Hibernating woodchucks offer clues to sudden cardiac death

When woodchucks hibernate they enter a profoundly altered physiological state: their body temperature drops (often as low as freezing) and heart and respiration rates slow dramatically. These hibernating animals have been found to be more resistant to cardiac arrhythmias and sudden cardiac death. Electrophysiologist Lai-Hua Xie and his colleagues examined muscle cells isolated in winter and summer from woodchucks. The researchers monitored the release and uptake of calcium ions when the cells were activated. They found that in winter the membrane system in muscle cells that stores and releases calcium had less leakage of calcium, released more of it during excitation and took it back up faster than in non-hibernating animals. The effect, Xie says, is a "higher resistance to arrhythmia in woodchucks in winter. Understanding these cardiac adaptive mechanisms in hibernators may suggest new strategies to protect non-hibernating animals, especially humans, from fatal cardiac arrhythmias."