Title:Beta-Blockers in Pediatric Hypertrophic Cardiomyopathies
Volume: 9
Issue: 2
Author(s): Ingegerd Ostman-Smith
Affiliation:
Keywords:
Beta-blocker, congestive heart failure, diastolic function, hypertrophic cardiomyopathy, Noonan's syndrome,
outflow obstruction, propranolol.
Abstract: Congestive cardiac failure accounts for 36% of childhood deaths in hypertrophic cardiomyopathy, and in infants
with heart failure symptoms before two years of age, the mortality is extremely high unless treatment with betareceptor
antagonists is instituted. The mechanism of heart failure is not systolic dysfunction, but rather extreme diastolic
dysfunction leading to high filling pressures.
Risk factors for development of heart failure are a generalized pattern of hypertrophy with a left ventricular posterior wallto-
cavity ratio >0.30, the presence of left ventricular outflow tract obstruction at rest, and the co-existence of syndromes in
the Noonan/Leopard/Costello spectrum. The 5-year survival of high-risk patients is improved from 54% to 93% by highdose
beta-blocker therapy (>4.5 mg/kg/day propranolol). The mechanism of the beneficial effect of beta-blockers is to improve
diastolic function by lengthening of diastole, reducing outflow-obstruction, and inducing a beneficial remodelling
resulting in a larger left ventricular cavity, and improved stroke volume. Hypertrophic cardiomyopathy is associated with
increased activity of cardiac sympathetic nerves, and infants in heart failure with hypertrophic cardiomyopathy show signs
of extreme sympathetic over-activity, and require exceptionally high doses of beta-blockers to achieve effective betablockade
as judged by 24 h Holter recordings, often 8-24 mg/kg/day of propranolol or equivalent.
Conclusion: Beta-blocker therapy is without doubt the treatment of choice for patients with heart failure caused by hypertrophic
cardiomyopathy, but the dose needs to carefully titrated on an individual basis for maximum benefit, and the dose
required is surprisingly large in infants with heart failure due to hypertrophic cardiomyopathy.
