The Effects of Verapamil Hydrochloride on Electrocardiographic (ECG) Parameters of Domestic Donkey (Equus asinus)

Verapamil hydrochloride, a calcium channel blocker, has been used in domestic animals. Its effects on electrical activities of the heart of donkeys were studied in this preliminary research work. This experiment was carried out on 10 healthy donkeys ranging in age from 4 to 7 years and mean body weight of 155 ± 18.6 kg. The electrocardiogram (ECG) was recorded on a base apex lead before (for 3 days), during, and after verapamil injection (10, 20, 30, 40, 50, and 60 minutes). Verapamil hydrochloride (0.3 mg/kg body weight) was given via catheterizaion as an intravenous bolus over 2 minutes. Heart rate, rhythm, ECG morphology, amplitude, durations, and intervals were measured and taken into consideration and values were compared. Results showed that heart rate was significantly increased at the time of injection from 55 ± 10.7 before injection to 77.61 ± 12.6 beats per minute after injection (P < .05). Duration of P and T waves; P-R interval, and also P-R segment were increased (P < .05). However, duration of QRS complex, P-P and R-R intervals, and S-T segment were significantly decreased after verapamil injection (P < .05). Sinus arrest (2 cases), bradycardia (1 case), and wandering pacemaker (1 case) were recorded before treatment and verapamil injection did not affect these arrhythmias, except in one case in which sinus arrest disappeared. However, after injection of verapamil, four types of arrhythmias (wandering pacemaker WPM], sinus tachycardia, 1^st degree AVB, and 2^nd degree AVB) were recognized. These arrhythmias (with the exception of tachycardia) can be related to the increase of vagal tone activity that might be attributed to the negative effect of verapamil on SA and atrioventricular block AV] nodes.