In a single-centre retrospective study of 273 patients from Wuhan, China, Han et al. reported that 10% had elevated troponin I and 12% had elevated NT-proBNP concentrations(1). Elevated cardiac biomarker levels were more common among severely ill patients as compared to milder cases. Among mild cases, 5% and 7% had elevated troponin I and NT-proBNP levels respectively. In total, 24 deaths were documented (case-fatality rate 9%). The case-fatality rate was higher among those with abnormal cardiac biomarkers (23%) as compared with those with normal cardiac biomarkers (5%).
The frequency with which cardiac biomarkers are elevated in COVID-19 is uncertain. The present study only included hospitalized patients. The threshold for hospitalization is likely to vary in different settings; if hospitalization were reserved for only the most unwell patients, then one might expect higher biomarker levels and vice versa. Also, this report does not provide data on cardiac biomarkers among non-hospitalized individuals with COVID-19. Given that only the minority of individuals with COVID-19 are hospitalized, the true prevalence of myocardial injury is uncertain.
The finding that elevated troponin and NT-proBNP are prognostically important is novel inasmuch as COVID-19 is a new infection to humans but is unsurprising based on similar observations in a variety of other clinical contexts. Little is known about the mechanisms underlying such putative cardiac injury. There have been anecdotal reports of presumed and in some cases histologically proven myocarditis. The contribution of pre-existing cardiac disease and demand ischemia or metabolic insult is unclear.
Systematic research into the cardiac complications of COVID-19 is limited as resources are stretched with the demands of treating large numbers of affected patients effectively while ensuring the safety of healthcare workers and research personnel. However, unless we can develop acceptable, safe and efficient ways of conducting epidemiologic biomarker research, as well as effective management strategies based on biomarker levels, the role of and best response to the finding of elevated cardiac biomarkers are unknown.
1. Han H, Xie L, Liu R et al. Analysis of heart injury laboratory parameters in 273 COVID-19 patients in one hospital in Wuhan, China. J Med Virol 2020.