Case Report: A leadless and endovascular pacemaker teamwork

Background

Cardiac Implantable Electronic Device infections increase short- and long-term mortality, along with healthcare costs. Leadless pacemakers (PM) were developed to overcome pocket- and minimize lead-related complications in selected high-risk patients. Recent advancements enable leadless devices to mechanically detect atrial activity, facilitating atrioventricular (AV) synchronous stimulation.

Case summary

A 90-year-old woman, implanted with a dual-chamber pacemaker eight years ago due to sinus node dysfunction, presented with syncope. A diagnosis of complete AV block, in the setting of ventricular lead dysfunction was made. Due to a high risk of infection, the patient was implanted with a leadless PM capable of maintaining AV synchrony in VDD mode (MICRA™ model MC1AVR1). The transvenous PM was programmed to AAI-R mode to drive the atria, which, in turn, triggered the leadless PM to stimulate the ventricles. At six month follow-up, the AV synchrony rate was 85%.

Conclusion

The combination of classic atrial pacing with leadless ventricular stimulation can be used in high-risk patients to reduce the risk of complications, in the setting of ventricular lead dysfunction. In this manner, AV synchrony can be maintained, improving hemodynamic parameters and quality of life. Low sinus rate variability at rest is essential to achieve a high AV synchrony rate in such cases.

Comparison of first- and second-generation leadless pacemakers in patients with sinus rhythm and complete atrioventricular block

INTRODUCTION

The efficacy and safety of leadless cardiac pacemakers (LPMs) as an alternative to conventional transvenous cardiac pacing have been largely reported. The first generation of the MicraTM transcatheter pacing system (VR; Medtronic) was able to provide single-chamber VVI(R) pacing mode only, with a potential risk of pacemaker syndrome in sinus rhythm patients. A second-generation system (AV) now provides atrioventricular synchrony through atrial mechanical (Am) sensing capability (VDD mode).

OBJECTIVE

We sought to compare VR and AV systems in sinus rhythm patients with chronic ventricular pacing (Vp) for complete atrioventricular block.

METHODS

All consecutive patients implanted with an LPM in our department for complete atrioventricular block were retrospectively screened. Patients with atrial fibrillation, sinus dysfunction, or Vp burden <20% at 1 month postimplantation were excluded. Patients were systematically followed with a visit at 1 month, and then at least once a year.

RESULTS

A total of 93 patients-45 VR (2015-2020) and 48 AV (2020-2021)-were included. VR and AV patients had similar baseline characteristics, except for VR patients being older (80 ± 8 vs. 77 ± 9 years, p = 0.049). The mean Vp burden was 77% in the VR and 82% in the AV group (p = 0.38). In AV patients, the median AV synchronous beats rate was 78%, with 65% having a >66% rate. An E/A ratio <1.2 as measured on echocardiography was the only independent predictor of accurate atrial mechanical tracking (p = 0.01). One-year survival rate was similar in both groups. Five patients in the VR and 0 in the AV group eventually developed pacemaker syndrome within 1 year post-implantation (p = 0.02).

CONCLUSION

In sinus rhythm patients with chronic Vp for complete atrioventricular block implanted with an LPM, the atrial mechanical sensing algorithm allowed significant atrioventricular synchrony in most patients and was associated with no occurrence of-otherwise rare-pacemaker syndrome.

Atrioventricular synchronous leadless pacing: Micra AV

Since the arrival of leadless pacemakers (LPs), they have become a cornerstone in remedial treatment of bradycardia and atrioventricular (AV) conduction disorders, as an alternative to transvenous pacemakers. Even though clinical trials and case reports show indisputable benefits of LP therapy, they also bring some doubts. Together with the positive results of the MARVEL trials, AV synchronization has become widely available in LPs, presenting a significant development in leadless technology. This review presents the Micra AV (MAV), describes major clinical trials, and introduces the basics of AV synchronicity obtained with the MAV and its unique programming options.

Dual-Chamber Leadless Pacing: Atrioventricular Synchrony in Preclinical Models of Normal or Blocked Atrioventricular Conduction

BACKGROUND

Dual-chamber leadless pacemakers (LP) require robust communication between distinct right atrial (RA) and right ventricular (RV) LPs to achieve atrioventricular (AV) synchrony.

OBJECTIVE

This preclinical study evaluated a novel, continuous implant-to-implant (i2i™) communication methodology for maintaining AV-synchronous, dual-chamber DDD(R) pacing by the 2 LPs.

METHODS

RA and RV LPs were implanted and paired in 7 ovine subjects, 4 of 7 with induced complete heart block. AV synchrony (% AV intervals <300 ms) and i2i communication success (% successful i2i transmissions between LPs) were evaluated acutely and chronically. During acute testing, 12-lead ECG and LP diagnostic data were collected from 5-minute recordings, in 4 postures and 2 rhythms (AP-VP and AS-VP or AP-VS and AS-VS) per subject. Chronic i2i performance was evaluated through 23 weeks post-implant (final i2i evaluation period: week 16-23).

RESULTS

Acute AV synchrony and i2i communication success across multiple postures and rhythms were 100.0% [100.0-100.0] (median [interquartile range]) and 99.9% [99.9-99.9], respectively. AV synchrony and i2i success rates did not differ across postures (P=0.59, P=0.11) or rhythms (P=1.00, P=0.82). During the final i2i evaluation period, the overall i2i success was 98.9% [98.1-99.0].

CONCLUSION

Successful AV-synchronous, dual-chamber DDD(R) leadless pacing using a novel, continuous, wireless communication modality was demonstrated across variations in posture and rhythm in a preclinical model.

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.

Leadless Pacemaker Implantation in a Patient With Diminutive Subclavian Veins

Conventional pacemakers have a longstanding history of preventing morbidity and mortality in patients with bradyarrhythmia and conduction disorders. While decades of advancements have improved pacemaker technology and implantation technique, insertion of transvenous leads and formation of a pectoral pocket can lead to complications, including pocket hematoma, pneumothorax, or infection. Leadless pacemakers were introduced in 2012 to address these complications; however, early leadless systems only provided single-chamber ventricular pacing. In 2020, an accelerometer-based atrial sensing feature was developed to allow for atrioventricular (AV) synchrony with these devices. Early evidence suggests that patients with sinus rhythm and AV block can benefit from single-chamber leadless pacing systems with an AV synchrony algorithm. As availability of these devices continues to broaden, identification of appropriate recipients has become increasingly relevant.

Micra-AV leadless pacemaker and atrioventricular (dys)synchrony: A stepwise process

Leadless pacemakers have become a major breakthrough in the management of bradyarrhythmia as an attractive alternative to the standard transvenous pacemakers, but safety and long-term outcomes of the new Micra-AV, which is capable guarantee atrioventricular (AV) synchrony, have been poorly described. Hence, we describe how we managed a 57-year-old patient who developed pacemaker syndrome due to significant Micra-AV dyssynchrony. This case emphasizes how leadless pacemaker AV synchrony could be overestimated, thereby requiring a stepwise process leading to adequate device reprogramming. Holter-ECG monitoring and exercise test resulted to be valuable tools for an early detection of inadequate AV synchrony, integrating and completing device reports.

Symptomatic sinus tachycardia with perpetuating slow pathway: successful treatment with radiofrequency ablation

We report a case of sinus tachycardia with perpetuating slow pathway (SP) conduction in a 42-year-old woman who developed severe symptoms as a result of atrioventricular (AV) desynchronization. The restoration of an AV synchrony, achieved with selective radiofrequency ablation of the SP, eliminated the symptomatic arrhythmia and may represent a reasonable therapeutic option despite the fact that the patient has no AV-node reentrant tachycardia. This case demonstrates the importance of AV timing.