High-risk patients with hypertrophic cardiomyopathy appear to have reduced risk of sudden cardiac death with implantable cardioverter-defibrillators, according to an article in the July 25 issue of Journal of the American Medical Association.

Hypertrophic cardiomyopathy is the most common cause of sudden cardiac death in young people, including trained athletes, according to background information in the article. Only in the last few years has the implantable cardioverter-defibrillator been systematically used as a potentially life-saving treatment for patients with the genetic disorder. The effectiveness and appropriate selection of patients for implantation has not been clarified.

Barry J. Maron, MD, of the Minneapolis Heart Institute Foundation, Minneapolis, and colleagues examined the clinical risk profile and incidence and effectiveness of device use in patients with the disorder. Researchers analyzed data from a multicenter registry of devices implanted between 1986 and 2003 in 506 patients with hypertrophic cardiomyopathy, average age 42 years. Patients were judged to be at high risk for sudden death. Average follow-up was 3.7 years.

Risk factors analyzed included history of premature myopathy-related sudden death in one or more first-degree or other relatives younger than 50 year, massive left ventricular hypertrophy, a certain type of nonsustained ventricular tachycardia, and prior unexplained syncope.

Of the 506 patients, 20 percent experienced one or more appropriate device interventions, in which the device terminated ventricular fibrillation or ventricular tachycardia. Intervention rates were 10.6 percent per year for secondary prevention after cardiac arrest (five-year cumulative probability, 39 percent), and 3.6 percent per year for primary prevention (five-year probability, 17 percent).

Time to first appropriate discharge was up to 10 years, with a 27 percent probability at five years or more after implantation. For primary prevention, 35 percent of patients with appropriate device interventions had undergone implantation for only a single risk factor; likelihood of appropriate discharge was similar in patients with one, two, or three or more risk markers.

“The results of this international, multicenter study show the effectiveness and reliability of the ICD in prevention of sudden cardiac death in high-risk patients with hypertrophic cardiomyopathy,” the authors wrote. “An important proportion of these device interventions occurred in patients who had undergone prophylactic ICD implantation for a single risk factor. Therefore, a single marker of high-risk status may justify consideration for a primary prevention defibrillator in selected patients with hypertrophic cardiomyopathy.”

In an accompanying editorial, Rick A. Nishimura, MD, and Steve R. Ommen, MD, of the Mayo Clinic College of Medicine, Rochester, Minn., commented on the findings of the study by Maron and colleagues.

“Patients who have experienced cardiac arrest or documented sustained ventricular tachycardia definitely should be considered for implantation of an ICD. Patients with two or more risk factors likely present a high enough risk to warrant implantation of an ICD. However, the decision to implant an ICD in any patient, especially one with a single risk factor, must include a thorough and earnest discussion of the accuracy of the current risk assessment tools, the risks and benefits of ICD therapy, and the individual patient’s viewpoints on procedures, devices, and death. Such an approach will allow the patient-physician team to arrive at an individualized decision regarding ICD implantation.”