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Body temperature link to sudden deaths

New Delhi, July 17: Subtle body temperature changes that occur during intensive exercise or sleep may be a trigger for the rare and tragic sudden cardiac deaths that have claimed the lives of otherwise healthy adults and infants, medical researchers have said.

The researchers at the Simon Fraser University (SFU) in Canada and other institutions have found that the body's temperature changes can set off spikes in abnormal heartbeat, a condition known as cardiac arrhythmia, that can, when unchecked, lead to the sudden death.

Their findings, published this week in The Journal of Physiology, could help explain the rare sudden deaths such as of a football player during a game, a candidate running at an army recruiting camp, or a healthy infant during sleep.

Biomedical physiologist Peter Ruben at the SFU and his colleagues studied a set of proteins that govern the electrical signals that drive the heartbeat, and how these proteins are affected by changes in the body temperature.

Doctors estimate that about 700,000 people die in India from sudden cardiac death every year, but over 80 per cent of these can be attributed to previously diagnosed or undiagnosed coronary artery disease.

"The other 20 per cent may be explained through underlying heart muscle disorders or electrical disorders of the heart," said B. Hygriv Rao, a senior electrophysiologist at the Krishna Institute of Medical Sciences, Hyderabad.

"In many cases, such disorders remain undiagnosed," Rao, who had reviewed sudden cardiac deaths in India two years ago, told The Telegraph.

For the heart to efficiently pump blood through the body, the muscle cells of the heart need to contract rhythmically in a well-coordinated manner. Arrhythmia can disrupt this rhythmic pumping and, in extreme cases, lead to sudden death.

"The electrical signal behind muscle contraction is produced by tiny protein molecules in the heart cells," Ruben said in a media release issued by the SFU. "Temperature fluctuations modify the way all proteins behave, but some DNA mutations can make proteins especially sensitive to changes in temperature."

Ruben's team found that one such protein is highly sensitive to temperature. When the body temperature increases slightly during intense exercise or decreases during deep sleep, the affected protein no longer works, leading to arrhythmia.

Cardiologists say specific knowledge of the protein machinery that is sensitive to temperature changes could in future be used to guide patients who may be at risk of sudden cardiac death.

"An underlying heart muscle disorder or electrical disorder of the heart could be diagnosed through a combination of electrocardiogram, echocardiogram, cardiac magnetic resonance imaging, and genetic tests," Rao said.

He said a patient who is diagnosed with such an underlying disorder and thus seen to be at risk of sudden cardiac death could be prescribed certain drugs or implantable cardiac devices to minimise the risk.

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