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Left Bundle Branch Area Pacing: Techniques and Troubleshooting
EP LAB DIGEST. 2023;23(4):18-20.
Hakeem Ayinde, MD, MS, FACC, FHRS,1 and Oluwaseun Adeola, MD, MPH, FACC, FHRS2
1Cardiology Associates of Fredericksburg, Fredericksburg, Virginia; 2Cardiology Clinic of San Antonio, San Antonio, Texas
Right ventricular apical pacing (RVAP) has long been the standard of care for ventricular pacing but is associated with up to a 20% risk of pacing-induced cardiomyopathy.1 The emergence of physiologic pacing in the form of His bundle pacing (HBP) and left bundle branch area pacing (LBBAP) has mitigated this risk. HBP is associated with a higher risk of lead dislodgement, higher capture threshold, and reduced battery longevity since the His bundle region is a relatively nonmuscular area of the heart. In contrast, LBBAP involves lead implantation deep in the interventricular septum, ensuring capture of the LBB and adjacent septal myocardium at a relatively low output while maintaining excellent lead durability.
We review pace mapping and anatomical-based implantation techniques for LBBAP and discuss practical steps of troubleshooting during lead implantation.
Case Presentation
A 51-year-old male with history of prior coronary artery bypass grafting and bicuspid aortic valve replacement with severe aortic stenosis underwent elective percutaneous valve replacement with a 26 mm Sapien 3 Ultra transcatheter heart valve (Edwards). Left ventricular ejection fraction was normal. Baseline electrocardiogram (ECG) showed normal sinus rhythm and normal intervals (Figure 1). Postoperatively, he developed new symptomatic sinus node dysfunction, prolonged PR interval, LBB block (LBBB), and QRS duration of 160 milliseconds (Figure 2). After shared decision-making, the decision was made to implant a dual-chamber pacemaker with LBBAP. During the procedure, the atrial lead was initially placed in the RV for backup pacing. A C304-His sheath (Medtronic) was advanced over the wire into the mid RV. A 3830 SelectSecure lead (Medtronic) was then advanced through the sheath. Using the aortic valve and atrioventricular (AV) junction as a landmark, the fixation spot was chosen in 30º right anterior oblique (RAO) fluoroscopic view, about 1.5 cm distal to the AV junction. The sheath was pulled back to this spot and counter clocked on the septum at a 2 o’clock angle. The lead was screwed in place while watching for advancement of the tip on fluoroscopy. Impedance and injury current were checked after 5 turns. The lead was turned further until an impedance drop of 50-100 ohms was recorded. Left ventricular activation time (LVAT) was consistently 69 milliseconds at all outputs. The atrial lead was then pulled back and placed in the right atrial appendage. At the end, programming at nominal AV delays (150 milliseconds sensed, 180 milliseconds paced) caused fusion between paced and conducted QRS (Figure 3A). Shortening AV delay to 100 milliseconds sensed and 130 milliseconds paced returned a completely paced QRS complex (Figures 3B and 3C).
Implantation Technique
1. Ensure 12-lead ECG is placed in the correct position and display all 12 leads on recording system.
2. Advance a C304-His sheath over the wire into the RV mid cavity.
3. Connect and display RV pacing cables on recording system.
4. Take an image of the heart in 30º RAO view. The ideal implant region is along an imaginary line one-third of the way from the aortic valve to the apex of the RV (Figure 4), usually about 1.5 cm distal to the plane of the tricuspid annulus. The coronary sinus (CS) fat pad, valvular calcification, or valvular prostheses can help identify the location of the aortic valve and tricuspid valve annulus.
5. Advance the sheath to this area and perform unipolar pacing (black alligator clip on tip electrode and red clip connected to patient’s skin).
6. Ideal locations may have the follow features: (a) “W” morphology in V1; (b) aVR and aVL discordance (negative QRS in aVR, positive in aVL); (c) Lead II with more positive R wave than lead III (d) Presence of R wave progression on precordial leads (V1-6 are neither all positive nor all negative).
7. The lead is screwed into the septum in 30º left anterior oblique (LAO) view. The sheath is counter clocked on the septum with the tip pointing at about 2 o’clock in LAO view. The black alligator clip is disconnected from the lead. The lead is then screwed into the septum by clocking between the thumb and forefinger close to the sheath, so that the torque is transmitted efficiently to the tip.
8. After 4-5 turns, check injury current, impedance, and QRS morphology. If LB capture is not achieved, 2-3 additional turns may be performed to advance lead deeper in septum. Consistent LVAT <80 milliseconds at varying outputs suggests good LB capture. LVAT is measured as time between stimulation artifact to peak of V6. LB potential is sometimes recorded (Figure 5). This is not essential for LB capture.
9. As the lead gets deeper in the septum, the impedance increases. A 50-100 ohm unipolar impedance drop suggests that the tip electrode has engaged the LV endocardium. Further turns here will likely cause the lead to cross into the LV cavity.
10. Advance the lead through the sheath to provide some slack prior to splitting the sheath.
Additional tips on troubleshooting during implantation are provided in the Table.
Differentiating LV Septal Pacing vs Nonselective LBB Pacing or Selective LBB Pacing
Fast activation of the LV lateral wall with an LV activation time <80 milliseconds suggests LBB capture. To increase specificity, we recommend checking the V6-V1 interpeak time (Figure 6).2 If this is short (<33 milliseconds), then it is LV septal capture. If >33 milliseconds, there is LBB capture. If >50 milliseconds, then it is highly likely there is selective LB capture.2
When to Select LBBAP
The following criteria is used to select patients for LBBAP:
- Anticipated RV pacing >40%
- Advanced AV nodal disease including marked first degree AV block, Mobitz I/II AV block
- QRS >150 milliseconds (RBBB, IVCD, or LBBB)
- Alternative to CS lead for cardiac resynchronization therapy (CRT), including cases where the CS lead has unsatisfactory threshold or phrenic stimulation
LBBAP is ideal in most cases with anticipated RV pacing >40%, including complete heart block and high-grade AV block. Patients with advanced His-Purkinje disease and bundle branch block with QRS >150 milliseconds may often have a narrower QRS duration with LBBAP due to recruitment of Purkinje tissue distal to level of block or source-sink phenomenon.3 LBBAP also offers a viable alternative to the CS lead for CRT, since CS lead placement may be limited by CS vein anatomy, phrenic nerve stimulation, and high capture threshold.
Conclusion
In contrast to conventional RV apical pacing, LBBAP provides physiologic pacing by engaging the conduction system. Implantation can be achieved safely in most patients and generally circumvents the issues related to high pacing thresholds and lead dislodgments with His bundle and CS pacing.
Disclosures: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. They have no conflicts of interest to report regarding the content herein.
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References
1. Khurshid S, Epstein AE, Verdino RJ, et al. Incidence and predictors of right ventricular pacing-induced cardiomyopathy. Heart Rhythm. 2014;11(9):1619-1625. doi:10.1016/j.hrthm.2014.05.040
2. Jastrzębski M, Burri H, Kiełbasa G, et al. The V6-V1 interpeak interval: a novel criterion for the diagnosis of left bundle branch capture. Europace. 2022;24(1):40-47. doi:10.1093/europace/euab164
3. Mirolo A, Chaumont C, Auquier N, et al. Left bundle branch area pacing in patients with baseline narrow, left, or right bundle branch block QRS patterns: insights into electrocardiographic and echocardiographic features. Europace. 2022;euac223. doi:10.1093/europace/euac223
