His bundle lead placement: Is His bundle captured?

A 59-year-old female underwent a dual-chamber pacemaker implantation for intermittent complete heart block. A baseline electrocardiogram showed normal sinus rhythm with first degree AV block and right bundle branch block. A His bundle lead placement was attempted. An intracardiac electrogram from the His bundle lead demonstrated Atrial-His (AH) and His-ventricular (HV) intervals were 186 and 110 milliseconds (msec), respectively. Pacing was performed from the His bundle lead with a decremental pacing output to assess for the His bundle capture threshold (Figure 1). However, there were no significant QRS morphology changes during the pacing. Is the His bundle captured? The tracing evaluation demonstrated the fascinating physiology of activation wavefront in His Purkinje system that could be applied in the use of conducting system pacing technologies. This article is protected by copyright. All rights reserved.