Effect of metoprolol on rest and exercise left ventricular systolic and diastolic function in idiopathic dilated cardiomyopathy

Objective To further characterize the effects of heart rate on systolic and diastolic function in patients with idiopathic dilated cardiomyopathy (IDCM), it was hypothesized that the relationship between heart rate and left ventricular systolic and diastolic function would be unaltered by β-blockade and exercise. Methods Eighteen patients with IDCM were randomized in a double-blind manner to receive either metoprolol or placebo for 3 months. Before and after 3 months of therapy, resting and exercise radionuclide left ventriculograms were obtained for assessment of left ventricular systolic and diastolic function. Results At rest, metoprolol treatment compared with placebo was associated with decreased heart rate (61 ± 11 vs 99 ± 10 beats/min, P < .0001) and an increased left ventricular ejection fraction (0.32% ± 0.10% vs 0.17% ± 0.08%, P = .01). With exercise, metoprolol compared with placebo caused a decreased heart rate (86 ± 18 vs 126 ± 43 beats/min, P = .056), an increase in left ventricular ejection fraction (0.32% ± 0.14% vs 0.19% ± 0.07%, P = .052), a longer time to peak filling rate (164 ± 21 vs 127 ± 17 ms, P = .005), and a decreased peak filling rate (5.41 ± 1.71 vs 8.40 ± 1.85 stroke volumes/s, P = .012). Before β-blockade, heart rate at rest was negatively correlated to left ventricular ejection fraction and positively correlated to peak filling rate; with exercise, the relationships of heart rate to left ventricular ejection fraction and peak filling rate were similar. After metoprolol treatment, the heart rate continued to have a similar positive correlation with the peak filling rate at rest and with exercise. Conclusions In patients with IDCM, systolic and diastolic cardiac function, at rest and with exercise, was related to heart rate. After β-blockade, at rest and with exercise, diastolic function continued to be related to heart rate. (Am Heart J 2001;141:e5.)