ELECTROCARDIOGRAPHIC CHANGES AT HIGH ALTITUDE

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Abstract
The ecgs of climbers were recorded at 19,000 ft. at intervals during the winter of 1960-61 and subsequently at altitudes up to 24,400 ft. The effect of O2 breathing and exercise on the record was also studied. There was a shift of direction of the QRS and T vectors to the right in the frontal plane. In the precordial leads, there was a shift to the left of the transitional zone of the QRS complex and inversion of the T wave spreading across from right to left (from Vl-2 to V4-5), i.e. a backward shift of the QRS and T vector in the sagittal plane. Oxygen breathing did not reverse these changes except in the first O2 experiment. There was a decrease in the amplitude of the QRS voltage which was reversed by O2 breathing. The significance of these changes is discussed.