Nonsustained ventricular tachycardia as a predictor for sudden death in patients with idiopathic dilated cardiomyopathy. The role of amiodarone treatment.

BACKGROUND: Sudden death frequently occurs in patients with idiopathic dilated cardiomyopathy. Ventricular arrhythmias are encountered in almost all cases. The prognostic significance of life-threatening arrhythmias such as successfully resuscitated ventricular fibrillation and sustained ventricular tachycardia is well known, while it is controversial for ventricular arrhythmias of a lower degree. Amiodarone has been used widely in these patients but its value in preventing sudden death is still uncertain. The aim of this study was to evaluate the prognostic significance of runs of nonsustained ventricular tachycardia (NSVT) as a hallmark for sudden death and the efficacy of amiodarone in preventing sudden death and reducing overall mortality in a large series of patients with dilated cardiomyopathy. METHODS: Over the period between 1983 and 1994, a series of 151 consecutive patients with idiopathic dilated cardiomyopathy underwent ambulatory electrocardiographic monitoring for a mean period of 191 hours/patient. Seventy-nine patients (56 male, mean age 50.7 +/- 13.1 years) (group A) had ventricular arrhythmias of Lown class < or = 4A, while 72 (53 male, mean age 48.6 +/- 12.8 years) (group B) had one or more NSVT runs. The two groups were well matched in terms of clinical features. Mean follow-up period was 86.8 +/- 38.7 and 74.7 +/- 39.5 months, respectively. In group A no antiarrhythmic drug was administered, while in group B 54/72 patients were treated with amiodarone (mean dosage 300 mg/day) for a mean period of 69.7 +/- 37.8 months (group B1). The remaining 18 patients received class I antiarrhythmic drugs, mexiletine (12) and propaphenone (6) for a mean period of 46.1 +/- 29.4 months, because amiodarone was contraindicated (3) or serious side-effects occurred during amiodarone treatment (15), which was discontinued after a mean period of 3.8 +/- 3.1 months (group B2). RESULTS: The cumulative survival probability in the whole population was 86.6% at two years and 65.6% at five years. The rate of sudden death was 6.0% at two years and 18.3% at five years. No statistically significant difference was observed in terms of all-cause mortality or sudden death in the three groups (A, B1, B2). In group B1, amiodarone determined the disappearance of NSVT at Holter monitoring in 50% of patients (27), with no significant difference in the rate of sudden death between the two subgroups. CONCLUSIONS: In unselected patients with idiopathic dilated cardiomyopathy, cardiovascular mortality does not differ between those with NSVT on chronic amiodarone treatment and those without NSVT who have not undergone antiarrhythmic therapy. There was a trend towards a higher overall and sudden mortality rate in patients with NSVT treated with other antiarrhythmic drugs vs patients with NSVT treated with amiodarone, but due to the small size of the first group no significant difference could be calculated. Assuming NSVT as a potential prognostic marker for sudden death, amiodarone treatment may have exerted a beneficial effect in these patients, but this statement is only a presumption due to the limitations of our study. The disappearance of NSVT during amiodarone treatment is not predictive of a reduced rate in sudden death, so that the potential effect of the drug does not appear to be related to the suppression of NSVT at Holter monitoring.