AimThe aim of this study was to link the values of D-dimer and C-reactive protein (CRP), with the occurrence of pericardial effusion in patients who had coronavirus disease 2019 (COVID-19) and have preserved systolic function of the left ventricle (LV).MethodsThis was a prospective study and included 146 patients who underwent echocardiographic examination 30 days after the acute phase of COVID-19. Patients who were placed on mechanical ventilation, patients who had pulmonary thromboembolism or acute coronary syndrome during the acute period of the disease, patients who had an ejection fraction of the LV <50%, patients who were diagnosed with pericarditis during acute illness or clinical signs of heart failure (or had elevated N-terminal-pro hormone B-type natriuretic peptide value), with verified renal or hepatic dysfunction were excluded from the study, including patients with diabetes mellitus Type 1, patients with cancer, connective tissue disease, or pregnant women. The existence of cardiovascular risk factors (hypertension, diabetes mellitus Type 2, and hyperlipidemia), the presence of previous ischemic heart disease, maximum values of D-dimer, and CRP (during the first 15 days of the disease) was taken into the analysis.ResultsEffusion was verified around the right atrium (RA) in 104 patients (3.85 ± 1.75 mm), in 135 patients next to the free wall of the right ventricle (RV) (5.24 ± 2.29 mm), in front of the apex of the LV in 27 patients (2.44 ± 0.97 mm), next to the lateral wall of LV in 35 patients (4.43 ± 3.21 mm), and behind the posterior wall of LV in 30 patients (2.83 ± 1.62 mm). Mean CRP values during the acute phase of the disease were 43.0 mg/L (8.6–76.2 mg/L), whereas D-dimer mean value was 880.00 μg/L (467.00 –2000.00 μg/L). CRP values correlated with effusion next to the free wall of RV (rho = 0.202; P = 0.018). The D dimer correlated with effusion around RA (rho = 0.308; P = 0.0001).ConclusionThe clinical picture of the post-COVID patients could be explained by the appearance of pericardial effusion. D-dimer value correlates with the occurrence of effusion around RA, whereas CRP value correlates with effusion next to the free wall of RV.