Season and myocardial injury in patients with ST-segment elevation myocardial infarction: A cardiac magnetic resonance imaging study

Background
Little is known about the causality and pathological mechanism underlying the association of seasonal variation with myocardial injury in patients with ST-segment elevation myocardial infarction (STEMI).
Objective
We evaluated the association of seasonal effect with myocardial injury using cardiovascular magnetic resonance (CMR) imaging in STEMI patients undergoing primary percutaneous coronary intervention (PCI).
Methods
In 279 patients undergoing primary PCI for STEMI, CMR was performed for a median of 3.3 days after the index procedure. Of these, STEMI occurred in 56 patients in the winter (Winter group), 80 patients in the spring (Spring group), 76 patients in the summer (Summer group), and 67 patients in the autumn (Autumn group), respectively. We compared myocardial infarct size, extent of area at risk (AAR), myocardial salvage index (MSI) and microvascular obstruction (MVO) area as assessed by CMR according to the season in which STEMI occurred.
Results
In the CMR analysis, the myocardial infarct size was not significantly different among the Winter group (21.0 ± 10.5%), the Spring group (19.6 ± 11.5%), the Summer group (18.6 ± 10.6%), and the Autumn group (21.1 ± 11.3%) (P = 0.475). The extent of AAR, MSI, and MVO areas were similar among the four groups. In the subgroup analysis, myocardial infarct size, extent of AAR, MSI, and MVO were not significantly different between the Harsh climate (winter + summer) and the Mild climate (spring + autumn) groups.
Conclusions
Seasonal influences may not affect advanced myocardial injury in STEMI patients undergoing primary PCI.