Increased interleukin-6 levels are associated with atrioventricular conduction delay in severe COVID-19 patients.

Background: Severely ill patients with coronavirus disease 2019 (COVID-19) show an increased risk of new-onset atrioventricular blocks (AVBs), associated with high rates of short-term mortality. Recent data suggest that the uncontrolled inflammatory activation observed in these patients, specifically interleukin (IL)-6 elevation, may play an important pathogenic role by directly affecting cardiac electrophysiology. The aim of our study was to assess the acute impact of IL-6 changes on electrocardiographic indices of atrioventricular conduction in severe COVID-19.

Methods: We investigated (1) the behavior of PR-interval and PR-segment in patients with severe COVID-19 during active phase and recovery, and (2) their association with circulating IL-6 levels over time.

Results: During active disease, COVID-19 patients showed a significant increase of PR-interval and PR-segment. Such atrioventricular delay was transient as these parameters rapidly normalized during recovery. PR-indices significantly correlated with circulating IL-6 levels over time. All these changes and correlations persisted also in the absence of laboratory signs of cardiac strain/injury or concomitant treatment with PR-prolonging drugs, repurposed or not.

Conclusions: Our study provides evidence that in patients with severe COVID-19 and high-grade systemic inflammation, IL-6 elevation is associated with a significant delay of atrioventricular conduction, independent of concomitant confounding factors. While transient, such alterations may enhance the risk of severe AVB and associated short-term mortality. Our data provide further support to current anti-inflammatory strategies for severe COVID-19, including IL-6 antagonists.