الفهرس 
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Abstract
QT interval is a measure of the time between the start of the Q wave and the end of the T wave in the heart’s electrical cycle. It should be between 0.33 and 0.44 seconds. (QTc( is the QT interval corrected for heart rate. Higher rates of prolonged QTc are seen in females, older patients, high systolic blood pressure, short stature, adverse drug reaction and anorexia nervosa .
Type I diabetes mellitus (TIDM) is the most common endocrine metabolic disorder of childhood and adolescence. Compared to the general population, TIDM may increase the risk of mortality, due largely to an increased risk of cardiovascular disease.
QTc prolongation has been suggested as an independent marker of increased mortality in patients with TIDM as well as a marker for the early recognition of abnormalities of the autonomic nervous system, especially cardiac autonomic neuropathy, in patients with diabetes. It was found in many studies that children and adolescents with TIDM have a greater risk for prolonged QTc interval.
The present study was conducted on 60 patients with type I diabetes mellitus. They were chosen randomly from children attending the diabetes clinic of Alexandria University Children’s Hospital and compared to the control group included 60 children matched for age and sex. ECG was done to all of them; QT interval was measured on a 12 lead resting electrocardiogram. QT calculated using Bazett’s formula. (QTC = QT /√RR ). It was found that 33.3% of diabetic children had prolonged QTc interval ≥ 0.45 seconds whereas all controls had normal QTc interval < 0.45 seconds which was statistically significant. With increase in HbA1c, QTc interval increases and as duration of DM increases, QTc interval increases. The presence of history of DKA increases the possibility of QTc interval prolongation as 68.3% of cases had history of DKA, while 31.7% did not; also it shows the distribution of cases according to onset of DM, it ranges from 1 to 10 years old and duration of DM which ranges from 3 to 14 years. It was also found that 60% of diabetic children with prolonged QTc interval were females; age of these children ranged from 4 to 16 years old, their BMI ranged from 16 to 27%, duration of DM was from 4 to 14 years, 90% of these children had history of DKA and their HbA1c ranged from 7.3 to 12.5%. Only one case with prolonged QTc interval had good glycemic control while 4 cases with normal QTc interval had good glycemic control.
Good glycemic control and regular follow up is recommended for all children with TIDM to prevent prolongation of QTc interval.