COVID-19(9) SARS-CoV-2(4) Post-COVID-19 tachycardia syndrome.(3) Coronavirus disease 2019(3) with COVID-19(3) Ejection fraction(3) Fragmented QRS (fQRS)(3) Patient(3) median(3) cardiac injury(3) Hydroxychloroquine(3) median age(3) Fredericia(2) ECG(2) group(2) arrhythmia(2) 95%CI(2) single-center(2) calculated(2) the median(2) Treatment(2) Diagnosis(2) female(2) QTc interval.(2) multivariable analysis(2) receiving(2) QT interval(2) IQR(2) Hospitalized(2) Retrospective study(2)