Atrial fibrillation in warmblood horses - Echocardiography, therapy, prognosis and outcome in 72 cases
Vorhofflimmern beim Warmblutpferd - Echokardiographie, Therapie, Prognose und Verlauf in 72 Fällen
Gehlen H, Stadler P
DOI: 10.21836/PEM20020603
Year: 2002
Volume: 18
Issue: 6
Pages: 530-536
Echocardiographic evaluation of 72 warmblood horses with atrial fibrillation was performed, using M-mode, B-mode and pulse-waved doppler echocardiography. There was no breed, sex or use predisposition when compared to the general hospital population. The mean age of affected horses was 12 years. 30 of these horses (42 %) had a history of poor performance. A heart frequency in rest over 55 beats per minute was seen in 18 horses. 3 horses showed peripheral oedema. During auscultation 42 horses (58 %) had additionally to total arrhythmia a heart murmurs. 22 horses showed no other sign of cardiac disease. In 50 horses (69 %) heart valve insufficiencies (mitral- and/or tricuspis valve insufficiency) could be detected during echocardiographic examination. 37 horses of them (51 %) had atrial dilatation. 19 horses showed a generalized cardiomegalie. In these cases therapy was not carried out, because of the poor prognosis. 34 horses had normal heart dimensions. Quinidine sulfate- infusion was used for treatment in 46 horses (64 %). 30 horses (65 %) converted to sinus rhythm, 25 of them had normal cardiac dimension, 5 horses had mild to moderate atrium dilatation. Treatment was not successful in 16 horses (35 %), 9 of these horses showed atrial dilation and 8 horses had normal dimensions. 23 horses converted to regular sinus rhythm with the first infusion. Horses with moderate mitral valve insufficiency and moderate left atrium dilatation, who did not converted to normal sinus rhythm during the first chinidin sulfat infusion, were treated with an angiotensin converting enzyme blocker and after this the second infusion was successful in 7 horses, unsuccessful in 14 horses (6 horses with two infusions, 8 horses with 3 infusions). 26 horses (36 %) with atrial fibrillation stayed untreated, 10 of them (39 %) were euthanized. It was concluded that the assessment of prognosis for successful therapy of atrial fibrillation is mostly difficult, because it depends on duration of the arrythmia, which is mostly unknown, and also associated cardiac diseases. In general therapy of atrial fibrillation should be carried out as soon as possible, after diagnosis and echocardiographic examination. The combination of atrial fibrillation with poor performane, which is often seen in racing horses, is in warmblood horses mostly due to additional cardiological diseases of higher degree (mostly mitral valve insufficiencies with left side dilatation), thus prognosis for successful therapy is in this cases poor. The size of left atrial diameter is a great value for determination the prognosis of successful therapy. Left atrial diamneter greater than 145 mm had a poor prognosis for successful therapy and a higher risk for recurrent atrial fibrillation as well as for further use. In our study 25 out of 46 horses without or only with moderate left atrial dilatation could be converted to normal sinus rhythm (54 %). Thus in this cases the prognosis is good. As found out in different other studies intravenous quinidine therapy was a safe and effective means of converting atrial fibrillation in warmblood horses in our study as well (side or toxic effects only 9 %, recurrent atrial fibrillation only 10 %).