Newer observations in seasonal behaiour of Acute coronary syndrome

Objectives. This observational study sought to determine whether incidence of acute myocardial infarction (AMI) admitted in our institution are varied by season.Background. The existence of circadian variation in the onset of AMI is well established. Examination of this periodicity has led to new insights into pathophysiologic triggers of atherosclerotic plaque rupture. Although a seasonal pattern for mortality fromAMI has been previously noted, it remains unclear whether the occurrence of AMI also displays a seasonal rhythmicity. Documentation of such a pattern may foster investigation of newpathophysiologic determinants of plaque rupture and intracoronary thrombosis.Methods. We analyzed the number of cases of AMI reported to our institution during the period jan 2005 to dec 2009.Data were normalized so that seasonal occurrence of AMI wasreported according to a standard 90-day length. Seasons were divided into winter (jan-mar),summer(apr-jun),monsoon(julsep),postmonsoon(oct-dec) as classified by Indian meterolgy department . Data were also collected on monthly basis.Results. A total of 7548 cases of AMI were analyzed during the study period of which 5503(73) were males and 2045 (27) were females.No seasonal variation in pattern of myocardial infarction noted in this study. however complication of MI and mortality were more during summer season.Myocardial infarction associated with stroke was also more during summer months. The same seasonal pattern was seen in men and women, in different ageThis pattern was seen in all subgroups analyzed groups. In-hospital case fatality rates for AMI followed a seasonal pattern,with a peak in summer.Conclusions. The present results suggest that there is no important seasonal variation in the occurrence of AMI in our institution.however complication and mortality showed marked peak during summer month with nadir during Unlike the large ranges in cold or hot weather found in temperate regions,the warm climate of subtropical region does not affect frequency of AMI. There is no specifc differnce in the incidence and outcome of STEMI and NSEMI with refernce to seasons.