State of the art of leadless pacing

Improving outcomes in single chamber leadless pacemakers: strategies for minimizing vascular complications

BACKGROUND

Leadless pacemaker therapy is associated with a significant reduction in lead-related complication rate compared to conventional transvenous single chamber pacemaker therapy. However, a significant complication rate of 1.2% was observed in vascular access due to the use of large delivery femoral sheath (27Fr). The aim of this study was to evaluate the effectiveness of real-time ultrasound guidance and Z suture technique in reducing total and major vascular complications in leadless pacemaker therapy.

METHOD

In this study, we performed a retrospective and prospective analysis of all adverse events associated with leadless pacemaker (Micra) implantation by two operators at a single tertiary center from December 2016 to December 2018. To mitigate the risk of vascular complications, all patients underwent real-time ultrasound-guided venipuncture for vascular access, as well as the application of a Z-suture technique for hemostasis at the end of the procedure. Data were collected on implant indications, implant procedure details, complications, and follow-up information.

RESULTS

In this study, 45 patients with an age range of 24 to 94 years (mean 76 ± 14 years) were recruited, with 21 (46.6%) being female. The pacing indications for the patients included atrial fibrillation (24, 53.3%), vascular (7, 15.5%), infection (9, 20%), cognitive/frailty (3, 6.6%), and occupational (2, 4.4%). The implant procedures were performed under general anesthesia in 6 (13.3%) of the cases, and under local anesthesia and sedation in 39 (86.6%) of the cases. A single deployment was achieved in 43 (95.5%) of the patients, while 2 deployments were required in 2 (4.4%) of the patients. Notably, no vascular or major complications were reported in our cohort of patients.

CONCLUSIONS

The results of this observational study indicate that incorporating real-time ultrasound guidance during venipuncture and the use of a Z-suture technique significantly reduce the occurrence of both total and major vascular complications associated with the implantation of leadless pacemaker. However, more robust and larger studies are required in order to confirm these results and implications for clinical practice.

Comparison of in-hospital outcomes and complications of leadless pacemaker and traditional transvenous pacemaker implantation

AIMS

Since their introduction in 1958, traditional cardiac pacemakers have undergone considerable upgrades over the years, but they continue to have a complication rate of ∼3.8%-12.4%. There are no randomized controlled trials comparing outcomes of leadless pacemakers (LPM) with single-chamber transvenous pacemakers (TV-VVI). The aim is to assess the differences in the procedural complications and in-hospital outcomes between LPM and TV-VVI implants.

METHODS AND RESULTS

We queried the national inpatient database from 2016 to 2019 to include adult patients undergoing LPM and TV-VVI. Admissions for leadless and single-lead transvenous pacemakers were identified by their appropriate ICD-10 codes. Complications were identified using ICD-10 codes that mostly represent initial encounter. The difference in outcomes was assessed using multivariable logistic regression and 1:1 propensity score matching between the two cohorts. Thirty-five thousand four hundred thirty expanded samples of admissions were retrieved of which 27 650 (78%) underwent TV-VVI with a mean age 81.3 ± 9.4 years and 7780 (22%) underwent LPM with a mean age of 77.1 ± 12.1 years. The LPM group had a higher likelihood of in-hospital mortality [adjusted odds ratio (aOR): 1.63, 95% CI (1.29-2.05), P < 0.001], vascular complications [aOR: 7.54, 95% CI (3.21-17.68), P < 0.001], venous thromboembolism [aOR: 3.67, 95% CI (2.68-5.02), P < 0.001], cardiac complications [aOR: 1.79, 95% CI (1.59-2.03), P < 0.001], device thrombus formation [aOR: 5.03, 95% CI (2.55-9.92), P < 0.001], and need for a blood transfusion [aOR: 1.54, 95% CI (1.14-2.07), P < 0.005]. The TV-VVI group had higher likelihood of in-hospital pulmonary complications [aOR:0.68, 95% CI (0.54-0.87), P < 0.002] and had a need for device revisions [aOR:0.42, 95% CI (0.23-0.76), P < 0.004].

CONCLUSION

There is a higher likelihood of all-cause in-hospital mortality and complications following LPM implantation in comparison to TV-VVI. This could be related to higher co-morbidities in the LPM group. Clinical trials aimed to accurately compare these two groups should be undertaken.

Clinical outcomes and predictors of complications in patients undergoing leadless pacemaker implantation

BACKGROUND

Leadless pacemakers have emerged as a viable alternative for traditional transvenous pacemakers to reduce the risk of device-related complications.

OBJECTIVE

The purpose of this study was to examine the real-world clinical outcomes and complications associated with the implantation of leadless pacemaker devices.

METHODS

Using the National Readmission Database (NRD), we examined patient demographics, and in-hospital and 30-day procedural outcomes after leadless pacemaker implantation from 2016-2018. Our cohort comprised adults (≥18 years) with an ICD-10 procedural code for leadless pacemaker implantation.

RESULTS

Our cohort included a total of 7821 patients who underwent leadless pacemaker implantation. Overall immediate procedure-related complications, as defined broadly in this study, occurred in 7.5% of patients. Pericardial effusion without the need for pericardiocentesis occurred in 1.9% of patients, with pericardiocentesis performed in 1.0%. Vascular complications occurred in 2.3% of patients; 0.33% required repair, and device dislodgment occurred in 0.51%. The most significant predictor for procedural complications was end-stage renal disease (odds ratio [OR] 1.65; 95% confidence interval [CI] 1.17-2.32; P = .004), congestive heart failure (OR 1.28; 95% CI 1.01-1.62; P = .04), and coagulopathy (OR 1.77; 95% CI 1.34-2.34; P <.001). All-cause readmission occurred in 17.9% of patients within 30 days from device implant, with 1.36% of readmissions being procedure related. At 30 days postimplant and after discharge, 0.25% of patients needed a new pacemaker, and 0.18% had pericardial complications.

CONCLUSION

In our large real-life cohort, we found the rate of serious complications after leadless pacemaker implantation to be relatively low and comparable to prior studies in a high-risk population with multiple comorbid conditions.

Factors influencing the use of leadless or transvenous pacemakers: results of the European Heart Rhythm Association Prospective Survey

To study the proportion of leadless pacemaker (LL-PM) implants and the factors influencing the choice of LL-PM vs. transvenous pacemaker (TV-PM) across tertiary centres in Europe with routine availability of the LL-PM. A European Heart Rhythm Association (EHRA) prospective snapshot survey using electronically distributed questionnaire sent to participating centres. Participating tertiary cardiac pacing centres prospectively included consecutive patients implanted between November 2018 and January 2019. Questions covered standards of care and policies used for patient management, focusing particularly on the reasons for choosing LL-PM vs. TV-PM. Overall, 21 centres from four countries (France, Netherlands, Spain, and Italy) participated, with eventual data from 798 patients (n = 472, 59% male). With 69 implants, LL-PM represented only 9% of all implants and 36% of the single-chamber pacing group; double-chamber transvenous pacemakers were implanted in 528 patients and biventricular (cardiac resynchronization pacemaker) in 79. The two major reasons reported in favour of LL-PM implantation were an anticipated high risk of infection or low rate of ventricular pacing. Compared to TV-PM, LL-PM patients were more often male (74% vs. 54%, P = 0.009), with greater proportion of valvular heart disease (45% vs. 35%, P = 0.01) and atrial fibrillation (AF; 65% vs. 23%, P < 0.0001), with significantly more comorbidities (≥ one comorbidity, 66% vs. 52%, P = 0.02). This contemporary multicentre European survey shows that LL-PM constitutes a small proportion of all PM implants. Patients implanted with LL-PM were more likely to have AF and a high anticipated risk of infection.

Quantification of artifacts during cardiac magnetic resonance in patients with leadless Micra pacemakers

INTRODUCTION

When cardiac magnetic resonance (MR) is performed after previous leadless transcatheter pacemaker implantation, an image distortion has to be expected in the heart region and evaluation of myocardial tissue can be affected. In this clinical prospective study, we aim to assess the extent and impact of this artifact on individual ventricular segments and compare it to conventional pacing devices.

METHODS

Total of 20 patients with leadless pacemaker placed in the right ventricle underwent cardiac MR imaging in a 1.5 Tesla scanner. A multiplanar segmentation was used to demarcate the left and right ventricular myocardium as well as the pacemaker-caused image artifact in systolic and diastolic time frames. Artifact size and its relative influence on myocardial segments were quantitatively assessed and expressed in AHA-17 model.

RESULTS

Implanted leadless pacemaker caused an image artifact with a volume of 48 ± 5 ml. Most distorted were the apical septal (53 ± 23%), apical inferior (30 ± 18%), and midventricular inferoseptal (30 ± 20%) segments. The artifact intersection with basal and lateral segments was none or negligible (up to 2%). The portion of left ventricular (LV) myocardium affected by the artifact was significantly higher in systole (8 ± 4%) compared to diastole (10 ± 3%; p < .001).

CONCLUSION

Implantation of leadless pacemaker represents no obstacle for cardiac MR imaging but causes an image artifact located mostly in septal, inferoseptal, and anteroseptal segments of apical and midventricular LV myocardium. With the exception of the apex, diastolic timing reduces the image distortion of all segments and improves global ventricular assessment.

In Vivo Intravascular Pacing Using a Wireless Microscale Stimulator

Millions of patients worldwide are implanted with permanent pacemakers for the treatment of cardiac arrhythmias and conduction disorders. The increased use of these devices has established a growing clinical need to mitigate associated complications. Pacemaker leads, in particular, present the primary risks in most implants. While wireless power transfer holds great promise in eliminating implantable device leads, anatomical constraints limit efficient wireless transmission over the necessary operational range. We thereby developed a transmitter-centered control system for wireless power transfer with sufficient power for continuous cardiac pacing. Device safety was validated using a computational model of the system within an MRI-based anatomical model. The pacer was then fabricated to meet the acute constraints of the anterior cardiac vein (ACV) to enable intravascular deployment while maintaining power efficiency. Our computational model revealed the wireless system to operate at > 50 times below the tissue energy absorption safety criteria. We further demonstrated the capacity for ex vivo pacing of pig hearts at 60 beats per minute (BPM) and in vivo pacing at 120 BPM following pacer deployment in the ACV. This work thus established the capacity for wireless intravascular pacing with the potential to eliminate complications associated with current lead-based deep tissue implants.

Alternate method for endocardial pacemaker lead implantation: A hybrid mini-thoracotomy approach

Although the conventional methods for endo-cardial pacemaker lead implantation via subclavian or cephalic or axillary vein routes is common, but sometimes due to anatomical variations it is not feasible to access these veins Emergence of newer techniques are useful for lead implantation. This case report focuses on a hybrid approach of combined mini-thoracotomy for endocardial pacemaker lead implantation. This fluoroscopy guided minimal thoracotomy approach with endocardial MRI compatible lead placement had the benefits of simple procedural, minimal hospital stay, low early complication rates and economically viable to the patient.

Implantation of the Micra transcatheter pacing system: A single center North India experience

Background

The leadless pacemaking transcatheter system, Micra, is a miniaturized, single-chamber pacemaker system. We report herein our experience with implantation of the Micra TPS system.

Objective

The current study was conducted to evaluate the safety and efficacy of the leadless Micra Transcatheter Pacemaker System (Medtronic).

Research design and methods

This was a prospective single centre nonrandomized study without controls. A transcatheter pacemaker was implanted in patients who had guideline based indications for ventricular pacing. 28 subjects were screened based on the selection criteria. Mica TPS was implanted. Parameters assessed were: duration of procedure (from femoral vein puncture to venous access closure), fluoroscopy time, number of device repositions, periprocedural electrical measurements (sensing, threshold and impedance) and in-hospital, intermediate to long term adverse events related to procedure.

Result and conclusion

s: The device was successfully implanted in 28 subjects. The mean intraoperative sensing value was 9.04 ± 1.5 mV and the impedance was 766.89 ± 213.9 Ω. At discharge from hospital, those values were 13.2 ± 15.83 mV and 855 ± 111.7, respectively. The recommended pacing threshold value as achieved in all subjects was 0.78 V, i.e. ≤ 1 V at 0.24 ms. There was no adverse event or complications reported for any of the subjects. Mean time from hospitalization to discharge was 1.5 days. Implantation of leadless pacemakers is feasible, safe and provides advantages over the conventional system.

A Multi-Dimensional Analysis of a Novel Approach for Wireless Stimulation

The elimination of integrated batteries in biomedical implants holds great promise for improving health outcomes in patients with implantable devices. However, despite extensive research in wireless power transfer, achieving efficient power transfer and effective operational range have remained a hindering challenge within anatomical constraints.

OBJECTIVE

We hereby demonstrate an intravascular wireless and batteryless microscale stimulator, designed for (1) low power dissipation via intermittent transmission and (2) reduced fixation mechanical burden via deployment to the anterior cardiac vein (ACV, ∼3.8 mm in diameter).

METHODS

We introduced a unique coil design circumferentially confined to a 3 mm diameter hollow-cylinder that was driven by a novel transmitter-based control architecture with improved power efficiency.

RESULTS

We examined wireless capacity using heterogenous bovine tissue, demonstrating >5 V stimulation threshold with up to 20 mm transmitter-receiver displacement and 20° of misalignment. Feasibility for human use was validated using Finite Element Method (FEM) simulation of the cardiac cycle, guided by pacer phantom-integrated Magnetic Resonance Images (MRI).

CONCLUSION

This system design thus enabled sufficient wireless power transfer in the face of extensive stimulator miniaturization.

SIGNIFICANCE

Our successful feasibility studies demonstrated the capacity for minimally invasive deployment and low-risk fixation.

Clinical outcomes of leadless pacemaker: a systematic review

INTRODUCTION

Transvenous pacemakers are associated with a significant amount of complications. Leadless pacemakers (LP) are emerging as an alternative to conventional devices. This article provides a systematic review of patient eligibility, safety and clinical outcomes of the LP devices.

EVIDENCE ACQUISITION

A systematic search for articles describing the use of LP was conducted. Out of two databases, 24 articles were included in the qualitative analysis. These articles comprised a total of 4739 patients, with follow-up times of 1-38 months. Further information was obtained from 10 more studies.

EVIDENCE SYNTHESIS

From a population of 4739 patients included in the qualitative analysis, 4670 LP were implanted with success (98.5%). A total of 248 complications were described (5.23%) during the follow-up. The most common were pacing issues such as elevated thresholds, dislodgements or battery failure (68 patients), events at the femoral access site such as hemorrhage, hematoma or pseudoaneurysms (64 patients) and procedure related cardiac injuries such as cardiac perforation, tamponade or pericardial effusion (47 patients). There were 360 deaths during the follow-up and 11 were described as procedure or device related. Four studies presented the strategy of using a combined approach of atrioventricular node ablation (AVNA) and LP implantation.

CONCLUSIONS

Leadless pacemakers seem to have a relatively low complication rate. These devices may be a good option in patients with an indication for single-chamber pacing, in patients with conditions precluding conventional transvenous pacemaker implantations. Studies directly comparing LP and transvenous pacemakers and data on longer follow-up periods are needed.

Wireless Pacing Using an Asynchronous Three-Tiered Inductive Power Transfer System

Despite numerous advancements in pacemaker technology for the treatment of cardiac arrhythmias and conduction disorders, lead-related complications associated with these devices continue to compromise patient safety and survival. In this work, we present a system architecture that has the capacity to deliver power to a wireless, batteryless intravascular pacer. This was made possible through a three-tiered, dual-sub-system, four-coil design, which operates on two different frequencies through intermittent remote-controlled inductive power transfer. System efficiency was enhanced using coil design optimization, and validated using numerical simulations and experimental analysis. Our pacemaker design was concepted to achieve inductive power transfer over a 55 mm range to a microscale pacer with a 3 mm diameter. Thus, the proposed system design enabled long-range wireless power transfer to a small implanted pacer with the capacity for intravascular deployment to the anterior cardiac vein. This proposed stent-like fixation mechanism can bypass the multitude of complications associated with pacemaker wires while wireless power can eliminate the need for repeated procedures for battery replacement.

The Safety and Feasibility of Same-Day Discharge After Implantation of MICRA Transcatheter Leadless Pacemaker System

Background

Data suggests that same day discharge after implantation of trans-venous pacemakers is safe and feasible. We sought to determine whether same day discharge was feasible and safe following implantation of Medtronic MICRA leadless pacemakers.

Methods

We retrospectively identified all patients undergoing MICRA placement at our institution between April 2014 to August 2018 (n=167). Patients were stratified into two groups: those discharged on the same day as their procedure (SD, n=25), and those observed for at least one night in the hospital (HD, n=142). The primary endpoint included a composite of major complications including: access site complications, new pericardial effusion, device dislodgement, and need for device revision up to approximately 45 days of follow up.

Results

SD and HD had similar age (75±13 vs. 75±13 years, p=0.923), prevalence of male sex (49 vs. 44%, p=0.669), and frequency of high-grade heart block as an indication for pacing (38 vs. 32%, p=0.596). There were more Caucasians in the SD group (72 vs. 66%, p=0.038). The rate of the composite endpoint was statistically non-significantly higher in the HD group (3.5% vs. 0.0%, p=1.00). The rates of each individual components comprising the composite endpoint were similar between groups.

Conclusions

Our data suggest that in appropriately selected patients, same day discharge can occur safely following Micra leadless pacemaker implantation.

Complications and associated healthcare costs of transvenous cardiac pacemakers in Germany

Aim: This study evaluated the occurrence and associated costs of pacemaker complications in Germany from 2010 to 2013. Patients & methods: Patients with a de novo or replacement implantation of a single or dual chamber pacemaker between 2010 and 2013 were followed for 12 months post-implant using German health insurance claims data. A case-control analysis was performed using propensity score matching to estimate the costs of complications. Results: Out of 12,922 implanted patients, 12.0% had a complication in the year following the implant. Complications related to lead and pocket were found in 10.2% of all implanted patients; infections occurred in 1.7% patients. Healthcare costs up to 36 months post complication were on average €4627 higher than for pacemaker patients without a complication. Conclusion: Pacemaker complications are common and represent a burden for patients and healthcare systems generating substantial costs. Most of the pacemaker complications involved the pacing lead or pacemaker pocket.

Outcomes of Micra leadless pacemaker implantation with uninterrupted anticoagulation

BACKGROUND

Implantation of the MICRA Leadless pacemaker requires the use of a 27 French introducer, blunt delivery system and device fixation to the myocardium via nitinol tines. While prior studies have proven its safety, it is unclear whether performing this procedure with uninterrupted anticoagulation exposes patients to increased risks. We sought to investigate the feasibility and safety of continuing therapeutic anticoagulation during the periprocedural period.

METHODS

We evaluated all patients undergoing MICRA placement at our institution between April 2014 and August 2018 with complete follow-up data (n = 170). Patients were stratified into two groups: those on active anticoagulation (OAC, n = 26), defined as having an International normalized ratio >2.0 or having continued a direct oral anticoagulant, and those not anticoagulated (Off-OAC, n = 144). We evaluated for a composite outcome of all major complications, including access site complications and pericardial effusion.

RESULTS

OAC and Off-OAC groups had similar mean age (74 ± 13 vs 75 ± 13 years; P = .914). The OAC group had a nonsignificantly lower prevalence of end-stage renal disease (8% vs 17%; P = .375) and aspirin use (27% vs 47%; P = .131). Those in the OAC group were more likely to be on warfarin than those in the Off-OAC group (81% vs 30%; P < .001). The rate of the composite endpoint was similar between the OAC and Off-OAC groups (3.8 % vs 1.4%, respectively; P = .761). Length of stay was similar between groups (1.3 ± 2.6 vs 2.3 ± 3.4 days; P = 0.108).

CONCLUSION

Continuation of therapeutic anticoagulation during MICRA implantation appears to be feasible, safe and associated with shorter hospitalization among appropriately selected individuals.

Leadless solution for arrhythmia-related sudden unexpected death in epilepsy

A leadless pacemaker is a recently approved pacing technology that helps mitigate lead-related complications, but it has several limitations. Careful candidate selection is needed. Here, we demonstrate leadless pacing as the solution for prolonged postictal bradycardia/asystole; there is no consensus regarding pacemaker implantation for seizure patients with such a risk of sudden cardiac death.

Optimization of Lead Placement in the Right Ventricle During Cardiac Resynchronization Therapy. A Simulation Study

Patients suffering from heart failure and left bundle branch block show electrical ventricular dyssynchrony causing an abnormal blood pumping. Cardiac resynchronization therapy (CRT) is recommended for these patients. Patients with positive therapy response normally present QRS shortening and an increased left ventricle (LV) ejection fraction. However, around one third do not respond favorably. Therefore, optimal location of pacing leads, timing delays between leads and/or choosing related biomarkers is crucial to achieve the best possible degree of ventricular synchrony during CRT application. In this study, computational modeling is used to predict the optimal location and delay of pacing leads to improve CRT response. We use a 3D electrophysiological computational model of the heart and torso to get insight into the changes in the activation patterns obtained when the heart is paced from different regions and for different atrioventricular and interventricular delays. The model represents a heart with left bundle branch block and heart failure, and allows a detailed and accurate analysis of the electrical changes observed simultaneously in the myocardium and in the QRS complex computed in the precordial leads. Computational simulations were performed using a modified version of the O'Hara et al. action potential model, the most recent mathematical model developed for human ventricular electrophysiology. The optimal location for the pacing leads was determined by QRS maximal reduction. Additionally, the influence of Purkinje system on CRT response was assessed and correlation analysis between several parameters of the QRS was made. Simulation results showed that the right ventricle (RV) upper septum near the outflow tract is an alternative location to the RV apical lead. Furthermore, LV endocardial pacing provided better results as compared to epicardial stimulation. Finally, the time to reach the 90% of the QRS area was a good predictor of the instant at which 90% of the ventricular tissue was activated. Thus, the time to reach the 90% of the QRS area is suggested as an additional index to assess CRT effectiveness to improve biventricular synchrony.

Leadless Dual-Chamber Pacing: A Novel Communication Method for Wireless Pacemaker Synchronization

Contemporary leadless pacemakers only feature single-chamber pacing capability. This study presents a prototype of a leadless dual-chamber pacemaker. Highly energy-efficient intrabody communication was implemented for wireless pacemaker synchronization. Optimal communication parameters were obtained by in vivo and ex vivo measurements in the heart and blood. The prototype successfully performed dual-chamber pacing in vivo. The presented wireless communication method may in the future also enable leadless cardiac resynchronization therapy.

Use of leadless pacemakers in Europe: results of the European Heart Rhythm Association survey

The purpose of this European Heart Rhythm Association (EHRA) survey is to provide an overview of the current use of leadless pacemakers (LLPM) across a broad range of European centres. An online questionnaire was sent to centres participating in the EHRA Electrophysiology Research Network. Questions dealt with standards of care and policies used for patient management, indications, and techniques of implantation of LLPM. In total, 52 centres participated in the survey. Most (86%) reported using LLPM, although 82% of these centres implanted <30 LLPM devices during the last 12 months. Non-availability (36%), lack of reimbursement (55%), and cost of the device (91%) were factors limiting the use of LLPM. The most commonly reported indications for LLPM were permanent atrial fibrillation (83%), a history of complicated conventional pacemaker (87%), or an anticipated difficult vascular access (91%). Implantation of LLPM is perceived as an easy-to-do and safe procedure by most implanters (64%), while difficult or risky in 28%, and comparable to conventional pacemakers by only a few (8%). Local vascular complications were the most frequently reported major problems (28%), but a significant number of respondents (36%) have never encountered any issue after LLPM implantation. Although cost and reimbursement issues strongly influence the use of LLPM, most respondents (72%) anticipate a significant increase in device utilization within next 2 years.

Monocentric experience of leadless pacing with focus on challenging cases for conventional pacemaker

AIM

Leadless cardiac pacemaker has been developed to reduce complications related to cardiac pacing and is considered as an alternative to conventional pacemaker although safety and efficacy data in clinical practice are limited. The purpose of this study was to investigate the safety and efficacy profile of Micra Transcatheter Pacing System (TPS) used in daily clinical activity with a focus on challenging cases for conventional pacing.

METHODS

A total of 66 patients (46 men, 79.1 ± 9.7 years) having a Class I or II indication for ventricular pacing underwent a Micra TPS implant procedure. All patients were enrolled in a prospective registry. Follow-up visits were scheduled at discharge and after 1, 3, 6 and 12 months.

RESULTS

Primary indication for pacing was third degree atrioventricular block (30.3%), sinus node dysfunction (21.2%) or permanent atrial fibrillation with bradycardia (45.5%). The device was successfully implanted in 65 patients (98.5%). During follow-up of 10.4 ± 6.1 months (range 1-23 months), electrical measurements remained stable. Mean pacing capture threshold, pacing impedance and R-wave sensing were respectively 0.57 ± 0.32 V, 580 ± 103 Ohms, 10.62 ± 4.36 mV at the last follow-up. One major (loss of function) and three minor adverse events occurred. Pericardial effusion, dislodgement, device related infection or pacemaker syndrome were not observed. Micra TPS implantation was straightforward for patients with congenital or acquired cardiac and/or vascular abnormalities, previous tricuspid surgery and after heart transplantation.

CONCLUSION

Our experience confirms that implantation of Micra is safe and efficient in a real world population including patients who present a challenging condition for conventional pacing.

Artefacts in 1.5 Tesla and 3 Tesla cardiovascular magnetic resonance imaging in patients with leadless cardiac pacemakers

BACKGROUND

There are limited data on patients with leadless cardiac pacemakers (LCP) undergoing magnetic resonance imaging. The aim of this prospective, single-center, observational study was to evaluate artefacts on cardiovascular magnetic resonance (CMR) images in patients with LCP.

METHODS

Fifteen patients with Micra™ LCP, implanted at least 6 weeks prior to CMR scan, were enrolled and underwent either 1.5 Tesla or 3 Tesla CMR imaging. Artefacts were categorized into grade 1 (excellent image quality), grade 2 (good), grade 3 (poor) and grade 4 (non-diagnostic) for each myocardial segment. One patient was excluded because of an incomplete CMR investigation due to claustrophobia.

RESULTS

LCP caused an arc-shaped artefact (0.99 ± 0.16 cm2) at the right ventricular (RV) apex. Of 224 analyzed myocardial segments of the left ventricle (LV) 158 (70.5%) were affected by grade 1, 27 (12.1%) by grade 2, 17 (7.6%) by grade 3 and 22 (9.8%) by grade 4 artefacts. The artefact burden of grade 3 and 4 artefacts was significantly higher in the 3 Tesla group (3 Tesla vs 1.5 Tesla: 3.7 ± 1.6 vs 1.9 ± 1.4 myocardial segments per patient, p = 0.03). A high artefact burden was particularly observed in the mid anteroseptal, inferoseptal and apical septal myocardial segments of the LV and in the mid and apical segments of the RV. Quantification of LV function and assessment of valves were feasible in all patients. We did not observe any clinical or device-related adverse events.

CONCLUSION

CMR imaging in patients with LCP is feasible with excellent to good image quality in the majority of LV segments. The artefact burden is comparable small allowing an accurate evaluation of LV function, cardiac structures and valves. However, artefacts in the mid anteroseptal, inferoseptal and apical septal myocardial segments of the LV due to the LCP may impair or even exclude diagnostic evaluation of these segments. Artefacts on CMR images may be reduced by the use of 1.5 Tesla CMR scanners.

Imaging features of leadless cardiovascular devices

Cardiovascular devices and hemodynamic monitoring systems continue to evolve with the goal of allowing for rapid clinical intervention and management. Cardiovascular devices including the CardioMicroelectromechanical (CardioMEMS) device, implantable loop recorder, and right ventricular (RV) leadless pacemaker are now widely used for treatment and monitoring of advanced cardiac conditions, as many of these devices have been shown to significantly improve patient outcomes. Additionally, hemodynamic monitoring devices have shown utility in monitoring patients with aortic aneurysms after endovascular aortic repair (EVAR) for early detection of Type I and Type II endoleaks. There is limited published data regarding the imaging features of these devices. As these devices become more widely used, it is important for radiologists to become familiar with the normal imaging features and potential complications. The goal of this review is to summarize the data regarding the use of leadless cardiovascular devices including the CardioMEMS device, implantable loop recorder, and RV leadless pacemaker, and to present cases demonstrating their utility and normal imaging features.

Leadless Pacemakers - Implant, Explant and Long-Term Safety and Efficacy Data

Implantable cardiac pacemakers have seen remarkable progress in the last sixty years and remained as cornerstone therapy for symptomatic bradycardia. Despite this progress the current day traditional transvenous implanted pacemaker systems are limited by the need for a surgically created pocket for the generator, indwelling leads in the vascular system and lastly passage through the tricuspid valve. A majority of the implant and explant related complications are due to the surgical pocket and indwelling leads. Leadless pacemakers represent a major leap in technology and emerged as an alternative to traditional systems promises to eliminate lead and pocket associated complications. As with any disruptive technology, some questions remain unanswered with the leadless pacing systems, specifically longevity and end of life management for the device. Despite the unknowns, as the technology progresses, it is possible that pacing leads will become extinct and pacemakers will miniaturize even further. This review summarizes the available technology, implant and explant details, and long-term safety and efficacy data for leadless pacemakers.

Neointimal fibrotic lead encapsulation - Clinical challenges and demands for implantable cardiac electronic devices

Every tenth patient with a cardiac pacemaker or implantable cardioverter-defibrillator implanted is expected to have at least one lead problem in his lifetime. However, transvenous leads are often difficult to remove due to thrombotic obstruction or extensive neointimal fibrotic ingrowth. Despite its clinical significance, knowledge on lead-induced vascular fibrosis and neointimal lead encapsulation is sparse. Although leadless pacemakers are already available, their clinical operating range is limited. Therefore, lead/tissue interactions must be further improved in order to improve lead removals in particular. The published data on the coherences and issues related to lead associated vascular fibrosis and neointimal lead encapsulation are reviewed and discussed in this paper.

Inductively powered wireless pacing via a miniature pacemaker and remote stimulation control system

Pacemakers have existed for decades as a means to restore cardiac electrical rhythms. However, lead-related complications have remained a clinical challenge. While market-released leadless devices have addressed some of the issues, their pacer-integrated batteries cause new health risks and functional limitations. Inductive power transfer enables wireless powering of bioelectronic devices; however, Specific Absorption Rate and size limitations reduce power efficiency for biomedical applications. We designed a remote-controlled system in which power requirements were significantly reduced via intermittent power transfer to control stimulation intervals. In parallel, the cardiac component was miniaturized to facilitate intravascular deployment into the anterior cardiac vein. Given size constraints, efficiency was optimal via a circular receiver coil wrapped into a half-cylinder with a meandering tail. The pacemaker was epicardially tested in a euthanized pig at 60 beats per minute, 2 V amplitude, and 1 ms pulse width, restoring mean arterial pressure from 0 to 37 mmHg. Power consumption was 1 mW at a range of > 3 cm with no misalignment and at 2 cm with 45° displacement misalignment, 45° x-axis angular misalignment, or 45° y-axis angular misalignment. Thus, we demonstrated a remote-controlled miniaturized pacing system with low power consumption, thereby providing a basis for the next generation of wireless implantable devices.

The endlessness evolution of medicine, continuous increase in life expectancy and constant role of the physician

In this review, the endlessness evolution of medical science and medical technology, and its effects on disease metamorphosis and increased life expectancy are discussed. In certain instances, the past will be compared with the present and predictions for the future will be outlined. Further, the constant role of the physician in maintaining the health of human beings is emphasized in this endlessness evolution.

Leadless Cardiac Pacemakers: Current status of a modern approach in pacing

Since the first transvenous pacemaker implantation, which took place 50 years ago, important progress has been achieved in pacing technology. Consequently, at present, more than 700,000 pacemakers are implanted annually worldwide. However, conventional pacemakers' implantation has a non-negligible risk of periprocedural and long-term complications associated with the transvenous leads and pacemaker pocket. Recently, leadless pacing systems have emerged as a therapeutic alternative to conventional pacing systems that provide therapy for patients with bradyarrhythmias, while eliminating potential transvenous lead- and pacemaker pocket-related complications. Initial studies have demonstrated favorable efficacy and safety of currently developed leadless pacing systems, compared to transvenous pacemakers. In the present paper, we review the current evidence and highlight the advantages and disadvantages of this novel technology. New technological advances may allow the next generation of leadless pacemakers to further expand, thereby offering a wireless cardiac pacing in future.

Leadless Pacemakers

Leadless pacing is an emerging technology with the potential to significantly improve outcomes associated with the need for long-term pacing. Specifically, the major advantage of leadless systems is abolishing the need for transvenous leads and subcutaneous pockets, both of which account for most adverse events associated with traditional pacemakers. Two leadless pacemakers are currently available: the Nanostim (leadless cardiac pacemaker [LCP]) device (St. Jude Medical, Sylmar, California) and the Micra Transcatheter pacing system (Medtronic, Minneapolis, Minnesota). These 2 pacemakers have shown promising results in clinical trials. In conclusion, in this review we summarize the results of the 2 investigational device exemption trials and compare the pros and cons of these devices to traditional transvenous pacemakers.

Anaesthetic consideration in patients with cardiac implantable electronic devices scheduled for surgery

With advances in cardiology and cardiothoracic surgery, several newer implantable cardiac devices have become common in the surgical population. Multichamber pacemakers, implanted cardiac defibrillators and ventricular assist devices are frequent in current day practice. Many of the newer implantable cardiac electronic devices are targeted at managing heart failure. While managing such patients for non-cardiac surgeries, specific issues related to equipment characteristics and troubleshooting should be a priority for the anaesthesiologists. There is a possibility of malfunction of the devices resulting in catastrophic outcomes. Therefore, it is imperative to understand the pathophysiology, device characteristics and troubleshooting before embarking on anaesthetising patients with implantable cardiac electronic devices.

The Micra Leadless Transcatheter Pacemaker. Implantation and Mid-term Follow-up Results in a Single Center

INTRODUCTION AND OBJECTIVES

Currently, studies on the leadless pacemaker (Micra) have mostly been limited to clinical trials with less than 6 months' follow-up and they often fail to reflect real population outcomes. We sought to evaluate electrical parameters at implantation and chronologically during follow-up, as well as the safety of this new technique.

METHODS

This prospective, observational study included 30 consecutive patients, all ≥ 65 years, with an indication for single-chamber pacemaker implantation.

RESULTS

Successful implantation was accomplished in all patients referred for leadless implantation. The mean age was 79.4±6.4 years (range, 66-89 years); 20 (66.6%) were men and 28 had permanent atrial fibrillation (93.3%); 1 had atrial tachycardia and 1 had sinus rhythm. Concomitant atrioventricular node ablation was performed immediately after implantation in 5 patients (16.6%), and implantation was performed after transcatheter aortic valve implantation in 2. The procedure was performed under an uninterrupted anticoagulation regimen (maximum INR 2.4) in 23 patients (76.6%). With the exception of 1 moderate pericardial effusion without tamponade, there were no severe complications. The mean follow-up was 5.3±3.3 months and 4 patients had more than 1 year of follow-up. Sensing and pacing parameters were stable both at implantation and during the short- to mid-term follow-up.

CONCLUSIONS

Implantation of leadless pacemakers is feasible, safe and provides advantages over the conventional system. Further studies with longer follow-up periods will be needed before these devices become widely used in routine clinical practice.

Congenital and childhood atrioventricular blocks: pathophysiology and contemporary management

Atrioventricular block is classified as congenital if diagnosed in utero, at birth, or within the first month of life. The pathophysiological process is believed to be due to immune-mediated injury of the conduction system, which occurs as a result of transplacental passage of maternal anti-SSA/Ro-SSB/La antibodies. Childhood atrioventricular block is therefore diagnosed between the first month and the 18th year of life. Genetic variants in multiple genes have been described to date in the pathogenesis of inherited progressive cardiac conduction disorders. Indications and techniques of cardiac pacing have also evolved to allow safe permanent cardiac pacing in almost all patients, including those with structural heart abnormalities.

CONCLUSION

Early diagnosis and appropriate management are critical in many cases in order to prevent sudden death, and this review critically assesses our current understanding of the pathogenetic mechanisms, clinical course, and optimal management of congenital and childhood AV block.

WHAT IS KNOWN

• Prevalence of congenital heart block of 1 per 15,000 to 20,000 live births. AV block is defined as congenital if diagnosed in utero, at birth, or within the first month of life, whereas childhood AV block is diagnosed between the first month and the 18th year of life. As a result of several different etiologies, congenital and childhood atrioventricular block may occur in an entirely structurally normal heart or in association with concomitant congenital heart disease. Cardiac pacing is indicated in symptomatic patients and has several prophylactic indications in asymptomatic patients to prevent sudden death. • Autoimmune, congenital AV block is associated with a high neonatal mortality rate and development of dilated cardiomyopathy in 5 to 30 % cases. What is New: • Several genes including SCN5A have been implicated in autosomal dominant forms of familial progressive cardiac conduction disorders. • Leadless pacemaker technology and gene therapy for biological pacing are promising research fields. In utero percutaneous pacing appears to be at high risk and needs further development before it can be adopted into routine clinical practice. Cardiac resynchronization therapy is of proven value in case of pacing-induced cardiomyopathy.