Transconduit implantation of an active fixation leadless pacemaker in a patient with intra-atrial Fontan palliation

Key Teaching Points.

• •Leadless pacemaker (LP) implantation is a less invasive alternative to surgical epicardial lead placement in Fontan patients with complicated anatomy who are deemed to be poor surgical candidates. This decision regarding LP implantation should be individualized on a case-by-case basis.
• •Choice of pacemaker (passive fixation [Micra] vs active fixation [Aveir]) and the site of implantation should be individualized based on anatomic factors, thrombus/device embolization risk at various locations, technical feasibility, and the likelihood of future device retrieval.
• •At present, surgical epicardial pacing is the most established method of permanent pacing in Fontan patients. Long-term data on device performance/safety and thromboembolism risk are required to elucidate the utility of LP implantation in this patient population.

Introduction

Long-term survivors of the Fontan procedure are predisposed to progressive conduction abnormalities, often necessitating pacemaker implantation. Epicardial lead placement remains the standard approach but is associated with significant procedural morbidity, particularly in patients with Fontan-associated liver disease and renal dysfunction, where surgical interventions carry elevated perioperative risk. Although leadless pacemakers (LPs) are a promising alternative, their use in Fontan physiology, particularly via a transconduit approach into the systemic ventricle, remains underreported. Here, we describe the first successful transconduit implantation of an Aveir VR LP into the systemic ventricle of a 61-year-old patient with an intra-atrial Fontan and significant comorbidities, highlighting technical considerations and potential benefits in high-risk cohorts.

Case report

A 61-year-old man with Klippel-Feil syndrome and associated complex congenital heart disease (CHD), including isolated dextrocardia, double-outlet right ventricle (RV), pulmonary stenosis, and hypoplastic RV, had undergone a Glenn anastomosis followed by an intra-atrial lateral tunnel Fontan procedure at age 27 years. At age 42 years, he developed complete atrioventricular (AV) block in the setting of permanent atrial fibrillation and underwent epicardial ventricular pacemaker implantation. He underwent generator changes at ages 46, 51, 54, and 57 years. The patient presented with a progressive increase in ventricular pacing threshold. Preoperative evaluation demonstrated Fontan-associated cirrhosis with a Child-Pugh score of 7 (class B) and stage 3b chronic kidney disease, with an estimated glomerular filtration rate of 33 mL/min per body surface area and creatinine of 2.19 mg/dL. Multidisciplinary adult CHD team assessment concluded that the patient’s surgical risk of epicardial lead revision was prohibitive. After shared decision making with the patient after extensive discussion in a multidisciplinary approach, transvenous LP implantation was contemplated.

The procedure was performed under conscious sedation, and bilateral femoral venous accesses were obtained under ultrasound guidance. Intracardiac echocardiogram (ICE), 8F AcuNav (Biosense Webster) was used in conjunction with fluoroscopy for anatomic guidance. A bidirectional Agilis NxT steerable sheath (Abbott, Chicago, IL) was used to support working wires for transconduit puncture. At the beginning, all equipment was positioned in the venous conduit in preparation for the puncture. Subsequently, this was successfully performed using a combination of a BRK needle with adjunctive electrocautery application and a radiofrequency (RF)-enabled PowerWire (Baylis). After the working wires were able to cross over the transconduit access, serial dilation was performed using over-the-wire angioplasty balloons to create an adequate tract for the passage of a 24F Aveir delivery sheath (Figure 1). This sheath was later advanced across the conduit into the systemic-exposed portion. Subsequently, Aveir VR LP was positioned into the apical septum of the hypoplastic RV, ensuring placement distal to the systemic AV valve apparatus (Figure 2, Figure 3, Figure 4, Supplemental Video 1).

Figure 1.

Intracardiac Echocardiography image of transbaffle balloon dilation.

Figure 2.

Deployment of the Aveir device.

Figure 3.

Device seated in the apical septum. AV = atrioventricular.

Figure 4.

A and B: Posteroanterior and lateral views of the chest showing the position of the Aveir device.

Device interrogation demonstrated a pacing threshold of 0.5 V at 0.4 ms pulse width and an impedance of 680 Ω, confirming optimal device performance. After implantation, the transconduit access was closed using a 10 mm Amplatzer septal occluder device (Figure 5). Anticoagulation with warfarin was resumed with a target international normalized ratio of 2–3.

Figure 5.

Amplatzer device closure of baffle fenestration.

The postoperative course was complicated by acute-on-chronic renal failure requiring hemodialysis. At the 3-month follow-up, device parameters were stable with a threshold of 0.75 V at 0.4 ms pulse width and impedance of 580Ω; no clinical thromboembolic events were noted.

Discussion

We report the first successful transconduit implantation of an Aveir VR LP into the systemic ventricle of a 61-year-old patient with an intra-atrial Fontan, with accompanying chronic liver and kidney disease.

Patients with Fontan physiology pose unique challenges for cardiac rhythm management owing to a lack of direct percutaneous venous access to the ventricle, increased venous pressure, and elevated thromboembolic risk. Although traditional epicardial pacing is the default option, it carries increased perioperative risk, especially in patients with end-organ dysfunction, such as Fontan-associated liver disease and chronic kidney disease. Lead failure and threshold elevation are common long-term complications of epicardial pacing, prompting interest in minimally invasive alternatives.

Percutaneous implantation of LPs, such as the Micra (Medtronic) and Aveir VR (Abbott), offers an appealing alternative as they eliminate the need for surgery and lead- and pocket-related complications such as infection. However, their use in patients with Fontan circulation remains technically challenging owing to complex venous anatomy and the lack of direct venous access to the ventricle. We describe the successful implantation of the Aveir VR (Abbott) pacemaker through transconduit access to the systemic ventricle. The best approach and the site of conduit puncture to place the LP at the targeted site of implantation would be based on the cardiac anatomy. In patients with lateral tunnel and extracardiac Fontan conduits, a similar approach to our case would be preferred, with additional efforts to identify a site of puncture that is closest to native atrial tissue (using computed tomography/magnetic resonance imaging and ICE) and away from calcifications. An inferior approach is generally preferred, given that in many Fontan patients, including our case, the superior vena cava is discontinuous from the right atrium owing to Glenn anastomosis, making a superior approach unfeasible. In the few cases where the superior vena cava and right atrium are continuous, a superior approach may be considered if femoral access proves challenging. In addition, the currently available tools are better suited for an inferior approach.

If a preexisting fenestration is present, we preferentially use it, often with balloon dilation, to facilitate passage of larger sheaths. If this does not provide easy access to the AV valve and ventricle, a new puncture may be needed. Transconduit puncture is in general technically challenging. Often times, both mechanical and RF-based approaches are used or at least considered. Advancements in baffle/conduit puncture including utilization of ICE, RF-enabled wires for conduit puncture, and noncompliant balloons for transconduit dilation have made this the favored approach compared with retrograde aortic access to the systemic ventricle, which carries a high risk of vascular and valve injury. The use of multimodal imaging, including ICE and fluoroscopy, was essential for navigating the anatomy, confirming the transconduit trajectory, and verifying sheath and device position relative to the AV valve to prevent valve impingement.

The choice of LP and the site of implantation in the ventricle are important considerations that should be individualized to each patient. Although implantation of the passive fixation tined Micra LP is previously described in Fontan patients,^1,2 we describe the first Fontan patient with implantation of the Aveir (Abbott) LP system, which has a screw-in active fixation mechanism. The Aveir device was chosen owing to the possibility of more stable fixation to the myocardium using the screw-in mechanism when the LP is implanted in the dominant morphologic left ventricle (LV), which typically has less prominent trabeculations compared with the hypoplastic morphologic RV. In addition, the Aveir device allows more reliable explantation and retrieval of the device in the future using a dedicated extraction tool if indicated. The ability to perform sequential AV pacing using the Aveir DR leadless dual chamber pacing system may provide superior hemodynamics in other Fontan patients.

When considering the site of device implantation in the ventricle, considerations included the relative size of the RV and LV cavities to support lead placement, noninterference with AV valve function, risk of embolization of thrombus or the device at different locations, and ease of access through the transbaffle puncture. Preimplantation cross-sectional imaging is critical for planning the most advantageous position. Uniquely in our patient, preprocedure computed tomography imaging showed the presence of an RV cavity large enough to implant a device with a partially formed ventricular septum separating it from the dominant LV (Figure 6). We felt that LP placement in the hypoplastic RV may carry a lower risk of thrombus embolization than the dominant LV, which directed blood directly toward the aorta. Hence, the RV was selectively targeted for LP placement.

Figure 6.

RV cavity large enough to implant a device with a partially formed ventricular septum separating it from the dominant LV. LV = left ventricle; RV = right ventricle.

Of note, the patient experienced significant renal dysfunction requiring intermittent hemodialysis after the procedure. This was likely multifactorial in nature, with preexisting chronic kidney disease, use of iodinated contrast, intraprocedural renal hypoperfusion, transconduit shunting, and systemic embolization into the renal vasculature being potential contributors.

Although the Aveir leadless pacing system may offer several advantages in select Fontan patients, long-term outcomes have not been reported in patients with CHD. A recent study by Rahmat et al³ demonstrates the safety and stability of midterm parameters of the AVEIR LP in 3 adults with CHD. Given the risk of thrombosis of the device, lifelong anticoagulation was recommended. Furthermore, unlike an epicardial pacing system, a new LP will need to be implanted once the existing device reaches the end of its battery life, which may involve additional technical complexity, spatial limitations, and consequently procedural risk. Further multicenter studies are needed to evaluate long-term outcomes of LP, including device performance and thromboembolic risks, before it can be considered in a broader Fontan population who are otherwise reasonable surgical candidates.

Conclusion

Transconduit LP implantation in adult CHD with Fontan physiology may be considered as an alternative to epicardial pacing in patients at high surgical risk. With careful imaging guidance and lifelong anticoagulation, it can be safely performed in patients with complex anatomy. Further prospective data are needed to define long-term safety and efficacy.

Disclosures

The authors have no conflicts of interest to disclose.