About 5-10% of the population will die from ventricular fibrillation or tachycardia, according to Framingham data. A class one indication for implantable cardioverter-defibrillators (ICD) includes patients who have these symptoms or survive a VF event, in the absence of acute myocardial infarction or other reversible causes.

The Canadian Cardiovascular Society/Canadian Heart Rhythm Society Guidelines for ICD implantation in 2009 also recommend considering the devices in patients with ischemic heart disease. But to be a good candidate, the guidelines say, the patient must have a left ventricular ejection fraction (LVEF) of less than 30%, measured at least 40 days post-myocardial infarction and at least three months post-coronary revascularization procedure (CABG or PCI).

Why we don’t use ICDs in recent heart attack

The rationale for this delay comes from the DINAMIT trial, which showed no overall survival benefit from ICD implantation in recent MI patients with low (< 35%) ejection fraction. The reason for the lack of benefit appears to have been twofold: First, the low LVEF was often a temporary effect of the MI, and LV function recovered soon after, so these weren’t really the kind of patients who benefit from ICDs. Secondly, many of the peri-infarct arrhythmias seen in these people were ischemia-mediated and thus didn’t necessarily respond to ICD therapy.

The MADIT 2 trial, rather than looking at recent MI patients, took those with any MI history, plus low LVEF (< 30%), and achieved very different results. Over 4 years, all-cause mortality in the ICD group was 41% lower than in the conventional medical therapy group, and the benefit continued thereafter. The researchers calculated a treatment cost of $50,000 per year of life saved over 8 years. To save one life, 6 ICDs needed to be implanted.

These results have been confirmed in the SCD-HeFT 2521 trial, which found a 23% relative risk reduction in the ICD group vs placebo. These individuals all had LVEF < 35% (52% ischemic cause, 38% non-ischemic) and congestive heart failure symptoms (NYHA class II or III). An amiodarone group saw no survival benefit vs placebo.

ICDs vs anti-arrhythmic drugs

The anti-arrhythmic amiodarone does reduce the risk of sudden cardiac death, but its overall survival benefit is neutral, due to pulmonary and thyroid toxicity.

ICD therapy is clearly superior to anti-arrhythmic drugs. But ICD use is limited, partly by cost (implanting a device costs roughly $25,000). Moreover, many of these patients have multiple comorbidities and poor long-term prognosis. I urge all my ICD patients to write an advance directive. Suitable selection of those with few comorbidities who aren’t in severe heart failure is of paramount importance.

ICDs aren’t perfect — approximately 25% of shocks are inappropriate and can interfere with quality of life. Patients may face recalls and will require frequent interaction with the health system.

Device therapy is lifesaving in the appropriate patient, but is only one component of the overall management of poor left ventricular function. Remember that beta-blockers decrease sudden-death mortality in the order of 25% and should not be forgotten.