BACKGROUND: Left ventricular (LV) systolic and diastolic function are known to be affected in the wake of a myocardial infarction (MI). beta-Adrenergic blocking agents have demonstrated improvement of LV systolic and diastolic function in patients with dilated cardiomyopathy and theoretically would have same beneficial effects in MI. beta-Adrenergic blocking agents are widely used in MI; however only few reports on changes of LV systolic and diastolic function during long-term treatment after acute MI are available.
METHODS: Two-dimensional and Doppler echocardiography were used to evaluate LV diastolic filling in 77 patients randomly assigned to placebo (n = 38) or metoprolol (n = 39). The patients were randomly assigned at day 5 to 7 (baseline) after acute MI and were treated for 12 months. LV diastolic filling was assessed by pulsed Doppler measurements of transmitral and pulmonary venous flow.
RESULTS: Mitral E-wave deceleration time was prolonged in the metoprolol group (baseline vs 12 months: 167 +/- 51 ms to 218 +/- 36 ms; P =. 01) versus the placebo group (baseline vs 12 months: placebo 174 +/- 46 ms to 189 +/- 41 ms), which implies a less restrictive filling of the LV in the metoprolol group. This was supported by a decrease of E/A ratio (baseline vs 12 months: placebo, 1.06 +/- 0.40 to 0.96 +/- 0.29; metoprolol, 1.09 +/- 0.33 to 0.80 +/- 0.21; P =.05) and prolongation of the isovolumetric relaxation time in the metoprolol treated group (baseline vs 12 months: placebo, 83 +/- 19 ms to 95 +/- 20 ms; metoprolol, 82 +/- 23 ms to 117 +/- 22 ms; P =.01). The difference between mitral A wave and pulmonary venous flow reversal duration was significantly changed during follow-up (baseline vs 12 months: placebo, 22 +/- 11 ms to 24 +/- 11; metoprolol, 11 +/- 21 to 32 +/- 17 ms; P =.02). Patients with normal LV filling pattern at baseline in the metoprolol group preserved a normal LV filling pattern during the study, and patients with restrictive LV filling pattern in the metoprolol group had a nonrestrictive LV filling pattern develop. Maximal or near maximal changes of the diastolic Doppler measurements occurred by 3 months of follow-up, whereas a significant increase in LV ejection fraction was noted after 12 months treatment with metoprolol.
CONCLUSIONS: Long-term treatment with the beta-blocking agent metoprolol seems to improve LV diastolic filling after acute MI. Less restrictive LV filling was noted during beta-blockade indicated by a significant prolongation of the mitral E deceleration time, which was predominantly noted in patients with restrictive LV filling. This observation might have prognostic implications because this LV filling pattern is known to be associated with poor outcome. The changes of LV diastolic filling occurred during the first 3 months, whereas systolic recovery was seen at up to 12 months of treatment.