Previous reports have suggested Takotsubo Cardiomyopathy (TTC) to have higher incidence in spring and summer months with peak noted from April to July. However, there are some smaller studies that show higher incidence during the winter months. To date, there has been no study looking at this seasonal trend using a large patient population. To address this gap in evidence, we analyzed the seasonal variation of TTC in the United States from 2009 to 2011 using data from the Nationwide Inpatient Sample, Healthcare Cost and Utilization Project, Agency for Healthcare Research and Quality. We identified cases of TTC using International Classification of Disease, Ninth Revision, Clinical Modification . A total of 10,989 patients with TTC were identified for the study using previously published inclusion and exclusion criteria ( Supplementary Figure 1 ).
Our results show that the peak of TTC admission occurs during the month of September (12.36 cases per 100,000 admissions). There were increased admissions during fall compared with winter months (n = 2,953 vs n = 2,454), which was statistically significant (p = 0.04). Similarly, there were increased admissions during summer compared with winter months (n = 2,928 vs n = 2,454), which showed trend towards statistical significance (p = 0.05; Figure 1 ). We observed increase in the number of admissions from April to September ( Figure 2 ), with a decreasing trend during the winter months as previously reported by Deshmukh et al. However, compared with their study, our study shows that peak occurs during the month of September rather than July. Because we analyzed TTC admissions for 3 years compared with just a single year, with larger patient population, our study is likely to be more reflective of the actual pattern. Interestingly, seasonal variation was far less significant in the south and west regions of the United States, where seasonal temperature variations are less extreme ( Supplementary Figure 2 ).
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