Tine-Based Leadless Pacemaker: Strategies for Safe Implantation in Unconventional Clinical Scenarios

Leadless pacemaker implementation at the right atrial appendage apex: An initial preclinical assessment

OBJECTIVE

This study evaluates the feasibility and efficacy of implanting a leadless pacemaker at the right atrial appendage (RAA) in a preclinical minipig model, aiming to address the limitations of atrial pacing with current leadless devices like the Medtronic Micra, which is typically used for right ventricular implantation.

METHODS

Four minipigs, each with a median body weight of 45.8 ± 10.0 kg, underwent placement of the Micra transcatheter pacing system (TPS) via the right femoral vein into the RAA apex. The pacing performance was assessed over 1-week (short-term) and 3-month (long-term) periods.

OUTCOMES

The initial findings indicated successful implantation, with satisfactory intrinsic R-wave amplitudes and pacing threshold. In the following period, the sensitivity, threshold, and impedance were stable with time. Notably, upon explanation at 3 months, a deep myocardial penetration by the device was observed, necessitating a redesign for safe long-term use in a growing subject's heart.

CONCLUSION

While initial results suggest that RAA apex placement of the Micra TPS is promising for potential inclusion in a dual-chamber pacing system, the issue of myocardial penetration highlights the need for device redesign to ensure safety and effectiveness in long-term applications.

Perioperative Considerations for Modern Leadless Pacemakers

Since their initial approval by the Food and Drug Administration in 2016, leadless pacemakers have become increasingly prevalent. This growth has been driven by an improved adverse effect profile when compared to traditional pacemakers, including lower rates of infection, as well as eliminated risk of pocket hematoma and lead complications. More recently, technology enabling leadless synchronized atrioventricular pacing in patients with atrioventricular block has vastly expanded the indications for these devices. Anesthesiologists will increasingly be relied upon to safely care for patients with leadless pacemakers undergoing non-electrophysiology procedures and surgery. This article provides an overview of the technology, evidence base, current indications, and unique perioperative considerations for leadless pacemakers.

Strategies for Safe Implantation and Effective Performance of Single-Chamber and Dual-Chamber Leadless Pacemakers

Leadless pacemakers (LPMs) have emerged as an alternative to conventional transvenous pacemakers to eliminate the complications associated with leads and subcutaneous pockets. However, LPMs still present with complications, such as cardiac perforation, dislodgment, vascular complications, infection, and tricuspid valve regurgitation. Furthermore, the efficacy of the leadless VDD LPMs is influenced by the unachievable 100% atrioventricular synchrony. In this article, we review the available data on the strategy selection, including appropriate patient selection, procedure techniques, device design, and post-implant programming, to minimize the complication rate and maximize the efficacy, and we summarize the clinical settings in which a choice must be made between VVI LPMs, VDD LPMs, or conventional transvenous pacemakers. In addition, we provide an outlook for the technology for the realization of true dual-chamber leadless and battery-less pacemakers.

Comparison of cardiac function before and after Micra implantation using pool scintigraphy and myocardial work: A case report

Leadless pacemakers, specifically Micra (Medtronic), have recently become a preferred alternative to transvenous pacemakers for use in bradyarrhythmia. Problems with conventional transvenous pacemakers include wound infection, lead disconnection, and tricuspid valve dysfunction. While Micra has the advantage of not being associated with the aforementioned complications, there have been reports of cardiac injury during Micra implantation, which have raised safety concerns. Many reports have evaluated Micra safety, but its effect on cardiac function remains unclear. In an 85-year-old man with bradycardic atrial fibrillation, a heart rate of approximately 35 bpm, and symptoms of dizziness, we analyzed ventricular workload, ejection fraction of the left and right ventricles, and inter/intraventricular synchrony using cardiac blood pool scintigraphy and myocardial work. Micra was successfully implanted into the right ventricular septum via the left femoral vein. A follow-up, 2 days later, showed no major complications associated with Micra pacing threshold and impedance. At this time, there was no apparent worsening of heart failure. Micra implantation for bradycardic atrial fibrillation has the potential to improve left ventricular work efficiency without the loss of ventricular synchrony.

The Large Right Heart Is Associated with the Prolongation of the Procedure Time of Leadless Pacemaker Implantation

Background and objectives: Leadless pacemakers are less invasive but are as effective as conventional pacemakers and are increasingly implanted in elderly patients. However, the implantation procedure is sometimes challenging in patients with abnormal anatomy, particularly those with an enlarged right heart. We aimed to determine the right heart parameters that were associated with longer procedure times for leadless pacemaker implantation. Materials and Methods: Among 19 consecutive patients in whom Micra leadless pacemakers (Micra TPS, Medtronic, Minneapolis, MN) were implanted, the diameter and area of both the right atrium and right ventricle were measured by transthoracic echocardiography before the procedure. The right heart parameters that were associated with a procedure time > 60 min were investigated. Results: In the 19 patients (median 81 years old, 10 male) who underwent implantation of the Micra system, 6 (32%) required a procedure time > 60 min. Among the baseline right heart echocardiographic parameters, right atrial diameter and area were significantly associated with a procedure time > 60 min (odds ratio 11.3, 95% confidence interval 1.09-1.17, p = 0.042; and odds ratio 1.57, 95% confidence interval 1.05-2.34, p = 0.029, respectively) at a cutoff of 4.0 cm and 17.0 cm2, respectively. Conclusions: Patients with an enlarged right atrium may not be good candidates for leadless pacemakers given the longer procedure time, and conventional pacemakers should perhaps be recommended as an alternative.