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.

Regional variations in patient selection and procedural characteristics for cryoballoon ablation of atrial fibrillation in the cryo global registry.

BACKGROUND: Cryoballoon ablation is a well-established anatomical approach for pulmonary vein isolation (PVI) in patients with atrial fibrillation (AF). Although widely adopted, regional variations in standards of care have not been well characterized. METHODS: Patients with AF were enrolled in the Cryo Global Registry (NCT02752737) from May 2016 to Sept 2021 at 128 sites in 37 countries and treated with cryoballoon ablation according to local clinical practice. Baseline patient and procedural characteristics were summarized for 8 regions (Central Asia & Russia, East Asia, Europe, Middle East, North America, South Africa, South America, and Southeast Asia). Serious procedure-related adverse events (SAEs) were evaluated in a subset of patients with ≥ 7 days of follow-up. RESULTS: A total of 3,680 patients undergoing initial PVI for AF were included. Cryoballoon ablation was commonly performed in patients with paroxysmal AF. Mean age ranged from 47 ± 12 years in the Middle East to 64 ± 11 years in East Asia. Mean procedure time was ≤ 95 min in all regions. Average freeze duration ranged from 153 ± 41 s in Southeast Asia to 230 ± 29 s in Central Asia & Russia. Acute procedural success was ≥ 94.7% in all geographies. In 3,126 subjects with ≥ 7 days of follow-up, 122 procedure-related SAEs were reported in 111 patients (3.6%) and remained low in all regions. One procedure-related death was reported during data collection. CONCLUSIONS: Despite regional variations in patient selection and procedural characteristics, PVI using cryoballoon ablation was performed with high acute success and short procedural times around the world. CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/ct2/show/NCT02752737.

Global LEADR pivotal trial results.

BACKGROUND: Implantable cardioverter-defibrillators last longer, and interest in reliable leads with targeted lead placement is growing. The OmniaSecure™ defibrillation lead is a novel small-diameter, catheter-delivered lead designed for targeted placement, based on the established SelectSecure SureScan MRI Model 3830 lumenless pacing lead platform. OBJECTIVE: This trial assessed safety and efficacy of the OmniaSecure defibrillation lead. METHODS: The worldwide LEADR pivotal clinical trial enrolled patients indicated for de novo implantation of a primary or secondary prevention implantable cardioverter-defibrillator/cardiac resynchronization therapy defibrillator, all of whom received the study lead. The primary efficacy end point was successful defibrillation at implantation per protocol. The primary safety end point was freedom from study lead-related major complications at 6 months. The primary efficacy and safety objectives were met if the lower bound of the 2-sided 95% credible interval was >88% and >90%, respectively. RESULTS: In total, 643 patients successfully received the study lead, and 505 patients have completed 12-month follow-up. The lead was placed in the desired right ventricular location in 99.5% of patients. Defibrillation testing at implantation was completed in 119 patients, with success in 97.5%. The Kaplan-Meier estimated freedom from study lead-related major complications was 97.1% at 6 and 12 months. The trial exceeded the primary efficacy and safety objective thresholds. There were zero study lead fractures and electrical performance was stable throughout the mean follow-up of 12.7 ± 4.8 months (mean ± SD). CONCLUSION: The OmniaSecure lead exceeded prespecified primary end point performance goals for safety and efficacy, demonstrating high defibrillation success and a low occurrence of lead-related major complications with zero lead fractures.

Impact of first-line cryoablation for atrial fibrillation on healthcare utilization, arrhythmia disease burden and efficacy outcomes: real-world evidence from the Cryo Global Registry.

BACKGROUND: Cryoballoon ablation (CBA) is an effective first-line treatment for symptomatic atrial fibrillation (AF), as recently demonstrated by three randomized trials. This sub-analysis of the Cryo Global Registry aims to examine current clinical practices of first-line CBA. METHODS: AF patients treated with first-line CBA were compared to CBA in antiarrhythmic drug (AAD)-refractory patients at 12 months. Efficacy was examined using time-to-first atrial arrhythmia recurrence following a 90-day blanking period. Healthcare utilization was evaluated by repeat ablations and hospitalizations. Disease burden was examined by assessing quality of life (QOL) and patients' reporting of symptoms. RESULTS: Of 1394 patients, 433 (31.1%) were treated with first-line CBA, which was more frequent in high-volume centers. Serious procedure-related adverse event rates were similar. Efficacy at 12 months was higher in the first-line group (87.8 vs. 81.6%, HRunadj 0.64 (95% CI 0.47-0.88); p < 0.01) regardless of the centers' CBA experience; when controlling for baseline characteristics, the difference was not significant (HRadj 0.87 (95% CI 0.56-1.37); p = 0.55). No difference was observed in repeat ablations and hospitalizations between cohorts. First-line patients experienced a larger mean reduction in symptoms and were prescribed AADs at a lower rate at 12-month follow-up (9.7 vs. 29.9%). QOL improved in both cohorts from baseline to 12 months with no significant difference between groups (p = 0.29). CONCLUSIONS: In this global real-world experience, first-line CBA in patients with symptomatic AF is effective, with a larger symptom reduction compared with CBA after AAD failure and without a difference in healthcare utilization at mid-term follow-up. CLINICAL TRIAL REGISTRATION: https://clinicaltrials.gov/ct2/show/NCT02752737.

Cryoballoon Ablation for the Treatment of Atrial Fibrillation in Patients With Concomitant Heart Failure and Either Reduced or Preserved Left Ventricular Ejection Fraction: Results From the Cryo AF Global Registry.

Background Heart failure (HF) and atrial fibrillation (AF) often coexist; yet, outcomes of ablation in patients with AF and concomitant HF are limited. This analysis assessed outcomes of cryoablation in patients with AF and HF. Methods and Results The Cryo AF Global Registry is a prospective, multicenter registry of patients with AF who were treated with cryoballoon ablation according to routine practice at 56 sites in 26 countries. Patients with baseline New York Heart Association class I to III (HF cohort) were compared with patients without HF. Freedom from atrial arrhythmia recurrence ≥30 seconds, safety, and health care utilization over 12-month follow-up were analyzed. A total of 1303 patients (318 HF) were included. Patients with HF commonly had preserved left ventricular ejection fraction (81.6%), were more often women (45.6% versus 33.6%) with persistent AF (25.8% versus 14.3%), and had a larger left atrial diameter (4.4±0.9 versus 4.0±0.7 cm). Serious procedure-related complications occurred in 4.1% of patients with HF and 2.6% of patients without HF (P=0.188). Freedom from atrial arrhythmia recurrence was not different between cohorts with either paroxysmal AF (84.2% [95% CI, 78.6-88.4] versus 86.8% [95% CI, 84.2-89.0]) or persistent AF (69.6% [95% CI, 58.1-78.5] versus 71.8% [95% CI, 63.2-78.7]) (P=0.319). After ablation, a reduction in AF-related symptoms and antiarrhythmic drug use was observed in both cohorts (HF and no-HF), and freedom from repeat ablation was not different between cohorts. Persistent AF and HF predicted a post-ablation cardiovascular rehospitalization (P=0.032 and P=0.001, respectively). Conclusions Cryoablation to treat patients with AF is similarly effective at 12 months in patients with and without HF. Registration URL: https://www.clinicaltrials.gov; Unique Identifier: NCT02752737.

Predictors of atrial mechanical sensing and atrioventricular synchrony with a leadless ventricular pacemaker: Results from the MARVEL 2 Study.

BACKGROUND: The MARVEL (Micra Atrial TRacking Using a Ventricular AccELerometer) 2 study assessed the efficacy of atrioventricular (AV) synchronous pacing with a Micra leadless pacemaker. Average atrioventricular synchrony (AVS) was 89.2%. Previously, low amplitude of the Micra-sensed atrial signal (A4) was observed to be a factor of low AVS. OBJECTIVE: The purpose of this study was to identify predictors of A4 amplitude and high AVS. METHODS: We analyzed 64 patients enrolled in MARVEL 2 who had visible P waves on electrocardiogram for assessing A4 amplitude and 40 patients with third-degree AV block for assessing AVS at rest. High AVS was defined as >90% correct atrial-triggered ventricular pacing. The association between clinical factors and echocardiographic parameters with A4 amplitude was investigated using a multivariable model with lasso variable selection. Variables associated with A4 amplitude together with premature ventricular contraction burden, sinus rate, and sinus rate variability (standard deviation of successive differences of P-P intervals [SDSD]) were assessed for association with AVS. RESULTS: In univariate analysis, low A4 amplitude was inversely related to atrial function assessed by E/A ratio and e'/a' ratio, and was directly related to atrial contraction excursion (ACE) and atrial strain (Ɛa) on echocardiography (all P ≤.05). The multivariable lasso regression model found coronary artery bypass graft history, E/A ratio, ACE, and Ɛa were associated with low A4 amplitude. E/A ratio and SDSD were multivariable predictors of high AVS, with >90% probability if E/A <0.94 and SDSD <5 bpm. CONCLUSION: Clinical parameters and echocardiographic markers of atrial function are associated with A4 signal amplitude. High AVS can be predicted by E/A ratio <0.94 and low sinus rate variability at rest.

Atrioventricular Synchronous Pacing Using a Leadless Ventricular Pacemaker: Results From the MARVEL 2 Study.

OBJECTIVES: This study reports on the performance of a leadless ventricular pacemaker with automated, enhanced accelerometer-based algorithms that provide atrioventricular (AV) synchronous pacing. BACKGROUND: Despite many advantages, leadless pacemakers are currently only capable of single-chamber ventricular pacing. METHODS: The prospective MARVEL 2 (Micra Atrial tRacking using a Ventricular accELerometer 2) study assessed the performance of an automated, enhanced accelerometer-based algorithm downloaded to the Micra leadless pacemaker for up to 5 h in patients with AV block. The primary efficacy objective was to demonstrate the superiority of the algorithm to provide AV synchronous (VDD) pacing versus VVI-50 pacing in patients with sinus rhythm and complete AV block. The primary safety objective was to demonstrate that the algorithm did not result in pauses or heart rates of >100 beats/min. RESULTS: Overall, 75 patients from 12 centers were enrolled; an accelerometer-based algorithm was downloaded to their leadless pacemakers. Among the 40 patients with sinus rhythm and complete AV block included in the primary efficacy objective analysis, the proportion of patients with ≥70% AV synchrony at rest was significantly greater with VDD pacing than with VVI pacing (95% vs. 0%; p < 0.001). The mean percentage of AV synchrony increased from 26.8% (median: 26.9%) during VVI pacing to 89.2% (median: 94.3%) during VDD pacing. There were no pauses or episodes of oversensing-induced tachycardia reported during VDD pacing in all 75 patients. CONCLUSIONS: Accelerometer-based atrial sensing with an automated, enhanced algorithm significantly improved AV synchrony in patients with sinus rhythm and AV block who were implanted with a leadless ventricular pacemaker. (Micra Atrial Tracking Using a Ventricular Accelerometer 2 [MARVEL 2]; NCT03752151).

The World-wide Randomized Antibiotic Envelope Infection Prevention (WRAP-IT) trial: Long-term follow-up.

BACKGROUND: The World-wide Randomized Antibiotic Envelope Infection Prevention trial reported a 40% reduction in major cardiac implantable electronic device (CIED) infections within 12 months of the procedure with the use of an antibacterial-eluting envelope (TYRX Absorbable Antibacterial Envelope, Medtronic, Mounds View, MN). OBJECTIVE: The purpose of this report was to describe the longer-term (>12 months) envelope effects on infection reduction and complications. METHODS: All trial patients who underwent CIED replacement, upgrade, revision, or initial cardiac resynchronization therapy - defibrillator implantation received standard-of-care infection prophylaxis and were randomized in a 1:1 ratio to receive the envelope or not. CIED infection incidence and procedure and system-related complications were characterized through all follow-up (36 months) by using Cox proportional hazards regression modeling. RESULTS: In total, 6800 patients received their intended randomized treatment (3371 envelope; 3429 control; mean follow-up period 21.0 ± 8.3 months). Major CIED-related infections occurred in 32 envelope patients and 51 control patients (Kaplan-Meier [KM] estimate 1.3% vs 1.9%; hazard ratio [HR] 0.64; 95% confidence interval [CI] 0.41-0.99; P = .046). Any CIED-related infection occurred in 57 envelope patients and 84 control patients (KM estimate 2.1% vs 2.8%; HR 0.69; 95% CI 0.49-0.97; P = .030). System- or procedure-related complications occurred in 235 envelope patients and 252 control patients (KM estimate 8.0% vs 8.2%; HR 0.95; 95% CI 0.79-1.13; P < .001 for noninferiority); the most common were lead dislodgment (1.1%), device lead damage (0.5%), and implant site hematoma (0.4%). Implant site pain occurred less frequently in the envelope group (0.1% vs 0.4%; P = .067). There were no (0.0%) reports of allergic reactions to the components of the envelope (mesh, polymer, or antibiotics). CONCLUSION: The effects of the TYRX envelope on the reduction of the risk of CIED infection are sustained beyond the first year postprocedure, without an increased risk of complications.

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.

Beta-blocker use and risk of symptomatic bradyarrhythmias: a hospital-based case-control study.

OBJECTIVE: To investigate the risk factors of symptomatic bradyarrhythmias in relation to ß-blockers use. METHODS: A hospital-based case-control study [228 patients: 108 with symptomatic bradyarrhythmias (cases) and 120 controls] was conducted in Sultanah Aminah Hospital, Malaysia between January 2011 and January 2014. RESULTS: The mean age was 61.1 ± 13.3 years with a majority of men (68.9%). Cases were likely than control to be older, hypertensive, lower body mass index and concomitant use of rate-controlling drugs (such as digoxin, verapamil, diltiazem, ivabradine or amiodarone). Significantly higher level of serum potassium, urea, creatinine and lower level of estimated glomerular filtration rate (eGFR) were observed among cases as compared to controls. On univariate analysis among patients on ß-blockers, older age (crude OR: 1.07; 95% CI: 1.03-1.11, P = 0.000), hypertension (crude OR: 5.6; 95% CI: 1.51-20.72, P = 0.010), lower sodium (crude OR: 0.04; 95% CI: 0.81-0.99, P = 0.036), higher potassium (crude OR: 2.36; 95% CI: 1.31-4.26, P = 0.004) and higher urea (crude OR: 1.23; 95% CI: 1.11-1.38, P = 0.000) were associated with increased risk of symptomatic bradyarrhythmias; eGFR was inversely and significantly associated with symptomatic bradyarrhythmias in both 'ß-blockers' (crude OR: 0.97; 95% CI: 0.96-0.98, P = 0.000) and 'non-ß-blockers' (crude OR: 0.99; 95% CI: 0.97-0.99, P = 0.023) arms. However, eGFR was not significantly associated with symptomatic bradyarrhythmias in the final model of both 'ß-blockers' (adjusted OR: 0.98; 95% CI: 0.96-0.98, P = 0.103) and 'non-ß-blockers' (adjusted OR: 0.99; 95% CI: 0.97-1.01, P = 0.328) arms. Importantly, older age was a significant predictor of symptomatic bradyarrhythmias in the 'ß-blockers' as compared to the 'non-ß-blockers' arms (adjusted OR: 1.09; 95% CI: 1.03-1.15, P = 0.003 vs. adjusted OR: 1.03; 95% CI: 0.98-1.09, P = 0.232, respectively). CONCLUSION: Older age was a significant predictor of symptomatic bradyarrhythmias in patients on ß-blockers than those without ß-blockers.