Background: The association among ketotic or hyperglycemic conditions and cardiac arrhythmias and sudden death increases possibility that ketosis or hyperglycemia may directly disrupt cardiac repolarization and hence be reason for arrhythmia and sudden cardiac death in these cases. Objective: The goal of the research was to assess ECG variations among diabetic studied cases admitted in Intensive Care Unit (ICU) with acute hyperglycemic syndromes. Patients and Methods: This study was prospective follow-up study and was conducted on patients admitted to medical critical care unit, Specialized Medical Hospital, Mansoura University during the period from January 2021 to January 2022. Results: There was significant (P<0.001) decrease in average heart rate, p wave maximum, p wave dispersion, QT maximum, QT dispersion and QTc. The depressed ST segment decreased from 4.8% to 3.8% with no significant difference, while the percentages of all types of arrhythmias are decreased on recovery in comparison to their values on admission. Conclusion: Diabetic ketoacidosis (DKA) and hyperglycemic hyperosmolar state (HHS) could be associated with several types of cardiac arrhythmias, which attributed to hyperglycemia and ketoacidosis rather than electrolyte disturbances.