Does metoprolol influence exercise haemodynamics in obstructive hypertrophic cardiomyopathy?

Exercise contributes to an abnormal risk in pulmonary capillary wedge pressure (PCWP), but is not affected by metoprolol, in patients with obstructive hypertrophic cardiomyopathy (HCM), results of a study have shown.

However, metoprolol treatment results in increased stroke volume (SV) at rest and peak exercise following changes in end-diastolic volume, left ventricular outflow tract (LVOT) gradient, and degree of mitral regurgitation.

Twenty-eight patients with obstructive HCM and New York Heart Association functional class ≥II were enrolled in this randomized, double-blind, placebo-controlled crossover trial. Participants were randomly assigned to initiate either metoprolol 150 mg or placebo for two consecutive 2-week periods.

The investigators carried out right-heart catheterization and echocardiography at rest and during exercise at the end of each treatment period. The difference in PCWP between peak exercise and rest served as the primary outcome.

No treatment effect on the primary outcome was seen between the two treatment groups (metoprolol vs placebo: 21 vs 23 mm Hg; p=0.12).

At rest, metoprolol was associated with a reduced heart rate (p<0.0001) and LVOT gradient (p=0.01), and with increased left ventricular end-diastolic volume (p=0.02) and SV (6.4 mL, 95 percent confidence interval [CI], 0.02‒17.7; p=0.049).

On the other hand, metoprolol correlated with a lower heart rate (p<0.0001), lower LVOT gradient (p=0.0005), lesser degree of mitral regurgitation (p=0.004), and increased SV (9 mL, 95 percent CI, 2‒15; p=0.008) during peak exercise.