The fixation tines of the Micra™ leadless pacemaker are atraumatic to the tricuspid valve

[Research of tricuspid regurgitation associated with cardiac implantable electronic devices]

Tricuspid regurgitation associated with cardiac implantable electronic devices (CIED) constitutes a significant subset of secondary tricuspid regurgitation, characterized by a multifactorial etiology involving pacing lead-mediated mechanical interference and CIED-related systemic factors. The pathogenesis of CIED-related tricuspid regurgitation encompasses direct mechanical trauma or functional disruption of the tricuspid valve apparatus by pacing leads, pacing mode-induced hemodynamic alterations, and clinical risk factors such as permanent atrial fibrillation, apical pacing, and high right ventricular pacing burden. The natural progression and clinical outcomes of CIED-related tricuspid regurgitation parallel those of tricuspid regurgitation stemming from other etiologies. Advanced imaging modalities, including echocardiography, cardiac computed tomography, and cardiac magnetic resonance imaging, enable precise diagnosis and longitudinal assessment of CIED-related tricuspid regurgitation. Management strategies emphasize multidisciplinary collaboration as well as integration of preventive approaches-such as refined lead implantation techniques and tailored pacing modalities-with therapeutic interventions ranging from pharmacotherapy to surgical valve repair or replacement. This article reviews the current understanding of CIED-related tricuspid regurgitation to provide a reference for clinical practice and research.

Surgical Repair After Leadless Pacemaker-Induced Avulsion of Tricuspid Valve

The use of the leadless pacemaker system (Micra; Medtronic) has grown in popularity with a lower risk of postimplantation complications associated with traditional pacemakers. We describe the case of a 78-year-old woman who presented with torrential tricuspid regurgitation due to avulsion of the anterior papillary muscle and entire chordal apparatus of the tricuspid valve after Micra pacemaker placement at an outside hospital. After she was deemed ineligible for transcatheter approaches, she underwent a minimally invasive tricuspid valve operation. Although her planned operation was valve replacement, she underwent a successful repair with postoperative echocardiography demonstrating no residual torrential tricuspid regurgitation.

Tricuspid valve disease and cardiac implantable electronic devices

The role of cardiac implantable electronic device (CIED)-related tricuspid regurgitation (TR) is increasingly recognized as an independent clinical entity. Hence, interventional TR treatment options continuously evolve, surgical risk assessment and peri-operative care improve the management of CIED-related TR, and the role of lead extraction is of high interest. Furthermore, novel surgical and interventional tricuspid valve treatment options are increasingly applied to patients suffering from TR associated with or related to CIEDs. This multidisciplinary review article developed with electrophysiologists, interventional cardiologists, imaging specialists, and cardiac surgeons aims to give an overview of the mechanisms of disease, diagnostics, and proposes treatment algorithms of patients suffering from TR associated with CIED lead(s) or leadless pacemakers.

The angle of the tines before the pull and hold test predicts engagement of the tines in Micra leadless pacemaker implantation

Background

Micra leadless pacemaker is secured to the myocardium by engagement of at least 2/4 tines confirmed with pull and hold test. However, the pull and hold test is sometimes difficult to assess. This study was performed to evaluate whether the angle of the tines before the pull and hold test predicts engagement of the tines in Micra leadless pacemaker implantation.

Methods

We retrospectively enrolled 93 consecutive patients (52.7% male, age 82.4 ± 9.4 years), who received Micra implantation from September 2017 to June 2020 at our institution. After deployment and before the pull and hold test, the angle of the visible tines to the body of the pacemaker was measured using the RAO view of the fluoroscopy image. The engagement of the tines was then confirmed with the pull and hold test.

Results

A total of 326 tines were analyzed. The angle of the engaged tines was significantly lower than the non-engaged tines (9.2 degrees [4.0-14.0] vs. 16.6 degrees [14.2-18.8], p < .0001). All tines with angles <10 degrees were engaged. In higher angles, engagement could not be predicted.

Conclusion

A low angle of the tines before the pull and hold test can predict engagement of the tines in Micra leadless pacemaker implantation. The tines which are already open after deployment may be presumed that they are engaged.

Evolution of tricuspid valve regurgitation after implantation of a leadless pacemaker - a single center experience, systematic review and meta-analysis

Introduction

Conventional transvenous pacemaker leads may interfere with the tricuspid valve leaflets, tendinous chords, and papillary muscles, resulting in significant tricuspid valve regurgitation (TR). Leadless pacemakers (LLPMs) theoretically cause less mechanical interference with the tricuspid valve apparatus. However, data on TR after LLPM implantation are sparse and conflicting. Our goal was to investigate the prevalence of significant TR before and after LLPM implantation.

Methods

Patients who received a leadless LLPM (Micra™ TPS, Medtronic) between May 2016 and May 2021 at our center were included in this observational study if they had at least a pre‐ and postinterventional echocardiogram (TTE). The evolution of TR severity was assessed. Following a systematic literature review on TR evolution after implantation of a LLPM, data were pooled in a random‐effects meta‐analysis.

Results

We included 69 patients (median age 78 years [interquartile range (IQR) 72–84 years], 26% women). Follow‐up duration between baseline and follow‐up TTE was 11.4 months (IQR 3.5–20.1 months). At follow‐up, overall TR severity was not different compared to baseline (p = .49). Six patients (9%) had new significant TR during follow‐up after LLPM implantation, whereas TR severity improved in seven patients (10%). In the systematic review, we identified seven additional articles that investigated the prevalence of significant TR after LLPM implantation. The meta‐analysis based on 297 patients failed to show a difference in significant TR before and after LLPM implantation (risk ratio 1.22, 95% confidence interval 0.97–1.53, p = .11).

Conclusion

To date, there is no substantial evidence for a significant change in TR after implantation of a LLPM.

Leadless pacemaker implantation under direct visualization during valve surgery

OBJECTIVE

The leadless cardiac pacemaker is typically implanted percutaneously and has been widely used for patients who have already undergone valve surgery. We sought to determine the feasibility and safety of implanting the leadless pacemaker under direct visualization during valve surgery.

METHODS

We performed a retrospective analysis of consecutive adult patients (n = 15) who underwent implantation of a leadless pacemaker under direct visualization at the time of valve surgery. Indications for single-chamber pacing were sick sinus syndrome with pauses (53.3%), atrial fibrillation with slow ventricular rates (13.3%) or complete heart block (6.6%), and elevated risk for postoperative heart block (26.6%). Leadless pacemaker performance and pacing percentage were assessed.

RESULTS

Patients' age was 67.5 ± 17 years, 6 patients (40%) were male, and 14 patients (93%) had atrial fibrillation. Isolated tricuspid valve replacement was performed in 5 patients (33.3%), and the remainder underwent multivalve surgery that included concomitant tricuspid valve repair/replacement. In 93% of the patients (n = 14), the immediate post-cardiopulmonary bypass pacing thresholds were normal (≤2.0 V at 0.24 ms) and normalized in the remaining patient by the next morning. The impedance/sensing values were normal and stable through follow-up (151 ± 119 days) in all patients. Reliable leadless pacemaker performance allowed for deferral of temporary epicardial wires in 11 patients (73%). There were no procedural complications or device malfunction.

CONCLUSIONS

Leadless cardiac pacemaker implantation during valve surgery is feasible and safe. This hybrid approach to pacing may simplify the perioperative management of patients undergoing valve surgery who have an indication for single-chamber pacing.

Injectable Sensors Based on Passive Rectification of Volume-Conducted Currents

Sensing implants that can be deployed by catheterization or by injection are preferable over implants requiring invasive surgery. However, present powering methods for active implants and present interrogation methods for passive implants require bulky parts within the implants that hinder the development of such minimally invasive devices. In this article, we propose a novel approach that potentially enables the development of passive sensing systems overcoming the limitations of previous implantable sensing systems in terms of miniaturization. In this approach implants are shaped as thread-like devices suitable for implantation by injection. Their basic structure consists of a thin elongated body with two electrodes at opposite ends and a simple and small circuit made up of a diode, a capacitor and a resistor. The interrogation method to obtain measurements from the implants consists in applying innocuous bursts of high frequency (≥1 MHz) alternating current that reach the implants by volume conduction and in capturing and processing the voltage signals that the implants produce after the bursts. As proof-of-concept, and for illustrating how to put in practice this novel approach, here we describe the development and characterization of a system for measuring the conductivity of tissues surrounding the implant. We also describe the implementation and the in vitro validation of a 0.95 mm-thick, flexible injectable implant made of off-the-shelf components. For conductivities ranging from about 0.2 to 0.8 S/m, when compared to a commercial conductivity meter, the accuracy of the implemented system was about ±10%.