Transplants from HCV-infected donors to uninfected recipients
Hearts and lungs from donors with hepatitis C viremia were traditionally deemed unsuitable for transplant. That’s all changed in the current era of highly effective direct-acting antiviral agents for the treatment of HCV infection.
In the DONATE HCV trial, Dr. Desai’s colleagues at Brigham and Women’s Hospital showed that giving HCV-uninfected recipients of hearts or lungs from HCV-viremic donors a shortened 4-week course of treatment with sofosbuvir-velpatasvir (Epclusa) beginning within a few hours after transplantation uniformly blocked viral replication. Six months after transplantation, none of the study participants had a detectable HCV viral load, and all had excellent graft function (N Engl J Med. 2019 Apr 25;380[17]:1606-17).
“This is effective prevention of HCV infection by aggressive upfront therapy,” Dr. Desai explained. “We can now take organs from HCV-viremic patients and use them in solid organ transplantation. This has led to a skyrocketing increase in donors with HCV infection, and those donations have helped us clear the waiting list.”
Donation after circulatory death
Australian transplant physicians have pioneered the use of donor hearts obtained after circulatory death in individuals with devastating neurologic injury who didn’t quite meet the criteria for brain death, which is the traditional prerequisite. In the new scenario, withdrawal of life-supporting therapy is followed by circulatory death, then the donor heart is procured and preserved via extracorporeal perfusion until transplantation.
The Australians report excellent outcomes, with rates of overall survival and rejection episodes similar to outcomes from brain-dead donors (J Am Coll Cardiol. 2019 Apr 2;73[12]:1447-59). The first U.S. heart transplant involving donation after circulatory death took place at Duke University in Durham, North Carolina. A multicenter U.S. clinical trial of this practice is underway.
If the results are positive and the practice of donation after circulatory death becomes widely implemented, the U.S. heart donor pool could increase by 30%.
Recent overhaul of donor heart allocation system may have backfired
The U.S. donor heart allocation system was redesigned in the fall of 2018 in an effort to reduce waiting times. One of the biggest changes involved breaking down the category with the highest urgency status into three new subcategories based upon sickness. Now, the highest-urgency category is for patients in cardiogenic shock who are supported by extracorporeal membrane oxygenation (ECMO) or other temporary mechanical circulatory support devices.
But an analysis of United Network for Organ Sharing (UNOS) data suggests this change has unintended adverse consequences for clinical outcomes.
Indeed, the investigators reported that the use of ECMO support is fourfold greater in the new system, the use of durable left ventricular assist devices (LVADs) as a bridge to transplant is down, and outcomes are worse. The 180-day rate of freedom from death or retransplantation was 77.9%, down significantly from 93.4% in the former system. In a multivariate analysis, patients transplanted in the new system had an adjusted 2.1-fold increased risk of death or retransplantation (J Heart Lung Transplant. 2020 Jan;39[1]:1-4).
“When you create a new listing system, you create new incentives, and people start to manage patients differently,” Dr. Desai observed. “Increasingly now, the path direct to transplant is through temporary mechanical circulatory support rather than durable mechanical circulatory support. Is that a good idea? We don’t know, but if you look at the best data, those on ECMO or percutaneous VADs have the worst outcomes. So the question of whether we should take the sickest of sick patients directly to transplant as a standard strategy has come under scrutiny.”
Improved durable LVAD technology brings impressive clinical outcomes
Results of the landmark MOMENTUM 3 randomized trial showed that 2-year clinical outcomes with the magnetically levitated centrifugal-flow HeartMate 3 LVAD now rival those of percutaneous mitral valve repair using the MitraClip device. Two-year all-cause mortality in the LVAD recipients was 22% versus 29.1% with the MitraClip in the COAPT trial and 34.9% in the MITRA-FR trial. The HeartMate 3 reduces the hemocompatibility issues that plagued earlier-generation durable LVADs, with resultant lower rates of pump thrombosis, stroke, and GI bleeding. Indeed, the outcomes in MOMENTUM 3 were so good – and so similar – with the HeartMate 3, regardless of whether the intended treatment goal was as a bridge to transplant or as lifelong destination therapy, that the investigators have recently proposed doing away with those distinctions.
“It is possible that use of arbitrary categorizations based on current or future transplant eligibility should be clinically abandoned in favor of a single preimplant strategy: to extend the survival and improve the quality of life of patients with medically refractory heart failure,” according to the investigators (JAMA Cardiol. 2020 Jan 15. doi: 10.1001/jamacardio.2019.5323).
The next step forward in LVAD technology is already on the horizon: a fully implantable device that eliminates the transcutaneous drive-line for the power supply, which is prone to infection and diminishes overall quality of life. This investigational device utilizes wireless coplanar energy transfer, with a coil ring placed around the lung and fixed to the chest wall. The implanted battery provides more than 6 hours of power without a recharge (J Heart Lung Transplant. 2019 Apr;38[4]:339-43).
“The first LVAD patient has gone swimming in Kazakhstan,” according to Dr. Desai.
Myocardial recovery in LVAD recipients remains elusive
The initial hope for LVADs was that they would not only be able to serve as a bridge to transplantation or as lifetime therapy, but that the prolonged unloading of the ventricle would enable potent medical therapy to rescue myocardial function so that the device could eventually be explanted. That does happen, but only rarely. In a large registry study, myocardial recovery occurred in only about 1% of patients on mechanical circulatory support. Attempts to enhance the process by add-on stem cell therapy have thus far been ineffective.
“For the moment, recovery is still a hope, not a reality,” the cardiologist said.
He reported serving as a consultant to more than a dozen pharmaceutical or medical device companies and receiving research grants from Alnylam, AstraZeneca, Bayer Healthcare, MyoKardia, and Novartis.
bjancin@mdedge.com