Nine RCTs (5,314 participants) were included. Five of these were on primary prevention (3,291 participants) and four were on secondary prevention (2,023 participants).
Overall, less than 1.5% of the participants were lost to follow-up. There were 1,292 deaths.
Pooling all studies showed a 30% reduction in all-cause mortality (P<0.001); the RR was 0.66 (95% CI: 0.46, 0.96, P=0.03) for primary prevention and 0.75 (95% CI: 0.64, 0.87, P=0.0002) for secondary prevention.
Compared with the anti-arrhythmic drugs group, there was a 57% reduction in arrhythmic death in the ICD treatment group; the RR was 0.34 (95% CI: 0.23, 0.50, P<0.00001) for primary prevention and 0.50 (95% CI: 0.38, 0.66, P<0.00001) for secondary prevention.
Overall, there was no excess of nonarrhythmic deaths in the ICD treated group; the RR was 0.95 (95% CI: 0.74, 1.21) for primary prevention and 0.95 (95% CI: 0.71, 1.27) for secondary prevention.
Subgroup analyses: studies with industrial sponsorship showed significantly greater benefit of ICDS than those without such sponsorship. Results also differed between groups of studies defined by differing clinical conditions (further details were provided in the paper).
Treatment-related complications: peri-operative death with ICD implantation occurred in 1.2% of the participants without concomitant thoracotomy and CABG versus, for example, 5.5% of the participants in one large CABG trial. Other commonly reported adverse events in the ICD-treated group were infection (3.7%), pericardial effusion and tamponade (0.6%), pneumothorax (1.6%), lead dislodgement or fracture (2.3%) and device malfunction (2.0%). In the anti-arrhythmic agents-treated group, amiodarone pulmonary toxicity was the most common reported adverse event (weighted mean 4.8%, range: 3.0 to 5.7).