ORIGINAL ARTICLE – ADULT CARDIAC
Interactive CardioVascular and Thoracic Surgery 21 (2015) 359–365 doi:10.1093/icvts/ivv160 Advance Access publication 20 June 2015
Cite this article as: Bentala M, Heuts S, Vos R, Maessen J, Scohy TV, Gerritse BM et al. Comparing the endo-aortic balloon and the external aortic clamp in minimally invasive mitral valve surgery. Interact CardioVasc Thorac Surg 2015;21:359–65.
Comparing the endo-aortic balloon and the external aortic clamp in minimally invasive mitral valve surgery
a b c d
Department of Cardiothoracic Surgery, Amphia Hospital, Breda, Netherlands Department of Cardiothoracic Surgery, Maastricht University Medical Centre, Maastricht, Netherlands Department of Methodology and Statistics, Maastricht University, Maastricht, Netherlands Department of Cardiothoracic Anaesthesia, Amphia Hospital, Breda, Netherlands
* Corresponding author. E-mail: [email protected] (M. Bentala). Received 9 March 2015; received in revised form 18 May 2015; accepted 28 May 2015
Abstract OBJECTIVES: The aim of this study was to assess the differences in perioperative outcomes and complications between the endo-aortic balloon (EAB) and the external aortic clamp (EAC) during primary elective minimally invasive mitral valve surgery (MIMVS) in a single referral centre by one surgeon. Primary outcomes were cardiopulmonary bypass time (CPB), cross-clamp time (CX) and occurrence of postoperative cerebrovascular accidents (CVAs). Secondary outcomes were other perioperative parameters and complications. METHODS: We retrospectively analysed 340 consecutive patients who underwent MIMVS for mitral regurgitation (MR), mitral stenosis or combined regurgitation/stenosis between November 2010 and March 2014 in a single referral centre. In total, 221 patients who underwent an isolated mitral valve repair or isolated mitral valve replacement or repair/replacement combined with an atrial fibrillation (AF)ablation procedure were included. Patients who had previous cardiac surgery or concomitant tricuspid valve surgery, myxoma or atrial septal defect closure surgery were excluded. RESULTS: A total of 57 patients (Group A) underwent MIMVS using the EAC and 164 patients (Group B) were operated using an EAB. Preoperative variables showed a significant difference in poor left ventricular function (LVF, P = 0.18) and moderate LVF (P = 0.019). No significant differences were found in CPB-time, cross-clamp time or postoperative CVA. Furthermore, no significant differences were found in complications, 30-day mortality or postoperative echocardiographical MR gradation. Hospital stay, however, was prolonged in Group A (P = 0.001) and maximum troponin T levels were significantly lower in Group B (P = 0.014). In Group B however, 10 procedures were converted (6%) from EAB to EAC. CONCLUSIONS: There is no difference in use between the EAB and the EAC in terms of CPB-time and cross-clamp time, complications or MR gradation at discharge. Use of the EAC showed significantly higher postoperative levels of troponin T, implying more myocardial damage, compared with the EAB. In 6% of the cases however, patients were converted from the EAB to the EAC. Keywords: Mitral valve • Minimally invasive surgery • External aortic clamp • Endo-aortic balloon
INTRODUCTION Minimally invasive mitral valve surgery (MIMVS) has been performed since the mid-1990s [1, 2] and for the past decade it has been widely accepted as a safe alternative for the median sternotomy approach. Studies of MIMVS describe reduced blood drainage volume, and the need for transfusions as well as reduced length of ICU stay, hospital stay and mechanical ventilation time. Cardiopulmonary bypass (CPB), cross-clamp time and procedure time are reported to be longer in the MIMVS [3, 4]. Although different techniques have been used, a right anterolateral minithoracotomy in the fourth intercostal space is the most preferred access route [4].
In order to set up CPB in MIMVS, patients require peripheral cannulation and clamping of the aorta. Clamping can be achieved in two different ways. The first method is the external aortic clamp (EAC), (Chitwood DeBakey-clamp, Scanlan International, Inc., St Paul, MN, USA) [5]. The EAC is introduced through a separate skin incision in the same or one intercostal space above the initial minithoracotomy in the anterior axillary line and can be positioned around the ascending aorta under direct view or videoscopic guidance. Cardioplegia and aortic-root venting are delivered through a needle-vent catheter in the aortic root. The second method is the endo-aortic balloon (EAB) (EndoClamp or its successor, IntraClude, Edwards Lifesciences, Irvine, CA, USA). The EAB is a triple lumen catheter with a balloon
© The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
ORIGINAL ARTICLE
Mohamed Bentalaa,*, Samuel Heutsb, Rein Vosc, Jos Maessenb, Thierry V. Scohyd, Bastiaan M. Gerritsed and Peyman Sardari Niab
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at the tip and a large central lumen for cardioplegia delivery and aortic-root venting. The other two lumina are for pressure monitoring in the aortic root and for inflation and deflation of the balloon. The balloon catheter is introduced via the common femoral artery through a special cannula (ThruPort EndoReturn, Edwards Lifesciences) and is inflated in the ascending aorta under transoesophageal echocardiography (TOE) guidance in order to achieve occlusion. The cardioplegia is then delivered antegradely through the central lumen of the balloon catheter in the aortic root. Previous studies, with relatively small groups, showed that EAC compared with EAB performs equally in terms of safety and the low risk of morbidity and mortality. These studies describe a longer procedure time, CPB time and cross-clamp (CX)-time when the EAB-technique is compared with EAC-technique [6–8]. The aim of this study is to assess the differences in perioperative outcomes and complications between the EAC and EAB in a single referral centre with a large group of patients. Primary outcomes are mortality, CPB-time, cross-clamp time and occurrence of postoperative cerebrovascular accidents (CVAs). Secondary outcomes are other perioperative parameters and complications.
MATERIALS AND METHODS Population We retrospectively analysed 340 consecutive patients who underwent elective MIMVS by a single surgeon in a single referral centre between November 2010 and March 2014. All the patients presented for isolated mitral valve (MV) repair or MV replacement were included. Patients who underwent repair or replacement in combination with a maze procedure, were included in the study as well. Patients with previous cardiac surgery (30), concomitant tricuspid surgery (46), myxoma excision (7) or atrial septal defect/patent open foramen ovale closure surgery (36) were excluded. Subsequently, 221 patients were included in the study.
Preoperative work-up Standard MIMVS work-up included a coronary angiography, chest X-ray and a consult with a maxillofacial surgeon. TEE was used to assess the thoracic aorta, the aortic valve and the severity and mechanism of mitral regurgitation (MR). MR was graded based on the recommendations of the European Association of Echocardiography (mild = 1, mild-moderate = 2, moderate = 3, severe = 4) [9]. A computer tomography angiography of the complete aorta and femoroiliac arteries was only performed if there were indications for vascular pathology. Patients with a history of right-sided lung surgery, thoracic deformity or severe peripheral artery disease were excluded for MIMVS. TEE was used intraoperatively for cannulation, for full cardiographic monitoring and for direct evaluation of the MV after weaning of extracorporeal circulation. Postoperative TEE was performed at discharge in all patients. Severity of dyspnoea was assessed based on the New York Heart Association Classification. Risk of mortality was described as and based on the additive European System for Cardiac Operative Risk Evaluation I [10]. Pulmonary hypertension was defined as a systolic pulmonary artery pressure above 60 mmHg. Mechanism
of MR was classified based on Carpentier’s functional classification for MR [11]. Poor left ventricular function (LVF) was defined as left ventricular ejection fraction (LVEF) 50%. Cardiac troponin levels were measured postoperatively at arrival at the ICU, 4 h later and the next day. If the cardiac troponin levels were high at any time, then the measurements were done more frequently. For this study, we used the maximum levels of cardiac troponin within hospital stay. Creatinine and haemoglobin levels were measured at discharge. Complications were registered when they occurred within 30 days of surgery or within the same hospitalization.
Surgical technique For anaesthesia, the same protocol was used in both cardiac surgery groups. After induction with propofol, midazolam, sufentanil and pancuronium, anaesthesia was maintained with sevoflurane and remifentanil. Arterial blood pressure monitoring was obtained by a 20 Gauge catheter in the right- and the left radial artery. Cerebral oximetry (INVOS, Covidien, Dublin, Ireland) was used to observe the cerebral saturation. An endobronchial blocker (EZ-blocker, Teleflex, Wayne, PA, USA) was used to allow one-lung ventilation. CPB was established by femoro-femoral cannulation in all patients using a 2 cm incision over the groin skin line with only ventral exposition of the femoral artery and vein. After femoral preparation, a guidewire was inserted in the femoral vein and advanced to the superior vena cava under TEE guidance. An endovenous drainage cannula was then inserted over this guidewire and advanced into the superior vena cava under the guidance of TEE. The venous cannula was a 25 mm two-staged cannula that allows a cardiac output up to 6 l/min. (RAP™ Femoral Venous Cannula 23/25, Sorin Group, Milan, Italy). When the EAB (EndoClamp, IntraClude. Edwards Lifesciences) was used, a special arterial cannula with a side arm was inserted in the common femoral artery (ThruPort EndoReturn, Edwards Lifesciences). Then a guidewire was introduced through the side arm of this arterial cannula and was advanced to the aortic root under TEE guidance. Finally, the EAB was advanced over the guidewire to the level of the ascending aorta proximal to the innominate artery. This was done before the initiation of the CPB, to prevent embolization from the descending aorta during the retrograde flow while manipulating with the guidewire or the EAB. After the insertion of the arterial and venous cannulas, a 4–5 cm minithoracotomy was made in the inframammary fold, usually in the fourth intercostal space. The procedure is then continued with one-lung ventilation (left). Visualization is accomplished by a 10 mm 0° endoscope that is placed in the anterior axillary line in the same intercostal space through a trocar. Carbondioxide is insufflated through a side arm of the trocar at a rate of 4 l/min. The operation was further performed using long shafted instruments. Mechanical rib spreading was avoided in the most cases of the EAB, however in the EAC group the rib spreader was used to gain a good direct view on the aorta. The view over the MV was, in both groups, totally endoscopic. The pericardium is opened 2 cm above the phrenic nerve. The dorsal pericardial edges are being pulled laterally with three sutures. In order to expose the left atrial roof, a suture is placed into the interatrial groove’s fat tissue and pulled towards the
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Statistical analysis Statistical analysis was performed using the SPSS statistical software package 21.0 for Windows (SPSS, Inc., Chicago, IL, USA). Normality of continuous variables was tested with the Shapiro– Wilk test. Continuous normal distributed data were analysed using the unpaired Student’s t-test, where values were expressed as mean ± standard deviation. Continuous non-normal distributed data were analysed using the Mann–Whitney U-test, where values were expressed as medians and ranges (R) and/or interquartile ranges (IQRs). Categorical data were tested with the χ2-test, or in
low expected quantities (≤5) with the Fisher’s exact test. These values were expressed as absolute numbers and percentages. In all cases, probability values (P) of less than 0.05 were considered significant. Both intraoperative clamping conversion and conversion to sternotomy were analysed using an intention-to-treat (ITT) analysis.
RESULTS Two-hundred and twenty-one patients were included in this study. Patients operated on between November 2010 and November 2011 (n = 54) were clamped with EAC. From November 2011 until March 2014, patients were aortic-clamped with the use of the EAB. EAC was used on 3 patients in this period because of a wide diameter of the ascending aorta (>4.0 cm). The first 38 patients within the EAB group, were clamped using the EndoClamp, the latter 126 patients in the EAB group were clamped using the EndoClamp’s successor; the IntraClude. Fifty-seven patients underwent MIMVS with the use of the EAC (Group A, 32 males, median age 62, IQR 57–63, R 28–84). Group B (n = 164) underwent surgery with the EAB clamping technique (92 males, median age; 66, IQR 60–74, R 37–87).
Baseline characteristics There was a significant difference in LVF. There were more patients with normal LVF in the EAB group (69 vs 46%, P = 0.002), whereas there were less patients with a moderate LVF in the EAB group (28 vs 46%, P = 0.019). Other baseline characteristics were similar between the two groups (Table 1).
Surgical procedure and perioperative outcomes There were no significant differences in surgical procedures between the two groups (Table 2). There were no significant differences in CPB- or X-time. Hospital stay, however, was significantly prolonged in Group A (P = 0.001). Furthermore, there was a significant difference in maximum postoperative cardiac troponin levels between the Groups A and B (P = 0.005). Because the first 27 patients of Group A received a different type of cardioplegia (without cooling), we compared these patients with the latter 30 patients of Group A. This showed no significant difference (median 0.578, IQR 0.314–0.852, R 0.210–8.650 vs median 0.704, IQR 0.435–1.088, R 0.161–3.640, P = 0.230). The latter group of 30 patients was then compared with Group B. This, still, showed significant lower levels of troponin T in Group B (median 0.704, IQR 0.435–1.088, R 0.161–3.640 vs median 0.449, IQR 0.281–0.780, R 0.117–6.190, P = 0.008). Other perioperative outcomes showed no differences (Table 3).
Complications No significant differences were found between the two groups in regard to complications (Table 4). In 2 cases (one case each in EAB and EAC), conversion to sternotomy intraoperatively was, respectively, due to excessive bleeding and high perfusion-pressure. These patients were taken into an ITT analysis.
ORIGINAL ARTICLE
anterior thoracic wall. The CPB was started and the cooling to a core temperature of 30°C was started; however, the initial 30 patients with EAC were operated on normothermia. The maximum arterial retrograde perfusion pressure that was accepted was 350 mmHg. If this pressure tended to be higher, the contralateral femoral artery was then cannulated for additional arterial perfusion. In case of use of the Chitwood clamp (Scanlan International, Inc.), the clamp was placed through a small incision in the anterior axillary line in the third or fourth intercostal space. In these cases, the pericardiotomy was cranially enlarged in order to have good exposition of the ascending aorta. An aortic-root needle was inserted in the aortic root for the purpose of cardioplegia delivery and aortic-root venting. The EAB was not used in patients with an ascending aorta diameter above 40 mm, according to the advice of the company that delivers this device. The chitwood clamp is then used. This is the only contraindication for the use of the EAB. An atrial retractor was placed through a small incision in the same intercostal space as the minithoracotomy, laterally from the right internal mammary artery.The aorta was clamped by means of either the direct transthoracic chitwood clamp, or through the inflation of the EAB under TEE guidance. Anterograde blood cardioplegia was administered through the aortic-root cannula in the EAC group, or through the central lumen of the EAB catheter. Blood cardioplegia solution, administered at 20-min intervals, was used for myocardial protection. In the EAB group, we made sure the cardioplegia pressure rose in the aortic root every time it was administered. The cardioplegia pressure in the aortic root must reach a pressure above 30 mmHg with a flow of cardioplegia at 250 ml/min. When the pressure in the aortic root during the cardioplegia delivery did not rise, the atrial-retractor or the EAB was repositioned in such manner that pressure elevation was restored. The left atrium was opened through an incision in the interatrial groove. In order to have optimal exposure of the MV, two sutures were placed in the anterior edge of the atriotomy. An atrial-retractor blade with a side arm (USB) was then positioned in order to have an optimal view over the entire MV annulus. Several different techniques for repair were used, depending on the mechanism of MR, chordal replacement was our preferred technique in case of chordal elongation or rupture (Table 2) [12]. At the end of the procedure, left ventricular de-airing was performed with a ventricular vent through the MV, and suction on the EAB lumen (in the EAB group) or the aortic-root needle (in the EAC group). The ventilation of the left lung was also started in this stadium for de-airing purpose. The left ventricular vent and the aortic needle were removed after establishing through TEE that there was no further air scattering within the left ventricle. The EAB was removed after weaning from CPB, during antegrade flow, for the same reason of risk of embolization from the descending aorta.
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Table 1: Baseline characteristics Parameter
Group A (EAC)
Group B (EAB)
P-value
Age (years) (median, IQR, range) Gender (male) BMI (kg/m2) (median, IQR, range) NYHA I II III EuroSCORE I (add) (median, IQR, range) Preoperative haemoglobin (mmol/l) (median, IQR, range) Preoperative creatinine (mmol/l) (median, IQR, range) LVF Normal (LVEF > 50%) Moderate (LVEF 30–50%) Poor (LVEF < 30%) COPD Peripheral artery disease CVA TIA Diabetes mellitus Hypertension Hypercholesterolaemia Pulmonary hypertension Atrial fibrillation Mitral stenosis Combined MR/MS Mitral regurgitation Grades 3 and 4 Carpentier I Carpentier II Carpentier IIIa Carpentier IIIb Barlow’s disease Endocarditis
62 (57–73) (28–84) 32 (56%) 25.1 (23.4–28.0) (19.2–39.5) – 7 (12%) 20 (35%) 31 (54%) 3 (2–6) (0–9) 8.8 (7.7–9.2) (6.4–10.4) 85 (72–96) (46–714) – 25 (46%) 25 (46%) 5 (9%) 6 (11%) 1 (2%) 4 (7%) 7 (12%) 6 (11%) 25 (44%) 8 (14%) 19 (33%) 25 (44%) 4 (7%) 3 (5%) 50 (88%) 48 (96%) 17 (34%) 30 (60%) 1 (2%) 2 (4%) 4 (8%) 1 (2%)
66 (60–74) (37–87) 92 (56%) 25 (22.4–27.4) (17.1–40.5) – 22 (13%) 57 (35%) 85 (52%) 2 (2–5) (0–10) 8.7 (8.0–9.2) (5.3–10.3) 83 (72–98) (47–312) – 112 (69%) 45 (28%) 7 (4%) 12 (7%) 2 (1%) 3 (2%) 9 (6%) 8 (5%) 67 (41%) 32 (20%) 38 (24%) 62 (38%) 5 (3%) 5 (3%) 154 (94%) 154 (100%) 37 (24%) 108 (70%) 2 (1%) 7 (4%) 19 (12%) 4 (3%)
0.078 0.10 0.34 – 0.83 0.96 0.74 0.56 0.99 0.93 – 0.002 0.019 0.18 0.45 1.00 0.075 0.13 0.20 0.69 0.36 0.14 0.44 0.24 0.43 0.15 0.059 0.17 0.18 0.57 1.00 0.61 1.00
IQR: interquartile range; BMI: body mass index; NYHA: New York Heart Association classification of dyspnoea; EuroSCORE: additive European System for Cardiac Operative Risk Evaluation; LVF: left ventricular function; COPD: chronic obstructive pulmonary disease; CVA: cerebrovascular accident; TIA: transient ischaemic attack; MR: mitral regurgitation; MS: mitral stenosis; EAC: external aortic clamp; EAB: endo-aortic balloon; LVEF: left ventricular ejection fraction.
group (1%); there were no mortalities in the EAC group (P = 1.000). Finally, there was no significant difference between Group A and Group B with respect to TEE MR gradation at discharge (Table 6).
Table 2: Surgical procedure Group B (EAB)
P-value
Parameters
Group A (EAC)
Concomitant maze procedure Replacement Repair Chordal replacement Resection Ring-use Size 26 Size 28 Size 30 Size 32 Size 34 Size 36
21 (37%)
56 (34%)
0.71
9 (16%) 48 (84%) 28 (58%) 2 (4%) 48 (100%) 1 (2%) 13 (27%) 18 (38%) 9 (19%) 6 (13%) 1 (2%)
15 (9%) 149 (91%) 98 (66%) 2 (1%) 146 (98%) 1 (1%) 27 (19%) 47 (32%) 23 (16%) 40 (27%) 8 (5%)
0.17 0.17 0.35 0.25 1.00 0.44 0.20 0.50 0.63 0.035 0.46
Maze: ablation surgery for atrial fibrillation; EAC: external aortic clamp; EAB: endo-aortic balloon.
In Group B, 10 patients (6%) required conversion from EAB to EAC for different reasons (Table 5); they were taken in to ITT analysis as well. Two patients died within 30 days of surgery in the EAB
DISCUSSION Our study compared the EAC and EAB in 221 patients undergoing MIMVS. Our primary outcomes were CPB-time, X-time and occurrence of postoperative CVA. We did not find significant differences between the two techniques regarding these outcomes. Baseline characteristics showed few differences in LVF between the two groups. The distribution was not equal in the group of normal LVF and moderate LVF. More patients in group EAB had normal LVF compared with group EAC, whereas less patients had moderate LVF compared with Group A. No differences in CPB- and X-time were found. Comparable studies show that CPB- and X-time are usually prolonged in the EAB groups [6, 13, 14]. Mazine et al. [6] reported that their results should be interpreted in the context of the initial experiences with the minimally invasive approach where the EAB was used and thus at the beginning of their experiences with this approach. Reichenspurner et al. [13] reported significantly longer crossclamping time and equal CPB time in a comparable study with 60
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Table 3: Perioperative data Parameters
Group A (EAC)
Group B (EAB)
P-value
CPB-time (min) (median, IQR, range) Cross-clamp time (min) (median, IQR, range) ICU stay (days) (median, IQR, range) Hospital stay (days) (median, IQR, range) Conversion to replacement Postoperative haemoglobin (mmol/l) (mean, SD) Postoperative creatinine (mmol/l) (median, IQR, range) Postoperative maximum Troponin T level (μg/l) (median, IQR, range)
135 (118–159) (79–197) 85 (66–100) (48–145) 1 (1–1) (0–5) 7 (7–10) (6–37) 0 7.3 ± 0.9SD 72 (61–85) (48–345) 0.667 (0.350–0.975) (0.161–8.650)
130 (113–149) (81–325) 77 (63–95) (39–237) 1 (1–1) (0–6) 6 (6–8) (4–44) 1 (1%) 7.2 ± 1.0SD 73 (64–87) (44–227) 0.449 (0.280–0.782) (0.117–6.190)
0.21 0.088 0.54 0.001 1.00 0.51 0.55 0.014
Table 4: Complications
Table 6:
Parameters
Group A (EAC)
Group B (EAB)
P-value
Conversion to sternotomy Groin lymphocele Aortal dissection DVT/PE Deep wound infection Pneumonia New onset AF Myocardial infarction Tamponade Rethoracotomy IABP dependence CVA Urinary tract infection Acute renal failure CVVH dependence
1 (2%) 0 0 0 0 3 (5%) 3 (5%) 2 (4%) 0 2 (4%) 0 0 0 1 (2%) 1 (2%)
1 (1%) 0 0 0 0 6 (4%) 23 (14%) 0 1 (1%) 5 (3%) 2 (1%) 3 (2%) 1 (1%) 4 (2%) 1 (1%)
0.45 – – – – 0.70 0.077 0.066 1.00 1.00 1.00 0.57 1.00 1.00 0.45
DVT: deep venous thrombosis; PE: pulmonary embolism; AF: atrial fibrillation; IABP: intra-aortal balloon pressure; CVA: cerebrovascular accident; CVVH: central veno venous haemodialysis; EAC: external aortic clamp; EAB: endo-aortic balloon.
Table 5: EAC
Reasons for intraoperative conversion of EAB to
Reason of conversion to EAB Unable to advance guidewire in Ascending aorta Abdominal aorta Unable to advance balloon in Femoral arteries Abdominal aorta Calcified descending aorta on TEE Iatrogenic balloon puncture High perfusion pressure Loss of balloon pressure
Number of cases
1 1 1 3 1 1 1 1
EAC: external aortic clamp; EAB: endo-aortic balloon; TEE: transoesophageal echocardiography.
patients in each group. They also reported that the learning curve could have played a role in the differences found. Ius et al. reported shorter CPB and X-time in the EAC. Furthermore, they reported
Mortality and MR gradation at discharge
Parameters
Group A (EAC)
Group B (EAB)
P-value
Thirty-day mortality MR gradation on discharge MR 0–1 MR 2 MR 3 MR 4
0 –
2 (1%) –
1.00 –
49 (98%) 1 (2%) 0 0
147 (99%) 0 1 (1%) 0
0.44 0.25 1.00 –
MR: mitral regurgitation; EAC: external aortic clamp; EAB: endo-aortic balloon.
their initial experiences with the minimally invasive approach in the EAB group [14]. In our series of 164 EAB patients, we were beyond the learning curve for the MIMVS approach. We started our experiences with this approach using the EAC. The cohort of 164 EAB-group contains also a sub-group, (n = 126) in which the latest EAB (the Intraclude) was used. The Intraclude is easier to position in the ascending aorta and it tends to migrate less during the procedure. These two reasons can potentially explain our findings of the equal CPB-time and X-time in these two groups. Loforte et al. [7] also found the same CPB-time and X-time in their comparison study between EAB and EAC in MIMVS approach. Krapf et al. [8] reported shorter CPB- and X-times in the EAB group in their comparison study in two large groups. However, these groups contained not only MV surgery patients but also endoscopic bypass surgery and other procedures. Occurrence of postoperative CVA, did not differ significantly between the EAC and EAB groups (0 vs 3, P = 0.57). Of these 3 patients with CVA, CVA occurred direct postoperatively in 2 patients, in 1 patient after 3 days. One patient recovered fully without any permanent damage. The total permanent stroke rate of the EAB group is 1.2% and for the whole cohort of 221 patients permanent stroke rate is 0.5%. Our findings are consistent with the comparison of EAC and EAB by other studies [6–8, 13, 14] in which no significant differences were found between these two groups either. Two studies reported a higher occurrence of microembolic events, registered by Trans Cranial Doppler ultrasound in the EAC group [7, 15]. However, these findings had no clinical consequences. The permanent stroke rate in our cohort is lower (0.5%) than that reported (1.7%) in literature [4]. We believe that our strategy
ORIGINAL ARTICLE
CPB: cardiopulmonary bypass; IQR: interquartile range; NS: not significant; ICU: intensive care unit; R: range; SD: standard deviation; EAC: external aortic clamp; EAB: endo-aortic balloon.
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of cooling to 30°C, the use of cerebral oximetry to detect cerebral ischaemia and the strict manipulation of the guidewire and the EAB ‘only’ during antegrade flow, are important factors that contribute to this low rate of permanent stroke. We did find a significant difference in hospital stay (median stay of 7 vs 6 days, P = 0.001) in favour of the EAB group. Other studies showed no difference in the duration of hospitalization in both the groups [7, 13], whereas Ius et al. even reported longer hospital stay in the EAB group. The explanation for the shorter hospital stay in our EAB group could be the use of the rib retractor in the EAC group. The patients in the EAC group had more pain that delayed early mobilization compared with those in the EAB group. Another reason is the change of postoperative treatment protocol of these patients in the nursing ward. After the first 100 consecutive patients, the protocol was changed to early mobilization and activation of these patients. These two reasons could explain the difference in the length of hospital stay between these two groups. We found a significant difference in postoperative maximum cardiac troponin levels, these were higher in the EAC group compared with the EAB group (P = 0.014). The first 27 patients in EAC group were treated with anterograde blood cardioplegia without cooling. From then on, all patients (30 patients in Group A and entire Group B) received anterograde blood cardioplegia in combination with cooling (to 30°C body temperature). Thereby, patients in the EAB group received anterograde cardioplegia after administration of adenosine through the lumen of the EAB. When we compared the first 27 patients (without cooling) of the EAC group with the latter 30 of the EAC group (with cooling), we found no significant difference in postoperative levels of cardiac troponin (P = 0.23). When we compared this second group of 30 patients in the EAC group, receiving cardioplegia with cooling, with the entire EAC group, receiving cardioplegia with cooling as well, we still found a significant difference in cardiac troponin levels, implying more myocardial damage in the EAC group (P = 0.008). This can potentially be explained by the prior administration of adenosine in the EAB group. Two studies proved that adenosine increases the potency of cardioplegia when administered in advance of the cardioplegia. This is possibly due to the inhibitory effects of adenosine on inflammatory-related processes in ischaemia [16, 17]. The difference cannot be explained either by a difference in the rate of concomitant atrial fibrillation (AF)-ablation surgery between the two groups (P = 0.71), which would be likely to induce more myocardial damage [18]. Other studies show no differences in myocardial damage [7] or more myocardial damage in the EAB group [14]. These studies, however, did not use blood cardioplegia, but crystalloid cardioplegia instead, and did not report the use of adenosine prior to cardioplegia administration, which therefore are difficult to compare with our results. Besides the use of the adenosine, we have a strict protocol for the use of antegrade blood cardioplegia when the EAB is used. As described above, the cardioplegia pressure in the aortic root must be above 30 mmHg, and the flow of cardioplegia must be at least 250 ml/min. The other studies did not report any strategy for observation of the antegrade cardioplegia delivery in the EAB group, only the strategy for retrograde cardioplegia was reported [6]. We believe that measuring the pressure rise above 30 mmHg in the aortic root and the amount of cardioplegia delivered to the aortic root is vital. Two causes can hinder the rise of pressure in the aortic root when EAB is used: the first cause is the deformation of the aortic annulus by the atrial-retractor blade (release of tension on the atrial-retractor blade will solve this problem) and the
second cause is malpositioning of the EAB with obstruction of the cardioplegia lumen by the aortic wall, thus diminishing the cardioplegia flow. Repositioning of the EAB will solve this problem. Ten patients (6%) in the EAB group were converted from EAB to EAC for several reasons (Table 5). In 7 patients, the conversion was due to the inability to advance the guidewire or the balloon in the ascending aorta. One patient was too tall (201 cm) for positioning of the EAB in the ascending aorta, the other 6 patients had femoral or aortic disease blocking the passage of the device. In 2 patients, conversion of EAB to EAC was due to puncture of the balloon and in one patient it was due to high pressures (above 350 mmHg) in the arterial cannula, without the possibility for contralateral cannulation. We did not find any significant differences in complications and clinical outcomes. This is consistent with other studies. Reichenspurner et al. [13], however, reported more re-explorations for bleeding and more complications in the EAB group, which is surprising because in the EAB group the ascending aorta is not punctured. Ius et al. [14] reported more cases of postoperatively prolonged ventilation (>72 h) in the EAB group. In our total cohort of 340 MIMVS procedures, neither aortic dissections nor femoral dissections were seen. We think this is because we do not accept arterial perfusion pressures above 350 mmHg and because we only dissect the anterior surface of the groin vessels and cannulate in the common femoral artery. The absence of any groin lymphocele postoperatively could also be due to this surgical technique.
Limitations There are two important limitations to our study. Firstly, data were collected retrospectively and therefore potentially biased. Secondly, the majority of the EAC group was operated prior to the EAB group and results can potentially be distorted by a learning curve. The fact that all patients were operated on by the same surgeon in our study, is a strength compared with other studies, which involved several surgeons. The learning curve of experience and the poorer LV function could be considered as a confounding factor in comparing the EAC and EAB group. Longer hospital stay with EAC and higher troponin levels may be influenced by the early experience; however, all surgery was performed by the same thoracic surgeon, who has extensive experience in mitral repair. A poorer LV function is generally not associated with a higher troponin level postoperatively in cardiac surgery, and there is no statistically significant difference in the rate of myocardial infarction between the two groups. Finally, our sample sizes were not equal. The EAC group consisted of 58 patients, whereas the EAB group consisted of 193 patients. This difference could potentially have influenced the significance between variables.
CONCLUSION MIMVS has become a standard approach for elective primary MV operations in our institution, and different techniques have been used to achieve aortic occlusion. These techniques were compared in our study. There were no differences in occurrence of CVA between the two clamping techniques. There were, however, significantly higher levels of postoperative measured cardiac troponin levels in the EAC group, implying more myocardial
damage. This could be caused by the addition of adenosine prior to cardioplegia delivery and monitoring of the cardioplegia pressures in the EAB, or because of the significant difference in LV function between both groups. Shorter hospital stay was found in the EAB group. Conversion from EAB to EAC was considered an important complication; it occurred in 6% of the EAB cases. In conclusion, there are no differences in use of the EAC and EAB regarding to CPB- and clamping-time, complications or clinical outcomes in our study. We do recommend that a randomized controlled trial be conducted in a referral centre where surgeons have completed their learning curve. Although this study has its limitations, a significant difference in postoperative troponine levels is found. The role of adenosine as myocardial protective agent should be further investigated.
[14]
[15]
[16]
[17]
[18]
Conflict of interest: Mohamed Bentala has a Consultancy agreement with Edwards life sciences.
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comparison of the port-access and transthoracic clamp techniques. Ann Thorac Surg 2005;79:485–91. Ius F, Mazzaro E, Tursi V, Guzzi G, Spagna E, Vetrugno L et al. Clinical results of minimally invasive mitral valve surgery: endoaortic clamp versus external aortic clamp techniques. Innovations 2009;4:311–8. Maselli D, Piziob R, Borellia G, Musumecib F. Endovascular balloon versus transthoracic aortic clamping for minimally invasive mitral valve surgery: impact on cerebral microemboli. Interact CardioVasc Thorac Surg 2006;5: 183–6. Katayama O, Ledingham SJ, Amrani M, Smolenski RT, Lachno DR, Jayakumar J et al. Functional and metabolic effects of adenosine in cardioplegia: role of temperature and concentration. Ann Thorac Surg 1997;63: 449–54; discussion 454–445. Vinten-Johansen J, Zhao ZQ, Corvera JS, Morris CD, Budde JM, Thourani VH et al. Adenosine in myocardial protection in on-pump and off-pump cardiac surgery. Ann Thorac Surg 2003;75:S691–699. Katritsis D, Hossein-Nia M, Anastasakis A, Poloniecki I, Holt DW, Camm AJ et al. Use of troponin-t concentration and kinase isoforms for quantitation of myocardial injury induced by radiofrequency catheter ablation. Eur Heart J 1997;18:1007–13.
eComment. New onset atrial fibrillation induced by adenosine
REFERENCES [1] Navia JL, Cosgrove DM III. Minimally invasive mitral valve operations. Ann Thorac Surg 1996;62:1542–4. [2] Lin PJ, Chang CH, Chu JJ, Liu HP, Tsai FC, Chu PH et al. Video-assisted mitral valve operations. Ann Thorac Surg 1996;61:1781–6; discussion 1786–1787. [3] Modi P, Hassan A, Chitwood WR Jr. Minimally invasive mitral valve surgery: a systematic review and meta-analysis. Eur J Cardiothorac Surg 2008;34:943–52. [4] Sundermann SH, Sromicki J, Rodriguez Cetina Biefer H, Seifert B, Holubec T, Falk V et al. Mitral valve surgery: right lateral minithoracotomy or sternotomy? A systematic review and meta-analysis. J Thorac Cardiovasc Surg 2014;148:1989–95. [5] Chitwood WR Jr, Elbeery JR, Moran JF. Minimally invasive mitral valve repair using transthoracic aortic occlusion. Ann Thorac Surg 1997;63: 1477–9. [6] Mazine A, Pellerin M, Lebon JS, Dionne PO, Jeanmart H, Bouchard D. Minimally invasive mitral valve surgery: influence of aortic clamping technique on early outcomes. Ann Thorac Surg 2013;96:2116–22. [7] Loforte A, Luzi G, Montalto A, Ranocchi F, Polizzi V, Sbaraglia F et al. Video-assisted minimally invasive mitral valve surgery: external aortic clamp versus endoclamp techniques. Innovations 2010;5:413–8. [8] Krapf C, Wohlrab P, Haussinger S, Schachner T, Hangler H, Grimm M et al. Remote access perfusion for minimally invasive cardiac surgery: to clamp or to inflate? Eur J Cardiothorac Surg 2013;44:898–904. [9] Lancellotti P, Moura L, Pierard LA, Agricola E, Popescu BA, Tribouilloy C et al. European association of echocardiography recommendations for the assessment of valvular regurgitation. Part 2: mitral and tricuspid regurgitation (native valve disease). Eur J Echocardiogr 2010;11:307–32. [10] Nashef SA, Roques F, Michel P, Gauducheau E, Lemeshow S, Salamon R. European system for cardiac operative risk evaluation (EuroSCORE). Eur J Cardiothorac Surg 1999;16:9–13. [11] Fedak PW, McCarthy PM, Bonow RO. Evolving concepts and technologies in mitral valve repair. Circulation 2008;117:963–74. [12] Holubec T, Sundermann SH, Jacobs S, Falk V. Chordae replacement versus leaflet resection in minimally invasive mitral valve repair. Ann Thorac Surg 2013;2:809–13. [13] Reichenspurner H, Detter C, Deuse T, Boehm DH, Treede H, Reichart B. Video and robotic-assisted minimally invasive mitral valve surgery: a
Authors: Omer Uz1, Veysel Temizkan2 and Zafer Isilak2 Deparment of Cardiovascular Surgery, GATA Haydarpasa Training Hospital, Istanbul, Turkey 2 Deparment of Cardiology, GATA Haydarpasa Training Hospital, Istanbul, Turkey doi: 10.1093/icvts/ivv216 © The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. 1
We read with interest the article of Bentala et al [1]. The authors evaluated the differences in perioperative outcomes and complications between the endo-aortic balloon and the external aortic clamp during primary elective minimally invasive mitral valve surgery in a single referral centre by one surgeon. They reported that there was no difference in use between the endo-aortic balloon and the external aortic clamp in terms of cardiopulmonary bypass-time and cross-clamp time, complications or mitral regurgitation gradation at discharge. We appreciate the authors’ efforts on conducting this valuable study. Nevertheless, we would like to share our opinions about some of the results of the study. As it is known, adenosine has also been shown to have powerful sympathomimetic effects through chemoreceptor activation, especially when administered as a bolus. Sympathetic activation has been demonstrated to be an important part of autonomically-triggered pulmonary veins’ (PVs) firing in isolated canine preparations and intact dogs. Adenosine can also induce ectopy in electrically silent PVs that may lead to development of new onset atrial fibrillation [2]. It was reported that the number of new onset AF was found to be higher (though not statistically significant) in the endo-aortic balloon group when compared to that of external aortic clamp. We think that adenosine administered before cardioplegia in the endo-aortic balloon group might be the cause of new onset AF originating from pulmonary veins. Conflict of interest: none declared. References [1] Bentala M, Heuts S, Vos R, Maessen J, Scohy TV, Gerritse BM et al. Comparing the endo-aortic balloon and the external aortic clamp in minimally invasive mitral valve surgery. Interact CardioVasc Thorac Surg 2015;21:359–65. [2] Cheung JW, Ip JE, Chung JH, Markowitz SM, Liu CF, Thomas G et al. Differential effects of adenosine on pulmonary vein ectopy after pulmonary vein isolation: implications for arrhythmogenesis. Circ Arrhythm Electrophysiol 2012;1:659– 66.
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M. Bentala et al. / Interactive CardioVascular and Thoracic Surgery
Interactive CardioVascular and Thoracic Surgery 21 (2015) 359–365 doi:10.1093/icvts/ivv160 Advance Access publication 20 June 2015
Cite this article as: Bentala M, Heuts S, Vos R, Maessen J, Scohy TV, Gerritse BM et al. Comparing the endo-aortic balloon and the external aortic clamp in minimally invasive mitral valve surgery. Interact CardioVasc Thorac Surg 2015;21:359–65.
Comparing the endo-aortic balloon and the external aortic clamp in minimally invasive mitral valve surgery
a b c d
Department of Cardiothoracic Surgery, Amphia Hospital, Breda, Netherlands Department of Cardiothoracic Surgery, Maastricht University Medical Centre, Maastricht, Netherlands Department of Methodology and Statistics, Maastricht University, Maastricht, Netherlands Department of Cardiothoracic Anaesthesia, Amphia Hospital, Breda, Netherlands
* Corresponding author. E-mail: [email protected] (M. Bentala). Received 9 March 2015; received in revised form 18 May 2015; accepted 28 May 2015
Abstract OBJECTIVES: The aim of this study was to assess the differences in perioperative outcomes and complications between the endo-aortic balloon (EAB) and the external aortic clamp (EAC) during primary elective minimally invasive mitral valve surgery (MIMVS) in a single referral centre by one surgeon. Primary outcomes were cardiopulmonary bypass time (CPB), cross-clamp time (CX) and occurrence of postoperative cerebrovascular accidents (CVAs). Secondary outcomes were other perioperative parameters and complications. METHODS: We retrospectively analysed 340 consecutive patients who underwent MIMVS for mitral regurgitation (MR), mitral stenosis or combined regurgitation/stenosis between November 2010 and March 2014 in a single referral centre. In total, 221 patients who underwent an isolated mitral valve repair or isolated mitral valve replacement or repair/replacement combined with an atrial fibrillation (AF)ablation procedure were included. Patients who had previous cardiac surgery or concomitant tricuspid valve surgery, myxoma or atrial septal defect closure surgery were excluded. RESULTS: A total of 57 patients (Group A) underwent MIMVS using the EAC and 164 patients (Group B) were operated using an EAB. Preoperative variables showed a significant difference in poor left ventricular function (LVF, P = 0.18) and moderate LVF (P = 0.019). No significant differences were found in CPB-time, cross-clamp time or postoperative CVA. Furthermore, no significant differences were found in complications, 30-day mortality or postoperative echocardiographical MR gradation. Hospital stay, however, was prolonged in Group A (P = 0.001) and maximum troponin T levels were significantly lower in Group B (P = 0.014). In Group B however, 10 procedures were converted (6%) from EAB to EAC. CONCLUSIONS: There is no difference in use between the EAB and the EAC in terms of CPB-time and cross-clamp time, complications or MR gradation at discharge. Use of the EAC showed significantly higher postoperative levels of troponin T, implying more myocardial damage, compared with the EAB. In 6% of the cases however, patients were converted from the EAB to the EAC. Keywords: Mitral valve • Minimally invasive surgery • External aortic clamp • Endo-aortic balloon
INTRODUCTION Minimally invasive mitral valve surgery (MIMVS) has been performed since the mid-1990s [1, 2] and for the past decade it has been widely accepted as a safe alternative for the median sternotomy approach. Studies of MIMVS describe reduced blood drainage volume, and the need for transfusions as well as reduced length of ICU stay, hospital stay and mechanical ventilation time. Cardiopulmonary bypass (CPB), cross-clamp time and procedure time are reported to be longer in the MIMVS [3, 4]. Although different techniques have been used, a right anterolateral minithoracotomy in the fourth intercostal space is the most preferred access route [4].
In order to set up CPB in MIMVS, patients require peripheral cannulation and clamping of the aorta. Clamping can be achieved in two different ways. The first method is the external aortic clamp (EAC), (Chitwood DeBakey-clamp, Scanlan International, Inc., St Paul, MN, USA) [5]. The EAC is introduced through a separate skin incision in the same or one intercostal space above the initial minithoracotomy in the anterior axillary line and can be positioned around the ascending aorta under direct view or videoscopic guidance. Cardioplegia and aortic-root venting are delivered through a needle-vent catheter in the aortic root. The second method is the endo-aortic balloon (EAB) (EndoClamp or its successor, IntraClude, Edwards Lifesciences, Irvine, CA, USA). The EAB is a triple lumen catheter with a balloon
© The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.
ORIGINAL ARTICLE
Mohamed Bentalaa,*, Samuel Heutsb, Rein Vosc, Jos Maessenb, Thierry V. Scohyd, Bastiaan M. Gerritsed and Peyman Sardari Niab
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at the tip and a large central lumen for cardioplegia delivery and aortic-root venting. The other two lumina are for pressure monitoring in the aortic root and for inflation and deflation of the balloon. The balloon catheter is introduced via the common femoral artery through a special cannula (ThruPort EndoReturn, Edwards Lifesciences) and is inflated in the ascending aorta under transoesophageal echocardiography (TOE) guidance in order to achieve occlusion. The cardioplegia is then delivered antegradely through the central lumen of the balloon catheter in the aortic root. Previous studies, with relatively small groups, showed that EAC compared with EAB performs equally in terms of safety and the low risk of morbidity and mortality. These studies describe a longer procedure time, CPB time and cross-clamp (CX)-time when the EAB-technique is compared with EAC-technique [6–8]. The aim of this study is to assess the differences in perioperative outcomes and complications between the EAC and EAB in a single referral centre with a large group of patients. Primary outcomes are mortality, CPB-time, cross-clamp time and occurrence of postoperative cerebrovascular accidents (CVAs). Secondary outcomes are other perioperative parameters and complications.
MATERIALS AND METHODS Population We retrospectively analysed 340 consecutive patients who underwent elective MIMVS by a single surgeon in a single referral centre between November 2010 and March 2014. All the patients presented for isolated mitral valve (MV) repair or MV replacement were included. Patients who underwent repair or replacement in combination with a maze procedure, were included in the study as well. Patients with previous cardiac surgery (30), concomitant tricuspid surgery (46), myxoma excision (7) or atrial septal defect/patent open foramen ovale closure surgery (36) were excluded. Subsequently, 221 patients were included in the study.
Preoperative work-up Standard MIMVS work-up included a coronary angiography, chest X-ray and a consult with a maxillofacial surgeon. TEE was used to assess the thoracic aorta, the aortic valve and the severity and mechanism of mitral regurgitation (MR). MR was graded based on the recommendations of the European Association of Echocardiography (mild = 1, mild-moderate = 2, moderate = 3, severe = 4) [9]. A computer tomography angiography of the complete aorta and femoroiliac arteries was only performed if there were indications for vascular pathology. Patients with a history of right-sided lung surgery, thoracic deformity or severe peripheral artery disease were excluded for MIMVS. TEE was used intraoperatively for cannulation, for full cardiographic monitoring and for direct evaluation of the MV after weaning of extracorporeal circulation. Postoperative TEE was performed at discharge in all patients. Severity of dyspnoea was assessed based on the New York Heart Association Classification. Risk of mortality was described as and based on the additive European System for Cardiac Operative Risk Evaluation I [10]. Pulmonary hypertension was defined as a systolic pulmonary artery pressure above 60 mmHg. Mechanism
of MR was classified based on Carpentier’s functional classification for MR [11]. Poor left ventricular function (LVF) was defined as left ventricular ejection fraction (LVEF) 50%. Cardiac troponin levels were measured postoperatively at arrival at the ICU, 4 h later and the next day. If the cardiac troponin levels were high at any time, then the measurements were done more frequently. For this study, we used the maximum levels of cardiac troponin within hospital stay. Creatinine and haemoglobin levels were measured at discharge. Complications were registered when they occurred within 30 days of surgery or within the same hospitalization.
Surgical technique For anaesthesia, the same protocol was used in both cardiac surgery groups. After induction with propofol, midazolam, sufentanil and pancuronium, anaesthesia was maintained with sevoflurane and remifentanil. Arterial blood pressure monitoring was obtained by a 20 Gauge catheter in the right- and the left radial artery. Cerebral oximetry (INVOS, Covidien, Dublin, Ireland) was used to observe the cerebral saturation. An endobronchial blocker (EZ-blocker, Teleflex, Wayne, PA, USA) was used to allow one-lung ventilation. CPB was established by femoro-femoral cannulation in all patients using a 2 cm incision over the groin skin line with only ventral exposition of the femoral artery and vein. After femoral preparation, a guidewire was inserted in the femoral vein and advanced to the superior vena cava under TEE guidance. An endovenous drainage cannula was then inserted over this guidewire and advanced into the superior vena cava under the guidance of TEE. The venous cannula was a 25 mm two-staged cannula that allows a cardiac output up to 6 l/min. (RAP™ Femoral Venous Cannula 23/25, Sorin Group, Milan, Italy). When the EAB (EndoClamp, IntraClude. Edwards Lifesciences) was used, a special arterial cannula with a side arm was inserted in the common femoral artery (ThruPort EndoReturn, Edwards Lifesciences). Then a guidewire was introduced through the side arm of this arterial cannula and was advanced to the aortic root under TEE guidance. Finally, the EAB was advanced over the guidewire to the level of the ascending aorta proximal to the innominate artery. This was done before the initiation of the CPB, to prevent embolization from the descending aorta during the retrograde flow while manipulating with the guidewire or the EAB. After the insertion of the arterial and venous cannulas, a 4–5 cm minithoracotomy was made in the inframammary fold, usually in the fourth intercostal space. The procedure is then continued with one-lung ventilation (left). Visualization is accomplished by a 10 mm 0° endoscope that is placed in the anterior axillary line in the same intercostal space through a trocar. Carbondioxide is insufflated through a side arm of the trocar at a rate of 4 l/min. The operation was further performed using long shafted instruments. Mechanical rib spreading was avoided in the most cases of the EAB, however in the EAC group the rib spreader was used to gain a good direct view on the aorta. The view over the MV was, in both groups, totally endoscopic. The pericardium is opened 2 cm above the phrenic nerve. The dorsal pericardial edges are being pulled laterally with three sutures. In order to expose the left atrial roof, a suture is placed into the interatrial groove’s fat tissue and pulled towards the
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Statistical analysis Statistical analysis was performed using the SPSS statistical software package 21.0 for Windows (SPSS, Inc., Chicago, IL, USA). Normality of continuous variables was tested with the Shapiro– Wilk test. Continuous normal distributed data were analysed using the unpaired Student’s t-test, where values were expressed as mean ± standard deviation. Continuous non-normal distributed data were analysed using the Mann–Whitney U-test, where values were expressed as medians and ranges (R) and/or interquartile ranges (IQRs). Categorical data were tested with the χ2-test, or in
low expected quantities (≤5) with the Fisher’s exact test. These values were expressed as absolute numbers and percentages. In all cases, probability values (P) of less than 0.05 were considered significant. Both intraoperative clamping conversion and conversion to sternotomy were analysed using an intention-to-treat (ITT) analysis.
RESULTS Two-hundred and twenty-one patients were included in this study. Patients operated on between November 2010 and November 2011 (n = 54) were clamped with EAC. From November 2011 until March 2014, patients were aortic-clamped with the use of the EAB. EAC was used on 3 patients in this period because of a wide diameter of the ascending aorta (>4.0 cm). The first 38 patients within the EAB group, were clamped using the EndoClamp, the latter 126 patients in the EAB group were clamped using the EndoClamp’s successor; the IntraClude. Fifty-seven patients underwent MIMVS with the use of the EAC (Group A, 32 males, median age 62, IQR 57–63, R 28–84). Group B (n = 164) underwent surgery with the EAB clamping technique (92 males, median age; 66, IQR 60–74, R 37–87).
Baseline characteristics There was a significant difference in LVF. There were more patients with normal LVF in the EAB group (69 vs 46%, P = 0.002), whereas there were less patients with a moderate LVF in the EAB group (28 vs 46%, P = 0.019). Other baseline characteristics were similar between the two groups (Table 1).
Surgical procedure and perioperative outcomes There were no significant differences in surgical procedures between the two groups (Table 2). There were no significant differences in CPB- or X-time. Hospital stay, however, was significantly prolonged in Group A (P = 0.001). Furthermore, there was a significant difference in maximum postoperative cardiac troponin levels between the Groups A and B (P = 0.005). Because the first 27 patients of Group A received a different type of cardioplegia (without cooling), we compared these patients with the latter 30 patients of Group A. This showed no significant difference (median 0.578, IQR 0.314–0.852, R 0.210–8.650 vs median 0.704, IQR 0.435–1.088, R 0.161–3.640, P = 0.230). The latter group of 30 patients was then compared with Group B. This, still, showed significant lower levels of troponin T in Group B (median 0.704, IQR 0.435–1.088, R 0.161–3.640 vs median 0.449, IQR 0.281–0.780, R 0.117–6.190, P = 0.008). Other perioperative outcomes showed no differences (Table 3).
Complications No significant differences were found between the two groups in regard to complications (Table 4). In 2 cases (one case each in EAB and EAC), conversion to sternotomy intraoperatively was, respectively, due to excessive bleeding and high perfusion-pressure. These patients were taken into an ITT analysis.
ORIGINAL ARTICLE
anterior thoracic wall. The CPB was started and the cooling to a core temperature of 30°C was started; however, the initial 30 patients with EAC were operated on normothermia. The maximum arterial retrograde perfusion pressure that was accepted was 350 mmHg. If this pressure tended to be higher, the contralateral femoral artery was then cannulated for additional arterial perfusion. In case of use of the Chitwood clamp (Scanlan International, Inc.), the clamp was placed through a small incision in the anterior axillary line in the third or fourth intercostal space. In these cases, the pericardiotomy was cranially enlarged in order to have good exposition of the ascending aorta. An aortic-root needle was inserted in the aortic root for the purpose of cardioplegia delivery and aortic-root venting. The EAB was not used in patients with an ascending aorta diameter above 40 mm, according to the advice of the company that delivers this device. The chitwood clamp is then used. This is the only contraindication for the use of the EAB. An atrial retractor was placed through a small incision in the same intercostal space as the minithoracotomy, laterally from the right internal mammary artery.The aorta was clamped by means of either the direct transthoracic chitwood clamp, or through the inflation of the EAB under TEE guidance. Anterograde blood cardioplegia was administered through the aortic-root cannula in the EAC group, or through the central lumen of the EAB catheter. Blood cardioplegia solution, administered at 20-min intervals, was used for myocardial protection. In the EAB group, we made sure the cardioplegia pressure rose in the aortic root every time it was administered. The cardioplegia pressure in the aortic root must reach a pressure above 30 mmHg with a flow of cardioplegia at 250 ml/min. When the pressure in the aortic root during the cardioplegia delivery did not rise, the atrial-retractor or the EAB was repositioned in such manner that pressure elevation was restored. The left atrium was opened through an incision in the interatrial groove. In order to have optimal exposure of the MV, two sutures were placed in the anterior edge of the atriotomy. An atrial-retractor blade with a side arm (USB) was then positioned in order to have an optimal view over the entire MV annulus. Several different techniques for repair were used, depending on the mechanism of MR, chordal replacement was our preferred technique in case of chordal elongation or rupture (Table 2) [12]. At the end of the procedure, left ventricular de-airing was performed with a ventricular vent through the MV, and suction on the EAB lumen (in the EAB group) or the aortic-root needle (in the EAC group). The ventilation of the left lung was also started in this stadium for de-airing purpose. The left ventricular vent and the aortic needle were removed after establishing through TEE that there was no further air scattering within the left ventricle. The EAB was removed after weaning from CPB, during antegrade flow, for the same reason of risk of embolization from the descending aorta.
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Table 1: Baseline characteristics Parameter
Group A (EAC)
Group B (EAB)
P-value
Age (years) (median, IQR, range) Gender (male) BMI (kg/m2) (median, IQR, range) NYHA I II III EuroSCORE I (add) (median, IQR, range) Preoperative haemoglobin (mmol/l) (median, IQR, range) Preoperative creatinine (mmol/l) (median, IQR, range) LVF Normal (LVEF > 50%) Moderate (LVEF 30–50%) Poor (LVEF < 30%) COPD Peripheral artery disease CVA TIA Diabetes mellitus Hypertension Hypercholesterolaemia Pulmonary hypertension Atrial fibrillation Mitral stenosis Combined MR/MS Mitral regurgitation Grades 3 and 4 Carpentier I Carpentier II Carpentier IIIa Carpentier IIIb Barlow’s disease Endocarditis
62 (57–73) (28–84) 32 (56%) 25.1 (23.4–28.0) (19.2–39.5) – 7 (12%) 20 (35%) 31 (54%) 3 (2–6) (0–9) 8.8 (7.7–9.2) (6.4–10.4) 85 (72–96) (46–714) – 25 (46%) 25 (46%) 5 (9%) 6 (11%) 1 (2%) 4 (7%) 7 (12%) 6 (11%) 25 (44%) 8 (14%) 19 (33%) 25 (44%) 4 (7%) 3 (5%) 50 (88%) 48 (96%) 17 (34%) 30 (60%) 1 (2%) 2 (4%) 4 (8%) 1 (2%)
66 (60–74) (37–87) 92 (56%) 25 (22.4–27.4) (17.1–40.5) – 22 (13%) 57 (35%) 85 (52%) 2 (2–5) (0–10) 8.7 (8.0–9.2) (5.3–10.3) 83 (72–98) (47–312) – 112 (69%) 45 (28%) 7 (4%) 12 (7%) 2 (1%) 3 (2%) 9 (6%) 8 (5%) 67 (41%) 32 (20%) 38 (24%) 62 (38%) 5 (3%) 5 (3%) 154 (94%) 154 (100%) 37 (24%) 108 (70%) 2 (1%) 7 (4%) 19 (12%) 4 (3%)
0.078 0.10 0.34 – 0.83 0.96 0.74 0.56 0.99 0.93 – 0.002 0.019 0.18 0.45 1.00 0.075 0.13 0.20 0.69 0.36 0.14 0.44 0.24 0.43 0.15 0.059 0.17 0.18 0.57 1.00 0.61 1.00
IQR: interquartile range; BMI: body mass index; NYHA: New York Heart Association classification of dyspnoea; EuroSCORE: additive European System for Cardiac Operative Risk Evaluation; LVF: left ventricular function; COPD: chronic obstructive pulmonary disease; CVA: cerebrovascular accident; TIA: transient ischaemic attack; MR: mitral regurgitation; MS: mitral stenosis; EAC: external aortic clamp; EAB: endo-aortic balloon; LVEF: left ventricular ejection fraction.
group (1%); there were no mortalities in the EAC group (P = 1.000). Finally, there was no significant difference between Group A and Group B with respect to TEE MR gradation at discharge (Table 6).
Table 2: Surgical procedure Group B (EAB)
P-value
Parameters
Group A (EAC)
Concomitant maze procedure Replacement Repair Chordal replacement Resection Ring-use Size 26 Size 28 Size 30 Size 32 Size 34 Size 36
21 (37%)
56 (34%)
0.71
9 (16%) 48 (84%) 28 (58%) 2 (4%) 48 (100%) 1 (2%) 13 (27%) 18 (38%) 9 (19%) 6 (13%) 1 (2%)
15 (9%) 149 (91%) 98 (66%) 2 (1%) 146 (98%) 1 (1%) 27 (19%) 47 (32%) 23 (16%) 40 (27%) 8 (5%)
0.17 0.17 0.35 0.25 1.00 0.44 0.20 0.50 0.63 0.035 0.46
Maze: ablation surgery for atrial fibrillation; EAC: external aortic clamp; EAB: endo-aortic balloon.
In Group B, 10 patients (6%) required conversion from EAB to EAC for different reasons (Table 5); they were taken in to ITT analysis as well. Two patients died within 30 days of surgery in the EAB
DISCUSSION Our study compared the EAC and EAB in 221 patients undergoing MIMVS. Our primary outcomes were CPB-time, X-time and occurrence of postoperative CVA. We did not find significant differences between the two techniques regarding these outcomes. Baseline characteristics showed few differences in LVF between the two groups. The distribution was not equal in the group of normal LVF and moderate LVF. More patients in group EAB had normal LVF compared with group EAC, whereas less patients had moderate LVF compared with Group A. No differences in CPB- and X-time were found. Comparable studies show that CPB- and X-time are usually prolonged in the EAB groups [6, 13, 14]. Mazine et al. [6] reported that their results should be interpreted in the context of the initial experiences with the minimally invasive approach where the EAB was used and thus at the beginning of their experiences with this approach. Reichenspurner et al. [13] reported significantly longer crossclamping time and equal CPB time in a comparable study with 60
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Table 3: Perioperative data Parameters
Group A (EAC)
Group B (EAB)
P-value
CPB-time (min) (median, IQR, range) Cross-clamp time (min) (median, IQR, range) ICU stay (days) (median, IQR, range) Hospital stay (days) (median, IQR, range) Conversion to replacement Postoperative haemoglobin (mmol/l) (mean, SD) Postoperative creatinine (mmol/l) (median, IQR, range) Postoperative maximum Troponin T level (μg/l) (median, IQR, range)
135 (118–159) (79–197) 85 (66–100) (48–145) 1 (1–1) (0–5) 7 (7–10) (6–37) 0 7.3 ± 0.9SD 72 (61–85) (48–345) 0.667 (0.350–0.975) (0.161–8.650)
130 (113–149) (81–325) 77 (63–95) (39–237) 1 (1–1) (0–6) 6 (6–8) (4–44) 1 (1%) 7.2 ± 1.0SD 73 (64–87) (44–227) 0.449 (0.280–0.782) (0.117–6.190)
0.21 0.088 0.54 0.001 1.00 0.51 0.55 0.014
Table 4: Complications
Table 6:
Parameters
Group A (EAC)
Group B (EAB)
P-value
Conversion to sternotomy Groin lymphocele Aortal dissection DVT/PE Deep wound infection Pneumonia New onset AF Myocardial infarction Tamponade Rethoracotomy IABP dependence CVA Urinary tract infection Acute renal failure CVVH dependence
1 (2%) 0 0 0 0 3 (5%) 3 (5%) 2 (4%) 0 2 (4%) 0 0 0 1 (2%) 1 (2%)
1 (1%) 0 0 0 0 6 (4%) 23 (14%) 0 1 (1%) 5 (3%) 2 (1%) 3 (2%) 1 (1%) 4 (2%) 1 (1%)
0.45 – – – – 0.70 0.077 0.066 1.00 1.00 1.00 0.57 1.00 1.00 0.45
DVT: deep venous thrombosis; PE: pulmonary embolism; AF: atrial fibrillation; IABP: intra-aortal balloon pressure; CVA: cerebrovascular accident; CVVH: central veno venous haemodialysis; EAC: external aortic clamp; EAB: endo-aortic balloon.
Table 5: EAC
Reasons for intraoperative conversion of EAB to
Reason of conversion to EAB Unable to advance guidewire in Ascending aorta Abdominal aorta Unable to advance balloon in Femoral arteries Abdominal aorta Calcified descending aorta on TEE Iatrogenic balloon puncture High perfusion pressure Loss of balloon pressure
Number of cases
1 1 1 3 1 1 1 1
EAC: external aortic clamp; EAB: endo-aortic balloon; TEE: transoesophageal echocardiography.
patients in each group. They also reported that the learning curve could have played a role in the differences found. Ius et al. reported shorter CPB and X-time in the EAC. Furthermore, they reported
Mortality and MR gradation at discharge
Parameters
Group A (EAC)
Group B (EAB)
P-value
Thirty-day mortality MR gradation on discharge MR 0–1 MR 2 MR 3 MR 4
0 –
2 (1%) –
1.00 –
49 (98%) 1 (2%) 0 0
147 (99%) 0 1 (1%) 0
0.44 0.25 1.00 –
MR: mitral regurgitation; EAC: external aortic clamp; EAB: endo-aortic balloon.
their initial experiences with the minimally invasive approach in the EAB group [14]. In our series of 164 EAB patients, we were beyond the learning curve for the MIMVS approach. We started our experiences with this approach using the EAC. The cohort of 164 EAB-group contains also a sub-group, (n = 126) in which the latest EAB (the Intraclude) was used. The Intraclude is easier to position in the ascending aorta and it tends to migrate less during the procedure. These two reasons can potentially explain our findings of the equal CPB-time and X-time in these two groups. Loforte et al. [7] also found the same CPB-time and X-time in their comparison study between EAB and EAC in MIMVS approach. Krapf et al. [8] reported shorter CPB- and X-times in the EAB group in their comparison study in two large groups. However, these groups contained not only MV surgery patients but also endoscopic bypass surgery and other procedures. Occurrence of postoperative CVA, did not differ significantly between the EAC and EAB groups (0 vs 3, P = 0.57). Of these 3 patients with CVA, CVA occurred direct postoperatively in 2 patients, in 1 patient after 3 days. One patient recovered fully without any permanent damage. The total permanent stroke rate of the EAB group is 1.2% and for the whole cohort of 221 patients permanent stroke rate is 0.5%. Our findings are consistent with the comparison of EAC and EAB by other studies [6–8, 13, 14] in which no significant differences were found between these two groups either. Two studies reported a higher occurrence of microembolic events, registered by Trans Cranial Doppler ultrasound in the EAC group [7, 15]. However, these findings had no clinical consequences. The permanent stroke rate in our cohort is lower (0.5%) than that reported (1.7%) in literature [4]. We believe that our strategy
ORIGINAL ARTICLE
CPB: cardiopulmonary bypass; IQR: interquartile range; NS: not significant; ICU: intensive care unit; R: range; SD: standard deviation; EAC: external aortic clamp; EAB: endo-aortic balloon.
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of cooling to 30°C, the use of cerebral oximetry to detect cerebral ischaemia and the strict manipulation of the guidewire and the EAB ‘only’ during antegrade flow, are important factors that contribute to this low rate of permanent stroke. We did find a significant difference in hospital stay (median stay of 7 vs 6 days, P = 0.001) in favour of the EAB group. Other studies showed no difference in the duration of hospitalization in both the groups [7, 13], whereas Ius et al. even reported longer hospital stay in the EAB group. The explanation for the shorter hospital stay in our EAB group could be the use of the rib retractor in the EAC group. The patients in the EAC group had more pain that delayed early mobilization compared with those in the EAB group. Another reason is the change of postoperative treatment protocol of these patients in the nursing ward. After the first 100 consecutive patients, the protocol was changed to early mobilization and activation of these patients. These two reasons could explain the difference in the length of hospital stay between these two groups. We found a significant difference in postoperative maximum cardiac troponin levels, these were higher in the EAC group compared with the EAB group (P = 0.014). The first 27 patients in EAC group were treated with anterograde blood cardioplegia without cooling. From then on, all patients (30 patients in Group A and entire Group B) received anterograde blood cardioplegia in combination with cooling (to 30°C body temperature). Thereby, patients in the EAB group received anterograde cardioplegia after administration of adenosine through the lumen of the EAB. When we compared the first 27 patients (without cooling) of the EAC group with the latter 30 of the EAC group (with cooling), we found no significant difference in postoperative levels of cardiac troponin (P = 0.23). When we compared this second group of 30 patients in the EAC group, receiving cardioplegia with cooling, with the entire EAC group, receiving cardioplegia with cooling as well, we still found a significant difference in cardiac troponin levels, implying more myocardial damage in the EAC group (P = 0.008). This can potentially be explained by the prior administration of adenosine in the EAB group. Two studies proved that adenosine increases the potency of cardioplegia when administered in advance of the cardioplegia. This is possibly due to the inhibitory effects of adenosine on inflammatory-related processes in ischaemia [16, 17]. The difference cannot be explained either by a difference in the rate of concomitant atrial fibrillation (AF)-ablation surgery between the two groups (P = 0.71), which would be likely to induce more myocardial damage [18]. Other studies show no differences in myocardial damage [7] or more myocardial damage in the EAB group [14]. These studies, however, did not use blood cardioplegia, but crystalloid cardioplegia instead, and did not report the use of adenosine prior to cardioplegia administration, which therefore are difficult to compare with our results. Besides the use of the adenosine, we have a strict protocol for the use of antegrade blood cardioplegia when the EAB is used. As described above, the cardioplegia pressure in the aortic root must be above 30 mmHg, and the flow of cardioplegia must be at least 250 ml/min. The other studies did not report any strategy for observation of the antegrade cardioplegia delivery in the EAB group, only the strategy for retrograde cardioplegia was reported [6]. We believe that measuring the pressure rise above 30 mmHg in the aortic root and the amount of cardioplegia delivered to the aortic root is vital. Two causes can hinder the rise of pressure in the aortic root when EAB is used: the first cause is the deformation of the aortic annulus by the atrial-retractor blade (release of tension on the atrial-retractor blade will solve this problem) and the
second cause is malpositioning of the EAB with obstruction of the cardioplegia lumen by the aortic wall, thus diminishing the cardioplegia flow. Repositioning of the EAB will solve this problem. Ten patients (6%) in the EAB group were converted from EAB to EAC for several reasons (Table 5). In 7 patients, the conversion was due to the inability to advance the guidewire or the balloon in the ascending aorta. One patient was too tall (201 cm) for positioning of the EAB in the ascending aorta, the other 6 patients had femoral or aortic disease blocking the passage of the device. In 2 patients, conversion of EAB to EAC was due to puncture of the balloon and in one patient it was due to high pressures (above 350 mmHg) in the arterial cannula, without the possibility for contralateral cannulation. We did not find any significant differences in complications and clinical outcomes. This is consistent with other studies. Reichenspurner et al. [13], however, reported more re-explorations for bleeding and more complications in the EAB group, which is surprising because in the EAB group the ascending aorta is not punctured. Ius et al. [14] reported more cases of postoperatively prolonged ventilation (>72 h) in the EAB group. In our total cohort of 340 MIMVS procedures, neither aortic dissections nor femoral dissections were seen. We think this is because we do not accept arterial perfusion pressures above 350 mmHg and because we only dissect the anterior surface of the groin vessels and cannulate in the common femoral artery. The absence of any groin lymphocele postoperatively could also be due to this surgical technique.
Limitations There are two important limitations to our study. Firstly, data were collected retrospectively and therefore potentially biased. Secondly, the majority of the EAC group was operated prior to the EAB group and results can potentially be distorted by a learning curve. The fact that all patients were operated on by the same surgeon in our study, is a strength compared with other studies, which involved several surgeons. The learning curve of experience and the poorer LV function could be considered as a confounding factor in comparing the EAC and EAB group. Longer hospital stay with EAC and higher troponin levels may be influenced by the early experience; however, all surgery was performed by the same thoracic surgeon, who has extensive experience in mitral repair. A poorer LV function is generally not associated with a higher troponin level postoperatively in cardiac surgery, and there is no statistically significant difference in the rate of myocardial infarction between the two groups. Finally, our sample sizes were not equal. The EAC group consisted of 58 patients, whereas the EAB group consisted of 193 patients. This difference could potentially have influenced the significance between variables.
CONCLUSION MIMVS has become a standard approach for elective primary MV operations in our institution, and different techniques have been used to achieve aortic occlusion. These techniques were compared in our study. There were no differences in occurrence of CVA between the two clamping techniques. There were, however, significantly higher levels of postoperative measured cardiac troponin levels in the EAC group, implying more myocardial
damage. This could be caused by the addition of adenosine prior to cardioplegia delivery and monitoring of the cardioplegia pressures in the EAB, or because of the significant difference in LV function between both groups. Shorter hospital stay was found in the EAB group. Conversion from EAB to EAC was considered an important complication; it occurred in 6% of the EAB cases. In conclusion, there are no differences in use of the EAC and EAB regarding to CPB- and clamping-time, complications or clinical outcomes in our study. We do recommend that a randomized controlled trial be conducted in a referral centre where surgeons have completed their learning curve. Although this study has its limitations, a significant difference in postoperative troponine levels is found. The role of adenosine as myocardial protective agent should be further investigated.
[14]
[15]
[16]
[17]
[18]
Conflict of interest: Mohamed Bentala has a Consultancy agreement with Edwards life sciences.
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eComment. New onset atrial fibrillation induced by adenosine
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Authors: Omer Uz1, Veysel Temizkan2 and Zafer Isilak2 Deparment of Cardiovascular Surgery, GATA Haydarpasa Training Hospital, Istanbul, Turkey 2 Deparment of Cardiology, GATA Haydarpasa Training Hospital, Istanbul, Turkey doi: 10.1093/icvts/ivv216 © The Author 2015. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved. 1
We read with interest the article of Bentala et al [1]. The authors evaluated the differences in perioperative outcomes and complications between the endo-aortic balloon and the external aortic clamp during primary elective minimally invasive mitral valve surgery in a single referral centre by one surgeon. They reported that there was no difference in use between the endo-aortic balloon and the external aortic clamp in terms of cardiopulmonary bypass-time and cross-clamp time, complications or mitral regurgitation gradation at discharge. We appreciate the authors’ efforts on conducting this valuable study. Nevertheless, we would like to share our opinions about some of the results of the study. As it is known, adenosine has also been shown to have powerful sympathomimetic effects through chemoreceptor activation, especially when administered as a bolus. Sympathetic activation has been demonstrated to be an important part of autonomically-triggered pulmonary veins’ (PVs) firing in isolated canine preparations and intact dogs. Adenosine can also induce ectopy in electrically silent PVs that may lead to development of new onset atrial fibrillation [2]. It was reported that the number of new onset AF was found to be higher (though not statistically significant) in the endo-aortic balloon group when compared to that of external aortic clamp. We think that adenosine administered before cardioplegia in the endo-aortic balloon group might be the cause of new onset AF originating from pulmonary veins. Conflict of interest: none declared. References [1] Bentala M, Heuts S, Vos R, Maessen J, Scohy TV, Gerritse BM et al. Comparing the endo-aortic balloon and the external aortic clamp in minimally invasive mitral valve surgery. Interact CardioVasc Thorac Surg 2015;21:359–65. [2] Cheung JW, Ip JE, Chung JH, Markowitz SM, Liu CF, Thomas G et al. Differential effects of adenosine on pulmonary vein ectopy after pulmonary vein isolation: implications for arrhythmogenesis. Circ Arrhythm Electrophysiol 2012;1:659– 66.
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