The Thai Journal of Veterinary Medicine


In safety pharmacological and toxicological studies, all new chemical entities should be investigated for the possibility of slow atrioventricular (AV) conduction especially at the infranodal of AV node. The objective of this study was to compare two locations of His bundle electrogram (HBE) recording, the right side (right atrium) and the left side (non-coronary cusp), of the heart in anesthetized dogs. Diltiazem was used to evaluate these two locations. The dogs (n=6) were anesthetized with morphine and a-chloralose. In order to record HBE, two catheters with multiple electrodes were placed in the right atrium via jugular vein and in the non-coronary cusp via femoral artery. Transthoracic electrocardiogram (ECG) was acquired. ECG parameters (HR, PR, QRS, and QT) and HBE parameters (AH and HV intervals) were measured at baseline and after a single bolus dose of 0.5 mg/kg diltiazem (5, 10, and 15 min). PR interval was significantly prolonged after receiving diltiazem when compared to the baseline (p<0.05). When HBE was recorded from the catheter placed in the non-coronary cusp, the AH interval was prolonged significantly whereas the HV interval did not change. The AH and HV intervals were prolonged when it was recorded from the catheter placed in the right atrium. The His bundle recording from the non-coronary cusp was preferable since the position was fixed and stable, resulting in the prolongation of the AH interval but not HV interval in response to diltiazem.

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