Objectives: This study was performed to investigate exercise hemodynamic status in a double-blind, placebo-controlled trial and was a substudy in the Metoprolol in Dilated Cardiomyopathy Trial.
Background: Previous open studies have shown beneficial effects on exercise hemodynamic status after beta-adrenergic blocking agent therapy in patients with congestive heart failure.
Methods: The study included 41 patients with idiopathic dilated cardiomyopathy with ejection fraction < 0.40 (metoprolol, 20 patients; placebo, 21 patients) whose hemodynamic status was investigated at rest and during supine submaximal exercise, at baseline and after 6 and 12 months of treatment. Myocardial metabolism was evaluated in a subset of 19 patients.
Results: Metoprolol-treated patients responded favorably, as expressed by improved exercise cardiac index ([mean +/- SD] placebo 4.8 +/- 1.6 to 4.7 +/- 1.8 liters/min per m2, metoprolol 4.3 +/- 1.1 to 5.4 +/- 1.9 liters/min per m2, p = 0.0001) and stroke work index (placebo 44 +/- 20 to 41 +/- 27 g.m/m2, metoprolol 35 +/- 16 to 58 +/- 28 g.m/m2, p < 0.0001). Exercise systolic arterial pressure increased (placebo 161 +/- 25 to 151 +/- 23 mm Hg, metoprolol 155 +/- 29 to 165 +/- 37 mm Hg, p = 0.0003) as well as exercise oxygen consumption index (placebo 463 +/- 194 to 474 +/- 232 ml/min per m2, metoprolol 406 +/- 272 to 507 +/- 298 ml/min per m2, p = 0.045). There was a significant increase in exercise duration in the metoprolol group (63 +/- 38 s) compared with the placebo group (-24 +/- 42 s) (p = 0.01). Net myocardial lactate extraction increased in the metoprolol group, suggesting less myocardial ischemia (placebo 17 +/- 22 to 9.5 +/- 6.4 mmol/min, metoprolol -32 +/- 100 to 42 +/- 45 mmol/min, p = 0.03). Peripheral levels of norepinephrine tended to decrease at rest and during exercise, whereas myocardial net spillover was unchanged.
Conclusions: Metoprolol improved hemodynamic status in patients with dilated cardiomyopathy at rest and had a more pronounced effect during exercise. These positive effects were achieved along with improved or stable myocardial metabolic data.