Severity of arrhythmias and extent of hypertrophy in hypertrophic cardiomyopathy.

To evaluate the relationship between the extent of left ventricular hypertrophy and ventricular or atrial arrhythmias, 77 patients with hypertrophic cardiomyopathy underwent two-dimensional echocardiography and 24-hour Holter monitoring. Antiarrhythmic treatment was discontinued before the study. Hypertrophy was septal in 33 patients, "extensive" (i.e., involving the septum and free wall) in 38 patients, and predominantly apical in six patients. Lown grade I and II ventricular arrhythmias were detected in 37% of patients, grade III in 21%, and grade IV in 29%. Atrial extrasystoles were seen in 52% of patients and chronic atrial fibrillation in 13%. More serious ventricular arrhythmias (Lown grades III and IV) occurred significantly more frequently in patients with extensive than in those with only septal hypertrophy (22/38 vs 11/33; p less than 0.001); similarly, chronic atrial fibrillation occurred more commonly in those with extensive hypertrophy (9/38 vs 1/33; p less than 0.01). During a mean follow-up period of 2.6 years, three patients died. All had a pattern of extensive hypertrophy. Two of them had ventricular tachycardia and the third had chronic atrial fibrillation. Results of this study suggest that an echocardiographic finding of extensive hypertrophy represents a useful marker for detecting patients at increased risk for serious ventricular and atrial arrhythmias.