April 24, 2008

A British study on 526 race-fit thoroughbred horses found that those with heart murmurs did not appear to perform any differently to those without.

The study, led by Dr Lesley Young, an equine cardiologist in Suffolk, explored the hypothesis that cardiac valvular regurgitation negatively impacted on race performance.

Cardiac murmurs associated with valvular regurgitation are common in conditioned performance horses, the authors wrote, but their association with athletic performance is unknown.

The 526 thoroughbreds used in the study were engaged in both flat and jump racing, over distances from 1000m to 6400m.

The horses underwent cardiac testing to determine the presence and severity of either an audible cardiac murmur or valvular regurgitation. The race performance of the horses was then determined using a standard regression approach.

The authors found that while the prevalence of murmurs and of regurgitation varied significantly between racetypes - generally increasing from two-year-olds to chasers - there were no consistent associations between racing performance and either grade of murmur or regurgitation.

The data showed that neither regurgitation nor murmurs were negatively associated with Timeform rating, an index of British racehorse quality, in any of the groups of racehorses studied.

The study was entitled Heart Murmurs and Valvular Regurgitation in Thoroughbred Racehorses: Epidemiology and Associations with Athletic Performance, was published in the Journal of Veterinary Internal Medicine in March-April, 2008.

Dr Young was joined in the study by K Rogers, of the Epidemiology Unit, Animal Health Trust, Suffolk; and J L N Wood, from the Department of Veterinary Medicine, Cambridge Infectious Disease Consortium, University of Cambridge.