Helix-fixation leadless pacemaker as a potential alternative to conventional transvenous pacemaker in post-Mustard baffle stenosis

Obstruction of a systemic venous pathway is relatively common after the Mustard operation. A helix-fixation leadless pacemaker was successfully implanted in the subpulmonic but morphologic LV in a d-TGA patient with post-Mustard baffle stenosis and failure of a previously implanted epicardial lead.

Leadless pacemaker tine damage and fracture: novel complications of a novel device fixation mechanism

Background

Leadless pacemakers represent a paradigm-changing advancement. However, they required innovative and novel device design, including the use of nitinol tines for fixation.

Objective

We aimed to understand the potential for fracture in the novel tine-based fixation mechanism.

Methods

A retrospective approach was used to search the MAUDE (Manufacturer and User Facility Device Experience) database for events related to Micra pacemaker tine fracture and damage. Review of each report was performed to ascertain frequency of tine fracture and damage.

Results

Of 4241 MAUDE reports (2104 Micra VR, 2167 Micra AV), 230 included the terms "fracture" or "tine," which yielded 7 tine fractures and 19 reports of tine damage. Overall, 2 (29%) of 7 tine fractures were noted during implantation, whereas 2 (29%) of 7 were discovered ≥1 week after implantation; 5 (71%) of 7 tine fracture reports described no associated patient signs or symptoms, and 4 (57%) of 7 described no change in pacing parameters. Tine damage occurred during implantation in 16 (84%) of 19, compared with 2 (11%) of 19 noted ≥1 week after implantation; 15 (79%) of 19 tine damage cases reported no associated signs or symptoms, and 7 (37%) of 19 described no changes in pacing parameters. Among all cases, there was 1 case of device embolization.

Conclusion

The novel tine-based fixation mechanism appears susceptible to a novel failure mechanism-tine fracture and/or damage. Our analysis suggests these events may not always be associated with adverse signs or symptoms. Diligent attention at implantation, and future bench or clinical studies are needed to understand the rate, clinical impact, and mechanism of such failures, and role of surveillance.

A comparative study of the two leadless pacemakers in clinical practice

INTRODUCTION

AVEIR-VR leadless pacemaker (LP) was recently approved for clinical use. Although trial data were promising, post-approval real world data with regard to its effectiveness and safety is lacking. To report our early experience with AVEIR-VR LP with regard to its effectiveness and safety and compare it with MICRA-VR.

METHODS

The first 25 patients to undergo AVEIR-VR implant at our institution between June and November 2022, were compared to 25 age- and sex-matched patients who received MICRA-VR implants.

RESULTS

In both groups, mean age was 73 years and 48% were women. LP implant was successful in 100% of patients in both groups. Single attempt deployment was achieved in 80% of AVEIR-VR and 60% of MICRA-VR recipients (p = 0.07). Fluoroscopy, implant, and procedure times were numerically longer in the AVEIR-VR group compared to MICRA-VR group (p > 0.05). No significant periprocedural complications were noted in both groups. Incidence of ventricular arrhythmias were higher in the AVEIR-VR group (20%) compared to the MICRA-VR group (0%) (p = 0.043). At 2 and 8 weeks follow-up, device parameters remained stable in both groups with no device dislodgements. The estimated battery life at 8 weeks was significantly longer in the AVEIR-VR group (15 years) compared to the MICRA-VR group (8 years) (p = 0.047). With 3-4 AVEIR-VR implants, the learning curve for successful implantation reached a steady state.

CONCLUSION

Our initial experience with AVEIR-VR show that it has comparable effectiveness and safety to MICRA-VR. Larger sample studies are needed to confirm our findings.

Preclinical cardiac perforation reduction in leadless pacing: An update to the Micra leadless pacemaker delivery system

BACKGROUND

Leadless pacemakers have been developed to avoid some of the complications that are associated transvenous pacemakers. Pericardial effusion is a rare complication of leadless pacemaker implantation, which may result from perforation of the delivery catheter. In this study, we describe preclinical perforation performance of an updated Micra delivery catheter.

METHODS

To assess preclinical perforation performance of the updated delivery catheter, three analyses were performed. First, Finite Element Analysis (FEA) computational modeling was performed to estimate the target tissue stress during Micra delivery catheter tenting. Second, benchtop perforation forces of ovine tissue were recorded for the original and updated delivery catheters. Finally, a Monte-Carlo simulation combining human cadaveric Micra implant forces and human ventricular tissue perforation properties was performed to estimate clinical perforation performance.

RESULTS

FEA modeling demonstrated a 66% reduction in target tissue stress when using the updated Micra delivery catheter (6.2 vs. 2.2 psi, Original vs. Updated Micra delivery catheter). Updated Micra delivery catheters required 20% more force to perforate porcine ventricular tissues in benchtop testing (μupd  = 26.9N vs. μorg  = 22.4N, p = .01). Monte-Carlo Simulation of catheter performance in human cadaveric tissues predicts 28.5% reduction of catheter-perforated cases with the updated delivery catheter.

CONCLUSIONS

This study, using computer modelling and benchtop experimentation, has indicated that increased surface area and rounding of the updated Micra catheter tip significantly improves preclinical perforation performance. It will be important to evaluate the impact of these catheter design changes with robust registry data.

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.

Sheath shape pattern during leadless pacemaker implantation

PURPOSE

Options for shaping the delivery sheath of leadless pacemakers (LPs) based on the cardiac anatomy of patients are limited. We predicted the shape of the LP sheath during implantation using preoperative computed tomography (CT) and intraoperative fluoroscopy.

METHODS

Forty-eight patients with implanted LPs due to symptomatic bradyarrhythmia were divided into two groups, α-loop and non-α-loop, based on the shape of the LP delivery sheath head at implantation. Angles between the inferior vena cava (IVC) and the interventricular septum (IVST), and the IVC and right ventricular apex (RVA) were measured by CT. The relationship between the final sheath shape and position of the IVC and the right or left side of the line drawn vertically from the deflection point of the sheath in the LAO view on fluoroscopy was assessed.

RESULTS

Angles between the IVC and IVST (44.4 ± 5.9° vs. 50.2 ± 6.8°) and IVC and RVA (52.5 ± 5.3° vs. 58.8 ± 7.8°) on CT were significantly (p < 0.01) smaller in the α-loop group. To predict the α-loop shape, a combined IVC-IVST angle < 50° and IVC-RVA angle < 55° revealed higher sensitivity (81.8%). The delivery sheath positioned right of the vertical line was more frequent in the α-loop group (90.9% vs. 23.1%, p < 0.01).

CONCLUSIONS

When the preoperatively calculated angles of IVC to IVST and RVA on CT were narrow, the right side of the sheath in the IVC from the vertical line drawn from the deflection point in the LAO view indicated the need to shape the delivery sheath head into an α-loop during LP implantation.

A Robot Mimicking Heart Motions: An Ex-Vivo Test Approach for Cardiac Devices

Purpose

The pre-clinical testing of cardiovascular implants gains increasing attention due to the complexity of novel implants and new medical device regulations. It often relies on large animal experiments that are afflicted with ethical and methodical challenges. Thus, a method for simulating physiological heart motions is desired but lacking so far.

Methods

We developed a robotic platform that allows simulating the trajectory of any point of the heart (one at a time) in six degrees of freedom. It uses heart motion trajectories acquired from cardiac magnetic resonance imaging or accelero-meter data. The rotations of the six motors are calculated based on the input trajectory. A closed-loop controller drives the platform and a graphical user interface monitors the functioning and accuracy of the robot using encoder data.

Results

The robotic platform can mimic physiological heart motions from large animals and humans. It offers a spherical work envelope with a radius of 29 mm, maximum acceleration of 20 m/s² and maximum deflection of ±19° along all axes. The absolute mean positioning error in x-, y- and z-direction is 0.21 ±0.06, 0.31 ±0.11 and 0.17 ±0.12 mm, respectively. The absolute mean orientation error around x-, y- and z-axis (roll, pitch and yaw) is 0.24 ±0.18°, 0.23 ±0.13° and 0.18 ±0.18°, respectively.

Conclusion

The novel robotic approach allows reproducing heart motions with high accuracy and repeatability. This may benefit the device development process and allows re-using previously acquired heart motion data repeatedly, thus avoiding animal trials.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13239-021-00566-3.

Predictors of increase in pacing threshold after transcatheter pacing system implantation due to micro-dislodgement

BACKGROUND

Achieving a favorable pacing threshold with a Micra transcatheter pacing system (Micra-TPS) is needed to reduce battery depletion. In some cases, the threshold increases shortly after the device is implanted, and a higher pacing threshold may be required. This study aims to identify the causes and predictors of the increase in pacing threshold observed shortly after Micra-TPS implantation.

METHODS

The study included 64 consecutive patients who underwent Micra-TPS implantation between 2017 and 2020. The patients were divided into two groups depending on their pacing threshold: the increased pacing threshold (IPT) group (threshold increased by ≥0.5 V/0.24 ms within 1 month of implantation) and the stable pacing threshold (SPT) group.

RESULTS

Excluding four patients who could not be followed up, of the 60 remaining patients, nine (15%) were in the IPT group and 51 (85%) were in the SPT group. The IPT group had significantly lower implant impedance values and higher implant thresholds than the SPT group (582 ± 59 vs 755 ± 167 Ω [P < .001] and 1.29 ± 0.87 vs 0.71 ± 0.40 V/0.24 ms [P = .014]). Implant impedance and threshold may serve as predictors of a threshold increase after implantation (area under the curve: 0.737-0.943 and 0.586-0.926, respectively).

CONCLUSIONS

An IPT was noted shortly after Micra-TPS implantation owing to micro-dislodgement because of insufficient anchoring of the device to the myocardium. Impedance >660 Ω and threshold <1.0 V/0.24 ms may predict an increase in pacing threshold.

Low delay rate adaptive pacemaker using FPGA embedded piezoelectric sensor

This paper presents the hardware implementation of low delay, power-efficient, rate-adaptive dual-chamber pacemaker (RDPM) using a piezoelectric sensor. Rate adaptive pacemaker has the ability to sense the patient's activity by means of some special sensors and it controls the pacing rate according to the patient's activity. Ideally, there should be no delay between sensing and the subsequent pacing operation performed by the pacemaker. However, delay in the responses of various components in the circuitry produces an accumulative delay effect in any practical circuit. Physical activity and the physiological needs of the patient can be easily adapted by the rate-responsive pacemakers using a wide range of sensor information. The piezo-electric sensor recognises the pressure on human muscles because of physical activity and converts it to an electrical signal, which is received by the pulse generator of the pacemaker. When the patient is in the rest mode, the heart rate is the only parameter that is to be detected by the pacemaker. Thus, the heart rate and the physical activity both are the inevitable parameters for the design of RDPM. Performance analysis of the proposed RDPM shows a significant reduction in the delay between sensing and pacing. Device utility analysis shows that the proposed design not only requires lesser memory but also reduces the number of components on the chip. Therefore, it becomes very clear that the proposed pacemaker design will consume much lesser power.

Safety of leadless pacemaker implantation in the very elderly

BACKGROUND

The Micra leadless pacemaker (MLP) has proven to be an effective alternative to a traditional transvenous pacemaker (TVP). However, there has been concern about using the MLP in frail elderly patients because of the size of the implant sheath and perceived risk of perforation.

OBJECTIVES

The objectives of this study were to report the safety of the MLP and compare MPLs with TVPs in the very elderly.

METHODS

All patients 85 years and older who received an MLP or a single-chamber TVP across 6 hospitals in the Northwell Health system from December 2015 to November 2019 were included. Demographic characteristics, procedural details, and procedure-related complications were reviewed.

RESULTS

Over 4 years, 564 patients underwent MLP implantation. During this time, 183 MLPs and 119 TVPs were implanted in patients 85 years and older. The mean age was 89.7 ± 3.4 years, and 47.4% were men. MLP implantation was successful in all but 3 patients (98.4% success rate). There was no difference in procedure-related complications (3.3% vs 5.9%; P = .276). Complications included 5 (2.7%) access site hematomas in the MLP group, 3 (2.5%) in the TVP group, 1 (0.5 vs 0.8%) pericardial effusion in each group, and 3 (2.5%) acute lead dislodgments (<24 hours) in the TVP group. MLP implantation resulted in a significantly shorter mean procedure time (35.7 ± 23.0 minutes vs 62.3 ± 31.5 minutes, P < .001).

CONCLUSION

In a large multicenter study of patients 85 years and older, MLP implantation (1) was successful in 98.4% of patients, (2) was safe with no difference in procedure-related complications compared to the TVP group, and (3) resulted in significantly shorter procedure times.

The unstable pacing thresholds of the leadless transcatheter pacemaker affected by body positions in subacute phase after implant

Background

If the threshold at implant of leadless transcatheter pacemakers (LTPs) is less than 2.0 V, pacing thresholds reportedly decrease significantly by 1 month and maintain an optimal value of less than 1.0 V by 6 months.

Case summary

We report a case series of two patients with unstable pacing thresholds of the LTPs in the subacute phase after implant. The first patient (77-year-old man) was implanted an LTP for sick sinus syndrome. At that time of implant, the pacing threshold was 0.9 V at 0.24 ms. At 1 week and 1 month later, the threshold had increased to more than 2.0 V at 0.24 ms. We investigated the trend data for the week and found variations in the threshold. The second patient (81-year-old man) was implanted an LTP for bradycardia and atrial fibrillation. The pacing threshold at implantation was 0.63 V at 0.24 ms. One week later, the threshold had increased in supine position and decreased in sitting position. The trend data for the week were fluctuating greatly.

Discussion

The pacing threshold may increase to more than 2.0 V with significant fluctuation on assessment at 1 week and 1 month after implantation in association with changes in body position, even though we confirmed a stable threshold at implant. If an increased threshold is observed, it is necessary to check the trend data and threshold in each body position.

An Implantable Accelerometer-Based Heart-Monitoring Device With Improved Positional Stability

This paper reports recent results from an ongoing effort to develop an implantable accelerometer-based heart-monitoring device for ischemia monitoring. The latest device prototype utilizes a new and more compact accelerometer (1.2 × 1.5 × 0.8 mm3), a prototype device from Bosch SensorTec, Reutlingen, Germany. This paper presents the fabrication and testing of the device, including an explorative study of the effect of the capsule shape on the stability of the implanted device in the heart tissue. The stability study indicated sufficient stability of the device and a higher resistance to retraction for one of the capsule designs. The device was able to carry out acceleration monitoring and it meets the leakage current requirements of the IEC60601 standard.

A Leadless Intracardiac Transcatheter Pacing System

BACKGROUND

A leadless intracardiac transcatheter pacing system has been designed to avoid the need for a pacemaker pocket and transvenous lead.

METHODS

In a prospective multicenter study without controls, a transcatheter pacemaker was implanted in patients who had guideline-based indications for ventricular pacing. The analysis of the primary end points began when 300 patients reached 6 months of follow-up. The primary safety end point was freedom from system-related or procedure-related major complications. The primary efficacy end point was the percentage of patients with low and stable pacing capture thresholds at 6 months (≤2.0 V at a pulse width of 0.24 msec and an increase of ≤1.5 V from the time of implantation). The safety and efficacy end points were evaluated against performance goals (based on historical data) of 83% and 80%, respectively. We also performed a post hoc analysis in which the rates of major complications were compared with those in a control cohort of 2667 patients with transvenous pacemakers from six previously published studies.

RESULTS

The device was successfully implanted in 719 of 725 patients (99.2%). The Kaplan-Meier estimate of the rate of the primary safety end point was 96.0% (95% confidence interval [CI], 93.9 to 97.3; P<0.001 for the comparison with the safety performance goal of 83%); there were 28 major complications in 25 of 725 patients, and no dislodgements. The rate of the primary efficacy end point was 98.3% (95% CI, 96.1 to 99.5; P<0.001 for the comparison with the efficacy performance goal of 80%) among 292 of 297 patients with paired 6-month data. Although there were 28 major complications in 25 patients, patients with transcatheter pacemakers had significantly fewer major complications than did the control patients (hazard ratio, 0.49; 95% CI, 0.33 to 0.75; P=0.001).

CONCLUSIONS

In this historical comparison study, the transcatheter pacemaker met the prespecified safety and efficacy goals; it had a safety profile similar to that of a transvenous system while providing low and stable pacing thresholds. (Funded by Medtronic; Micra Transcatheter Pacing Study ClinicalTrials.gov number, NCT02004873.).