Increased risk of congestive heart failure among infarctions with nighttime onset

Background The onset of acute myocordial infarction varies by time of day, with a peak in the morning and a trough at night. Whether infarct-related complications differ by the timing of the infarction is unknown. Methods and Results In the Determinants of Myocardial Infarction Onset study, we performed chart reviews and Face-to-face interviews with 3625 patients with acute myocardial infarction. We assessed the time of onset of symptoms, the presence of ventricular tachycardia or congestive heart failure, and peak creatine kinase levels (in 1043 patients). We Found significant circadian variation in the risk of congestive heart failure (P = .001). The risk dropped from 17% for infarctions that began between 6 PM and midnight to 10% for infarctions that began between 6 AM and noon. Adjustment for differences in the time from symptom onset to presentation for care and use of thrombolytic agents did not change the results, We found no circadian variation in the risk of ventricular tachycardia or in peak creatine kinase levels. Conclusions The risk of congestive heart failure is highest among infarctions that begin at night. Further research may clarify whether this reflects differences in the pathophysiologic characteristics of infarction or the quality of medical care provided for daytime and nighttime infarctions.