Haiduc et al attempt to summarise the current literature surrounding the effect of congenital heart disease (CHD) on COVID-19 outcomes. Reference Haiduc, Ogunjimi and Shammus1 We propose further consideration of the following factors: age, type and severity of CHD, and comorbidities.
This review directly compares studies and case reports of patients with ages ranging from 3 months to 76 years. Discrepancy in ages is important to consider since COVID-19 is known to affect infants less than 1 year of age more severely. Reference Singh, Heston and Langel2 This may be due to low T-cell activation, reduced expression of ACE2 in the lungs and other developmental differences. Reference Singh, Heston and Langel2 Older patients are likely to have developed more comorbidities which may be the reason for the presentation of worse COVID-19 symptoms, rather than being due to their CHD alone. Literature also shows racial disparities in the severity of COVID-19 which may confound the effect of CHD on outcomes. Reference Best, Mohan and Kong3
Contrary to this review, there is evidence that individual defects such as single ventricular defects are not sufficient cause alone for worse COVID-19 outcomes. Reference Lewis, Anderson and Fremed4 Lewis et al reported that out of 53 CHD patients, there appeared to be no correlation between the complexity of the CHD and the subsequent infection-related cardiac decompensation displayed by the patient. Reference Lewis, Anderson and Fremed4 This may explain why patients with similar CHDs experience different disease trajectories. Therefore, using only the CHD status is not a sufficient indicator for poor outcomes and markers of symptom progression such as raised cardiac troponins upon admission may prove more useful. Reference Malviya and Rakesh5 This is particularly relevant since CHD patients with infection-induced myocardial injury are at a higher risk of complications. Reference Malviya and Rakesh5 Treatment protocols used to manage infections should also be considered amongst the studies included in the review. For example, Non-steroidal anti-inflammatory drugs use in early infection is thought to be controversial due to reports of causing more complications when administered for respiratory tract infections. Reference Robb, Goepp, Rossi and Yao6
From the studies included in the review, 24% of the patients had comorbidities with the most frequent being genetic conditions, type 2 diabetes mellitus, and chronic kidney disease. Reference Haiduc, Ogunjimi and Shammus1 Massin et al demonstrates that a significant proportion of children with CHD have associated non-cardiac comorbidities including genetic conditions, with the most common being trisomy 18. Reference Massin, Astadicko and Dessy7 These comorbidities make it difficult to assess the direct effect of CHDs on outcomes. Similarly, Agarwal et al show that adults with CHD are twice as likely to have non-cardiac comorbidities compared to their non-CHD counterparts. Reference Agarwal, Thombley and Broberg8 Additionally, for patients below the age of 40, the more severe the CHD, the higher the risk of developing non-cardiac comorbidities. Reference Agarwal, Thombley and Broberg8
In conclusion, in order to determine causality or a significant correlation between COVID-19 prognosis and CHD, this review needs to stratify CHD according to type of defect and severity, whilst controlling for confounders such as age and comorbidities.
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