Cardiac arrhythmia at high altitude: the progressive effect of aging.

To evaluate the effects of aging on cardiac rhythm at high altitude, I wore a Holter monitor at age 75 during a climb to 5,100 m on Mt. Kilimanjaro, then compared findings with those from my climb to 5,895 m at age 65. Holter leads were placed to identify left or right ventricular source of ectopy, and on the 2nd ascent arterial oxygen saturation was monitored by finger oximetry. Sea-level testing revealed no evidence of cardiac disease. During ascent from 4,710 to 5,100 m, when arterial oxygen saturation reached 70%, heart rate was higher (123 vs 116 beats per minute), and frequency of left ventricular premature complexes was greater (56 vs 50 per hour) than on the earlier ascent. Nine 3- to 5-complex runs of left ventricular tachycardia were recorded during climbing, resting, or sleeping, and there was 1 run of 14 complexes at 250 beats per minute during the climb near 5,100 m. These observations suggest that aging increases sympathetic response or sensitivity, or both, to hypoxia during exercise, and even during sleep. Also, our focus should perhaps be on sympathetic stimulation rather than on pulmonary hypertension as a cause of arrhythmia in unacclimatized older persons at high altitude.