Original Article
Retroaortic right internal thoracic artery grafting of circumflex artery targets
Asian Cardiovascular & Thoracic Annals 2015, Vol. 23(5) 543–551 ß The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0218492315573360 aan.sagepub.com
Oren Lev-Ran1, Menachem Matsa1, Yaron Ishay1, Amir Shabtai1, Alina Vodonos2 and Gideon Sahar1
Abstract Background: Retroaortic right internal thoracic artery grafting has failed to gain popularity. We aimed to delineate patient correlates of eligibility, distribution of targets, and effects of target remoteness on outcome and risk of retroaortic bleeding. Methods: Data of 861 patients undergoing skeletonized bilateral internal thoracic artery grafting (2007–2012) were analyzed according to retroaortic (n ¼ 300) or T-graft configuration. Retroaortic graft subgroups were categorized according to proximal (first obtuse marginal, ramus) or distal (2nd, 3rd, or sequential 1st-2nd obtuse marginal) circumflex artery targets. Results: LOESS curve analyses revealed that taller patients had a higher likelihood of retroaortic grafting. The distribution of 337 retroaortic graft targets (300 patients) was first obtuse marginal in 74.5%, 2nd marginal in 12.4%, ramus in 11.2%, 3rd marginal in 1.9% and sequential 1st-2nd marginal in 12.3%. The success rate in reaching proximal and distal circumflex artery targets was 97% and 30%, respectively, 5-year survival (92.2%) and freedom from major adverse cardiac and cerebrovascular events (85.8%) were comparable between proximal and distal retroaortic graft subgroups. Distal circumflex artery targets had no effect on the occurrence of major adverse cardiac and cerebrovascular events. The incidence of retroaortic bleeding from skeletonized retroaortic grafts was 0.6%. Conclusions: Taller patients have a greater likelihood of qualifying for retroaortic grafting. This technique is highly reproducible for proximal but not distal circumflex artery targets. Distal circumflex artery targets are not independent correlates of early or late adverse outcomes. The risk of retroaortic bleeding is low despite retroaortic right internal thoracic artery skeletonization.
Keywords Internal mammary-coronary artery anastomosis, coronary artery bypass, coronary artery disease, mammary arteries, thoracic arteries, treatment outcome
Introduction The use of bilateral internal thoracic arteries (BITA) during coronary artery bypass grafting (CABG) has been established as a determinant of improved longterm survival and event-free cardiac survival.1,2 Cardiac benefits are sustained throughout the first 20 postoperative years, and BITA grafting has now been recommended in patients with a life expectancy of 10 years or longer at the time of CABG.2 However, the prevalence of BITA use in contemporary practice remains significantly low, comprising 4% and 10% of CABG operations in the United States and Europe, respectively.3 Explanations for these results have
focused on a perceived high risk of sternal complications and concerns related to the BITA configuration, mainly the mode of right internal thoracic artery (RITA) utilization. Despite the extra length gained by 1 Department of Cardiothoracic Surgery, Soroka University Medical Center, Beer-Sheva, Israel 2 Clinical Research Center, Soroka University Medical Center, Beer-Sheva, Israel
Corresponding author: Oren Lev-Ran, MD, Department of Cardiothoracic Surgery, Soroka University Medical Center, Beer-Sheva, POB 151, 84101, Israel. Email: [email protected]
Downloaded from aan.sagepub.com at Monash University on November 17, 2015
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skeletonized harvesting,4 insufficient RITA length remains a limiting factor in in-situ BITA techniques and has led to increased use of composite T- or Y-configurations.5,6 Although this technique has proved feasible,6 concerns remain pertaining to the possibility of competitive flow, limited flow reserve, and inflow dependency on a single left internal thoracic artery (LITA) stem.5,7 Incomplete relief of ischemia, higher risk-adjusted morbidity, and a learning-curve effect has also been reported.7 Two techniques have been described for in-situ BITA revascularization of the left coronary system, distinguished by the RITA course in relation to the aorta and the respective coronary targets. The ante-aortic RITA technique has been shown to be feasible in terms of RITA accessibility to the left anterior descending artery (LAD) and patency rate,5,8 but enthusiasm for this approach has been offset by the risk to a patent retrosternal RITA conduit during a subsequent sternotomy. The retroaortic RITA (rRITA) technique, in which rRITA is routed to circumflex artery (Cx) targets through the transverse sinus,9,10 has failed to gain popularity. Data in the literature are scarce and available reports differ in technical aspects including the method of RITA procurement, the method of retroaortic routing, and surgeons’ discretion to use distal RITA postbifurcation segments. This technique confers the benefits of multiple internal thoracic artery (ITA) inflow, maintains the gold standard LITA-LAD graft, technical simplicity, and avoidance of the disadvantages of other BITA arrangements. However, it appears that concerns regarding rRITA accessibility, the feasibility of grafting remote Cx targets, and the risk of retroaortic bleeding deter surgeons from using this technique. The aim of this study was to delineate morphological and demographical patient characteristics that may aid in predicting rRITA accessibility, to evaluate the feasibility of distal Cx grafting, and to assess the incidence of retroaortic bleeding from skeletonized rRITA conduits. Early and long-term results are presented, and technical aspects are discussed.
Patients and methods The protocol of this study was approved by the institutional ethics committee, and individual consent was waived. The data of 861 consecutive patients undergoing left-sided BITA grafting between May 2007 and December 2012 were reviewed. The morphological and demographical descriptors of patients undergoing rRITA grafting (retroaortic group; n ¼ 300) were compared with those of patients undergoing T-grafts (n ¼ 561). The retroaortic group was further categorized, according to Cx target remoteness, as proximal and distal subgroups. The proximal subgroup was
defined as rRITA Cx targets: ramus intermedius or first obtuse marginal artery (M1); the distal subgroup was defined as Cx targets: second obtuse marginal artery (M2), third obtuse marginal artery (M3), or sequential M1-M2. During the study period, BITA were used on a routine basis in the following configurations: T-grafts, rRITA, ante-aortic RITA, and RITA to right coronary artery in 53.6%, 28.6%, 6%, and 11.6% of the patients, respectively. The study cohort comprised 82.3% of all 1046 BITA patients. Contraindications for use of BITA were relative and included chronic lung disease or the combination of female sex and body mass index (BMI) >30 kgm2; these correlates were previously defined as risk factors for deep sternal wound infection, irrespective of BITA configuration.5 Included were patients undergoing isolated primary CABG operations. Patient allocation to either configuration was based on intraoperative RITA length measurements and at the discretion of the surgeon. Both ITA were harvested as skeletonized conduits.4,5 The RITA was harvested distal to its bifurcation. The larger post-bifurcation branch, either the superior epigastric artery or the musculophrenic artery, was mobilized 1–1.5 cm distally. Post-bifurcation segments were considered adequate for use following assessment of distal caliber, distal flow, and mural quality, and excluding the possibility of a graft-coronary size mismatch. In-situ rRITA was routed into the transverse sinus via an opening in the right pericardium. The pericardial opening was developed by blunt dissection without the use of electrocautery, to avoid right phrenic nerve injury. Length assessment was performed on a non-vented beating heart after initiation of cardiopulmonary bypass but prior to crossclamping. All operations were carried out through a midline sternotomy using standard cardiopulmonary bypass and intermittent antegrade or retrograde tepid blood cardioplegia. In all patients, the LITA was used to graft the LAD (with or without a sequential diagonal artery). If required, radial artery conduits were preferentially used to graft the right coronary system, attached proximally to the aorta; if target-vessel stenosis was 70% or less, greater saphenous veins were used. Proximal anastomoses were performed during a single crossclamp application, without the use of an aortic side-clamp. Patients’ data were analyzed according to the Society of Thoracic Surgeons National Cardiac Surgery Database guidelines and definitions. Early major adverse events were defined as the occurrence of 30day mortality, perioperative myocardial infarction, or a cerebrovascular event. Cardiac mortality was defined as death related to myocardial infarction, cardiac arrhythmia, out-of-hospital sudden death, or deteriorating congestive heart failure. Undetermined causes of
Downloaded from aan.sagepub.com at Monash University on November 17, 2015
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death were regarded as cardiac. Major adverse cardiac or cerebrovascular events (MACCE) were defined as the occurrence of late cardiac death, a late nonfatal myocardial infarction, the need for repeat revascularization, or a late cerebrovascular event. Follow-up was obtained by telephone questionnaires and the computed registry database. The categoric variables were tested for group independence using the chisquared test. The results are expressed as percentages and p values. Numeric variables were compared with both the t test and the nonparametric Mann-Whitney test. Data are expressed as mean standard deviation with the p value. Logistic regression was used to evaluate the effect of preoperative and intraoperative descriptors on the occurrence of early major adverse events. Results of logistic regression are expressed as the odds ratio with the associated 95% confidence interval and p value. A Cox hazard model was used to evaluate the effect of preoperative and intraoperative descriptors on the occurrence of all-cause mortality and MACCE. Results are expressed as the hazard ratio with associated 95% confidence interval and p value. All analyses were performed with SPSS version 18 software (SPSS, Inc., Chicago, IL, USA). A scatter plot with overlay of a LOESS (locally weighted scatter plot smoothing) curve was produced. The LOESS curve provides graphic presentation of data derived from a multivariate logistic regression model.
Results The morphological and demographical patient characteristics are detailed in Table 1. Patients undergoing rRITA grafting were taller (170 8.3 vs. 168 10.6 cm, p ¼ 0.006), but the distribution of other morphological and demographical patient descriptors was comparable between both BITA configuration groups. LOESS curves derived from the multivariate logistic regression model were used to assess the likelihood of undergoing the retroaortic technique. Variables assessed in this model were age, sex, height, weight, BMI, and body
surface area, as well as combinations of these factors. The results of this analysis showed that height was the only effector to correlate with the likelihood of undergoing rRITA grafting (Figure 1). The effect of height was independent of other confounders. This correlation was apparent in both sexes (Figure 1). A total of 337 Cx anastomoses were performed in 300 patients by rRITA. Cx target distribution was M1, M2, ramus intermedius, and M3 in 74.5%, 12.4%, 11.2% and 1.9%, respectively (Table 2). Sequential M1-M2 grafting was performed in 12.4% of patients. While the success rate of reaching the M1 or ramus intermedius targets (proximal targets) was constant (97% of cases), the success rate of reaching distal Cx targets (M2, M3 or sequential M1-M2) varied significantly between surgeons and ranged between 20% and 40%. The proximal subgroup constituted 84% of patients (distal subgroup 16%; Table 2). Baseline characteristics were comparable between subgroups, with the exception of previous cerebrovascular disease. Operative data are presented in Table 2. Early postoperative results are detailed in Table 3. The incidence of reexploration for bleeding was 1.7% (5 patients). The source of bleeding was identified as the left or right ITA procurement site in 4 patients and unidentified in one patient. There was no bleeding related to the rRITA in any of these patients. Repeat manipulation of a grafted rRITA (after weaning from cardiopulmonary bypass but prior to chest closure) was necessary in 2 (0.6%) patients. Additional metal clips were placed on rRITA side-branches for active bleeding (1 patient) and for clip reinforcement (1 patient). There was no difference in postoperative results between the retroaortic subgroups (Table 3). Follow-up ranged from 22 to 59 months (median 43 months) and was obtained in 99% of cases. Late results are listed in Table 3. Postoperative angiograms were limited to symptom-directed patients and consequently performed in 23 (7.6%); a total of 24 distal rRITA anastomoses were demonstrated (sequential rRITA in one patient) at 37 19 months (range 6–54 months),
Table 1. Morphological and demographical characteristics of 861 patients undergoing coronary artery bypass grafting of circumflex artery targets. Variable
Retroaortic group n ¼ 300
T-graft group n ¼ 561
p value
Age (years) Female sex Height (cm) Weight (kg) BMI (kgm2) BSA (m2)
59.0 8.4 10.3% 170.2 8.3 81.0 13.4 28.1 4.1 1.9 0.25
59.7 8.9 13.1% 168.2 10.6 79.8 13.4 28.1 4.0 1.9 0.19
0.263 0.250 0.006 0.212 0.916 0.307
BMI: body mass index; BSA: body surface area.
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Asian Cardiovascular & Thoracic Annals 23(5)
Figure 1. The effect of patient height on the likelihood of undergoing rRITA grafting. LOESS curves created by a logistic regression model. rRITA: retroaortic right internal thoracic artery.
resulting in overall rRITA patency of 87.5% (21/24). At 5 years, the overall reintervention rate was 2.7%, and reintervention in rRITA-grafted coronary arteries was 1%. No repeat CABG operations were performed. Five-year freedom (Kaplan-Meier) from allcause mortality and freedom from MACCE was 92.2% and 85.8%, respectively. Survival at 1 and 5 years was comparable between the proximal and distal subgroups (log-rank p ¼ 0.675): 99.2% and 92.4%, and 100% and 91.7%, respectively (Figure 2). Freedom from MACCE at 1 and 5 years postoperatively was comparable between both subgroups (log-rank p ¼ 0.909): 98.8% and 88.5%, and 97.9% and 92.5%, respectively (Figure 3). Multivariate correlates of early and late endpoints are summarized in Table 4. Diabetes mellitus was identified as an independent predictor of early major adverse events (logistic regression p ¼ 0.024, odds ratio 6.4). Distal Cx targets (p ¼ 0.942, odds ratio 1) were not effectors for the occurrence of early major adverse events. Independent predictors of late all-cause mortality were preoperative renal dysfunction (defined as serum creatinine >2 mgdL1; p ¼ 0.0022, hazard ratio 18.8) and BMI (Cox hazard model p ¼ 0.019, hazard ratio 1.3). A serum creatinine level greater than 2 mgdL1 was identified as a predictor of MACCE (p < 0.001, hazard ratio 13.2). Distal Cx targets did not independently correlate with all-cause mortality or MACCE (Table 4).
Discussion Studies examining Cx accessibility by rRITA are scarce and have yielded inconsistent results. Success rates in reaching proximal and distal Cx targets of 96% and 92%, respectively, were reported by Ura and colleagues.11 Bonacchi and colleagues12 proposed that any Cx branch could be reached by rRITA, irrespective of its remoteness. Conversely, Tatoulis and colleagues6 concluded that distal Cx targets cannot be readily reached despite the extra length conferred by rRITA skeletonization. Explanations for these discrepancies can be partly attributed to technical differences between surgeons. It seems that most centers using rRITA via the transverse sinus on a routine basis have adopted technical alterations to enhance its length or reciprocally shorten its retroaortic course. The maneuvers reported to elongate rRITA grafts include skeletonized RITA procurement or inclusion of post-bifurcation RITA segments in the bypass graft, and retrocaval RITA routing has been proposed to shorten its route.5–7,11,12 In our study, the rRITA conduits were invariably skeletonized, elongated by 1–1.5 cm postbifurcation segments, and routed ante-caval via the transverse sinus. Our results indicate that proximal Cx targets (M1 or ramus intermedius) are highly accessible by the rRITA. Importantly, accessibility to proximal Cx targets was reproducible irrespective of the individual surgeon. It is consequently implied that rRITA grafting can be preplanned when proximal Cx
Downloaded from aan.sagepub.com at Monash University on November 17, 2015
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Table 2. Baseline characteristics and operative data of the retroaortic right internal thoracic artery group.
Variable Age (years) Female sex Height (cm) Weight (kg) BMI (kgm2) BMI >30 (kgm2) BSA (m2) EuroSCORE Diabetes mellitus Insulin treatment Arterial vascular disease Creatinine >2 mgdL1 Chronic lung disease Cerebrovascular disease Congestive heart failure Ejection fraction
Retroaortic right internal thoracic artery grafting of circumflex artery targets
Asian Cardiovascular & Thoracic Annals 2015, Vol. 23(5) 543–551 ß The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav DOI: 10.1177/0218492315573360 aan.sagepub.com
Oren Lev-Ran1, Menachem Matsa1, Yaron Ishay1, Amir Shabtai1, Alina Vodonos2 and Gideon Sahar1
Abstract Background: Retroaortic right internal thoracic artery grafting has failed to gain popularity. We aimed to delineate patient correlates of eligibility, distribution of targets, and effects of target remoteness on outcome and risk of retroaortic bleeding. Methods: Data of 861 patients undergoing skeletonized bilateral internal thoracic artery grafting (2007–2012) were analyzed according to retroaortic (n ¼ 300) or T-graft configuration. Retroaortic graft subgroups were categorized according to proximal (first obtuse marginal, ramus) or distal (2nd, 3rd, or sequential 1st-2nd obtuse marginal) circumflex artery targets. Results: LOESS curve analyses revealed that taller patients had a higher likelihood of retroaortic grafting. The distribution of 337 retroaortic graft targets (300 patients) was first obtuse marginal in 74.5%, 2nd marginal in 12.4%, ramus in 11.2%, 3rd marginal in 1.9% and sequential 1st-2nd marginal in 12.3%. The success rate in reaching proximal and distal circumflex artery targets was 97% and 30%, respectively, 5-year survival (92.2%) and freedom from major adverse cardiac and cerebrovascular events (85.8%) were comparable between proximal and distal retroaortic graft subgroups. Distal circumflex artery targets had no effect on the occurrence of major adverse cardiac and cerebrovascular events. The incidence of retroaortic bleeding from skeletonized retroaortic grafts was 0.6%. Conclusions: Taller patients have a greater likelihood of qualifying for retroaortic grafting. This technique is highly reproducible for proximal but not distal circumflex artery targets. Distal circumflex artery targets are not independent correlates of early or late adverse outcomes. The risk of retroaortic bleeding is low despite retroaortic right internal thoracic artery skeletonization.
Keywords Internal mammary-coronary artery anastomosis, coronary artery bypass, coronary artery disease, mammary arteries, thoracic arteries, treatment outcome
Introduction The use of bilateral internal thoracic arteries (BITA) during coronary artery bypass grafting (CABG) has been established as a determinant of improved longterm survival and event-free cardiac survival.1,2 Cardiac benefits are sustained throughout the first 20 postoperative years, and BITA grafting has now been recommended in patients with a life expectancy of 10 years or longer at the time of CABG.2 However, the prevalence of BITA use in contemporary practice remains significantly low, comprising 4% and 10% of CABG operations in the United States and Europe, respectively.3 Explanations for these results have
focused on a perceived high risk of sternal complications and concerns related to the BITA configuration, mainly the mode of right internal thoracic artery (RITA) utilization. Despite the extra length gained by 1 Department of Cardiothoracic Surgery, Soroka University Medical Center, Beer-Sheva, Israel 2 Clinical Research Center, Soroka University Medical Center, Beer-Sheva, Israel
Corresponding author: Oren Lev-Ran, MD, Department of Cardiothoracic Surgery, Soroka University Medical Center, Beer-Sheva, POB 151, 84101, Israel. Email: [email protected]
Downloaded from aan.sagepub.com at Monash University on November 17, 2015
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Asian Cardiovascular & Thoracic Annals 23(5)
skeletonized harvesting,4 insufficient RITA length remains a limiting factor in in-situ BITA techniques and has led to increased use of composite T- or Y-configurations.5,6 Although this technique has proved feasible,6 concerns remain pertaining to the possibility of competitive flow, limited flow reserve, and inflow dependency on a single left internal thoracic artery (LITA) stem.5,7 Incomplete relief of ischemia, higher risk-adjusted morbidity, and a learning-curve effect has also been reported.7 Two techniques have been described for in-situ BITA revascularization of the left coronary system, distinguished by the RITA course in relation to the aorta and the respective coronary targets. The ante-aortic RITA technique has been shown to be feasible in terms of RITA accessibility to the left anterior descending artery (LAD) and patency rate,5,8 but enthusiasm for this approach has been offset by the risk to a patent retrosternal RITA conduit during a subsequent sternotomy. The retroaortic RITA (rRITA) technique, in which rRITA is routed to circumflex artery (Cx) targets through the transverse sinus,9,10 has failed to gain popularity. Data in the literature are scarce and available reports differ in technical aspects including the method of RITA procurement, the method of retroaortic routing, and surgeons’ discretion to use distal RITA postbifurcation segments. This technique confers the benefits of multiple internal thoracic artery (ITA) inflow, maintains the gold standard LITA-LAD graft, technical simplicity, and avoidance of the disadvantages of other BITA arrangements. However, it appears that concerns regarding rRITA accessibility, the feasibility of grafting remote Cx targets, and the risk of retroaortic bleeding deter surgeons from using this technique. The aim of this study was to delineate morphological and demographical patient characteristics that may aid in predicting rRITA accessibility, to evaluate the feasibility of distal Cx grafting, and to assess the incidence of retroaortic bleeding from skeletonized rRITA conduits. Early and long-term results are presented, and technical aspects are discussed.
Patients and methods The protocol of this study was approved by the institutional ethics committee, and individual consent was waived. The data of 861 consecutive patients undergoing left-sided BITA grafting between May 2007 and December 2012 were reviewed. The morphological and demographical descriptors of patients undergoing rRITA grafting (retroaortic group; n ¼ 300) were compared with those of patients undergoing T-grafts (n ¼ 561). The retroaortic group was further categorized, according to Cx target remoteness, as proximal and distal subgroups. The proximal subgroup was
defined as rRITA Cx targets: ramus intermedius or first obtuse marginal artery (M1); the distal subgroup was defined as Cx targets: second obtuse marginal artery (M2), third obtuse marginal artery (M3), or sequential M1-M2. During the study period, BITA were used on a routine basis in the following configurations: T-grafts, rRITA, ante-aortic RITA, and RITA to right coronary artery in 53.6%, 28.6%, 6%, and 11.6% of the patients, respectively. The study cohort comprised 82.3% of all 1046 BITA patients. Contraindications for use of BITA were relative and included chronic lung disease or the combination of female sex and body mass index (BMI) >30 kgm2; these correlates were previously defined as risk factors for deep sternal wound infection, irrespective of BITA configuration.5 Included were patients undergoing isolated primary CABG operations. Patient allocation to either configuration was based on intraoperative RITA length measurements and at the discretion of the surgeon. Both ITA were harvested as skeletonized conduits.4,5 The RITA was harvested distal to its bifurcation. The larger post-bifurcation branch, either the superior epigastric artery or the musculophrenic artery, was mobilized 1–1.5 cm distally. Post-bifurcation segments were considered adequate for use following assessment of distal caliber, distal flow, and mural quality, and excluding the possibility of a graft-coronary size mismatch. In-situ rRITA was routed into the transverse sinus via an opening in the right pericardium. The pericardial opening was developed by blunt dissection without the use of electrocautery, to avoid right phrenic nerve injury. Length assessment was performed on a non-vented beating heart after initiation of cardiopulmonary bypass but prior to crossclamping. All operations were carried out through a midline sternotomy using standard cardiopulmonary bypass and intermittent antegrade or retrograde tepid blood cardioplegia. In all patients, the LITA was used to graft the LAD (with or without a sequential diagonal artery). If required, radial artery conduits were preferentially used to graft the right coronary system, attached proximally to the aorta; if target-vessel stenosis was 70% or less, greater saphenous veins were used. Proximal anastomoses were performed during a single crossclamp application, without the use of an aortic side-clamp. Patients’ data were analyzed according to the Society of Thoracic Surgeons National Cardiac Surgery Database guidelines and definitions. Early major adverse events were defined as the occurrence of 30day mortality, perioperative myocardial infarction, or a cerebrovascular event. Cardiac mortality was defined as death related to myocardial infarction, cardiac arrhythmia, out-of-hospital sudden death, or deteriorating congestive heart failure. Undetermined causes of
Downloaded from aan.sagepub.com at Monash University on November 17, 2015
Lev-Ran et al.
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death were regarded as cardiac. Major adverse cardiac or cerebrovascular events (MACCE) were defined as the occurrence of late cardiac death, a late nonfatal myocardial infarction, the need for repeat revascularization, or a late cerebrovascular event. Follow-up was obtained by telephone questionnaires and the computed registry database. The categoric variables were tested for group independence using the chisquared test. The results are expressed as percentages and p values. Numeric variables were compared with both the t test and the nonparametric Mann-Whitney test. Data are expressed as mean standard deviation with the p value. Logistic regression was used to evaluate the effect of preoperative and intraoperative descriptors on the occurrence of early major adverse events. Results of logistic regression are expressed as the odds ratio with the associated 95% confidence interval and p value. A Cox hazard model was used to evaluate the effect of preoperative and intraoperative descriptors on the occurrence of all-cause mortality and MACCE. Results are expressed as the hazard ratio with associated 95% confidence interval and p value. All analyses were performed with SPSS version 18 software (SPSS, Inc., Chicago, IL, USA). A scatter plot with overlay of a LOESS (locally weighted scatter plot smoothing) curve was produced. The LOESS curve provides graphic presentation of data derived from a multivariate logistic regression model.
Results The morphological and demographical patient characteristics are detailed in Table 1. Patients undergoing rRITA grafting were taller (170 8.3 vs. 168 10.6 cm, p ¼ 0.006), but the distribution of other morphological and demographical patient descriptors was comparable between both BITA configuration groups. LOESS curves derived from the multivariate logistic regression model were used to assess the likelihood of undergoing the retroaortic technique. Variables assessed in this model were age, sex, height, weight, BMI, and body
surface area, as well as combinations of these factors. The results of this analysis showed that height was the only effector to correlate with the likelihood of undergoing rRITA grafting (Figure 1). The effect of height was independent of other confounders. This correlation was apparent in both sexes (Figure 1). A total of 337 Cx anastomoses were performed in 300 patients by rRITA. Cx target distribution was M1, M2, ramus intermedius, and M3 in 74.5%, 12.4%, 11.2% and 1.9%, respectively (Table 2). Sequential M1-M2 grafting was performed in 12.4% of patients. While the success rate of reaching the M1 or ramus intermedius targets (proximal targets) was constant (97% of cases), the success rate of reaching distal Cx targets (M2, M3 or sequential M1-M2) varied significantly between surgeons and ranged between 20% and 40%. The proximal subgroup constituted 84% of patients (distal subgroup 16%; Table 2). Baseline characteristics were comparable between subgroups, with the exception of previous cerebrovascular disease. Operative data are presented in Table 2. Early postoperative results are detailed in Table 3. The incidence of reexploration for bleeding was 1.7% (5 patients). The source of bleeding was identified as the left or right ITA procurement site in 4 patients and unidentified in one patient. There was no bleeding related to the rRITA in any of these patients. Repeat manipulation of a grafted rRITA (after weaning from cardiopulmonary bypass but prior to chest closure) was necessary in 2 (0.6%) patients. Additional metal clips were placed on rRITA side-branches for active bleeding (1 patient) and for clip reinforcement (1 patient). There was no difference in postoperative results between the retroaortic subgroups (Table 3). Follow-up ranged from 22 to 59 months (median 43 months) and was obtained in 99% of cases. Late results are listed in Table 3. Postoperative angiograms were limited to symptom-directed patients and consequently performed in 23 (7.6%); a total of 24 distal rRITA anastomoses were demonstrated (sequential rRITA in one patient) at 37 19 months (range 6–54 months),
Table 1. Morphological and demographical characteristics of 861 patients undergoing coronary artery bypass grafting of circumflex artery targets. Variable
Retroaortic group n ¼ 300
T-graft group n ¼ 561
p value
Age (years) Female sex Height (cm) Weight (kg) BMI (kgm2) BSA (m2)
59.0 8.4 10.3% 170.2 8.3 81.0 13.4 28.1 4.1 1.9 0.25
59.7 8.9 13.1% 168.2 10.6 79.8 13.4 28.1 4.0 1.9 0.19
0.263 0.250 0.006 0.212 0.916 0.307
BMI: body mass index; BSA: body surface area.
Downloaded from aan.sagepub.com at Monash University on November 17, 2015
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Asian Cardiovascular & Thoracic Annals 23(5)
Figure 1. The effect of patient height on the likelihood of undergoing rRITA grafting. LOESS curves created by a logistic regression model. rRITA: retroaortic right internal thoracic artery.
resulting in overall rRITA patency of 87.5% (21/24). At 5 years, the overall reintervention rate was 2.7%, and reintervention in rRITA-grafted coronary arteries was 1%. No repeat CABG operations were performed. Five-year freedom (Kaplan-Meier) from allcause mortality and freedom from MACCE was 92.2% and 85.8%, respectively. Survival at 1 and 5 years was comparable between the proximal and distal subgroups (log-rank p ¼ 0.675): 99.2% and 92.4%, and 100% and 91.7%, respectively (Figure 2). Freedom from MACCE at 1 and 5 years postoperatively was comparable between both subgroups (log-rank p ¼ 0.909): 98.8% and 88.5%, and 97.9% and 92.5%, respectively (Figure 3). Multivariate correlates of early and late endpoints are summarized in Table 4. Diabetes mellitus was identified as an independent predictor of early major adverse events (logistic regression p ¼ 0.024, odds ratio 6.4). Distal Cx targets (p ¼ 0.942, odds ratio 1) were not effectors for the occurrence of early major adverse events. Independent predictors of late all-cause mortality were preoperative renal dysfunction (defined as serum creatinine >2 mgdL1; p ¼ 0.0022, hazard ratio 18.8) and BMI (Cox hazard model p ¼ 0.019, hazard ratio 1.3). A serum creatinine level greater than 2 mgdL1 was identified as a predictor of MACCE (p < 0.001, hazard ratio 13.2). Distal Cx targets did not independently correlate with all-cause mortality or MACCE (Table 4).
Discussion Studies examining Cx accessibility by rRITA are scarce and have yielded inconsistent results. Success rates in reaching proximal and distal Cx targets of 96% and 92%, respectively, were reported by Ura and colleagues.11 Bonacchi and colleagues12 proposed that any Cx branch could be reached by rRITA, irrespective of its remoteness. Conversely, Tatoulis and colleagues6 concluded that distal Cx targets cannot be readily reached despite the extra length conferred by rRITA skeletonization. Explanations for these discrepancies can be partly attributed to technical differences between surgeons. It seems that most centers using rRITA via the transverse sinus on a routine basis have adopted technical alterations to enhance its length or reciprocally shorten its retroaortic course. The maneuvers reported to elongate rRITA grafts include skeletonized RITA procurement or inclusion of post-bifurcation RITA segments in the bypass graft, and retrocaval RITA routing has been proposed to shorten its route.5–7,11,12 In our study, the rRITA conduits were invariably skeletonized, elongated by 1–1.5 cm postbifurcation segments, and routed ante-caval via the transverse sinus. Our results indicate that proximal Cx targets (M1 or ramus intermedius) are highly accessible by the rRITA. Importantly, accessibility to proximal Cx targets was reproducible irrespective of the individual surgeon. It is consequently implied that rRITA grafting can be preplanned when proximal Cx
Downloaded from aan.sagepub.com at Monash University on November 17, 2015
Lev-Ran et al.
547
Table 2. Baseline characteristics and operative data of the retroaortic right internal thoracic artery group.
Variable Age (years) Female sex Height (cm) Weight (kg) BMI (kgm2) BMI >30 (kgm2) BSA (m2) EuroSCORE Diabetes mellitus Insulin treatment Arterial vascular disease Creatinine >2 mgdL1 Chronic lung disease Cerebrovascular disease Congestive heart failure Ejection fraction
