Date Published: February 8, 2019
Publisher: Public Library of Science
Author(s): Ik Hyun Park, Woo Jin Jang, Hyun Kyu Cho, Ju Hyeon Oh, Woo Jung Chun, Yong Hwan Park, Mirae Lee, Young Bin Song, Joo-Yong Hahn, Seung-Hyuk Choi, Sang-Chol Lee, Hyeon-Cheol Gwon, Yeon Hyeon Choe, Olivia Manfrini.
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).
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).
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.
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.
Seasonal influences may not affect advanced myocardial injury in STEMI patients undergoing primary PCI.
Seasonal variations influence the incidence of acute myocardial infarction (MI) . Previous studies have reported that acute MI occurs more frequently in cold and hot weather, and that ambient temperature may play an important role in the development of acute MI . Evidence in support of this data considers various mechanisms, such as a potential effect of temperature on platelet activation, blood viscosity, and vascular resistance [2–4]. Kloner et al.  investigated seasonal variations in myocardial perfusion using enzymatic infarct size as estimated by the cumulative release of cardiac enzymes and reported that smaller infarct size was observed in the summer, but the causality and pathological mechanisms underlying the association of seasonal effects with myocardial injury remained unclear. Cardiovascular magnetic resonance (CMR) imaging can precisely assess the extent of myocardial injury and salvaged myocardium in acute MI patients [6,7]. We evaluated the association between seasonal variation and myocardial injury as assessed by CMR imaging in STEMI patients undergoing primary PCI.
This study was approved by the institutional review board of Samsung Medical Center and Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, respectively and all subjects provided written informed consent to participate in this study.
We investigated the association between seasonal variation and myocardial injury using CMR imaging in STEMI patients treated with primary PCI. The main finding of our study was that there was no significant difference of myocardial infarct size between winter, spring, summer, and autumn; furthermore, the extent of AAR, MSI, and MVO area were similar among the four seasons. Between harsh climates (winter and summer season) and mild climates (spring and autumn season), the nature of myocardial injury as assessed by CMR was not significantly different either. To the best of our knowledge, this is the first study to evaluate seasonal variations associated with myocardial injury as determined by CMR imaging data in STEMI patients. Our findings corresponded well with those of earlier studies that established an absence of seasonal effect on myocardial infarct size in acute MI patients . Therefore, the results of our study may provide the causality and pathological mechanisms for the absence of seasonal variation in myocardial injury.
Seasonal effects could influence the incidence of acute MI, especially in the winter or summer; however, these are not associated with a larger extent of myocardial edema, less myocardial salvage, or greater myocardial infarct size as assessed by CMR imaging. Based on our study, seasonal variation may not affect advanced myocardial injury in STEMI patients undergoing primary PCI. Further investigation with potential therapeutic implications of these findings should be considered.