Electrocardiographic changes during exposure to high altitude

Abstract

Serial electrocardiograms were obtained in 22 sea level residents and 20 Denver residents while at altitudes of 11,400 or 14,110 feet for four to five weeks. Significant QRS changes were noted in the groups at each high altitude; however, only minimal changes occurred in the Denver subjects at 11,400 feet. Pertinent findings include transient increases in heart rate, decreases in QRS amplitude, and T wave inversion; rightward and posterior shifts in QRS axis were progressive and prolonged. The variables of daily controlled exercise, depth of inspiration, and speed of ascent did not significantly influence the electrocardiographic findings.It is suggested that changes in QRS amplitude and T waves at altitude are transient effects of cardiac hypoxia, while prolonged shifts of the QRS axis may represent early stages of myocardial hypertrophy and are secondary to changes in pulmonary perfusion rather than ventilation.