Stress of high elevation a possible factor in Summit County visitor heart attack deaths
March 13, 2017
A total of 23 people died of heart complications in Summit County last year. Among those, 19 were people who lived at lower elevations and suffered heart attacks shortly after arriving in the mountains.
The vast majority of those people were in their 50s or older, and they typically suffered heart attacks within a day or two of arriving, according to coroner's reports.
Although a firm link between high elevation and heart attacks hasn't been established, the markedly higher incidence of fatal cardiac events among people visiting from closer to sea level underscores the added stress that thin air can put on the circulatory system, doctors said.
"It's an interesting problem," said Dr. Warren Johnson, a local cardiologist. "It probably is more stressful because of the altitude when these lowlanders come up to exercise and ski and bike."
“There is very plausible biology behind this phenomenon of dealing with the stress of low oxygen and having higher adrenaline that stresses the heart.”Dr. Erik SwensonProfessor of medicine at the University of Washington
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Johnson said that he has seen several patients who were cleared to visit Summit by doctors near sea level, but upon arriving they experienced heart complications that persisted until they returned to lower elevations.
The High Country's thin air was noted in several of the coroner's reports, along with aerobic activates like skiing or walking through deep snow.
In one case, a man in his 60s collapsed while skiing at Breckenridge Ski Resort and was unable to be revived, a report said. His cause of death was listed as acute heart failure due to hypertension.
Often, reports said, decedents had reported feeling fatigued or having difficulty breathing before suffering heart attacks.
One man in his late 50s had been skiing at Keystone Resort and early on decided to call it a day, telling his friends he was tired and feeling ill before dying of heart failure near his car.
"It probably is the case that for anyone coming from low altitude with some underlying degree of heart problems, the stress of the new hypoxia is considerably higher," said Dr. Erik Swenson, a professor of medicine at the University of Washington. "It's a big step up for people adapted to lower altitude, and it might be enough of a cardiac stress to trigger a heart attack."
The actual concentration of oxygen in the air is the same at high elevations, but the strain on the body is greater because the air pressure is lower, reducing the effective oxygen level.
At sea level, the effective oxygen concentration is around 20 percent. But at 9,000 feet, roughly the elevation of Summit's towns, that drops to 14 percent. At the heights where most ski areas top out, around 12,000 feet, the effective oxygen concentration is only 13 percent.
The body responds to low oxygen levels by breathing more, pumping blood faster and producing adrenaline, all of which can take a toll on the body and potentially lead to heart complications.
"There is very plausible biology behind this phenomenon of dealing with the stress of low oxygen and having higher adrenaline that stresses the heart," Swenson said.
Still, the difficulty of sifting through the myriad factors that contribute to heart attacks — everything from lifestyle to genetics to age — means that finding a robust connection to elevation has been difficult.
"We have been looking into it, but we don't have enough evidence yet to say that this is unique to being up here," Johnson said.
Making a gradual transition to high altitude can help, both doctors said. Staying in Denver for several days before coming up to the High Country, for instance, can help the body start the long process of acclimation.
Adjusting to high elevations, however, can take weeks; several of the visitors who died of heart attacks last year had stayed in Denver for at least one night before traveling to Summit.
Johnson advised that people with a history of heart disease planning on visiting Summit should start preparing for the trip at sea level by consulting their doctor and exercising several weeks in advance.
Otherwise, the stress of low oxygen and aerobic activity on an already-weakened heart could prove fatal.
"If you're working harder than you normally do with the stress of being up there, for some it could be too much," said Swenson. "Everything is revved."