Colour flow Doppler echocardiography in horses with cardiac murmurs.

Thirty-two horses with cardiac murmurs typical of tricuspid, mitral and aortic regurgitation were studied using colour flow Doppler echocardiography. The dimensions and duration of any regurgitant signals, recorded at the cardiac valve suspected as being the site of origin of the murmur, were measured. Results were compared with flow signals described at the valves of normal horses (Blissitt and Bonagura 1995). Horses with murmurs suggestive of tricuspid (n = 8) and aortic (n = 8) regurgitation showed larger regurgitant signals at the tricuspid and aortic valves respectively, than has been reported in normal horses. Horses with murmurs suggestive of mitral regurgitation (n = 8) had a regurgitant signal of longer duration than occurs in normal horses, but the jets were not larger. Comparison of two groups of horses with low and high grade murmurs of tricuspid regurgitation, showed that horses with louder murmurs had significantly longer jets of larger area than those with low grade murmurs. This study demonstrates that colour flow Doppler echocardiography is a sensitive technique for the detection of valvular regurgitation in horses. However, quantification of jet size and duration are important for distinguishing physiological backflow which occurs in normal horses (Blissitt and Bonagura 1995) from valvular regurgitation associated with cardiac murmurs.