SARS-CoV-2 spike protein-induced inflammation underlies proarrhythmia in COVID-19.

Coronavirus disease 2019 (COVID-19) patients have a 1.7-fold higher arrhythmia risk with rates of cardiac complications ranging from 2% non-ICU patients to 59% in non-survivors. Atrial fibrillation (AF), the most common arrhythmia, is a frequent complication of acute and long COVID-19. The high expression of ACE2 in the heart suggested that infectious virus may underlie cardiac complications. However, we recently reported in human cardiac tissue from fatal COVID-19 cases perivascular spike protein, elevated pro-inflammatory cytokines, vascular damage, and cardiac remodeling without evidence for direct infection of cardiac cells by SARS-CoV2. Mislocalization of intercalated disc (ID) components, connexin-43 (Cx43) gap junctions and Na(V)1.5 sodium channels, was also evident in patients' hearts, recapitulating structural remodeling we previously identified as providing a substrate for atrial arrhythmias following an acute inflammatory insult. Therefore, we hypothesized that the inflammatory response elicited by SARS-CoV2 spike protein is sufficient to provoke atrial arrhythmias. Structural and functional assessments of WT murine hearts were performed five days following a single bolus intravenous injection of the viral spike protein. In vivo ECGs demonstrated increased atrial arrhythmia burden in spike-injected mice vs. control. Immunohistochemistry studies revealed elevated expression of inflammatory markers and evidence of vascular damage in these mice. Additionally, we observed disruption of ID ultrastructure and mislocalization of Cx43 and Na(V)1.5 in the atria of spike protein-injected mice. Our results suggest that vascular-leak inducing inflammatory insult from viral spike protein, and not direct infection by SARS-CoV2 results in the pathophysiology of cardiac dysfunction in fatal COVID-19.