A recent study published in the Journal of the American College of Cardiology (JACC) looked to test the usefulness of the Destination Therapy Risk Score (DTRS) in patients with continuous flow left ventricular assist devices (LVAD). The DTRS was developed to predict the risk of 90-day in-hospital mortality with pulsatile flow LVAD as destination therapy (DT). 

The study, titled "Risk Assessment for Continuous Flow Left Ventricular Assist Devices: Does the Destination Therapy Risk Score Work? An Analysis of Over 1,000 Patients," established the DTRS in 1,124 patients with the continuous flow HeartMate II LVAD as a bridge to transplant (BTT) and destination therapy (DT) and 114 DT patients with the pulsatile flow HeartMate XVE. Patients were divided into low, medium and high risk groups. Study authors concluded that using DTRS in a large cohort of patients with a continuous flow device demonstrates only a modest ability to predict 90-day in-hospital mortality. For patients with continuous flow devices implanted as bridge to transplant (BTT), DTRS provides poor discrimination of two-year mortality. However, for patients implanted as DT, DTRS stratifies patient outcomes over two years but does not characterize a group of patients with a futile outcome.

An accompanying editorial, "Timing Isn’t Everything: Donor Heart Allocation in the Present LVAD Era," congratulates the study authors "for providing … a cautionary tale about prematurely adopting risk predictor models into clinical decision making." 

"Even though this DTRS has been widely applied and almost universally accepted, this score was never sufficiently prospectively validated," the editorial says. "Not only did the DTRS fail to risk-stratify recipients of a continuous flow pump, but it failed to effectively risk-stratify destination therapy recipients of a HeartMate XVE, a population similar to the derivation cohort. This is an important and timely observation for those working in the field of mechanical support, a field that depends on accurate and effective risk predictor models to advise patients and inform clinical decision making.”

Another JACC study, titled "Transplant Registrants With Implanted Left Ventricular Assist Devices Have Insufficient Risk to Justify Elective Organ Procurement and Transplantation Network Status 1A Time," attempts to identify risk disparities within heart transplant urgency designations. The disparities can occur because patients with LVADs are given 30 days of elective status 1A time, which can create competition for organs between stable LVAD-supported registrants and less stable registrants listed as status 1A or 1B.

After analyzing the Scientific Registry of Transplant Recipients database for all status 1A and 1B listings between 2005 and 2010, cox models were used to estimate the relative and absolute risk of adverse events, such as death or delisting as to illness during status 1A or 1B listing. Study authors found the historic allowance for 30 days of elective status 1A time for implanted LVADs creates disparities in risk among status 1A registrants. The allowance of 30 days of elective status 1A time should not be allocated to stable registrants with implanted LVADs. Registrants supported with paracorporeal ventricular assist devices should be listed as status 1A indefinitely.

"The popular idea that LVADs are not a bridge but a necessary gateway to transplant should be treated with caution to avoid over-application of LVAD therapy and policies that create inequality on the transplant list," the authors wrote.

The same accompanying editorial, which also commented on this study, disagreed with the authors’ conclusions. According to the editorial, there is no direct evidence that prioritizing stable LVAD patients has prevented other 1A patients from receiving timely transplants. However, the author of the editorial agreed that the current organ allocation system needs further refinement. The author also suggested the adoption of a heart allocation score, similar in principle to the model for end-stage liver disease or the lung allocation score, or expansion of the number of prioritization categories matching individual risk profiles.

The author wrote, "Regardless of which system emerges, facilitating this change will require robust data collection and analysis similar to the ones published today to achieve a fair and balanced system for our patients."

To read both studies online, visit http://content.onlinejacc.org/.

 

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