Long-term heart transplant outcomes after lowering fixed pulmonary hypertension using left ventricular assist devices

Heart transplantation: focus on donor recovery strategies, left ventricular assist devices, and novel therapies

Heart transplantation is advocated in selected patients with advanced heart failure in the absence of contraindications. Principal challenges in heart transplantation centre around an insufficient and underutilized donor organ pool, the need to individualize titration of immunosuppressive therapy, and to minimize late complications such as cardiac allograft vasculopathy, malignancy, and renal dysfunction. Advances have served to increase the organ donor pool by advocating the use of donors with underlying hepatitis C virus infection and by expanding the donor source to use hearts donated after circulatory death. New techniques to preserve the donor heart over prolonged ischaemic times, and enabling longer transport times in a safe manner, have been introduced. Mechanical circulatory support as a bridge to transplantation has allowed patients with advanced heart failure to avoid progressive deterioration in hepato-renal function while awaiting an optimal donor organ match. The management of the heart transplantation recipient remains a challenge despite advances in immunosuppression, which provide early gains in rejection avoidance but are associated with infections and late-outcome challenges. In this article, we review contemporary advances and challenges in this field to focus on donor recovery strategies, left ventricular assist devices, and immunosuppressive monitoring therapies with the potential to enhance outcomes. We also describe opportunities for future discovery to include a renewed focus on long-term survival, which continues to be an area that is under-studied and poorly characterized, non-human sources of organs for transplantation including xenotransplantation as well as chimeric transplantation, and technology competitive to human heart transplantation, such as tissue engineering.

Mechanical Circulatory Support as a Bridge-to-Transplant Candidacy: When Does It Work?

Durable mechanical circulatory support (dMCS) devices can be offered as a bridge-to-transplant (BTT) or as a bridge-to-candidacy (BTC) strategy for candidates with contraindications to transplant listing, including pulmonary hypertension (BTC-PH), morbid obesity (BTC-Obes), social issues (BTC-Soc), or chronic illness (BTC-Illness). An understanding of the trajectory of BTC patients could guide future triage of advanced heart failure patients who are not candidates for transplantation. We performed a retrospective review all patients who underwent dMCS implantation as either BTT (206 patients) or BTC (114 patients) at our center from January 1, 2010, to March 31, 2020. There was no significant difference in mortality between BTC patients and BTT patients. Compared with the BTT group, significantly more patients in the BTC-PH group were transplanted (81% vs. 63%; p < 0.05) and significantly fewer patients in the BTC-Obes group (44%; p < 0.05) and BTC-Soc group (39%; p < 0.05) were transplanted. Additionally, the readmission rate was higher for those in the BTC-Obes (6.2 vs. 2.1; p < 0.05) and BTC-Soc (3.9 vs. 2.1; p < 0.05) groups. Bridge-to-candidacy patients generally had poorer post-dMCS trajectories than BTT patients. Centers should not be dissuaded from pursuing a BTC strategy for qualified patients; however, careful consideration of potential adverse outcomes is necessary.

Invasive Haemodynamic Assessment Before and After Left Ventricular Assist Device Implantation: A Guide to Current Practice

Mechanical circulatory support for the management of advanced heart failure is a rapidly evolving field. The number of durable long-term left ventricular assist device (LVAD) implantations increases each year, either as a bridge to heart transplantation or as a stand-alone ‘destination therapy’ to improve quantity and quality of life for people with end-stage heart failure. Advances in cardiac imaging and non-invasive assessment of cardiac function have resulted in a diminished role for right heart catheterisation (RHC) in general cardiology practice; however, it remains an essential tool in the evaluation of potential LVAD recipients, and in their long-term management. In this review, the authors discuss practical aspects of performing RHC and potential complications. They describe the haemodynamic markers associated with a poor prognosis in patients with left ventricular systolic dysfunction and evaluate the measures of right ventricular (RV) function that predict risk of RV failure following LVAD implantation. They also discuss the value of RHC in the perioperative period; when monitoring for longer term complications; and in the assessment of potential left ventricular recovery.

Pulmonary vasodilator use in continuous-flow left ventricular assist device management

Pulmonary hypertension (PH) due to left heart disease is the most common etiology for PH. PH in patients with heart failure with reduced fraction (HFrEF) is associated with reduced functional capacity and increased mortality. PH-HFrEF can be isolated post-capillary or combined pre- and post-capillary PH. Chronic elevation of left-sided filling pressures may lead to reverse remodeling of the pulmonary vasculature with development of precapillary component of PH. Untreated PH in patients with HFrEF results in predominant right heart failure (RHF) with irreversible end-organ dysfunction. Management of PH-HFrEF includes diuretics, vasodilators like angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers or angiotensin-receptor blocker-neprilysin inhibitors, hydralazine and nitrates. There is no role for pulmonary vasodilator use in patients with PH-HFrEF due to increased mortality in clinical trials. In patients with end-stage HFrEF and fixed PH unresponsive to vasodilator challenge, implantation of continuous-flow left ventricular assist device (cfLVAD) results in marked improvement in pulmonary artery pressures within 6 months due to left ventricular (LV) mechanical unloading. The role of pulmonary vasodilators in management of precapillary component of PH after cfLVAD is not well-defined. The purpose of this review is to discuss the pharmacologic management of PH after cfLVAD implantation.

Physiology of the Assisted Circulation in Cardiogenic Shock: A State-of-the-Art Perspective

Mechanical circulatory support (MCS) has made rapid progress over the last 3 decades. This was driven by the need to develop acute and chronic circulatory support as well as by the limited organ availability for heart transplantation. The growth of MCS was also driven by the use of extracorporeal membrane oxygenation (ECMO) after the worldwide H1N1 influenza outbreak of 2009. The majority of mechanical pumps (ECMO and left ventricular assist devices) are currently based on continuous flow pump design. It is interesting to note that in the current era, we have reverted from the mammalian pulsatile heart back to the continuous flow pumps seen in our simple multicellular ancestors. This review will highlight key physiological concepts of the assisted circulation from its effects on cardiac dynamic to principles of cardiopulmonary fitness. We will also examine the physiological principles of the ECMO-assisted circulation, anticoagulation, and the haemocompatibility challenges that arise when the blood is exposed to a foreign mechanical circuit. Finally, we conclude with a perspective on smart design for future development of devices used for MCS.

Heart Transplantation After Ventricular Assist Device Therapy: Benefits, Risks, and Outcomes

Heart transplantation is an established treatment for end-stage heart failure. Due to the increase in demand and persistent scarcity of organ, mechanical circulatory devices have played a major role in therapy for advanced heart failure. Usage of left ventricular assist device (LVAD) has gone up from 6% in 2006 to 43% in 2013 as per the United Network of Organ Sharing database. Majority of patients presenting for a heart transplantation are often bridged with an assist device prior for management of heart failure while on wait-list. On one hand, it is well established that LVADs improve survival on wait-list; on the other hand, the effect of LVAD on morbidity and survival after a heart transplantation is still unclear. In this article, we review the available literature and attempt to infer the outcomes given the risks and benefits of heart transplantation with prior LVAD patients.