Heart attack happens when there is a sudden loss of blood flow to a part of a person’s heart muscle. A heart attack requires immediate medical attention – delaying calling 999 can dramatically reduce a person’s chance of survival. It is well understood that pre-existing health conditions can raise a person’s risk of having a heart attack. Chillingly, one activity greatly escalates the risk, regardless of how healthy a person is.
The UK may have experienced an unprecedented heatwave this summer but people should think twice before plunging into cold water.
Research published in the Journal of Physiology revealed that entering cold water suddenly, without taking time to acclimatise, may cause abnormal heart rhythms that can be fatal.
The study explained how rapid submersion in cold water, combined with holding ones breath, automatically activates two powerful responses in the body which may interact and cause conflict at the level of the heart.
Providing further insight into how his happens, the scientists, from the University of Portsmouth and Kings College London, explained how the body’s cold shock Response, which speeds up the heart rate and causes hyperventilation, may conflict with the Diving Response, which does the opposite and which acts to conserve oxygen.
Professor Mike Tipton, who runs the Extreme Environments Laboratory in the Department of Sport and Exercise Science, said that entering cold water should be done with caution.
He said: “As the recent sad spate of immersion deaths confirm, we have entered the most dangerous time of the year for water-related deaths. As air temperatures rise dramatically, people start to go into water that remains dangerously cold. The body’s responses to immersion in cold water are profound, uncontrollable and can result in drowning and heart problems within seconds.”
Professor Tipton and his colleague Professor Mike Shattock of King’s College London, revealed that sudden cooling of the skin evokes the cold shock response; the faster the change in skin temperature the bigger the response. Immersion of the face with breath holding evokes the diving response: therefore submersion, even periodic submersion due to wave splash, can produce Autonomic Conflict.
Professor Tipton said: “Those wanting to enter the water should do so in a slow and controlled fashion to minimise these hazardous responses. Individuals should also realise the water they felt comfortable in at the end of last year is colder, and they are less prepared for it at the start of the summer.
“The prevalence of heart problems on immersion in water tends to be underestimated because electrical disturbances to the heart are undetectable post-mortem,” he said.
He added: “The incapacitation caused by cardiac arrest, such as gasping for breath and breathing in water, means that death is often ascribed to drowning, but we believe a significant number of these cases could have a basis in Autonomic Conflict.”
Professor Shattock said: “These heart rate irregularities caused by Autonomic Conflict occur quite frequently on immersion in cold water but may only become lethal when other predisposing factors exist such as a large heart, pre-existing heart disease or a subtle and otherwise benign genetic mutation. We also think that Autonomic Conflict may be a cause of sudden death in other, non water-related situations.”