Effect Of Adrenergic β-blockade On Left Ventricular Function In Patients With Acute Myocardial Infarction

Objective To investigate the effect of three different dosages of metoprolol on left ventricular systolic function in the patients of acute myocardial infarction.Methods 71 patients with acute myocardial infarction were divided randomly into four groups as follows: control group and three different dosages groups of metoprolol(25mg,50mg and 100mg,respectively).The date of cardiac function were measured by two-dimensional Doppler echocardiography, while heart rate ,blood pressure and the clinical symptom were also recorded at baseline,3 and 6 months after admission.Results At 6 months after admission, The changes of left ventricular(LV)systolic function and NYHA class improved in 100mg-group ,as reflected by the increased LV ejection fraction[ (54±10)% vs (46± 8)%;p<0.05] , decreased LV end systolic volume[ (31 ±14)ml vs(43± 13)ml;p<0.05],anddecreased LV end distolic volume[ (69 ± 15)ml vs (81 ± 16)ml;p<0.05]. There was no significant differences compared with control group at 3 months after admission. The mean dose of metoprolol in 100-mg group was 90± 15mg/day.Conclusion Long-term treatment with metoprolol seems to improve left ventricular function after acute myocardial infarction.The recovery of LV systolic function was seen at up to 6 months of treatment. Among the three different dosages used in this study , 100mg- group showed biggest improvement in left ventricular systolic function. This suggested that enough β -adrenergic blockade can block β -acepter and develop benefit effection on heart.