**7. Conclusion**

provide an accurate representation of waiting list mortality in patients receiving continuousflow LVAD support. Because the cause of death of LVAD patients is usually unrelated to heart failure; heart failure score models may either under- or overestimate the risk of mortality in these patients. This, in turn, leads to inaccurate organ allocation, and may come at the cost of

The current organ procurement protocol for patients with an LVAD is based on outcome studies performed in the era in which pulsatile flow devices were used. Based on these outcomes, patients implanted with an LVAD awaiting orthotopic heart transplant are status 1B on the waiting list, with the option of a 30-day upgrade to status 1A at the discretion of the transplant center. In addition, patients with an LVAD can be upgraded to status 1A in the event of a device complication or malfunction. However, it is not clear that patients on LVAD support necessarily merit this degree of prioritization. For example, a retrospective review of UNOS data revealed that despite being older, less favorable recipients, modern LVAD patients spend more time in Status 1A and have greater waitlist survival, which allows LVAD patients to receive preferred donor hearts and could allow for better post-transplant survival [59]. In particular, a 30-day upgrade of relatively stable LVAD patients to the highest priority level (compared with other critically ill patients at Status 1A) may allow for competition between patients with different risks of death. With this in mind, there is a concern that LVAD is perceived as a not a bridge to transplant, but a necessary gateway to transplant that is at risk of being over utilized. Furthermore, simulations have failed to demonstrate improvements in waiting list survival or post-transplant mortality with the Status 1A time allotment [60].

There is still an argument to be made, however, that the risk of VAD complications, including thrombosis, infection and sensitization that compromise post-transplant outcomes and abrogate any potential benefit that may have been realized by having the VAD; furthermore, the aforementioned allocation simulations do not demonstrate increased waiting list mortality for other candidates who did not have VADs in lieu of other mechanical support. What is perhaps the most likely reason for all of these findings is that the allocation system is already saturated with candidates at Status 1A and adding more Status 1A time for VAD patients would do little to solve the problem–instead, a more efficient method would involve risk stratification prioritization of those VAD patients at higher risk for mortality in contrast to

Studies are ongoing to develop strategies to make smaller and more durable devices, to diminish thrombosis, and to minimize surgical complication rates. A miniaturized LVAD could reduce the extent of surgical intervention, and would potentially extend the use of the LVAD for support of earlier stages of heart failure. Revolutionary future devices currently under trial will not require sternotomy or cardiopulmonary bypass; instead they will be placed through a minithoracotomy incision into a subclavicular subcutaneous pocket similar to a pacemaker. Future technology will ideally allow for completely implantable devices, as well as for devices that can provide variable flow in the LVAD, with automated modulation of

A return of pulsatile LVAD is also to be expected. There is recent research to suggest that pulse pressure causes vascular responses such as the endothelial production of nitric oxide and vasodilation

those stable VAD patients who are at relatively lower risk.

flow in the setting of increased demand such as during exercise.

**6.3. The future of LVAD support**

60 Heart Transplantation

detrimentally affecting the transplant chances of those patients without LVADs.

Left ventricular assist devices represent a useful adjunct in the setting of bridge to orthotopic heart transplant. There are still a number of unanswered questions regarding their efficient use; most of these questions have come about secondary to the incredible speed innovation surrounding these tools as well as their rapid and widespread adoption. There is a critical need for continued high quality studies such as large, well conducted, randomized controlled trials, particularly addressing the issues of justice in donor organ allocation, patient selection, complication avoidance, and needs of high-risk patient groups. Although this technology, and the field of heart transplantation in general, is associated with multiple remaining challenges and complications remain, it is clear that the LVAD is a powerful tool for augmenting the failing heart and stabilizing the transplant candidate while a donor organ becomes available. It represents an important facet in the holistic care of this challenging patient population.
