Heart risks for climbers at altitude

23 March, 2017
Load carrying high on Dhaulagiri
Load carrying high on Dhaulagiri
Load carrying high on Dhaulagiri
Load carrying high on Dhaulagiri

A study, by sports scientists at Leeds Beckett University and cardiologists at Poole Hospital, has found that in a team of 16 healthy mountaineers, without a previous history of heart disease, more than half (56.3%) experienced rhythm disturbances at altitudes of 4,100 metres or above.

These were either significant pauses in their heart beat – where the heart stops for three seconds or more – or very fast or irregular heartbeats. The pauses generally took place at night, while the climbers were asleep. All identified abnormalities disappeared once climbers descended below 4100m.

The research, published in the journal Circulation, was carried out with the voluntary involvement of members of last May’s Joint Services expedition to climb Dhaulagiri (8167 m) without oxygen. Having established Camp 3 at 7440 metres they were prevented from making a summit bid by high winds.

Medical data measuring heart rate and rhythm was gathered during the climb, using an innovative REVEAL LINQ two-inch device, which was implanted under the skin on the chest.

It was the first study to continually monitor climbers’ heartbeat over an extended period and shows the potential for technologies such as these to be used to help with medical diagnoses in remote locations. The group was studied over a period of at least four months, both before, during and after the 51-day expedition.

Heart rate and activity data were continuously recorded by the device and could be uploaded to a remotely stored server by a cellular signal or manually for analysis. The climbers could also trigger the device to specifically store extended recordings of their heart beat if they experienced any concerning symptoms, such as severe palpitations, which was observed among half the participants. Additional data on the climbers’ blood oxygen levels and physical condition were also collected.

Dr Chris Boos, Visiting Professor at Leeds Beckett University and Consultant Cardiologist at Poole Hospital, who led this study explained: “Our research has delivered a unique and fascinating insight into cardiac physiology at high altitude, showing what happens to the heart rate and rhythm while you sleep and exercise at very high altitude."

Dr. Boos with the REVEAL LINQ implant developed by medical technology company, Medtronic.(Photo courtesy of Poole Hospital NHS Trust)
Dr. Boos with the REVEAL LINQ implant developed by medical technology company, Medtronic.(Photo courtesy of Poole Hospital NHS Trust)

The most commonly identified cardiac abnormality were significant pauses, which were recorded on 81 occasions and affected 50 percent of the subjects. Both the frequency and duration of the pauses increased the higher the climbers went with the longest pause lasting seven seconds.

One climber experienced an episode of a sustained symptomatic irregular fast heartbeat, known as atrial fibrillation, which lasted for nearly five hours and had kept him awake at night, and another developed a fast abnormal heart rhythm known as a supraventricular tachycardia (SVT) lasting 31 seconds, while he attempted to lift a heavy load.

However, Dr Boos, said: “For the majority of mountaineers, there should be no cause for concern, as the pauses during sleep may simply represent normal physiological adaptation to the significant challenges of the very high altitude environment. However, going above 4000m could potentially exacerbate any pre-existing conditions which climbers may, or may not already be aware of, and this should be taken into account when planning expeditions.”

He added: “Our study also shows the potential of this kind of technology for delivering medical diagnoses to people in extremely remote locations.”

In November last year, the highly experienced alpinist and Himalayan mountaineer, Conrad Anker, suffered a heart attack while attempting the unclimbed Lunag-Ri in Nepal. National Geographic ran a candid interview with Conrad that provides a fascinating insight into this difficult health issue.

Related Climbing News: Dhaulagiri Medical Research Expedition