454
The Journal of Heart and Lung Transplantation, Vol 33, No 4, April 2014
these patients survived,3 the patient described in this study will be followed by a medical geneticist. SVT is the most common arrhythmia with cardiac tumors in the neonatal period, and rhabdomyoma can be associated with ventricular pre-excitation.4 Evolution of inconsistent arrhythmia types suggests that the patient’s re-entrant tachycardia was not mediated by an embryonic accessory pathway. Destruction of the conduction system has been described in diffuse rhabdomyomatosis,5 and likely explains the unusual progression of this patient’s arrhythmias. Analogous alternate routes of conduction have been described in glycogen-storage disease, whereby diffuse myocardial infiltration may connect atrial and ventricular myocardium, resulting in pre-excitation. The differential diagnosis for infantile HCM includes primary sarcomeric defects, infiltrative cardiomyopathies with diagnosable biochemical perturbations, and syndromic cardiomyopathies. However, the presence of refractory arrhythmias and fluctuating wall thickness changes in a patient with diffuse ventricular thickening may indicate an alternative diagnoses, such as diffuse rhabdomyomatosis. This patient’s clinical course was atypical for sarcomeric HCM. Her early, severe and rapid progression to heart failure, recalcitrant SVT, and evolving arrhythmias were clues to a diagnosis other than HCM, which may have changed our approach to management. If diffuse rhabdomyomatosis was suspected and confirmed by biopsy, an electrophysiology study with the potential for decompensation would not have been pursued
Intraoperative transesophageal echocardiographic guidance of total artificial heart implantation Nowell M. Fine, MD,a Radha S. Gopalan, MD,b Francisco A. Arabia, MD,c Sudhir S. Kushwaha, MD,a and Krishnaswamy Chandrasekaran, MDa,b From the aDivision of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota; b Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Scottsdale, Arizona; and the cDivision of Cardiovascular Surgery, Department of Surgery, Cedars-Sinai Medical Center, Los Angeles, California
For advanced heart failure patients who are candidates for mechanical circulatory support (MCS) but are at increased risk for poor outcomes after left ventricular assist device implantation, the total artificial heart (TAH) has become an important therapeutic option.1–3 The SynCardia TAH (SynCardia Systems Inc, Tucson, AZ) became the first TAH approved for use in the United States in 2004, and the number TAH-implanting centers is growing.2 Centers that perform echocardiography on MCS-supported patients have endeavored to characterize the signs of abnormal device function to deliver useful information in a timely manner. However, little is known about the role of intraoperative (IO) transesophageal echocardiography (TEE) during TAH implantation. In this report, we describe the role of IO-TEE during TAH implantation and discuss the utility and limitations of IO-TEE guidance.
aggressively. Given the natural history of diffuse rhabdomyomatosis, ablation could have been avoided and transplantation may have been pursued earlier, which is important because early transplant outcomes are directly related to the need for extracorporeal membrane oxygen (ECMO) support before transplantation.
Disclosure statement The authors have no conflicts of interest to disclose. We thank Lawrence Merritt, MD, for valuable input.
References 1. Coates TL, McGahan JP. Fetal cardiac rhabdomyomas presenting as diffuse myocardial thickening. J Ultrasound Med 1994;13:813-6. 2. Shrivastava S, Jacks JJ, White RS, et al. Diffuse rhabdomyomatosis of the heart. Arch Pathol Lab Med 1977;101:78-80. 3. Verhaaren HA, Venaaker O, De Wolf D, et al. Left ventricular outflow obstruction in rhabdomyoma of infancy: meta-analysis of the literature. J Pediatr 2003;143:258-63. 4. Gotlieb AI, Chan M, Palmer WH, et al. Ventricular preexcitation syndrome. Accessory left atrioventricular connection and rhabdomyomatous myocardial fibers. Arch Pathol Lab Med 1977;101:486-9. 5. Mandke JV, Kinare SG, Phatak AM. Congenital diffuse rhabdomyomatosis of the heart with biventricular outflow obstruction. Indian Heart J 1992;44:187-8.
Echocardiographic imaging of the TAH requires a thorough understanding of the device and its components, as well as the implantation procedure. During implantation, the ventricular portion of the recipient heart is excised, leaving only a rim of ventricular myocardium. The atria and their respective venous connections are left intact and form the atrial chambers of the TAH. The aortic and pulmonary roots are excised just above the aortic and pulmonary valves, leaving the distal ascending aorta and distal main pulmonary artery (PA) intact. The SynCardia TAH unit has 2 separate pneumatic pumping chambers, representing the left and right ventricles (the TAH components are illustrated in Supplementary Figure 1, available on the jhltonline.org Web site). The TAH also contains four Medtronic-Hall single-tilting disk valve prostheses (Medtronic-Hall, Medtronic, Minneapolis, MN) in each valvular position. Each pneumatic pumping chamber has an inlet valve representing the mitral and tricuspid valve and an outlet valve representing the aortic and pulmonary valve. The pneumatic pumping chambers are sutured to the rim of the ventricular myocardium adjoining the atrioven tricular groove. The outlet valves are connected to the retained native ascending aorta and PA, respectively, by a conduit. The diaphragms within each pumping chamber are pneumatically driven by an external driver that is connected by left and right drivelines tunneled extraperitoneally through the abdominal wall. The retention of both atria provide for an excellent imaging window of the TAH from the middle and upper esophageal IO-TEE imaging windows. Figure 1 shows IO-TEE images
Case Anecdotes, Comments and Opinions
455
Figure 1 Intra-operative transesophageal echocardiography from the midesophageal imaging window after implantation of the SynCardia (SynCardia Systems Inc, Tucson, AZ) total artificial heart demonstrates an intact right atrium (RA) and left atrium (LA), with prosthetic right (RIV) and left (LIV) single-tilting disk inlet valves (yellow arrows) in the (A) open and (B) closed positions. The prosthetic valves are anchored to ventricular rims and lead into their respective pneumatic pumping chambers (ventricles). Acoustic artifact from the pneumatic pumping chambers and prosthetic inlet valves obscure visualization of structures distal to the ventricular rims. The prosthetic right singletilting disk inlet valve is shown in the (C) open position with color inflow into the right pneumatic ventricle (RPV) and in the (D) closed position. A mild regurgitant washing jet (yellow arrow) in the closed position is present with (D) normal prosthetic valve function. (E) The prosthetic left single-tilting disk outlet valve is shown (yellow arrow) in the (left image) short-axis and (right image) long-axis views. (F) The prosthetic right single-tilting disk outlet valve is more difficult to visualize (yellow arrow). Ao, aorta; LPV, left pneumatic ventricle; PA, pulmonary artery.
of a normally functioning TAH. Transgastric windows are not useful because the air in the pneumatic pumping chambers will result in significant artifact. Similarly, transthoracic echocardiography is generally not feasible in TAH patients. Electrocardiographic gating during IO-TEE cannot be used for image acquisition because there will be no R wave because both native ventricles are removed entirely. Table 1 presents important steps and considerations for performing IO-TEE during TAH implantation. Pre-cardiopulmonary bypass IO-TEE imaging usually plays a limited role; however, a comprehensive study should be performed to rule out unexpected findings, such as a patent foramen ovale or pulmonary venous abnormality. The venous-to-atrial connections and the atrial
chambers are crucial structures to assess soon after implantation and also at the time of the chest closure. The integrity of junctions of the superior vena cava and inferior vena cava (IVC) to right atrium (RA) and pulmonary veins to left atrium (LA) are essential for maintaining adequate input to the pneumatic pumping chambers of the TAH. They can be kinked or twisted while the outflow conduits are being connected to the aorta and PA at the time of surgery or compressed by sternal apposition during chest closure (Figure 2). The venous structures can also be sucked down by inappropriately high pneumatic pumping chamber vacuum levels. This suck-down phenomenon can be exaggerated when there is concomitant volume depletion. Similarly, the
456
The Journal of Heart and Lung Transplantation, Vol 33, No 4, April 2014
Table 1 Steps Involved When Performing Intra-operative Transesophageal Echocardiography Imaging During Total Artificial Heart Implantation Step Description 1 2
3
4
Pre-cardiopulmonary bypass IO-TEE plays a limited role in TAH implantation; however, a comprehensive study should be performed to rule out unexpected findings such as a patent foramen ovale or pulmonary venous abnormality. While coming off cardiopulmonary bypass support, small amounts of air in the ascending aorta or pulmonary artery are commonly seen. However, a large bolus of air occurring in pulsatile fashion is abnormal and should be communicated to the surgeon immediately to make sure that there is no air leak. Inspect the venous connections, including the IVC and SVC to RA and pulmonary veins to LA junctions, to make sure that they are not distorted. Color and pulsed-wave Doppler flow velocities should be obtained. Adjustment of the left and right pneumatic pumping chambers within the chest may kink or twist these venous entrances. The aorta and pulmonary artery connections should similarly be checked although are much less likely to kink. Inspect the inlet and outlet prosthetic valves and the single-tilting disk mobility of each, along with mean Doppler gradients across them. It is generally not difficult to visualize the inlet valves but can be difficult and requires experience to assess the outlet valves. The outlet valves can be imaged from the upper esophageal window using the aortic arch as the imaging medium. IO-TEE, intra-operative transesophageal echocardiography; IVC, inferior vena cava; LA, left atrium; RA, right atrium; SVC, superior vena cava.
Figure 2 Intra-operative transesophageal echocardiography imaging of the inferior vena cava (IVC) after implantation of a SynCardia (SynCardia Systems Inc, Tucson, AZ) total artificial heart (TAH), taken (A) immediately after device implantation, demonstrating a patent IVC (yellow arrow) with unobstructed flow, and (B) immediately after chest closure, which resulted in shifting of the TAH in the chest cavity causing compression of the IVC (yellow arrow) and obstructed flow causing color aliasing. This subsequently resolved with device repositioning. In a different patient, the right atrium (RA) and left atrium (LA) are shown (C) after TAH implantation immediately after chest closure, demonstrating severe compression of the LA caused by shifting of the TAH in the chest cavity. This compression also resolved with device repositioning.
presence of ascites can distort the IVC-to-RA junction by elevating the diaphragm, and pleural effusions can distort the pulmonary vein-to-LA junctions, resulting in inflow compression and reduced pre-load to the appropriate pneumatic chambers (Figure 2). Next, the inlet valves of the left and right pneumatic pumping chamber are evaluated for proper function, including adequate single-tilting disk excursion with a mild regurgitant washing jet by color-flow imaging (Figure 1). Filling Doppler inflow gradients across the TAH inlet valves can also be measured (see Supplementary Figure 2, available on the jhltonline.org Web site). Although these gradients are significantly influenced by hemodynamic conditions and device settings and function, they may potentially be used as a baseline that can be compared with subsequent follow-up values. Lastly, the ascending aorta and main PA can be imaged from the middle and upper esophageal windows. Visualization of both outlet valves can be difficult in some patients but should be attempted from the upper esophageal window (Figure 1).
Disclosure statement The authors thank Drs Soon J. Park, Lyle D. Joyce, and Richard C. Daly for their contribution to this report. Dr Francisco A. Arabia has performed consulting for SynCardia Inc. None of the other authors has a financial relationship with a commercial entity that has an interest in the subject of the presented manuscript or other conflicts of interest to disclose. There are no other or conflicts of interest or financial relationships to disclose.
Supplementary materials Supplementary figures are available in the online version of this article at jhltonline.org.
References 1. Copeland JG, Smith RG, Arabia FA, Nolan PE, Sethi GK, Tsau PH, et al. Cardiac replacement with a total artificial heart as a bridge to transplantation. N Engl J Med 2004;351:859-67.
Case Anecdotes, Comments and Opinions
457
2. Copeland JG, Copeland H, Gustafson M, Mineburg N, Covington D, Smith RG, et al. Experience with more than 100 total artificial heart implants. J Thoracic Cardiovasc Surgery 2012;143: 727-34.
3. Kirklin JK, Naftel DC, Kormos RL, Stevenson LW, Pagani FD, Miller MA, et al. Fifth INTERMACS annual report: risk factor analysis from more than 6,000 mechanical circulatory support patients. J Heart Lung Transplant 2013;32:141-56.
Use of tissue plasminogen activator to resolve high purge system pressure in a catheter-based ventricular-assist device
50 units/ml heparin (Figure 1). Systemic heparin for a PTT 60 to 80 seconds was continued. No bleeding complications occurred during or after the tPA infusion. The purge pressure subsequently remained at goal for 6 days, at which time the patient received a permanent LVAD. No macroscopic defects in the Impella purge line or motor/pump housing were observed at explant, and the device was returned to the manufacturer for analysis. We used thrombolytic therapy to salvage an Impella device and allow extended therapy, without pump exchange. Our decision to use tPA was prompted by the temporal association between the increased purge pressure and removal of heparin, and its resolution, although temporary, with reinstitution of heparin. The presumption was that fibrin build-up on the purge system seal and/or motor shaft contributed to partial occlusion of the purge flow outlet and to increased motor drag causing increasing motor current. We had observed similar behavior in the past with extended de-heparinization of the purge solution. The decision to attempt this approach rather than exchanging the Impella device was made because the latter would have required reopening the sternum in a patient with: (1) four prior sternotomies and a fifth pending for long-term VAD reimplantation; and (2) prior sternal wound infection requiring flap coverage. In addition, although the Impella is a temporary device, the cost, which is approximately $30,000 at our institution, is not trivial. Finally, the patient did not exhibit hemodynamic instability or hemolysis, either of which would have prompted urgent exchange. Tissue plasminogen activator initiates local fibrinolysis by binding to fibrin in a clot and converting plasminogen to plasmin. Cathflo (Genentech, San Francisco, CA) was the tPA of choice due to its fibrin-specific mechanism of action with limited systemic exposure. We selected 2 mg tPA empirically based on catheter-clearing doses. Our initial intention had been to bolus into the catheter; however, the high resistance of the tubing precluded this. Despite the low dose and extended delivery time, resolution of high pressures was obtained. A higher dose might have resulted in more rapid resolution, but we were wary of increasing bleeding risk given the unknown probability of success. No bleeding occurred with the dose we used. The tPA was diluted in a normal saline solution. In postintervention discussions with Abiomed (personal communication), we were cautioned that instilling normal saline through the purge line might increase the risk of motor corrosion. Fortunately, the pump continued to function normally for 6 days after the intervention. In hindsight, sterile water might have been a better choice. In conclusion, we were able to successfully obtain resolution of the high purge pressures with a catheter-clearing tPA dose, without adverse effects. This therapy may be an alternative to
Erik N. Sorensen, PhD,a Carla Williams, PharmD,b and Ali Tabatabai, MDc From the Departments of aClinical Engineering; bPharmacy, and the cMedicine, University of Maryland Medical Center, Baltimore, Maryland.
A 54-year-old man with a HeartMate II (Thoratec Corp, Pleasanton, CA) left ventricular-assist device (LVAD) placed 7 months prior underwent explantation for chronic bacteremia and pump pocket infection. As a temporizing measure, an Impella 5.0 LD (Abiomed, Danvers, MA) was inserted into the left ventricle (LV) through a remnant of the HeartMate II outflow graft. The Impella’s purge system was primed with 5% dextrose and unfractionated heparin (20 units/ml). Purge pressures of 418 to 652 mm Hg (normal reference range, 300–700 mm Hg) were observed at a purge flow rate of 25 ml/h (Figure 1). Because of bleeding, heparin was stopped on arrival in the intensive care unit. After 6 hours, the purge pressure was 4 700 mm Hg. A flow rate reduction to 5 ml/h yielded pressures of 650 to 850 mm Hg. With bleeding subsided, 50 units/ml heparin was added to the purge solution, and a systemic infusion for a partial thromboplastin time (PTT) goal of 45 to 55 seconds commenced. With these changes, the purge pressure decreased to normal levels within 6 hours at an infusion rate of 1 to 3 ml/h. However, in o 24 hours, a purge pressure 4 700 mm Hg required maintenance of 5% dextrose at a flow rate of 1 ml/h. A transient normalization was followed by a recurrence of intermittent high pressures. On the fourth postoperative day, the PTT goal was increased to 60 to 80 seconds. By evening, however, we were unable to maintain pressures o 700 mm Hg. Increasing the heparin concentration to 200 units/ml and pausing the infusion for pressure 4 900 mm Hg failed to help. Peak motor current had also risen from 0.75 to 0.76 A to 0.77 to 0.78 A, concerning for increased drag. Because the goal was a 10- to- 14-day period of quiescent blood cultures, followed by implantation of a permanent LVAD, we undertook a novel salvage approach. We substituted 2 mg tissue plasminogen activator (tPA) diluted in 50 ml normal saline for the heparinized purge solution. Continuing high pressures limited the initial infusion rate to 1 ml/h. After 16 hours, the purge pressure rapidly dropped to o 300 mm Hg (Figure 1). The infusion rate was able to be increased to 15 ml/h and was complete at 23 hours. At this point, heparinized dextrose was reintroduced. Stable purge pressures of 350 to 450 mm Hg were achieved with 25 ml/h of 5% dextrose and
The Journal of Heart and Lung Transplantation, Vol 33, No 4, April 2014
these patients survived,3 the patient described in this study will be followed by a medical geneticist. SVT is the most common arrhythmia with cardiac tumors in the neonatal period, and rhabdomyoma can be associated with ventricular pre-excitation.4 Evolution of inconsistent arrhythmia types suggests that the patient’s re-entrant tachycardia was not mediated by an embryonic accessory pathway. Destruction of the conduction system has been described in diffuse rhabdomyomatosis,5 and likely explains the unusual progression of this patient’s arrhythmias. Analogous alternate routes of conduction have been described in glycogen-storage disease, whereby diffuse myocardial infiltration may connect atrial and ventricular myocardium, resulting in pre-excitation. The differential diagnosis for infantile HCM includes primary sarcomeric defects, infiltrative cardiomyopathies with diagnosable biochemical perturbations, and syndromic cardiomyopathies. However, the presence of refractory arrhythmias and fluctuating wall thickness changes in a patient with diffuse ventricular thickening may indicate an alternative diagnoses, such as diffuse rhabdomyomatosis. This patient’s clinical course was atypical for sarcomeric HCM. Her early, severe and rapid progression to heart failure, recalcitrant SVT, and evolving arrhythmias were clues to a diagnosis other than HCM, which may have changed our approach to management. If diffuse rhabdomyomatosis was suspected and confirmed by biopsy, an electrophysiology study with the potential for decompensation would not have been pursued
Intraoperative transesophageal echocardiographic guidance of total artificial heart implantation Nowell M. Fine, MD,a Radha S. Gopalan, MD,b Francisco A. Arabia, MD,c Sudhir S. Kushwaha, MD,a and Krishnaswamy Chandrasekaran, MDa,b From the aDivision of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota; b Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Scottsdale, Arizona; and the cDivision of Cardiovascular Surgery, Department of Surgery, Cedars-Sinai Medical Center, Los Angeles, California
For advanced heart failure patients who are candidates for mechanical circulatory support (MCS) but are at increased risk for poor outcomes after left ventricular assist device implantation, the total artificial heart (TAH) has become an important therapeutic option.1–3 The SynCardia TAH (SynCardia Systems Inc, Tucson, AZ) became the first TAH approved for use in the United States in 2004, and the number TAH-implanting centers is growing.2 Centers that perform echocardiography on MCS-supported patients have endeavored to characterize the signs of abnormal device function to deliver useful information in a timely manner. However, little is known about the role of intraoperative (IO) transesophageal echocardiography (TEE) during TAH implantation. In this report, we describe the role of IO-TEE during TAH implantation and discuss the utility and limitations of IO-TEE guidance.
aggressively. Given the natural history of diffuse rhabdomyomatosis, ablation could have been avoided and transplantation may have been pursued earlier, which is important because early transplant outcomes are directly related to the need for extracorporeal membrane oxygen (ECMO) support before transplantation.
Disclosure statement The authors have no conflicts of interest to disclose. We thank Lawrence Merritt, MD, for valuable input.
References 1. Coates TL, McGahan JP. Fetal cardiac rhabdomyomas presenting as diffuse myocardial thickening. J Ultrasound Med 1994;13:813-6. 2. Shrivastava S, Jacks JJ, White RS, et al. Diffuse rhabdomyomatosis of the heart. Arch Pathol Lab Med 1977;101:78-80. 3. Verhaaren HA, Venaaker O, De Wolf D, et al. Left ventricular outflow obstruction in rhabdomyoma of infancy: meta-analysis of the literature. J Pediatr 2003;143:258-63. 4. Gotlieb AI, Chan M, Palmer WH, et al. Ventricular preexcitation syndrome. Accessory left atrioventricular connection and rhabdomyomatous myocardial fibers. Arch Pathol Lab Med 1977;101:486-9. 5. Mandke JV, Kinare SG, Phatak AM. Congenital diffuse rhabdomyomatosis of the heart with biventricular outflow obstruction. Indian Heart J 1992;44:187-8.
Echocardiographic imaging of the TAH requires a thorough understanding of the device and its components, as well as the implantation procedure. During implantation, the ventricular portion of the recipient heart is excised, leaving only a rim of ventricular myocardium. The atria and their respective venous connections are left intact and form the atrial chambers of the TAH. The aortic and pulmonary roots are excised just above the aortic and pulmonary valves, leaving the distal ascending aorta and distal main pulmonary artery (PA) intact. The SynCardia TAH unit has 2 separate pneumatic pumping chambers, representing the left and right ventricles (the TAH components are illustrated in Supplementary Figure 1, available on the jhltonline.org Web site). The TAH also contains four Medtronic-Hall single-tilting disk valve prostheses (Medtronic-Hall, Medtronic, Minneapolis, MN) in each valvular position. Each pneumatic pumping chamber has an inlet valve representing the mitral and tricuspid valve and an outlet valve representing the aortic and pulmonary valve. The pneumatic pumping chambers are sutured to the rim of the ventricular myocardium adjoining the atrioven tricular groove. The outlet valves are connected to the retained native ascending aorta and PA, respectively, by a conduit. The diaphragms within each pumping chamber are pneumatically driven by an external driver that is connected by left and right drivelines tunneled extraperitoneally through the abdominal wall. The retention of both atria provide for an excellent imaging window of the TAH from the middle and upper esophageal IO-TEE imaging windows. Figure 1 shows IO-TEE images
Case Anecdotes, Comments and Opinions
455
Figure 1 Intra-operative transesophageal echocardiography from the midesophageal imaging window after implantation of the SynCardia (SynCardia Systems Inc, Tucson, AZ) total artificial heart demonstrates an intact right atrium (RA) and left atrium (LA), with prosthetic right (RIV) and left (LIV) single-tilting disk inlet valves (yellow arrows) in the (A) open and (B) closed positions. The prosthetic valves are anchored to ventricular rims and lead into their respective pneumatic pumping chambers (ventricles). Acoustic artifact from the pneumatic pumping chambers and prosthetic inlet valves obscure visualization of structures distal to the ventricular rims. The prosthetic right singletilting disk inlet valve is shown in the (C) open position with color inflow into the right pneumatic ventricle (RPV) and in the (D) closed position. A mild regurgitant washing jet (yellow arrow) in the closed position is present with (D) normal prosthetic valve function. (E) The prosthetic left single-tilting disk outlet valve is shown (yellow arrow) in the (left image) short-axis and (right image) long-axis views. (F) The prosthetic right single-tilting disk outlet valve is more difficult to visualize (yellow arrow). Ao, aorta; LPV, left pneumatic ventricle; PA, pulmonary artery.
of a normally functioning TAH. Transgastric windows are not useful because the air in the pneumatic pumping chambers will result in significant artifact. Similarly, transthoracic echocardiography is generally not feasible in TAH patients. Electrocardiographic gating during IO-TEE cannot be used for image acquisition because there will be no R wave because both native ventricles are removed entirely. Table 1 presents important steps and considerations for performing IO-TEE during TAH implantation. Pre-cardiopulmonary bypass IO-TEE imaging usually plays a limited role; however, a comprehensive study should be performed to rule out unexpected findings, such as a patent foramen ovale or pulmonary venous abnormality. The venous-to-atrial connections and the atrial
chambers are crucial structures to assess soon after implantation and also at the time of the chest closure. The integrity of junctions of the superior vena cava and inferior vena cava (IVC) to right atrium (RA) and pulmonary veins to left atrium (LA) are essential for maintaining adequate input to the pneumatic pumping chambers of the TAH. They can be kinked or twisted while the outflow conduits are being connected to the aorta and PA at the time of surgery or compressed by sternal apposition during chest closure (Figure 2). The venous structures can also be sucked down by inappropriately high pneumatic pumping chamber vacuum levels. This suck-down phenomenon can be exaggerated when there is concomitant volume depletion. Similarly, the
456
The Journal of Heart and Lung Transplantation, Vol 33, No 4, April 2014
Table 1 Steps Involved When Performing Intra-operative Transesophageal Echocardiography Imaging During Total Artificial Heart Implantation Step Description 1 2
3
4
Pre-cardiopulmonary bypass IO-TEE plays a limited role in TAH implantation; however, a comprehensive study should be performed to rule out unexpected findings such as a patent foramen ovale or pulmonary venous abnormality. While coming off cardiopulmonary bypass support, small amounts of air in the ascending aorta or pulmonary artery are commonly seen. However, a large bolus of air occurring in pulsatile fashion is abnormal and should be communicated to the surgeon immediately to make sure that there is no air leak. Inspect the venous connections, including the IVC and SVC to RA and pulmonary veins to LA junctions, to make sure that they are not distorted. Color and pulsed-wave Doppler flow velocities should be obtained. Adjustment of the left and right pneumatic pumping chambers within the chest may kink or twist these venous entrances. The aorta and pulmonary artery connections should similarly be checked although are much less likely to kink. Inspect the inlet and outlet prosthetic valves and the single-tilting disk mobility of each, along with mean Doppler gradients across them. It is generally not difficult to visualize the inlet valves but can be difficult and requires experience to assess the outlet valves. The outlet valves can be imaged from the upper esophageal window using the aortic arch as the imaging medium. IO-TEE, intra-operative transesophageal echocardiography; IVC, inferior vena cava; LA, left atrium; RA, right atrium; SVC, superior vena cava.
Figure 2 Intra-operative transesophageal echocardiography imaging of the inferior vena cava (IVC) after implantation of a SynCardia (SynCardia Systems Inc, Tucson, AZ) total artificial heart (TAH), taken (A) immediately after device implantation, demonstrating a patent IVC (yellow arrow) with unobstructed flow, and (B) immediately after chest closure, which resulted in shifting of the TAH in the chest cavity causing compression of the IVC (yellow arrow) and obstructed flow causing color aliasing. This subsequently resolved with device repositioning. In a different patient, the right atrium (RA) and left atrium (LA) are shown (C) after TAH implantation immediately after chest closure, demonstrating severe compression of the LA caused by shifting of the TAH in the chest cavity. This compression also resolved with device repositioning.
presence of ascites can distort the IVC-to-RA junction by elevating the diaphragm, and pleural effusions can distort the pulmonary vein-to-LA junctions, resulting in inflow compression and reduced pre-load to the appropriate pneumatic chambers (Figure 2). Next, the inlet valves of the left and right pneumatic pumping chamber are evaluated for proper function, including adequate single-tilting disk excursion with a mild regurgitant washing jet by color-flow imaging (Figure 1). Filling Doppler inflow gradients across the TAH inlet valves can also be measured (see Supplementary Figure 2, available on the jhltonline.org Web site). Although these gradients are significantly influenced by hemodynamic conditions and device settings and function, they may potentially be used as a baseline that can be compared with subsequent follow-up values. Lastly, the ascending aorta and main PA can be imaged from the middle and upper esophageal windows. Visualization of both outlet valves can be difficult in some patients but should be attempted from the upper esophageal window (Figure 1).
Disclosure statement The authors thank Drs Soon J. Park, Lyle D. Joyce, and Richard C. Daly for their contribution to this report. Dr Francisco A. Arabia has performed consulting for SynCardia Inc. None of the other authors has a financial relationship with a commercial entity that has an interest in the subject of the presented manuscript or other conflicts of interest to disclose. There are no other or conflicts of interest or financial relationships to disclose.
Supplementary materials Supplementary figures are available in the online version of this article at jhltonline.org.
References 1. Copeland JG, Smith RG, Arabia FA, Nolan PE, Sethi GK, Tsau PH, et al. Cardiac replacement with a total artificial heart as a bridge to transplantation. N Engl J Med 2004;351:859-67.
Case Anecdotes, Comments and Opinions
457
2. Copeland JG, Copeland H, Gustafson M, Mineburg N, Covington D, Smith RG, et al. Experience with more than 100 total artificial heart implants. J Thoracic Cardiovasc Surgery 2012;143: 727-34.
3. Kirklin JK, Naftel DC, Kormos RL, Stevenson LW, Pagani FD, Miller MA, et al. Fifth INTERMACS annual report: risk factor analysis from more than 6,000 mechanical circulatory support patients. J Heart Lung Transplant 2013;32:141-56.
Use of tissue plasminogen activator to resolve high purge system pressure in a catheter-based ventricular-assist device
50 units/ml heparin (Figure 1). Systemic heparin for a PTT 60 to 80 seconds was continued. No bleeding complications occurred during or after the tPA infusion. The purge pressure subsequently remained at goal for 6 days, at which time the patient received a permanent LVAD. No macroscopic defects in the Impella purge line or motor/pump housing were observed at explant, and the device was returned to the manufacturer for analysis. We used thrombolytic therapy to salvage an Impella device and allow extended therapy, without pump exchange. Our decision to use tPA was prompted by the temporal association between the increased purge pressure and removal of heparin, and its resolution, although temporary, with reinstitution of heparin. The presumption was that fibrin build-up on the purge system seal and/or motor shaft contributed to partial occlusion of the purge flow outlet and to increased motor drag causing increasing motor current. We had observed similar behavior in the past with extended de-heparinization of the purge solution. The decision to attempt this approach rather than exchanging the Impella device was made because the latter would have required reopening the sternum in a patient with: (1) four prior sternotomies and a fifth pending for long-term VAD reimplantation; and (2) prior sternal wound infection requiring flap coverage. In addition, although the Impella is a temporary device, the cost, which is approximately $30,000 at our institution, is not trivial. Finally, the patient did not exhibit hemodynamic instability or hemolysis, either of which would have prompted urgent exchange. Tissue plasminogen activator initiates local fibrinolysis by binding to fibrin in a clot and converting plasminogen to plasmin. Cathflo (Genentech, San Francisco, CA) was the tPA of choice due to its fibrin-specific mechanism of action with limited systemic exposure. We selected 2 mg tPA empirically based on catheter-clearing doses. Our initial intention had been to bolus into the catheter; however, the high resistance of the tubing precluded this. Despite the low dose and extended delivery time, resolution of high pressures was obtained. A higher dose might have resulted in more rapid resolution, but we were wary of increasing bleeding risk given the unknown probability of success. No bleeding occurred with the dose we used. The tPA was diluted in a normal saline solution. In postintervention discussions with Abiomed (personal communication), we were cautioned that instilling normal saline through the purge line might increase the risk of motor corrosion. Fortunately, the pump continued to function normally for 6 days after the intervention. In hindsight, sterile water might have been a better choice. In conclusion, we were able to successfully obtain resolution of the high purge pressures with a catheter-clearing tPA dose, without adverse effects. This therapy may be an alternative to
Erik N. Sorensen, PhD,a Carla Williams, PharmD,b and Ali Tabatabai, MDc From the Departments of aClinical Engineering; bPharmacy, and the cMedicine, University of Maryland Medical Center, Baltimore, Maryland.
A 54-year-old man with a HeartMate II (Thoratec Corp, Pleasanton, CA) left ventricular-assist device (LVAD) placed 7 months prior underwent explantation for chronic bacteremia and pump pocket infection. As a temporizing measure, an Impella 5.0 LD (Abiomed, Danvers, MA) was inserted into the left ventricle (LV) through a remnant of the HeartMate II outflow graft. The Impella’s purge system was primed with 5% dextrose and unfractionated heparin (20 units/ml). Purge pressures of 418 to 652 mm Hg (normal reference range, 300–700 mm Hg) were observed at a purge flow rate of 25 ml/h (Figure 1). Because of bleeding, heparin was stopped on arrival in the intensive care unit. After 6 hours, the purge pressure was 4 700 mm Hg. A flow rate reduction to 5 ml/h yielded pressures of 650 to 850 mm Hg. With bleeding subsided, 50 units/ml heparin was added to the purge solution, and a systemic infusion for a partial thromboplastin time (PTT) goal of 45 to 55 seconds commenced. With these changes, the purge pressure decreased to normal levels within 6 hours at an infusion rate of 1 to 3 ml/h. However, in o 24 hours, a purge pressure 4 700 mm Hg required maintenance of 5% dextrose at a flow rate of 1 ml/h. A transient normalization was followed by a recurrence of intermittent high pressures. On the fourth postoperative day, the PTT goal was increased to 60 to 80 seconds. By evening, however, we were unable to maintain pressures o 700 mm Hg. Increasing the heparin concentration to 200 units/ml and pausing the infusion for pressure 4 900 mm Hg failed to help. Peak motor current had also risen from 0.75 to 0.76 A to 0.77 to 0.78 A, concerning for increased drag. Because the goal was a 10- to- 14-day period of quiescent blood cultures, followed by implantation of a permanent LVAD, we undertook a novel salvage approach. We substituted 2 mg tissue plasminogen activator (tPA) diluted in 50 ml normal saline for the heparinized purge solution. Continuing high pressures limited the initial infusion rate to 1 ml/h. After 16 hours, the purge pressure rapidly dropped to o 300 mm Hg (Figure 1). The infusion rate was able to be increased to 15 ml/h and was complete at 23 hours. At this point, heparinized dextrose was reintroduced. Stable purge pressures of 350 to 450 mm Hg were achieved with 25 ml/h of 5% dextrose and
