Correlation between the Width and Number of QRS Complexes with the Pathologic Anatomy of the Cardiac Conduction System in Canine Cases of Third-degree Atrioventricular Block

Abstract

This study examines the relationship between the damaged area of the atrioventricular (AV) conduction system, and both the QRS width and ventricular rate in the electrocardiography of 31 subjects. The subjects were dogs diagnosed with severe anatomical lesions in the AV conduction system by postmortem histopathological examination and were selected from 36 dogs with third-degree AV block. The narrow QRS complex group consisted of four cases, and the wide QRS complex group consisted of 27 cases. Among the 31 cases, 26 cases (84%) were in accordance with the QRS width and lower automatic center, which was assumed to have been derived from the damaged area (supposed lower center). Ventricular rates in 15 cases were less than 40/minute, seven cases were 40 to 60/minute, and nine cases were greater than 60/minute. Thirteen out of 31 cases (42%) were in accordance with the ventricular rate and supposed lower center. In conclusion, it was recognized that QRS duration indicated the locations of the severe AV conduction disturbances more favorably than the ventricular rate.