High-altitude medicine

ZONE OF KNOWLEDGE

If you suffer from heart diseases such as arrhythmias, hypertension, coronary artery disease, or have had a heart attack or undergone cardiac surgery, you should consult a doctor before planning a trip to high mountains.

Staying at high altitudes poses additional stress on the cardiovascular system, which can be dangerous in certain situations. If you are taking medications, make sure to bring an adequate supply of them for the trip, as well as extra in case of delays or unforeseen circumstances.

PREPARATION BEFORE DEPARTURE

Before your planned trip, it is advisable to:

➤ improve physical fitness,

➤ check exercise tolerance at sea level,

➤ discuss with your doctor the procedures in case of chest pain and the medications used.

BEHAVIOR AT HIGH ALTITUDE

If you experience a worsening of your condition while at high altitude, do not ascend to a higher elevation. It is also worth considering descending to a lower level and informing your companions about your condition.

EFFECT OF ALTITUDE ON HEART FUNCTION

Staying at high altitude affects the functioning of the cardiovascular system.Acute high-altitude hypoxia, increased physical activity, dehydration, and cold trigger the activation of the sympathetic nervous system, leading to:

➤ vasoconstriction,

➤ increased heart rate,

➤ increased blood pressure,

➤ increased cardiac output.

As a result, the heart muscle's demand for oxygen increases.This phenomenon is most evident during acclimatization, especially in the first three days at a new altitude.

During trekking, as higher altitudes are reached almost daily, the heart's demand for oxygen gradually rises. After about a week of acclimatization at the same altitude, heart function parameters usually return to levels similar to those at sea level.

CORONARY ARTERY DISEASE AND STAYING AT HIGH ALTITUDE

In individuals with coronary artery disease, the body's compensatory abilities at high altitude are limited.

Under such conditions, the following may occur more frequently:

➤ episodes of chest pain,

➤ arrhythmias,

➤ risk of sudden cardiac arrest.

Increased oxygen demand of the heart may also reveal previously undiagnosed coronary artery disease.Therefore, for individuals over 45 years old, it is recommended to perform the following before traveling to high mountains:

➤ EKG examination,

➤ cardiological stress test,

➤ echocardiogram.

Studies conducted in the Alps have shown that skiers and climbers with heart diseases, such as heart attack, hypertension, or coronary artery disease, have a higher risk of sudden cardiac arrest in the mountains. For this reason, many mountain huts and tourist centers have an automated external defibrillator (AED) on site.

SAFE ALTITUDE

Up to an altitude of about 2500 m above sea level, there is no increased risk of sudden cardiac death or heart attack.

Altitudes up to about 3500 m above sea level usually do not pose a significant risk for patients with stable coronary artery disease and good exercise tolerance at sea level. However, symptoms of the disease may occur more frequently and with less exertion than at sea level.

At each new altitude, it is recommended to acclimatize for 3–5 days before undertaking more strenuous physical activity. Ascending to higher altitudes should be done gradually, and the intensity of exertion is best monitored by heart rate.

There is a lack of reliable scientific data regarding the stay of individuals with coronary artery disease above 3500 m above sea level.

CHEST PAIN

If a person with coronary artery disease experiences chest pain during exertion at sea level, symptoms are likely to worsen at high altitude. In such cases, staying and exertion at high altitude are contraindicated.

AFTER A HEART ATTACK

Traveling to high altitude is absolutely contraindicated for the first 6 months after a heart attack.

After this period, before planning a high-altitude expedition, a stress test should be performed to assess exercise tolerance.

AFTER CARDIAC SURGERY

There is no data indicating that staying at high altitude increases the risk of closure of aortocoronary bypasses or stents after coronary artery angioplasty.

If the procedure was performed before the occurrence of a heart attack, there are reports of good exercise tolerance even at altitudes around 5700 m above sea level, although these are isolated observations.

RISK OF CARDIAC DEATHS AT HIGH ALTITUDE

Between 1987 and 1991, among approximately 276 thousand trekkers, 40 deaths were recorded at high altitude, of which:

➤ 2 were sudden deaths,

➤ 4 were caused by heart attacks.

These data suggest that the mortality rate from cardiac causes at high altitude is not very high, but the topic requires further research.

INDIVIDUAL RISK ASSESSMENT

The qualification of individuals with coronary disease for high-altitude expeditions requires an individual risk assessment. Important factors include:

➤ the type of planned activity (e.g., skiing vs. trekking),

➤ the intensity of effort,

➤ access to medical assistance.

Rescue and medical conditions in the Alps are significantly better than in remote regions such as the Himalayas.

HEART FAILURE

Individuals with symptomatic heart failure at sea level (e.g., edema, liver enlargement, pulmonary edema) should not be at high altitude.

Patients with stable disease can be at altitudes of up to about 2500 m above sea level.

At altitude, it may be necessary to increase the dose of diuretics, such as acetazolamide, while being mindful of the risk of dehydration.

CONGENITAL HEART DEFECTS

High-altitude hypoxia causes constriction of the pulmonary vessels and increased pressure in the pulmonary arteries. This can lead to high-altitude pulmonary edema (HAPE).

Individuals with certain congenital heart defects, such as:

➤ tetralogy of Fallot,

➤ ventricular septal defect,

➤ atrial septal defect,

➤ patent ductus arteriosus (Botallo's duct),

➤ absence of a pulmonary artery,

may exhibit an exaggerated constrictive response of the pulmonary arteries to hypoxia, increasing the risk of pulmonary hypertension and HAPE.

Individuals with symptomatic pulmonary hypertension at sea level should not be at altitude. Asymptomatic individuals should be aware of the increased risk of complications.

In some cases, prophylactic use of nifedipine during high-altitude stays is recommended.

Before departure, it may also be considered to test the body's response to hypoxia, for example, using a hypoxicator or hypobaric chamber.

BIBLIOGRAPHY

• Travel at High Altitude –www.medex.org.uk

• K. Mieske et al., Journeys to High Altitude—Risks and Recommendations for Travelers with Preexisting Medical Conditions, Journal of Travel Medicine, 2010; Volume 17 (Issue 1): 48–62

• G. Strapazzon et al., Risk Assessment and Emergency Management of Coronary Heart Disease at Altitude, High Altitude Medicine & Biology, 2011; Volume 12, Number 1: 97–98

• Ward, Milledge, Schoene, High Altitude Medicine and Physiology, 2007

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DO YOU WANT TO LEARNMORE?

If you want to better prepare yourself health-wise for trekking or high-altitude expeditions, you can find an extended version of the guide in the ebook"High Altitude Medicine in Practice – A Guide for Trekking and Expeditions" >>

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You can also gain practical knowledge about emergency procedures in the mountains through the online training"High Altitude First Aid" >> - designed for individuals planning trips to high altitudes.

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Meanwhile, you can find a detailed composition of the expedition first aid kit and a precise guide for preparing an expedition kit and personal rescue set in the ebook"Expedition First Aid Kit – A Complete Medical Guide" >>

ARE YOU PLANNINGA TREKORA HIGH-ALTITUDE EXPEDITION?

If you want to check whether your health condition allows you to safely participate in trekking or a high-altitude expedition, it is worth taking advantage ofa medical consultation >> ora telemedicine expedition package >>

This way, you can assess health risks in advance, prepare appropriately for the trip, and increase safety while at altitude.

The company was established in 2004. The goal of MedEverest is education in the field of mountain medicine and the dangers of high altitudes. I deal with all medical aspects of staying at high altitude. I organize medical support for trekking and high-altitude expeditions.

Specialist Medical Practice Medeverest Robert Szymczak based in Gdańsk (80-360), at ul. Bolesława Krzywoustego 19F, NIP: 5841943576, REGON: 220148318.

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