Cardiac and Muscle Injury Might Partially Contribute to Elevated Aminotransferases in COVID-19 Patients

Dear Editor:

Corona virus disease 2019 (COVID-19) patients can have elevated aminotransferases.1, 2, 3 It seemed that increases of aspartate aminotransferase were more prominent than alanine aminotransferase in COVID-19 patients according to previous studies.1, 2, 3 In the study by Fan et al,¹ the proportions of patients with elevated aspartate aminotransferase and alanine aminotransferase were 21.6% and 18.2%, respectively. Among severe COVID-19 patients, the proportion of patients with elevated levels of aspartate aminotransferase also seemed higher than the proportion with elevated levels of alanine aminotransferase (39.4% vs 28.1%) in the study by Guan et al.² In another study,³ the absolute levels of aspartate aminotransferase were also higher than alanine aminotransferase (31 vs 24 U/L). Of note, the upper limits of normal for aspartate aminotransferase and alanine aminotransferase were different, which were 40 vs 50 U/L, respectively.³

But not all abnormal liver function test results mean liver damage. Guo et al⁴ indicated that acute cardiac injury can occur in COVID-19 patients, which can be seen in up to 27.8% of patients (52/187). Patients with acute cardiac injury also had significantly higher levels of aspartate aminotransferase than those without cardiac injury (39.5 vs 29.0 U/L; P < .001). However, the difference in alanine aminotransferase did not reach statistical significance between patients with acute cardiac injury and without it (28.5 vs 23.0; P = .11).⁴ Meanwhile, the heart may occasionally contain a high alanine aminotransferase activity,⁵ so abnormal levels of alanine aminotransferase and aspartate aminotransferase might partly result from myocardial injury, especially when increases of aspartate aminotransferase are more prominent.

In addition, the viral infection can cause muscle injury. In the case of muscle injury, sarcoplasmic proteins including creatine kinase, alanine aminotransferase, and aspartate aminotransferase can be high. It has been reported that rhabdomyolysis can occasionally occur in COVID-19 patients.^{2 , 6}

Hence, we think the incidence of liver damage might be overestimated in COVID-19 patients. We speculate that cardiac and muscle injury might partially contribute to elevated aminotransferases in COVID-19 patients. The largest study so far found that 13.7% of COVID-19 patients had elevated levels of creatine kinase, which may also indicate that muscle or cardiac injury occurred.²

Regarding the association between liver injury and overall prognosis in COVID-19 patients, Fan et al¹ indicated that baseline liver impairment was associated with a prolonged hospital stay, and abnormal liver function during admission had little effect on the length of hospital stay. However, the acute cardiac injury is significantly associated with fatal outcome in COVID-19 patients⁴; meanwhile, rhabdomyolysis is a potentially life-threatening condition. We suggest that patients with elevated aminotransferase be evaluated for the presence of acute cardiac injury or rhabdomyolysis.