TOPLINE:
Results of the SUMMIT study confirm the association between exposure to high altitude and the occurrence of cardiac arrhythmia, with more than one in three healthy individuals experiencing bradyarrhythmia or tachyarrhythmia while climbing Mount Everest.
METHODOLOGY:
- Arterial hypoxemia, electrolyte imbalances, and periodic breathing increase the vulnerability to cardiac arrhythmia at altitude.
- In the SUMMIT study, 41 healthy men (mean age, 33.6 years) underwent 12-lead ECG, transthoracic echocardiography, and exercise stress tests before and ambulatory rhythm recording both before and during an expedition on Mount Everest.
- None of the men had signs of exertional ischemia, wall motion abnormality, or cardiac arrhythmia at baseline.
- The primary endpoint was the incidence of a composite of supraventricular (> 30 sec) and ventricular (more than three beats) tachyarrhythmia and bradyarrhythmia (sinoatrial arrest, second- or third-degree atrioventricular block).
TAKEAWAY:
- Among the 34 men who reached basecamp (5300 m), 32 climbed to ≥ 7900 m, and 14 reached the summit of Mount Everest (8849 m).
- Forty-three bradyarrhythmic events were documented in 13 climbers (38.2%); seven men had a total of 23 bradycardias at rest, and 10 had 19 bradycardias during exercise; one individual had two episodes of third-degree atrioventricular block at rest at an altitude of 6500 m.
- Two tachyarrhythmic events were recorded in two climbers (5.9%); one climber had a nonsustained ventricular tachycardia during descent from 7900 m and one had a slow monomorphic sustained ventricular tachycardia during the ascent from 6500 m to 7300 m.
- Most rhythm disturbances were recorded at an altitude < 7300 m at which a majority of climbers did not use supplemental oxygen, whereas numerically fewer rhythm disturbances occurred on supplemental oxygen, despite higher altitude.
IN PRACTICE:
"The results of the SUMMIT study showed a substantial incidence of cardiac arrhythmia at extreme altitude. The potential implications of the observed rhythm disturbances need to be explored in future studies," the authors concluded.
SOURCE:
The study, with first author Kunjang Sherpa, MD, DM, Department of Cardiology, National Academy of Medical Sciences, Bir Hospital, Kathmandu, Nepal, was published online on April 3 in JAMA Cardiology.
LIMITATIONS:
The sample size was modest, and the study only included male climbers with previous exposure to extreme altitude, which may have biased the results.
DISCLOSURES:
The study was supported by a dedicated grant from the Swiss Polar Institute. Wearable continuous ECG patches were provided free of charge from ATsens, Seongnam, Republic of Korea. Sherpa had no relevant disclosures.