Author + information
- Received November 30, 2018
- Revision received December 19, 2018
- Accepted December 19, 2018
- Published online April 15, 2019.
- Robert D. Anderson, MBBSa,
- Mukund Prabhu, MD DMb,
- Jonathan M. Kalman, MBBS, PhDa,
- Jitendra K. Vohra, MDa,
- Joseph B. Morton, MBBS, PhDa and
- Irene Stevenson, MBBSa,∗ ()
- aDepartment of Cardiology, Royal Melbourne Hospital, Faculty of Medicine, Dentistry, and Health Science, University of Melbourne, Melbourne, Victoria, Australia
- bDepartment of Cardiology, Royal Melbourne Hospital and Department of Cardiology, Kasturba Medical College, Manipal Academy of Higher Education, Manipal, India
- ↵∗Address for correspondence:
Dr. Irene Stevenson, Department of Cardiology, Royal Melbourne Hospital, 300 Grattan Street, Parkville, Victoria 3050, Australia.
A 46-year-old woman underwent implantation of an elective His-bundle (HB) pacemaker following a protracted history of atrial tachyarrhythmias including paroxysmal atrial fibrillation, atrial tachycardia, and cavotricuspid isthmus-dependent atrial flutter. Despite undergoing prior pulmonary vein isolation and a re-do procedure for reconnection, right atrial flutter isthmus, and crista terminalis ablations, she had recurrent episodes and had become profoundly bradycardic on antiarrhythymic therapy. Physiological pacing with an HB pacemaker (with an atrial lead to facilitate right atrial overdrive pacing) was preferred prior to retrial of medical therapy. Baseline electrocardiogram showed normal intervals (Figure 1A).
The HB was mapped using unipolar recordings from a 69-cm Medtronic 3839 lead with a 1.8-mm exposed helix (Medtronic Inc., Minneapolis, Minnesota) through a His C315 nondeflectable sheath using a pace-sense analyzer to record intracardiac electrograms. Pre-deployment, His-ventricular interval was prolonged measuring 61 ms (Figure 1A) and unipolar pacing at this site produced nonselective HB pacing (high output, arrows [Figure 1B]) and right bundle pacing (low output, arrowheads [Figure 1B]). Deployment of the lead (8 clockwise rotations of transmitted torque) produced a large current of injury on the HB lead and marked prolongation of the PR interval to 305 ms and splitting of the His into 2 low-voltage components (H1 and H2) (Figure 1C). Initially the H1-H2 and H2-ventricular intervals were constant (98 ms and 55 ms); however, there were periods where the H1-H2 demonstrated a 4:3 Wenckebach pattern with a constant atrial-H1 interval, progressive lengthening of the H1-H2 interval until a dropped H1 (absent H2 and the QRS complex, star [Figure 1D]) supportive of an intra-Hisian position and lead tip-induced injury (Figure 1E). Pacing at this site produced selective pacing just above the threshold (Figure 1F). Device check the following day showed no further atrioventricular block and the His lead threshold had reduced to 0.5 V at 1 ms.
Prior studies demonstrate heart block in approximately 1% of HB pacemakers due to focal damage of the HB and surrounding edema induced by electrode fixation (1,2). Intra-Hisian injury, manifesting as His splitting and an HB escape rhythm is rarely reported in about 0.3% of cases, which can often be predicted by a large HB injury current on the unipolar lead electrogram. In all cases, initial HB capture thresholds were acutely high and rapidly improved. Pacing is typically able to overcome the His-ventricular block, and in all cases conduction had completely recovered at 2-week follow-up (1).
Dr. Anderson has been supported by postgraduate scholarships cofunded by the National Health and Medical Research Council (NHMRC) and Royal Australasian College of Physicians NHMRC Woodcock Scholarships. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
All authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the JACC: Clinical Electrophysiology author instructions page.
- Received November 30, 2018.
- Revision received December 19, 2018.
- Accepted December 19, 2018.
- Vijayaraman P.
- Vijayaraman P.,
- Dandamudi G.,
- Ellenbogen K.A.