A five-year-old warmblood mare with atrial fibrillation was treated wi
th quinidine sulphate. The atrial rhythm changed to atrial flutter and
, because there were toxic effects, the treatment was discontinued, Se
ven months after the occurrence of the atrial flutter, treatment with
a rapid atrial pacing technique restored a normal sinus rhythm. One ye
ar after the pacing therapy the horse was still in sinus rhythm and ha
d been brought back into training.