The Live Equine Heart: A First Look (video incl)

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 team works to view the colt's ventricular septal defect using an intracardiac ultrasound probe.

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.

The condition is congenital (the foal was born with it), and is caused by the septum stopping growth before the area can close up during fetal development. The defect is not inherited.

The defect causes a loud heart murmur, which was detected when the foal was being evaluated for a fever caused by an unrelated problem. John Gurley, MD, associate professor and director of the University of Kentucky catheterization lab, used a heart catheter (passed through the jugular vein) and a special ultrasound probe to view the colt's heart from the inside. Debbie Creighton, clinical account manager for Siemens Medical Solutions in the AcuNav Division, provided the equipment and technical assistance for the procedure.

Fairfield Bain, DVM, Dipl. ACVIM, ACVP, ACVECC, the veterinary internist who is treating the foal at Hagyard-Davidson-McGee veterinary hospital, asked Gurley if he would attempt a procedure to correct the problem at the clinic. Bain says he sees about 8-10 horses a year with this type of defect, and until now,  they have had to be medically managed. While some have successfully performed with these defects, the great majority eventually show the long-term effects of heart failure. Gurley said that in humans, "If you're not extremely active, your lungs can handle (this type of defect), but at age 50, clinical signs start appearing."

In horses, just as in children, VSDs can sometimes self-repair, but this colt's hole is in a non-muscular area of the septum and is highly unlikely to close on its own, says Bain.

This colt is Gurley's first equine patient. He noted, "The (heart) catheter and imaging skills are really things that do not currently exist in veterinary cardiology." He viewed the hole using intracardiac (within the heart) ultrasound with the foal sedated and standing, the first time this has been done in a horse; the hole measured about 1 cm in diameter. (Click here to see what they saw. You will need QuickTime to open this 8.5 Mb file. Also check back to see more images of the procedure.)

Bain leaned curiously toward the screen and said, "We've done transesophageal (via the esophagus, or tube that leads from the mouth to the stomach) ultrasounds before, but not heart catheter (ones)."

The hole is allowing blood leakage between the heart's chambers and therefore is disturbing pressures in the chambers. Gurley and Bain think that installing a closure device to "plug" the hole would be feasible without interfering with the nearby valves that prevent backflow of blood. (Open-heart surgery to correct heart problems would be impossible in a horse due to its narrow-chested anatomy.)

Gurley repeated the process of finding the defect five times, each time mapping the anatomy of the cardiac structures as he advanced with the catheter. This repeatability ensured that it was a workable procedure for going back in to install the closure device.

Engineers have been contacted with the measurements of the hole, and they will decide what type and size device will best suit the foal. The closure devices are called amplatzers and are made of a nickel-titanium alloy and fabric. Once installed, the tissue of the heart covers the margins of the device, creating a smooth wall of endothelium (organ lining) where the hole once was and sealing the defect. In human medicine, holes up to 38 mm (about 1.5 in) have been repaired in this manner.

Gurley and Bain hope to install the device within a few weeks, because the colt is growing quickly and these operations are more successful on younger, growing individuals. The device is likely to cost about $3,000. Each ultrasound probe (a new one must be used for each procedure to avoid contamination) costs around $2,500. "Fortunately,the animal's value and potential are of the level that the owners are willing to pursue cutting-edge technology in an effort to correct the problem.  It may not work, but they are willing to give it a try," said Bain.

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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