It's another example of the obesity paradox, an unexplained phenomenon where obese patients who do have a heart attack live longer than thin ones.
The mice were given 60 percent of calories from animal fat before experiencing heart attacks experienced about half as much heart damage as mice that ate a control diet. The benefit was greatest among mice that ate a high-fat diet for one week before the heart attack, but in mice that ate a high-fat diet for six weeks, the protective effect disappeared, which is a confounding factor preventing reading too much into the study.
W. Keith Jones, PhD, of Loyola University Chicago Stritch School of Medicine, believes that in the short-term, a high-fat diet protects the heart because of autophagy - self-digestion by eukaryotic cells: Proteins damaged by the heart attack are removed from heart cells as if they were garbage, thus increasing the chances the cells will survive. Acutely, a high-fat diet increases levels of a molecule in the blood that activates protective pathways in heart muscle. This increases the readiness of the "garbage trucks," which means that the cell becomes resistant to damage when the heart attack occurs. As a result, more heart muscle survives.
Published in the American Journal of Physiology - Heart and Circulatory Physiology.