UNOS status of heart transplant patients supported with a left ventricular assist device: is it time to reconsider the status criteria?

The recent introduction of the continuous-flow left ventricular assist device (LVAD) has had an important impact on outcomes for those receiving bridge-to-transplantation (BTT) therapy. Because of the demonstrated survival and quality-of-life benefit with LVAD support and the broader availability of these devices after their commercialization, the number of supported patients waiting for heart transplantation is increasing. Progress in LVAD technology, better patient selection, and refined postoperative management all contribute to improved operative outcomes and long-term survival. Patients can now be safely supported by LVADs for many years. As demand for the limited number of available donor organs increases, policies regarding the status of transplant candidates may need to be revised for optimal management of this scarce resource. Heart Transplant Waiting-List Status The United Network for Organ Sharing (UNOS) status code 1A is designated for candidates on the waiting list who have the highest priority on the basis of medical urgency. Patients may be listed as Status 1A for 30 days at any time after LVAD implantation when they are clinically stable. Patients who are experiencing LVAD-related complications, such as infection, thromboembolism, or device malfunction, may also be listed as Status 1A (Table I). Patients who are supported by an LVAD but who do not meet the aforementioned criteria are listed as Status 1B. Status 2 does not apply to patients with LVADs. TABLE I. UNOS Definition of Status 1A for Candidates on Waiting List* Changes in LVAD Technology The criteria for the UNOS listing status were established when the previous generation of pulsatile LVADs was being used for BTT therapy. The chief drawbacks of the pulsatile LVAD were related to its large size and poor durability. The device had to be placed in an abdominal pocket that remained susceptible to serious infection throughout support. Durability was limited due to bearing wear and the development of valve incompetence in the device. Therefore, reliable LVAD operation was limited to approximately 18 months, which greatly increased the chances of morbidity and death from either the cessation of LVAD support or the need to replace the device. In comparison with the pulsatile LVAD, the continuous-flow LVAD is considerably smaller and more durable. The surgery required for LVAD implantation is less extensive, which helps to reduce complications related to bleeding and infection. The lack of device failure has nearly eliminated the need for replacement surgery, which further reduces the incidence of serious complications. In the only randomized clinical trial comparing the 2 types of LVADs, complications—including pump replacement, infection, bleeding, right-sided heart failure, arrhythmia, respiratory failure, renal failure, and hospitalization—were all significantly less for the continuous-flow LVAD group.1 The survival rate was also significantly higher (P < 0.001) with the continuous-flow device. The current survival rate for BTT therapy with a continuous-flow LVAD is 85%, and the device is associated with greatly improved functional capacity and quality of life.2,3 The risk of serious complications is low, which may result in less urgency to perform heart transplantation in clinically stable outpatients. In the early BTT experience with continuous-flow LVADs (2005–2008), 48% of patients had undergone transplantation at 1 year, compared with 39% in the later experience (2008–2010). This shows increasing confidence that LVADs can support patients longer.4 Also, some patients have chosen to forgo transplantation in favor of continued LVAD support. Although the clinical experience with continuous-flow LVADs has been largely positive, some problems persist and new ones have emerged. Rarely, patients may need to be readmitted to the hospital because the LVAD percutaneous driveline becomes infected; in some cases, this complication increases the urgency for transplantation.5 Surgical bleeding has been reduced but not been eliminated. Late gastrointestinal bleeding associated with continuous-flow LVADs is controllable in most cases; however, it can be persistent or severe and require multiple transfusions. Patients who are supported for longer periods of time might develop recurrent right-sided heart failure, which can limit pump performance and worsen quality of life. Similarly, with longer durations of support, new valve gradients and stress on the native aortic valve will cause some patients to develop substantial aortic insufficiency. Reevaluating UNOS Status The criteria for UNOS status codes were developed at a time when device-related infections were prevalent and when life-threatening LVAD failure or pump malfunction was due to failure of the device's bearings or incompetence of its valves. However, outcomes of BTT therapy have dramatically improved over the past decade, while unanticipated device-related complications have emerged. Currently, driveline infection is a common reason for upgrading a patient to Status 1A, but in the absence of sepsis or a true device-pocket infection, the driveline infection rarely threatens a patient's life or alters the device. In addition, impending pump failure or a device-related complication, such as bearing wear, was once easy to recognize and attribute to the device; however, this has changed with the new technology. Complications such as gastrointestinal bleeding and aortic insufficiency are probably related to the pump, whereas hemolysis is perhaps the new indicator of impending pump failure. These new complications are not clearly considered in the current UNOS guidelines. Also, given the increasing number of outpatients who are on LVAD support, it is very difficult to perform heart transplantation in a Status 1B patient who is receiving continuous inotropic agents without invasive monitoring. Today, a patient who is at home with long-term LVAD support is more like the traditional Status 2 patient with respect to the risk of serious complications or death. According to the current UNOS status criteria, all medically stable BTT patients can be given 1A status for 30 days. This 30-day 1A listing window for BTT patients does not reflect true urgency on the basis of medical need. Many of these patients undergo transplantation when they are doing well at home with an excellent functional status and without device complications. Overall, the UNOS criteria for listing patients for heart transplantation and for determining their status for priority has resulted in the best use of a limited resource. However, the evolving LVAD technology has led to significant shifts in patient outcomes and device-related complications. Technological improvements and the increasing clinical use of LVADs have resulted in a new generation of patients waiting for heart transplantation. It might be time to revisit the clinical indications for establishing the priority and status categories for patients who are eligible to receive a donor offer for heart transplantation.