Objectives This study was designed to delineate the role of implantable cardioverter defibrillator (ICD) therapy for the primary and secondary prevention of sudden cardiac death in patients listed for heart transplantation.

Setting Retrospective observational multicentre study.

Patients 1089 consecutive patients listed for heart transplantation in two tertiary heart transplant centres were enrolled. Of 550 patients (51%) on the transplant list with an ICD, 216 had received their ICD for the primary prevention of sudden cardiac death and 334 for secondary prevention. 539 patients did not receive an ICD.

Intervention Treatment with or without an ICD was left to the discretion of the heart failure specialist.

Main outcome measure All-cause mortality.

Results ICDs appear to be associated with a reduction in all-cause mortality in patients implanted with the device for primary and secondary prevention compared to those without an ICD despite a median time on the waiting list of only 8 months (estimated 1-year: 88±3% vs 77±3% vs 67±3%; p=0.0001). A Cox regressional hazard model (corrected for age, sex, underlying heart disease, atrial fibrillation, cardiac resynchronisation therapy, New York Heart Association (NYHA) class, ejection fraction, co-medication and year of listing) suggested an independent beneficial effect of ICDs that was most pronounced in patients who had received an ICD for primary prevention (HR 0.4, 95% CI 0.19 to 0.85; p=0.016).

Conclusions ICD implantation appears to be associated with an immediate and sustained survival benefit for patients awaiting heart transplantation.