Interleukin-6 is upregulated and may be associated with myocardial injury in some patients who have recovered from COVID-19.

Coronavirus disease (COVID-19) causes myocardial injury by inducing a cytokine storm in severe cases. Studies have reported that myocardial injury persists for a prolonged period during COVID-19 recovery, and cardiac troponin is a useful indicator of myocardial injury. The interleukin-6 (IL-6) level is known to be associated with the morbidity and mortality of COVID-19, but this association has not been studied during recovery. The current study examined the association between IL-6 levels and myocardial damage during COVID-19 recovery. Four of 209 patients (1.9%) who recovered from COVID-19 had elevated IL-6 levels. All 4 patients tested positive for high-sensitivity troponin T, and 3 patients had subclinical left ventricular (LV) dysfunction according to echocardiography. Positivity for IL-6 during COVID-19 recovery suggests ongoing myocardial damage due to inflammation.

Elevated high-sensitivity troponin is associated with subclinical cardiac dysfunction in patients recovered from coronavirus disease 2019.

The aim of this study is to investigate myocardial damage in recovering coronavirus disease 2019 (COVID-19) patients with high-sensitivity troponin levels (hsTnT) and echocardiography. In this single-center cohort study, 215 COVID-19 recovered patients were recruited from all over Japan between April and September 2020. Demographic characteristics, hsTnT levels, and echocardiography data were collected for 209 patients, after excluding those without serum samples or good-quality echocardiographic images. The mean (± standard deviation) age was 44 (± 12) years (range: 36-55 years), and 50.7% of the patients were males. The median time interval (interquartile range) from COVID-19 onset to post-recovery examination was 56 days (34-96 days). Seventy-four recovered patients (35.4%) had hsTnT less than detection sensitivity (< 3 pg/mL) and 135 recovered patients (64.6%) had hsTnT ≥ 3 pg/mL. Ejection fraction was more than 50% in all cases. Left ventricular global longitudinal strain (LVGLS) and right ventricular free-wall longitudinal strain (RVFWLS) were reduced in 62 (29.7%) and 8 patients (3.8%), respectively. They were significantly associated with elevated hsTnT levels. In cases with hsTnT above 5 pg/mL, the LVGLS was greatly reduced to 19.0 ± 2.2% (p < 0.001). Multivariate linear regression analysis showed that elevated hsTnT level was an independent predictor of reduced LVGLS (standardized ß = -0.34; p < 0.001). In recovered COVID-19 patients, even a slight increase in hsTnT above detection sensitivity was associated with decreased LVGLS. hsTnT and echocardiography may be useful tools to detect myocardial injury in recovered COVID-19 patients.