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Selçuk Adabag, Mohammad Madjid, Alan Cheng, An attempt to reconcile the contrasting results of analyses on implantable cardioverter-defibrillator shocks during the pandemic, European Heart Journal, Volume 43, Issue 11, 14 March 2022, Page 1173, https://doi.org/10.1093/eurheartj/ehab378
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This commentary refers to the article ‘Ventricular arrhythmia burden during the coronavirus disease 2019 (COVID-19) pandemic’, by C.J. O’Shea et al., 2021;42:520–528, https://doi.org/10.1093/eurheartj/ehaa893 and the discussion piece ‘Cardiac defibrillator therapies during the COVID-19 pandemic: how you look provides perspective, by C.J. O’Shea et al., https://doi.org/10.1093/eurheartj/ehab385.
We read the report by O’Shea et al.1 demonstrating a 32% reduction in implantable cardioverter-defibrillator (ICD) therapies during the COVID-19 pandemic with great interest. We recently performed a similar analysis in New York City, New Orleans, and Boston.2 But in contrast to O’Shea et al., we found a 2–3 times higher rate of ICD shocks during the pandemic in comparison to the same time period in 2019. The results of these two studies appear contradictory at first, and it is important to point out why.
One important difference between these two analyses lies in their respective study populations. While O’Shea et al. analysed ICD therapies across the population on a state level, our data originated from zip codes with the highest prevalence of COVID-19. Hence, our study population was more likely to be enriched with patients infected with COVID-19 and positioned to demonstrate the effect of COVID-19 infection on ICD therapies. The state-level analysis, on the other hand, could have been diluted by a larger number of uninfected patients and thus be better positioned to demonstrate the impact of other factors related to the pandemic, such as stay-at-home orders, reduced activity or stress. Furthermore, the event rate of treated ventricular arrhythmias (2.8 events per 100 patient-days) in the report by O’Shea et al. was much higher than the event rate in our study (18–30 events per 1000 patients over 60 days) or that in previously published reports of ICD therapies (∼10% per year).3
In the absence of patient-level clinical information, these ecological studies carry a significant potential for confounding. However, patients with ICD offer a unique opportunity to study the influence of cardiac or non-cardiac events on arrhythmias4 and future studies examining the incidence of ICD therapies in patients with documented COVID-19 infection are needed.
Conflict of interest: S.A. has received grants from Medtronic unrelated to this Discussion Forum article. A.C. is an employee of Medtronic. There are no other items to disclose.
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