I FLUENCE OF CIRCADIAN VARIATIONS ON ONSET AND IN-HOSPITAL OUTCOME OF FIRST ACUTE MYOCARDIAL INFARCTION

Abstract

Objective: To evaluate the influence of circadian variations on the onset and in-hospital outcome of first acute
myocardial infarction (AMI).

Materials And Methods: 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 6:01-12 hours, Group III 144(33.9%) patients presenting in 12:01-18
hours and Group IV comprised of 96(22.6%) patients having onset of AMI during 18:01-24 hours.
Cardiovascular risk factors and in-hospital outcome were compared between the groups by applying Chi
Square test.

Results: Two peaks of onset of symptom were observed, first between 12:01-18 hours 144(33.9%) patients
and the second between 6:01-12 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 II 7(5.9%) and 4(2.8%) in Group III p<0.485. Overall 201(47.3%)
patients received streptokinase therapy. Overall in-hospital mortality was 62(14.8%), mortality was higher
22(18.6%) in Group II, followed by 14(14.6% in Group IV, 19(13.2%) in Group III and 8(11.9%) in Group J
p<O.U3. Left ventricular failure was the common cause 45(l 0.6%) of in-hospital mortality.

Conclusion: The onset time of AMI has bimodal appearance with an early peak at 12:01-18 hours and a
second lesser peak at 6:01-12 hours. In-hospital mortality was higher in patients presenting between 6:01-12
hours because of more frequency of advanced kiIIip class at the time of presentation in this Group.