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Objectives: The study was done to characterize the electrocardiographic and electrophysiologic features of focal atrial tachycardia originating at the mitral annulus (MA)., Background: Though the majority of left atrial tachycardias originate around the ostia of the pulmonary veins, only isolated reports have described focal tachycardia originating from the MA., Methods: Seven patients of a consecutive series of 172 patients undergoing radiofrequency ablation for focal atrial tachycardia are reported. Electrophysiologic study involved catheters positioned along the coronary sinus (CS), crista terminalis (CT), His bundle, and a mapping/ablation catheter., Results: All seven patients had tachycardia foci originating from the superior region of the MA in close proximity to the left fibrous trigone and mitral-aortic continuity. These foci demonstrated a characteristic P-wave morphology and endocardial activation pattern. The P-wave morphology in the precordial leads typically showed a biphasic pattern, with an inverted component followed by an upright component. The P-wave was consistently of low amplitude in the limb leads. Earliest endocardial activity occurred at the His bundle region in all seven patients. In general, CS activation was proximal to distal, and mid-CT activation was earlier than high or low CT. Ablation was successful at the superior aspect of the MA in all patients., Conclusions: The MA is an unusual but important site of origin for focal atrial tachycardia, with a propensity to be localized to the superior aspect. It can be suspected as a potential anatomic site of tachycardia origin from analysis of P-wave morphology and the atrial endocardial activation sequence map. Using mapping targeted to anatomic structures achieved a high success rate for ablation.

The article offers information on gastric autonomic activity and atrial fibrillation (AF) susceptibility in gastroesophageal reflux disease. It mentions information on association between gastroesophageal reflux disease (GERD) and AF; and also mentions about acute electrophysiological changes in atrial refractoriness and associated increased inducibility of AF in an animal model of GERD.

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The article offers a commentary on a study on atrial fibrillation (AF) frequency mapping using continuous wavelet transform (CWT). Topics covered include the need to determine the substrate responsible for AF specific to individual patient for a more targeted ablative therapy, costs associated with mapping techniques using basket-type catheter and non-invasive body surface electrodes, and the utility of CWT frequency analysis versus fast-Fourier transform (FFT)-derived dominant frequency (DF).

Background: Rotors are postulated to maintain cardiac fibrillation. Despite the importance of bipolar electrograms in clinical electrophysiology, few data exist on the properties of bipolar electrograms at rotor sites. The pivot of a spiral wave is characterized by relative uncertainty of wavefront propagation direction compared to the periphery. The bipolar electrograms used in electrophysiology recording encode information on both direction and timing of approaching wavefronts. Objective: To test the hypothesis that bipolar electrograms from the pivot of rotors have higher Shannon entropy (ShEn) than electrograms recorded at the periphery due to the spatial dynamics of spiral waves. Methods and Results: We studied spiral wave propagation in 2-dimensional sheets constructed using a simple cell automaton (FitzHugh-Nagumo), atrial (Courtemanche-Ramirez-Nattel) and ventricular (Luo-Rudy) myocyte cell models and in a geometric model spiral wave. In each system, bipolar electrogram recordings were simulated, and Shannon entropy maps constructed as a measure of electrogram information content. ShEn was consistently highest in the pivoting region associated with the phase singularity of the spiral wave. This property was consistently preserved across; (i) variation of model system (ii) alterations in bipolar electrode spacing, (iii) alternative bipolar electrode orientation (iv) bipolar electrogram filtering and (v) in the presence of rotor meander. Directional activation plots demonstrated that the origin of high ShEn at the pivot was the directional diversity of wavefront propagation observed in this location. Conclusions: The pivot of the rotor is consistently associated with high Shannon entropy of bipolar electrograms despite differences in action potential model, bipolar electrode spacing, signal filtering and rotor meander. Maximum ShEn is co-located with the pivot for rotors observed in the bipolar electrogram recording mode, and may be an intrinsic property of spiral wave dynamic behaviour. [ABSTRACT FROM AUTHOR]

QT variability (QTV) signifies repolarization lability, and increased QTV is a risk predictor for sudden cardiac death. The aim of the present study was to investigate the role of autonomic nervous system activity on QTV. This study was performed in 29 subjects: 10 heart failure (HF) patients with spontaneous ventricular tachycardia [HFVT(+)], 10 HF patients without spontaneous VT [HFVT(-)], and 9 subjects with structurally normal hearts (HNorm). The beat-to-beat QT interval was measured on 3-min records of surface ECGs at baseline and during interventions (atrial pacing and esmolol, isoprenaline, and atropine infusion). Variability in QT intervals was expressed as the SD of all QT intervals (SDQT). The ratio of the SDQT to SD of RR intervals (SDRR) was calculated as an index of QTV normalized to heart rate variability. There was a trend toward a higher baseline SDQT-to-SDRR ratio in the HFVT(+) group compared with the HFVT(-) and HNorm groups (P = 0.09). SDQT increased significantly in the HFVT(+) and HFVT(-) groups compared with the HNorm group during fixed-rate atrial pacing (P = 0.008). Compared with baseline, isoprenaline infusion increased SDQT in HNorm subjects (P = 0.02) but not in HF patients. SDQT remained elevated in the HFVT(+) group relative to the HNorm group despite acute β-adrenoceptor blockade with esmolol (P = 0.02). In conclusion, patients with HF and spontaneous VT have larger fluctuations in beat-to-beat QT intervals. This appears to be a genuine effect that is not solely a consequence of heart rate variation. The effect of acute autonomic nervous system modulation on QTV appears to be limited in HF patients. [ABSTRACT FROM AUTHOR]

Background: Both ageing and hypertension are known risk factors for atrial fibrillation (AF) although the pathophysiological contribution or interaction of the individual factors remains poorly understood. Here we aim to delineate the arrhythmogenic atrial substrate in mature spontaneously hypertensive rats (SHR). Methods: SHR were studied at 12 and 15 months of age (n = 8 per group) together with equal numbers of age-matched normotensive Wistar-Kyoto control rats (WKY). Electrophysiologic study was performed on superfused isolated right and left atrial preparations using a custom built high-density multiple-electrode array to determine effective refractory periods (ERP), atrial conduction and atrial arrhythmia inducibility. Tissue specimens were harvested for structural analysis. Results: Compared to WKY controls, the SHR demonstrated: Higher systolic blood pressure (p<0.0001), bi-atrial enlargement (p<0.05), bi-ventricular hypertrophy (p<0.05), lower atrial ERP (p = 0.008), increased atrial conduction heterogeneity (p = 0.001) and increased atrial interstitial fibrosis (p = 0.006) & CD68-positive macrophages infiltration (p<0.0001). These changes resulted in higher atrial arrhythmia inducibility (p = 0.01) and longer induced AF episodes (p = 0.02) in 15-month old SHR. Ageing contributed to incremental bi-atrial hypertrophy (p<0.01) and atrial conduction heterogeneity (p<0.01) without affecting atrial ERP, fibrosis and arrhythmia inducibility. The limited effect of ageing on the atrial substrate may be secondary to the reduction in CD68-positive macrophages. Conclusions: Significant atrial electrical and structural remodeling is evident in the ageing spontaneously hypertensive rat atria. Concomitant hypertension appears to play a greater pathophysiological role than ageing despite their compounding effect on the atrial substrate. Inflammation is pathophysiologically linked to the pro-fibrotic changes in the hypertensive atria. [ABSTRACT FROM AUTHOR]

The article investigates whether bipolar electrogram Shannon entropy (ShEn), a measure of signal amplitude distribution, could differentiate the pivot from surrounding peripheral regions and thereby assist clinical rotor mapping of atrial fibrillation (AF). The study covered bipolar electrogram recordings in computer simulation, isolated rat atria, epicardial recordings of induced AF in sheep and persistent AF patients. Results suggested that ShEn may assist AF rotor mapping.

The article studies an externally irrigated magnetic resonance imaging (MRI)-compatible ablation catheter and integrated electrophysiology (EP) pacing and recording system. The researchers conducted lesion visualization using noncontrast and gadolinium-diethylene triamine pentaacetic acid-enhanced T1-weighted imaging. Results show the feasibility of using multiple catheters, integrated EP pacing and recording system and externally irrigated ablation in biatrial mapping and ablation.

AF in WPW Syndrome. Aim: We aimed to characterize electrophysiological properties of pulmonary veins (PVs) in patients with Wolff-Parkinson-White (WPW) syndrome and atrial fibrillation (AF), and to compare them to those in patients with WPW without AF. Methods and Results: A total of 31 patients (mean age 40 ± 15 years, 23 males) with WPW were recruited: 16 patients with (AF group) and 15 without (controls) a history of AF. The basic electrophysiological (EPS) and echocardiographic data were not different between the 2 groups. Effective refractory periods (ERPs) of PVs were significantly shorter in the AF group compared to controls: left superior (LS) PV ERP 185±29 versus 230 ± 24 ms, P = 0.001; left inferior PV ERP 198 ± 25 versus 219 ± 26 ms, P = 0.04; right superior (RS) PV ERP 207 ± 25 versus 236 ± 19 ms, P = 0.001; right inferior PV ERP 208 ± 30 versus 240 ± 19 ms, P = 0.003. Maximal veno-atrial conduction delay (i.e., the maximal prolongation of interval from stimulus delivered at PV ostia to proximal coronary sinus after extrastimulus compared to the basic drive cycle) was longer in the AF group when pacing from LSPV (69.3 ± 37.9 vs 32.6 ± 16.1 ms, P = 0.01) and RSPV (74.1 ± 25.9 vs 50.2 ± 26.5 ms, P = 0.04). During EPS, AF was induced more often in the AF group (n = 7) compared to controls (n = 1; P = 0.04). Follow-up revealed that AF recurred in 3 patients in the AF group and none of the controls. Conclusion: Patients with WPW syndrome and AF have shorter ERPs of PVs and greater maximal veno-atrial conduction delay compared to patients with WPW without AF. These findings suggest a potential role of PVs in the development of AF in patients with WPW. (J Cardiovasc Electrophysiol, Vol. 23 p. 280-286, March 2012.) [ABSTRACT FROM AUTHOR]

Electroanatomic Properties of the Pulmonary Veins. Introduction: Rapid PV activity is critical in initiating and maintaining AF. The underlying substrate responsible for this remains uncertain. We sought to identify if patients with paroxysmal (PAF) and persistent atrial fibrillation (PeAF) have an abnormal substrate within the pulmonary veins (PVs). Methods and Results: Thirty-nine patients with AF (21 PAF, 18 PeAF) were compared with 15 age-matched controls with left-sided accessory pathways (AVRT). High-density 3D electroanatomic maps of the PVs were created. PV voltage, conduction, PV muscle sleeve length, effective refractory periods (ERPs) of the PVs, posterior left atrium (PLA), left atrial appendage (LAA) and distal coronary sinus (CSd), and signal complexity were assessed. Compared with controls, the PVs of AF patients had (1) lower mean-voltage and a higher % low-voltage; (2) shorter PV muscle sleeves; (3) slower conduction; (4) shorter ERP; and (5) more prevalent complex signals. Compared with the PAF group, the PeAF group had (1) higher % low voltage; (2) slower conduction; and (3) more complex signals. In PAF patients, the PLA and LAA ERPs were longer than controls and the PV ERP was shorter than controls; in PeAF patients PLA and LAA ERPs were reduced, but to a lesser extent than in the PVs. AF induction occurred during PV ERP testing in both AF groups, but not controls. Conclusions: PAF and PeAF patients demonstrate electrical and electroanatomic remodeling of the PVs compared to control patients without prior AF. Some of these changes were more marked in PeAF. (J Cardiovasc Electrophysiol, Vol. 22, pp. 1083-1091, October 2011) [ABSTRACT FROM AUTHOR]

All preclinical studies of atrial remodeling in heart failure (HF) have been confined to a single model of rapid ventricular pacing. To evaluate whether the atrial changes were specific to the model or represented an end result of HF, this study aimed to characterize atrial remodeling in an ovine model of doxorubicin-induced cardiomyopathy. Fourteen sheep, 7 with cardiomyopathy induced by repeated intracoronary doxorubicin infusions and 7 controls, were studied. The development of HF was monitored by cardiac imaging and hemodynamic parameters. Open chest electrophysiological study was performed using custom-made 128-electrode epicardial plaque assessing effective refractory period (ERP) and conduction velocity. Atrial tissues were harvested for structural analysis. The HF group had demonstrable moderate global HF (left ventricular ejection fraction [LVEF]: 37.1 vs 46.4%; P = 0.003) and showed the following compared to controls: left atrial dilatation (P = 0.02) and dysfunction (P = 0.005); longer P-wave duration (P < 0.05); higher ERP at all cycle lengths (P ≤ 0.002) and locations (P < 0.001); slower conduction velocity (P < 0.001); increased conduction heterogeneity index (P < 0.001); increased atrial fibrosis (right atrial [RA]: 5.9 ± 2.6 vs 2.8 ± 0.9%; P < 0.0001, left atrial [LA]: 3.7 ± 2.2 vs 2.4 ± 1.1%; P = 0.002), and longer induced atrial fibrillation (AF) episodes (16 ± 22 vs 2 ± 3 seconds; P = 0.04). In this model of HF, there was significant atrial remodeling characterized by atrial enlargement/dysfunction, increased fibrosis, slowed/heterogeneous conduction, and increased refractoriness associated with more sustained AF. These findings appear the 'same sort' to previous models of HF implicating a final common substrate leading to the development of AF in HF. (J Cardiovasc Electrophysiol, Vol. 22, pp. 175-182, February 2011) [ABSTRACT FROM AUTHOR]

1. High-density cardiac electrophysiological study (EPS) of small animal atria has been limited to optical mapping techniques, which require complex and expensive equipment setup. We aim to evaluate the feasibility of carrying out EPS in isolated atrial tissues using a custom made high-density multiple-electrode array (MEA). 2. Isolated rat atrial preparations were studied. The MEA (4 × 5 mm) consisted of 90 silver chloride coated electrodes (0.1 mm diameter, 0.5 mm pitch) and was connected to a conventional EP system yielding 80 bipolar signals. Atrial tissues were placed over the MEA in a dish bubbled with 100% oxygen and superfused with modified HEPES solution at pH 7.35 and 37°C. Then, 1 mmol of 2,3-butanedione monoxime was added to suppress motion artifacts from muscle contractions. Custom plaque analysis software was used for offline conduction analysis. 3. Isolated atrial tissues showed good viability of > 30 min, allowing ample time for complete EPS. High quality electrograms with excellent signal to noise ratio were obtained. All electrophysiological parameters showed good reproducibility: effective refractory period, conduction velocity and heterogeneity index. Tachycardia was also inducible in these normal atria. 4. The present study shows the feasibility of performing high-density EPS of small isolated atrial tissues with a conventional electrode-based technique. The MEA system is compatible with standard electrophysiology recording systems and provides a novel, inexpensive option for detailed EPS in small animal models. In particular, it presents new research avenues to further explore the mechanisms of atrial arrhythmias in various transgenic and knockout rodent models. [ABSTRACT FROM AUTHOR]

Background: Chronic pulmonary disease and sleep apnea have been associated with the development of atrial fibrillation (AF). Objective: The purpose of this study was to characterize the atrial electrical changes that occur with hypercapnia and hypoxemia and to determine their role in AF development. Methods: Seventeen sheep (6 control, 5 hypercapnia, 6 hypoxemia) underwent open chest electrophysiologic evaluation under autonomic blockade. A 64-electrode endocardial basket catheter was positioned in the right atrium, and 2 × 128 electrode epicardial plaques were sutured to the right atrial and left atrial appendages to determine atrial refractoriness (effective refractory period [ERP]) at 9 sites and 5 cycle lengths, conduction time to fixed points on each plaque, and AF vulnerability. Results: Hypercapnia was associated with a 152% lengthening of ERP from baseline and increased conduction time. ERPs rapidly returned to baseline, but recovery of conduction was delayed at least 117 ± 24 minutes following resolution of hypercapnia. AF vulnerability was reduced during hypercapnia (with increased ERP) but increased significantly with subsequent return to eucapnia (when ERP normalized but conduction time remained prolonged). No significant changes in ERP, atrial conduction time, or AF vulnerability occurred in hypoxemic or control groups. Conclusion: Differential recovery of ERP and conduction that occurs following hypercapnia might account for the increased vulnerability to AF observed in the phase after return to eucapnia. This may explain in part the increased prevalence of AF in pulmonary disease and sleep apnea. [ABSTRACT FROM AUTHOR]

Background: Abstract presentation at conferences provides the opportunity to rapidly communicate research findings. The outcome and impact of publications arising from cardiac electrophysiology abstracts are not known. Objective: The purpose of this study was to examine the characteristics of abstracts presented at the annual scientific sessions of Heart Rhythm Society (HRS), their publication rate, and the indexed impact of subsequent publications. Methods: Two independent database searches (MEDLINE and EMBASE) were performed by cross-referencing authors and keywords from abstracts originally presented at HRS in 2003. ISI Web of Knowledge was accessed for impact factors and citation rates. Results: A total of 790 abstracts were presented, of which 377 (47.7%) resulted in publication of an original article. Median time to publication was 1.39 years (interquartile range [IQR] 0.88–2.30 years), and the median impact factor and citation rate of published articles was 4.14 (IQR 3.48–11.05) and 10 (IQR 4–25), respectively. Experimental research abstract category (odds ratio [OR] 2.03, P <.001), randomized study design (OR 0.53, P = .02), and positive findings (OR 0.80, P = .06) were independently predictive of publication by stepwise logistic regression. Independent predictors of higher citation rates were randomized study design (P = .03) and impact factor of the publishing journal (P <.001). Conclusion: Almost half of all abstracts presented at HRS resulted in publication in journals with a high impact factor. Experimental research abstracts, those with a randomized study design, and those demonstrating positive findings were predictors of subsequent publication. Randomized study design and greater impact factor of the publishing journal were found to predict higher citation rates. [Copyright &y& Elsevier]

Introduction: Sites of complex fractionated atrial electrograms (CFAE) and dominant frequency (DF) have been implicated in maintaining atrial fibrillation (AF); however, their relationship is poorly understood. Methods and Results: Twenty patients underwent biatrial high-density contact mapping (507 ± 150 points/patient) during AF. CFAE were characterized using software to quantify electrogram complexity (CFE-mean). Spectral analysis determined the frequency with greatest power and sites of high DF with a frequency gradient. CFE-mean was higher (less fractionated) for right compared with left atria (P < 0.001) and in paroxysmal compared with persistent AF (P < 0.001). DF was lower for right compared with left atria (P = 0.02) and in paroxysmal compared with persistent AF (P < 0.001). There was significant regional variation in DF in paroxysmal (P < 0.001) but not persistent AF. Highest DF points clustered together with 5.2 ± 1.7 clusters/patient. Correlation between CFE-mean and DF was poor on a point-by-point basis (r =−0.17, P < 0.001), but moderate on an individual basis (r =−0.50, P = 0.03). Exploration of their spatial relationship demonstrated CFAE areas in close proximity (median 5 mm, IQR 2–10) to high DF sites; within 10 mm in 80% and 10–20 mm in 10%. Simultaneous activation mapping at these sites further supports this observation. Conclusion: Greater fractionation and higher DF are seen in persistent AF and left atria during AF. Preferential areas of high DF are observed in paroxysmal but not persistent AF. CFAE and DF correlate within an individual but not point-by-point. Exploration of their spatial relationship demonstrates CFAE in areas adjacent to high DF, and this is supported by activation mapping at these sites. [ABSTRACT FROM AUTHOR]

Introduction: Sites of complex fractionated atrial electrograms (CFAEs) and highest dominant frequency (DF) have been proposed as critical regions maintaining atrial fibrillation (AF). This study aimed to determine the minimum electrogram recording duration that accurately characterizes CFAE or DF sites for ablation without unduly lengthening the procedure. Methods and Results: Fourteen patients with AF undergoing catheter ablation had high-density (498 ± 174 points) biatrial mapping performed during AF before ablation. At each point, 8-second electrograms were recorded. CFAE characterization using the NavX software provided a representation of electrogram complexity (CFE-mean). CFE-mean for each point from 7-, 6-, 5-, 4-, 3-, 2-, and 1-second subsamples were compared with the index 8-second CFE-mean. Offline spectral analysis defined DF as the frequency with greatest power, and DF of subsamples were compared with index DF. Index 8-second electrogram CFE-mean was 114 ± 20 ms for right atria and 102 ± 17 ms for left atria (P = 0.01); DF was 5.7 ± 0.8 Hz for right atria and 6.0 ± 0.8 Hz for left atria (P = 0.02). Means from shorter electrograms were nonsignificantly decreased for CFE-mean and overestimated for DF (P < 0.001). Mean absolute differences between subsampled and index values ranged from 3.3 to 20.1 ms for CFE-mean and 0.11 to 1.18 Hz for DF. Subsampled electrograms deviating >10% from index values ranged from 2.5 to 56% for CFE-mean and 3.5 to 41% for DF. Intraclass correlation coefficients ranged from 0.992 to 0.788 for CFE-mean and 0.897 to 0.233 for DF. Unacceptable differences from index values were found with CFE-mean and DF from electrograms <5 seconds. Conclusion: Electrograms of ≥5-second duration are required to accurately characterize CFAE and DF sites for ablation. [ABSTRACT FROM AUTHOR]

Sinus node disease was previously thought to be a disease limited to the sinus node and its atrial connections. However, recent reports have demonstrated sinus node disease as a disease of the entire right atrial myocardium. These patients have widespread electrophysiological abnormalities of their atria, including prolonged refractory periods and slowed conduction. In addition to these electrical changes, there are significant structural changes, such as fibrosis and fatty infiltration, which can be detected endocardially as regions of fractionated signals, low-voltage electrograms, and electrically silent areas. In most cases, the etiology of these changes is unknown. These changes may contribute to the high prevalence of atrial fibrillation seen in patients with sinus node disease. [Copyright &y& Elsevier]

Pulmonary vein (PV) arrhythmogenicity underlying the maintenance of atrial fibrillation (AF) may be explained by three mechanisms: enhanced automaticity, triggered activity, and reentry. There are only a few reports describing sustained PV tachycardias (PVT) following electrical disconnection from the left atrium, in which the electrophysiological features are most consistent with a reentrant mechanism. We describe the case of a patient with paroxysmal AF demonstrating PVT within an isolated PV with high-density mapping revealing two different PVTs interacting in a “ping-pong” manner. [ABSTRACT FROM AUTHOR]

Background: Chronic atrial fibrillation (CAF) can be acutely terminated using a combination of approaches targeting thoracic veins, left atrial areas showing rapid/heterogeneous electrical activity, and by linear ablation. This observational study emphasizes the crucial role for conventional endocardial mapping to identify discrete anatomical sites, ablation of which is indispensable for the achievement of atrial fibrillation (AF) termination. Methods: Eighty consecutive patients with CAF underwent catheter ablation using the stepwise approach. Pulmonary vein isolation and roof-line ablation were performed as the initial two steps in all patients. In the presence of locally rapid or heterogeneous activity, ablation was then performed at all sites within the left atrium and coronary sinus (CS) region with the endpoint of local organization or slowing. If AF persisted, the mitral isthmus was targeted. Patients in whom AF terminated during one of these five ablation steps were differentiated from those in whom AF was terminated by radiofrequency ablation at a single discrete anatomic site within 1 minute. Electrograms at discrete anatomic sites of termination were classified according to morphology. Results: Termination of AF was achieved in 69 (86%) patients by ablation alone. In 50 patients (72%), this occurred while following the predetermined ablation schema. In the remaining 19 patients (28%), ablation targeting a discrete site (preferentially located at the CS, the base of left atrial appendage, and the interatrial septum) terminated AF. Such sites were identified by (1) continuous electrical activity and fractionation and (2) bursts of short cycle activity (130–160 msec), centrifugal activation or local activation gradients, indicating sources perpetuating AF. Conclusion: In 28% of patients with termination of CAF, the final successful ablation site is anatomically discrete and displays electrophysiological characteristics that can be effectively identified by point and activation mapping. Failure to identify these sites may significantly reduce the likelihood of termination of CAF by catheter ablation. [ABSTRACT FROM AUTHOR]

Background: Left atrial (LA) linear lesions are effective in substrate modification for atrial fibrillation (AF). However, achievement of complete conduction block remains challenging and conduction recovery is commonly observed. The aim of the study was to investigate the localization of gap sites of recovered LA linear lesions. Methods and Results: Forty-eight patients with paroxysmal (n = 26) and persistent/permanent (n = 22) AF underwent repeat ablation after pulmonary vein (PV) isolation and LA linear ablation at the LA roof and/or mitral isthmus due to recurrences of AF or flutter. In 35 patients, conduction through the mitral isthmus line (ML) had recovered whereas roof-line recovery was observed in 30 patients. The gaps within the ML were distributed to the junction between left inferior PV and left atrial appendage in 66%, the middle part of the ML in 20%, and in 8% to the endocardial aspect of the ML while only 6% of lines showed an epicardial site of recovery. The RL predominantly recovered close to the right superior PV (54%) and less frequently in the mid roof or close to the left PV (both 23%). Reablation of lines required significantly shorter RF durations (ML: 7.24 ± 5.55 minutes vs 24.08 ± 9.38 minutes, RL: 4.24 ± 2.34 minutes vs 11.54 ± 6.49 minutes; P = 0.0001). Patients with persistent/permanent AF demonstrated a significantly longer conduction delay circumventing the complete lines than patients with paroxysmal AF (228 ± 77 ms vs 164 ± 36 ms, P = 0.001). Conclusions: Gaps in recovered LA lines were predominantly located close to the PVs where catheter stability is often difficult to achieve. Shorter RF durations are required for reablation of recovered linear lesions. Conduction times around complete LA lines are significantly longer in patients with persistent/permanent AF as compared to patients with paroxysmal AF. [ABSTRACT FROM AUTHOR]

Background: Noninducibility of sustained atrial fibrillation (AF) after pulmonary vein isolation (PVI) has been shown to be associated with a better clinical outcome. We evaluated the role of clinical variables that could predict noninducibility of sustained AF after PVI. Methods and Results: Data were collected prospectively from 181 patients (153 male; age 54 ± 9 years) referred for ablation of drug-refractory symptomatic paroxysmal AF (duration ≤7 days). Clinical variables were evaluated with regard to their ability of predicting noninducibility of sustained AF (≤10 minutes) after PVI. Univariate analysis was performed on all collected variables followed by multivariate analysis for variables showing a P value <0.1. After PVI, sustained AF was noninducible in 97 (54%) patients. The following clinical variables showed a significant difference between the groups: body weight, longest AF episode, duration of AF history, presence or absence of structural heart disease, left ventricular (LV) hypertrophy, prior cardioversion, left atrial (LA) parasternal, and longitudinal diameters and LV diameters. On multivariate analysis, three independent predictors of noninducibility were identified: a shorter duration of AF episodes (AF <12 hours: RR 0.01 (0.002–0.06), P < 0.001; AF 12–48 hours: RR 0.07 (0.01–0.37), P = 0.001); LA longitudinal diameter <57 mm (RR 0.33 (0.13–0.82), P = 0.016); and absence of LV hypertrophy (RR 0.15 (0.04–0.63), P = 0.01). Conclusions: Shorter AF episodes, smaller LA longitudinal diameter, and absence of LV hypertrophy are independent predictors of noninducibility of sustained AF after PVI. [ABSTRACT FROM AUTHOR]

Background: The relative contributions of different atrial regions to the maintenance of persistent atrial fibrillation (AF) are not known. Methods: Sixty patients (53 ± 9 years) undergoing catheter ablation of persistent AF (17 ± 27 months) were studied. Ablation was performed in a randomized sequence at different left atrial (LA) regions and comprised isolation of the pulmonary veins (PV), isolation of other thoracic veins, and atrial tissue ablation targeting all regions with rapid or heterogeneous activation or guided by activation mapping. Finally, linear ablation at the roof and mitral isthmus was performed if sinus rhythm was not restored after addressing the above-mentioned areas. The impact of ablation was evaluated by the effect on the fibrillatory cycle length in the coronary sinus and appendages at each step. Activation mapping and entrainment maneuvers were used to define the mechanisms and locations of intermediate focal or macroreentrant atrial tachycardias. Results: AF terminated in 52 patients (87%), directly to sinus rhythm in 7 or via the ablation of 1–6 intermediate atrial tachycardias (total 87) in 45 patients. This conversion was preceded by prolongation of fibrillatory cycle length by 39 ± 9 msec, with the greatest magnitude occurring during ablation at the anterior LA, coronary sinus and PV-LA junction. Thirty-eight atrial tachycardias were focal (originating dominantly from these same sites), while 49 were macroreentrant (involving the mitral or cavotricuspid isthmus or LA roof). Patients without AF termination displayed shorter fibrillatory cycles at baseline: 130 ± 14 vs 156 ± 23 msec; P = 0.002. Conclusion: Termination of persistent AF can be achieved in 87% of patients by catheter ablation. Ablation of the structures annexed to the left atrium—the left atrial appendage, coronary sinus, and PVs—have the greatest impact on the prolongation of AF cycle length, the conversion of AF to atrial tachycardia, and the termination of focal atrial tachycardias. [ABSTRACT FROM AUTHOR]

Aims Anatomical and wide atrial encircling of the pulmonary veins (PVs) has been proposed as a cure of atrial fibrillation (AF). We evaluated the acute achievement of electrical PV isolation using this approach. In addition, the consequences of wide encircling of the PVs with isolation were assessed. [ABSTRACT FROM PUBLISHER]

Objectives: The purpose of this study was to characterize the pattern of atrial remodeling seen with human aging.Background: Atrial fibrillation (AF) occurs in 3% to 4% of the population over 65 years of age. It is associated with thromboembolic complications, worsening heart failure, and increased mortality, yet the electrical and structural remodeling that occurs with human aging remains unknown.Methods: Thirteen patients (66.4 ± 1.7 years) ≥60 years (group A), 13 patients (50 ± 2.1 years) age 31 to 59 years (group B), and 15 patients (24.7 ± 1.0 years) ≤30 years (group C) underwent conventional electrophysiologic studies and electroanatomic mapping. We measured atrial refractoriness (ERP) at the distal coronary sinus (CS); low and high lateral right atrium (LRA) and the high septal right atrium at 600, 500, and 400 ms; maximum corrected sinus node recovery time (CSNRT); P-wave duration (PWD); conduction time (CT) along the CS and LRA; and discrete double potentials (DP) along the crista.Results: Aging was associated with an increase in atrial ERP, prolonged CT along the CS, increased PWD and CSNRT. There was no significant change in dispersion of refractoriness or rate adaptation. Electroanatomic mapping revealed diffuse areas of low voltage with regional conduction slowing. Both techniques demonstrated a greater number of DPs and fractionated signals along the crista terminalis with aging.Conclusions: Aging is associated with regional conduction slowing, anatomically determined conduction delay at the crista, and structural changes that include areas of low voltage. In addition, impairment of sinus node function and an increase in atrial ERP occurred with aging. This electrical and structural remodeling may explain the increased propensity to AF with aging. [Copyright &y& Elsevier]

Objectives: To evaluate the feasibility and outcome of ablation to transect the anterior left atrium (LA) in patients with atrial fibrillation (AF).Background: While the Maze procedure is effective in maintaining sinus rhythm in patients with AF, it is associated with significant morbidity. This prospective clinical study evaluates the feasibility and consequences of limited LA linear ablation to transect the anterior LA in patients with AF.Methods: Twenty-four patients (51.2 +/- 7.3 years) with paroxysmal (n = 16) or chronic (n = 8) AF resistant to pulmonary vein (PV) isolation were studied. To transect the anterior LA, linear ablation was performed joining the superior PVs; this line was then connected to the anterior mitral annulus. Pulmonary vein isolation and cavotricuspid isthmus ablation were performed in all cases. Ablation was performed using an irrigated catheter with the endpoint of achieving complete linear block demonstrated by online double potentials, differential pacing techniques, and an activation detour.Results: Of 20 patients in AF prior to linear ablation, arrhythmia terminated in 12 (60%), including half the patients with chronic AF, during ablation. Despite repeated ablation, complete linear block was achieved in only 14 of 24 patients (58%). Complete linear conduction block resulted in an activation detour around the mitral annulus and PVs with a delay of 158 +/- 30 ms (P = .0001), significantly delayed activation of the lateral LA with prolongation of P-wave duration (P = .002), and characteristic change in P-wave morphology during sinus rhythm (P = .002). Of the 14 with anterior LA transection, 4 (29%) have had regular atrial tachycardias due to macroreentry through recovered gaps. Nine of these 14 (64%) have remained arrhythmia-free without antiarrhythmics compared to 3 of 10 (30%) with incomplete block at 28 +/- 4 months following their last procedure (P = .2).Conclusions: This study demonstrates the feasibility of catheter ablation to transect the anterior LA in humans. While being effective in the termination of AF, this configuration of linear lesions is technically challenging to complete, results in significant delayed LA activation, and is associated with modest long-term arrhythmia suppression. [ABSTRACT FROM AUTHOR]

Coronary Sinus Disconnection. We report a case of radiofrequency catheter ablation for chronic atrial fibrillation, in which electrical disconnection of the coronary sinus was necessary to isolate a trigger initiating atrial fibrillation. (J Cardiovasc Electrophysiol, Vol. 15, pp. 364-368, March 2004) [ABSTRACT FROM AUTHOR]

The term "Mahaim fiber" usually is applied to an atriofascicular fiber that inserts distally into the right bundle branch and forms the anterograde limb of a reciprocating tachycardia. One of the features that has been used to describe the physiology of Mahaim fibers is the presence of anterograde preexcitation. We describe two patients who had a clinical tachycardia consistent with a "Mahaim tachycardia" in whom there was no evidence or minimal evidence of anterograde preexcitation during sinus rhythm or atrial pacing. In both patients, the tachycardia was rendered noninducible by radiofrequency ablation at the site of Mahaim potentials at the tricuspid annulus, and a long-term cure was achieved. This is the first description of a "latent Mahaim fiber" that does not cause preexcitation but which can support antidromic reciprocating tachycardia. [ABSTRACT FROM AUTHOR]

Introduction: Focal right atrial tachycardia (RAT) arising from the crista terminalis, para-Hisian, and coronary sinus os regions are well described. Less information exists regarding RAT arising from the nonseptal region of the tricuspid annulus (TA). Methods and Results: From a consecutive series of 64 patients who had undergone successful radiofrequency ablation (RFA) of 67 RATs, the characteristics of 9 (13%) patients (6 men; mean age 50 ± 20 years) with a TA focus were reviewed. The annular focus was localized to the inferoanterior TA in 7 and the superior TA in 2. Mean tachycardia cycle length was 371 ± 66 msec. Mean activation time at the site of successful RFA in 9 of 9 patients was -43 ± 11 msec. At 9.3 ± 5.6 months of follow-up, 1 of 9 patients had recurrent tachycardia successfully treated with repeat RFA. In 7 of 9 patients with RAT from the inferoanterior TA, the surface ECG P wave morphology was upright in a VL, inverted in III and V1, and either inverted or biphasic with an initial negative deflection from V2 to V6. Conclusion: The TA is an important site of origin of RAT. In the present study, the inferoanterior region of the TA was a preferential site of origin with resulting characteristic P wave morphology. Knowledge of this anatomic distribution and P wave morphology allows targeted mapping and may facilitate successful RFA. [ABSTRACT FROM AUTHOR]

The efficacy of intravenous magnesium in terminating sustained monomorphic ventricular tachycardia was examined in this study. This therapy was found to be ineffective in aborting monomorphic ventricular tachycardia induced in the electrophysiology laboratory. [ABSTRACT FROM AUTHOR]

Hypertrophic cardiomyopathy (HCM) is an inherited cardiac disorder affecting one in 500 of the general population. Atrial fibrillation (AF) is the most common arrhythmia in patients with HCM. We sought to characterize the atrial electrophysiological and structural substrate in young and aging Gly203Ser cardiac troponin-I transgenic (HCM) mice. At 30 weeks and 50 weeks of age (n = 6 per strain each group), the left atrium was excised and placed on a multi-electrode array (MEA) for electrophysiological study; subsequent histological analyses and plasma samples were analyzed for biomarkers of extracellular matrix remodeling and cell adhesion and inflammation. Wild-type mice of matched ages were included as controls. Young HCM mice demonstrated significantly shortened atrial action potential duration (APD), increased conduction heterogeneity index (CHI), increased myocyte size, and increased interstitial fibrosis without changes in effective refractory periods (ERP), conduction velocity (CV), inflammatory infiltrates, or circulating markers of extracellular matrix remodeling and inflammation. Aging HCM mice demonstrated aggravated changes in atria electrophysiology and structural remodeling as well as increased circulating matrix metalloproteinases (MMP)-2, MMP-3, and VCAM-1 levels. This model of HCM demonstrates an underlying atrial substrate that progresses with age and may in part be responsible for the greater propensity for AF in HCM. [ABSTRACT FROM AUTHOR]

Focuses on the rapid development of nonpharmacological strategies for treatment of atrial fibrillation. Role of pulmonary veins in the implementation of ablation at mitral isthmus; Advantages of the new strategy over traditional ablation techniques; Assertion on the need for further research on the potential of the new technique.

LA Appendage Disconnection. We report a case with paroxysmal atrial fibrillation, in whom multiple foci were identified in the left atrial appendage after pulmonary vein isolation. The patient was successfully treated by catheter ablation to disconnect this structure. (J Cardiovasc Electrophysiol, Vol. 16, pp. 1-3, August 2005) [ABSTRACT FROM AUTHOR]

Cycle length alternation in atrioventricular reentrant tachycardia due to alternating conduction time over the dual atrioventricular (AV) nodal pathways has been well described. Atriofascicular pathways with decremental conduction characteristics (Mahaim fibers) are known to contain accessory AV nodal tissue. We describe a case of cycle-length alternans in antidromic tachycardia through an atriofascicular pathway because of alternation in conduction time in the antegrade limb. The possible mechanisms of this phenomenon, rarely described in atriofascicular pathways, are discussed. [ABSTRACT FROM AUTHOR]

Discusses the importance of knowledge of the left atrial anatomy coupled with improved understanding of the mechanisms initiating and maintaining atrial fibrillation (AF) on the development of ablation techniques and strategies. Role of the pulmonary veins in the initiation of AF; Number of location of left atrial linear lesions; Implications on studies of cardiac electrophysiology.

The COVID-19 pandemic poses a significant stress on health resources in Australia. The Heart Rhythm Council of the Cardiac Society of Australia and New Zealand aims to provide a framework for efficient resource utilisation balanced with competing risks when appropriately treating patients with cardiac arrhythmias. This document provides practical recommendations for the electrophysiology (EP) and cardiac implantable electronic devices (CIED) services in Australia. The document will be updated regularly as new evidence and knowledge is gained with time. [ABSTRACT FROM AUTHOR]

Background Insertable cardiac monitors (ICMs) are increasingly utilized for diagnosis of unexplained syncope and arrhythmia monitoring. The Reveal LINQ is a novel miniaturized ICM with improved algorithms. The feasibility and safety of insertion outside the traditional electrophysiology laboratory is unknown. Here we compare outcomes of Reveal LINQ insertion in different environments. Methods We report on a prospective, single-centre, non-randomized, observational experience of consecutive Reveal LINQ implantation in the electrophysiology laboratory or a procedure room between October 2013 and October 2015. Results Of 178 consecutive patients who underwent LINQ device insertion, 80 were implanted in the electrophysiology laboratory and 98 in a procedure room. There were no significant differences in baseline patient characteristics. All implants were performed in the recommended manufacturer method with the exception of 1 which required suture closure. Only a minority received peri-procedural antibiotics with a greater number in the electrophysiology laboratory group (11 [14%] versus 1 [1%], p = 0.007). Overall, there were 3 (1.7%) complications with no significant difference between the electrophysiology laboratory and the procedure room groups (2 [3%] versus 1 [1%], p = 0.45). There was 1 superficial infection in the procedure room group and 1 superficial infection with device extrusion and 1 traumatic extrusion in the electrophysiology laboratory group. Procedure room implantation subjectively improved laboratory efficiency and patient flow. Conclusion Reveal LINQ insertion can be safely performed outside of the cardiac laboratory provided a sterile technique is followed by the operator using manufacturer recommendations for insertion. These findings have significant resource implications for hospitals undertaking such procedures. [ABSTRACT FROM AUTHOR]

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 < 0.001); LA volume (p < 0.001); LA pressure (p < 0.001), and PA pressures (p < 0.001); reduced atrial CV (LA p < 0.001) with increased conduction heterogeneity (p < 0.001); increased fractionated electrograms (p < 0.001); decreased posterior LA voltage (p < 0.001) and increased voltage heterogeneity (p < 0.001); no change in the effective refractory period (ERP) (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. [ABSTRACT FROM AUTHOR]

Although conferences are important vehicles for discussing scientific findings, the translation of presented research into peer-reviewed manuscripts is a crucial subsequent step in the research process. Given the evolving subspecialization of cardiology, we sought to characterize the temporal and comparative outcomes of abstracts presented at a subspecialty cardiac electrophysiology conference. Abstracts presented at the Heart Rhythm Society conference (1994 through 2006; HRS abstracts) and abstracts presented at the American Heart Association conference (2003; AHA abstracts) were studied. Subsequent publications, impact factors, and citation rates were determined. A total of 3,850 HRS and 1,000 AHA abstracts were studied. More human abstracts were presented at HRS than AHA (p <0.05). Compared with HRS abstracts, more AHA abstracts were published (p <0.001) and had higher impact factors and citation rates (p <0.001 for both). These differences were attributable in part to the greater proportion of human HRS abstracts. Compared with HRS abstracts, electrophysiology-related AHA abstracts were published less (p <0.001), and these publications had similar impact factors (p [ 0.38) although greater citation rates (p [ 0.001). The number and publication rate of HRS abstracts increased over the 15-year period, as did their publication impact factors and citation rates (p <0.001 for all). In conclusion, there are significant differences between AHA and HRS abstracts. Although AHA abstracts were more likely to be published overall, the publication rate and impact of electrophysiology abstracts presented at both a subspecialty (HRS) and a major cardiovascular conference (AHA) were comparable. There has also been a growth in the number and impact of cardiac electrophysiology abstracts presented at HRS in recent years. [ABSTRACT FROM AUTHOR]

Recent reports have described that hospitalizations for atrial fibrillation (AF) are continuing to increase. Given that hospitalizations are responsible for most of the economic burden associated with AF, the aim of this study was to characterize the impact of age and how changing procedural practices may be contributing to the increasing rates of AF hospitalizations. The annual age- and gender-specific incidence of hospitalizations for AF, electrical cardioversions, electrophysiologic studies, and radiofrequency ablation procedures in Australia were determined from 1993 to 2007 inclusive. Over this 15-year follow-up period spanning almost 300 million person-years, a total of 473,501 hospitalizations for AF were identified. There was a relative increase in AF hospitalizations of 203% over the study period, in contrast to an increase for all hospitalizations of only 71%. Whereas the gender-specific incidence of hospitalizations remained stable, the age-specific incidence increased significantly over the study period, particularly in older age groups. AF hospitalizations associated with electrical cardioversions decreased from 27% to 14% over the study period. Electrophysiologic studies and radiofrequency ablation procedures contributed minimally to the overall increase in AF hospitalizations observed. In conclusion, in addition to the growing prevalence of AF because of the aging population, there is an increasing age-specific incidence of hospitalizations for AF, particularly in older age groups. In contrast, changing procedural trends have contributed minimally to the increasing number of AF-associated hospitalizations. Greater attention to older patients with AF is required to develop strategies to prevent hospitalizations and contain the growing burden on health care systems. [ABSTRACT FROM AUTHOR]

Percutaneous transseptal left atrial (LA) access is increasingly becoming a routine procedure in the electrophysiology and cardiac catheterisation laboratories. Our aim was to review an unselected large series of this procedure performed over a period of five years. We clinically characterised difficult cases and presented a method of safe and expeditious LA access. Overall, 543 transseptal punctures were performed. Of those, 10 were classified as difficult, with failure to access the LA in three or more attempts. In all 10 cases, surgical electrocautery was successfully used to facilitate needle puncture of the septum. All patients subsequently underwent an uncomplicated procedure. In conclusion, we describe a method to trouble-shoot the difficult transseptal access procedure, outlining the clinical characteristics, echocardiographic features and special precautions that need to be considered when utilising this method. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this report was to study the effect of chronic stretch reversal on the electrophysiological characteristics of the atria in humans. Background: Atrial stretch is an important determinant for atrial fibrillation. Whether relief of stretch reverses the substrate predisposed to atrial fibrillation is unknown. Methods: Twenty-one patients with mitral stenosis undergoing mitral commissurotomy (MC) were studied before and after intervention. Catheters were placed at multiple sites in the right atrium (RA) and sequentially within the left atrium (LA) to determine: effective refractory period (ERP) at 10 sites (600 and 450 ms) and P-wave duration (PWD). Bi-atrial electroanatomic maps determined conduction velocity (CV) and voltage. In 14 patients, RA studies were repeated ≥6 months after MC. Results: Immediately after MC, there was significant increase in mitral valve area (2.1 ± 0.2 cm2, p < 0.0001) with decrease in LA (23 ± 7 mm Hg to 10 ± 4 mm Hg, p < 0.0001) and pulmonary arterial pressures (38 ± 16 mm Hg to 27 ± 12 mm Hg, p < 0.0001) and LA volume (75 ± 20 ml to 52 ± 18 ml, p < 0.0001). This was associated with reduction in PWD (139 ± 19 ms to 135 ± 20 ms, p = 0.047), increase in CV (LA: 1.3 ± 0.3 mm/ms to 1.7 ± 0.2 mm/ms, p = 0.006; and RA: 1.0 ± 0.1 mm/ms to 1.3 ± 0.3 mm/ms, p = 0.002) and voltage (LA: 1.7 ± 0.6 mV to 2.5 ± 1.0 mV, p = 0.005; and RA: 1.8 ± 0.6 mV to 2.2 ± 0.7 mV, p = 0.09), and no change in ERP. Late after MC, mitral valve area remained at 2.1 ± 0.3 cm2 (p = 0.7) but with further decrease in PWD (113 ± 19 ms, p = 0.04) and RA ERP (at 600 ms, p < 0.0001), with increase in CV (1.0 ± 0.1 mm/ms to 1.3 ± 0.2 mm/ms, p = 0.006) and voltage (1.8 ± 0.7 mV to 2.8 ± 0.6 mV, p = 0.002). Conclusions: The atrial electrophysiologic and electroanatomic abnormalities that result from chronic stretch due to MS reverses after MC. These observations suggest that the substrate predisposing to atrial arrhythmias might be reversed. [Copyright &y& Elsevier]

Objectives: The purpose of this study was to determine whether patients with paroxysmal “lone” atrial fibrillation (AF) have an abnormal atrial substrate. Background: While “AF begets AF,” prompt termination to prevent electrical remodeling does not prevent disease progression. Methods: Twenty-five patients with paroxysmal lone AF, without arrhythmia in the week prior, and 25 reference patients with left-sided accessory pathways were studied. Multipolar catheters placed at the lateral right atrium (RA), crista terminalis, coronary sinus, septal RA, and sequentially within the left atrium (LA) determined the effective refractory period (ERP) at 10 sites, conduction time along linear catheters, and conduction characteristics at the crista terminalis. Bi-atrial electroanatomic maps were created to determine regional differences in conduction velocity and voltage. Results: Patients with AF demonstrated the following compared with reference patients: larger atrial volumes (RA: 94 ± 18 ml vs. 69 ± 9 ml, p = 0.003; LA: 99 ± 19 ml vs. 77 ± 17 ml, p = 0.006); longer ERP (at 600 ms: 255 ± 25 ms vs. 222 ± 16 ms, p < 0.001; at 450 ms: 234 ± 20 ms vs. 212 ± 14 ms, p = 0.004); longer conduction time along linear catheters (57 ± 18 ms vs. 47 ± 10 ms, p = 0.01); longer bi-atrial activation time (128 ± 17 ms vs. 89 ± 10 ms, p < 0.001); slower conduction velocity (RA: 1.3 ± 0.3 mm/ms vs. 2.1 ± 0.5 mm/ms; LA: 1.2 ± 0.2 mm/ms vs. 2.2 ± 0.4 mm/ms, p < 0.001); greater proportion of fractionated electrograms (27 ± 8% vs. 8 ± 5%, p < 0.001); longer corrected sinus node recovery time (265 ± 57 ms vs. 185 ± 60 ms, p = 0.002); and lower voltage (RA: 1.7 ± 0.4 mV vs. 2.9 ± 0.4 mV; LA: 1.7 ± 0.7 mV vs. 3.3 ± 0.7 mV, p < 0.001). Conclusions: Patients with paroxysmal lone AF, remote from arrhythmia, demonstrate bi-atrial abnormalities characterized by structural change, conduction abnormalities, and sinus node dysfunction. These factors are likely contributors to the “second factor” that predisposes to the development and progression of AF. [Copyright &y& Elsevier]