BACKGROUND: Left ventricular (LV) diastolic function predicts and correlates with exercise capacity. Beta-blockers improve exercise capacity and LV diastolic function in patients with severe LV systolic dysfunction in dilated cardiomyopathy. However, information on the effect of metoprolol XL on exercise capacity in relation to LV diastolic function in patients with mild to moderate LV systolic dysfunction after acute myocardial infarction is limited.
METHODS: In a randomized, double-blind, placebo-controlled study of 77 patients, a subgroup of 59 patients with mild to moderate LV systolic dysfunction after acute myocardial infarction were given metoprolol XL (n = 29) or placebo (n = 30). The effects of metoprolol XL on exercise capacity in relation to effects on LV diastolic filling were studied. Two-dimensional Doppler echocardiography and maximal symptom limited bicycle test were performed on days 5 through 7 and after 3 months.
RESULTS: Maximal exercise capacity increased in the metoprolol XL group (124 +/- 30 W vs 135 +/- 29 W) compared with placebo (125 +/- 31 W vs 126 +/- 34 W) (P <.01). E/A ratio decreased, A peak velocity increased, reverse pulmonary flow decreased, and deceleration time was significantly prolonged in the metoprolol XL group. A significant correlation was found between the changes of deceleration time (metoprolol XL: rho = 0.69, P <.0001; placebo: rho = 0.31, P = not significant) and A peak velocity (metoprolol XL: rho = 0.71, P <.0001; placebo: rho = -0.15, not significant) in relation to changes of exercise capacity.
CONCLUSION: Metoprolol XL increases exercise capacity after 3 months, and this change seems related to improvement of LV diastolic filling after acute myocardial infarction.