Background: Beta-blockers improve survival and ventricular function in patients with heart failure. We evaluated the long-term persistence of metoprolol-induced improvement and its impact on prognosis in idiopathic dilated cardiomyopathy.
Methods: Two hundred and four of 586 patients enrolled in a registry on the natural history of idiopathic dilated cardiomyopathy survived 4 years without transplantation; 98 of them were on standard heart failure treatment, whereas 106 took metoprolol in addition. We analyzed the effects of treatment using beta-blockers in terms of changes in left ventricular ejection fraction (LVEF), NYHA functional class and left ventricular end-diastolic diameter index (LVEDDI) after 1, 2 and 4 follow-up years in order to elaborate an improvement score that was related to the subsequent outcome over 60 months after the 4-year follow-up visit.
Results: Greater LVEF increases and NYHA functional class and LVEDDI decreases were observed in patients submitted to metoprolol vs standard treatment at all stages of follow-up. Changes (delta vs baseline) for LVEF (p = 0.02), NYHA functional class (p = 0.0001) and LVEDDI (p = 0.004) were maximal during the first year (10 +/- 11 vs 6 +/- 12 units, -0.72 +/- 0.77 vs -0.23 +/- 0.81, -3.5 +/- 5 vs -1.6 +/- 3.5 mm), persisted at 2 (12 +/- 12 vs 8 +/- 12 units, -0.80 +/- 0.70 vs -0.37 +/- 0.87, -4.2 +/- 5 vs -2.3 +/- 4 mm) but showed a trend to decline at 4 years (11 +/- 12 vs 8 +/- 13 units, -0.54 +/- 0.90 vs -0.24 +/- 0.91, -4.3 +/- 5 vs -2.3 +/- 5 mm) of follow-up. Improvement at 4 years was associated with a better transplant-free survival (81 vs 52%, p = 0.0005, odds ratio 0.36, 95% confidence interval 0.18 to 0.74).
Conclusions: In idiopathic dilated cardiomyopathy, the more significant improvement in symptoms and left ventricular function and size, that is observed following treatment using metoprolol, translates into a better outcome. These benefits peak within the first 2 years of start of treatment but may begin to fade thereafter.