The M.D. shouts “Clear!” as the defibrillator jolts the patient with electricity. This is a familiar scene in medical shows, but we may start seeing it in the stables, too, now that veterinarians are using electric shock to treat atrial fibrillation in horses.

In “a fib,” [ā-fib] as the disorder is called, the upper chambers of the heart do not beat in a coordinated fashion. The irregular heart rhythm reduces an animal’s ability to exercise. Eventually, the problem leads to heart disease.

Traditionally, drugs were used to get the heart beating at a normal rhythm, again. But this practice has been associated with some cardiac risks.

Because the equine chest is so large, electrodes are not placed on the surface. Instead, wires are passed through a large vein in the neck and put in direct contact with the heart. In many cases, the results are shockingly good.