The impact of circadian variation on 12-month mortality in patients with acute myocardial infarction.
OBJECTIVE
Although circadian variation in the onset of acute myocardial infarction (AMI) has been reported in a number of studies, not much is known about the impact of circadian variation on 12-month mortality. The aim of this study was to investigate the impact of circadian variation on 12-month mortality in patients with AMI.


METHODS
Eight hundred ninety two patients (mean age 67±12; 66.1% men) with AMI who visited Kyungpook National University Hospital from November 2005 to December 2007 were included in this study. Patients were divided into groups based on four 6-hours intervals: overnight (00:00-05:59); morning (06:00-11:59); afternoon (12:00-17:59) and evening (18:00-23:59).


RESULTS
Kaplan-Meier survival curves showed 12-month mortality rates of 9.6%, 9.1%, 12.1%, and 16.7% in the overnight, morning, afternoon, evening-onset groups, respectively (p=0.012). Compared with the morning-onset AMI group, the serum creatinine levels (p=0.002), frequency of Killip class ≥3 (p=0.004), and prescription rate of diuretics (p=0.011) were significantly higher in the evening-onset AMI group, while the left ventricular ejection fraction (p=0.012) was significantly lower. The proportion of patients who arrived in the emergency room during routine duty hours was significantly lower in evening-onset groups irrespective of the presence or absence of ST-segment elevation (p<0.001). According to univariate analysis, the 12-month mortality rate in the evening group was significantly higher compared to the morning group (hazard ratio 1.998, 95% confidence interval 1.196 to 3.338, p=0.008).


CONCLUSIONS
Patients with evening-onset AMI had poorer baseline clinical characteristics, and this might affect the circadian impact on 12-month mortality. Further studies are needed to clarify the role of circadian variation on the long-term outcome of AMI.
Department of Internal Medicine, Kyungpook National University Hospital, Daegu, Korea.
Myung Hwan
MH
Bae
Hyeon Min
HM
Ryu
Jang Hoon
JH
Lee
Ju Hwan
JH
Lee
Yong Seop
YS
Kwon
Sang Hyuk
SH
Lee
Dong Heon
DH
Yang
Hun Sik
HS
Park
Yongkeun
Y
Cho
Shung Chull
SC
Chae
Jae-Eun
JE
Jun
Wee-Hyun
WH
Park
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