ICDs prevented sudden cardiac death in patients with hypertrophic cardiomyopathy

Consider primary prevention defibrillator implantation in select patients with single risk factor for sudden cardiac death.

Implantable cardioverter defibrillators have been successfully used systematically as a potentially lifesaving treatment in high-risk patients with hypertrophic cardiomyopathy in the last few years.

“If applied to the appropriate subset of patients, this therapy may change the clinical course of the disease,” Barry J. Maron, MD, director of the Hypertrophic Cardiomyopathy Center, Minneapolis Heart Institute Foundation, told Cardiology Today.

Maron and colleagues analyzed data from an international, multicenter registry of ICDs implanted in high-risk patients with hypertrophic cardiomyopathy (n=506) between 1986 and 2003. Mean age of patients was 42 years at device implantation for secondary (n=123) or primary prevention (n=383). Patients, of which 323 were men, were judged to be at high risk for sudden death. Mean follow-up was 3.7 years.

Twenty percent of patients experienced one or more appropriate device intervention, in which the ICD terminated ventricular fibrillation (n=49) or ventricular tachycardia (n=54). Total appropriate intervention rate was 5.5% per year (95% CI, 4.5%-6.6%). Probability of discharge at five years was 23%.

High-risk patients

Forty-two percent of patients in the secondary prevention group experienced appropriate device interventions. Intervention rate was 10.6% per year (95% CI, 7.9%-13.9%). Probability of discharge at five years was 39%.

Thirteen percent of patients in the primary prevention group experienced appropriate device interventions. Intervention rate was 3.6% per year (95% CI, 2.7%-4.8%). Probability of discharge at five years was 17%.

Among patients with appropriate interventions, 38 had one discharge, 44 had two to five discharges, and 21 had more than five discharges. Beyond five years, overall probability of first appropriate device intervention was 27%.

Fourteen percent of patients with one risk factor in the primary prevention group experienced appropriate device interventions compared with patients with two risk factors (11%) and greater than three risk factors (17%). For primary prevention, 35% of patients with appropriate ICD interventions had undergone implantation for a single factor. Likelihood of appropriate discharge was similar in patients with one, two, or three or more risk factors.

“It is important to assess risk level in young, even asymptomatic, patients with hypertrophic cardiomyopathy,” Maron said.

“An important proportion of these device interventions occurred in patients who had undergone prophylactic ICD implantation for a single risk factor,” he said in a press release. “Therefore, a single risk marker of high-risk status may justify consideration for a primary prevention defibrillator in selected patients with hypertrophic cardiomyopathy.” – by Christen Haigh

There was an old idea that when patients with hypertrophic cardiomyopathy fibrillated, they could not be defibrillated, or it was extremely difficult to defibrillate them. Obviously, Dr. Maron has shown that an ICD can defibrillate patients and do so with good results.

– Douglas P. Zipes, MD

Section Editor, Electrophysiology and Arrhythmia Disorders,
Cardiology Today Editorial Board

For more information:

• Maron BJ, Spirito P, Shen WK, et al. Implantable cardioverter-defibrillators and prevention of sudden cardiac death in hypertrophic cardiomyopathy. JAMA. 2007;298:405-412.