Circadian variation in myocardial perfusion and mortality in patients with ST-segment elevation myocardial infarction treated by primary angioplasty

Background Little is known about whether the physiological factors that determine the circadian variation in ST-segment elevation myocardial infarction (STEMI) onset and thrombolysis efficacy may affect myocardial perfusion and long-term outcome of patients with STEMI treated with primary angioplasty. Methods Our study population consisted of 1548 consecutive patients with STEMI treated by primary angioplasty between April 1997 and October 2001. All clinical, angiographic, and follow-up data were collected. Results Most of the patients (65.2%) were treated at daytime (between 8 am and 8 pm). Patients treated between 1 pm and midnight had a lower prevalence of anterior infarction and longer door-to-balloon time, whereas the shortest ischemic time and the largest use of stent were observed in patients treated between midnight and 4 am Patients treated between 4 and 8 am showed the worst outcome in terms of myocardial perfusion, enzymatic infarct size, and 1-year outcome, whereas patients treated between 8 am and 4 pm had the best myocardial perfusion and lowest 1-year mortality rate. After correction for baseline confounding factors, the time of treatment (between 4 and 8 am) was still significantly associated with 1-year mortality (relative risk 1.92, 95% CI 1.13-3.26, P = .016). Conclusions This is the first study showing a significant relationship between the time of treatment, myocardial perfusion, and long-term mortality in patients with STEMI undergoing mechanical reperfusion.