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Implantable Defibrillators in Preventing Sudden Death



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Am Fam Physician. 2000 Aug 15;62(4):858-859.

Hypertrophic cardiomyopathy is a common cause of sudden cardiac death. Although it is known to be a genetically determined disease, the natural history is variable. Some studies have attempted to determine which patients are at highest risk for sudden cardiac death, but the data remain scant. Consequently, data supporting medical therapies for patients with hypertrophic cardiomyopathy are also limited, with some suggestion that amiodarone is efficacious. Maron and colleagues conducted a retrospective, multicenter study to determine if implantable cardioverter-defibrillators were effective in preventing sudden death in patients with hypertrophic cardiomyopathy.

Patients were enrolled at numerous sites in the United States and Italy. Eligibility criteria included an unequivocal diagnosis of hypertrophic cardiomyopathy confirmed by two-dimensional echocardiographic evidence of a hypertrophied and nondilated left ventricle in the absence of another cardiac or systemic disease. All patients had undergone a previous implantation procedure of a cardioverter-defibrillator for the prevention of sudden death and a follow-up of at least three months following implantation. The prophylactic implantation in patients was performed for the primary prevention of sudden death. The primary clinical reasons included a history of syncope, a family history of sudden cardiac death because of hypertrophic cardiomyopathy, left ventricular wall thickness of at least 30 mm, nonsustained ventricular tachycardia on Holter monitor, or inducible ventricular tachycardia or fibrillation during electrophysiologic testing. Patients who had defibrillators implanted for secondary prevention included those who had experienced a previous cardiac arrest or sustained spontaneous ventricular tachycardia.

The study included 128 patients ranging from eight to 82 years of age. More than one half of the participants were less than 41 years of age and almost 70 percent were male. Defibrillators were implanted for primary prevention in 85 patients and for secondary prevention in 43 patients. Of the 128 patients enrolled in the study, 29 patients had one or more appropriate discharges of their defibrillators; 19 were in the secondary prevention group. The majority of these discharges were for ventricular fibrillation or ventricular tachycardia. Fifteen of the 29 patients were concurrently taking antiarrhythmic medications (predominantly amiodarone). The overall rate of appropriate discharges was 7 percent per year. In the group of 43 patients with defibrillators implanted for secondary prevention, the rate of appropriate discharge was 11 percent. Of the 29 patients with appropriate discharges, 21 had two or more discharges: 10 patients had ventricular tachycardia; nine had ventricular fibrillation (preceded by ventricular tachycardia in three of these patients); and two had multiple discharges of ventricular fibrillation and tachycardia. Nine patients experienced more than five appropriate discharges. Two deaths occurred in patients with end-stage cardiomyopathy for whom defibrillator discharges failed to reverse the ventricular dysrhythmia. Complications were noted in 18 of the 128 patients and included malfunction or fracture of leads in 12 patients, infection in two patients, and subclavian vein thrombosis, hemorrhage and hematoma in one patient each.

Maron and colleagues conclude from this data that implantable cardioverter-defibrillators are effective in preventing sudden cardiac death in patients with hypertrophic cardiomyopathy. The study has also determined that ventricular tachycardia or ventricular fibrillation is responsible for sudden death in this group of patients. They suggest that implantable defibrillators represent a life-saving device for patients with hypertrophic cardiomyopathy, and these devices should be considered for primary and secondary prevention in high-risk patients.

Maron BJ, et al. Efficacy of implantable cardioverter-defibrillators for the prevention of sudden death in patients with hypertrophic cardiomyopathy. N Engl J Med. February 10, 2000;342:365–73.

editor's note: Maron's data are consistent with published data suggesting that implantable cardioverter-defibrillators are much more effective than medical therapy for the prevention of sudden cardiac death in high-risk patients with ischemic heart disease. However, given that the trial was retrospective and nonrandomized, I believe that their recommendation of this intervention for primary prevention of sudden death (in the absence of more data) is premature. Further criteria to better understand factors that would classify patients with hypertrophic cardiomyopathy as “high risk” must be determined. In regard to cost consideration, the going rate for this device in our community is about $35,000—not including surgical costs.—j.t.k.

 

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