ABSTRACT
To determine the prevalence of cardiac murmurs in clinically healthy horses of riding schools [Shiraz, Isfahan and Tehran]. Field Study. Five hundred and twenty six horses [475 sporting and 51 non-sporting horses]. Horses were divided into: sporting horses [jumping, race, endurance, training], non-sporting horses [foals, pleasure] and two different age groups:>2 and = 2 years old. Cardiac auscultation was done by two individuals using ordinary stethoscope and sensor stethoscope. Chi-square test and the frequencies as percent and Odd's ratio. Cardiac murmurs were detected in 378 out of 526 horses [71.9%]. In 88 horses, more than one murmur was detected. The most common and the least common cardiac murmurs originated from the tricuspid and pulmonary valves, respectively. Prevalence of murmurs on the tricuspid valve of horses > 2 years old was significantly greater than horses = 2 years old [p=0.005, df=1, Chi [2]=8.06].The prevalence of murmurs on the tricuspid valve of sporting horses was significantly greater than the non-sporting horses [p=0.001, df=1, chi [2] =10.20]. Our data suggested that training regimes in horses of >2 years old can be related with increase in the prevalence of systolic murmurs on the tricuspid valve. This finding may be due to the effect of training and occurrence of eccentric cardiac hypertrophy