CARDIOLOGY
the horses were grouped by breed. For statistical purposes, the horses were also divided into lower, intermediate and upper divisions based on their past performance. In addition to collecting information about the arrhythmias, the investigators also noted how long each horse had a heart rate (HR) >200 beats/min. A total of 131 horses were enrolled from events across the United States, but 56 ultimately had to be excluded from the study—39 had excessive ECG artifacts during the event, 16 failed to finish the event, and 1 had pre-existing atrial fibrillation.
The results
There were large differences in the average HRs for each division. Horses in division 1 averaged 176.3 beats/min, while division 3 averaged 199.7 beats/ min. The maximal HRs for each division were 196.5, 205.8 and 215.9 beats/min, respectively. Less than half of the horses in division 1 attained an HR of 200 beats/min, while all but 1 horse in division 3 had an HR of 200 beats/min or greater. “For the division 1 horses, an average of 13% of the cross-country event was spent with an HR of 200 beats/min or greater, whereas the horses in division 3 spent an average of 60% of the event time over 200 beats/min. In at least 1 horse, the HR was more than 200 beats/min for the entire event. To me, these findings illustrate the phenomenal difference in work between the divisions.” The arrhythmia findings shook out in a similar manner.
“In all of the arrhythmia categories, horses in division 1 had a lower frequency than horses in division 3,” Dr. Durando said. “No horses in division 1 or division 2 had complex arrhythmias, whereas 20% of horses in division 3 did.” In fact, horses in division 1 were 94% less likely to have an arrythmia and 98% less likely to fulfill the Martin criteria (more than 2 premature depolarizations) than the horses in division 3 were. Age and increasing maximal HR were 2 predictors of couplet arrhythmias, and the time the HR was >200 beats/min was a predictor of triplets and complex arrhythmias. Division was also significantly related to the severity of the arrhythmia. “We were surprised at the number of horses that had simple and complex arrhythmias during crosscountry,” Dr. Durando explained. “Around 56% had at least 1 premature depolarization during the event.” Dr. Durando’s team also discovered a critical need for better ECG-collecting technology. The set-up used in the study was not particularly well received by the riders, and reliability was an issue. “It would facilitate the collection of more data and gaining more information if we had a somewhat easier way of doing this,” she said. “[It is difficult] to collect ECGs from these horses when they're exercising so intensely. Cross-country is probably one of the hardest sports to try to do because of the motion artifact that you're going to get with horses going over jumps and changing speeds and riders.” MeV
Purina Omolene Horse Feed Now Provides Gastric Support The Purina Omolene horse feed lineup now contains the Outlast Gastric Support Supplement. This addition to the Omolene feed line provides gastric support in every meal, which benefits most horses. “Research shows up Anna Pesta, PhD to 90% of active horses are at risk for experiencing gastric discomfort,” said Anna Pesta, PhD, equine nutritionist for Purina Animal Nutrition. “Adding the Outlast supplement to Omolene horse feeds was a logical decision because it allowed us to provide the benefit of daily support of proper gastric pH to a wider variety of horses. 6
Issue 9/2021 | ModernEquineVet.com
Omolene feeds provide fuel for performance in any horse, from active pleasure to top equine athletes. This lineup of textured feeds also works well for horses that are picky eaters or who don’t eat pelleted feed, horses needing to gain weight, racehorses and horses with high caloric demands. Look for the Outlast Gastric Support Supplement seal on each of these Purina Omolene feeds: • 100 Active Pleasure: For horses in light to moderate work. • 200 Performance: For horses in competition, broodmares and yearlings. • 300 Mare & Foal: For foals, weanlings, yearlings and pregnant or lactating mares fed with foals. • 400 Complete Advantage®: For competition horses. • 5 00 Competition: For hard-working and endurance equine athletes. MeV
