High-Altitude Medical

HANDBOOK

If you suffer from heart conditions such as cardiac arrhythmias, arterial hypertension, coronary artery disease, or if you have had a myocardial infarction (heart attack) or cardiac surgery, you should consult your physician before planning travel to high mountains.

Staying at altitude places additional strain on the cardiovascular system, which in some situations may be dangerous. If you take medications, make sure to bring an adequate supply for the expedition as well as extra doses in case of delays or unforeseen circumstances.

PREPARATION BEFORE THE TRIP

Before a planned expedition it is advisable to:

➤ improve physical fitness,

➤ assess exercise tolerance at sea level,

➤ discuss with your doctor what to do in case of chest pain and which medications should be used.

BEHAVIOR AT ALTITUDE

If you experience worsening well-being at altitude, you should not ascend further. Consider descending to a lower altitude and inform your companions about your condition.

THE EFFECT OF ALTITUDE ON HEART FUNCTION

High altitude affects the cardiovascular system. Acute high-altitude hypoxia, increased physical activity, dehydration, and cold lead to activation of the sympathetic nervous system, which results in:

➤ constriction of blood vessels,

➤ increased heart rate,

➤ increased blood pressure,

➤ increased cardiac output.

As a result, the oxygen demand of the heart muscle increases. This effect is most pronounced during acclimatization, especially in the first three days at a new altitude.

During trekking, when altitude increases almost every day, the heart’s oxygen demand gradually rises. After about one week of acclimatization at the same altitude, cardiovascular parameters usually return to values closer to those observed at sea level.

CORONARY ARTERY DISEASE AT ALTITUDE

People with coronary artery disease have limited compensatory capacity at altitude. In such conditions, the following may occur more frequently:

➤ episodes of chest pain,

➤ cardiac arrhythmias,

➤ risk of sudden cardiac arrest.

The increased oxygen demand of the heart may also reveal previously undiagnosed coronary artery disease. Therefore, for individuals over the age of 45, it is recommended before traveling to high altitude to undergo:

➤ ECG examination,

➤ cardiac exercise stress test,

➤ echocardiography.

Studies conducted in the Alps have shown that skiers and mountaineers with a history of myocardial infarction, hypertension, or coronary artery disease have a higher risk of sudden cardiac arrest in the mountains. For this reason, many mountain huts and tourist facilities at altitude are equipped with automated external defibrillators (AEDs).

SAFE ALTITUDE

Up to approximately 2500 m above sea level, there is no increased risk of sudden cardiac death or myocardial infarction.

Altitudes up to around 3500 m above sea level for patients with stable coronary artery disease and good exercise tolerance at sea level generally do not pose a major risk. However, symptoms of coronary disease may appear more frequently and with lower levels of exertion than at sea level.

At each new altitude, 3–5 days of acclimatization are recommended before engaging in more intense physical activity. Ascents should be gradual, and the level of exertion should ideally be monitored by heart rate rather than perceived effort.

Currently, there is limited scientific data regarding the safety of patients with coronary artery disease at altitudes above 3500 m.

CHEST PAIN

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

AFTER MYOCARDIAL INFARCTION

Travel to high altitude is absolutely contraindicated for the first six months after a myocardial infarction.

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

AFTER CARDIAC SURGERY

There is no evidence that high altitude increases the risk of closure of coronary artery bypass grafts or stents placed during coronary angioplasty.

If the procedure was performed before a myocardial infarction occurred, there are reports of good exercise tolerance even at altitudes of around 5700 m, although these are only isolated observations.

RISK OF CARDIAC DEATH AT ALTITUDE

Between 1987 and 1991, among approximately 276,000 trekkers, 40 deaths were reported at altitude.

Of these:

➤ 2 were sudden deaths,

➤ 4 were caused by myocardial infarction.

These data suggest that the frequency of cardiac deaths at altitude is not very high, although further research is needed.

INDIVIDUAL RISK ASSESSMENT

Qualification of individuals with coronary artery disease for high-altitude travel requires an individualized risk assessment. Important factors include:

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

➤ the intensity of physical effort,

➤ access to medical care.

Rescue and medical facilities in the Alps are much more accessible than in remote regions such as the Himalayas.

HEART FAILURE

People with symptomatic heart failure at sea level (e.g., peripheral edema, enlarged liver, pulmonary edema) should not expose themselves to high-altitude conditions.

Patients with stable disease may stay at altitudes of up to approximately 2500 m above sea level.

At altitude, it may be necessary to increase the dose of diuretic medications, such as acetazolamide, while carefully avoiding dehydration.

CONGENITAL HEART DEFECTS

High-altitude hypoxia leads to constriction of pulmonary vessels and increased pressure in the pulmonary arteries, which may result in 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,

➤ absence of a pulmonary artery,

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

Individuals with symptomatic pulmonary hypertension at sea level should not stay at high altitude. Those without symptoms should still be aware of the increased potential risk of complications.

In some cases, prophylactic use of nifedipine at altitude may be considered.

Before travel, it may also be useful to assess the body’s response to hypoxia using simulated altitude testing, such as with a hypoxicator or a hypobaric chamber.

REFERENCES

• 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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WANT TO LEARN MORE?

If you want to better prepare your health for trekking or a high-altitude expeditions, check out the expanded guide in the ebook "High-Altitude Medicine for Trekkers and Climbers" >>

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Gain practical skills for handling emergencies in the mountains through our online training "High-Altitude First Aid" >> - prepared for those planning trips to high altitudes.

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 For a detailed list of what to include in your expedition medical kit and step-by-step instructions for assembling your personal first aid set, see the ebook "High-Altitude Expedition Medical Kit Guide" >>

PLANNING A TREK OR A HIGH-ALTITUDE EXPEDITION?

If you would like to check whether your health condition allows you to safely participate in a trek or high-altitude expedition, consider booking a medical consultation >> or using a telemedical expedition package >>

This allows you to assess potential health risks in advance, prepare properly fot altitude, and increase your safety during the expedition.

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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