A first, large multicentre study in the United States has found that despite the advances in clinical management strategies after heart transplantation, there has not been an improvement in the incidence of sudden cardiac death (SCD) in heart transplant patients over the last three decades.
The study, led by Kairav Vakil, from the University of Minnesota, Minneapolis, USA, assessed the incidence, predictors, and temporal trends of SCD amongst heart transplant recipients. In this study, published in HeartRhythm, the authors retrospectively analysed data from the United Network for Organ Sharing registry on 37,492 patients who underwent first-time heart transplantation in the USA between 1 October 1987 and 31 December 2012.
Patients (mean age 51.9±11.7 years; 77% males; 78% Caucasian) were followed up for 6.5±5.7 years; during that period 17,324 (46%) deaths were identified. Their results indicate that approximately 10% of these deaths were due to SCD. They write, “The ration of sudden cardiac death to all deaths increased to 10% per year after the first year of follow-up and remained nearly constant thereafter.” Further, they note: “While there was a significant temporal reduction in the incidence of non-sudden deaths since 1987, the incidence of SCD has not changed.” Vakil et al also found that left ventricular ejection fraction (LVEF) ≤40%, allograft rejection, and higher donor age were associated with an increased risk of SCD. In contrast, higher recipient age and Caucasian race seemingly appeared to be protective against SCD.
Previous studies, the authors comment, have suggested that pacemakers could prevent SCD due to asystole and severe brady-arrhythmias, which has been reported in some heart transplant patients. In the present study, 3,080 (8%) patients were implanted with a permanent pacemaker; however, the analysis showed that its presence did not reduce SCD risk in heart transplant patients.
The authors call for the need for preventative strategies such as implantable cardioverter defibrillators (ICDs) that may possibly reduce the burden of SCD after heart transplantation. Vakil et al write: “Based on our findings one could speculate that ICD therapy may aid in preventing SCD in heart transplant recipients with an LVEF≤40%.” They refer to a retrospective observational multicentre study by Tsai et al (Circulation Heart Failure 2009;2:197-201), which reported that 22% of 36 heart transplant patients-who received an ICD for being at high-risk SCD-received appropriate ICD shocks during 51 months of follow-up. This study, they write, suggests that “ICD therapy may be effective in these patients. However caution is advised because reduction in sudden cardiac death with ICD may not translate to a reduction in total mortality.” Further future research is needed in this area, they note.
Vakil told Cardiac Rhythm News: “Currently, there are no data to support the use of primary prevention ICDs in heart transplant patients with low ejection fraction. It is important to note that heart transplant patients have a significantly higher incidence of non-sudden deaths as compared to patients with other cardiovascular diseases. However, the residual is still there and 10% of patients do suffer SCD. Whether tachyarrhythmias underlie a significant proportion of sudden deaths and whether ICD would benefit these patients, still remains to be studied. This calls for further validation studies, and perhaps even a multicentre randomised control clinical trial of primary prevention ICDs in certain high-risk heart transplant patients.”