On July 9, a human interventional cardiologist and an equine veterinarian in Lexington, Ky., successfully completed the first step of a landmark procedure to repair a heart problem in a 5-month-old Thoroughbred foal called a ventricular septal defect (VSD). At best, the problem could cost the colt his athletic career if not corrected. At worst, it could cost him his life.

The colt’s defect involves a hole in the wall (called the septum) between the left and right ventricles, or lower chambers of the heart, between the origins of the aorta and pulmonary artery. Normally, there is no communication between these two chambers so no blood flows from one to the other, but the defect in this foal’s septum allows a certain percentage of blood flow to be shunted from left to right instead of all of it passing out into the aorta as in the normal heart