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.