How Good Are You at Predicting Long-Term Outcome From the Cardiac Prepurchase Exam?

By Paul Basilio

A thorough prepurchase cardiac examination provides a unique opportunity to identify at-risk horses prior to competition. If found, the cardiac disease is likely to be mild, but performance-limiting and life-threatening conditions can be present in seemingly normal horses.

Fe ter Woort, DVM, DVSc, DACVIM, (LAIM), and colleagues recently completed a study to identify the most and least common cardiac findings on prepurchase examinations, and gauged how accurate cardiac prognoses are in predicting athletic outcomes.

“Over the years, we’ve found some really spectacular cardiac disease in horses that looked healthy on the outside,” Dr. ter Woort said here at the 65th Annual AAEP Convention in Denver. Shuttersotck/acceptphoto

The Horses

The retrospective study included 174 horses from her Equine Sports Medicine Practice in Belgium, as well as horses treated at the New Bolton Center in Kennett Square, Penn. Show jumpers, eventers, show hunters and dressage horses were represented, among others.

Horses that had undergone complete cardiac examination with echocardiography (ECG) as part of a prepurchase exam or within 4 weeks of purchase were included. Outcomes were assessed by an owner interview conducted by phone call or email.

“I also used FEI [International Federation for Equestrian Sports] data,” she said. “For those who are not familiar with that data, it’s like Facebook stalking for horses. You enter the name and you can see where they’ve competed, who rode them, what class they were in, and what their results were, provided they were competing in an FEI-sanctioned event. All these data are freely available.”

The Results

In 86% of the cases, a murmur was found on auscultation. Of those horse, the most common murmur by far was systolic (85%), followed by diastolic (14%) and continuous (1%). About 8% had an arrhythmia, 3% had both an arrhythmia and a murmur, and 3% had neither.

More than 80% of cases of mitral regurgitation and 70% of cases of tricuspid regurgitation were classified as insignificant or mild. In these cases, there is trace regurgitation and no cardiac changes present, or a jet of regurgitation but no significant cardiac changes. Severe regurgitation was seen in around 5% for each type.

The Prognoses

“In 82% of the cases, we gave them an excellent or good prognosis based on the recommendations of the 2015 American College of Veterinary Internal Medicine consensus statement,” Dr. ter Woort said. “That was based on the diagnosis, the severity of disease, and the horse’s intended use.”

Horses were classified in the “good prognosis” category, even when there may have been mention of a small risk for the development of atrial fibrillation (AF) later in their career, for example.

A guarded prognosis was given to 11% of the horses with moderate or severe mitral regurgitation, moderate aortic regurgitation, cardiomyopathy, moderate tricuspid regurgitation, myocarditis, AF or frequent premature ventricular contractions (PVCs). Approximately 6% of the horses received a poor prognosis. These were horses with severe mitral regurgitation, large ventricular septal defect, AF, aortocardiac fistula, atrial tachycardia, or frequent PVCs.

Outcomes

To gauge the success of the prognoses given at the time of the PPE, Dr. ter Woort contacted the owners of horses who had at least 1-year of follow-up on record. She reached 42 owners of horses with good or excellent prognoses, and 8 owners of horses with guarded or poor prognoses.

“I wanted that number to be higher, but that’s the reality of calling owners and asking them how a horse that they brought in 9 years ago is doing,” she said.

Most of the horses with good or excellent prognoses were performing well or had been retired or euthanized for what the owners described as non-cardiac reasons.

“One horse that we gave a good prognosis to was not doing well,” she added. “That horse had mild aortic regurgitation on the pre-purchase exam and developed an aortocardiac fistula 3 years later that was picked up on a routine recheck. We went back and looked at the echocardiogram to see if we had missed anything, but we did not find anything.”

Of the 8 horses with guarded or poor prognoses, 7 did not do well. Three had heart failure and were euthanized, 2 had heart-related poor performance, and 2 had sudden death.

“We had 1 horse with a poor prognosis due to atrial tachycardia that did do well,” Dr. ter Woort said. “The reason it did well was because we treated it with a transvenous electrical cardioversion. After treatment, it was in normal sinus rhythm and did well.”

One interesting finding was that the grade of the murmur was not necessarily a good predictor for diagnosis or outcomes. Murmurs in horses with a good or excellent prognosis ranged from grade 1/6 to 6/6, murmurs in the guarded group ranged from grade 2/6 to 6/6, and the poor group showed grade 5/6 and 6/6.

“The horses with a poor prognosis only had loud murmurs, but the grade of the murmur did not predict the diagnosis or the outcome,” she explained. “If you have a horse with a Grade 5/6 murmur, you cannot say whether it has an excellent or poor prognosis. Just based on auscultation alone, you can’t tell whether it’s going to be no big deal or whether it will have a guarded prognosis, which is not something you want for an athletic horse.”

For most cases, a complete cardiac prepurchase exam can provide reassurance for the prospective buyer, but it also provides an opportunity to remove at-risk horses from sporting events, according to Dr. ter Woort.

“I think it’s clear that you can tell your clients at the time you hear a murmur that in 94% of the cases it will be no big deal,” she said, “but we should perform echocardiography to make sure your horse is not in the other 6%.”

Murmur Diagnosis

• Mitral regurgitation (50%) • Physiologic flow murmur (22%) • Tricuspid regurgitation (12%) • Aortic regurgitation (8%) • Ventricular septal defect (5%) • Other (3%)

Arrhythmia Diagnosis

• Sinus arrhythmia (3%) • Frequent APCs (3%) • Frequent PVCs (2%) • Atrial fibrillation (2%) • Atrial tachycardia (1 horse)