Leadless Pacemaker Implantation and AV Nodal Ablation: Initial Experience

The Micra Transcatheter Pacing System (TPS; Medtronic) has been established as a great alternative to transvenous single-chamber pacemakers, with overall less complication rates.¹ Simultaneous AV node ablation and permanent pacemaker implantation is a good option for patients with atrial fibrillation in whom rate control is difficult to achieve with medical therapy only.² Concomitant use has not been widely explored with the use of the leadless pacemaker. In this article, we describe our first pace-and-ablate experience using the Micra TPS. 

 

An 80-year-old female, with a past medical history of mechanical mitral valve replacement and permanent atrial fibrillation, presented with a symptomatic and very rapid ventricular rate. She did not tolerate rate control medical therapy due to drops in her blood pressure with attempted titration of beta blockers and calcium channel blockers. Hence, we discussed the option of performing an AV node ablation along with permanent pacemaker implantation. We thought she would be a good candidate for the new Micra TPS, as she would only need single-chamber pacing. All advantages and disadvantages of transvenous versus leadless pacemaker options were discussed with her, and she elected to proceed with this option. 

 

After local infiltration with 1% lidocaine, right femoral venous access was obtained (with vascular ultrasound guidance) through which an 8 French (Fr) sheath was placed in the right femoral vein. Another 8 Fr left femoral venous access was obtained (to later be used for AV node ablation and backup pacing, which might be required during the procedure). A right femoral venogram was performed through the right venous sheath to check the anatomy and possible tortuosity of the venous system (Figure 1). The right femoral venous access was slowly upsized (with step up dilation) to a 21 Fr dilator, all advanced over an Amplatz Super Stiff Guidewire (Boston Scientific), with its tip placed in the superior vena cava. A 27 Fr Micra delivery sheath was then advanced over the Amplatz Super Stiff Guidewire under fluoroscopic guidance to the mid right atrium, and 2500 units of intravenous heparin were administered. Next, the delivery catheter was introduced into the delivery sheath and advanced under fluoroscopic guidance. It was then deflected and directed to the mid to high septum of the right ventricle with special attention to avoid the RV free wall and apex. Contrast injections in multiple views (RAO 30 and LAO 40) were performed to ensure adequate contact with the RV septal wall. The device was then deployed under fluoroscopic guidance into a mid septal position (after ensuring a good forward pressure achieving a gooseneck deformation in the Micra delivery catheter). The first deployment attempt was successful. The electrical pacing system was tested using the analyzer, which showed excellent sensing and pacing parameters (pacing threshold of 0.25V@0.24ms, R waves of 6-7 mV, and an impedance of 600-700 ohms). A tug test was performed and recorded on fluoroscopy, and resulted in splaying of 3 of 4 tines, which confirmed adequate fixation (Figure 2). The tether was then cut and slowly removed, the device was released, and the delivery catheter was removed. Pacing and sensing parameters continued to be stable after releasing the device. 

Backup pacing was reprogrammed to VVI 40. Subsequently, a deflectable 4 mm tip radiofrequency ablation catheter was advanced under fluoroscopic guidance via the left femoral access site into the right atrium. In the RAO projection, the catheter was advanced carefully to the anterior tricuspid annulus and the His bundle electrogram was recorded, and radiofrequency was delivered just posterior and inferior to that location (Figure 3). Several lesions were delivered in that location and resulted in complete AV block. The patient was observed for a total of 30 minutes without evidence of return of spontaneous AV conduction. The catheter was removed under fluoroscopic guidance.  

 

A figure-of-8 suture was then applied at the right femoral venous access site and the 27 Fr sheath was pulled, achieving excellent hemostasis. Manual compression was held for 20 minutes and adequate hemostasis was confirmed. The patient made a complete and uneventful recovery with no immediate post-procedure complications. A chest x-ray performed on post-operative day 1 demonstrated stable position of the device (Figure 4). Pacing and sensing parameters continued to be excellent and stable on the next day and at two-week post-op, with persistent complete AV block. The procedure did not result in groin hematoma or bleeding from the access site despite being on dual full anticoagulation (warfarin and IV heparin for bridging). 

Since its introduction, the Micra TPS has been proven to be a safe and efficacious alternative to a transvenous system while providing low and stable pacing thresholds.³ Performance of the Micra TPS in a real-world setting demonstrates a high implant success and low rate of major complications through 30 days post implant.⁴ The leadless pacemaker has a great advantage of preventing the complications inherent to transvenous pacemakers,⁵ including pocket complications (hematoma and/or infection) and lead complications (lead fractures, dislodgements, and/or tricuspid valve insufficiency).

 

On the other hand, AV nodal ablation together with pacemaker implantation is an established last resort therapy option for patients with atrial fibrillation in whom rate control with medical therapies is difficult to achieve.¹ However, its use with the leadless pacemaker has not been well studied. Ho et al reported the first simultaneous leadless pacemaker implantation and AV node ablation using a single vascular access site, and demonstrated that it is feasible and safe.⁶ They described the potential risks of performing an ablation immediately after implantation, including mechanical dislodgement, electrical damage to the device, electromagnetic interference, and/or conductive heating of tissue near the device. A single access site was used in that case, where a multiple sheath assembly (8 Fr inside a 14 Fr sheath) was inserted into the introducer sheath to allow hemostatic seal during ablation. In a larger single-site study, Sande et al studied 10 patients who successfully underwent immediate AV ablation with leadless pacemaker implantation.⁷ All patients remained alive at mean follow-up of 9 ± 8 months, without notable events and with stable electrical parameters. 

 

In our case, we elected to insert the ablation catheter into a separate venous access site (left femoral vein). The separate venous access site allows the use of backup pacing that might be needed during the process of implanting the Micra TPS. The location of the His bundle was mapped using a decapolar diagnostic catheter prior to inserting the Micra delivery sheath (Figure 5). This allowed for more precise manipulation of the ablation catheter to minimize the chance of mechanical dislodgement of the pacemaker. The pacemaker was implanted in mid to apical septal position to prevent mechanical, electrical, and thermal interaction between the ablation catheter and pacemaker. 

 

In summary, we re-demonstrated that simultaneous use of AV nodal ablation and Micra TPS implantation could be safely and effectively done. Further larger-scale studies with long-term follow-ups are required to prove the efficacy and safety of that concomitant use.