Effects of altitude on heart health

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People with heart disease are very susceptible to the effects of altitude, especially when on airplanes, mountain climbing, hot air balloon rides. High altitude increases cardiac output, increases heart rate, increases breathing rate and contractility of the heart, adversely affecting cardiovascular health if not prepared for countermeasures.

1. At what altitude is the thin air?

The higher the altitude, the thinner the air, the lower the oxygen density. Therefore, the cardiovascular system has to work harder to meet the body's oxygen needs.
For high-rise buildings, on average from the 10th floor onwards, the air will begin to thin out. However, the adaptation of the body due to the influence of altitude only begins to appear when at an altitude above 1500m above sea level. Normally, for healthy people, when climbing in the first 6 to 8 hours (such as when climbing a mountain) will notice signs of adaptation of the cardiovascular system. Accordingly, because the oxygen concentration in the air decreases, the body must compensate by slightly increasing cardiac output and respiratory output to be able to maintain the ability to supply oxygen to living organs. In addition, cardiomyocytes also increase their ability to use oxygen by various mechanisms. This is a very important factor to pay special attention to those with cardiovascular disease.
People born and raised at altitudes above 5000m (in high mountain areas), due to early adaptation to the thin concentration of air, the size of the rib cage is larger than that of people living in the plains. At the same time, the right ventricle is also more developed, helping the body to respond to and maintain high pulmonary artery pressure.

2. Effect of altitude on cardiovascular disease

When reaching an altitude above 1500m above sea level, the body begins to adapt to meet the oxygen demand by increasing the activity of the cardiovascular system. Therefore, the effect of altitude unintentionally harms the body. people with heart disease, the risk of dangerous cardiovascular events.
2.1. Changes in Cardiovascular Physiological Function Altitude is related to a gradual decrease in barometric pressure, air temperature and humidity. A decrease in barometric pressure leads to a dilution of oxygen in the air, causing hypoxia in tissues. The human body must adapt by various physiological responses to help maintain tissue oxygen concentration, increase alveolar ventilation, cardiac output, erythrocyte size, red blood cell oxygen carrying capacity, and other factors. Other metabolic reactions at the cellular microscopic level Effects of altitude increase blood pressure, increase heart rate (even at rest) and minute ventilation (which is the volume of respiratory gas in one minute) Alveolar hypoxia and hypoxic arterial blood cause pulmonary vasoconstriction, increased pulmonary vascular resistance and pulmonary artery pressure Altitude acclimatization leads to decreased left ventricular volume during both diastole and systole 2.2. Heart failure Patients with pulmonary hypertension , chronic obstructive pulmonary disease , chronic kidney disease , myocardial ischemia , anemia and thrombosis are susceptible to heart failure due to the effects of altitude .
2.3. Ischemic heart disease When hypoxic due to the effects of altitude, the heart adapts by increasing heart rate, the degree of which increases proportional to altitude. As the heart rate increases, so does the myocardial oxygen demand. Therefore, for patients with ischemic heart disease, the condition may become more serious, it is necessary to be very cautious and follow the instructions of the treating doctor.
2.4. Hypertension Patients with high blood pressure are very susceptible to the effects of altitude. Furthermore, the effects of some classes of antihypertensive drugs may be altered as the patient grows taller.

2.5. Cardiac arrhythmias Air travel and mountain climbers are at increased risk of cardiac arrhythmias due to increased sympathetic activity due to altitude, decreased SaO2 (arterial blood oxygen saturation), increased cardiac activity right ventricle and changes in plasma potassium concentration.
2.6. Pulmonary hypertension Under the physiological effects of hypoxia, the use of supplemental oxygen should be considered during flights or activities at altitudes of 1500m or higher in patients with pulmonary hypertension of degree III, IV and for those whose PaO2 is always fluctuating below 60 mmHg.
2.7. Congenital heart disease Patients with congenital heart disease are at greater risk of severe hypoxia than healthy individuals, because the increase in pulmonary vascular resistance due to the effects of altitude can worsen the condition of the shunts. . However, if only the oxygen content in the blood decreases, it is not dangerous because cardiac output and blood hematocrit will increase enough to maintain the ability to supply oxygen to the whole body.
2.8. Cerebrovascular diseases Ischemic stroke: Elevation is a risk factor for ischemic stroke in patients with a history of ischemic stroke. Caused by direct effects of hypoxia and cerebrovascular hyporesponsiveness Hemorrhagic stroke: High-altitude arterial hypertension increases the risk of aneurysms and ruptures brain, venous and arterial malformations, and an increased risk of hypertension-related cerebral hemorrhage

3. How to avoid the effects of altitude?

Although altitude-related travel activities (such as mountain climbing, high-altitude hot air ballooning, etc.) can affect people with cardiovascular disease, the following tips should help patients have a safer ride:
Light activities should be done only when at altitudes above 1500m to avoid putting extra pressure on the heart Heart failure patients should not move more than 500m per day when in places too high, because a sudden change in altitude can worsen cardiovascular symptoms Patients with severe cardiovascular disease, such as a history of myocardial infarction, stroke, poorly controlled hypertension, coronary stenting should not participate in sports activities related to altitude such as mountain climbing, skydiving,... Check and discuss the effects of cardiovascular drugs being used with medical staff medical conditions before traveling and make sure to carry and take all prescribed medications during your trip Altitude's effects on heart health are usually not too dangerous. Most people with heart disease can safely travel to the highlands if they make sure to take safety precautions before going and follow the instructions of their treating physician.
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Reference source: acc.org; cardiosmart.org