Preventing Sudden Death with Implantable Defibrillators in Octogenarians: Too Much Too Late?

Implantable cardioverter defibrillators (ICD) are highly effective in the prevention of sudden arrhythmic deaths. The recurrence rate following an out of hospital cardiac arrest or ventricular tachycardia is as high as 24-44% over the ensuing 18-36 months that secondary prevention is an important consideration in patients without a clearly defined reversible cause such as acute ischemia or major metabolic derangement. In this context, the ICD has been shown to be superior to anti-arrhythmics drugs including amiodarone, in a number of clinical trials.  The value of an ICD is probably better expressed as the numbers needed to treat (NNT) to save a life. In the AVID trial, 9 patients had to be treated to save a life over a period of 3 years. The use of ICDs for primary prevention in patients at high risk for arrhythmic events is more controversial. The event rate is lower, and the benefit less pronounced as reflected in a larger NNT. In the MADIT II trial of patients with coronary artery disease and severe LV dysfunction, the NNT was 18 to save one life over a period of 20 months. In the SCD-Heft study of heart failure patients with LVEF < 0.35, the NNT was 14 over 5 year. In all cases, a non-arrhythmic cause limiting life expectancy to less than 1 year rarely justifies the use of an ICD. The use of ICDs in patients with advanced age is not well defined in clinical trials either because of exclusion for age over 80 or low representation of this age group. The current “appropriate use” guidelines suggest that an ICD may be appropriate in patients over the 80 years, based on individual considerations.