Relation Between Time of Symptom Onset of ST‐Segment Elevation Myocardial Infarction and Patient Baseline Characteristics: From the National Cardiovascular Data Registry

BACKGROUND: The presence of a morning excess of ST-segment elevation myocardial infarction (STEMI) has been observed. The relation between patient characteristics and timing of STEMI may provide insight into the biological processes responsible for this phenomenon. HYPOTHESIS: Patient baseline characteristics will vary with timing of STEMI. METHODS: We performed an analysis using a large national registry of unselected patients with STEMI (N=45,218). Patients were categorized by time of symptom onset: early (6 am-2 pm), late day (2 pm-10 pm), and overnight (10 pm-6 am) then evaluated for variations in characteristics. RESULTS: A circadian variation in the timing of symptom onset of STEMI was observed (early 41%, late day 32%, and overnight 26%, P<0.001). Circadian variations in factors known to alter timing of events were seen, including lower rates of home β-blocker use, smoking, and diabetes, with early onset of STEMI symptoms. In addition, patients in the 6 am to 2 pm subgroup were more likely older, white race, and male, with higher rates of home aspirin use and lower rates of obesity. Higher rates of coexisting cardiovascular disease, including prior heart failure, 3-vessel coronary artery disease, and depressed left ventricular ejection fraction, were observed in the overnight group. More robust antiplatelet therapy with home clopidogrel use was not associated with a change in the timing of events. CONCLUSIONS: A morning excess of STEMI continues to exist and represents a potential target for preventative strategies. Patient baseline characteristics vary with the onset of STEMI and may reflect a physiologic relationship between these factors and the timing of events.