His Bundle Pacing: New Approach Using Stylet-Supported Pacing Leads

Five-year performance data is now available for HBP.¹ Studies to date have consistently used the SelectSecure 3830 lead (Medtronic) in the His position, with standard pacing leads used for RV apical pacing (RVP).^1-6 The 3830 lead is lumenless and not supported by a stylet, and therefore, an outer guide sheath is necessary to position the lead tip. Capture thresholds were significantly higher compared to RVP (1.35±0.9 V vs 0.62±0.5 V @ 0.5 ms; P<0.01), with differences attributed to the lead-tissue interface.^1,5

The C315HIS sheath (Medtronic) is preferred for delivery of the 3830 lead, with a fixed primary curve designed to direct the sheath tip anteriorly toward the tricuspid valve annulus, and a second fixed curve directed orthogonally toward the septum.⁶ With the C315 in position, the 3830 lead may be advanced 1-2 cm beyond the sheath. His mapping and preliminary pacing are performed from the exposed helix. When favorable results are obtained, active fixation is achieved with 5-8 revolutions of the lead body. In settings where the C315 is unable to reach the tricuspid annulus (such as right atrial enlargement), the SelectSite C304 deflectable sheath (Medtronic) with single plane curvature is recommended.⁵ Success with the C304 sheath demonstrates that a secondary curve providing septal angulation is not strictly necessary to deliver a pacing lead to the His position.

OUR APPROACH

Stylets are known to facilitate tissue contact during implant for the majority of pacing leads, with most featuring an extendable/retractable fixation mechanism. To incorporate the advantages of a stylet support with HBP, we are now performing HBP using a standard extendable/retractable pacing lead supported by a luminal stylet. Here we share our early experience. In the cases shown (Figures 1-5), we use a Solia S ProMRI pacing lead (BIOTRONIK), supported by a stylet that is shaped with primary and secondary curves as needed, with or without the additional support of a Selectra R-45 outer guide sheath (BIOTRONIK). The primary curve of the Selectra R-45 sheath is similar to that of the C315HIS sheath, and a secondary curve can be added with customized shaping of the stylet to direct the lead to the His position. In this case, the 60 cm lead is required to accommodate the length of the guide sheath. Mapping is performed in a bipolar configuration prior to extension of the fixation screw, with the screw extended when a satisfactory His recording and paced QRS morphology are obtained. The outer sheath is then slit and removed, followed by withdrawal of the stylet. Gentle curving of the stylet avoids placing torque on the lead tip as the stylet is withdrawn, helping to avoid inadvertent dislodgment during sheath removal.

Operators at the Indiana University School of Medicine and Geisinger Heart Institute routinely perform HBP for all cases requiring a ventricular pacing lead. Similarly, we have used HBP for all implants since performing our first case in June 2016.⁷ We were the first to perform HBP with closed loop stimulation (CLS), combining a BIOTRONIK pacemaker with the SelectSecure 3830 lead.⁸ With >100 such cases, we now have the largest single-center experience combining HBP with CLS. We have found no discernable limitation with CLS derived from the His position, and now seek to offer our patients the benefits of HBP with a stylet-supported lead and extendable/retractable fixation mechanism. Included below are three representative cases demonstrating this approach.

EXAMPLE CASES

In the first case, a 68-year-old male underwent pacemaker implantation for profound chronotropic incompetence (Figures 1 and 2). A Solia S pacing lead was advanced through a Selectra R-45 sheath positioned in the right atrium, and directed toward the tricuspid annulus. A primary curve was placed on the tip of the stylet to septally direct the lead. A secondary curve was not required. Mapping was performed in a bipolar configuration, recording a prominent His potential with the local electrogram demonstrating an A-H-V sequence (Figure 1B). At implant, the R wave measured 4.1 mV with impedance 425Ω. Implant threshold was 1.2V @ 0.4 msec with ECG demonstrating non-selective His bundle capture (see figure legends for details). At one-month follow-up, the R wave measured 5.8 mV with threshold 0.8V @ 0.4 msec.

The second case involved an 86-year-old female with severe tricuspid regurgitation, right bundle branch block (Figure 3A1), and permanent atrial fibrillation for whom atrioventricular junction (AVJ) ablation was planned (Figure 3). A stylet with both primary and secondary curves was needed to direct the lead to the His position. A right bundle potential was recorded (Figure 3A2), and bundle branch block was corrected by pacing (Figure 3A3). Implant threshold was 1.5V @ 0.4 msec, with the R wave measuring 3.1 mV and impedance 522Ω (Figure 3B). The lead stylet was particularly helpful in stabilizing the lead tip in the setting of severe tricuspid regurgitation and right atrial enlargement. At one-month follow-up, the R wave measured 4.8 mV with threshold 1.0V @ 0.4 msec (see figure legend for details).

The third case demonstrated lead placement without an outer guide sheath, using only stylet support (Figures 4 and 5). This was attempted when use of an outer guide sheath was found to impede lead positioning, with optimal placement readily achieved with a stylet-only approach. A Solia S pacing lead was advanced to the right atrium. A stiff stylet with customized shape (Figure 4A) was then advanced through the lead, directing the tip to the His position (Figure 4B). A His potential was recorded in bipolar mode (Figure 5A) prior to extension of the fixation screw. Because the shaped stylet did not feature a sharp secondary curve, it could be withdrawn without introducing torque at the lead tip. Selective His capture was demonstrated (Figure 5B), with final lead position shown at implant (Figure 4C) and post procedure (Figure 5C).

CONCLUSION

We demonstrate HBP with an extendable/retractable active fixation lead supported by a luminal stylet. With this technique, an outer sheath is not necessary and may be detrimental. Stylet-based HBP provides improved lead stability and tissue contact, allowing for a customized implant approach in the setting of anatomic variation. Notably, stylet-support leads from other manufacturers should yield similar results. To our knowledge, these cases are the first reports of HBP using a pacing lead supported by a luminal stylet, with and without an outer guide sheath. Long-term lead performance characteristics will follow.

Disclosure: Dr. Kneller has no conflicts of interest to report regarding the content herein. Outside the submitted work, he reports honoraria for professional services from Medtronic and BIOTRONIK, and non-financial support from BIOTRONIK for research work.   

References

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