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Objectives This study describes a series of cases best explained by invoking the left septal fascicle (LSF) as a critical component of the arrhythmia circuit. Background Numerous anatomic studies have shown evidence of the LSF, but its precise role in the onset of arrhythmia is unclear. Methods This paper presents 5 cases that implicated the LSF as a critical component of arrhythmogenesis. Results The first case had ventricular fibrillation repeatedly documented after a single premature atrial complex, produced left-sided conduction delay and simultaneous earliest activation of the left anterior fascicle (LAF) and left posterior fascicle (LPF). The LSF was ablated, resulting in an arrhythmia cure. The second case showed narrow QRS morphology during fascicular re-entrant tachycardia. The earliest mid-septal diastolic potentials had distal-to-proximal activation suggesting an LSF as a retrograde common pathway. The third case, with multiple ectopic Purkinje-related premature complexes exhibited earliest Purkinje potentials in the mid-septum, with subsequent anterograde activation of the LAF and LPF. Ablation of the LSF eliminated the premature ventricular complexes (PVCs). The fourth case demonstrated LPF and LAF PVCs. The His-left bundle activation showed earliest potentials at the proximal insertion of the left bundle during LPF PVCs, as well as a distal-to-proximal activation pattern during LAF PVC, suggestive of LSF involvement. The fifth case had focal non–re-entrant fascicular beats successfully ablated over the LSF. Conclusions Involvement of the LSF is suspected with presentation of multiform fascicular and narrow QRS complex ventricular episodes of arrhythmia. Diagnoses and ablation require detailed mapping of the entire left sided conduction system.

Aims Population studies reporting contemporary long-term outcomes following catheter ablation of atrial fibrillation (AF) are sparse. We evaluated long-term clinical outcomes following AF ablation and examined variation in outcomes by age, sex, and the presence of heart failure. Methods and results We identified 30 601 unique patients (mean age 62.7 ± 11.8 years, 30.0% female) undergoing AF ablation from 2008 to 2017 in Australia and New Zealand using nationwide hospitalization data. The primary outcomes were all-cause mortality and rehospitalizations for AF or flutter, repeat AF ablation, and cardioversion. Secondary outcomes were rehospitalizations for other cardiovascular events. During 124 858.7 person-years of follow-up, 1900 patients died (incidence rate 1.5/100 person-years) with a survival probability of 93.0% (95% confidence interval (CI) 92.6–93.4%) by 5 years and 84.0% (95% CI 82.4–85.5%) by 10 years. Rehospitalizations for AF or flutter (13.3/100 person-years), repeat ablation (5.9/100 person-years), and cardioversion (4.5/100 person-years) were common, with respective cumulative incidence of 49.4% (95% CI 48.4–50.4%), 28.1% (95% CI 27.2–29.0%), and 24.4% (95% CI 21.5–27.5%) at 10 years post-ablation. Rehospitalizations for stroke (0.7/100 person-years), heart failure (1.1/100 person-years), acute myocardial infarction (0.4/100 person-years), syncope (0.6/100 person-years), other arrhythmias (2.5/100 person-years), and new cardiac device implantation (2.0/100 person-years) occurred less frequently. Elderly patients and those with comorbid heart failure had worse survival but were less likely to undergo repeat ablation, while long-term outcomes were comparable between the sexes. Conclusion Patients undergoing AF ablations had good long-term survival, a low incidence of rehospitalizations for stroke or heart failure, and about half remained free of rehospitalizations for AF or flutter, including for repeat AF ablation, or cardioversion.

Objectives: This study sought to prospectively study the development and then regression of premature ventricular contraction (PVC)-induced cardiomyopathy, with the hypothesis that structural left ventricular (LV) changes that are of potential clinical significance may endure beyond the period of exposure to PVCs. Background: Recovery of LV function after eradication of PVCs in PVC-induced cardiomyopathy is incompletely defined. Methods: Fifteen swine were exposed to: 1) 50% paced PVCs from the LV lateral epicardium for 12 weeks (LV PVC, n = 5); 2) no pacing for 12 weeks (Control, n = 5); or 3) 50% paced LV PVCs for 12 weeks followed by pacing cessation for 4 weeks (Recovery, n = 5). LV function was quantified biweekly in sinus rhythm with echocardiography. Dyssynchrony was measured from pressure-volume loops at baseline and terminal studies. LV fibrosis was quantified after sacrifice. Results: LV ejection fraction during sinus rhythm fell between baseline and terminal studies in the LV PVC group (65.8 ± 3.0 to 39.3 ± 3.2; p < 0.05), whereas there was no significant change in the Control group (69.6 ± 3.0 to 72.2 ± 3.0; p = NS) or after Recovery (64.5 ± 3.4% to 61.4 ± 3.4%; p = NS) groups. There was a significant increase in LV dyssynchrony measured during sinus rhythm between baseline and terminal studies in the LV PVC group (4.0 ± 1.5% to 9.0 ± 1.5%; p < 0.05); there was a similar increase in dyssynchrony that persisted 4 weeks after PVC cessation in the Recovery group (4.4 ± 1.7% to 12.8 ± 1.7%; p < 0.05). After sacrifice, percent fibrosis was higher in the LV PVC group compared with Control (5.7 ± 0.3% vs. 3.0 ± 0.3%; p < 0.05) and remained elevated in Recovery (4.1 ± 0.3% vs. 3.0 ± 0.3%; p < 0.05) despite return to baseline LV ejection fraction. Conclusions: In a swine model of PVC-induced cardiomyopathy, cessation of PVCs for 4 weeks leads to normalization of LV systolic function but significant changes in myocardial fibrosis and LV dyssynchrony during sinus rhythm persist.

This study sought to define the extent and spatial distribution of endocardial-epicardial dissociation (EED) in a swine model.The mechanisms underlying persistent atrial fibrillation (AF) remain unclear.Sixteen swine underwent simultaneous endocardial and epicardial mapping using 32-electrode grid catheters. This included 6 swine with rapid atrial pacing-induced atrial remodeling. Three right atrial (RA) and 3 left atrial (LA) regions were mapped during sinus rhythm, atrial pacing, acute or persistent AF, and AF in the presence of pericardial acetylcholine. Unipolar electrogram recordings over 10-s epochs underwent offline phase analysis using customized software. Regional activation patterns on paired surfaces and the instantaneous phase at each matched electrode location were analyzed. EED was defined as paired electrodes out of phase by ≥20 ms.The mean distance between matched endocardial-epicardial electrode pairs was 4.4 ± 1.8 mm. During episodes of AF, rotational activations with ≥3 full rotations were not seen. EED was seen during 34.4 ± 16.4% of mapped time periods: LARA, persistentacute AF in the LA, and acetylcholine-inducedacute AF in both atria (p 0.05 for each). Most marked EED in persistent AF was in the LA appendage (47.2 ± 3.7%) and the LA posterior wall (50.3 ± 4.7%).Marked EED was seen in a swine model of AF, particularly during persistent AF. There was significantly more EED in the LA than the RA and, particularly, in the LA PW and LAA. Mapping approaches limited to the endocardium may not sufficiently characterize the complexity of AF.

Ventricular bipolar voltage values0.5 and1.0/1.5 mV (epi- and endocardium) correlating with dense scar and border zone, respectively, were established using a 3.5-mm tip catheter. Novel microelectrode catheters promise improved mapping resolution; however, whether standard voltage criteria apply to catheters with smaller electrode size and interelectrode distance remains unclear.The purpose of this study was to determine whether traditional bipolar voltage criteria for scar apply during substrate mapping with a microelectrode catheter.Paired bipolar and microbipolar voltage values were acquired from control swine (n = 2) using the microelectrode catheter and assessed for systemic differences. In a postinfarction swine model (n = 6), scar characteristics were compared between the bipolar maps and microbipolar maps using both standard and adjusted voltage criteria derived from the control animals.In control swine, although 5th percentile values for bipolar and microbipolar voltage were similar (1.12 vs 1.22 mV [left ventricular (LV) endo]; 0.88 mV vs 0.98 mV [epi]), median values were significantly greater when acquired by microbipolar electrodes (3.60 vs 6.76 mV, P = .002 [LV endo]; 2.61 vs 2.72 mV, P = .02 [epi]). Microbipolar values were systematically larger by 2.0× and 1.4× in the LV endocardium and epicardium, respectively. Application of standard voltage values to microbipolar maps in postinfarct swine underestimated scar area by approximately 41% in the LV endocardium (13.7 vs 33.4 cmBipolar voltage values acquired from microelectrodes are systemically larger than those acquired from standard catheters. New reference values should be established for these novel catheters.

Background Atrial fibrillation/atrial flutter (AF/AFL) hospitalisations are common, however, little is known about the long-term outcomes of these episodes. Objective To examine the incidence of mortality, all-cause and cause-specific re-hospitalisations at up to 8 years after a hospitalisation for AF/AFL. Methods Unique patients hospitalised with a primary diagnosis of AF/AFL from 2008–2015 were identified using nation-wide hospitalisation data from Australia and New Zealand. All-cause mortality was the primary outcome. Secondary endpoints included all-cause and cause-specific re-hospitalisations. Results were reported as incident rate per 100 patient-years. Results We included 265,737 patients (mean age 69.9±13.9y, female 45.2%, elective 28.7%). The median length of stay was 1 day (Interquartile range [IQR] 0–4 days) and the median CHA2DS2-VASc score was 2 (IQR 1–2). During the index hospitalisation, 9,837 (3.7%) patients underwent catheter or surgical ablation and 52,634 (19.8%) underwent cardioversion. During the median follow-up time of 3.4 years (range 0–8.0 years), 53,669 patients died (incident rate of 5.7/100 patient-years) with a survival probability gradually decreasing from 92.8% (95% CI 92.7–92.9%) at 1-year to 65.4% (95% CI 64.9–65.8%) at 8-years post-discharge (Table 1 and Figure 1). All-cause re-hospitalisations occurred in 210,118 patients (incident rate of 22.2/100 patient-years) with a rehospitalisation-free survival probability of 7.1% (95% CI 6.9—7.3%) at the end of follow-up. Unplanned re-hospitalisations occurred more frequently than planned episodes (incident rate of 17.2 vs. 16.6/100 patient-years respectively). AF/AFL accounted for 25.1% of all-cause re-hospitalisations (incident rate of 8.9/100 patient-years) and the probability of freedom from re-hospitalisations for AF/AFL was 55.4% (95% CI 55.0–55.8%) at 8-years. Incident rates of re-hospitalisations for catheter ablation (1.5/100 patient-years), stroke (1.6/100 patient-years), heart failure (2.7/100 patient-years), and acute myocardial infarction (1.0/100 patient-years) were low. In subgroup analyses, worse survival was observed in female patients, older age groups, patients with comorbid heart failure, hypertension, diabetes, and those who did not undergo ablation during the index hospitalisation. Conclusion Nearly two-thirds of patients were surviving by 8-years following an AF/AFL hospitalisation with a low rate of re-hospitalisations for stroke, heart failure, and myocardial infarction. However, re-hospitalisations for recurrent atrial arrhythmia were common. Efforts to reduce re-hospitalisations, especially unplanned encounters, are required to improve patient outcomes. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): National Heart Foundation of Australia

IMPORTANCE: Millions of clinicians rely daily on automated preliminary electrocardiogram (ECG) interpretation. Critical comparisons of machine learning–based automated analysis against clinically accepted standards of care are lacking. OBJECTIVE: To use readily available 12-lead ECG data to train and apply an explainability technique to a convolutional neural network (CNN) that achieves high performance against clinical standards of care. DESIGN, SETTING, AND PARTICIPANTS: This cross-sectional study was conducted using data from January 1, 2003, to December 31, 2018. Data were obtained in a commonly available 12-lead ECG format from a single-center tertiary care institution. All patients aged 18 years or older who received ECGs at the University of California, San Francisco, were included, yielding a total of 365 009 patients. Data were analyzed from January 1, 2019, to March 2, 2021. EXPOSURES: A CNN was trained to predict the presence of 38 diagnostic classes in 5 categories from 12-lead ECG data. A CNN explainability technique called LIME (Linear Interpretable Model-Agnostic Explanations) was used to visualize ECG segments contributing to CNN diagnoses. MAIN OUTCOMES AND MEASURES: Area under the receiver operating characteristic curve (AUC), sensitivity, and specificity were calculated for the CNN in the holdout test data set against cardiologist clinical diagnoses. For a second validation, 3 electrophysiologists provided consensus committee diagnoses against which the CNN, cardiologist clinical diagnosis, and MUSE (GE Healthcare) automated analysis performance was compared using the F1 score; AUC, sensitivity, and specificity were also calculated for the CNN against the consensus committee. RESULTS: A total of 992 748 ECGs from 365 009 adult patients (mean [SD] age, 56.2 [17.6] years; 183 600 women [50.3%]; and 175 277 White patients [48.0%]) were included in the analysis. In 91 440 test data set ECGs, the CNN demonstrated an AUC of at least 0.960 for 32 of 38 classes (84.2%). Against the consensus committee diagnoses, the CNN had higher frequency-weighted mean F1 scores than both cardiologists and MUSE in all 5 categories (CNN frequency-weighted F1 score for rhythm, 0.812; conduction, 0.729; chamber diagnosis, 0.598; infarct, 0.674; and other diagnosis, 0.875). For 32 of 38 classes (84.2%), the CNN had AUCs of at least 0.910 and demonstrated comparable F1 scores and higher sensitivity than cardiologists, except for atrial fibrillation (CNN F1 score, 0.847 vs cardiologist F1 score, 0.881), junctional rhythm (0.526 vs 0.727), premature ventricular complex (0.786 vs 0.800), and Wolff-Parkinson-White (0.800 vs 0.842). Compared with MUSE, the CNN had higher F1 scores for all classes except supraventricular tachycardia (CNN F1 score, 0.696 vs MUSE F1 score, 0.714). The LIME technique highlighted physiologically relevant ECG segments. CONCLUSIONS AND RELEVANCE: The results of this cross-sectional study suggest that readily available ECG data can be used to train a CNN algorithm to achieve comparable performance to clinical cardiologists and exceed the performance of MUSE automated analysis for most diagnoses, with some exceptions. The LIME explainability technique applied to CNNs highlights physiologically relevant ECG segments that contribute to the CNN’s diagnoses.

Background: The key drivers of symptom severity and health-related quality of life (hr-QOL) in patients with atrial fibrillation (AF) remain unclear. We aimed to determine the relative contribution to symptom severity and hr-QOL of clinical factors including left ventricular (LV) diastolic function and ventricular rate control during AF and of psychological functioning.Methods: Seventy-eight consecutive patients with symptomatic AF and preserved LV systolic function underwent detailed evaluation of i) AF symptom severity and hr-QOL; ii) clinical factors including left ventricular (LV) diastolic function, AF burden, and ventricular rate during AF and iii) state and trait aspects of psychological functioning.Results: Moderate-to-severe AF-related symptoms were reported by 64% of the study population whilst 36% reported no more than mild symptoms. Worse symptom severity was associated with a higher score on the Perceived Stress Scale (16.7 +/- 4.4 vs. 5.4 +/- 4.4, p < 0.0001) and higher prevalence of the Type D Personality (20150 vs. 4/28, p = 0.012). In multivariable models, only a predisposition to subjectively appraise life situations as stressful (higher PSS score) and a personality with a higher degree of negative affectivity and social inhibition (higher TDPS score) were independent predictors of higher AF symptom severity and poorer hr-QOL. No clinical factors including AF burden, ventricular rates during AF or LV diastolic function were significant predictors of AF-specific symptoms or hr-QOL.Conclusion: In a tertiary AF population with preserved LV systolic function, only psychological functioning consistently predicts both AF-related symptoms and hr-QOL. LV diastolic function, AF burden, and ventricular rate during AF are not independent predictors.

Background Leadless pacemaker is a novel technology, and evidence supporting its use is uncertain. We performed a systematic review and meta‐analysis to examine the safety and efficacy of leadless pacemakers implanted in the right ventricle. Methods and Results We searched PubMed and Embase for studies published before June 6, 2020. The primary safety outcome was major complications, whereas the primary efficacy end point was acceptable pacing capture threshold (≤2 V). Pooled estimates were calculated using the Freedman‐Tukey double arcsine transformation. Of 1281 records screened, we identified 36 observational studies of Nanostim and Micra leadless pacemakers, with most (69.4%) reporting outcomes for the Micra. For Micra, the pooled incidence of complications at 90 days (n=1608) was 0.46% (95% CI, 0.08%–1.05%) and at 1 year (n=3194) was 1.77% (95% CI, 0.76%–3.07%). In 5 studies with up to 1‐year follow‐up, Micra was associated with 51% lower odds of complications compared with transvenous pacemakers (3.30% versus 7.43%; odds ratio [OR], 0.49; 95% CI, 0.34–0.70). At 1 year, 98.96% (95% CI, 97.26%–99.94%) of 1376 patients implanted with Micra had good pacing capture thresholds. For Nanostim, the reported complication incidence ranged from 6.06% to 23.54% at 90 days and 5.33% to 6.67% at 1 year, with 90% to 100% having good pacing capture thresholds at 1 year (pooled result not estimated because of the low number of studies). Conclusions Most studies report outcomes for the Micra, which is associated with a low risk of complications and good electrical performance up to 1‐year after implantation. Further data from randomized controlled trials are needed to support the widespread adoption of these devices in clinical practice.

This study sought to identify acute changes in human atrial electrophysiology during alcohol exposure.The mechanism by which a discrete episode of atrial fibrillation (AF) occurs remains unknown. Alcohol appears to increase the risk for AF, providing an opportunity to study electrophysiologic effects that may render the heart prone to arrhythmia.In this randomized, double-blinded, placebo-controlled trial, intravenous alcohol titrated to 0.08% blood alcohol concentration was compared with a volume and osmolarity-matched, masked, placebo in patients undergoing AF ablation procedures. Right, left, and pulmonary vein atrial effective refractory periods (AERPs) and conduction times were measured pre- and post-infusion. Isoproterenol infusions and burst atrial pacing were used to assess AF inducibility.Of 100 participants (50 in each group), placebo recipients were more likely to be diabetic (22% vs. 4%; p = 0.007) and to have undergone a prior AF ablation (36% vs. 22%; p = 0.005). Pulmonary vein AERPs decreased an average of 12 ms (95% confidence interval: 1 to 22 ms; p = 0.026) in the alcohol group, with no change in the placebo group (p = 0.98). Whereas no statistically significant differences in continuously assessed AERPs were observed, the proportion of AERP sites tested that decreased with alcohol (median: 0.5; interquartile range: 0.6 to 0.6) was larger than with placebo (median: 0.4; interquartile range: 0.2 to 0.6; p = 0.0043). No statistically significant differences in conduction times or in the proportion with inducible AF were observed.Acute exposure to alcohol reduces AERP, particularly in the pulmonary veins. These data demonstrate a direct mechanistic link between alcohol, a common lifestyle exposure, and immediate proarrhythmic effects in human atria. (How Alcohol Induces Atrial Tachyarrhythmias Study [HOLIDAY]; NCT01996943).

This study describes a series of cases best explained by invoking the left septal fascicle (LSF) as a critical component of the arrhythmia circuit.Numerous anatomic studies have shown evidence of the LSF, but its precise role in the onset of arrhythmia is unclear.This paper presents 5 cases that implicated the LSF as a critical component of arrhythmogenesis.The first case had ventricular fibrillation repeatedly documented after a single premature atrial complex, produced left-sided conduction delay and simultaneous earliest activation of the left anterior fascicle (LAF) and left posterior fascicle (LPF). The LSF was ablated, resulting in an arrhythmia cure. The second case showed narrow QRS morphology during fascicular re-entrant tachycardia. The earliest mid-septal diastolic potentials had distal-to-proximal activation suggesting an LSF as a retrograde common pathway. The third case, with multiple ectopic Purkinje-related premature complexes exhibited earliest Purkinje potentials in the mid-septum, with subsequent anterograde activation of the LAF and LPF. Ablation of the LSF eliminated the premature ventricular complexes (PVCs). The fourth case demonstrated LPF and LAF PVCs. The His-left bundle activation showed earliest potentials at the proximal insertion of the left bundle during LPF PVCs, as well as a distal-to-proximal activation pattern during LAF PVC, suggestive of LSF involvement. The fifth case had focal non-re-entrant fascicular beats successfully ablated over the LSF.Involvement of the LSF is suspected with presentation of multiform fascicular and narrow QRS complex ventricular episodes of arrhythmia. Diagnoses and ablation require detailed mapping of the entire left sided conduction system.

Background: Endocardial-epicardial dissociation and focal breakthroughs in humans with atrial fibrillation (AF) have been recently demonstrated using activation mapping of short 10-second AF segments. In the current study, we used simultaneous endo-epi phase mapping to characterize endo-epi activation patterns on long segments of human persistent AF. Methods: Simultaneous intraoperative mapping of endo- and epicardial lateral right atrium wall was performed in patients with persistent AF using 2 high-density grid catheters (16 electrodes, 3 mm spacing). Filtered unipolar and bipolar electrograms of continuous 2-minute AF recordings and electrodes locations were exported for phase analyses. We defined endocardial-epicardial dissociation as phase difference of ≥20 ms between paired endo-epi electrodes. Wavefronts were classified as rotations, single wavefronts, focal waves, or disorganized activity as per standard criteria. Endo-Epi wavefront patterns were simultaneously compared on dynamic phase maps. Complex fractionated electrograms were defined as bipolar electrograms with ≥5 directional changes occupying at least 70% of sample duration. Results: Fourteen patients with persistent AF undergoing cardiac surgery were included. Endocardial-epicardial dissociation was seen in 50.3% of phase maps with significant temporal heterogeneity. Disorganized activity (Endo: 41.3% versus Epi: 46.8%, P =0.0194) and single wavefronts (Endo: 31.3% versus Epi: 28.1%, P =0.129) were the dominant patterns. Transient rotations (Endo: 22% versus Epi: 19.2%, P =0.169; mean duration: 590±140 ms) and nonsustained focal waves (Endo: 1.2% versus Epi: 1.6%, P =0.669) were also observed. Apparent transmural migration of rotational activations (n=6) from the epi- to the endocardium was seen in 2 patients. Electrogram fractionation was significantly higher in the epicardium than endocardium (61.2% versus 51.6%, P Conclusions: Simultaneous endo-epi phase mapping of prolonged human persistent AF recordings shows significant Endocardial-epicardial dissociation marked temporal heterogeneity, discordant and transitioning wavefronts patterns and complex fractionations. No sustained focal activity was observed. Such complex 3-dimensional interactions provide insight into why endocardial mapping alone may not fully characterize the AF mechanism and why endocardial ablation may not be sufficient. Graphic Abstract: A graphic abstract is available for this article.

Introduction: Permanent junctional reciprocating tachycardia (PJRT) is a rare supraventricular tachycardia (SVT), typically involving a single decremental posteroseptal accessory pathway (AP). Methods: Four patients with long RP SVT underwent electrophysiology (EP) study and ablation. The cases were reviewed. Results: Case 1 recurred despite 3 prior ablations at the site of earliest retrograde atrial activation during orthodromic reciprocating tachycardia (ORT). Mapping during a repeat EP study demonstrated a prepotential in the coronary sinus (CS). Ablation over the earliest atrial activation in the CS resulted in dissociation of the potential from the atrium during sinus rhythm. The potential was traced back to the CS os and ablated. Case 2 underwent successful ablation at 6 o'clock on the mitral annulus (MA). ORT recurred and successful ablation was performed at 1 o'clock on the MA. Case 3 had tachycardia with variation in both V-A and A-H intervals which precluded the use of usual maneuvers so we used simultaneous atrial and ventricular pacing and introduced a premature atrial contraction with a closely coupled premature ventricular contraction. Case 4 had had two prior atrial fibrillation ablations with continued SVT over a decremental atrioventricular bypass tract that was successfully ablated at 5 o'clock on the tricuspid annulus. A second SVT consistent with a concealed nodoventricular pathway was successfully ablated at the right inferior extension of the AV nodal slow pathway. Conclusion: We describe challenging cases of PJRT by virtue of complex anatomy, diagnostic features, and multiple arrhythmia mechanisms.

IntroductionOutcome of patients undergoing catheter ablation of atrial fibrillation (AF) varies widely. We sought to investigate whether parameters derived from the spectral analysis of surface ECG and intracardiac AF electrograms can predict outcome in patients referred for pulmonary vein isolation (PVI).MethodsResultsWe performed spectral analysis on the surface ECG and intracardiac electrograms from patients referred for AF ablation. After filtering and QRST subtraction, we measured the dominant frequency (DF), regularity index (RI) and the organizational index (OI) of fibrillatory electrograms and determined their value for predicting AF recurrence after ablation. A subjective, blinded prediction based on the surface ECG was also performed.We analyzed data from 153 PVI procedures in 140 patients (67.1% with persistent or longstanding AF). In a multivariable model, DF in the right atrium (RA) and distal coronary sinus (CSd)-to-RA DF gradient predicted AF recurrence (OR, 3.52, P=0.023 and OR, 0.2, P=0.034, respectively). DF in RA and CSd to RA DF gradient had a good predictive value for PVI outcome (area under the curve [AUC] of 0.73, P=0.007 and 0.74, P=0.007, respectively). These performed better than the subjective predictions of experienced electrophysiologists (P=0.2).ConclusionsHigher RA DF, lower CSd to RA DF gradient predicted recurrence after AF ablation. These spectral measures suggest a more remodeled atrial substrate and may provide simple tools for risk stratification or predict the need for additional substrate modification in patients referred for AF ablation.

Background Current phase mapping systems for atrial fibrillation create 2-dimensional (2D) maps. This process may affect the accurate detection of rotors. We developed a 3-dimensional (3D) phase mapping technique that uses the 3D locations of basket electrodes to project phase onto patient-specific left atrial 3D surface anatomy. Objective We sought to determine whether rotors detected in 2D phase maps were present at the corresponding time segments and anatomical locations in 3D phase maps. Methods One-minute left atrial atrial fibrillation recordings were obtained in 14 patients using the basket catheter and analyzed off-line. Using the same phase values, 2D and 3D phase maps were created. Analysis involved determining the dominant propagation patterns in 2D phase maps and evaluating the presence of rotors detected in 2D phase maps in the corresponding 3D phase maps. Results Using 2D phase mapping, the dominant propagation pattern was single wavefront (36.6%) followed by focal activation (34.0%), disorganized activity (23.7%), rotors (3.3%), and multiple wavefronts (2.4%). Ten transient rotors were observed in 9 of 14 patients (64%). The mean rotor duration was 1.1 ± 0.7 seconds. None of the 10 rotors observed in 2D phase maps were seen at the corresponding time segments and anatomical locations in 3D phase maps; 4 of 10 corresponded with single wavefronts in 3D phase maps, 2 of 10 with 2 simultaneous wavefronts, 1 of 10 with disorganized activity, and in 3 of 10 there was no coverage by the basket catheter at the corresponding 3D anatomical location. Conclusion Rotors detected in 2D phase maps were not observed in the corresponding 3D phase maps. These findings may have implications for current systems that use 2D phase mapping.

Background: The cornerstone of atrial fibrillation (AF) ablation is isolation of the pulmonary veins (PVs). Patients with recurrent AF undergoing repeat ablation usually have PV reconnection (PVr). The ablation strategy and outcome of patients undergoing repeat ablation who have persistent isolation of all PVs (PVi) at the time of repeat ablation is unknown.Methods and results: We studied consecutive patients with recurrent AF undergoing repeat ablation and compared patients with PVi to those with PVr. One hundred fifty-two patients underwent repeat ablation, and of these, 25 patients (16.4%) had PVi. Patients with PVi underwent ablation targeting any isoproterenol induced AF triggers, atrial substrate, or inducible atrial tachycardias or flutters. Patients with PVi compared to PVr were more likely to have a history of persistent AF (64% vs. 26%; P < 0.0001), obesity (BMI 30.4 vs. 28.2; P = 0.05), and prior use of contact force sensing catheters (28% vs. 0.8%, P < 0.0001). After a mean follow-up of 19 +/- 15 months, 56% of PVi patients remained in sinus rhythm compared to 76.3% of PVr patients (P = 0.036). In a multi-variable model, PVi patients and those with cardiomyopathy had a higher risk of recurrent atrial tachyarrhythmias (HR = 3.6 95%, CI 1.6-8.3, P = 0.002 and HR = 6.2, 95% CI 2.3-16.3, P < 0.0001, respectively).Conclusion: In patients who have all PVs isolated at the time of the redo AF ablation, a strategy of targeting non-PV AF triggers and inducible flutters can still lead to AF freedom in more than half of patients. Patients with PVr, however, have a better long-term outcome.

Background: Nodofascicular and nodoventricular (NFV) accessory pathways connect the atrioventricular node and the Purkinje system or ventricular myocardium, respectively. Concealed NFV pathways participate as the retrograde limb of supraventricular tachycardia (SVT). Manifest NFV pathways can comprise the anterograde limb of wide-complex SVT but are quite rare. The purpose of this report is to highlight the electrophysiological properties and sites of ablation for manifest NFV pathways. Methods: Eight patients underwent electrophysiology studies for wide-complex tachycardia (3), for narrow-complex tachycardia (1), and preexcitation (4). Results: NFV was an integral part of the SVT circuit in 3 patients. Cases 1 to 2 were wide-complex tachycardia because of manifest NFV SVT. Case 3 was a bidirectional NFV that conducted retrograde during concealed NFV SVT and anterograde causing preexcitation during atrial pacing. NFV was a bystander during atrioventricular node re-entrant tachycardia, atrial fibrillation, atrial flutter, and orthodromic atrioventricular re-entrant tachycardia in 4 cases and caused only preexcitation in 1. Successful NFV ablation was achieved empirically in the slow pathway region in 1 case. In 5 cases, the ventricular insertion was mapped to the slow pathway region (2 cases) or septal right ventricle (3 cases). The NFV was not mapped in cases 5 and 7 because of its bystander role. QRS morphology of preexcitation predicted the right ventricle insertion sites in 4 of the 5 cases in which it was mapped. During follow-up, 1 patient noted recurrent palpitations but no documented SVT. Conclusions: Manifest NFV may be critical for wide-complex tachycardia/manifest NFV SVT, act as the retrograde limb for narrow-complex tachycardia/concealed NFV SVT, or cause bystander preexcitation. Ablation should initially target the slow pathway region, with mapping of the right ventricle insertion site if slow pathway ablation is not successful. The QRS morphology of maximal preexcitation may be helpful in predicting successful right ventricle ablation site.

Objectives The goal of this study was to characterize, in detail, focal atrial tachycardia (AT) arising from the crista terminalis to investigate associations with other atrial arrhythmia and to define long-term ablation outcomes. Background The crista terminalis is known to be the most common site of origin for focal AT, but it is not well characterized. Methods This study retrospectively identified a total of 548 ablation procedures for AT performed at a single center over a 16-year period, of which 171 were arising from the crista terminalis. Results Compared with patients with other AT sites of origin, crista terminalis AT patients were older (57.3 vs. 47.3 years), more commonly female (72.9% vs. 59.1%), were more commonly associated with coexistent atrioventricular nodal re-entry tachycardia (17.1% vs. 9.7%), and were more likely to be inducible with programmed stimulation (81.5% vs. 58.9%). There was preferential conduction in the superior-inferior axis along the crista terminalis. Acute ablation success rate was high (92.2%) and improved significantly when three-dimensional mapping was used (98.5%). Recurrence in the first 12 months after a successful ablation was 9.7%. Only 2 patients developed atrial fibrillation over the long-term follow-up of >7 years. Conclusions This large series characterized the clinical and electrophysiological features and immediate and long-term ablation outcomes for AT originating from the crista terminalis. Features of the tachycardia suggest that age-related localized remodeling of the crista terminalis causes a superficial endocardial zone of conduction slowing leading to re-entry. Ablation outcomes were good, with long-term freedom from atrial arrhythmia.

Background An association between atrial fibrillation ( AF ), anxiety, and depression is recognized, but the spectrum of psychological distress remains unclear. We aimed to characterize the severity and predictors of distress associated with AF in a tertiary population and its response to AF management. Methods and Results Seventy‐eight patients with symptomatic AF underwent evaluation, including of AF symptom severity, health‐related quality of life, psychological distress, suicidal ideation, and specific personality traits. Twenty participants underwent AF ablation and 58 were managed medically, with repeat assessments at 4, 8, and 12 months. Severe distress (Hospital Anxiety and Depression Scale score, ≥15/42) was identified in 27 of 78 (35%). Independent predictors were a personality marked by vulnerability to stress (Perceived Stress Scale: R 2 , 0.54; β=0.7±0.1; t=7.8; P R 2 , 0.47; β=0.7±0.1; t=6.7; P R 2 , 0.35; odds ratio, 1.22±0.06; P R 2 , 0.48; odds ratio, 1.43±0.14; P AF ablation (median AF burden 1% [0–1%] over 12 months) was associated with significant reductions in distress (Hospital Anxiety and Depression Scale score, 13.9±1.8 to 4.3±1.8; P P =0.02). Conclusions There was a high prevalence of severe psychological distress (35%) and of suicidal ideation (20%) in a tertiary AF population, with personality traits predicting both. Effective AF ablation was associated with significant improvements, suggesting AF itself may be a treatable causative factor of distress.

Frequent ventricular ectopy is a common clinical presentation in patients suffering idiopathic ventricular outflow tract arrhythmias. These are focal arrhythmias that generally occur in patients without structural heart disease and share a predilection for characteristic anatomic sites of origin. Mechanistically, they are generally due to cyclic adenosine monophosphate (cAMP)-mediated triggered activity. As a result, there is typically an exercise or catecholamine related mode of induction and often a sensitivity to suppression with adenosine. Treatment options include clinical surveillance, medical therapy with anti-arrhythmic agents or catheter ablation. Medical therapy may offer symptomatic benefit but may have side-effects and usually results in burden reduction rather than eradication of ectopy. Catheter ablation using contemporary mapping techniques, whilst associated with some inherent procedural risk, is a potentially curative and safe option in most patients. Although usually associated with a good prognosis, some patients may develop an ectopy-mediated cardiomyopathy or, rarely, ectopy-induced polymorphic ventricular arrhythmias; catheter ablation is the treatment of choice in those patients.

The pathophysiology of cardiomyopathy associated with premature ventricular contractions (PVCs) remains unclear.This study prospectively explored cardiomyopathy development in a swine model of paced ectopic beats.A total of 35 swine underwent pacemaker implantation. A group exposed to paced bigeminy from the right ventricular apex (RVA) for 14 weeks (RVA PVC) (n = 10) were compared with a group exposed to regular pacing from the RVA at 140 beats/min (RV-140) (n = 5) and a control group (n = 5). To test the role of ectopic beat dyssynchrony, further groups were exposed for 12 weeks to bigeminy from the right ventricular free wall (RVFW PVC) (n = 5), the left ventricular epicardium (LV Epi PVC) (n = 5) or the right atrium (premature atrial complex) (n = 5).After 14 weeks, the mean left ventricular ejection fraction (LVEF) was significantly lower in the RVA PVC group than in the RV-140 or control groups (p 0.05). LVEF declined significantly in the LV Epi PVC (65.2 ± 2.4% to 39.7 ± 3.0%; p 0.01) and RVFW PVC (66.1 ± 2.6% to 48.6 ± 2.7%; p 0.01) groups, with final LVEF significantly lower and ventricular fibrosis significantly higher in the LV Epi PVC group compared with all others (p 0.05). Protein levels of pRyR2, NCX-1, CaMKII-α, and PLN were up-regulated and levels of SERCA2a were down-regulated in the LV Epi PVC group compared with the control group (p 0.05). Longer ectopic beat QRS duration and greater LV dyssynchrony were significantly associated with larger declines in LV systolic function.In a swine model of paced ectopic beats, PVC-induced cardiomyopathy is phenotypically distinct from a tachycardia-induced cardiomyopathy. Cardiomyopathy severity is strongly associated with severity of the hemodynamic derangement associated with the paced ectopic beats, particularly the extent of LV dyssynchrony.

Outcome of patients undergoing catheter ablation of atrial fibrillation (AF) varies widely. We sought to investigate whether parameters derived from the spectral analysis of surface ECG and intracardiac AF electrograms can predict outcome in patients referred for pulmonary vein isolation (PVI).We performed spectral analysis on the surface ECG and intracardiac electrograms from patients referred for AF ablation. After filtering and QRST subtraction, we measured the dominant frequency (DF), regularity index (RI) and the organizational index (OI) of fibrillatory electrograms and determined their value for predicting AF recurrence after ablation. A subjective, blinded prediction based on the surface ECG was also performed.We analyzed data from 153 PVI procedures in 140 patients (67.1% with persistent or longstanding AF). In a multivariable model, DF in the right atrium (RA) and distal coronary sinus (CSd)-to-RA DF gradient predicted AF recurrence (OR, 3.52, P = 0.023 and OR, 0.2, P = 0.034, respectively). DF in RA and CSd to RA DF gradient had a good predictive value for PVI outcome (area under the curve [AUC] of 0.73, P = 0.007 and 0.74, P = 0.007, respectively). These performed better than the subjective predictions of experienced electrophysiologists ( P = 0.2).Higher RA DF, lower CSd to RA DF gradient predicted recurrence after AF ablation. These spectral measures suggest a more remodeled atrial substrate and may provide simple tools for risk stratification or predict the need for additional substrate modification in patients referred for AF ablation.

Left atrial (LA) structure and function are intimately related to the clinical phenotypes of atrial fibrillation (AF), and have direct implications for the success or otherwise of various therapeutic strategies. In conjunction with intrinsic structural characteristics of the LA, pathological remodelling to a large extent dictates the clinical course of AF. Remodelling is a product of the physiological and structural plasticity of the LA in disease states (including AF itself), and manifests as electrical, physical and structural changes that promote the substrate necessary for AF maintenance. The degree of remodelling impacts upon the efficacy of pharmacological, non-pharmacological and interventional treatments for AF. Evolving therapies seek to specifically target these processes although presently, several remain in the development phase. Catheter ablation (CA) is now firmly established as a highly effective treatment for AF, although increasing its efficacy in the remodelled LA of more severe AF phenotypes remains an ongoing challenge.

Atrial fibrillation (AF) is the most commonly encountered sustained cardiac rhythm disorder, is an independent risk factor for stroke, heart failure and death, and its development is promoted by a range of common cardiovascular pathologies. The management of AF is directed at these predisposing conditions, at reducing the risk of systemic thromboembolism, and towards rate or rhythm control of the arrhythmia. Guidelines increasingly support the use of catheter ablation (CA) as an early management strategy, with the efficacy of CA crucially dependent on the extent of left atrial (LA) structural remodeling; LA imaging plays a central role in each of identifying comorbidities, risk stratification for stroke, and identification of suitable candidates for CA. An understanding of the strengths and limitations of various echocardiographic modalities, of cardiac computed tomography and of cardiac magnetic resonance imaging is therefore an increasingly important part of the armory of the electrophysiologist. In particular, individualized use of imaging to select patients more likely to benefit from CA of AF is important, and post-procedural imaging to evaluate the extent of reverse LA remodeling after CA is critical to appropriate decisions regarding ongoing anti-arrhythmic therapy and long-term anticoagulation.

Aims Pulmonary vein isolation (PVI) is the cornerstone of catheter ablation of atrial fibrillation (AF). The intervenous ridge (IVR) may be incorporated into ablation strategies to achieve PVI; however, randomized trials are lacking. We performed a randomized multi-centre international study to compare the outcomes of (i) circumferential antral PVI (CPVI) alone ( minimal ) vs. (ii) CPVI with IVR ablation to achieve individual PVI ( maximal ). Methods and results Two hundred and thirty-four patients with paroxysmal AF underwent CPVI and were randomized to a minimal or maximal ablation strategy. The primary outcome of recurrent atrial arrhythmia was assessed with 7-day Holter monitoring at 6 and 12 months. PVI was achieved in all patients. Radiofrequency ablation time was longer in the maximal group (46.6 ± 14.6 vs. 41.5 ± 13.1 min; P < 0.01), with no significant differences in procedural or fluoroscopy times. At mean follow-up of 17 ± 8 months, there was no difference in freedom from AF after a single procedure between a minimal (70%) and maximal ablation strategy (62%; P = 0.25). In the minimal group, ablation was required on the IVR to achieve electrical isolation in 44%, and was associated with a significant reduction in freedom from AF (57%) compared with the minimal group without IVR ablation (80%; P < 0.01). Conclusion There was no statistically significant difference in freedom from AF between a minimal and maximal ablation strategy. Despite attempts to achieve PVI with antral ablation, IVR ablation is commonly required. Patients in whom antral isolation can be achieved without IVR ablation have higher long-term freedom from AF (the Minimax study; ACTRN12610000863033).

Objectives This study aimed to determine the spatiotemporal stability of rotors and other atrial activation patterns over 10 min in longstanding, persistent AF, along with the relationship of rotors to short cycle-length (CL) activity. Background The prevalence, stability, and mechanistic importance of rotors in human atrial fibrillation (AF) remain unclear. Methods Epicardial mapping was performed in 10 patients undergoing cardiac surgery, with bipolar electrograms recorded over 10 min using a triangular plaque (area: 6.75 cm 2 ; 117 bipoles; spacing: 2.5 mm) applied to the left atrial posterior wall (n = 9) and the right atrial free wall (n = 4). Activations were identified throughout 6 discrete 10-s segments of AF spanning 10 min, and dynamic activation mapping was performed. The distributions of 4,557 generated activation patterns within each mapped region were compared between the 6 segments. Results The dominant activation pattern was the simultaneous presence of multiple narrow wave fronts (26%). Twelve percent of activations represented transient rotors, seen in 85% of mapped regions with a median duration of 3 rotations. A total of 87% were centered on an area of short CL activity ( Conclusions In patients with longstanding, persistent AF, activation patterns are spatiotemporally stable over 10 min. Transient rotors can be demonstrated in the majority of mapped regions, are spatiotemporally associated with short CL activity, and, when recurrent, demonstrate anatomical determinism.

Objectives This study sought to validate a 3-dimensional (3D) phase mapping system and determine the distribution of dominant propagation patterns in persistent atrial fibrillation (AF). Background Currently available systems display phase as simplified 2-dimensional maps. We developed a novel 3D phase mapping system that uses the 3D location of basket catheter electrodes and the patient’s 3D left atrial surface geometry to interpolate phase and create a 3D representation of phase progression. Methods Six-minute AF recordings from the left atrium were obtained in 14 patients using the Constellation basket catheter and analyzed offline. Exported signals underwent both phase and traditional activation analysis and were then visualized using a novel 3D mapping system. Analysis involved: 1) validation of phase analysis by comparing beat-to-beat AF cycle length calculated using phase inversion with that determined from activation timing in the same 20-s segment; 2) validation of 3D phase by comparing propagation patterns observed using 3D phase with 3D activation in the same 1-min segment; and 3) determining the distribution of dominant propagation patterns in 6-min recordings using 3D phase. Results There was strong agreement of beat-to-beat AF cycle length between activation analysis and phase inversion ( R 2 = 0.91). There was no significant difference between 3D activation and 3D phase in mean percentage of propagation patterns classified as single wavefronts (p = 0.99), focal activations (p = 0.26), disorganized activity (p = 0.76), or multiple wavefronts (p = 0.70). During prolonged 3D phase, single wavefronts were the most common propagation pattern (50.2%). A total of 34 rotors were seen in 9 of 14 patients. All rotors were transient with mean duration of 1.0 ± 0.6 s. Rotors were only observed in areas of high electrode density where the interelectrode distance was significantly shorter than nonrotor sites (7.4 [interquartile range: 6.3 to 14.6] vs. 15.3 mm [interquartile range: 10.1 to 22.2]; p Conclusions During prolonged 3D phase mapping, transient rotors were observed in 64% of patients and reformed at the same anatomic location in 44% of patients. The electrode density of the basket catheter may limit the detection of rotors.

Gender and Atrial ElectrophysiologyBackgroundGender-based differences in the clinical nature of cardiac arrhythmias such as atrial fibrillation (AF) are well established.ObjectiveThe purpose of this study was to identify any such gender-based differences in the underlying pulmonary vein and atrial substrate.Methods and ResultsThirty-eight patients with no history of AF undergoing catheter ablation for supraventricular tachycardia (SVT) and 55 with paroxysmal or persistent AF undergoing catheter ablation of AF underwent detailed electroanatomic mapping of the pulmonary veins and atria. Refractory periods in multiple locations, sinus node function, endocardial bipolar voltage, pulmonary vein and atrial conduction, and bipolar electrogram complexity were analyzed. There were no significant between-gender differences in age or other clinical variables known to impact on the atrial or pulmonary vein substrate. In neither the AF nor the non-AF cohorts were there any significant differences in atrial or pulmonary vein refractoriness, sinus node function, any measure of PV electrophysiology, or any measure of atrial electrophysiology.ConclusionNo systematic between-gender differences were observed in the PV or atrial substrate either in those with or without a history of AF, with a similar prevalence of the cardiovascular comorbidities frequently associated with atrial remodeling and AF seen in both male and female groups.

Background/Objective The purpose of this study was to characterize the association between the extent of left atrial electroanatomic remodeling in atrial fibrillation and the atrial fibrillation cycle length derived from lead V 1 of the surface ECG (V1AFCL). Methods Twenty-three patients in atrial fibrillation (AF) who presented for AF ablation underwent detailed electroanatomic mapping of the left atrium. The digital 12-lead ECG was exported for offline analysis, with signal filtering and QRST subtraction used to reveal the fibrillatory baseline in lead V 1 . Mean V1AFCL was determined by direct annotation of the fibrillatory baseline, and the corresponding dominant V1AFCL was determined by Fourier transformation to derive the dominant frequency from the frequency power spectrum. The simultaneous AFCL from proximal and distal coronary sinus recordings was determined using the same methods. The strength of the association between various left atrial remodeling variables and V1AFCL was determined. Results The 2 methods of deriving V1AFCL and intracardiac AFCL were found to produce highly equivalent results. V1AFCL showed significant correlation with intracardiac AFCL derived from both proximal and distal coronary sinus recordings. A longer V1AFCL was associated with slower left atrial conduction velocity and greater signal complexity but not with other remodeling variables, including left atrial size, atrial refractoriness, and mean endocardial voltage. Conclusion A longer atrial fibrillatory cycle length in surface ECG lead V 1 is significantly associated with parameters of more advanced left atrial electroanatomic remodeling, specifically slower atrial conduction and more extensive electrogram fractionation.

It is a source of much frustration to clinicians and patients alike that outcomes of catheter ablation for persistent atrial fibrillation (AF) remain stubbornly suboptimal.1,2 It is clearly understood that paroxysmal AF is driven in the great majority of cases by electric triggers located in myocardial sleeves extending into the pulmonary veins (PVs)3 and, built on this, a large body of evidence has been generated to demonstrate that durable PV isolation can provide effective treatment for paroxysmal AF.4 Equivalent outcomes from catheter ablation of persistent AF have been hampered by ongoing uncertainty about the basic electrophysiological mechanisms by which this arrhythmia is sustained. Article see p 554 Early data from animal and computer models suggested the presence of multiple electric wavefronts meandering through the atrial wall, after the principles of Brownian motion.5 Subsequent data have highlighted the role of atrial myocardial structural remodeling in constraining the propagation of such wavelets,6 and the importance of the 3-dimensional nature of the wall has been highlighted,7 with dissociation between endocardial and epicardial layers and wavefront breakthroughs between these layers facilitating arrhythmia maintenance. Set against this is clear evidence from high-resolution optical mapping in animal models of spiral wave re-entry sustaining fibrillation of both the ventricles8 and the atria.9,10 Multiple groups have attempted to demonstrate such spiral waves and rotors by high-density epicardial mapping in human AF but, although transient rotational activity centered on a core of high-frequency activity consistent with the electrophysiology expected of rotors has been described,11,12 there are no reports of sustained spiral wave re-entry in human persistent AF demonstrated through such methods. Exciting developments in recent years have resulted from the application of innovative mapping techniques. Multielectrode vests have been used to record body surface …

Atrial fibrillation (AF) is a common arrhythmia, with a prevalence that increases markedly with increasing age. Presence of AF has implications for management of future stroke risk. If the patient's pulse is irregular, an electrocardiogram should be ordered. Key management decisions are whether to adopt a rhythm control or a rate control strategy and whether to initiate anticoagulation. The primary aim of a rhythm control strategy is improved symptom control. AF ablation may be considered in younger patients (aged < 65 years) with paroxysmal or early persistent AF. AF increases the risk of stroke, and anticoagulation should be considered on the basis of stroke risk - clearly indicated with a CHADS 2 score (congestive heart failure, hypertension, age ≥ 75 years, diabetes, 1 point each; previous stroke or transient ischaemic attack, 2 points) of ≥ 2 - independent of the type of AF. In most patients with AF, the benefit of stroke reduction with systemic anticoagulation will outweigh its bleeding risks. All anticoagulants and antiplatelet agents increase the risk of bleeding. However, the new oral anticoagulants tend to have an improved safety profile, particularly in regard to intracranial bleeding, and are at least as effective as warfarin for stroke prevention.

Background— A common strategy for ablation of scar-based ventricular tachycardia is delivering multiple lesions in a linear pattern. Methods and Results— We tested the efficacy of a novel linear irrigated multipolar ablation catheter capable of creating linear lesions with a single application. Healthy swine underwent endocardial and epicardial linear ablation using a novel linear irrigated ablation catheter; control animals underwent focal lesions in a linear pattern over 3.5 cm with an irrigated radiofrequency catheter. The linear catheter contained 7 irrigated electrodes spaced over 3.5 cm and could deliver ≤25 W to each electrode. Linear ablation required significantly less radiofrequency time than focal ablation (56±11 versus 497±110 seconds; P P 3 ; P =0.002). There was no difference between linear (n=22) and focal (n=7) endocardial line length or volume. Gaps (length 2.8±0.9 mm) were present in 53% of focal lines and 0% of linear ablation lines. No perforations, steam pops, or thrombus were noted. Conclusions— Compared with sequential focal radiofrequency ablation in a linear pattern, an irrigated multipolar linear ablation catheter safely delivers contiguous endocardial or epicardial lesions without gaps in a single ablation. This catheter shows promise for decreasing ventricular tachycardia ablation procedure time and improving outcome.

Medical care of heart failure (HF) begins with the determination of the cause of the heart failure and diagnosing potential reversible causes (i.e., coronary heart disease, hyperthyroidism, etc.). Medical therapy includes pharmacological and nonpharmacological strategies that limit and/or reverse the signs and symptoms of HF. Initial behavior modification includes dietary sodium and fluid restriction to avoid weight gain; and encouraging physical activity when appropriate. Optimization of medical therapy is the first line of treatment that includes the use of diuretics, vasodilators (i.e., ACE inhibitors or ARBs), beta blockers, and potentially inotropic agents and anticoagulation depending on the patient's severity of heart failure and LV dysfunction. As heart failure advances despite optimized medical management, cardiac resynchronization therapy (CRT), and implantable cardioverter defibrillators (ICDs) are appropriate device therapies. The development of progressive end-stage HF, despite maximal medical therapy, necessitates the consideration of mechanical circulatory devices such as ventricular assist devices (VADs) either as a bridge to heart transplantation or as destination therapy. Despite the advances in the treatment of heart failure, there is still a large morbidity and mortality associated with HF, thus the need to develop newer strategies for the treatment of HF.

Aims: Catheter ablation to achieve posterior left atrial wall (PW) isolation may be performed as an adjunct to pulmonary vein isolation (PVI) in patients with persistent atrial fibrillation (AF). We aimed to determine whether routine adenosine challenge for dormant posterior wall conduction improved long-term outcome. Methods and results: A total of 161 patients with persistent AF (mean age 59 +/- 9 years, AF duration 6 +/- 5 years) underwent catheter ablation involving circumferential PVI followed by PW isolation. Posterior left atrial wall isolation was performed with a roof and inferior wall line with the endpoint of bidirectional block. In 54 patients, adenosine 15 mg was sequentially administered to assess reconnection of the pulmonary veins and PW. Sites of transient reconnection were ablated and adenosine was repeated until no further reconnection was present. Holter monitoring was performed at 6 and 12 months to assess for arrhythmia recurrence. Posterior left atrial wall isolation was successfully achieved in 91% of 161 patients (procedure duration 191 +/- 49 min, mean RF time 40 +/- 19 min). Adenosine-induced reconnection of the PW was demonstrated in 17%. The single procedure freedom from recurrent atrial arrhythmia was superior in the adenosine challenge group (65%) vs. no adenosine challenge (40%, P < 0.01) at a mean follow-up of 19 +/- 8 months. After multiple procedures, there was significantly improved freedom from AF between patients with vs. without adenosine PW challenge (85 vs. 65%, P = 0.01).Conclusion Posterior left atrial wall isolation in addition to PVI is a readily achievable ablation strategy in patients with persistent AF. Routine adenosine challenge for dormant posterior wall conduction was associated with an improvement in the success of catheter ablation for persistent AF.

A young woman with placement of a dual-chamber implantable cardioverter-defibrillator (ICD) and a history of prior cardiac arrest due to congenital long QT syndrome presented with defibrillation caused by a ventricular fibrillation arrest. Routine device interrogation revealed significant lead dysfunction. During device revision, breaches were detected in the insulation of both leads within the pre-pectoral pocket and an “arc mark” was observed on the ICD generator casing; these findings were consistent with a high-voltage discharge through a short circuit between the denuded right ventricular lead and the casing. In this case, system failure was unmasked only by interrogation after appropriate device activation, which highlights the importance of thorough evaluation after all ICD activations.

Mechanisms sustaining human persistent atrial fibrillation (AF) remain debated, with significant differences between high-density epicardial and global endocardial mapping studies. A key difference is the density of recording electrodes.We aimed to determine the differences in the prevalence of different atrial activation patterns, and specifically in the prevalence of rotational activations, with varying densities of bipolar electrodes.Epicardial mapping was performed in 10 patients undergoing cardiac surgery, with bipolar electrograms recorded using a triangular plaque (6.75 cm(2) area; 117 bipoles; 2.5-mm inter-bipole spacing) applied to the left atrial posterior wall or right atrial free wall. Dynamic wavefront mapping based on the timing of atrial electrograms was applied to 2 discrete 10-second AF segments. The spacing between bipolar electrode locations was increased from 2.5 × 3.5 mm in the horizontal and oblique directions to 5.0 × 3.5, 5.0 × 7.1, and 7.5 × 10.6 mm, with wavefront mapping repeated at each density.As density reduced, there was a significant change in relative proportions of the various activation patterns (F=3.69; P.001). Simple broad wavefront activations became more prevalent (20% ± 8% to 54% ± 8%; P.05) and complex patterns became less prevalent (48% ± 8% to 9% ± 8%; P.05) with reducing density. The prevalence of rotational activity declined with bipole density, from median 5.0% (range 0.9%-12.1%) to 0% (range 0%-1.5%) (P = .03). The largest change occurred between inter-bipole spacings of 5.0 × 3.5 and 5.0 × 7.1 mm.Apparent activation patterns in persistent AF vary significantly with electrode density. Low density underestimates the prevalence of complex and rotational patterns. The largest difference occurs between an inter-bipole spacing of 5.0 × 3.5 and a spacing of 5.0 × 7.1 mm. This may have important implications for mapping technology design.