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Background: Impaired quality of life due to atrial fibrillation (AF), which often includes decreased activity level, is an indication for ablation. However, the impact of ablation for AF on activity is poorly understood., Objective: The purpose of this study was to assess the impact of ablation on activity minutes per day using continuous accelerometer data from cardiac implantable electronic devices (CIEDs)., Methods: Using the Optum® Health Record dataset (2007-2019) linked with the Medtronic CareLink® database, we identified patients who had a CIED with AF detection and accelerometer capabilities. Patients with a device that transmitted heart rhythm and activity data ≥3 months before and ≥12 months after ablation were included in analysis. The associations between ablation and activity minutes were assessed for each CIED type., Results: Of 4297 eligible patients who underwent AF ablation, 409 (9.5%) (65% male; age 67.3 ± 9.8 years; 64% paroxysmal AF) were included in analysis. The average AF burden and activity minutes per day preablation were 30.9% ± 37.4% and 175 ± 99 minutes, respectively. After ablation, relative AF burden decreased by 75.1% ± 53.2% (P <.001). There was no change in activity minutes per day after ablation in the entire cohort (average change -0.10 ± 36.2 minutes; P = .96). There were also no clinically significant changes in activity minutes postablation in subgroups based on CIED, season of ablation, quartile of AF burden change, and quartile of age at the time of ablation., Conclusion: There were no clinically significant changes in activity minutes per day in patients with CIEDs after ablation for AF., (Copyright © 2022 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Chronic anticoagulation is recommended for atrial fibrillation (AF) patients with thromboembolic risk factors regardless of AF duration/frequency. Continuous rhythm assessment with pacemakers (PMs)/implantable cardioverter-defibrillators (ICDs) and use of direct-acting oral anticoagulants (DOACs) may allow anticoagulation only around AF episodes, reducing bleeding without increasing thromboembolic risk., Objective: The purpose of this study was to evaluate the feasibility/safety of intermittent DOAC use guided by continuous remote AF monitoring via dual-chamber PMs or ICDs., Methods: Patients with nonpermanent AF, current DOAC use, CHADS 2 score ≤3, a St. Jude Medical dual-chamber PM or ICD, and rare AF episodes were followed with biweekly and AF-alert based remote transmissions. Patients free of AF episodes lasting ≥6 minutes with a total AF burden <6 hours/day for 30 consecutive days discontinued DOAC. If AF burden surpassed these limits, DOAC was restarted and/or continued. Total days on DOAC and adverse events were assessed., Results: Among 48 patients (mean age 71.3 years; 65% male; 79% paroxysmal AF; 87% CHADS 2 score 1-2), 14,826 days of monitoring were completed. Patients used DOACs for 3763 days, representing a 74.6% reduction in anticoagulation time compared to chronic administration. Adverse events included 2 gastrointestinal bleeds (both on DOAC), 1 fatal intracerebral bleed (off DOAC), and no thromboembolic/stroke events., Conclusion: Among patients with rare AF episodes and low-to-moderate stroke risk, PM/ICD-guided DOAC administration is feasible and decreased anticoagulation utilization by 75%. Few adverse events occurred, although the study was not powered to assess these outcomes. PM/ICD-guided DOAC administration may prove a viable alternative to chronic anticoagulation. Future studies are warranted., (Copyright © 2018 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Undersensing of premature ventricular beats and low-amplitude R waves are primary causes for inappropriate bradycardia and pause detections in insertable cardiac monitors (ICMs)., Objective: The purpose of this study was to develop and validate an enhanced algorithm to reduce inappropriately detected bradycardia and pause episodes., Methods: Independent data sets to develop and validate the enhanced algorithm were derived from a database of ICM-detected bradycardia and pause episodes in de-identified patients monitored for unexplained syncope. The original algorithm uses an auto-adjusting sensitivity threshold for R-wave sensing to detect tachycardia and avoid T-wave oversensing. In the enhanced algorithm, a second sensing threshold is used with a long blanking and fixed lower sensitivity threshold, looking for evidence of undersensed signals. Data reported includes percent change in appropriate and inappropriate bradycardia and pause detections as well as changes in episode detection sensitivity and positive predictive value with the enhanced algorithm., Results: The validation data set, from 663 consecutive patients, consisted of 4904 (161 patients) bradycardia and 2582 (133 patients) pause episodes, of which 2976 (61%) and 996 (39%) were appropriately detected bradycardia and pause episodes. The enhanced algorithm reduced inappropriate bradycardia and pause episodes by 95% and 47%, respectively, with 1.7% and 0.6% reduction in appropriate episodes, respectively. The average episode positive predictive value improved by 62% (P < .001) for bradycardia detection and by 26% (P < .001) for pause detection, with an average relative sensitivity of 95% (P < .001) and 99% (P = .5), respectively., Conclusion: The enhanced dual sense algorithm for bradycardia and pause detection in ICMs substantially reduced inappropriate episode detection with a minimal reduction in true episode detection., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Damage to extracardiac structures, including the esophagus and phrenic nerve, is a known complication of cryoballoon ablation (CBA) during pulmonary vein (PV) isolation for atrial fibrillation (AF). Other adjacent structures, including the pulmonary bronchi and lung parenchyma, may be affected during CBA at the PV ostia., Objective: The purpose of this study was to prospectively study the bronchial effects of CBA in humans undergoing CBA for PV isolation., Methods: Ten patients undergoing CBA for AF under general anesthesia were enrolled in an institutional review board-approved prospective observational study. Real-time bronchoscopy was performed during cryoablation of PVs adjacent to pulmonary bronchi to monitor for thermal injury. Patients were followed for the development of respiratory complaints postprocedure., Results: In 7 of 10 patients (70%) and in 13 of 22 freezes (59%), ice formation was visualized in the left mainstem bronchus during CBA in the left upper PV. Ice formation was not seen in the right mainstem bronchus during right upper PV CBA. The average time to ice formation was 89 seconds. There was no significant difference (P = -.45) in average minimum balloon temperature during freezes with ice formation (-48.5°C) and freezes without ice formation (-46.3°C). No patients went on to develop respiratory complications., Conclusion: Unrecognized ice formation occurs frequently in the left mainstem bronchus during CBA for AF. This information helps explain the source of cough and hemoptysis in some patients who undergo CBA. The long-term consequences of this novel finding and the implications for procedural safety are unknown., (Copyright © 2017 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Insertable cardiac monitors (ICMs) are used for long-term ECG monitoring. The Reveal LINQ ICM has an improved atrial fibrillation (AF) detection algorithm., Objective: The purpose of this study was to investigate the algorithm's real-world performance in patients with syncope, cryptogenic stroke, and known AF., Methods: Consecutive patients with implanted ICM and AF detection parameters automatically set and maintained depending on the indication for monitoring were included. A single reviewer annotated all stored episodes after ICM implant. A second reviewer annotated a random sample of 10% of all detected AF episodes. The episode detection positive predictive value as well as true and false detection rates were determined for AF episodes of different durations., Results: The study enrolled 3759 patients (1604 [43%] with syncope, 1049 [28%] with known AF, 1106 [29%] with cryptogenic stroke). Overall, 20,659 AF episodes were detected in 1020 patients. The gross episode detection positive predictive value was 84%, 73%, and 26% for all episodes (≥2 minutes) and improved to 97%, 95%, and 91% for detected AF episodes ≥1 hour in the syncope, known-AF, and cryptogenic stroke patient cohorts, respectively. The true (and false) detection rate was 0.23 (0.05), 3.8 (1.4), and 0.23 (0.65) per patient-month of monitoring for the syncope, known-AF, and cryptogenic stroke patient cohorts, respectively. Limiting ECG storage to the longest detected AF episode significantly reduced the burden of episode adjudication without significantly compromising the identification of patients with true AF., Conclusion: The performance of LINQ ICM is dependent on the AF incidence rate in the population being monitored, the programmed sensitivity of AF algorithm, and the duration of detected AF episodes., (Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Despite an extensive initial evaluation, the cause of up to a third of ischemic strokes remains undetermined. The detection of atrial fibrillation (AF) in these patients with cryptogenic stroke is critical as the diagnosis of AF would warrant anticoagulation to reduce the risk of recurrent stroke. Observational studies and prospective randomized controlled trials have shown that a substantial proportion of patients with cryptogenic stroke have AF detected by post-stroke cardiac monitoring with higher AF detection rates observed with longer monitoring periods., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: Traditional mapping of atrial fibrillation (AF) is limited by changing electrogram morphologies and variable cycle lengths., Objective: We tested the hypothesis that morphology recurrence plot analysis would identify sites of stable and repeatable electrogram morphology patterns., Methods: AF electrograms recorded from left atrial (LA) and right atrial (RA) sites in 19 patients (10 men; mean age 59 ± 10 years) before AF ablation were analyzed. Morphology recurrence plots for each electrogram recording were created by cross-correlation of each automatically detected activation with every other activation in the recording. A recurrence percentage, the percentage of the most common morphology, and the mean cycle length of activations with the most recurrent morphology were computed., Results: The morphology recurrence plots commonly showed checkerboard patterns of alternating high and low cross-correlation values, indicating periodic recurrences in morphologies. The mean recurrence percentage for all sites and all patients was 38 ± 25%. The highest recurrence percentage per patient averaged 83 ± 17%. The highest recurrence percentage was located in the RA in 5 patients and in the LA in 14 patients. Patients with sites of shortest mean cycle length of activations with the most recurrent morphology in the LA and RA had ablation failure rates of 25% and 100%, respectively (hazard ratio 4.95; P = .05)., Conclusion: A new technique to characterize electrogram morphology recurrence demonstrated that there is a distribution of sites with high and low repeatability of electrogram morphologies. Sites with rapid activation of highly repetitive morphology patterns may be critical to sustaining AF. Further testing of this approach to map and ablate AF sources is warranted., (Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: An electrocardiographic (ECG) screening test has been developed to identify patients being considered for a totally subcutaneous implantable cardioverter-defibrillator (S-ICD) at risk for T-wave oversensing., Objective: The purpose of this study was to determine the proportion of potential S-ICD recipients who fail the ECG screening test and to identify predictors of failure., Methods: Patients who already have an ICD but are not receiving antibradycardia pacing are representative of patients who might be considered for an S-ICD. One hundred such outpatients were enrolled in the study. Surface rhythm strips were recorded along the sensing vectors of the S-ICD system and the screening template applied. Clinical and standard ECG characteristics of patients who failed the test were compared to those who passed., Results: Patients had the following characteristics: 72% male, age 57 ± 16 years, body mass index 29 ± 6 kg/m(2), left ventricular ejection fraction 43% ± 17%, QRS duration 109 ± 23 ms, QTc interval 447 ± 39 ms, 44% had coronary disease, and 55% had heart failure. Among the 100 patients, 8% failed the screening test. There were no differences in patient clinical characteristics and most standard ECG measurements. However, patients with T-wave inversions in standard ECG leads I, II, and aVF had a 45% chance of failing., Conclusion: Eight percent of potential S-ICD patients were not eligible for the S-ICD after failing the screening test designed to identify patients susceptible to T-wave oversensing. Patients with T-wave inversions in leads I, II, and aVF on a standard ECG were 23 times more likely to fail. More work is needed in S-ICD sensing algorithms to increase patient eligibility for the S-ICD., (Copyright © 2014 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: The mechanisms of persistent human atrial fibrillation (AF) are not well understood., Objective: The purpose of this study was to examine whether left atrial (LA) drivers are present in persistent AF by performing a comprehensive evaluation of atrial activation frequency and organization using multisite atrial recordings and correlating the findings with atrial waveform frequency and organization on surface ECG., Methods: Nine patients undergoing catheter ablation for persistent AF were studied. Electrograms were recorded from at least 10 sites in each atrium, tagged to an electroanatomic map, and subjected to spectral analysis. Dominant frequency (DF) and regularity index were calculated at each site. Surface ECG recordings were analyzed to obtain precordial lead DFs and AF vector stability index., Results: Mean, maximum, and minimum DF and mean regularity index were higher in LA than right atrium (RA). DF was correlated with regularity index (R = 0.59, P <.0001) and negatively correlated with distance from maximal DF site (R = -0.80, P <.0001). Precordial lead DFs were highly correlated with atrial DFs. Vector stability index was 0.39 +/- 0.12 (P <.01 vs predicted if AF vector direction was random). LA-RA DF gradient and vector stability index were negatively correlated (R = -0.83, P <.05)., Conclusion: The existence of LA-RA frequency gradients in most patients in this study along with the regularity of LA activation and centrifugal dissipation of activation frequency suggest that LA drivers are often present in persistent AF. Analysis of AF vectors from surface ECG demonstrates spatial stability and correlates with intracardiac recordings. These findings may have implications for catheter ablation of persistent AF.

Background: Atrial fibrillation (AF) is a common complication after major noncardiac thoracic surgery and increases the cost and morbidity of these operations. We sought to derive and validate a clinical prediction rule to risk-stratify patients for postoperative AF., Methods: For a cohort of cancer patients who underwent noncardiac thoracic surgery, we examined the association of preoperative clinical variables with development of postoperative AF. Logistic regression identified multivariable predictors of AF and a clinical risk score was developed by assigning weighted point scores for the presence of each significant covariate. An independent data set was used for validation purposes., Results: Of the 856 patients, 147 (17.2%) developed postoperative AF. Male gender (odds ratio [OR] 1.7, 95% confidence interval [CI] 1.1 to 2.4), advanced age (55 to 74 years OR 4.4, 95% CI 2.0 to 9.8; > or =75 years OR 9.2, 95% CI 3.9 to 21.5), and preoperative heart rate greater than or equal to 72 beats per minute (OR 1.7, 95% CI 1.2 to 2.5) were independent predictors of postoperative AF. A risk score was assigned with male gender and heart rate greater than or equal to 72 beats per minute each receiving 1 point, and age 55 to 74 and greater than or equal to 75 years receiving 3 and 4 points, respectively. The risk of postoperative AF ranged from 0% (0 points) to 54.6% (6 points) (p < 0.001). The score-based risk in both derivation and validation sets was similar (p = 0.66)., Conclusions: A prediction rule using clinical variables can be used to predict the risk of postoperative AF after noncardiac thoracic surgery. This information can be used to guide prophylactic therapy.