AHA issues recommendations for patients with CVD planning high-altitude activities
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Because sudden cardiac death can occur in patients with CVD traveling to higher altitudes, experts recommended in a new American Heart Association scientific statement that patients with CVD consult a physician before travel.
“Many people and health care professionals are familiar with symptoms of acute mountain sickness like headaches, dizziness, nausea and weakness. However, they may be less aware of the stress placed on the body — and particularly the heart and lungs, when people with cardiovascular disease travel to mountainous regions where there is a reduction in oxygen availability compared to sea-level conditions. If people are not prepared, they may be at an increased risk of adverse events in these types of environments,” William K. Cornwell III, MD, MSCS, FAHA, assistant professor of cardiology at the University of Colorado School of Medicine and chair of the scientific statement writing group, said in a press release. “This concise overview of how altitude impacts patients with cardiovascular disease provides additional information to help guide clinicians in advising their patients on best practices for safe travel to higher altitudes and mountainous regions.”
According to the statement, high-altitude exposure is associated with lower blood-oxygen content caused by reduced atmospheric pressure and partial pressure of oxygen, creating a hypoxic environment. High-altitude activities can require increased oxygen demand, which is a challenge to overcome in relatively oxygen-deprived environments.
In the presence of acute hypoxia, individuals can experience systemic arterial vasodilatation, hypoxic pulmonary vasoconstriction and activation of peripheral chemoreceptors. These physiological responses can have downstream effects, including sympathetic activation, which increases BP and cardiac output, as well as hyperventilation and pulmonary hypertension, the committee wrote.
Effects of high-altitude activities
“More than 100 million people travel to mountainous environments yearly for work or pleasure. Mountain activities frequently involve exercise, which, when combined with environmental changes such as temperature, humidity, pressure and oxygen availability, place unique challenges on the cardiovascular system,” the committee wrote. “Medical resources are frequently limited, which may compromise outcomes following adverse events. Therefore, it is incumbent on clinicians to understand the unique physiologic challenges associated with exercising in hypoxic environments.”
The committee identified the following CVD states that, if identified in a patient planning high-altitude travel, increase risk for CV events at high altitude:
In patients with CAD, atherosclerosis can cause paradoxical vasoconstriction of coronary vessels in response to increased oxygen demand from exercise combined with altitude-related hypoxia. Moreover, acute hypoxia may exacerbate angina symptoms.
In hypertension, high-altitude exposure causes an initial reduction in BP associated with hypoxia-related systemic vasodilation; however, the initial reduction is counteracted by chemoreflex-mediated vasoconstriction, causing BP elevation. This risk in BP is primarily driven by increased oxygen content due to high-altitude acclimatization.
In patients with rhythm disorders or at risk for sudden cardiac death, acute hypoxia may trigger an arrhythmic event. According to the statement, prior observational studies showed that more than 50% of sudden cardiac deaths at altitude occur within the first day of exposure.
Physiological responses to hypoxia, including sympathetic nerve activation, elevated systemic and pulmonary arterial pressures, tachycardia, increased lung fluid content and reductions in stroke volume, may worsen symptoms in patients with HF with reduced ejection fraction. In addition, HF therapies such as carvedilol, diuretics and acetazolamide may inhibit exercise tolerance at altitude. According to the statement, there are no published studies on altitude tolerance among patients with HF with preserved ejection fraction; however, patients with HFpEF are likely to have elevated pulmonary arterial pressure, hypertension and atrial fibrillation at sea level, so heart-rate and BP control at altitude may be important.
High-altitude exposure can also increase pulmonary hypertension and pulmonary vascular resistance, which can worsen hypoxemia and exercise tolerance. According to the statement, altitude can also worsen central sleep apnea and decrease nighttime systemic oxygen saturation.
Pretravel considerations
“A thorough assessment by a health care professional may be necessary before a mountain sojourn to assess risk and ensure that people with a history of heart disease safely enjoy physical activities in the mountains,” Cornwell said in the release. “Together with a health care professional, a plan should be developed before travel, bearing in mind the location and duration of travel, along with the severity of the individual’s medical conditions.”
The writing committee recommended the following strategies for clinicians to help patients planning a safe trip to high altitudes:
- Increase altitude gradually so the body has time to acclimate to the lower levels of oxygen at high elevations.
- Stay hydrated.
- Adjust medications to reduce the likelihood of CV events, as directed by a medical professional.
- Determine whether additional medications are needed to treat certain symptoms, especially if they occur while in a remote location.
- Limit or avoid alcohol.
- Identify symptoms that could prompt emergency evacuation.
- Plan a gradual ascent and establish emergency descent plans.
- Be aware of the closest hospitals.
“Patients with cardiovascular disease must accept the risk of an acute cardiovascular event with limited access to advanced medical care, and this risk should be factored into pretravel counseling as appropriate based on an individual’s risk profile,” the committee wrote.
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