Leadless pacemakers at 5-year follow-up: the Micra transcatheter pacing system post-approval registry

BACKGROUND AND AIMS

Prior reports have demonstrated a favourable safety and efficacy profile of the Micra leadless pacemaker over mid-term follow-up; however, long-term outcomes in real-world clinical practice remain unknown. Updated performance of the Micra VR leadless pacemaker through five years from the worldwide post-approval registry (PAR) was assessed.

METHODS

All Micra PAR patients undergoing implant attempts were included. Endpoints included system- or procedure-related major complications and system revision rate for any cause through 60 months post-implant. Rates were compared through 36 months post-implant to a reference dataset of 2667 transvenous pacemaker patients using Fine-Gray competing risk models.

RESULTS

1809 patients were enrolled between July 2015 and March 2018 and underwent implant attempts from 179 centres in 23 countries with a median follow-up period of 51.1 months (IQR: 21.6-64.2). The major complication rate at 60 months was 4.5% [95% confidence interval (CI): 3.6%-5.5%] and was 4.1% at 36 months, which was significantly lower than the 8.5% rate observed for transvenous systems (HR: .47, 95% CI: .36-.61; P < .001). The all-cause system revision rate at 60 months was 4.9% (95% CI: 3.9%-6.1%). System revisions among Micra patients were mostly for device upgrades (41.2%) or elevated thresholds (30.6%). There were no Micra removals due to infection noted over the duration of follow-up. At 36 months, the system revision rate was significantly lower with Micra vs. transvenous systems (3.2% vs. 6.6%, P < .001).

CONCLUSIONS

Long-term outcomes with the Micra leadless pacemaker continue to demonstrate low rates of major complications and system revisions and an extremely low incidence of infection.

Outcomes of patients implanted with an atrioventricular synchronous leadless ventricular pacemaker in the Medicare population

BACKGROUND

The Micra AV Coverage with Evidence Development study is a novel analysis of utilization and outcomes associated with Micra AV leadless pacing in US Medicare patients.

OBJECTIVE

The purpose of this study was to describe patient characteristics, complications, and outcomes of patients implanted with a Micra AV leadless pacemaker compared with a contemporaneous cohort of patients implanted with a dual chamber transvenous pacemaker.

METHODS

Patients implanted with Micra AV (n = 7471) or a dual chamber transvenous pacemaker (n = 107,800) from February 5, 2020, through December 1, 2021, were identified using device registry-linked Medicare claims data. Acute complications were assessed at 30 days, and chronic complications, reinterventions, and all-cause mortality were assessed at 6 months.

RESULTS

Patients implanted with Micra AV had higher rates of end-stage renal disease (14.9% vs 2.0%; P < .0001) and overall comorbidity burden (mean Charlson Comorbidity Index 4.9 vs 3.8; P < .0001). There was no difference in the unadjusted rate of complications at 30 days (9.1% vs 8.7%; P = .61), and patients implanted with Micra AV had a significantly lower adjusted rate of complications (8.6% vs 11.0%; P < .0001). At 6 months, patients implanted with Micra AV had significantly lower rates of complications (adjusted hazard ratio 0.50; 95% confidence interval 0.43-0.57; P < .0001) and reinterventions (adjusted hazard ratio 0.46; 95% confidence interval 0.36-0.58; P < .0001). Patients implanted with Micra AV had higher all-cause mortality at 30 days and 6 months, likely because of differences in the underlying risk of mortality.

CONCLUSION

Patients implanted with Micra AV had similar rates of complications at 30 days and significantly lower rates of complications and reinterventions at 6 months, despite being sicker than patients implanted with a transvenous pacemaker.

Safety and Performance of the Micra VR Leadless Pacemaker in a Japanese Cohort - Comparison With Global Studies

BACKGROUND

The Micra leadless pacemaker has demonstrated favorable outcomes in global trials, but its real-world performance and safety in a Japan-specific population is unknown.Methods and Results: Micra Acute Performance (MAP) Japan enrolled 300 patients undergoing Micra VR leadless pacemaker implantation in 15 centers. The primary endpoint was the acute (30-day) major complication rate. The 30-day and 6-month major complication rates were compared to global Micra studies. All patients underwent successful implantation with an average follow-up of 7.23±2.83 months. Compared with previous Micra studies, Japanese patients were older, smaller, more frequently female, and had a higher pericardial effusion risk score. 11 acute major complications were reported in 10 patients for an acute complication rate of 3.33% (95% confidence interval: 1.61-6.04%), which was in line with global Micra trials. Pericardial effusion occurred in 4 patients (1.33%; 3 major, 1 minor). No procedure or device-related deaths occurred. Frailty significantly improved from baseline to follow-up as assessed by Japan Cardiovascular Health Study criteria.

CONCLUSIONS

In a Japanese cohort, implantation of the Micra leadless pacemaker had a high success rate and low major complication rate. Despite the Japan cohort being older, smaller, and at higher risk, the safety and performance was in line with global Micra trials.

Leadless versus transvenous single-chamber ventricular pacemakers: 3 year follow-up of the Micra CED study

INTRODUCTION

The Micra Coverage with Evidence Development (CED) Study is a novel comparative analysis of Micra (leadless VVI) and transvenous single-chamber ventricular pacemakers (transvenous VVI) using administrative claims data. To compare chronic complications, device reinterventions, heart failure hospitalizations, and all-cause mortality after 3 years of follow-up.

METHODS

US Medicare claims data linked to manufacturer device registration information were used to identify Medicare beneficiaries with a de novo implant of either a Micra VR leadless VVI or transvenous VVI pacemaker from March 9, 2017 to December 31, 2018. Unadjusted and propensity score overlap-weight adjusted Fine-Gray competing risk models were used to compare outcomes at 3 years.

RESULTS

Leadless VVI patients (N = 6219) had a 32% lower rate of chronic complications and a 41% lower rate of reintervention compared with transvenous VVI patients (N = 10 212) (chronic complication hazard ratio [HR] 0.68; 95% confidence interval [CI], 0.59-0.78; reintervention HR 0.59; 95% CI 0.44-0.78). Infections rates were significantly lower among patients with a leadless VVI (<0.2% vs. 0.7%, p < .0001). Patients with a leadless VVI also had slightly lower rates of heart failure hospitalization (HR 0.90; 95% CI 0.84-0.97). There was no difference in the adjusted 3-year all-cause mortality rate (HR 0.97; 95% CI, 0.92-1.03).

CONCLUSION

This nationwide comparative evaluation of leadless VVI versus transvenous VVI de novo pacemaker implants demonstrated that the leadless group had significantly fewer complications, reinterventions, heart failure hospitalizations, and infections than the transvenous group at 3 years, confirming that the previously reported shorter-term advantages associated with leadless pacing persist and continue to accrue in the medium-to-long-term.

Two-year outcomes of leadless vs. transvenous single-chamber ventricular pacemaker in high-risk subgroups

AIMS

This study compares clinical outcomes between leadless pacemakers (leadless-VVI) and transvenous ventricular pacemakers (transvenous ventricular permanent-VVI) in subgroups of patients at higher risk of pacemaker complications.

METHODS AND RESULTS

This study is based on the Micra Coverage with Evidence Development (CED) study. Patients from the Micra CED study were considered in a high-risk subgroup if they had a diagnosis of chronic kidney disease Stages 4-5 (CKD45), end-stage renal disease, malignancy, diabetes, tricuspid valve disease (TVD), or chronic obstructive pulmonary disease (COPD) 12 months prior to pacemaker implant. A pre-specified set of complications and reinterventions were identified using diagnosis and procedure codes. Competing risks models were used to compare reinterventions and complications between leadless-VVI and transvenous-VVI patients within each subgroup; results were adjusted for multiple comparisons. A post hoc comparison of a composite outcome of reinterventions and device complications was conducted. Out of 27 991 patients, 9858 leadless-VVI and 12 157 transvenous-VVI patients have at least one high-risk comorbidity. Compared to transvenous-VVI patients, leadless-VVI patients in four subgroups [malignancy, HR 0.68 (0.48-0.95); diabetes, HR 0.69 (0.53-0.89); TVD, HR 0.60 (0.44-0.82); COPD, HR 0.73 (0.55-0.98)] had fewer complications, in three subgroups [diabetes, HR 0.58 (0.37-0.89); TVD, HR 0.46 (0.28-0.76); COPD, HR 0.51 (0.29-0.90)) had fewer reinterventions, and in four subgroups (malignancy, HR 0.52 (0.32-0.83); diabetes, HR 0.52 (0.35-0.77); TVD, HR 0.44 (0.28-0.70); COPD, HR 0.55 (0.34-0.89)] had lower rates of the combined outcome.

CONCLUSION

In a real-world study, leadless pacemaker patients had lower 2-year complications and reinterventions rates compared with transvenous-VVI pacing in several high-risk subgroups.

TRIAL REGISTRATION

ClinicalTrials.gov ID NCT03039712.

Correlation between AV synchrony and device collected AM-VP sequence counter in atrioventricular synchronous leadless pacemakers: A real-world assessment

INTRODUCTION

Micra atrioventricular (AV) provides leadless atrioventricular synchronous pacing by sensing atrial contraction (A4 signal). Real-world operation and reliability of AV synchrony (AVS) assessment using device data have not been described. The purposes of this study were to (1) assess the correlation between AVS and atrial mechanical sensed-ventricular pacing (AM-VP) percentages in patients with permanent high-degree AV block and (2) report on the real-world effectiveness of Micra AV.

METHODS

The correlation between ECG-determined AVS in-clinic and device-collected %AM-VP was assessed using data from 40 patients with high-degree AV block enrolled in the Micra Atrial tRacking using a Ventricular AccELerometer (MARVEL) 2 study. A retrospective analysis to assess continuously-sampled %AM-VP since last session, device programming, and electrical parameters was performed using Micra AV transmissions from the Medtronic CareLink database. Patients with transmissions ≥180 days postimplant were included.

RESULTS

Among the 40 MARVEL 2 AV block patients with a median %VP of 99.7%, AVS was highly correlated with AM-VP (median AVS 87.1%, median AM-VP 79.1%; R²  = 0.764, p < .001). The CareLink cohort included 4384 patients programmed to VDD mode. The mean A4 amplitude was 2.3 ± 1.8 m/s² at implant and 2.3 ± 1.6 m/s² at 28 weeks. In patients with %VP >90% (n = 1662), the median %AM-VP was 74.7%. For the full cohort, median %VP was 65.6% and median projected battery longevity was 10.5 years.

CONCLUSION

In patients with a high pacing burden, %AM-VP provides a reasonable estimation of AVS. The first large real-world analysis of Micra AV patients with >90% VP showed stable atrial sensing over time with a median %AM-VP, a correlate of AVS, of 74.7%.

Ambulatory atrioventricular synchronous pacing over time using a leadless ventricular pacemaker: Primary results from the AccelAV study

BACKGROUND

Previous studies demonstrated that accelerometer-based, mechanically timed atrioventricular synchrony (AVS) is feasible using a leadless ventricular pacemaker.

OBJECTIVE

The purpose of this study was to determine the performance of a leadless ventricular pacemaker with accelerometer-based algorithms that provide AVS pacing.

METHODS

AccelAV was a prospective, single-arm study to characterize AVS in patients implanted with a Micra AV, which uses the device accelerometer to mechanically detect atrial contractions and promote VDD pacing. The primary objective was to characterize resting AVS at 1 month in patients with complete atrioventricular block (AVB) and normal sinus function.

RESULTS

A total of 152 patients (age 77 ± 11 years; 48% female) from 20 centers were enrolled and implanted with a leadless pacemaker. Among patients with normal sinus function and complete AVB (n = 54), mean resting AVS was 85.4% at 1 month, and ambulatory AVS was 74.8%. In the subset of patients (n = 20) with programming optimization, mean ambulatory AVS was 82.6%, representing a 10.5% improvement (P <.001). Quality of life as measured by the EQ-5D-3L (EuroQol Five-Dimensions Three-Level questionnaire) improved significantly from preimplant to 3 months (P = .031). In 37 patients with AVB at both 1 and 3 months, mean AVS during rest did not differ (86.1% vs 84.1%; P = .43). There were no upgrades to dual-chamber devices or cardiac resynchronization therapy through 3 months.

CONCLUSION

Accelerometer-based mechanical atrial sensing provided by a leadless pacemaker implanted in the right ventricle significantly improves quality of life in a select cohort of patients with AV block and normal sinus function. AVS remained stable through 3 months, and there were no system upgrades to dual-chamber pacemakers.

Chronic outcomes of leadless vs transvenous single chamber ventricular pacemakers in high-risk subgroups

Background

The Micra leadless pacemaker (LP-VVI) has been shown to have lower chronic complications and device-related reinterventions compared to transvenous ventricular pacemakers (TV-VVI) in a large, real-world population. This study compares the complication and reintervention rate in subgroups with comorbidities associated with higher risk of pacemaker complications and hypothesized to benefit from leadless pacing.

Methods

The longitudinal Micra Coverage with Evidence Development (CED) Study compared the outcomes of Medicare patients receiving LP-VVI to those receiving a TV-VVI in the US. Patients in the Micra CED study were included in this study if they had a diagnosis of chronic kidney disease Stages 4–5 (CKD45), end-stage renal disease (ESRD), malignancy, diabetes, tricuspid valve disease (TVD), or chronic obstructive pulmonary disease (COPD) on any administrative claim in the 12 months prior to pacemaker implant. A pre-specified set of complications and system reinterventions were identified using the relevant diagnosis and procedure codes. Adjusted and unadjusted Fine-Gray competing risks models were used to compare reinterventions and complications between LP-VVI and TV-VVI patients within each subgroup. All results were adjusted for multiple comparisons using a Bonferroni correction. An ad-hoc comparison of a composite endpoint of select reinterventions (system replacement, removal, revision, and lead reinterventions) and device complications was also conducted.

Results

The sample size of patients in each subgroup ranged from 2,032 patients with ESRD to 11,936 patients with diabetes. The percent of LP-VVI patients in each subgroup ranged from 44.0 in the TVD subgroup to 74.9 in the ESRD subgroup. Compared to patients implanted with a TV-VVI, patients with a LP-VVI with malignancy, diabetes, TVD, and COPD had significantly fewer complications (Table 1; Malignancy, HR 0.68, [0.48–0.95]; Diabetes, HR 0.69, [0.53–0.89]; TVD, HR 0.60 [0.44–0.82]; COPD, HR 0.73, [0.55–0.98]). LP-VVI patients with diabetes, TVD, and COPD also had lower rates of reintervention (Table; Diabetes, HR 0.58, [0.37–0.89]; TVD, HR 0.46 [0.28–0.76]; COPD, HR 0.51, [0.29–0.90]). LP-VVI patients with malignancy, diabetes, TVD, and COPD had lower rates of the combined endpoint of device complications and select reinterventions (Table; Malignancy, HR 0.52, [0.32–0.83]; Diabetes, HR 0.52, [0.35–0.77]; TVD, HR 0.44 [0.28–0.70]; COPD, HR 0.55, [0.34–0.89]).

Conclusions

In a real-world study of US Medicare patients, the leadless pacemaker was associated with lower rates of chronic complications and reinterventions at 2 years compared with TV-VVI pacing in several high-risk subgroups.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Medtronic

Leadless vs. transvenous single-chamber ventricular pacing in the Micra CED study: 2-year follow-up

AIMS

Clinical trials have demonstrated the safety and efficacy of the Micra leadless VVI pacemaker; however, longer-term outcomes in a large, real-world population with a contemporaneous comparison to transvenous VVI pacemakers have not been examined. We compared reinterventions, chronic complications, and all-cause mortality at 2 years between leadless VVI and transvenous VVI implanted patients.

METHODS AND RESULTS

The Micra Coverage with Evidence Development study is a continuously enrolling, observational, cohort study of leadless VVI pacemakers in the US Medicare fee-for-service population. Patients implanted with a leadless VVI pacemaker between March 9, 2017, and December 31, 2018, were identified using Medicare claims data linked to manufacturer device registration data (n = 6219). All transvenous VVI patients from facilities with leadless VVI implants during the study period were obtained directly from Medicare claims (n = 10 212). Cox models were used to compare 2-year outcomes between groups. Compared to transvenous VVI, patients with leadless VVI had more end-stage renal disease (12.0% vs. 2.3%) and a higher Charlson comorbidity index (5.1 vs. 4.6). Leadless VVI patients had significantly fewer reinterventions [adjusted hazard ratio (HR) 0.62, 95% confidence interval (CI) 0.45-0.85, P = 0.003] and chronic complications (adjusted HR 0.69, 95% CI 0.60-0.81, P < 0.0001) compared with transvenous VVI patients. Adjusted all-cause mortality at 2 years was not different between the two groups (adjusted HR 0.97, 95% CI 0.91-1.04, P = 0.37).

CONCLUSION

In a real-world study of US Medicare patients, the Micra leadless VVI pacemaker was associated with a 38% lower adjusted rate of reinterventions and a 31% lower adjusted rate of chronic complications compared with transvenous VVI pacing. There was no difference in adjusted all-cause mortality at 2 years.

Development and validation of a risk score for predicting pericardial effusion in patients undergoing leadless pacemaker implantation: experience with the Micra transcatheter pacemaker

AIMS

There is limited information on what clinical factors are associated with the development of pericardial effusion after leadless pacemaker implantation. We sought to determine predictors of and to develop a risk score for pericardial effusion in patients undergoing Micra leadless pacemaker implantation attempt.

METHODS AND RESULTS

Patients (n = 2817) undergoing implant attempt from the Micra global trials were analysed. Characteristics were compared between patients with and without pericardial effusion (including cardiac perforation and tamponade). A risk score for pericardial effusion was developed from 18 pre-procedural clinical variables using lasso logistic regression. Internal validation and future prediction performance were estimated using bootstrap resampling. The scoring system was also externally validated using data from the Micra Acute Performance European and Middle East (MAP EMEA) registry. There were 32 patients with a pericardial effusion [1.1%, 95% confidence interval (CI): 0.8-1.6%]. Following lasso logistic regression, 11 of 18 variables remained in the model from which point values were assigned. The C-index was 0.79 (95% CI: 0.71-0.88). Patient risk score profile ranged from -4 (lowest risk) to 5 (highest risk) with 71.8% patients considered low risk (risk score ≤0), 16.6% considered medium risk (risk score = 1), and 11.7% considered high risk (risk score ≥2) for effusion. The median C-index following bootstrap validation was 0.73 (interquartile range: 0.70-0.75). The C-index based on 9 pericardial effusions from the 928 patients in the MAP EMEA registry was 0.68 (95% CI: 0.52-0.83). The pericardial effusion rate increased significantly with additional Micra deployments in medium-risk (P = 0.034) and high-risk (P < 0.001) patients.

CONCLUSION

The overall rate of pericardial effusion following Micra implantation attempt is 1.1% and has decreased over time. The risk of pericardial effusion after Micra implant attempt can be predicted using pre-procedural clinical characteristics with reasonable discrimination.

CLINICAL TRIAL REGISTRATION

The Micra Post-Approval Registry (ClinicalTrials.gov identifier: NCT02536118), Micra Continued Access Study (ClinicalTrials.gov identifier: NCT02488681), and Micra Transcatheter Pacing Study (ClinicalTrials.gov identifier: NCT02004873).

Leadless Pacemaker Implant, Anticoagulation Status, and Outcomes: Results From The Micra Transcatheter Pacing System Post-Approval Registry

BACKGROUND

Early results from the Micra investigational trial and Micra post-approval registry (PAR) demonstrated excellent safety and device performance; however, outcomes based upon anticoagulation status at implant have not been evaluated.

OBJECTIVE

To report implant characteristics, perforation rate and vascular related events based upon perioperative oral anticoagulation (AC) strategy in patients undergoing Micra implant.

METHODS

We compared procedure characteristics, major complications, and vascular events, including pericardial effusion, stratified by any AE (including major complications, minor complications and observations) or major complication only according to AC status in the Micra PAR.

RESULTS

Among 1795 patients with AC status available, 585 were not on AC, 795 had AC interrupted, and 415 had AC continued during Micra implant. Non-AC patients tended to be younger, with less history of AF and COPD, and more history of dialysis than interrupted and continued patients. The implant success rate was similar for all groups (99.1%-99.8%). Through 30 days post implant, the overall major complication rate was 3.1% for the non-AC group, 2.6% for the interrupted group, and 1.5% for the continued group. The combined rate for any vascular or pericardial effusion AE did not differ significantly between AC strategies (6.5%, 4.8%, and 3.6% respectively).

CONCLUSION

Implant of Micra appears to be safe and feasible regardless of an interrupted or continued peri-procedural oral anticoagulation strategy, with no increased risk of perforation rate or vascular complications.

Leadless pacemaker implant in patients requiring CIED extraction: outcomes based upon timing of extraction

Background

Previous results from global Micra Transcatheter Pacemaker clinical trials have demonstrated leadless pacing as a safe and attractive option for patients with prior cardiac implantable electronic device (CIED) infection and extraction. Whether outcomes differ based upon the timing of prior device extraction has not been studied.

Purpose

To describe characteristics and outcomes of patients undergoing CIED extraction during or prior to Micra implantation.

Methods

Patients who underwent CIED explant and Micra implantation were identified from the Micra Post-Approval Registry and Micra Acute Performance studies. Baseline characteristics were summarized. A Fine-Gray competing risk model was used to compare risk for major complication through 24 months.

Results

Of the 2739 patients included in the studies, 99 (3.6%) patients had CIED extraction the day of Micra implantation (same day) and 127 (4.6%) patients had CIED extraction within 30 days prior to Micra implantation (prior). Although infection was the primary reason for CIED extraction in both groups, a larger proportion of prior patients underwent extraction for this reason (87.4% vs. 42.4%). In contrast, more same day patients underwent CIED extraction for physician/elective reasons (16.2% vs. 3.1%). Same day patients prior device history included pacemaker (42 dual chamber and 30 single chamber), ICD (1 single chamber and 4 dual chamber), CRT (7 CRT-ICD and 13 CRT-P) while prior patients device history included pacemaker (29 single chamber, 80 dual chamber), ICD (3 dual chamber), CRT (5 CRT-ICD and 7 CRT-P). Overall, patients with extraction were aged 72.8±14.3 years, predominantly male (65.9%), and medical history was similar between groups, with the exception to CHF, which was higher for the same day group (18.2% vs 6.3%, P=0.021). The implant success rate was 98.0% for same day patients and 100% for prior patients. Median procedure duration was not significantly different between the groups (26.0 minutes and 25.0 minutes for same day and prior, respectively). Average follow-up duration was 16.5±13.8 months (range 0–53.4) for same day patients and 18.2±15.2 months (range 0–58.3) for subsequent patients. The rate of acute major complications (&lt;30 days) was 5.1% for same day and 3.2% for prior. Through 24 months, the rate of major complications was 6.4% for same day and 6.0% for prior (HR: 1.19, 95% CI: 0.40 – 3.50, P=0.76, Figure). The rate of major complications related to infection was low and did not differ by group (1.01% vs. 1.57%, P=1.00)

Conclusion

The Micra leadless pacemaker was implanted with a high success rate following CIED extraction. Outcomes following CIED extraction appear similar, whether the extraction is performed during or prior to Micra implant.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): Medtronic, Inc. Risk of major complications

Contemporaneous Comparison of Outcomes Among Patients Implanted With a Leadless vs Transvenous Single-Chamber Ventricular Pacemaker

Question

How do the performance of leadless VVI pacemakers and transvenous VVI pacemakers compare in a contemporaneous Medicare population?

Findings

In this cohort study including 15 408 patients, despite significant differences in patient characteristics, patients in whom a leadless pacemaker was implanted were observed to have higher rates of pericardial effusion and/or perforation but lower rates of other device-related complications and requirements for device revision at 6 months.

Meaning

The results from this study further develop the evidence on leadless pacemakers in practice and can inform shared decision-making about device choice for patients and physicians.

Importance

The safety and efficacy of leadless VVI pacemakers have been demonstrated in multiple clinical trials, but the comparative performance of the device in a large, real-world population has not been examined.

Objective

To compare patient characteristics and complications among patients implanted with leadless VVI and transvenous VVI pacemakers.

Design, Setting, Participants

The Longitudinal Coverage With Evidence Development Study on Micra Leadless Pacemakers (Micra CED) is a continuously enrolling observational cohort study evaluating complications, utilization, and outcomes of leadless VVI pacemakers in the US Medicare fee-for-service population. Patients implanted between March 9, 2017, and December 1, 2018, were identified and included. All Medicare patients implanted with leadless VVI and transvenous VVI pacemakers during the study period were enrolled. Patients with less than 12 months of continuous enrollment in Medicare prior to leadless VVI or transvenous VVI implant and with evidence of a prior cardiovascular implantable electronic device were excluded, leaving 5746 patients with leadless VVI pacemakers and 9662 patients with transvenous VVI pacemakers. Data were analyzed from May 2018 to April 2021.

Exposures

Medicare patients implanted with leadless VVI pacemakers or transvenous VVI pacemakers.

Main Outcomes and Measures

The main outcomes were acute (30-day) complications and 6-month complications.

Results

Of 15 408 patients, 6701 (43.5%) were female, and the mean (SD) age was 81.0 (8.7) years. Compared with patients with transvenous VVI pacemakers, patients with leadless VVI pacemakers were more likely to have end-stage kidney disease (690 [12.0%] vs 226 [2.3%]; P < .001) and a higher mean (SD) Charlson Comorbidity Index score (5.1 [3.4] vs 4.6 [3.0]; P < .001). The unadjusted acute complication rate was higher in patients with leadless VVI pacemakers relative to transvenous VVI pacemakers (484 of 5746 [8.4%] vs 707 of 9662 [7.3%]; P = .02). However, there was no significant difference in overall acute complication rates following adjustment for patient characteristics (7.7% vs 7.4%; risk difference, 0.3; 95% CI, −0.6 to 1.3; P = .49). Pericardial effusion and/or perforation within 30 days was significantly higher among patients with leadless VVI pacemakers compared with patients with transvenous VVI pacemakers in both unadjusted and adjusted models (unadjusted, 47 of 5746 [0.8%] vs 38 of 9662 [0.4%]; P < .001; adjusted, 0.8% vs 0.4%; risk difference, 0.4; 95% CI, 0.1 to 0.7; P = .004). Patients implanted with leadless VVI pacemakers had a lower rate of 6-month complications compared with patients implanted with transvenous VVI pacemakers (unadjusted hazard ratio, 0.84; 95% CI, 0.68-1.03; P = .10; adjusted hazard ratio, 0.77; 95% CI, 0.62-0.96; P = .02).

Conclusions and Relevance

In this study, despite significant differences in patient characteristics, patients in whom a leadless pacemaker was implanted were observed to have higher rates of pericardial effusion and/or perforation but lower rates of other device-related complications and requirements for device revision at 6 months. Understanding the benefits and risks associated with leadless VVI pacemakers compared with transvenous VVI pacemakers can help clinicians and patients make informed treatment decisions.

Behavior of AV synchrony pacing mode in a leadless pacemaker during variable AV conduction and arrhythmias

Introduction

MARVEL 2 assessed the efficacy of mechanical atrial sensing by a ventricular leadless pacemaker, enabling a VDD pacing mode. The behavior of the enhanced MARVEL 2 algorithm during variable atrio‐ventricular conduction (AVC) and/or arrhythmias has not been characterized and is the focus of this study.

Methods

Of the 75 patients enrolled in the MARVEL 2 study, 73 had a rhythm assessment and were included in the analysis. The enhanced MARVEL 2 algorithm included a mode‐switching algorithm that automatically switches between VDD and ventricular only antibradycardia pacing (VVI)‐40 depending upon AVC status.

Results

Forty‐two patients (58%) had persistent third degree AV block (AVB), 18 (25%) had 1:1 AVC, 5 (7%) had variable AVC status, and 8 (11%) had atrial arrhythmias. Among the 42 patients with persistent third degree AVB, the median ventricular pacing (VP) percentage was 99.9% compared to 0.2% among those with 1:1 AVC. As AVC status changed, the algorithm switched to VDD when the ventricular rate dropped less than 40 bpm. During atrial fibrillation (AF) with ventricular response greater than 40 bpm, VVI‐40 mode was maintained. No pauses longer than 1500 ms were observed. Frequent ventricular premature beats reduced the percentage of AV synchrony. During AF, the atrial signal was of low amplitude and there was infrequent sensing.

Conclusion

The mode switching algorithm reduced VP in patients with 1:1 AVC and appropriately switched to VDD during AV block. No pacing safety issues were observed during arrhythmias.

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.

Patient selection, pacing indications, and subsequent outcomes with de novo leadless single-chamber VVI pacing

AIMS

Patient selection is a key component of securing optimal patient outcomes with leadless pacing. We sought to describe and compare patient characteristics and outcomes of Micra patients with and without a primary pacing indication associated with atrial fibrillation (AF) in the Micra IDE trial.

METHODS AND RESULTS

The primary outcome (risk of cardiac failure, pacemaker syndrome, or syncope related to the Micra system or procedure) was compared between successfully implanted patients from the Micra IDE trial with a primary pacing indication associated with AF or history of AF (AF group) and those without (non-AF group). Among 720 patients successfully implanted with Micra, 228 (31.7%) were in the non-AF group. Reasons for selecting VVI pacing in non-AF patients included an expectation for infrequent pacing (66.2%) and advanced age (27.2%). More patients in the non-AF group had a condition that precluded the use of a transvenous pacemaker (9.6% vs. 4.7%, P = 0.013). Atrial fibrillation patients programmed to VVI received significantly more ventricular pacing compared to non-AF patients (median 67.8% vs. 12.6%; P < 0.001). The overall occurrence of the composite outcome at 24 months was 1.8% with no difference between the AF and non-AF groups (hazard ratio 1.36, 95% confidence interval 0.45-4.2; P = 0.59).

CONCLUSION

Nearly one-third of patients selected to receive Micra VVI therapy were for indications not associated with AF. Non-AF VVI patients required less frequent pacing compared to patients with AF. Risks associated with VVI therapy were low and did not differ in those with and without AF.

Leadless pacemaker implant in patients with a history of open heart surgery: experience with the Micra transcatheter pacemaker

Background

The Micra transcatheter pacemaker has demonstrated a favorable safety and efficacy profile relative to transvenous pacing. Patients with a history of open heart surgery have a higher risk of complications with transvenous pacemakers during follow-up. The experience with leadless pacemakers among a large cohort of patients with a history of open heart surgery has not been reported.

Objective

To report outcomes in patients with a history of open heart surgery undergoing Micra implant.

Methods

Patients undergoing Micra implant from the Micra Transcatheter Pacing Post-Approval Registry (PAR) were included in the analysis. Baseline and procedural characteristics, major complications, and electrical performance were compared among patients with vs. without history of cardiac surgery.

Results

A total of 331 out of 1815 (18.2%) patients had a history of open heart surgery, underwent Micra implant, and were followed for 19.4±10.4 months. The mean age was 74.6±13.5 years, 40% were female. The most common cardiac surgery was aortic valve surgery (71%) followed by mitral valve surgery (39%). Patients with prior open-heart surgery were more likely to have contraindications to transvenous pacing, were more likely to be on oral anticoagulants, and had more co-morbidities including atrial fibrillation, heart failure, and coronary artery disease (all p&lt;0.005). Implantation was successful in 327 of 331 patients (98.8%) with a median procedure time of 29 minutes. Mean pacing capture thresholds (PCTs) at implant were 0.66±0.51V and remained stable through follow-up. There were 11 major complications in 10 cardiac surgery patients, with no device or procedure-related infections reported. The major complication rate was 3.1% (Figure) and was not significantly different than that of patients without a history of open heart surgery (HR: 0.85, P=0.640). There was 1 cardiac perforation (with no intervention required) in the open heart surgery group (0.3%) and there were 14 cardiac perforations (0.94%, P=0.332) in the non-open heart surgery group of which 10 required intervention.

Conclusion

The Micra transcatheter pacemaker can be safely implanted in patients with a history of open heart surgery, with a similar long-term safety profile to patients without a history of open heart surgery. Importantly, there were no device-related infections reported in either group.

Risk of Major Complication

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Medtronic, Inc.

Resource utilization associated with hospital and office-based insertion of a miniaturized insertable cardiac monitor: results from the RIO 2 randomized US study

Background: Previous studies support operational benefits when moving insertable cardiac monitor (ICM) insertions outside the cardiac catheterization/electrophysiology laboratories, but this has not been directly assessed in a randomized trial or when the procedure is specifically moved to the office setting. To gain insight, the RIO 2 US study collected resource utilization and procedure time intervals for ICM insertion in-office and in-hospital and these data were used to calculate costs associated with staff time and supply use in each setting.Methods and results: The Reveal LINQ In-Office 2 US study (randomized [1:1], multicenter, unblinded) included 482 patients to undergo insertion of the ICM in-hospital (in an operating room or CATH/EP laboratory) (n = 251) or in-office (n = 231). Detailed information on resource utilization was collected prospectively by the study and used to compare resource utilization and procedure time intervals during ICM insertion procedures performed in-office vs. in-hospital. In addition, costs associated with staff time and supply use in each setting were calculated retrospectively. Total visit duration (check-in to discharge) was 107 min shorter in-office vs. in-hospital (95% CI = 97-116 min; p < 0.001). Patient preparation and education in-office were more likely to occur in the same room as the procedure, compared with in-hospital (91.6% vs. 34.2%, p < 0.001 and 87.3% vs. 22.1%, p < 0.001, respectively). There was a reduction in registered nurse and cardiovascular/operating room technologist involvement in-office, accompanied by higher physician and medical assistant participation. Overall staff time spent per case was 75% higher in-hospital, leading to 50% higher staffing costs compared to in-office.Conclusions: ICM insertion in a physician's office vs. a hospital setting resulted in reduced patient visit time and reduced overall staff time, with a consequent reduction in staffing costs. Clinical trial registration: ClinicalTrials.gov NCT02395536.

298Atrioventricular synchronous pacing in leadless ventricular pacemaker is safe and effective in patients with paroxysmal AV block and atrial arrhythmias

Funding Acknowledgements

Medtronic, Inc.

Background/Introduction

Accelerometer (ACC)-based AV synchronous pacing by tracking atrial activity is feasible using a leadless ventricular pacemaker. Patients may experience variable AV conduction (AVC) and/or atrial arrhythmias during the lifetime of their device. ACC-based AV synchronous pacing should facilitate AVC and pace appropriately in those two common rhythms.

Purpose

To characterize the behavior of ACC-based AV synchronous pacing algorithms during paroxysmal AV block (AVB) and atrial arrhythmias.

Methods

The MARVEL2 (Micra Atrial tRacking using a Ventricular accELerometer) was a 5-hour acute study to assess the efficacy of atrial tracking with a temporarily downloaded algorithm into a Micra leadless pacemaker. Patients with a history of AVB were eligible for inclusion. The MARVEL2 algorithm included a mode-switching algorithm that switched between VDD and VVI-40 depending upon AVC status. The AVC algorithm requires 2 ventricular paces (VP) at 40 bpm out of 4 pacing cycles to switch to VDD.

Results

Overall, 75 patients (age 77.5 ± 11.8 years, 40% female, median time from Micra implant 9.7 months) from 12 centers worldwide were enrolled. During study procedures, 40 patients (53%) had normal sinus rhythm with complete AVB, 18 (24%) had 1:1 AVC, 5 (7%) had varying AVC status, 8 (11%) had atrial arrhythmias, and 2 other rhythms.  Two patients with complete AVB had the AVC mode switch feature disabled due to an idioventricular rate &gt;40 bpm.  Among the 40 subjects with a predominant 3rd degree AVB and normal sinus function the median %VP was 99.9% compared to 0.2% among those with 1:1 AVC (Figure). In the patients with 1:1 AVC, there were 64 opportunities to AVC mode switch with 48 switching to VDI-40. In the other 16 cases (2 patients) the mode remained VDD due to sinus bradycardia varying between 40-45 bpm. High %VP was observed in 2 patients with 1:1 AVC and sinus bradycardia &lt;40 bpm. The AVC mode switch minimized %VP (&lt;1%) in patients with PR intervals &gt; 300 ms (N = 2). Among patients with varying AVC, the algorithm appropriately switched to VDD when the ventricular rate was paced at 40 bpm. During infrequent AVB or AF with ventricular response &gt;40 bpm, VVI-40 mode was maintained.

In patients with AF, the ACC signal was of low amplitude and there was infrequent sensing, resulting in VP at the lower rate (50 bpm). In the one patient with atrial flutter, the ACC was intermittently detected, resulting in VP at 67 bpm (IQR 66-67 bpm).

Conclusion(s)

The mode switching algorithm in the MARVEL2 reduced %VP in patients with 1:1 AVC and appropriately switched to VDD during complete AVB.  If greater AV synchrony or rate support is required, disabling the AVC algorithm may be appropriate for low grade AVB or idioventricular rhythms. In the presence of atrial arrhythmias, the algorithm paced near the lower rate.

Abstract Figure. Distribution of VP% by heart rhythm

Evaluation of stroke incidence with duty-cycled multielectrode-phased radiofrequency ablation of persistent atrial fibrillation results of the VICTORY AF Study

INTRODUCTION

The VICTORY AF Study was designed to evaluate the risk of the procedure and/or device-related strokes in patients with PersAF on warfarin undergoing ablation with a phased radiofrequency (RF) system.

METHODS

The VICTORY AF trial was a prospective, multicenter, single-arm, investigational study. PersAF patients on vitamin K antagonism without major structural heart disease or history of stroke/transient ischemic attack undergoing phased RF ablation for atrial fibrillation (AF) were included. The primary outcome was the incidence of the procedure and/or device-related stroke within 30 days of the ablation by a board-certified neurologist's assessment. The secondary outcomes were an acute procedural success, 6 months effectiveness (defined as the reduction in AF/atrial flutter episodes lasting ≥10 minutes by 48-hour Holter 6 months postablation) and the number of patients with pulmonary vein (PV) stenosis.

RESULTS

A total of 129 (108 PersAF, 21 long-standing PersAF) patients were treated (mean age: 60.6 ± 7.7; 79.8% male, 54.3% CHA2Ds2-VASc score ≥ 2). Two nondisabling strokes were reported (1.6%); one before discharge and the second diagnosed at the 30-day visit. Due to slow enrollment, the study was terminated before reaching the 95% one-sided upper confidence boundary for stroke incidence. Acute procedural success was 93.8%, and at 6 months, 72.8% of patients demonstrated ≥90% reduction in AF burden, 78.9% were off all antiarrhythmic drugs. There were no patients with PV stenosis of greater than 70%.

CONCLUSIONS

VICTORY AF demonstrated a 1.6% incidence of stroke in PersAF undergoing ablation with a phased RF system which did not meet statistical confidence due to poor enrollment. The secondary outcomes suggest comparable efficacy to phased RF in the tailored treatment of permanent AF trial. Rigorous clinical evaluation of the stroke risk of new AF ablation technologies as well as restriction to Vitamin K antagonist anticoagulation appears to be unachievable goals in a clinical multicenter IDE trial of AF ablation in the current era.

Using Medicare Claims to Identify Acute Clinical Events Following Implantation of Leadless Pacemakers

Background

There is heightened interest in how real-world data (RWD) can be used to supplement or replace traditional mechanisms for collecting clinical information. A critical component in evaluating utility of RWD is assessing the validity and reliability of event measurement. Only two studies have validated Medicare claims with physician-adjudicated data collected in a clinical study and none in the pacemaker patient population. This study compares events identified in physician-adjudicated clinical registry data collected in the Micra Post-Approval Registry (PAR) with events identified via Medicare administrative claims in the Micra Coverage with Evidence (CED) Study.

Methods

Patients who were dually enrolled in the Micra CED and the Micra PAR between March 9, 2017 and December 1, 2017 were included in the validation analysis. All patients intended to be implanted with a Micra device were eligible for participation in the Micra PAR. All Medicare fee-for-service beneficiaries implanted with a Micra device who met the 12-month continuous enrollment criteria were included in the Micra CED. We compared the count of acute (30-day) complications identified in the Medicare claims and the physician-adjudicated PAR data to assess agreement between data sources.

Results

There were 230 patients dually enrolled in the Micra CED and Micra PAR studies during the study period. Overall, there were 17 acute events reported in either the Micra CED or the Micra PAR, with 95% agreement in the identification of events and absence of events between studies. Study disagreement between events reported in either study varied: arteriovenous fistula (50%), pulmonary embolism (67%), hemorrhage/hematoma (75%), and deep vein thrombosis (100%). Among physician-adjudicated events, there was no disagreement between the Micra CED and Micra PAR studies in any event type.

Conclusion

Findings from this study demonstrate high agreement in event identification between Medicare claims data and registries for patients implanted with Micra leadless pacemakers.

5970Morbidity and mortality in patients precluded for transvenous pacemaker implantation: experience with the Micra transcatheter pacemaker

Background

The Micra transcatheter pacemaker has proven to be a safe and effective alternative to transvenous pacemakers (TVPs). However, the safety profile after Micra implantation in patients deemed poor candidates for TVPs is poorly understood.

Purpose

To evaluate the safety and all-cause mortality outcomes in Micra recipients stratified by whether or not they were precluded for therapy with TVP.

Methods

Micra patients from the Micra Transcatheter Pacing (IDE) Study, Continued Access (CA) study, and Post-Approval Registry (PAR) were divided into groups based upon whether or not the implanting physician considered the patient to be precluded from receiving a transvenous pacing system. All-cause mortality was compared between the Micra patient groups and patients receiving a single-chamber transvenous pacing system (SC-TVP) since 2010 from the Medtronic product surveillance registry using univariate and multivariate Cox models.

Results

Among 2,819 patients who underwent a Micra implant attempt, the overall major complication rate through 24 months was 3.5%. In these patients, 548 were deemed precluded from TVP implantation. Prior device infection or bacteremia (38.9%), venous access issues (36.1%) and thrombosis (10.2%) were amongst the most common causes of preclusion for TVP implantation. These patients were younger (71.7 vs. 76.7 years), more frequently on hemodialysis (26.3% vs. 2.5%), and more often had a prior CIED implanted (38.4% vs. 4.4%) than non-precluded patients. Over an average follow-up of 13.5±11.1 months, all-cause mortality was significantly higher in precluded Micra patients compared with SC-TVP patients (HR: 2.16, 95% CI: 1.54–3.2, P<0.001) (Figure 1). However, there was no significant difference in all-cause mortality when comparing non-precluded Micra patients and SC-TVP patients (HR: 1.12, 95% CI: 0.86–1.44, P=0.401). Acute all-cause death (within 1 month) among Micra patients was 2.74% and 1.32% in the precluded and non-precluded TVP groups, respectively. The procedure-related death rate was 0.55% for the TVP precluded group and 0.13% for the not precluded group (P=0.092). The major complication rate through 24-months was similar between the two Micra groups (4.0% vs 3.4%, P=0.630).

All-cause mortality for Micra and SC-TVP

Conclusion

The overall safety profile of Micra remains is in line with previously reported data. All-cause mortality risk (both acute and long term) appears to be higher in patients who were precluded from receiving TVP.

Acknowledgement/Funding

Supported by Medtronic

Safety of in-hospital insertable cardiac monitor procedures performed outside the traditional settings: results from the Reveal LINQ in-office 2 international study

Background

Historically, the majority of insertable cardiac monitor (ICM) procedures were performed in the cardiac catheterization (cath) lab, electrophysiology (EP) lab, or operating room (OR). The miniaturization of ICMs allows the procedure to be relocated within the hospital without compromising patient safety. We sought to estimate the rate of untoward events associated with procedures performed within the hospital but outside the traditional settings and to characterize resource utilization, procedure time intervals, and physician experience.

Methods

The Reveal LINQ in-Office 2 (RIO 2) International study was a single arm, multicenter, prospective study. Patients indicated for an ICM and willing to undergo device insertion outside the cath/EP lab or OR were eligible and followed for 90 days after insertion.

Results

A total of 191 patients (45.5% female aged 63.8 ± 26.9 years) underwent successful Reveal LINQ ICM insertion at 17 centers in Europe, Canada and Australia. The median total visit duration was 106 min (interquartile range [IQR]: 55–61). Patient preparation and patient education accounted for 10 min (IQR: 5–20) and 10 min (IQR: 8–15) of total visit duration, respectively. Preparation and education occurred in the procedure room for 90.6 and 60.2% of patients, respectively. There were no untoward events (0.0, 95% CI: 0.0–2.1%) though four patients presented with procedure-related adverse events that did not require invasive intervention. Physicians rated procedure location as convenient or very convenient.

Conclusions

The Reveal LINQ™ ICM insertion can be safely and efficiently performed in the hospital outside the cath/EP lab or OR.

Trial registration

ClinicalTrials.gov identifier NCT02412488; registered on April 9, 2015.

Electronic supplementary material

The online version of this article (10.1186/s12872-019-1106-3) contains supplementary material, which is available to authorized users.

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.

Accelerometer-based atrioventricular synchronous pacing with a ventricular leadless pacemaker: Results from the Micra atrioventricular feasibility studies

BACKGROUND

Micra is a leadless pacemaker that is implanted in the right ventricle and provides rate response via a 3-axis accelerometer (ACC). Custom software was developed to detect atrial contraction using the ACC enabling atrioventricular (AV) synchronous pacing.

OBJECTIVE

The purpose of this study was to sense atrial contractions from the Micra ACC signal and provide AV synchronous pacing.

METHODS

The Micra Accelerometer Sensor Sub-Study (MASS) and MASS2 early feasibility studies showed intracardiac accelerations related to atrial contraction can be measured via ACC in the Micra leadless pacemaker. The Micra Atrial TRacking Using A Ventricular AccELerometer (MARVEL) study was a prospective multicenter study designed to characterize the closed-loop performance of an AV synchronous algorithm downloaded into previously implanted Micra devices. Atrioventricular synchrony (AVS) was measured during 30 minutes of rest and during VVI pacing. AVS was defined as a P wave visible on surface ECG followed by a ventricular event <300 ms.

RESULTS

A total of 64 patients completed the MARVEL study procedure at 12 centers in 9 countries. Patients were implanted with a Micra for a median of 6.0 months (range 0-41.4). High-degree AV block was present in 33 patients, whereas 31 had predominantly intrinsic conduction during the study. Average AVS during AV algorithm pacing was 87.0% (95% confidence interval 81.8%-90.9%), 80.0% in high-degree block patients and 94.4% in patients with intrinsic conduction. AVS was significantly greater (P <.001) during AV algorithm pacing compared to VVI in high-degree block patients, whereas AVS was maintained in patients with intrinsic conduction.

CONCLUSION

Accelerometer-based atrial sensing is feasible and significantly improves AVS in patients with AV block and a single-chamber leadless pacemaker implanted in the right ventricle.

Impact of operator experience and training strategy on procedural outcomes with leadless pacing: Insights from the Micra Transcatheter Pacing Study

BACKGROUND

Leadless pacemaker systems have been designed to avoid the need for a pocket and transvenous lead. However, delivery of this therapy requires a new catheter-based procedure. This study evaluates the role of operator experience and different training strategies on procedural outcomes.

METHODS

A total of 726 patients underwent implant attempt with the Micra transcatheter pacing system (TPS; Medtronic, Minneapolis, MN, USA) by 94 operators trained in a teaching laboratory using a simulator, cadaver, and large animal models (lab training) or locally at the hospital with simulator/demo model and proctorship (hospital training). Procedure success, procedure duration, fluoroscopy time, and safety outcomes were compared between training methods and experience (implant case number).

RESULTS

The Micra TPS procedure was successful in 99.2% of attempts and did not differ between the 55 operators trained in the lab setting and the 39 operators trained locally at the hospital (P = 0.189). Implant case number was also not a determinant of procedural success (P = 0.456). Each operator performed between one and 55 procedures. Procedure time and fluoroscopy duration decreased by 2.0% (P = 0.002) and 3.2% (P < 0.001) compared to the previous case. Major complication rate and pericardial effusion rate were not associated with case number (P = 0.755 and P = 0.620, respectively). There were no differences in the safety outcomes by training method.

CONCLUSIONS

Among a large group of operators, implantation success was high regardless of experience. While procedure duration and fluoroscopy times decreased with implant number, complications were low and not associated with case number. Procedure and safety outcomes were similar between distinct training methodologies.

Worldwide Randomized Antibiotic EnveloPe Infection PrevenTion Trial (WRAP-IT)

BACKGROUND

Cardiac implantable electronic device (CIED) infection is a major complication that is associated with significant morbidity and mortality. The aim of this study is to determine whether Medtronic TYRX absorbable envelope reduces the risk of CIED infection through 12 months of follow-up post procedure.

METHODS

WRAP-IT is a randomized, prospective, multi center, international, single-blinded study. Up to 7,764 subjects who are undergoing CIED generator replacement, upgrade, or revision, or a de novo CRT-D implant, will be enrolled and randomized (1:1) to receive the TYRX envelope or not. The primary endpoint is major CIED infection throughout 12 months of follow up after the procedure. Data will be analyzed with an intention to treat approach. WRAP-IT will also assess the performance of Medtronic's lead monitoring algorithms in subjects whose CIED includes a transvenous right ventricular defibrillation system.

CONCLUSIONS

WRAP-IT is a large randomized clinical trial that will assess the efficacy of TYRX absorbable envelope in reducing CIED infection, define its cost effectiveness, and will also provide a unique opportunity to better understand the pathophysiology and risk factors for CIED infection.

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.).

Early performance of a miniaturized leadless cardiac pacemaker: the Micra Transcatheter Pacing Study

AIMS

Permanent cardiac pacing is the only effective treatment for symptomatic bradycardia, but complications associated with conventional transvenous pacing systems are commonly related to the pacing lead and pocket. We describe the early performance of a novel self-contained miniaturized pacemaker.

METHODS AND RESULTS

Patients having Class I or II indication for VVI pacing underwent implantation of a Micra transcatheter pacing system, from the femoral vein and fixated in the right ventricle using four protractible nitinol tines. Prespecified objectives were >85% freedom from unanticipated serious adverse device events (safety) and <2 V 3-month mean pacing capture threshold at 0.24 ms pulse width (efficacy). Patients were implanted (n = 140) from 23 centres in 11 countries (61% male, age 77.0 ± 10.2 years) for atrioventricular block (66%) or sinus node dysfunction (29%) indications. During mean follow-up of 1.9 ± 1.8 months, the safety endpoint was met with no unanticipated serious adverse device events. Thirty adverse events related to the system or procedure occurred, mostly due to transient dysrhythmias or femoral access complications. One pericardial effusion without tamponade occurred after 18 device deployments. In 60 patients followed to 3 months, mean pacing threshold was 0.51 ± 0.22 V, and no threshold was ≥2 V, meeting the efficacy endpoint (P < 0.001). Average R-wave was 16.1 ± 5.2 mV and impedance was 650.7 ± 130 ohms.

CONCLUSION

Early assessment shows the transcatheter pacemaker can safely and effectively be applied. Long-term safety and benefit of the pacemaker will further be evaluated in the trial.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov ID NCT02004873.