INTRODUCTION: ST-segment elevation myocardial infarction (STEMI) onset follows a circadian rhythm, yet data from large contemporary national registries remain limited, particularly regarding how onset time influences treatment delays and coronary pathology.
OBJECTIVES: To examine circadian patterns of STEMI onset and their impact on treatment delays, culprit vessel involvement, and periprocedural mortality.
PATIENTS AND METHODS: We retrospectively analyzed 153 543 STEMI patients from the Polish National PCI Registry (ORPKI) between 2014 and 2022. We examined the hourly distribution of symptom onset and its associations with patient characteristics, treatment delays, and infarct-related artery location.
RESULTS: STEMI onset showed pronounced circadian variation, peaking at 8:00 AM. Although the overall pattern was similar between sexes (P for interaction = 0.15), median onset time occurred significantly earlier in males than females (10:00 AM vs. 11:00 AM, P = 0.007). Nocturnal onset (e.g., 3:00 AM) was associated with substantially longer median pain-to-first-medical-contact times compared with daytime onset (180 vs. 90 minutes at 1:00 PM; P <0.001). We identified a novel opposing circadian rhythm for the infarct-related artery location: left anterior descending (LAD) artery identified as the infarct-related artery peaked during nocturnal hours with a nadir at noon, while right coronary artery (RCA) involvement demonstrated the inverse pattern (P <0.001). Despite delayed presentation, periprocedural mortality did not vary significantly by onset time.
CONCLUSIONS: This large nationwide cohort demonstrates that STEMI onset follows a robust circadian pattern significantly affecting system delays. The discovery of opposing circadian rhythms for LAD versus RCA involvement suggests that time of day influences not only STEMI triggering but also its pathophysiological manifestation.
