Shibuya J, et al. - Using optical coherence tomography (OCT), researchers studied coronary culprit lesion morphologies in order to gain clarity regarding the mechanisms driving the observed trend of worse outcomes in patients diagnosed with acute coronary syndrome (ACS) during winter. Patients admitted with ACS in winter (W-ACS; n=390) and in other seasons (O-ACS; n=1027) were retrospectively compared for characteristics and outcomes. In patients who were analyzed with OCT (173 patients in W-ACS and 450 in O-ACS), angiography and OCT results were interpreted. In patients diagnosed with ACS during winter, worse angiographic results, as well as less plaque erosion (more plaque rupture or calcified nodules) at the culprit lesions on OCT, were evident, which could be partly related to worse cardiac mortality within two years.