Body temperature can trigger sudden cardiac death

Sudden death caused by an irregular heartbeat (cardiac arrhythmia) can be triggered by changes in body temperature, scientists have warned. While studying the proteins that underlie electrical signalling in the heart and subjecting those proteins to conditions that are similar to the stress of exercise, professor Peter Ruben from the Simon Fraser University at Burnaby in British Columbia found that in some cases, temperature can cause changes that trigger arrhythmia.

Ruben's team found a protein that is far more sensitive to temperature than normal. When normal body temperature goes up, for example during exercise, or goes down during sleep, the affected protein no longer functions normally. The disrupted protein function causes the electrical signal in our heart to become erratic, triggering an arrhythmia and, potentially, sudden cardiac death.

"With this new knowledge, people can examine their family histories and, if sudden cardiac death is part of that family history, or if they suffer from unexplained fainting, they can seek medical advice," Ruben advised in a paper published in the Journal of Physiology. When muscle cells in our hearts contract rhythmically and in a well-coordinated way, the heart efficiently pumps blood throughout our bodies.

When the rhythmic pumping action is disrupted by an arrhythmia, our hearts can no longer distribute blood. In extreme cases, this leads to sudden cardiac death. The electrical signal behind muscle contraction is produced by tiny protein molecules in the membrane of our heart cells.

"Temperature fluctuations modify the way all proteins behave, but some DNA mutations can make proteins especially sensitive to changes in temperature," the team explained. Through a combination of electrocardiograms, genetic screening, and lifestyle management, some tragic deaths caused by cardiac arrhythmia may be prevented.