Pervenous Pacing of the Specialized Conducting System in Man

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Abstract
His bundle electrograms were recorded and A-V junction pacing was achieved in 30 patients by a pervenous electrode catheter technic. His bundle pacing was achieved in 26, and A-V node pacing in five patients. Conduction time from atrium to the His bundle (A-H time) and His bundle to ventricular activation (H-V time) were measured. During His bundle pacing, the pacing impulse to ventricular activation time (PI-R) was the same as the H-V time during normal sinus rhythm and remained constant at different pacing rates. With A-V node pacing, the PI-R interval was shorter than the conduction time from atrium to the ventricle (sum of the A-H and the H-V time) but longer than the H-V time, and there was progressive lengthening of PI-R interval, with increase in pacing rates. The QRS complex remained unchanged in all ECG leads with BH and A-V node pacing from that during normal sinus rhythm. During BH pacing, the retrograde Wenckebach phenomenon was demonstrated. Bundle of His pacing was used to establish a His bundle rhythm in a patient with complete heart block localized within the His bundle. BH pacing is of value for validation of His bundle electrograms and differentiation from that of right bundle branch. Clinically, this technic has proved extremely useful in definitive diagnosis of bilateral bundle-branch block in patients with right bundle-branch block and left axis deviation and infarction.