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46 TheHorse.com THE HORSE October 2015 noted no dramatic abnormalities in heart rate, rhythm, or function or fluid buildup in the lungs. "We hypothesized that some horses might develop arrhythmias dur- ing intense exercise that resolve when exercise is discontinued," says Kohn. "Therefore, we think it is important to actually record the heart rhythm, the electrocardiogram, while horses compete to describe the transient cardiac arrhyth- mias while horses compete." Kohn says it's also important to moni- tor horses during the early part of the recovery period because that's when arrhythmias are seen. "Now that we have a more reliable way to record exercising ECGs in the field, our next step will be to study a large group of eventing horses at all levels of competitions," Kohn contin- ues. "Our goal is to describe the electrical activity of the heart in healthy horses dur- ing cross-country competition." Post-Mortem Policies While studying what happens to horses during exercise and competition has been important to the CPRG, learning as much as possible after a case of sudden death is also crucial. Kohn hopes to help educate horse owners about the impor- tance of obtaining necropsies on horses that die during competition. "Some people understandably find the thought of allowing a necropsy on their horse quite distasteful and are unwilling to give permission for the procedure," she says. "Perhaps if horse owners understood how important a contribution their particular horse might make to our understand- ing of causes of sudden death, owners/ riders would be more accepting of the necropsy." Due to the importance of this informa- tion, the USEA now requires and pays for a necropsy of every horse that dies in competition. The USEA's research group has developed a protocol to forward to the person responsible for performing the necropsy on a horse that dies in competi- tion so that each report is standardized. "Post-mortem drug testing of these horses is also mandatory," says Kohn. "We want to know what medications the horse has been given so that we can iden- tify associations that may exist between administration of a particular drug and sudden death during competition." The CPRG has also discussed banking the heart and other tissues for additional detailed examinations and future tests of sudden death cases in eventing. The USEA is not the only group requir- ing necropsies. Kohn says the Fédéra- tion Equestre Internationale (FEI) now mandates necropsies and collects data on all horses that die in FEI competitions. Prior to 2013, it was nearly impossible to determine how frequently collapse or sudden death occurred at United States Equestrian Federation (USEF) events because a reporting procedure wasn't in place. On August 1, 2013, GR 843, a new USEF rule, also known as the "collapse rule," took effect as part of an overarch- ing "Catastrophic Incident Protocol." The goal is to keep USEF informed of any col- lapses and give it the power to investigate by appointing a veterinarian to examine the horse or pony. In addition, the animal can be drug tested, according to other USEF rules. The rule requires owner, rider, and/or trainer cooperation. The USEF also has a Horse Welfare Review Panel that reviews fatalities and collapses, says Stephen Schumacher, DVM, chief administrator of USEF's Drugs and Medications Department. This panel reviews necropsy and drug test re- sults, steward/technical delegate reports, veterinary records, eyewitness reports, personal accounts of those involved with the horse, any available videos, and more—all in an effort to get a clear pic- ture of what happened and why. Because even with a necropsy, says Schumacher, the cause of death can be impossible to pinpoint. Take-Home Message Despite the current research and vari- ous organizations' efforts, the reasons why sudden death happens remain a puzzle. "I don't think anyone should expect that we're going to find a cure or a way to prevent all fatalities in equestrian sport," says Kohn. "Fatalities do occur in other sports and among human athletes, as well. Still we aim to prevent the pre- ventable and mitigate risk by thoroughly studying this problem among equine athletes." It might be a puzzle that always has some missing pieces, but as more becomes known, a partial picture of this malady might emerge that can help save SPORTS MEDICINE ABOUT THE AUTHOR Sarah Evers Conrad lives in Lexington, Kentucky, and has been an equestrian journalist since 2000. She has worked on staff at The Horse, Equestrian, and USEF. She currently freelances and owns All In Stride Marketing, a digital marketing firm. A Horse-Human Connection Rikke Buhl, DVM, PhD, professor and section head of Medicine and Surgery in Large Ani- mal Internal Medicine at the University of Copenhagen, in Denmark, is conducting cardiac research that could prove promising for preventing sudden death. She's trying to determine if potassium ion channel defects could be causing cardiac arrhythmias in horses similar to what's been described in humans and dogs with the cardiac disease Long QT syndrome (LQTS). This condition involves an increased interval between the Q and T wave (two of the six waves that indicate electrical events during a heartbeat) on electrocardiogram (ECG) and problems with potassium ion channel function, which interrupt electrical signals in the heart that cause it to beat. While researchers have not yet confirmed LQTS to exist in horses, they have character- ized horses' QT interval and how it changes due to heart rate and racing intensity. "With the new tools developed by the Equine Cardiac Group (at the University of Copenhagen), the presence of LQTS will be investigated in horses by screening ECGs from a large pool of horses with different genetic backgrounds," Buhl says. "Genetic sequencing will be performed on blood samples from this population and from horses with sudden death to describe mutations in the potassium channels in horses." If the team finds LQTS to exist in horses, the next step might be developing a blood test, an ECG test, and possibly a genetic database that identifies mutations that cause sudden death in horses.—Sarah Evers Conrad Cardiac and/or pul- monary failure are found to be the most common causes diag- nosed on (equine) post- mortem examinations." DR. RIKKE BUHL