READERS’ COMMENTS Seasonal and Regional Variation in Takotsubo Cardiomyopathy Previous reports have suggested Takotsubo Cardiomyopathy (TTC) to have higher incidence in spring and summer months with peak noted from April to July.1e3 However, there are some smaller studies that show higher incidence during the winter months.4 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).5 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 ¼ 2,953 vs n ¼ 2,454), which was statistically signiﬁcant (p ¼ 0.04). Similarly, there were increased admissions during summer compared with winter months (n ¼ 2,928 vs n ¼ 2,454), which showed trend towards statistical signiﬁcance (p ¼ 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.5 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). Although we observed that TTC is less common during the winter months as previously reported, our study highlights that the peak occurrence of TTC is
Figure 1. Cases of TTC per 100,000 admissions by season 2009 to 2011. ICD-9-CM ¼ International Classiﬁcation of Disease, Ninth Revision, Clinical Modiﬁcation.
Figure 2. Cases of TTC per 100,000 discharges by month 2009 to 2011.
different. The peak seems to be during the late summer months and early fall. This study further strengthens the evidence of opposite seasonal variation of other cardiovascular diseases such as myocardial infarction.6 Why these effects are more pronounced in regions of more seasonal temperature ﬂuctuation are matters for further study.
Supplementary Data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.amjcard. 2014.03.002. Madan Raj Aryal, MD Ranjan Pathak, MD Paras Karmacharya, MD Anthony A. Donato, MD Reading Health System, 6th Avenue and Spruce Street, West Reading, PA 19611 26 February 2014
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