Circadian onset and prognosis of myocardial infarction with non-obstructive coronary arteries (MINOCA)

Background Many acute cardiovascular events such as myocardial infarction (MI) follow circadian rhythms. Myocardial infarction with non-obstructive coronary arteries (MINOCA) is a newly noticed entity with limited data on onset pattern and its impact on prognosis. Material and methods In this observational study of Swedish MINOCA patients registered in the SWEDEHEART registry between 2003-2013 and followed until December 2013 we identified 9,092 unique patients with MINOCA out of 199,163 MI admissions in total. Incidence rate ratios (IRR) were calculated for whole hours, parts of the day, weekdays, months, seasons and major holidays. Results The mean age was 65.5 years, 62.0% were women and 16.6% presented with STEMI. The risk for MINOCA proved to be most common in the morning (IRR = 1.70, 95% CI [1.63-1.84]) with a peak at 08.00 AM (IRR = 2.25, 95% CI [1.96-2.59]) and on Mondays (IRR = 1.28, 95% CI [1.18-1.38]). No altered risk was detected during the different seasons, the Christmas and New Year holidays or the Swedish Midsummer festivities. There was no association between time of onset of MINOCA and short-or long-term prognosis. Conclusion The onset of MINOCA shows a circadian and circaseptan variation with increased risk at early mornings and Mondays, similar to previous studies on all MI, suggesting stress related triggering. However, during holidays were traditional MI increase, we did not see any increase for MINOCA. No association was detected between time of onset and prognosis, indicating that the underlying pathological mechanisms of MINOCA and the quality of care are similar at different times of onset but triggering mechanism may be more active early mornings and Mondays.