Background: Exposure to high altitudes has been associated with an increased risk of cardiac arrhythmias in healthy subjects and an increased risk of sudden cardiac death.

Aim: The aim of the present study is to evaluate the risk and the incidence of cardiac arrhythmias at extreme altitude.

Methods: This is a prospective cohort study of healthy volunteers determined to climb Mount Everest. Subjects will be evaluated for eligibility by electrocardiography and echocardiography. All study participants will undergo ambulatory rhythm monitoring in their home environment within 12 weeks of the climb. Subsequently, ambulatory rhythm monitoring will be repeated during the ascent from basecamp to the summit of Mount Everest. The primary endpoint will be the composite of supraventricular and ventricular tachyarrhythmias, and bradyarrhythmias.

Background: Several physiological changes at high altitude give rise to a pro-arrhythmic milieu. A fall in atmospheric pressure at high altitude decreases the partial pressure of oxygen (PaO2) and causes arterial hypoxemia. Respiratory alkalosis secondary to hyperventilation causes hypokalemia and hypocalcemia. Both factors facilitate the occurrence of rhythm disturbances, and may be further exacerbated in an adrenergic state with increased epinephrin levels.

Objectives: The primary objective is to investigate the incidence of supraventricular and ventricular tachyarrhythmias, and the incidence of bradyarrhythmias in climbers during the ascent of Mount Everest. The secondary objective is to investigate clinical, electrocardiographic and echocardiographic predictors of cardiac arrhythmias at extreme altitude.

Methods: This is a prospective cohort study of healthy volunteers climbing Mount Everest. Subjects will be evaluated for eligibility by electrocardiography and echocardiography. All participants will undergo a stress test in order to rule out pre-existing rhythm disturbances during exercise. Study participants will undergo ambulatory rhythm monitoring in their home environment within 12 weeks of the climb. Subsequently, subjects will repeat ambulatory rhythm monitoring during the ascent from basecamp to the summit of Mount Everest. The subjects will act as their own controls.

Inclusion Criteria:

• Age ≥18 years
• Normal electrocardiogram
• Normal echocardiography
• Written informed consent

Exclusion Criteria:

• Known cardiac arrhythmia
• Evidence of AV-block, left bundle branch block, or repolarization disorders on electrocardiogram
• Evidence of structural heart disease (valve disease more than mild) or compromised left ventricular ejection fraction as assessed by echocardiography
• Symptoms or history of skin cancer, rash, skin disease, keloid or injury
• Cardiac pacemakers, cardiac defibrillators, implantable electrical devices
• Pregnancy, breastfeeding

Healthy volunteers climbing Mount Everest.