The electrocardiogram at extreme altitude: experience on Mt. Everest

Area of Science:

• Cardiology
• Altitude Physiology
• Environmental Medicine

Background:

• The American Medical Research Expedition to Mt. Everest offered a rare chance to study cardiac responses in humans at extreme altitudes.
• Previous research on electrocardiographic (ECG) changes at high altitude was limited.

Purpose of the Study:

• To document 12-lead resting ECGs in a large cohort at extreme altitude.
• To analyze changes in heart rate, electrical axis, and conduction patterns at varying altitudes.

Main Methods:

• 19 male subjects underwent 12-lead resting ECG recordings at sea level, 5400m (base camp), and 6300m (camp 2).
• Data from 12 subjects with complete recordings were analyzed using a two-way analysis of variance.
• Measurements included heart rate, P wave amplitude, QTc interval, and frontal plane QRS axis.

Main Results:

• Resting heart rate significantly increased with altitude (p < 0.001).
• P wave amplitude increased, QTc interval decreased (p < 0.001), and the frontal plane QRS axis shifted significantly rightward (p < 0.001).
• At extreme altitude, conduction disturbances (right bundle branch) and signs of right ventricular hypertrophy were observed in some subjects.

Conclusions:

• Extreme altitude exposure induces significant and measurable changes in cardiac electrical activity.
• These ECG alterations reflect physiological adaptations and potential strain on the heart at high altitudes.
• Further research is warranted to understand the long-term implications of these high-altitude cardiac changes.