A Simple Step Toward Better Healing

By Jane Farrell

Heart-attack patients’ recovery can improve if hospitals keep to regular day-night cycles during the first few days after the attack, research shows.

Previous studies have shown that circadian rhythms, or day-night cycles, can affect the timing of a heart attack. But this is the first investigation to show the importance of keeping to circadian rhythms in the first few days after the attack.

The findings, by researchers from the University of Guelph, in Toronto, were published in the journal Circulation Research.

As anyone who’s ever been in an intensive-care unit knows, hospital ICUs are busy places at night, with noise, light, nursing and medical procedures, and other interruptions that disturb acutely ill patients.

The researchers used a mouse model in reaching their conclusions. The team induced heart attacks in mice, and then compared rodents held under normal light and dark cycles with others whose cycles were disrupted for five days after the attacks.

Heart repair was impaired in the mice that had their circadian rhythms disrupted.  “These mice were likely to go more quickly to heart failure,” said Prof. Tami Martino of the Department of Biomedical Sciences. . “Disrupting circadian rhythms for the first few days after a heart attack worsens the disease outcome.”

The first five days after a heart attack are crucial for proper scar formation, removal of dead tissue, proliferation of new cells and growth of blood vessels in the heart.

Martino said the study showed a “simple way to better practice medicine  to improve the outcome from heart attacks by considering normal circadian rhythms.”