Bisoprolol, but not verapamil, eases peak oxygen consumption in nonobstructive HCM

Peak oxygen consumption (pVO₂) in patients with nonobstructive hypertrophic cardiomyopathy (HCM) is reduced following treatment with the beta-blocker bisoprolol but remains unchanged with the calcium-channel blocker verapamil, reports a study.

Moreover, significant differences in exercise response, structural changes, myocardial function, symptoms, and biomarkers have been observed.

Thirty-two patients (mean age 54 years, 34 percent women) with nonobstructive HCM and ≥1 marker of disease severity (NYHA functional class ≥II, N-terminal pro–B-type natriuretic peptide [NT-proBNP] >300 ng/L, or documented nonsustained ventricular tachycardia) were analysed.

The pVO₂ was 25.7 mL/kg/min with bisoprolol, 28.2 mL/kg/min with verapamil, and 28.7 mL/kg/min with placebo, with adjusted mean differences in pVO₂ of ‒1.8 mL/kg/min for bisoprolol vs verapamil (p=0.013), ‒2.5 mL/kg/min for bisoprolol vs placebo (p=0.002), and ‒0.7 mL/kg/min for verapamil vs placebo (p=0.990).

Compared with placebo, the peak heart rate was lower with bisoprolol (‒37 beats/min; p<0.001) and with verapamil (‒17 beats/min; p<0.001). Both bisoprolol and verapamil did not change the oxygen consumption at anaerobic threshold or the minute ventilation/CO₂ production slope.

On the other hand, verapamil improved the global longitudinal strain (‒1.1 percent; p=0.001), but bisoprolol did not (‒0.6 percent; p=0.263), relative to placebo.

Treatment with bisoprolol, however, resulted in reduced Kansas City Cardiomyopathy Questionnaire Overall Summary Score (KCCQ-OSS; −6.6 points; p=0.001), increased NT-proBNP (165 ng/L; p=0.006), increased left atrial volume index (LAVI; 13.0 mL/m²; p<0.001), and increased tricuspid regurgitation (TR) pressure gradient (4.3 mm Hg; p=0.049) compared with placebo.

Furthermore, treatment with verapamil did not change KCCQ-OSS (‒2.3 points; p=0.668), LAVI (5.2 mL/m²; p=0.194), or TR pressure gradients (1.1 mm Hg; p=1.000) but reduced NT-proBNP (‒177 ng/L; p<0.001) relative to placebo.

Neither bisoprolol nor verapamil change the NYHA functional classification of patients.

“This study provides new insights into the mechanisms of these drugs that might be taken into consideration in management of nonobstructive HCM,” the investigators said.