β Blockers for Prevention of Exercise-Induced Left Ventricular Outflow Tract Obstruction in Patients With Hypertrophic Cardiomyopathy

Abstract

Whether treatment with β blockers (BBs) is of benefit to patients with hypertrophic cardiomyopathy (HC) and provocable outflow obstruction (with none or with only mild heart failure symptoms) is largely unresolved. Thus, we prospectively studied 27 patients with HC (age 36 ± 15 years; 81% men) with New York Heart Association class I or II, without obstruction at rest, but with exercise-induced left ventricular outflow tract (LVOT) gradient of ≥ 30 mm Hg. Patients underwent exercise echocardiography at baseline and after treatment with nadolol (n = 18; 40 to 80 mg/day) or bisoprolol (n = 9; 5 to 10 mg/day), according to a prespecified protocol. Without the BBs, the postexercise LVOT gradient was 87 ± 29 mm Hg and >50 mm Hg in 25 patients (93%). After a 12 ± 4-month period of BB treatment, the postexercise LVOT gradient had decreased to 36 ± 22 mm Hg (p <0.001) and was virtually abolished (to 0 or <30 mm Hg) in 14 patients (52%), substantially blunted (≥ 20 mm Hg reduction) in 9 (33%), and unchanged in only 4 (15%). Severe postexercise obstruction (range 58 to 80 mm Hg) persisted in 6 patients (22% compared to 93% without BBs; p <0.001). Nonresponders (residual postexercise gradient of ≥ 30 mm Hg with BBs) were characterized by an increased body mass index (hazard ratio 2.03/1 kg/m(2), 95% confidence interval 1.2 to 3.4; p <0.05). In conclusion, in patients with HC with mild or no symptoms, treatment with BBs can prevent the development of LVOT obstruction triggered by physiologic exercise. These findings provide a rationale for the novel strategy of early prophylactic pharmacologic treatment with standard, well-tolerated doses of BBs in physically active patients with provocable gradients, aimed at effective prevention of the hemodynamic burden associated with dynamic obstruction.

Hypertrophic Cardiomyopathy

“…Beta adrenergic receptor blockers, without intrinsic sympathetic activity, were first used in the treatment of HCM in the 1960s 227–229 , and have, since then, remained the cornerstone of pharmacological treatment of symptomatic patients. They are effective in the relief of ischemic chest discomfort and may attenuate exercise-induced LVOT obstruction and resulting dyspnea as well 230 .…”

Prognostic role of stress echocardiography in hypertrophic cardiomyopathy: The International Stress Echo Registry

“…In fact, Nistri et al [25] found that most of the patients with HCM exhibited a reduction in left ventricular outflow tract obstruction with beta-blockers therapy treatment.…”

Almanac 2014: cardiomyopathies

“…There have been few developments in therapy since the last Almanac, but early prophylactic β-blocker therapy in physically active patients (NYHA 1 and 2) with provokable LVOTO has been shown to be effective in reducing outflow gradients during physiological exercise 17. Another study has confirmed the additive benefit of disopyramide in therapy of symptomatic patients with obstruction resistant to initial therapy with β-blocker or verapamil 18…”