Peter Ruben (seated) and PhD. students  Mena Abdelsayed (left) and Colin Peters (standing).

Sudden death caused by cardiac arrhythmia can be triggered by changes in body temperature. This is the finding of SFU professor Peter Ruben and his collaborators, Mena Abdelsayed and Colin Peters, published today in the Journal of Physiology.

The soccer player who drops dead in the middle of a game, or the infant who dies during sleep is often a victim of arrhythmia. Sudden cardiac death has several causes, including inheritable mutations in our DNA affecting structure and function of proteins in the heart. Ruben says that, “By studying the proteins that underlie electrical signaling in the heart, and by subjecting those proteins to conditions that are similar to the stress of exercise, we found that in some cases, temperature can cause changes that trigger arrhythmia.”

Ruben explains that 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. He adds, “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.”

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.

The DNA mutation that creates more temperature-sensitive proteins is very rare, but it can produce deadly results when combined with another arrhythmia trigger, such as changes in the acid content of our blood that occur normally as a by-product of exercise and sleep, particularly sleep apnea. Ruben notes that 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. Through a combination of electrocardiograms, genetic screening, and lifestyle management, some tragic deaths caused by cardiac arrhythmia may be prevented.

Read the story in the Vancouver Sun, 24 Hours and Shape magazine.

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