Implantable cardioverter-defibrillators in heart transplant patients: a systematic review and meta-analysis

Type of funding sources: None.

Whilst implantable cardioverter-defibrillator (ICD) implantation is beneficial in a select group of patients, heart transplant patients were excluded from landmark clinical trials. Thus, controversy remains about the utility of ICD in high-risk heart transplant patients.

To understand the utility, benefits and side-effects of ICD in heart transplant patients.

Five electronic databases were systematically searched from their inception to August 2021, in order to identify all studies which explored the role of ICD in heart transplant patients.  We used a random-effects model for data analysis based on event rates (ER) and 95% confidence interval (CI). Publication bias was assessed using funnel plots and Egger’s regression analysis.

Eleven studies with 4648 heart transplant patients, 129 of whom received ICD, met the inclusion criteria for the meta-analysis. Studies included two multicentre retrospective cohort studies, four single centre retrospective cohort studies, two case series and three case reports. Of the 129 heart transplant patients with ICD, 74% were men, mean age at ICD implantation was 48.5 years, mean time from transplant to ICD was 99 months, and mean follow-up duration was 40 months.

The indication for ICD implantation was often multifactorial and included severe allograft vasculopathy (40%), the presence of left ventricular systolic dysfunction (37%), documented VT/VF (14%), unexplained syncope (14%), and history of cardiac arrest (13%).

Appropriate ICD therapy for patients occurred as an average event rate of 19% (95% CI 13%-27%) (I2 = 0% p = 0.66), Figure 1. Inappropriate therapy for patients occurred as an average event rate of 9% (95% CI 5%-16%) (I2 = 0% p = 0.96), Figure 2. There was no evidence of publication bias.

In total, nine ICD-related complications were reported including pocket haematoma (n = 1), pocket site infection (n = 2), infection of the ICD system (n = 1), lead displacement (n = 2) and lead fracture (n = 1). Mortality occurred in 28 patients, with heart failure being the leading primary cause of death (n = 10), followed by sepsis (n = 6), arrhythmia (n = 3) and electromechanical disassociation (n = 3).

Heart transplant patients with ICD more often received appropriate than inappropriate ICD shock therapy. The 19% appropriate ICD shock rate suggests a high burden of ventricular arrhythmias in high-risk heart transplant patients. Thus, ICD therapy may be beneficial in a select subset of heart transplant patients, keeping in mind even with appropriate shock therapy, subsequent terminal electromechanical disassociation and arrhythmias may imply ICD are not fully protective against arrhythmic aetiologies of mortality.

Abstract Figure 1