MIC Trial: Metoprolol in Patients with Mild to Moderate Heart Failure: Effects on Ventricular Function and Cardiopulmonary Exercise Testing

UNLABELLED: Beta-blocker therapy results in a functional benefit in patients with heart failure (CHF) due to idiopathic dilated cardiomyopathy (DCM). This study assessed if similar effects were observed in patients with ischemic heart disease (CAD), NYHA II-III after 6 months of therapy with metoprolol. METHODS AND RESULTS: Fifty-two patients with CHF secondary to DCM (26 patients) and CAD (26 patients) and a left ventricular ejection fraction (EF)<40% were enrolled in the placebo-controlled study. The study medication was titrated over 6 weeks, the mean final dosage was 135 mg/day. Three patients died due to cardiogenic shock, two received placebo and one metoprolol. Eight patients did not complete the study due to non-compliance. Metoprolol significantly reduced heart rate at rest and after submaximal and maximal exercise. Vo(2)-max and Vo(2)-AT as well as the 6-min walk test improved significantly after metoprolol treatment. There was a significant increase in EF at rest (27.3-35. 2%), submaximal (28.5-37.7%) and maximal exercise (28.7-40.9%) in the metoprolol-treated patients. No differences were found between patients with CAD and DCM. We also observed reduced left ventricular volumes. CONCLUSION: The additional therapy with metoprolol improved cardiac function and the cardiopulmonary exercise capacity in patients with CHF.