Pre-existing CAD and risk of mortality
One of the most striking and statistically significant findings of our cohort was the association between preexisting CAD and mortality. Patients with CAD had 62% mortality compared to 22% for those without prior CAD ((HR 2.4; 95% CI 1.16-4.9; P = 0.01) (figure 5). The association between viral illness and cardiovascular morbidity and mortality is well known. Previous work has shown much higher rates of influenza related death among those patients with cardiovascular disease. (13) Systemic illness puts significant stress on the heart as it tries to meet increased metabolic demands. In our cohort, we found several important differences between patients with preexisting CAD and those without that could explain the high mortality seen in these patients. Patients with preexistent CAD were significantly older (77 vs 61 years), had a higher prevalence of CKD (42 vs 14%) , underlying CHF (26% vs 6%), EF<45% (42% vs 14%) and higher levels of pro BNP and peak troponin T levels compared to those without CAD (supplemental Table). Interestingly, the level of inflammatory markers and D- dimer were not significantly different. While the exact mechanism for worse outcomes in COVID-19 patients with preexisting CAD is unclear, several theories have been suggested. Severe hypoxemia and cytokine storm, mediated by an imbalanced response among subtypes of T helper cells, may contribute to myocardial injury in COVID-19 patients and pose a greater risk in patients with a history of CAD and heart failure (7, 9). SARS-CoV has also been shown to directly cause myocardial inflammation via interaction with angiotensin-converting enzyme 2, a known receptor for SARS-COV-2 expressed on myocytes and vascular endothelial cells. (14, 15)