Atrial fibrillation: Echocardiographic findings

Seven horses with atrial fibrillation (of duration as long as 4 months) and ten normal warmblood horses were examined, using M-mode, 2-dimensional real-time (B-mode), pulsed-wave and colour coded Doppler echocardiography. Horses with atrial fibrillation had significant increases in the mean values for left ventricular internal diameter, as well as left and right atrial chamber size and significant decreases of fractional shortening compared with normal horses. In horses with atrial fibrillation the M-mode echocardiogram revealed the lack of an A-peak at the level of the ventricles, immediately below the septal leaflet of the mitral valve. In horses with atrial fibrillation pulsed-wave Doppler analysed tracings of tricuspid valve outflow showed the absence of the A-peak (A wave), which is associated with atrial contraction. The presence of a large systolic regurgitant jet associated with tricuspid valve insufficency was detected with colour coded Doppler echocardiography in the right atrium in two horses. M-mode, 2-dimensional real-time and Doppler echocardiography should be used to characterise valvular abnormalities and signs of atrial dilatation accurately as a prognostic indicator for therapy with quinidine sulphate.