Temporary MCS a Safe, Effective Strategy for the Transplant Waitlist

Use of temporary mechanical circulatory support (MCS) as a bridge to transplantation was a good strategy for many people following implementation of the 2018 national donor heart allocation policy, yet hemodynamic criteria may need to be modified to better identify the most urgent transplant candidates.

Within 14 days of status 2 listing, people with either a percutaneous endovascular MCS device or an intra-aortic balloon pump (IABP) received a heart transplant in 64.2% of cases, and only 1.9% died or were delisted for worsening clinical condition (a figure that rose to 3.1% at 30 days on the waitlist).

Thus, temporary MCS represented a “safe, effective, and efficient” bridging strategy for status 2 patients and was associated with a “relatively low prevalence of adverse events when considering the patient’s clinical status,” reported Veli Topkara, MD, MS, of Columbia University Irving Medical Center in New York City, and colleagues in JACC: Heart Failure.

Likelihood of transplantation at 30 days was similar among heart failure patients eligible for status 2 by different criteria:

• Cardiogenic shock with hemodynamic criteria (CS-HD; 68.6% of the group): 80.1% likelihood
• Cardiogenic shock without hemodynamic criteria before temporary MCS (CS-woHD; 3.2%): 73.3% likelihood
• Exceptions (28.2%): 79.7% likelihood

Yet patients with CS-woHD had a higher risk of death or delisting — delisting in particular — compared with peers who met hemodynamic criteria (adjusted HR 2.28, 95% CI 1.10-4.75).

“Although some of this risk may be the result of individual patient management, it does put forward that the CS-woHD group warrants greater priority on the waitlist, and incorporation of biomarkers of organ hypoperfusion (elevated lactate, acute kidney injury, ischemic hepatitis) may help provide greater differentiation of patients with the greatest risk of waitlist mortality,” Topkara and colleagues wrote.

“However, although implementation of a more restrictive criteria may identify higher-risk individuals, it increases the possibility of excluding patients who may not fulfill all criteria … and thus may further expand the exception group,” they added.

In contrast, given that none of the pre-temporary MCS hemodynamic criteria were predictive of waitlist adverse events, it appeared that “at least some individuals who meet CS-HD criteria are not as acutely at risk as initially thought,” the group found.

“This was thought provoking given the wide hemodynamic ranges that existed among this patient cohort, and it suggests that systolic blood pressure, cardiac index, and PCWP [pulmonary capillary wedge pressure] are not sufficient discriminators of disease severity,” they noted.

In October 2018, the United Network for Organ Sharing (UNOS) changed its policy, such that people on temporary MCS became higher-priority transplant candidates, whereas durable left ventricular assist device (LVAD) users were pushed to lower tiers.

Recent studies have shown a growth in temporary MCS users, and a commensurate fall in LVAD users, on the transplant waitlist because of this policy change.

Indeed, Topkara and colleagues reported that among the 35.8% of status 2 patients who did not undergo transplantation within 14 days, only 2.8% went on to receive a durable LVAD.

“Patient and physician preference to go directly to transplantation, thereby avoiding additional surgery (LVAD implantation), the risk of complications following LVAD implantation before future transplant surgery, and the prolonged waitlist time that LVAD recipients face in the current system likely explain the small number of patients who transitioned to LVAD in this cohort,” the investigators wrote.

Their study included 2,279 adults with heart failure in the UNOS registry who received status 2 designation for transplant. Of this cohort, 87.1% had an IABP, and 12.9% had a percutaneous endovascular MCS device.

Topkara’s team acknowledged that the UNOS dataset is subject to reporting inaccuracies and lacks information on the causes of death or delisting among transplant candidates.