RESUMO
Background and Objective: Diurnal variation in the onset of acute myocardial infarction with a peak in the morning has been demonstrated. Few data are available concerning about the left ventricular systolic dysfunction according to the infarct time. Regarding importance of onset of heart failure following acute myocardial infarction, this study was done to survey the effect of the time of acute myocardial infarction on left ventricular systolic dysfunction
Methods: This prospective study was performed on 100 patients with acute myocardial infarction [AMI]. Left ventricular systolic dysfunction [LVSD] was defined by echocardiography when ejection fraction [EF] was less than 55%
Findings: Of these patients, 72 had EF<55% and 37% of them experienced myocardial infarction between 6 am and 5:59 pm [Group 1] and 63 experienced their AMI between 6 pm and 5:59 am [Group 2]. Left ventricular EF less than 55% occurred in 22 [59.5%] patients of group 1 compared with 50 [79.4%] in group 2 [P=0.04]. Mild, moderate and severe LVSD were also more frequent in group 2 patients [P=0.01]
Conclusion: The risk of mild, moderate and severe left ventricular systolic dysfunction after AMI is higher among infarctions that begin at night