In the case of rejection and heart dysfunction, rescuing heterotopic heart transplantation (HHT) patients might be challenging because of high panel reactive antibodies (PRA) and availability of donor hearts. In this case, for the first time, the SynCardia 50cc total artificial heart (TAH) (SynCardia Systems, LLC, Tucson, AZ) was used as a rescue therapy on a HHT patient. Patient was able to undergo successful orthotopic heart transplantation six months after being placed on TAH.
A Hispanic, 41-year-old man with childhood cardiomyopathy had a HHT in 1992 and subsequently developed transplant vasculopathy and allograft dysfunction. A myocardial infarction in 2013 resulted in 100% occlusion of the transplanted heart’s left anterior descending artery. The patient had elevated PRAs: Class I (56%) and Class II (97%). In 2016, despite continuous milrinone therapy and multiple hospitalizations, patient symptoms became worse and included shortness of breath, lower extremity swelling, abdominal distention, anorexia, and weight loss. After admission to an outside facility in May 2016, a right heart catheterization was done (see Figure 1, Supplemental Digital Content, http://links.lww.com/ASAIO/A391).
Electrocardiogram (EKG) findings included atrial fibrillation with a rapid ventricular response with aberrantly conducted or premature ventricular complexes; right axis deviation, incomplete right bundle branch block, plus right ventricular hypertrophy with a pulmonary disease pattern. Transthoracic echocardiogram imaging of the donor heart revealed a biventricular dilatation and severe systolic dysfunction (see Figure 1, Supplemental Digital Content, http://links.lww.com/ASAIO/A391), with the left ventricular ejection fraction estimated to be less than 20%. Biatrial enlargement and moderate mitral and tricuspid regurgitation were detected.
A Computed tomography (CT) of the chest without contrast displayed the transplanted heart situated in the right chest, causing narrowing and compression of the middle lobe of the right lung. The native heart was enlarged with a cardiothoracic ratio of 16.7/27.8 cm.
An intra-aortic balloon pump (IABP) was implanted during the May 2016 admission in an attempt to provide cardiac support. Dialysis was also done at this outside hospital.
Patient was transferred to our center in June 2016, and after desensitization, patient was placed on the transplantation list with an 1A status. His hemodynamic condition deteriorated on IABP support because of urinary tract infection, which contributed to severe cardiogenic shock. Emergent venoarterial extracorporeal membrane oxygenation (VA-ECMO) was completed in June along with an IABP exchange. The patient was presented at the Medical Review Board (MRB) and approved for biventricular support. He underwent TAH placement after being on VA-ECMO for 7 days. The SynCardia 50cc investigational device was chosen because of its small size; it was hypothesized that it would be a viable option as the existing donor heart consumed considerable space in the mediastinum.
The patient was placed on cardiopulmonary bypass using bicaval venous and standard aortic cannulation. After the cava were snared and the aorta was cross-clamped, the native ventricles were removed. Dissection of the donor heart and the surrounding fibrous tissue was avoided because of extreme risk of lung injury with massive bleeding and complex air leaks. Next, the coronary sinus was ligated, and the cut edges of both atria were sutured to the attachment atrial rings—left first, then the right one. Next, the outflow connector grafts were sutured to the great vessels. Finally, both ventricular pumps were brought into the field, and their drivelines were externalized through the abdominal wall. The left pump was attached first, followed by the right. The heart was filled and the deairing process took place before weaning from cardiopulmonary bypass. With the TAH in place, alongside the donor heart in situ (Figure 1), functional testing was initiated. The patient became hypotensive and transesophageal echocardiography showed retrograde flow across the aortic valve and pulmonary valve, causing blood pooling and biventricular enlargement of the donor heart. The donor aorta and pulmonary artery (PA) were then clamped (Figure 2) and hemodynamics radically improved. At this pivotal juncture, we debated between two options: total donor heart exclusion versus partial donor heart exclusion. Total exclusion requires explanting the TAH in order to close the atrial anastomoses after obliterating the donor PA and aorta. This option would require a longer aortic cross-clamp time and longer pump time, resulting in an increased potential for coagulopathy and other complications. Partial exclusion leaves both the atrial anastomosis open and the TAH in place; only the donor PA and aorta are transected. However, with the left atrial anastomosis in place, blood may pool at the site of the anastomosis, posing a greater chance of thrombosis and/or embolization. Because anticoagulation therapy is indicated after a TAH implantation, we decided this would mitigate the risk of thrombosis or embolization. Thus, partial exclusion (Figure 3) of the donor heart was chosen as the best course of action at this time.
Delayed sternal closure was performed in order to correct coagulopathy before definitive chest closure. During his postoperative course, the patient suffered a minor stroke from which he completely recovered. After rehabilitation and with approval from the MRB, patient was listed for heart and kidney transplantation. At this time, a CT scan was obtained as part of the traditional standard-of-care testing done before transplant (Figure 4).
The patient was on TAH support for six months. A new donor heart and kidney became available in January 2017, and the patient underwent a successful orthotopic heart and kidney transplantation at that time. The procedure was done in standard bicaval anastomosis fashion after removing TAH. There was no thrombi detected or observed in the donor heart on visual exploration. Again, the donor heart from the HHT was left in place, but the atrial anastomosis was closed between that heart and the atrium of the new donor heart with pericardial patch. After transplantation and rehabilitation, the patient continues to do well and does not require dialysis.
With the advancement of mechanical circulatory support and immunosuppression therapy, HHT is becoming rare in this era.1 Because there is a narrow indication range for this procedure, the population of HHT patients is small.2 However, despite the small size of the population, or perhaps because of it, there is little reliable or evidence-based reports on how to treat this unique population once the donor heart starts to fail.
Heterotopic heart transplantation patients are similar to those who have undergone a previous orthotropic heart transplant and suffer chronic rejection. Both populations typically have high PRAs and biventricular failure, which prevents them from being eligible for an immediate heart transplantation and limits mechanical circulatory support options, respectively.3 Published data does not support the use of ECMO as a bridge to transplantation (BTT) therapy in patients with previous heart transplantations.4 Instead, prolonged support with implantable biventricular devices for chronic graft dysfunction is recommended.5 In the case presented herein, VA-ECMO was placed as a bridge to decision therapy, and it successfully supported the patient and allowed him to recover from most of end organ damages, except the kidney, because he remained dialysis dependent. Once stable, we were able to proceed with the TAH procedure. To our knowledge, this is the first reported case of an HHT patient receiving SynCardia TAH as a BTT therapy with a successful transplantation outcome.
This unique case provides several lessons and key concepts. Leaving the donor heart from the HHT in situ prevents the need for long and tedious extensive dissection around the right lung; thereby reducing the potential risk of lung parenchymal injury, massive bleeding, and complex air leaks. The need for donor heart exclusion from HHT should be done as total exclusion at the time of the TAH implantation. Although our case report shows that a partial exclusion can be done, we believe that in retrospect, a total exclusion should be done because it may reduce the possibility for thrombosis and embolism.
We believe the SynCardia 50cc-TAH, which is a smaller version with extensive use in pediatric population,6 is a viable option for HHT patients as a BTT therapy. Patients with anatomic constraints because of the limited mediastinum space available, also routinely have extensive scar tissue present at the time of the reoperation. The procedure reported herein provides a viable treatment alternative.
1. Flécher E, Fouquet O, Ruggieri VG, Chabanne C, Lelong B, Leguerrier A. Heterotopic heart transplantation
: Where do we stand? Eur J Cardiothorac Surg 2013.44: 201–206
2. Nakatani T, Frazier OH, Lammermeier DE, Macris MP, Radovancevic B. Heterotopic heart transplantation
: A reliable option for a select group of high-risk patients. J Heart Transplant
3. Kalya A, Jaroszewski D, Pajaro O, et al. Role of total artificial heart
in the management of heart transplant
rejection and retransplantation: case report and review. Clin Transplant
4. Khan MS, Mery CM, Zafar F, et al. Is mechanically bridging patients with a failing cardiac graft to retransplantation an effective therapy? Analysis of the United Network of Organ Sharing database. J Heart Lung Transplant
5. Tenderich G, Koerner MM, Stuettgen B, et al. Mechanical circulatory support after orthotopic heart transplantation. Int J Artif Organs 1998.21: 414–416
6. Wells D, Villa CR, Simón Morales DL. The 50/50 cc Total Artificial Heart
Trial: Extending the benefits of the total artificial heart
to underserved populations. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu 2017.20: 16–19