Predictive value of heart rate in dilated cardiomyopathy treated with metoprolol

Abstract

Predictive factors of a favourable response to beta-blocker therapy are still unknown and the role of heart rate remains controversial.

Aim: To investigate the relation between heart rate and the response to chronic metoprolol treatment in patients with dilated cardiomyopathy (DCM).

Methods: Ninety-eight consecutive patients with DCM, left ventricular ejection fraction (LVEF) < or = 0.40 and blood pressure < or = 140/90 mmHg were treated with metoprolol, associated with digitalis, diuretics and ACE-inhibitors. After 24 +/- 6 months, 48 patients (49%) were classified as "improved" on the basis of a clinical/instrumental score.

Results: Rest, mean 24-hour and maximal exercise heart rate were all significantly and directly related to the probability of improvement, but heart rate at rest, supine and in upright position, showed the highest predictive power. The relationship between heart rate and improvement with metoprolol appeared to be non-linear, with an increasing probability in patients with higher heart rate, but with a fall of the slope in cases with extreme tachycardia. By dividing our study population on the basis of the most important clinical variables, this complex relation was evident only in patients at a more advanced stage of the disease.

Conclusion: Our analysis confirms the strict relationship between heart rate and improvement with chronic metoprolol therapy in patients with DCM. This relation seems to be non-linear and is influenced by the severity of the disease.