Serum Lactate Dehydrogenase, Creatinine Phosphokinase, and Troponin Levels Among Cardiac Patients with Coronavirus Disease 2019: A Retrospective Study

Background & Objectives: Coronavirus disease 2019 (COVID-19) can cause myocardial injury and thereby worsen clinical outcomes in patients with preexisting cardiac disease. This study assessed the association between admission serum lactate dehydrogenase (LDH), creatine phosphokinase (CPK), and troponin levels and clinical outcomes among hospitalized cardiac patients with and without PCR-confirmed COVID-19. Materials & Methods: In this retrospective comparative study, we analyzed 200 consecutive cardiac patients admitted in Zabol, Iran, between March 2019 and March 2020. One-hundred patients had PCR-confirmed COVID-19 and 100 did not. We compared demographic characteristics, admission blood pressure, admission serum LDH, CPK, and troponin levels, baseline left ventricular ejection fraction (EF), and length of hospital stay between groups. Multivariable logistic regression was used to identify independent predictors of in-hospital mortality. Results: Compared with non-COVID-19 cardiac patients, those with COVID-19 exhibited higher mean systolic blood pressure (166.96 versus 143.08 mmHg; p < 0.001), higher mean diastolic blood pressure (110.55 versus 91.35 mmHg; p < 0.001), and higher mean levels of CPK (363.06 versus 270.99 U/L; p < 0.001) and LDH (570.69 versus 384.43 U/L; p < 0.001). Troponin positivity was more frequent among COVID-19 patients (71% versus 41%; p < 0.001). An EF below 35% occurred more often in the COVID-19 cohort (54% versus 20%; p = 0.048). In multivariable analysis, independent predictors of in-hospital mortality were COVID-19 status (adjusted odds ratio [aOR] 2.42; 95% confidence interval [CI], 1.28–4.56), troponin positivity (aOR 3.15; 95% CI, 1.63–6.08), and EF < 35% (aOR 2.89; 95% CI, 1.41–5.91). After adjustment for covariates, neither admission CPK nor LDH remained statistically significant predictors of mortality. Conclusion: Troponin positivity and reduced left ventricular ejection fraction are robust independent predictors of mortality among hospitalized cardiac patients, particularly in the context of COVID-19. Although CPK and LDH are frequently elevated in patients with COVID-19, these markers may predominantly reflect nonspecific tissue injury rather than myocardial-specific damage. Early assessment of troponin and EF on admission can facilitate risk stratification and inform clinical management in this high-risk population.