Early performance of the Micra transcatheter pacemaker from the global clinical trial reported a 99.2% implant success rate, low and stable pacing capture thresholds, and a low (4.0%) rate of major ...complications up to 6 months.
The purpose of this report was to describe the prespecified long-term safety objective of Micra at 12 months and electrical performance through 24 months.
The Micra Transcatheter Pacing Study was a prospective single-arm study designed to assess the safety and efficacy of the Micra VVIR leadless/intracardiac pacemaker. Enrolled patients met class I or II guideline recommendations for de novo ventricular pacing. The long-term safety objective was freedom from a system- or procedure-related major complication at 12 months. A predefined historical control group of 2667 patients with transvenous pacemakers was used to compare major complication rates.
The long-term safety objective was achieved with a freedom from major complication rate of 96.0% at 12 months (95% confidence interval 94.2%–97.2%; P < .0001 vs performance goal). The risk of major complications for patients with Micra (N = 726) was 48% lower than that for patients with transvenous systems through 12 months postimplant (hazard ratio 0.52; 95% confidence interval 0.35–0.77; P = .001). Across subgroups of age, sex, and comorbidities, Micra reduced the risk of major complications compared to transvenous systems. Electrical performance was excellent through 24 months, with a projected battery longevity of 12.1 years.
Long-term performance of the Micra transcatheter pacemaker remains consistent with previously reported data. Few patients experienced major complications through 12 months of follow-up, and all patient subgroups benefited as compared to transvenous pacemaker historical control group.
BACKGROUND—Specific noninvasive signal processing was applied to identify drivers in distinct categories of persistent atrial fibrillation (AF).
METHODS AND RESULTS—In 103 consecutive patients with ...persistent AF, accurate biatrial geometry relative to an array of 252 body surface electrodes was obtained from a noncontrast computed tomography scan. The reconstructed unipolar AF electrograms acquired at bedside from multiple windows (duration, 9±1 s) were signal processed to identify the drivers (focal or reentrant activity) and their cumulative density map. The driver domains were catheter ablated by using AF termination as the procedural end point in comparison with the stepwise-ablation control group. The maps showed incessantly changing beat-to-beat wave fronts and varying spatiotemporal behavior of driver activities. Reentries were not sustained (median, 2.6 rotations lasting 449±89 ms), meandered substantially but recurred repetitively in the same region. In total, 4720 drivers were identified in 103 patients3802 (80.5%) reentries and 918 (19.5%) focal breakthroughs; most of them colocalized. Of these, 69% reentries and 71% foci were in the left atrium. Driver ablation alone terminated 75% and 15% of persistent and long-lasting AF, respectively. The number of targeted driver regions increased with the duration of continuous AF2 in patients presenting in sinus rhythm, 3 in AF lasting 1 to 3 months, 4 in AF lasting 4 to 6 months, and 6 in AF lasting longer. The termination rate sharply declined after 6 months. The mean radiofrequency delivery to AF termination was 28±17 minutes versus 65±33 minutes in the control group (P<0.0001). At 12 months, 85% patients with AF termination were free from AF, similar to the control population (87%,); P=not significant.
CONCLUSIONS—Persistent AF in early months is maintained predominantly by drivers clustered in a few regions, most of them being unstable reentries.
Early results of the Micra Investigational Device Exemption (IDE) study and Micra Post-Approval Registry (PAR) demonstrated excellent safety and efficacy performance; however, intermediate-term ...results across a large patient population in the real-world setting have not been evaluated.
We report updated performance of the Micra transcatheter pacemaker from a worldwide PAR and compare it with the IDE study as well as a transvenous historical control.
The safety objective of the analysis was system- or procedure-related major complications through 12 months postimplantation. We compared the major complication rate with that of the 726 patients from the IDE and with a reference data set of 2667 patients with transvenous pacemakers by using a Fine-Gray competing risk model.
The Micra device was successfully implanted in 1801 of 1817 patients (99.1%). The mean follow-up period was 6.8 ± 6.9 months. Through 12 months, the major complication rate was 2.7% (95% confidence interval CI 2.0%–3.7%). The risk of major complications for Micra PAR patients was 63% lower than that for patients with transvenous pacemakers through 12 months postimplantation (hazard ratio 0.37; 95% CI 0.27–0.52; P < .001). The major complication rate trended lower in the PAR than in the IDE study (hazard ratio 0.71; 95% CI 0.44–1.1; P = .160), driven by the lower pericardial effusion rate in the PAR. There were 3 cases of infection associated with the procedure, but none required device removal and there were no battery or telemetry issues. Pacing thresholds were low and stable through 12 months postimplantation.
Performance of the Micra transcatheter pacemaker in international clinical practice remains consistent with previously reported data. Major complications were infrequent and occurred 63% less often compared to transvenous systems.
Micra Transcatheter Pacing System Post-Approval Registry ClinicalTrials.gov identifier: NCT02536118; Micra Transcatheter Pacing Study ClinicalTrials.gov identifier: NCT02004873.
Biventricular pacing (BVP) may not achieve complete electrical resynchronization.
The purpose of this study was to assess whether the resynchronizing effect of BVP varies among patients depending on ...the underlying electrical substrate.
High-resolution electrocardiographic mapping with invasive measurement of the maximal rate of systolic left ventricular (LV) pressure rise (LVdP/dtmax) was performed during baseline activation and during BVP in 61 patients with heart failure with various conduction delays: 13 with narrow QRS duration (<120 ms), 22 with nonspecific intraventricular conduction disturbance, and 26 with left bundle branch block. Electrical dyssynchrony, both during baseline activation and BVP, was quantified by total and LV activation times (TAT and LVTAT) and by ventricular electrical uncoupling (VEU = mean LVTAT - mean right ventricular activation time). Response to BVP was defined as a ≥10% increase in LVdP/dtmax.
The electrical activation pattern during BVP was similar for all patient groups and, hence, not dependent on baseline conduction disturbance. During BVP, TAT, LVTAT, and VEU were similar for all groups and were either not correlated or weakly correlated with the change in LVdP/dtmax. In contrast, changes in electrical dyssynchrony correlated significantly with the change in LVdP/dtmax: r=0.71, 0.69, and 0.69 for ∆TAT, ∆LVTAT, and ∆VEU, respectively (all P < .001). Responders showed higher baseline dyssynchrony levels and BVP-induced dyssynchrony reduction than did nonresponders (all P < .001); in nonresponders, BVP worsened activation times than did baseline activation.
BVP does not eliminate electrical dyssynchrony, but rather brings it to a common level independent of the patient's underlying electrical substrate. Therefore, BVP is of benefit to patients with dyssynchrony but not to patients with insufficient electrical dyssynchrony in whom it induces an iatrogenic electropathy.
New-onset left bundle branch block (LBBB) is a specific concern of transcutaneous aortic valve implantation (TAVI) given its estimated incidence ranging from 5% to 65%. This high rate of occurrence ...is dependent on the type of device used (size and shape), implantation methods, and patient co-morbidities. The appearance of an LBBB after TAVI reflects a very proximal lesion of the left bundle branch as it exits the bundle of His. At times transient, its persistence can lead to permanent pacemaker implantation in 15% to 20% of cases, most often for high-degree atrioventricular block. The management of LBBB after TAVI is currently not defined by international societies resulting in individual centers developing their own management strategy. The potential consequences of LBBB are dysrhythmias (atrioventricular block, syncope, and sudden death) and functional (heart failure) complications. Prompt postprocedural recognition and management (permanent pacemaker implantation) of patients prevents the occurrence of potential complications and may constitute the preferred approach in this frail and elderly population despite additional costs and complications of cardiac pacing. Moreover, the expansion of future indications for TAVI necessitates better identification of the predictive factors for the development of LBBB. Indeed, long-term right ventricular pacing may potentially increase the risk of developing heart failure in this population. In conclusion, it is thus imperative to not only develop new aortic prostheses with a less-deleterious impact on the conduction system but also to prescribe appropriate pacing modes in this frail population.
Background
QRS narrowing following cardiac resynchronization therapy with biventricular (BiV) or left ventricular (LV) pacing is likely affected by patient‐specific conduction characteristics (PR, ...qLV, LV‐paced propagation interval), making a universal programming strategy likely ineffective. We tested these factors using a novel, device‐based algorithm (SyncAV) that automatically adjusts paced atrioventricular delay (default or programmable offset) according to intrinsic atrioventricular conduction.
Methods and Results
Seventy‐five patients undergoing cardiac resynchronization therapy (age 66±11 years; 65% male; 32% with ischemic cardiomyopathy; LV ejection fraction 28±8%; QRS duration 162±16 ms) with intact atrioventricular conduction (PR interval 194±34, range 128–300 ms), left bundle branch block, and optimized LV lead position were studied at implant. QRS duration (QRSd) reduction was compared for the following pacing configurations: nominal simultaneous BiV (Mode I: paced/sensed atrioventricular delay=140/110 ms), BiV+SyncAV with 50 ms offset (Mode II), BiV+SyncAV with offset that minimized QRSd (Mode III), or LV‐only pacing+SyncAV with 50 ms offset (Mode IV). The intrinsic QRSd (162±16 ms) was reduced to 142±17 ms (−11.8%) by Mode I, 136±14 ms (−15.6%) by Mode IV, and 132±13 ms (−17.8%) by Mode II. Mode III yielded the shortest overall QRSd (123±12 ms, −23.9% P<0.001 versus all modes) and was the only configuration without QRSd prolongation in any patient. QRS narrowing occurred regardless of QRSd, PR, or LV‐paced intervals, or underlying ischemic disease.
Conclusions
Post‐implant electrical optimization in already well‐selected patients with left bundle branch block and optimized LV lead position is facilitated by patient‐tailored BiV pacing adjusted to intrinsic atrioventricular timing using an automatic device–based algorithm.
Background:Frequency and distribution of left ventricular (LV) venous collaterals were studied in vivo to evaluate the ease and feasibility of implanting a new ultra-thin LV quadripolar microlead for ...cardiac resynchronization therapy (CRT).Methods and Results:Evaluable venograms were analyzed to define the prevalence of venous collaterals (>0.5 mm diameter) between: (1) different LV segments; and (2) different major LV veins in: unselected patients who underwent CRT from 2008 to 2012 at Rouen Hospital, France (retrospective); and CRT patients from the Axone Acute pilot study in 2018 (prospective). In prospective patients with evaluable venograms, LV microlead implantation was attempted. Thirty-six (21/65 retrospective, 15/20 prospective) patients had evaluable venograms with ≥1 visible venous collaterals. Collaterals were found between LV veins in all CRT patients with evaluable venograms. Regionally, prevalence was highest between: the apical inferior and apical lateral (42%); and mid inferior and mid inferolateral (42%) segments. Collateral connections were most prevalent between: the inferior interventricular vein (IIV) and lateral vein (64% 23/36); and IIV and infero-lateral vein (36% 13/36). Cross-vein microlead implantation was possible in 18 patients (90%), and single-vein implantation was conducted in the other 2 patients (10%).Conclusions:Venous collaterals were found in vivo between LV veins in all CRT patients with evaluable venograms, making this network an option for accessing multiple LV sites using a single LV microlead.
Subcutaneous implantable cardioverter-defibrillator (S-ICD) implantations are rapidly expanding. However, the subcutaneous detection and interpretation of cardiac signals in S-ICDs is much more ...challenging than by conventional devices. There is a complete paradigm shift in cardiac signal sensing with subcutaneous signal detection, leading in some cases to oversensing with restricted programming options.
The aim of this single-center study was to quantify and describe cases where recurring oversensing made the extraction of the device necessary.
Consecutive patients (n = 108) implanted with an S-ICD in our tertiary referral hospital were considered for analysis. Clinical and remote monitoring data were analyzed.
The S-ICD had to be explanted in 6 of 108 implanted patients (5.6%) because of refractory oversensing issues: myopotential oversensing, P- or T-wave oversensing, rate-dependent left bundle branch block aberrancy during exercise with R-wave double counting, and R-wave amplitude decrease after ventricular tachycardia ablation leading to noise detection. Seventeen of 108 patients experienced oversensing (15.7%): 9 patients had at least 1 inappropriate charge without a shock (8.3%), 3 patients had at least 1 inappropriate shock (2.8%), and 5 patients had both episodes (4.6%).
So far, cardiologists have had to deal with transvenous ICD lead fractures, but signal oversensing without correcting programming option could be the equivalent weakness of S-ICDs, despite an adequate screening.
Introduction
Recognition of implantable cardioverter defibrillator (ICD) lead malfunction before occurrence of life threatening complications is crucial. We aimed to assess the effectiveness of ...remote monitoring associated or not with a lead noise alert for early detection of ICD lead failure.
Methods
From October 2013 to April 2017, a median of 1,224 (578–1,958) ICD patients were remotely monitored with comprehensive analysis of all transmitted materials. ICD lead failure and subsequent device interventions were prospectively collected in patients with (RMLN) and without (RM) a lead noise alert (Abbott Secure Sense™ or Medtronic Lead Integrity Alert™) in their remote monitoring system.
Results
During a follow‐up of 4,457 patient years, 64 lead failures were diagnosed. Sixty‐one (95%) of the diagnoses were made before any clinical complication occurred. Inappropriate shocks were delivered in only one patient of each group (3%), with an annual rate of 0.04%. All high voltage conductor failures were identified remotely by a dedicated impedance alert in 10 patients. Pace‐sense component failures were correctly identified by a dedicated alert in 77% (17 of 22) of the RMLN group versus 25% (8 of 32) of the RM group (P = 0.002). The absence of a lead noise alert was associated with a 16‐fold increase in the likelihood of initiating either a shock or ATP (OR: 16.0, 95% CI 1.8–143.3; P = 0.01).
Conclusion
ICD remote monitoring with systematic review of all transmitted data is associated with a very low rate of inappropriate shocks related to lead failure. Dedicated noise alerts further reduce inappropriate detection of ventricular arrhythmias.
Device repositioning during Micra leadless pacemaker implantation may be required to achieve optimal pacing thresholds.
The purpose of this study was to describe the natural history of acute elevated ...Micra vs traditional transvenous lead thresholds.
Micra study VVI patients with threshold data (at 0.24 ms) at implant (n = 711) were compared with Capture study patients with de novo transvenous leads at 0.4 ms (n = 538). In both cohorts, high thresholds were defined as >1.0 V and very high as >1.5 V. Change in pacing threshold (0–6 months) with high (1.0 to ≤1.5 V) or very high (>1.5 V) thresholds were compared using the Wilcoxon signed-rank test.
Of the 711 Micra patients, 83 (11.7%) had an implant threshold of >1.0 V at 0.24 ms. Of the 538 Capture patients, 50 (9.3%) had an implant threshold of >1.0 V at 0.40 ms. There were no significant differences in patient characteristics between those with and without an implant threshold of >1.0 V, with the exception of left ventricular ejection fraction in the Capture cohort (high vs low thresholds, 53% vs 58%; P = .011). Patients with an implant threshold of >1.0 V decreased significantly (P < .001) in both cohorts. Micra patients with high and very high thresholds decreased significantly (P < .01) by 1 month, with 87% and 85% having 6-month thresholds lower than the implant value. However, when the capture threshold at implant was >2 V, only 18.2% had a threshold of ≤1 V at 6 months and 45.5% had a capture threshold of >2 V.
Pacing thresholds in most Micra patients with elevated thresholds decrease after implant. Micra device repositioning may not be necessary if the pacing threshold is ≤2 V.
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