Background: Different electrocardiographic (ECG) results, seen in coronavirus disease 2019 (COVID-19) patients are most likely due to the combined impact of acute COVID-19 and chronic heart disease. Few studies have addressed the effects of hypoxemia, the hallmark of the pandemic disease, on ECG. Objectives: The present study discusses the prevalence of arrhythmias and disorders of conduction system in demised and survived COVID-19 patients, using ECG and Sokolow-Lyon voltage as a sign of hypoxemia to predict mortality in the admitted patients and after discharge. Methods: We investigated the ECG, and other medical data of 960 COVID-19 patients admitted to Faghihi hospital in Shiraz, Iran, from August 2021 to December 2021. Results: Most of the patients were male (541 or 56.4%) and older than 65 years old (462 or 48.1%). A total of 475 (49.5%) patients died. Multiple logistic regression revealed an independent association between the COVID-19 death rate and cardiovascular disease (OR = 3.05; 95% CI: 1.96 - 4.74), QT dispersion more than 40 (OR = 5.08; 95% CI: 3.61 - 7.15), heart rate (more than 100 versus less than 60 OR = 2.86; 95% CI: 1.03 - 7.9), ST segment elevation myocardial infarction (OR = 3.93; 95% CI: 2.63 - 5.86), poor progression (OR = 2.33; 95% CI: 1.56 - 3.49), hypertrophy (OR = 1.97; 95% CI: 1.02 - 3.81), and Sokolow-Lyon (OR = 2.91; 95% CI: 1.64 - 5.16). Conclusions: Electrocardiographic examination of COVID-19 patients is important during admission and after discharge. Sokolow-Lyon voltage less than 10 can be regarded as an independent predictor of mortality in COVID-19 patients discharged from hospital.