Outcome of primary angioplasty for acute myocardial infarction during routine duty hours versus during off-hours

Objectives We sought to investigate the impact of circadian patterns in the onset of acute myocardial infarction (AMI) on the practice of primary angioplasty. Background A circadian variation in the time of onset of AMI with a peak in the morning hours has been described. Methods We studied 1,702 consecutive patients with acute ST-segment elevation myocardial infarction treated with primary angioplasty. We observed circadian variation in frequency of symptom onset, hospital admission, and first balloon inflation. Circadian patterns of symptom onset, hospital admission, and balloon inflation are similar. Results A majority of patients have symptom onset (53%), hospital admission (53%), and first balloon inflation (52%) during routine duty hours (0800 to 1800 h). There were no differences in baseline clinical characteristics or treatment delays between routine duty hours and off-hours patients. Hospital admission between 0800 and 1800 was associated with an angioplasty failure rate of 3.8%, compared with 6.9% between 1800 and 0800, p < 0.01. Thirty-day mortality was 1.9% in patients with hospital admission between 0800 and 1800, compared with 4.2% in patients with hospital admission between 1800 and 0800, p < 0.01. Conclusions Circadian variations may have a profound effect on the practice of primary angioplasty. A majority of patients are treated during routine duty hours. Patients treated during off-hours have a higher incidence of failed angioplasty and consequently a worse clinical outcome than patients treated during routine duty hours.