CLIMBERS may be at risk of heart complications at high altitudes, cardiologists at Poole Hospital have shown.

New research reveals climbing above 4,000m can provoke abnormal heart rhythms in otherwise healthy mountaineers with abnormalities increasing with altitude.

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

These were either significant pauses in their heartbeat – 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 4,100m.

The research, published in the journal Circulation, was carried out with a team of military volunteers from the Defence Medical Services during an expedition to climb Nepal’s 8,167m Mount Dhaulagiri, in the Himalayas – the seventh tallest mountain in the world.

The mountaineers had mini heart monitors called REVEAL LINQ implanted in their chests and they were studied over a period of at least four months both before, during and after the 51-day expedition.

Similar in size to a AAA battery, the devices are typically used in clinical care to detect rare cardiac events but had not previously been tried at high altitude.

Heart rate and activity data were automatically transmitted for analysis.

The research is the first to continually monitor climbers’ heartbeat over an extended period and shows the potential for technology to be used to help with medical diagnoses in remote locations.

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.

“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.”

The team plan to continue their investigations with larger groups of subjects and using even more recent advances in cardiac non-invasive monitoring technology which will enable even greater detail to be recorded without the need for devices to be implanted.