Verapamil therapy in infants with hypertrophic cardiomyopathy

We sought to evaluate the saftey and efficacy of acure and chronic treatment with verapamil infanta with hypertrophic cardimyopathy. Prior studies have shown an improvement in adluts with hypertrophiuc cardiomyophathy who were treated with verapamil. Acutely, it reduced the degree of left ventricular outflow tract abstruction. Chronic therapy was associated with an improvement in sysmptoms ans incresed long-term survial. To date, no data are available on the efficacy of this drug in infants with hypertrophic cardiomyopathy. We evaluated prospectively the safety and efficacy of verapamil in infants. The acute and chronic effects of verapamil on infants with an echocardiographic diagnosis of hypertrophic cardiomyopathy were evaluated at a single institution between 1980 and 1994, with long-term follow-up available until 1996. Acute effects of an intravenous bolus of 0.1 mg/kg and infusion at 0.007 mg/kg/min were evaluated, where possible, in the cardiac catheterization laboratory. Oral verapamil at 3–5 mg/kg/day was started after catheterization. Follow-up included serial clinical, echocardiographic and Holter monitoring. A total of 22 patients were studied, 17 having a presumed diagnosis of primary hypertrophic cardiomyopathy including three with Noonan's syndrome. Acute infusion of the drug was well tolerated by all, without adverse electrophysiological effects. Haemodynamic effects were consistent with a negative inotropic action with significant falls in cardiac index (4.6±1.2 to 4.1±0.9 l/min/m2), systolic blood pressure (88±16 to 82±14 mmHg) and gradient across the left ventricular outflow tract (nine patients 48.2±30.4 to 28.4±24.1 mmHg). End-diastolic pressure was unchanged (14.0±6.8 to 13.9±4.7 mmHg). Three patients with primary hypertrophic cardiomyopathy died (two while being treated). In the group with primary hypertrophic cardiomyopathy continuing with long-term treatment, follow-up revealed regression in two, progression in three (two died) and stability in 10. For those treated, there was a trend towards improvement in clinical status. Verapamil is well tolerated acutely in infants with hypertrophic cardiomyopathy. The outcome was considerably better in these patients compared with prior reports, though careful long-term assessment is needed.