Ventricular assist devices (VAD) in Fontan Patients – Why, Who and When: A Surgical and Heart Failure Cardiologist's Perspective

Why VAD in patients with Fontan?

Every long-term study of late outcomes after Fontan palliation has demonstrated the same fact – a disconcertingly large proportion of individuals will not survive. While the exact risk varies depending on the cohort analyzed, in nearly all studies, 10-20% of individuals with Fontan palliation have not survived with the Fontan intact after 20 years.^1-5 For years, the ultimate solution to failing Fontan physiology has been heart transplant. While the results of heart transplant in individuals with Fontan physiology have improved, their 1-year survival remains lower on average than all other heart diseases.⁶ The reasons for this are not completely clear, but widely shared anecdotal experience and emerging data suggest late referral and poor patient status at the time of transplant contribute. In other heart disease, VAD placement has become a common approach to allow rehabilitation, improvement of physical status, better extracardiac end-organ function, and overall improved candidacy for heart transplantation. Although a more physiologically complex scenario compared to most acquired heart diseases, VADs could achieve the same status improvement in Fontan patients. Many centers are beginning to use them for this purpose to improve overall Fontan survival both pre- and post-transplant and in some cases, as chronic therapy.

Who should be considered for a Fontan VAD?

Fontan circulatory failure may occur in many ways. In addition to systolic and diastolic ventricular heart failure, the Fontan pathway itself may fail ("right heart failure without a right heart"), or lymphatic syndromes such as protein-losing enteropathy, abnormal pulmonary vasculature, or Fontan-specific extra-cardiac organ failure as in Fontan-associated liver disease, may develop. These do not occur in isolation, and may develop insidiously over the years, increasing the complexity of patient treatment.

So when should a VAD be considered? In a study by the Advanced Cardiac Therapies Improving Outcomes Network (ACTION),⁷ it was noted that the use of a systemic ventricle VAD in single ventricles can be successful. Despite being a critically ill cohort with 81% of 45 reported Fontan patients having INTERMACS profile 1 or 2 at 1 year from VAD placement, 70% had survived to transplant and another 9% were alive on a device. Systemic ventricular dysfunction was present in the majority of these patients, indicating that depressed systolic function in a Fontan can be supported by VAD and should be considered an indication. The role of VAD therapy for ventricular diastolic dysfunction is less clear, but there is evidence both in the ACTION experience and elsewhere that optimized VAD therapy can also lower ventricular diastolic pressure and thereby lower Fontan pathway pressure.⁸ Thus, VADs may improve systolic or mixed systolic and diastolic ventricular dysfunction in Fontan physiology. The efficacy of VAD to improve other etiologies of Fontan circulatory failure is unknown. Although VAD support to the Fontan pathway (essentially adding a pump to the pumpless pulmonary circulation) has been described,⁹ it is technically challenging and is currently experimental. As experience grows, VADs may allow Fontan patients to become better physical candidates for transplant regardless of Fontan failure etiology. Frailty in patients with Fontan is of increasing focus in their clinical care. In some cases, VADs may allow rehabilitation and improvement of the frail state, but more specific research and experience is necessary.

VADs in Fontan patients – A Surgeon's Perspective of Technical Aspects

VAD implantation in a single ventricle does not vary much from a more straightforward case. Unlike standard LVAD placement, in Fontan VAD often the heart is arrested, since preserving the right heart (sub-pulmonary ventricle) is not an issue. If Damus-Kaye-Stansel connections are present, they may be thin walled and difficult to deal with; so often a graft is sewn to the innominate or subclavian artery even distal to a previous shunt location, ensuring no critical innominate artery stenosis is present. At the end of the case, this shunt may be clipped just distal to the anastomosis and kept long so it may be used at transplantation. This is especially helpful if the patient is undergoing en bloc heart-liver transplantation or will need arch reconstruction at transplant. If the aorta is particularly worrisome to place a side biting clamp, one can consider anastomosis of the outflow graft to the innominate artery especially easy, if there are bilateral superior vena cava. One may also cannulate the outflow graft at transplantation to establish bypass.

Many believe Fontan VADs should be placed in the ventricle and do not feel atrial placed devices are as effective for long-term or chronic support. The ventriculotomy is a bit more anterior in a systemic right ventricle (RV). Frequently used is a "cut then sew" technique for the apical cuff in a systemic RV to ensure easy exploration of the ventricle and removal of any possible muscle bundles that could impede inflow. Many surgeons consider creating or enlarging a fenestration, even if challenging, given the post-operative physiologic benefit to Fontan circulation a fenestration may provide. Creation of the fenestration can be challenging if the graft or patch is calcified, or the atrium is particularly thick. Esmark strips are applied loosely around inferior and superior vena cava as well as the pulmonary arteries and aorta if circumferentially dissected out. If the aorta is difficult to circumferentially dissect out and the patient is quite sick, one can just fibrillate the heart to achieve fenestration. Often a pillow made of a sheet of GelFoam® is left sandwiched between two thin membranes of GoreTex. This may help with post-op discomfort especially in smaller patients. Also, in Fontan patients in particular because of the amount of chest wall collaterals, it helps decrease the risk of bleeding from the device causing chest wall trauma during early ambulation/mobilization. This pocket also makes it easy to remove the device at time of transplantation. Frequently, intracorporeal VADs are placed in the extra pericardial space inferior to the left lower lobe and in smaller patients' posterior to the diaphragm in the sulcus where the diaphragm and ribs meet. All of these small adaptations make initiating cardiopulmonary bypass at the time of the transplant quite efficient. Spending the time in the operating room to ensure excellent hemostasis and chest closure with the attainable goal of no hemostatic blood products given in the intensive care unit is essential in maximizing lung function and extubation in the first 24 hours.

References

1. Pundi KN, Johnson JN, Dearani JA, et al. 40-year follow-up after the fontan operation: long-term outcomes of 1,052 patients. J Am Coll Cardiol 2015;66:1700-10.
2. Downing TE, Allen KY, Glatz AC, et al. Long-term survival after the Fontan operation: twenty years of experience at a single center. J Thorac Cardiovasc Surg 2017:154:243-53.
3. Moon J, Shen L, Likosky DS, et al. Relationship of ventricular morphology and atrioventricular valve function to long-term outcomes following Fontan procedures. J Am Coll Cardiol 2020;76: 419-31.
4. Daley M, du Plessis K, Zannino D, et al. Reintervention and survival in 1428 patients in the Australian and New Zealand Fontan Registry. Heart 2020;106:751-57.
5. Mery CM, De Leon LE, Trujillo-Diaz D, et al. Contemporary outcomes of the Fontan operation: a large single-institution cohort. Ann Thor Surg 2019;108:1439-46.
6. Simpson KE, Pruitt E, Kirklin JK, et al. Fontan patient survival after pediatric heart transplant has improved in the current era. Ann Thor Surg 2017;103:1315-20.
7. Cedars A, Kutty S, Danford D, et al. Systemic ventricular assist device support in Fontan patients: a report by ACTION. J Heart Lung Transplant 2021;40:368-76.
8. Chau P, Lim HM, Schumacher KR, Grifka RG, Peng DM. Use of a hemodynamic ramp study to optimize continuous-flow ventricular assist device in a Fontan patient. ASAIO J 2019;65:e47-e49.
9. Moosmann J, Dittrich S, Purbojo A, Cesnjevar R. RVAD implantation in a Fontan patient with protein-losing enteropathy as a bridge to transplant: Prêtre modification. J Card Surg 2020;35:1721-24.

Clinical Topics: Cardiac Surgery, Congenital Heart Disease and Pediatric Cardiology, Geriatric Cardiology, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Cardiac Surgery and CHD and Pediatrics, Cardiac Surgery and Heart Failure, Congenital Heart Disease, CHD and Pediatrics and Interventions, CHD and Pediatrics and Prevention, Acute Heart Failure, Heart Transplant, Mechanical Circulatory Support

Keywords: Fontan Procedure, Heart-Assist Devices, Vena Cava, Superior, Heart Ventricles, Pulmonary Circulation, Pulmonary Artery, Airway Extubation, Blood Pressure, Brachiocephalic Trunk, Cardiopulmonary Bypass, Constriction, Pathologic, Critical Illness, Diaphragm, Early Ambulation, Frail Elderly, Gelatin Sponge, Absorbable, Liver Transplantation, Operating Rooms, Protein-Losing Enteropathies, Subclavian Artery, Thoracic Wall, Heart Transplantation, Heart Failure, Ventricular Dysfunction, Intensive Care Units, Pericardium, Shock, Heart Diseases, Liver Diseases, Hemostasis, Referral and Consultation, Surgeons, Polytetrafluoroethylene, Aorta

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