Aims: The implantable defibrillator (ICD) reduces arrhythmic and all-cause mortality in patients with a history of life-threatening ventricular arrhythmias. However, its effectiveness in elderly patients is uncertain, given their competing risk of non-arrhythmic death.
Methods and results: Individual patient data from all three secondary prevention trials comparing the ICD to amiodarone were pooled. Patients were divided into two groups based on age < 75 and > or = 75 years. Patient characteristics were reported and the effect of the ICD on all-cause mortality and arrhythmic death was determined for each group. The effect of age on these outcomes was determined by evaluating the interaction term (age-treatment). A total of 1866 patients were included in this analysis. Their mean age was 63.7 +/- 10.4 years (intra-quartile range 58-71 years). There were 252 patients > or = 75 years old (13.5% of total). Patients > or = 75 years old had a similar left ventricular (LV) ejection fraction (EF)(32.6 +/- 13.7 vs. 33.8 +/- 14.9%, P = 0.20) and baseline prevalence of NYHA class 3 or 4 heart (12.3 vs. 11.8%, P = 0.38) failure as younger patients, but were less likely to have ventricular fibrillation as their presenting arrhythmia (39 vs. 53%, P = 0.0001). Over a mean follow-up of 2.3 years, older patients were more likely to die of non-arrhythmic death (8.74% per year vs. 3.96% per year, P = 0.001) and arrhythmic death (6.73% per year vs. 3.84% per year, P = 0.03). The ICD significantly reduced all-cause and arrhythmic death in patients < 75 years old (all-cause death HR = 0.69, 95% CI: 0.56-0.85, P < 0.0001; arrhythmic death HR = 0.44, 95% CI: 0.32-0.62, P < 0.0001), but not in patients > or = 75 years old (all-cause death HR = 1.06, 95% CI: 0.69-1.64, P = 0.79; arrhythmic death HR = 0.90, 95% CI: 0.42-1.95, P = 0.79). The interaction between age > or = 75 and ICD use was of borderline significance in each case (P = 0.09 and P = 0.11, respectively).
Conclusion: Elderly patients with a history of life-threatening ventricular arrhythmias have a high incidence of non-arrhythmic death. In these patients, the ICD may not afford the same survival advantage over amiodarone that is seen in younger patients. ICD therapy should not be withheld based on age alone; however, physicians should carefully consider the risk of non-arrhythmic death among elderly patients when selecting the appropriate therapy for an individual.