At the U.S. Eventing Association Safety Summit in the summer of 2008, it became apparent that there are many more questions than there are answers when it comes to some of the troubles that have bedeviled the sport of eventing.

But in at least one area, that’s going to change.

The USEA Cardiovascular Study Task Force has been teleconferencing regularly since the Safety Summit and is preparing to collect some baseline data on what happens to a horse’s heart and lungs during the cross-country phase via a pilot study at the Plantation Field CIC*** (Pa.) in September.

It’s the first of what may be many studies seeking to unravel the mystery behind many of the horse fatalities that have occurred at recent events, when apparently healthy and well-prepared equine athletes have been felled on course by catastrophic cardiovascular events.

In addition, a proposed U.S. Equestrian Federation rule change will require that any horse that dies during the course of an event be necropsied, and the USEA will continue to cover the cost of the procedure, a policy put in place after the Safety Summit.

The Heart Of The Issue

The idea of a USEA-funded study of cardiovascular issues in event horses had been percolating for several years, according to Jo Whitehouse, the USEA’s executive director.

After the 2008 Red Hills event in Florida, during which two horses—Jonathan Holling’s Direct Merger and Melissa Miller’s Leprechauns Rowdy Boy—died suddenly from what appeared to be cardiovascular issues, Whitehouse called Kent Allen, DVM, the chairman of the USEF Veterinary Committee, with a renewed sense of urgency to make the theoretical project reality.

By the time the Safety Summit took place in June, three months later, the planning had already begun.

The task force is chaired by Allen and includes veterinarians Catherine Kohn, who conducted the heat studies prior to the 1996 Atlanta Olympics; Carol Clark, a partner at Peterson & Smith Equine Hospital in Ocala, Fla.; Eleanor Green, professor at the University of Florida College of Veterinary Medicine; and Mark Revenaugh, owner of the Equine Performance Institute in Mulino, Ore.

The group also includes two human cardiologists—Mark Hart, owner of Amy Tryon’s Poggio, and Lynn Cronin, an amateur eventer from Michigan. Leigh Anne Claywell, the USEF director of competitions, Whitehouse, and Wendy Weinstein of the USEA round out the panel.

At issue are the mysterious and sudden deaths of horses that seemingly had no health problems, were well-prepared for the event and were not struggling on course.

Kingpin, ridden by Mike Winter, suffered a hemorrhage of the large vessels of the abdomen at the Rolex Kentucky CCI*** in April. In 2008, Tigger Too, ridden by Lauren Kieffer, died from an aortic rupture on course at the Jersey Fresh CCI***, just weeks after the loss of Direct Merger and Leprechauns Rowdy Boy at Red Hills from pulmonary hemorrhages. In 2007 Laine Ashker’s Eight Saint James Place also died at the Jersey Fresh CCI after rupturing an abdominal blood vessel on cross-country.

Although sudden death from a cardiovascular issue isn’t a new phenomenon, many eventing enthusiasts believe that it’s happening with increasing frequency. Experts also wonder how many other horses have experienced similar problems that went undetected.

For example, a horse might have suffered a ruptured aorta a few strides before a fence but still tried to negotiate the obstacle. The horse might then have seemed to sustain a fatal injury in the ensuing fall. Without a necropsy, it might never be known that the horse was in distress before even attempting the obstacle.

No single kind of injury is to blame; rather, there are several different types of injury, all residing under the same cardiovascular umbrella.

A spontaneous rupture of one of the large vessels—such as the aorta, which pumps oxygenated blood from the heart to the rest of the body, or the large vessels of the abdomen—will lead to sudden death and can only be diagnosed via a post-mortem examination.

Exercise-induced pulmonary hemorrhage, or bleeding in the lungs during exercise, can be a mild affliction resulting in just a trickle of blood from the nose with little or no impact on performance. Or, a horse can suffer a rupture of a pulmonary vessel inside the lung, resulting in sudden death.

First Foray Into Research

The pilot study at Plantation Field will hopefully indicate where future studies should be focused in order to better understand how the stress of cross-country affects a horse’s heart and lungs and what can be done to minimize cardiovascular problems.

The study will rely upon the cooperation of the CIC*** competitors, who will have a choice of whether or not to participate.

Kohn, a professor at the Ohio State University College of Veterinary Medicine, explained that researchers would establish a baseline by examining horses prior to cross-country day (likely on Friday), while they’re quiet and at rest. A standing echocardiogram will be performed to evaluate the heart, and an ultrasound will be conducted on the horse’s lungs. Both procedures are non-invasive.

A second echocardiogram will be conducted immediately after cross-country, as the horses pull up at the finish, she said. Data from the pre-competition exams can then be compared to those performed after cross-country to discover what changes occur during competition.

In addition, a limited number of horses will be fitted with small on-board EKG monitors that will record as the
horse is galloping, gleaning valuable data about what actually occurs to the horse’s heart as he’s traveling the cross-country course. The researchers will only have about eight of the EKG monitors available, so this data will be collected from a much smaller pool of horses, Kohn said, but she hopes to have as many participants as possible for the pre- and post-cross-country exams.

Whitehouse acknowledged that taking part in the study might be a “minor inconvenience” to riders, but she expressed hope that many, especially the sport’s most experienced, will participate.

“If riders would support this effort, it would be really appreciated,” she said. “Hopefully, it will give us a look at what’s going on with the horse’s heart and lungs during competition.”

The data from the pilot study can also be compared with data collected during the heat studies prior to the Atlanta Olympics, which may help illuminate any differences between the way horses handle cross-country during long-format and short-format events, to see if that area merits further study, Whitehouse said.

She also cautioned that the study is only a first step.

“The scope of this [project] could be absolutely immense,” she said.

The pilot study is designed to better define areas that need further research, which will then hopefully be explored by university research teams, here or abroad. The USEA is the sole source of funding for the pilot study and has committed $20,000.

“This year, we can cover it,” Whitehouse said. “In future years, it could be a lot bigger than the USEA.”

The veterinarians and other experts are donating their time, she added.

Whitehouse also noted that the data collected might be of use in another study investigating variations in speed along a cross-country course, conducted by John Staples and amateur eventer Reed Ayers. The two designed a study measuring changes in speed with radar guns and GPS units and presented their preliminary findings at the Safety Summit.

The results of the cardiovascular pilot study, the further findings of the speed study, and the results of a two-year USEF frangible pin study will all be shared at the USEA Annual Meeting in Reston, Va., in December, Whitehouse said. 

All About Necropsies

Another U.S. Eventing Association initiative that emerged from the 2008 Safety Summit was the organization’s offer to pay for the cost of a complete necropsy for any horse that died during the course of a competition.

The veterinary portion of the meeting emphasized the need to collect as much data as possible about fatalities to better understand why they happen, and by removing one perceived hurdle—the cost of a post-mortem examination, which can be several hundred dollars—officials hoped to encourage the practice.

The USEA leaders have now decided to go even one step further, according to Executive Director Jo Whitehouse, and are working with the U.S. Equestrian Federation to enact a new rule mandating a post-mortem examination for any horse that dies during an event. The rule could possibly be enacted as soon as Dec. 1, as an extraordinary rule change.

The death of a horse—especially when it’s as unexpected and tragic as the recent sudden cardiovascular-related deaths at competitions have been—is, of course, a terribly traumatic event, and the last thing on an owner’s or rider’s mind at that point is having the horse necropsied. Many owners may not be familiar with what’s involved or why the exam is so important.

The post-mortem examination is crucial because sudden death is rarely due to a condition that was previously known, or is able to be diagnosed before the fact. It’s only via a necropsy that the cause of death can be discovered.

Another aspect emphasized at the Safety Summit was the importance of doing a necropsy at a university or state animal health testing facility that’s equipped to conduct the kind of thorough examination necessary for useful data collection.

All veterinarians are trained in how to conduct a post-mortem examination, and any veterinarian can do what’s known as a gross necropsy—usually involving opening the horse up and looking for anything obvious, and taking tissue samples to send to a lab. But the complete examination that can be conducted in a specialized setting is much more valuable, according to Richard Jakowski, DVM, Ph.D., a veterinary pathologist at Tufts University Cummings School of Veterinary Medicine (Mass.), who has been conducting post-mortem examinations for 30 years.

Veterinary pathologists, who perform necropsies at these specialized facilities, have at least an additional three years of training after veterinary school. In addition, the pathologist will be the one to examine any tissue samples taken—if the exam is conducted by a practitioner who sends the samples to another lab, the analysis is conducted by someone else who has not actually seen the horse’s body.

“There’s a disconnect there—two different people are doing the exam,” Jakowski noted.

A complete post-mortem involves examination of just about every part of the horse’s body, said Jakowski, who prefers to call the process an autopsy or post-mortem, rather than a necropsy.

Pathologists visually examine the body structures and organs and also take tissue samples for further testing and microscopic evaluation. In the event of a sudden, unexplained death, the heart and lungs are the first areas of interest and most likely culprit, although an issue involving the brain is also possible, he said.

If a horse has suffered an aortic rupture, an event that Jakowski called “relatively rare,” it will be immediately apparent upon examination because of massive hemorrhage throughout the horse’s chest. The rupture generally appears where the aorta leaves the heart to deliver oxygenated blood to the rest of the horse’s body.

“The lesion [rupture] is very obvious,” he said. “There’s almost no reason to do microscopic evaluation because usually we don’t find any underlying problem. It’s a mysterious disease, and we don’t know why it happens.”

There are some cases of sudden death in which a post-mortem will deliver only negative findings, Jakowski explained, meaning that pathologists are only able to rule out causes of death. In these cases, it’s a matter of “diagnosis of exclusion” and a cause is determined by process of elimination.

Cardiac arrhythmias occur when something goes wrong with the electrical activity in the heart, and an irregular heartbeat develops. But it’s difficult to find evidence of an arrhythmia during a post-mortem, Jakowski said, so often the conclusion is reached because there’s no other obvious cause.

As valuable as a post-mortem examination is, Jakowski acknowledged that it’s sometimes a difficult thing for an owner to agree to when a beloved animal dies suddenly. The idea of the horse being surgically examined after death can be unsettling.

“I don’t know if there’s any way to soften that,” he admitted.

With horses, because of their size, the post-mortem examination is a more difficult undertaking than it is with small pets. With dogs and cats, it’s often possible to do a cosmetic autopsy, in which the body is returned in a viewable condition with the head intact and limbs attached, Jakowski said. But due to a horse’s size and structure, that’s not possible when conducting a complete post-mortem.

At Tufts, the remains are usually disposed of after the post-mortem, rather than being returned to the owner, although the remains can be cremated and returned, Jakowski said.

“We have to invade the body, so to speak,” he explained, in order to fully evaluate a horse’s organs and tissues. But, he added, “We do it as carefully as we can.”