Sex differences in leadless pacemaker implantation: A propensity-matched analysis from the i-LEAPER registry

BACKGROUND

The impact of sex in clinical and procedural outcomes in leadless pacemaker (LPM) patients has not yet been investigated.

OBJECTIVE

The purpose of this study was to investigate sex-related differences in patients undergoing LPM implantation.

METHODS

Consecutive patients enrolled in the i-LEAPER registry were analyzed. Comparisons between sexes were performed within the overall cohort using an adjusted analysis with 1:1 propensity matching for age and comorbidities. The primary outcome was the comparison of major complication rates. Sex-related differences regarding electrical performance and all-cause mortality during follow-up were deemed secondary outcomes.

RESULTS

In the overall population (n = 1179 patients; median age 80 years), 64.3% were men. After propensity matching, 738 patients with no significant baseline differences among groups were identified. During median follow-up of 25 [interquartile range 24-39] months, female sex was not associated with LPM-related major complications (hazard ratio [HR] 2.03; 95% confidence interval [CI] 0.70-5.84; P = .190) or all-cause mortality (HR 0.98; 95% CI 0.40-2.42; P = .960). LPM electrical performance results were comparable between groups, except for a higher pacing impedance in women at implant and during follow-up (24 months: 670 [550-800] Ω vs 616 [530-770] Ω; P = .014) that remained within normal limits.

CONCLUSION

In a real-world setting, we found differences in sex-related referral patterns for LPM implantation with an underrepresentation of women, although major complication rate and LPM performance were comparable between sexes. Female patients showed higher impedance values, which had no impact on overall device performance. Electrical parameters remained within normal limits in both groups during the entire follow-up.

First long-term outcome data for the MicraVR™ transcatheter pacing system: data from the largest prospective German cohort

AIMS

The MicraVR™ transcatheter pacing system (TPS) has been implemented into clinical routine for several years. The primary recipients are patients in need for VVI pacing due to bradycardia in the setting of atrial fibrillation (AF). Implantation safety and acute success have been proven in controlled studies and registries. So far only few long-term real-life data on TPS exist. We report indication, procedure and outcome data from two high-volume implanting German centers.

METHODS

Between 2016 and 2019, 188 (of 303) patients were included. During follow-up (FU), TPS interrogation was performed after 4 weeks and thereafter every 6 months.

RESULTS

Indication for TPS implantation in 159/188 (85%) patients was permanent or intermittent AV block III° in the setting of atrial fibrillation. The mean procedure duration was 50 min [35.0-70.0]. The average acute values after system release were: thresholds: 0.5V [0.38-0.74]/0.24ms; R-wave sensing: 10.0mV [8.1-13.5]; impedance: 650 Ohm [550-783]; RV-pacing demand: 16.9% [0.9-75.9]; and battery status: 3.15 V [3.12-3.16]. During FU of 723.4 ± 597.9 days, neither pacemaker failure nor infections were reported. Long-term FU revealed: thresholds: 0.5V [0.38-0.63]/0.24 ms; sensing: 12.3mV [8.9-17.2]; impedance: 570 Ohm [488-633]; RV-pacing demand: 87.1% [29.5-98.6]; and battery status 3.02 V [3.0-3.1]. Forty-three patients died from not-device-related causes.

CONCLUSION

This to date largest German long-term dataset for MicraVR™ TPS implantation revealed stable device parameter. Foremost, battery longevity seems to fulfill predicted values despite a significant increase in RV-pacing demand over time and even in patients with consecutive AV-node ablation. Of note, no infections or system failure were observed.

Outcomes of leadless pacemaker implantation following transvenous lead extraction in high-volume referral centers: Real-world data from a large international registry

BACKGROUND

Limited data on the real-world safety and efficacy of leadless pacemakers (LPMs) post-transvenous lead extraction (TLE) are available.

OBJECTIVE

The purpose of this study was to assess the long-term safety and effectiveness of LPMs following TLE in comparison with LPMs de novo implantation.

METHODS

Consecutive patients who underwent LPM implantation in 12 European centers joining the International LEAdless PacemakEr Registry were enrolled. The primary end point was the comparison of LPM-related complication rate at implantation and during follow-up (FU) between groups. Differences in electrical performance were deemed secondary outcomes.

RESULTS

Of the 1179 patients enrolled, 15.6% underwent a previous TLE. During a median FU of 33 (interquartile range 24-47) months, LPM-related major complications and all-cause mortality did not differ between groups (TLE group: 1.6% and 5.4% vs de novo group: 2.2% and 7.8%; P = .785 and P = .288, respectively). Pacing threshold (PT) was higher in the TLE group at implantation and during FU, with very high PT (>2 V@0.24 ms) patients being more represented than in the de novo implantation group (5.4% vs 1.6 %; P = .004). When the LPM was deployed at a different right ventricular (RV) location than the one where the previous transvenous RV lead was extracted, a lower proportion of high PT (>1-2 V@0.24 ms) patients at implantation, 1-month FU, and 12-month FU (5.9% vs 18.2%, P = .012; 3.4% vs 12.9%, P = .026; and 4.3% vs 14.5%, P = .037, respectively) was found.

CONCLUSION

LPMs showed a satisfactory safety and efficacy profile after TLE. Better electrical parameters were obtained when LPMs were implanted at a different RV location than the one where the previous transvenous RV lead was extracted.

Predictors of Pacing Capture Threshold Exacerbation After Leadless Pacemaker Implantation

The predictors of pacing capture threshold (PCT) exacerbation after leadless pacemaker implantation remain unknown. We analyzed the predictors of poor PCT by identifying risk factors using multivariate logistic regression analysis for 211 patients with leadless pacemaker implantation. Twenty patients met the criteria for elevated PCT levels and were categorized in the poor PCT group. Multivariate analyses revealed that PCT (P < 0.0001) and pacing impedance (P = 0.03) were independent predictors of PCT exacerbation. Elevated PCT levels and low pacing impedance during leadless pacemaker implantation were potential risk factors for the replacement of leadless pacemakers after the procedure.

Fluoroscopic Predictors of Acceptable Capture threshold during the Implantation of the Micra Transcatheter Pacing System

Introduction

Few predictors of low capture threshold before the deployment of the Micra transcatheter pacing system (Micra TPS) have been determined. We aimed to identify fluoroscopic predictors of an acceptable capture threshold before Micra TPS deployment.

Methods

Sixty patients were successfully implanted with Micra TPS. Before deployment, gooseneck appearance of the catheter shaft was quantified using the angle between the tangent line of the shaft and the cup during diastole in the right anterior oblique (RAO) view. The direction of the device cup toward the ventricular septum was evaluated using the angle between the cup and the horizontal plane in the left anterior oblique (LAO) view.

Results

Of the 95 deployments we evaluated, 56 achieved an acceptable capture threshold of ≤2.0 V at 0.24 ms. In this acceptable threshold group, the deflection angle of the gooseneck shaft was significantly larger and the device cup was placed more horizontally with a lower elevation angle compared with those in the high threshold group. A deflection angle of ≥6° and an elevation angle of ≤30° were identified as the predictors of an acceptable capture threshold after deployment. An acceptable capture threshold was achieved in 24/31 (77.4%) patients in whom either angle criterion was satisfied at the first deployment.

Conclusions

Diastolic gooseneck appearance of the delivery catheter in the RAO view or near‐horizontal direction in the LAO view predicts an acceptable capture threshold after deployment. The shape of the delivery catheter before deployment should be evaluated using multiple fluoroscopic views to ensure successful implantation of Micra TPS.

Intraoperative sensing increase predicts long-term pacing threshold in leadless pacemakers

PURPOSE

High pacing threshold (HPT) and very high pacing threshold (VHPT) are known to have a negative impact on leadless pacemaker battery longevity, representing the most common reason for device repositioning. In this study, we evaluated if intraoperative electrical parameters recorded during Micra™ VR implant would be able to predict device performance during follow-up (FU).

METHODS

A total of 93 patients undergoing Micra™ VR implant were retrospectively considered. Patients were enrolled in the study if electrical assessment was performed at least twice at implant, at Micra™ final positioning and after removal of the delivery system. All patients received a FU visit at 1 and 12 month after discharge. R-wave sensing amplitude, pacing threshold (PT), and impedance were recorded at each visit.

RESULTS

When compared to the first assessment, R-wave sensing amplitude increased by 19.1% after 13 ± 4 min (+ 1.71 ± 0.2 mV, 95% CI 1.4 to 2.02; p < .001). Conversely, there was a significant PT decrease of 22.1% at 12-month FU (- 0.22 ± 0.03 V, 95% CI - 0.13 to - 0.31; p < .001). Among patients with HPT, acute increase of R-wave sensing of 1.5 mV after 14 ± 4 min predicted a significant reduction of PT below 1 V/0.24, at 12-month post-implant (R = 0.72, 95% CI 0.13 to 0.33, p < .001), with a sensitivity of 87.5% (95% CI 0.61-0.98) and a specificity of 88.8% (95% CI 0.51-0.99).

CONCLUSION

A 1.5-mV increase in R-wave amplitude at implant is predictive of PT normalization (< 1.0 V/0.24 ms) at 12-month FU. This finding may have practical implications for device repositioning in case of HPT recording at implant.

Leadless pacemaker implantation sites confirmed by computed tomography and their parameters and complication rates

BACKGROUND

Implantations of leadless pacemakers in the septum lower the risk of cardiac perforation. However, the relationship between the implantation site and the success rate, complication rate, and pacemaker parameters are not well-investigated.

METHODS

Patients who underwent leadless pacemaker implantation with postprocedural computed tomography (CT) between September 2017 and November 2020 were analyzed. Septum was targeted with fluoroscopic guidance with contrast injection. We divided patients into two groups based on the implantation site confirmed by CT: septal and non-septal, which included the anterior/posterior edge of the septum and free wall. We compared the complication rates and pacemaker parameters between the two groups.

RESULTS

A total of 67 patients underwent CT after the procedure; among them, 28 were included in the septal group and 39 were included in the non-septal group. The non-septal group had significantly higher R wave amplitudes (6.5 ± 3.3 vs. 9.7 ± 3.9 mV, p = .001), lower pacing threshold (1.0 ± 0.94 vs. 0.63 ± 0.45 V/0.24 ms, p = .02), and higher pacing impedance (615 ± 114.1 vs. 712.8 ± 181.3 ohms, p = .014) after the procedure compared to the septal group. Cardiac injuries were observed in four patients (one cardiac tamponade, one possible apical hematoma, two asymptomatic pericardial effusion), which were only observed in the non-septal group.

CONCLUSIONS

Leadless pacemaker implantation may be technically challenging with substantial number of patients with non-septal implantation when assessed by CT. Septal implantation may have a lower risk of cardiac injury but may lead to inferior pacemaker parameters than non-septal implantation.

Efficacy and safety of leadless pacemaker: A systematic review, pooled analysis and meta-analysis

Background

Leadless pacemakers have been designed as an alternative to transvenous systems which avoid some of the complications associated with transvenous devices. We aim to perform a systematic review of the literature to report the safety and efficacy findings of leadless pacemakers.

Methods

We searched MEDLINE and EMBASE to identify studies reporting the safety, efficacy and outcomes of patients implanted with a leadless pacemaker. The pooled rate of adverse events was determined and random-effects meta-analysis was performed to compare rates of adverse outcomes for leadless compared to transvenous pacemakers.

Results

A total of 18 studies were included with 2496 patients implanted with a leadless pacemaker and success rates range between 95.5 and 100%. The device or procedure related death rate was 0.3% while any complication and pericardial tamponade occurred in 3.1% and 1.4% of patients, respectively. Other complications such as pericardial effusion, device dislodgement, device revision, device malfunction, access site complications and infection occurred in less than 1% of patients. Meta-analysis of four studies suggests that there was no difference in hematoma (RR 0.67 95%CI 0.21–2.18, 3 studies), pericardial effusion (RR 0.59 95%CI 0.15–2.25, 3 studies), device dislocation (RR 0.33 95%CI 0.06–1.74, 3 studies), any complication (RR 0.44 95%CI 0.17–1.09, 4 studies) and death (RR 0.45 95%CI 0.15–1.35, 2 studies) comparing patients who received leadless and transvenous pacemakers.

Conclusion

Leadless pacemakers are safe and effective for patients who have an indication for single chamber ventricular pacing and the findings appear to be comparable to transvenous pacemakers.

Leadless pacemakers: A review of current data and future directions

Leadless pacemakers (LPs) have revolutionized the field of pacing by miniaturizing pacemakers and rendering them completelty intracardiac, hence reducing complications related to pacemaker pockets and transvenous leads. However, first generation LPs appear to be associated with a higher rate of myocardial perforation as compared to transvenous pacemakers (TV-PPM). Currently, LPs are predominantly designed to pace the right ventricle with no LPs that provide atrial or biventricular pacing. In this article, we review the available data on LPs while advocating for the need for a randomized controlled trial comparing LPs to TV-PPMs. In addition, we review the future directions of leadless devices.

Safety and Efficacy of Leadless Pacemakers: A Systematic Review and Meta-Analysis

Background Leadless pacemaker is a novel technology, and evidence supporting its use is uncertain. We performed a systematic review and meta-analysis to examine the safety and efficacy of leadless pacemakers implanted in the right ventricle. Methods and Results We searched PubMed and Embase for studies published before June 6, 2020. The primary safety outcome was major complications, whereas the primary efficacy end point was acceptable pacing capture threshold (≤2 V). Pooled estimates were calculated using the Freedman-Tukey double arcsine transformation. Of 1281 records screened, we identified 36 observational studies of Nanostim and Micra leadless pacemakers, with most (69.4%) reporting outcomes for the Micra. For Micra, the pooled incidence of complications at 90 days (n=1608) was 0.46% (95% CI, 0.08%-1.05%) and at 1 year (n=3194) was 1.77% (95% CI, 0.76%-3.07%). In 5 studies with up to 1-year follow-up, Micra was associated with 51% lower odds of complications compared with transvenous pacemakers (3.30% versus 7.43%; odds ratio [OR], 0.49; 95% CI, 0.34-0.70). At 1 year, 98.96% (95% CI, 97.26%-99.94%) of 1376 patients implanted with Micra had good pacing capture thresholds. For Nanostim, the reported complication incidence ranged from 6.06% to 23.54% at 90 days and 5.33% to 6.67% at 1 year, with 90% to 100% having good pacing capture thresholds at 1 year (pooled result not estimated because of the low number of studies). Conclusions Most studies report outcomes for the Micra, which is associated with a low risk of complications and good electrical performance up to 1-year after implantation. Further data from randomized controlled trials are needed to support the widespread adoption of these devices in clinical practice.

Leadless pacemaker implant with concomitant atrioventricular node ablation: Experience with the Micra transcatheter pacemaker

Background

The feasibility and outcomes of concomitant atrioventricular node ablation (AVNA) and leadless pacemaker implant are not well studied. We report outcomes in patients undergoing Micra implant with concomitant AVNA.

Methods

Patients undergoing AVNA at the time of Micra implant from the Micra Transcatheter Pacing (IDE) Study, Continued Access (CA) study, and Post‐Approval Registry (PAR) were included in the analysis and compared to Micra patients without AVNA. Baseline characteristics, acute and follow‐up outcomes, and electrical performance were compared between patients with and without AVNA during the follow‐up period.

Results

A total of 192 patients (mean age 77.4 ± 8.9 years, 72% female) underwent AVNA at the time of Micra implant and were followed for 20.4 ± 15.6 months. AVNA patients were older, more frequently female, and tended to have more co‐morbid conditions compared with non‐AVNA patients (N = 2616). Implant was successful in 191 of 192 patients (99.5%). The mean pacing threshold at implant was 0.58 ± 0.35 V and remained stable during follow‐up. Major complications within 30 days occurred more frequently in AVNA patients than non‐AVNA patients (7.3% vs. 2.0%, p < .001). The risk of major complications through 36‐months was higher in AVNA patients (hazard ratio: 3.81, 95% confidence interval: 2.33–6.23, p < .001). Intermittent loss of capture occurred in three AVNA patients (1.6%), all were within 30 days of implant and required system revision. There were no device macrodislodgements or unexpected device malfunctions.

Conclusion

Concomitant AVN ablation and leadless pacemaker implant is feasible. Pacing thresholds are stable over time. However, patient comorbidities and the risk of major complications are higher in patients undergoing AVNA.

A Predictive Model for the Long-Term Electrical Performance of a Leadless Transcatheter Pacemaker

OBJECTIVES

This study sought to formulate a predictive model for describing the long-term electrical performance of Micra (Medtronic, Mounds View, Minnesota).

BACKGROUND

The Micra leadless pacemaker is an alternative ventricular pacing option that avoids the pitfalls of transvenous leads. However, well-defined metrics to predict the long-term electrical performance of the device are lacking.

METHODS

We identified all patients who underwent successful Micra implantation enrolled in the investigational device exemption study, continued access study, or post-approval registry with complete 1-year post-implantation data or system revision due to elevated thresholds (N = 1,843). The analysis endpoint was an elevated pacing capture threshold (PCT) at ≥12 months post-implantation, defined as ≥2.0 V at 0.24 ms or an increase of ≥1.5 V from implantation or need for system revision due to elevated thresholds at ≤12 months post-implantation. We evaluated for univariate and multivariate associations between patient and device characteristics at implantation and for elevated thresholds at 12 months.

RESULTS

Among the total cohort, 75 patients (4.1%) had elevated thresholds at 12 months; of these, 13 required system revisions. Predictors associated with elevated thresholds in univariate analysis included the total number of deployments (excluded from the multivariable model), impedance and PCT at implantation, male sex, history of diabetes, and ischemic cardiomyopathy. Multivariable regression modeling found that male sex, history of diabetes, implantation PCT of ≥2 V, and impedance of <800 Ω were independent predictors of elevated PCT at 12 months (all p < 0.05).

CONCLUSION

A history of diabetes, male sex, elevated PCT, and low impedance at implantation were independent predictors of elevated thresholds at 12 months. These metrics represent the foundation of a simple tool to aid in procedural decision making.

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.