Cardiac Morphology and Heart Murmurs in Elite Eventing and Dressage Horses

Abstract

Introduction Training related cardiac adaptation is documented in Standardbreds and Thoroughbreds, including an increased incidence of AV valve regurgitation. In Warmbloods less is known about training effects on cardiac function or subclinical valve regurgitation. Methods Fifteen adult untrained Warmbloods (aged 3.8?±?0.7 years) were compared with fifteen adult Warmblood eventers (aged 11.4?±?0.9 years) competing at CIC2* (group 1, n?=?5) and CCI2*, CIC3*, CCI3* and CCI4*levels (group 2, n?=?9) and fifteen healthy adult Warmbloods competing at advanced dressage (group 3, n?=?5), Prix Saint Georges, Intermediate or Grand Prix (group 4, n?=?10) levels (mean age 10.3?±?0.7 years). The presence of heart murmurs, valve regurgitation and echocardiographic parameters were evaluated, and training intensity was scored. A correlation was found between bodyweight and not height. Differences in cardiac morphology were compared using General Linear Models with post-hoc Bonferroni correction (SPSS version 20), using group and bodyweight as covariates. Significance was set at P<0.05. Prevalence of audible heart murmurs and valvular regurgitation was higher in eventers (0?20% and 29?79%, respectively and dressage horses (7?40% and 7?60%, respectively) than controls (0?20% and 7?20%, respectively). Interventricular septum in diastole (IVSd, left ventricular mass (LVM) and LV mean wall thickness (LVMWT) were greater in groups 2 and 4 than controls; group 4 also had a greater pulmonary artery diameter (PAD) and LV posterior wall (LVPWd). Group 1 showed a greater LVMWT; group 4 a greater end point septal separation (EPSS). Training intensity influenced in both categories IVSd and MWT; in eventers also the right ventricular diameter in diastole and in dressage horses also LVPWd, LVM, EPSS and PAD. Elite eventers and dressage horses showed an increased prevalence of audible murmurs and valvular regurgitation. Cardiac adaptations resembled those associated with resistance and endurance training. Increased performance level and training intensity accompanied increased cardiac muscle thickness and volume. These effects should be considered during sales and performance evaluations. Ethical Animal Research Evaluated by the Animal Ethics Committee of Utrecht University and owner consent was obtained. Sources of funding:?Faculty of Veterinary Medicine, Utrecht University. Competing interests:?none.