Spatiotemporal characteristics of atrial fibrillation electrograms: a novel marker for arrhythmia stability and termination

Background: Sequentially mapped complex fractionated atrial electrograms (CFAE) and dominant frequency (DF) sites have been targeted during catheter ablation for atrial fibrillation (AF). However, these strategies have yielded variable success and have not been shown to correlate consistently with AF dynamics. Here, we evaluated whether the spatiotemporal stability of CFAE and DF may be a better marker of AF sustenance and termination. Methods: Eighteen sheep with 12 weeks of "one-kidney, one-clip" hypertension underwent open-chest studies. A total of 42 self-terminating (28–100 s) and 6 sustained (>15 min) AF episodes were mapped using a custom epicardial plaque and analyzed in 4-s epochs for CFAE, using the NavX CFE-m algorithm, and DF, using a Fast Fourier Transform. The spatiotemporal stability index (STSI) was calculated using the intraclass correlation coefficient of consecutive AF epochs. Results: A total of 67,733 AF epochs were analyzed. During AF initiation, mean CFE-m and the STSI of CFE-m/DF were similar between sustained and self-terminating episodes, although median DF was higher in sustained AF (p=0.001). During sustained AF, the STSI of CFE-m increased significantly (p=0.02), whereas mean CFE-m (p=0.5), median DF (p=0.07), and the STSI of DF remained unchanged (p=0.5). Prior to AF termination, the STSI of CFE-m was significantly lower (p<0.001), with a physiologically non-significant decrease in median DF (−0.3 Hz, p=0.006) and no significant changes in mean CFE-m (p=0.14) or the STSI of DF (p=0.06). Conclusions: Spatiotemporal stabilization of CFAE favors AF sustenance and its destabilization heralds AF termination. The STSI of CFE-m is more representative of AF dynamics than are the STSI of DF, sequential mean CFE-m, or median DF

Remote monitoring of implantable cardioverter-defibrillators: a systematic review and meta-analysis of clinical outcomes

Background: Remote monitoring (RM) of implantable cardioverter-defibrillators (ICD) is an established technology integrated into clinical practice. One recent randomized controlled trial (RCT) and several large device database studies have demonstrated a powerful survival advantage for ICD patients undergoing RM compared with those receiving conventional in-office (IO) follow-up. Objectives: This study sought to conduct a systematic published data review and meta-analysis of RCTs comparing RM with IO follow-up. Methods: Electronic databases and reference lists were searched for RCTs reporting clinical outcomes in ICD patients who did or did not undergo RM. Data were extracted from 9 RCTs, including 6,469 patients, 3,496 of whom were randomized to RM and 2,973 to IO follow-up. Results: In the RCT setting, RM demonstrated clinical outcomes comparable with office follow-up in terms of all-cause mortality (odds ratio [OR]: 0.83; p = 0.285), cardiovascular mortality (OR: 0.66; p = 0.103), and hospitalization (OR: 0.83; p = 0.196). However, a reduction in all-cause mortality was noted in the 3 trials using home monitoring (OR: 0.65; p = 0.021) with daily verification of transmission. Although the odds of receiving any ICD shock were similar in RM and IO patients (OR: 1.05; p = 0.86), the odds of inappropriate shock were reduced in RM patients (OR: 0.55; p = 0.002). Conclusions: Meta-analysis of RCTs demonstrates that RM and IO follow-up showed comparable overall outcomes related to patient safety and survival, with a potential survival benefit in RCTs using daily transmission verification. RM benefits include more rapid clinical event detection and a reduction in inappropriate shocks

Electrophysiological, electroanatomical, and structural remodeling of the atria as consequences of sustained obesity

Background: Obesity and atrial fibrillation (AF) are public health issues with significant consequences. Objectives This study sought to delineate the development of global electrophysiological and structural substrate for AF in sustained obesity. Methods: Ten sheep fed ad libitum calorie-dense diet to induce obesity over 36 weeks were maintained in this state for another 36 weeks; 10 lean sheep with carefully controlled weight served as controls. All sheep underwent electrophysiological and electroanatomic mapping; hemodynamic and imaging assessment (echocardiography and dual-energy x-ray absorptiometry); and histology and molecular evaluation. Evaluation included atrial voltage, conduction velocity (CV), and refractoriness (7 sites, 2 cycle lengths), vulnerability for AF, fatty infiltration, atrial fibrosis, and atrial transforming growth factor (TGF)-β1 expression. Results: Compared with age-matched controls, chronically obese sheep demonstrated greater total body fat (p 0.8) or ERP heterogeneity (p > 0.3). Obesity was associated with more episodes (p = 0.02), prolongation (p = 0.01), and greater cumulative duration (p = 0.02) of AF. Epicardial fat infiltrated the posterior LA in the obese group (p < 0.001), consistent with reduced endocardial voltage in this region. Atrial fibrosis (p = 0.03) and TGF-β1 protein (p = 0.002) were increased in the obese group. Conclusions: Sustained obesity results in global biatrial endocardial remodeling characterized by LA enlargement, conduction abnormalities, fractionated electrograms, increased profibrotic TGF-β1 expression, interstitial atrial fibrosis, and increased propensity for AF. Obesity was associated with reduced posterior LA endocardial voltage and infiltration of contiguous posterior LA muscle by epicardial fat, representing a unique substrate for AF

Aggressive risk factor reduction study for atrial fibrillation and implications for the outcome of ablation: the ARREST-AF cohort study

Version of record (Published version) freely available online at Publisher website BACKGROUND: The long-term outcome of atrial fibrillation (AF) ablation demonstrates attrition. This outcome may be due to failure to attenuate the progressive substrate promoted by cardiovascular risk factors. OBJECTIVES: The goal of this study was to evaluate the impact of risk factor and weight management on AF ablation outcomes. METHODS: Of 281 consecutive patients undergoing AF ablation, 149 with a body mass index ≥27 kg/m(2) and ≥1 cardiac risk factor were offered risk factor management (RFM) according to American Heart Association/American College of Cardiology guidelines. After AF ablation, all 61 patients who opted for RFM and 88 control subjects were assessed every 3 to 6 months by clinic review and 7-day Holter monitoring. Changes in the Atrial Fibrillation Severity Scale scores were determined. RESULTS: There were no differences in baseline characteristics, number of procedures, or follow-up duration between the groups (p = NS). RFM resulted in greater reductions in weight (p = 0.002) and blood pressure (p = 0.006), and better glycemic control (p = 0.001) and lipid profiles (p = 0.01). At follow-up, AF frequency, duration, symptoms, and symptom severity decreased more in the RFM group compared with the control group (all p < 0.001). Single-procedure drug-unassisted arrhythmia-free survival was greater in RFM patients compared with control subjects (p < 0.001). Multiple-procedure arrhythmia-free survival was markedly better in RFM patients compared with control subjects (p < 0.001), with 16% and 42.4%, respectively, using antiarrhythmic drugs (p = 0.004). On multivariate analysis, type of AF (p < 0.001) and RFM (hazard ratio 4.8 [95% confidence interval: 2.04 to 11.4]; p < 0.001) were independent predictors of arrhythmia-free survival. CONCLUSIONS: Aggressive RFM improved the long-term success of AF ablation. This study underscores the importance of therapy directed at the primary promoters of the AF substrate to facilitate rhythm control strategies

Electroanatomical Remodeling of the Atria in Obesity: Impact of Adjacent Epicardial Fat

OBJECTIVES: The aims of the study were to characterize: 1) electrical and electroanatomical remodeling in patients with atrial fibrillation (AF) with obesity; and 2) the impact of epicardial fat depots on adjacent atrial tissue. BACKGROUND: Obesity is associated with an increased risk of AF. METHODS: A total of 115 patients with AF who underwent AF ablation were screened. After exclusion, 26 patients were divided into 2 groups (obese: body mass index [BMI] ≥27 kg/m2 and reference: BMI <27 kg/m2). They underwent cardiac magnetic resonance (CMR) imaging and electroanatomic mapping of the left atrium (LA) in sinus rhythm before AF ablation. Atrial and ventricular epicardial adipose tissue (EAT) were assessed by CMR. The following electrophysiological parameters were assessed: global and regional voltage, conduction velocity (CV), electrogram fractionation, and CV heterogeneity. In addition, the regional relationship between LA EAT depots and the electrophysiological substrate was evaluated. RESULTS: The BMIs of the obese and reference groups were 30.2 ± 2.6 and 25.2 ± 1.3 kg/m2, respectively (p < 0.001). There was no difference in the left ventricular ejection fraction and a nonsignificant increase in LA size with obesity. Obesity was associated with increase in all measures of EAT (p < 0.05), with a predominant distribution adjacent to the posterior LA and the atrioventricular groove. Obesity was associated with reduced global CV (0.86 ± 0.31 m/s vs. 1.26 ± 0.29 m/s; p < 0.001), with a nonsignificant increase in conduction heterogeneity (p = 0.10), increased fractionation (54 ± 17% vs. 25 ± 10%; p < 0.001), and regional alteration in voltage (p < 0.001). Although the global LA voltage was preserved, there was greater voltage heterogeneity (p = 0.001) and increased low-voltage areas (13.9% vs. 3.4%; p < 0.001) in the obese group compared with the reference group. The low voltage areas were predominantly seen in the posterior and/or inferior LA, which was similar to location of EAT on CMR imaging. Among various measures of obesity, LA EAT volume correlated best with posterior LA fractionation (r2 = 0.55 for LA EAT volume vs. r2 = 0.36 for BMI) and CV (r2 = 0.31 for LA EAT volume vs. r2 = 0.22 for BMI). CONCLUSIONS: Obesity is associated with electroanatomical remodeling of the atria, with areas of low voltage, conduction slowing, and greater fractionation of electrograms. These changes were more pronounced in regions adjacent to epicardial fat depots, which suggested a role for fat depots in the development of the AF substrate