Visiting high-altitude locations may be dangerous for people with high blood pressure or certain heart conditions, according to a new report from the American Heart Association that offers guidance about engaging in recreational activities in mountainous regions.
Published Thursday in the Journal of the American Heart Association, the scientific statement marks the first time the AHA has addressed the impact of physical activity at high altitude on people with heart conditions.
To help prepare for emergencies beforehand, people with high blood pressure, coronary artery disease, heart rhythm abnormalities or heart failure first should check with a health care professional, the statement advises. Consequences can be serious and even fatal, such as sudden cardiac death, which can occur within the first 24 hours of altitude change.
Many people are familiar with symptoms of acute mountain sickness such as headaches, dizziness, nausea and weakness, statement writing group chair Dr. William Cornwell III said in a news release.
"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," said Cornwell, an assistant professor of cardiology at the University of Colorado School of Medicine in Aurora.
Stress on heart, blood vessels
At higher altitudes – any place 9,840 feet above sea level or higher – the heart needs more oxygen-rich blood, even at rest. Activities at higher altitudes such as skiing, hiking, bicycling or climbing can place too much stress on the heart and blood vessels due to lower levels of oxygen and fluctuations in air pressure, temperature and humidity. Even at moderate altitudes, such as 8,800 feet above sea level, fainting can be common and may happen within 24 hours of making the ascent.
More than 100 million people travel to high-altitude, mountainous regions in the U.S. for work or pleasure each year, the report said. Many have risk factors for or already have been diagnosed with cardiovascular disease, so it's important to know the potential impact of exertion on the body, especially when medical centers that provide advanced cardiac care can be difficult to find or reach in some mountain areas.
People who live at high altitudes face fewer risks because their bodies have had time to adjust to living with less oxygen.
The statement advises increasing altitude gradually to give the body time to adjust to lower oxygen levels; drinking lots of fluids for better hydration; limiting or avoiding alcohol; and planning how to descend in an emergency. It suggests people with heart conditions consult a doctor about whether they need to adjust heart medications before travel. Finally, it recommends anyone who could potentially require emergency care to identify where to find it and to learn the symptoms that would prompt a need for it.
The report also offers guidance on altitude categories. Any place under 6,560 feet above sea level, such as Denver, is low altitude. Places 6,560 to 9,840 feet above sea level – such as the popular ski destination of Park City, Utah – are categorized as moderate altitude. High altitude is any place 9,840 to 16,400 feet above sea level. Mount Rainer, Washington, which is 14,411 feet above sea level, falls into this category. The summit of Denali in Alaska is 20,310 feet above sea level and considered extreme altitude.
"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," Cornwell said.
Giving the body time to adjust
Sudden cardiac death may be triggered by intense physical exertion, especially if the body hasn't had enough time to acclimate to the higher altitude and isn't well hydrated, the statement said. It can occur without warning and be fatal within minutes. But that risk can be lowered by sleeping one night at 3,381 feet above sea level before reaching high altitude, to give the body time to more gradually adjust to the change.
People with coronary artery disease – characterized by narrowed arteries leading to the heart – may experience shortness of breath, chest pain, dizziness and other symptoms caused by arteries being further constricted at high altitude and limiting blood flow to the heart. For people who recently had a heart attack, the evidence suggests "a trip to an area of higher altitude may need to be delayed," Cornwell said.
People with heart failure may need to adjust their medications at higher altitudes because of changes in blood pressure and the increased workload on the heart. Likewise, people with difficult-to-control blood pressure, or those visiting high-altitude areas for long periods of time, may need to carefully monitor blood pressure levels for any changes.
Sudden cardiac death is the most frequent non-traumatic cause of death at altitude, according to the statement. It may occur without warning and result in death within minutes if the individual does not receive treatment. Risk factors for sudden cardiac death include history of a prior heart attack, as well as male sex and older age.