Implant, performance, and retrieval of an atrial leadless pacemaker in sheep

BACKGROUND

Medtronic is developing an atrial Micra Transcatheter Pacing System (Medtronic, Minneapolis, Minnesota) and associated retrieval system.

OBJECTIVE

The purpose of this study was to evaluate chronic atrial Micra retrieval, reimplantation, and chronic pacing performance.

METHODS

Sheep were implanted in 2 groups: group 1 (n = 6) for 6 months, a second device implanted, and first retrieved and studied for an additional 6 months; group 2 (n = 6) for 6 months, devices were retrieved, and a second device implanted and observed acutely. Both groups underwent histopathological evaluation. Pacing capture thresholds (PCTs), p wave amplitude, and pacing impedances were measured chronically. Device retrieval times were recorded, and intracardiac echocardiography was used.

RESULTS

At 24 weeks, PCTs for group 1 were low and stable for both the first device (0.55 ± 0.14 V) and the second device (0.57 ± 0.09 V), in which the average retrieval time was 17:35 minutes. For group 2, the average retrieval time was 6:12 minutes, chronic PCTs in the first device were 0.53 ± 0.11 V, and acute PCTs for the second device were 0.71 ± 0.19 V. Pathological findings were within an expected range of tissue responses for similar Micra acute and chronic implants and device retrievals. p waves and impedances were stable and within an expected range for implant site and electrode design. Complications included 1 early dislodgment and 1 death attributed to a prototype retrieval tool.

CONCLUSION

In an animal model, an atrial Micra can be easily implanted with excellent chronic pacing performance and is easily retrievable at 6 months. A second device can successfully be implanted with low, chronic stable thresholds. A developed prototype retrieval tool was easy to use and, with modifications, complication free.

Security millimetre wave body scanner safe for patients with leadless pacemakers or subcutaneous implantable cardioverter-defibrillators

PURPOSE

This study was designed to evaluate the electromagnetic interference (EMI) effects and safety of the new security screening millimetre wave body scanners (MWBSs) for patients with rare cardiac implantable electronic devices (CIEDs).

METHODS

We identified 73 patients with either entirely subcutaneous implantable cardioverter-defibrillators (S-ICD) or leadless pacemakers (LPM) attending routine device follow-up. CIED programming was optimised for the detection of EMI occurrence, and high-voltage therapy was disabled. Patients then underwent millimetre wave body scans under continuous ECG monitoring. Scanning was performed at the recommended distance as well as in close proximity to the scanner emulating accidental exposure. CIED function was observed for EMI effects.

RESULTS

There were no episodes of inhibition of pacing in the leadless pacemaker subgroup, no oversensing in the S-ICD subgroup and no spontaneous device reprogramming in any group. There was no change in pacing or sensing thresholds, and S-ICD vector eligibility remained unchanged after scanning with the MWBS. No CIEDs were identified by the MWBS during the study.

CONCLUSION

No EMI events were detected during the use of MWBSs by patients with either S-ICDs or LPMs. This data should be reassuring for patients suggesting that they can undergo security body scans without worries or disclosure of their CIED status.

Successful implantation of leadless pacemakers in children: a case series

Background

A leadless pacemaker is a new concept in which a miniaturized pacing device is self-contained within the heart. Recently published data show that leadless pacemakers are associated with a decreased risk of major complications when compared with transvenous cardiac pacemakers. This seems to be of particular importance in children and young adults in whom various complications may occur during their lifetime.

Case summary

Herein, we report the successful implantation of Micra™ Transcatheter Pacing System in two children: 12-year-old boy and 13-year-old girl, along with a long-term follow-up. The children had indications for pacemaker implantation, however, with an expected low percentage of pacing due to paroxysmal nature of the third-degree atrioventricular block. The implantation procedures were performed in general anaesthesia. There were no complications. During the 2-year follow-up, there were no adverse events and the electrical parameters of the device remained stable. Pacing percentage was below 0.1%.

Discussion

Transvenous cardiac pacemakers improve quality of life and reduce mortality but may be associated with various short- and long-term complications, mainly related to the presence of transvenous leads and the pulse generator. Compared with adult patients, the implantation of conventional pacemakers in children is still a challenge, not only because of their smaller size but also due to continuing growth, as well as a higher rate of lead and device-related complications. We demonstrate that the implantation of leadless pacemakers in children is feasible and could be worth considering in certain clinical scenarios, especially when ventricular pacing is required rarely.

First transcatheter leadless pacemaker implantation in a pediatric patient with a genetic disease

A pediatric patient suffering from Marden-Walker syndrome, a rare genetic disease, was referred to the authors' hospital for syncope due to bradycardia. Since this disease is associated with severe joint contractures, a transcatheter leadless pacing system (TPS) was chosen. Despite the small body size and complex anatomy, TPS implantation was feasible, demonstrating that it is a safe alternative in difficult venous access compared to a conventional pacemaker with increased risk of lead complications in these patients.

Comparison of the safety and efficacy of Nanostim and Micra transcatheter leadless pacemaker (LP) extractions: a multicenter experience

PURPOSE

Leadless pacemaker (LP) extraction is a relatively new field with limited operator experience. We sought to report a comparison of retrieval process for Nanostim vs Micra transcatheter LPs.

METHODS

The list of retrievals for the Micra transcatheter pacemaker system (TPS) was obtained from Medtronic whereas Nanostim data was obtained from centers that participated in the Leadless II study. Details of retrieval such as indication, days post implantation, complications, and post procedure device management were obtained from the manufacturer database for each site, and any missing details were obtained from individual operators. Extractions performed on the same day were labeled as "Early" and thereafter were labeled as "Late."

RESULTS

A total of 113 retrievals were attempted (73 in Nanostim and 40 in Micra TPS). The most common reasons for retrieval were battery advisory and inadequate pacing threshold (n = 16) for Nanostim and Micra, respectively. Success rate in Nanostim group was around 90% (66/73) compared with 100% in Micra group (p = 0.049). Late retrieval occurred in 50% of Micra TPS cases (20/40) compared with 100% of Nanostim LP cases. Median time to extraction was 46 days for Micra TPS and 256 days for Nanostim LP (p < 0.001). Rate of serious adverse events with Nanostim extraction was 3% (n = 2/73).

CONCLUSION

Overall, LP extraction is feasible and safe to perform irrespective of the duration and type of the device.

Performance of the Micra cardiac pacemaker in nonagenarians

INTRODUCTION AND OBJECTIVES

The Micra transcatheter pacing system has shown high effectiveness and a lower complication rate than conventional transvenous pacemakers. However, the benefit of the device is unknown in the very old population (≥ 90 years). The aim of this study was to evaluate the safety and effectiveness of Micra in patients ≥ 90 years.

METHODS

We present a prospective observational study with consecutive patients aged >70 years who underwent implantation of a Micra pacemaker system. Patients were divided into 2 groups: ≥ 90 and<90 years.

RESULTS

The Micra system was implanted in 129 patients, of whom 41 were aged ≥ 90 years and 88<90 years. The device was successfully implanted in 40 (97.6%) patients ≥ 90 years and in 87 (98.9%) patients<90 years (P=.58). An adequate position was achieved with need for ≤ 2 repositions in 97.5% and 91.9% of patients, respectively (P=.32). Procedure time (26.1 ±11.6 vs 30.3 ±14.2minutes; P=.11) and fluoroscopy time (6.4 ±4.7 vs 7.2 ±4.9minutes; P=0.41) were similar in the 2 groups. There were 3 major complications (2.3%), all in the group aged<90 years: 1 cardiac perforation, 1 femoral hematoma, and 1 femoral pseudoaneurysm. Thirteen patients aged ≥ 90 years (31.7%) and 16 patients aged <90 years (18.2%) died during a mean follow-up of 230±233 days and 394±285 days, respectively. There were no device-related deaths. No infection, dislocation or migration of Micra were observed. The electrical performance was optimal at follow-up.

CONCLUSIONS

The Micra leadless pacing system seems to be safe and effective in patients older than 90 years. It may be considered a reasonable alternative to conventional transvenous pacing in this population.

Percutaneous extraction of a leadless Micra pacemaker after dislocation: a case report

Background 

Leadless pacemaker implantation rates are increasing worldwide. Until now leadless pacemaker dislocation and extraction has been rarely reported.

Case summary 

An 83-year-old patient with cardiac amyloidosis, chronic atrial fibrillation, and complete heart block was implanted with a leadless pacemaker (Micra, Medtronic). On the day after implantation, the device showed an exit block and on cardiac echocardiography and cardiac computer tomography, a device dislocation could be detected. During the day, the device moved at least three times between the tricuspid valve and the right ventricular apex. Each time causing non-sustained ventricular tachycardia. At the next day device extraction was scheduled. After 189 minutes of procedure time, it was possible to retrieve the device with the help of two steerable introducers (Agilis) and two snare catheters.

Discussion 

Implantable transcatheter leadless pacemakers can be implanted safely most of the time. However, in rare cases device dislocations may occur. Device extraction is possible, but is described as challenging in most published cases

Safety and Efficacy Outcomes of Combined Leadless Pacemaker and Atrioventricular Nodal Ablation for Atrial Fibrillation Using a Single Femoral Puncture Approach

BACKGROUND

Atrioventricular nodal (AVN) ablation with permanent pacemaker (PPM) insertion is indicated for rate control in patients with atrial fibrillation (AF) who remain unresponsive to rate or rhythm control strategies. The leadless PPM (Micra Transcatheter Pacing System [TPS], Medtronic, Minneapolis, MN, USA) has the advantage of eliminating transvenous lead and pacemaker pocket-related complications. The aim of this case series was to determine the outcomes of patients who had undergone combined Micra TPS and AVN ablation, performed via a single femoral approach.

METHOD

A retrospective review was undertaken on patients who had undergone concurrent procedures, across two major hospitals in Perth, Western Australia. Procedural details were obtained from a cardiac devices database whilst patient demographics and clinical information were determined from medical records.

RESULTS

Fourteen (14) patients underwent concurrent Micra TPS insertion and AVN ablation for symptomatic AF. The average age was 73±9.2 years, and 43% of them were males. There was no acute procedural/device related complication. Over a median follow-up duration of 9 months (36% completing 12-month follow-up), there was no incidence of device complications, in particular device dislodgement, malfunction or infection. One patient had a resuscitated ventricular fibrillation (VF) arrest event with new onset cardiomyopathy during follow-up and required Micra TPS removal. One patient died at 33 days post procedure from a non-cardiac cause. Device performance was excellent with stable sensing and pacing thresholds during the follow-up period.

CONCLUSION

Our study has shown that combined leadless PPM (Micra TPS) implantation and AVN ablation using a single femoral approach is feasible, with good safety and efficacy profile in the short-medium term. Long-term data involving larger cohorts is needed to confirm the findings of this study and determine the clinical usefulness of this combined approach.

The use of a single chamber leadless pacemaker for the treatment of cardioinhibitory vasovagal syncope

Background

The use of pacemakers in the treatment of cardioinhibitory vasovagal syncope is controversial with a mixed message from the limited evidence base. Single chamber leadless pacemakers have been shown to be an effective alternative option to conventional pacemakers.

Objective

This study examines the use of leadless pacemakers in a cardioinhibitory vasovagal population in the United Kingdom.

Methods

Observational data on 32 patients implanted with the Micra Transcatheter Pacemaker System for vasovagal syncope are presented. Data was collected on implant indications, implant procedure and follow up data from 12 centres across the United Kingdom that had elected to use a Micra leadless pacemaker in this patient population.

Results

32 patients aged 37 ± 14 years (range 18 to 64 years) with 62% of the patients being female were recruited to the study. Vasovagal syncope was diagnosed clinically and with the support of Holter monitoring, tilt table testing and implantable loop recorders. The duration of symptoms was 8 ± 8 yrs. with an average frequency of syncope being 4 ± 6 times/year. The Micra pacemaker was successfully implanted in all patients with a major complication rate of 3.1%. Patients were followed up for 404 ± 237 days (range 63–928 days). At follow up 28 (87%) patients were free from symptoms.

Conclusions

This observational study suggests that the use of a single chamber leadless pacemaker in the treatment of cardioinhibitory vasovagal syncope might be a reasonable clinical option.

Leadless pacemaker implant in patients with pre-existing infections: Results from the Micra postapproval registry

Introduction

Leadless pacemakers may provide a safe and attractive pacing option to patients with cardiac implantable electronic device (CIED) infection. We describe the characteristics and outcomes of patients with a recent CIED infection undergoing Micra implant attempt.

Methods and Results

Patients with prior CIED infection and device explant with Micra implant within 30 days, were identified from the Micra post approval registry. Procedure characteristics and outcomes were summarized. A total of 105 patients with prior CIED infection underwent Micra implant attempt ≤30 days from prior system explant (84 [80%] pacemakers and 13 [12%] ICD/CRT‐D). All system components were explanted in 93% of patients and explant occurred a median of 6 days before Micra implant, with 37% occurring on the day of Micra implant. Micra was successfully implanted in 99% patients, mean follow‐up duration was 8.5 ± 7.1 months (range 0‐28.5). The majority of patients (91%) received IV antibiotics preimplant, while 42% of patients received IV antibiotics postprocedure. The median length of hospitalization following Micra implant was 2 days (IQR, 1‐7). During follow‐up, two patients died from sepsis and four patients required system upgrade, of which two patients received Micra to provide temporary pacing support. There were no Micra devices explanted due to infection.

Conclusion

Implantation of the Micra transcatheter pacemaker is safe and feasible in patients with a recent CIED infection. No recurrent infections that required Micra device removal were seen. Leadless pacemakers appear to be a safe pacing alternative for patients with CIED infection who undergo extraction.

Subclinical cardiac perforation caused by a Micra™ leadless pacemaker

A subclinical cardiac perforation by a device cup of the Micra™ transcatheter pacing system was suspected in a 78-year-old woman. During the procedure, the device cup was placed on the septum. The contrast media was injected before device deployment and remained outside of the myocardium. Later, a cardiac computed tomography scan visualized a protruded diverticular structure on the right ventricle. The contrast material remained in a pouch within the pericardium. To ensure the device is oriented away from the border between the right ventricular septum and the free wall, right anterior oblique view should be carefully reviewed before deployment.

Visualization and appearance of artifacts of leadless pacemaker systems in cardiac MRI : An experimental ex vivo study

Background

Leadless pacemaker systems are an important upcoming device in clinical rhythmology. Currently two different products are available with the Micra system (Medtronic) being the most used in the clinical setting to date. The possibility to perform magnetic resonance imaging (MRI) is an important feature of modern pacemaker devices. Even though the Micra system is suitable for MRI, little is yet known about its impact on artifacts within the images.

Objective

The aim of our ex vivo study was to perform cardiac MRI to quantify the artifacts and to evaluate if artifacts limit or inhibit the assessment of the surrounding myocardium.

Methods

After ex vivo implantation of the leadless pacemaker (LP) in a porcine model, hearts were filled with saline solution and fixed on wooden sticks on a plastic container. The model was examined at 1.5 T and at 3 T using conventional sequences and T2 mapping sequences. In addition, conventional X‑rays and computed tomography (CT) scans were performed.

Results

Correct implantation of the LP could be performed in all hearts. In almost all MRI sequences the right ventricle and the septal region surrounding the (LP) were altered by an artifact and therefore would sustain limited assessment; however, the rest of the myocardium remained free of artifacts and evaluable for common radiologic diagnoses. A characteristic shamrock-shaped artifact was generated which appeared to be even more intense in magnitude and brightness when using 3 T compared to 1.5 T.

Conclusion

The use of the Micra system in cardiac MRI appeared to be feasible. In our opinion, it will still be possible to make important clinical cardiac MRI diagnoses (the detection of major ischemic areas or inflammatory processes) in patients using the Micra system. We suggest the use of 1.5 T as the preferred method in clinical practice.

Acute septic arthritis of the knee: A rare case report of infection with Parvimonas micra after an intra-articular corticosteroid injection for osteoarthritis

Acute bacterial mono-articular septic arthritis affects most commonly the lower extremity joints in adult population and most commonly caused by Staphylococcus aureus. Various risk factors determine susceptibility to infection including host immunity, medical co-morbidity and joint structural abnormality and other organisms may be involved. Parvimonas micra (P. micra) is among the rare organisms that may be associated with atypical septic arthritis and primarily affects the native knee joint. Only 3 case reports in the literature have reported on pyogenic pyogenic joint infection caused by this organism. We hereby present our experience with a case of knee septic arthritis caused by P. micra in a patient with knee osteoarthritis following a recent intra-articular injection with corticosteroids. In susceptible patients, Intra-articular corticosteroid injection and crystal induced arthritis may propose a potential risk of contracting infection with P. micra.

Leadless Cardiac Pacemaker Implantation After Lead Extraction in Patients With Severe Device Infection

BACKGROUND

Conventional pacemaker therapy is limited by short- and long-term complications, most notably device infection. Transcatheter pacing systems (TPS) may be beneficial in this kind of patients as they eliminate the need for a device pocket and leads and thus may reduce the risk of re-infection.

METHODS

We assessed a novel procedure in 6 patients with severe device infection who were pacemaker dependent. After lead extraction a single chamber TPS was implanted into the right ventricle.

RESULTS

Of the 6 patients who underwent lead extraction due to severe device infection at our institution, 3 were diagnosed with a pocket infection only, whereas the other 3 showed symptoms of both pocket and lead infection. Successful lead extraction and TPS implantation was accomplished in all patients. Four patients were bridged with a temporary pacemaker between 2 hours and 2 days after lead extraction, whereas 2 patients had the TPS implanted during the same procedure just before traditional pacemaker system removal. All patients stayed free of infection during the follow-up period of 12 weeks. An additional positron emission tomography scan was performed in each patient and indicated no signs of an infection around the TPS.

CONCLUSION

Transcather pacemaker implantation was safe and feasible in 6 patients and did not result in re-infection even if implanted before removal of the infected pacemaker system within the same procedure. Therefore, implantation of a TPS may be an option for patients with severe device infection, especially in those with blocked venous access or who are pacemaker dependent.