Influence of circadian variations on onset and in-hospital outcome of first acute myocardial infarction

ABSTRACT

To evaluate the influence of circadian variations on the onset and in-hospital outcome of first acute myocardial infarction [AMI]. After fulfilling the inclusion criteria 425 patients presenting with new onset acute myocardial infarction were studied. The study patients were divided into 4 groups according to time of onset of symptoms. Group I consisted of 67[15.8%] patients presenting during 0-6 hours interval, Group II 118[27.7%] patients presenting during 60l-12 hours, Group III 144[33.9%] patients presenting in 1201-18 hours and Group IV comprised of 96[22.6%] patients having onset of AM1 during 180l-24 hours. Cardiovascular risk factors and in-hospital outcome were compared between the groups by applying Chi Square test. Two peaks of onset of symptom were observed, first between 120l-18 hours 144[33.9%] patients and the second between 60l-12 hours 118[27.7%] patients. The trough was early morning time 0-6 hours when only 67[15.8%] patients had acute MI. Mean age of the study population was 54.5 +/- 12.3 years. There were 337[79.3%] males and 88[20.7%] females. There were 114[26.8%] diabetics, 138[32.5%] hypertensives and 215[50.6%] smokers. Majority of patients 168[39.5%] presented 3-6 hours after the onset of symptoms. Overall 100[23.5%] patients presented to the hospital within 3 hours of onset of symptoms. Overall 173[40.7%] patients had anterior wall myocardial infarction followed by Anterospetal wall myocardial infarction in 147[34.6%] patients. In Group IV patients there was more 9[6.3%] tendency of presenting in advanced Killip class followed by Group I1 7[5.9%] and 4[2.8%] in Group 111 p<0.485. Overall 201[47.3%] patients received streptokinase therapy. Overall in-hospital mortality was 62[14.5%], mortality was higher 22[18.6%] in Group 11, followed by 14[14.6% in Group IV, 19[13.2%] in Group III and 8[11.9%] in Group I p<0.113. Left ventricular failure was the common cause 45[10.6%] of in-hospital mortality. The onset time of AMI has bimodal appearance with an early peak at 120l-18 hours and a second lesser peak at 60l-12 hours. In-hospital mortality was higher in patients presenting between 60l-12 hours because of more frequency of advanced killip class at the time of presentation in this Group