Electrocardiographic changes during upper gastrointestinal endoscopy in ambient hypoxia.

Electrocardiographic (ECG) changes were studied in 120 consecutive subjects during and after upper GI endoscopy done in ambient hypoxia (PO2-120 mmHg) at Shimla (2200 m). No premedication was given to any of the subjects. There were 75 men and 44 women. Fifty three subjects were aged 40 years or below (Group I) and 67 subjects were above 40 (Group II). There were 29 subjects with and 91 subjects without cardiac diseases. Increase in heart rate was seen in 96.6% of subjects. Maximum rise in heart rate was found in cardiac patients. ST depression was seen in 14.2%, T wave inversion in 13.3%, supraventricular tachycardia in 5.8% and ventricular ectopics in 1.6%. ST depression was more frequent in cardiac than in non cardiac patients (P less than 0.001) and T wave inversion was more frequent in women than in men (P less than 0.001). All the changes reverted to normal within 10 minutes. ECG changes notwithstanding, upper GI endoscopy without premedication in the presence of ambient hypoxia is a safe procedure.