HISTORY AND CLINICAL FINDINGS

During a routine check up examination on a group of horses of a riding school in Shiraz, Iran, a 4-year old Arubian horse was observed to have very slow heart rate, in the range of 16 to 18 beats per minute, (bpm) on auscultation. A base apex electrocardiogram (ECG) was recorded (using Cardiostat 701, Siemens, Germany) to determine the type of arrhythmia causing bradycardia. At the time of ECG recording, the horse was normal with no apparent sign of any disorder, and respiratory movements and body temperature were in normal range. The horse was given a light exercise and examined immediately after the exercise and for 15 minutes thereafter. The heart rate increased to 80 beats per minute by light exercise but returned to pre-exercise rate 5 minutes after the end of exercise