Sudden death caused by heart attacks can be triggered by changes in body temperature, according to new research that might explain why athletes sometimes die inexplicably during play and infants pass away while sleeping.

The study, published in the Journal of Physiology, adds to the list of potential causes of cardiac arrhythmia, which also include genetic defects and other underlying cardiovascular problems.

Lead researcher Peter Ruben, a physiology specialist at Simon Fraser University, found that body temperature increases can cause changes in proteins that underlie electrical signaling in the heart in ways that are similar to the stress of exercise — increasing the risk of fatal arrhythmia and, 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,” Ruben explained. “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 a protein that when normal body temperature rises, during exercise, or falls during sleep, the affected proteins no longer function normally. This can cause the electrical signal in the heart to become erratic, triggering an arrhythmia and, potentially, death.

"For many years, we have studied sodium channels, the proteins in our hearts that produce electrical signals,” he added. “An earlier study of ours found that temperature changes are a trigger for some seizure disorders. We imagined that cardiac arrhythmias are like seizures and wondered whether they might share the same triggers."

Ruben said electrocardiograms, genetic screening, and lifestyle management may help reduce the risk to individuals who are prone to such heart conditions.