Right Atrial Complexity Evolves With Stepwise Left-Sided Persistent Atrial Fibrillation Substrate Ablation and Predicts Outcomes.

OBJECTIVES: This study sought to study the relation between outcomes of modified stepwise atrial fibrillation (AF) substrate ablation and dynamic electrogram characteristics in the coronary sinus (CS) and right atrium (RA). BACKGROUND: Identifying patients with persistent AF who will benefit from limited lesion sets versus those requiring extensive substrate modification is challenging. METHODS: We studied 70 patients undergoing persistent AF ablation, 43 with acute success (successful ablation [sABL], AF termination, or noninducibility) and 27 with failure (failed ablation [fABL], no termination, or induced AF of >5 minutes). Dominant frequency (DF) and sample entropy (SampEn, increasing with signal complexity) were measured on 30-second recordings of wide-coverage simultaneous RA and CS electrograms during baseline AF and induced AF post-pulmonary vein isolation and after left-sided electrogram-guided ablation steps (on the CS with or without the left atrium [LA]). RESULTS: At baseline AF, patients with sABL exhibited lower RA SampEn (p = 0.023) and lower CS DF (p = 0.030) compared to fABL. A positive RA-to-CS SampEn gradient predicted ablation failure (48% vs. 19% for patients in fABL vs. sABL; p = 0.015). A positive RA-to-CS DF gradient developed in patients with fABL after extra-pulmonary vein substrate modification, unlike patients with sABL (p = 0.0008). At 24 months, 76% of patients were AF free, and 68% were arrhythmia free. sABL was associated with fewer AF recurrences (hazard ratio: 0.31; 95% confidence interval: 0.12-0.84; p = 0.021). A negative RA-to-CS SampEn gradient at baseline was associated with freedom from AF (-0.14 ± 0.19 vs. 0.04 ± 0.18; p = 0.002). CONCLUSIONS: RA greater than CS electrogram complexity gradients at baseline or developing during ablation are associated with unfavorable acute and long-term outcomes of persistent AF ablation. These parameters allow monitoring of the effects of left-sided substrate ablation and, therefore, a rational choice of additional RA substrate modification.

Sustained and self-terminating atrial fibrillation induced immediately after pulmonary vein isolation exhibit differences in coronary sinus electrical activity from onset.

INTRODUCTION: Little data exists on the electrophysiological differences between sustained atrial fibrillation (sAF; >5 minutes) vs self-terminating nonsustained AF (nsAF; <5 minutes). We sought to investigate the electrophysiological characteristics of coronary sinus (CS) activity during postpulmonary vein isolation (PVI) sAF vs nsAF. METHODS AND RESULTS: We studied 142 patients post-PVI for paroxysmal AF (PAF). In a 50-patient subset, CS electrograms in the first 30 seconds of induced AF were analyzed manually. A custom-made algorithm for automated electrogram annotation was derived for validation on the whole patient set. In patients with sAF post-PVI, CS fractionated potentials were ablated. Manual analysis showed that patients with sAF exhibited higher activation pattern variability (2.1 vs 0.5 changes/sec; P < .001); fewer proximal-to-distal wavefronts (25 vs 61%; P < .001); fewer unidirectional wavefronts (60 vs 86%; P < .001); more pivot locations (4.3 vs 2.1; P < .001); shorter cycle lengths (190 vs 220 ms; P < .001); and shorter cumulative isoelectric segments (35 vs 44%; P = .045) compared to nsAF. These observations were confirmed on the whole study population by automated electrogram annotation and sample entropy computation (SampEn: 0.29 ± 0.15 in sAF vs 0.15 ± 0.05 in nsAF; P < .0001). The derived model predicted sAF with 78% sensitivity, 88% specificity; agreement with manual model: 88% (Cohen's kappa= 0.76). CS defragmentation resulted in AF termination or noninducibility in 49% of sAF. CONCLUSION: In PAF patients post-PVI, induced sAF shows greater activation sequence variability, shorter cycle length, and higher SampEn in the CS compared to nsAF. Automated electrogram annotation confirmed these results and accurately distinguished self-terminating nsAF episodes from sAF based on 30-second recordings at AF onset.

Evolution of post-pulmonary vein isolation atrial fibrillation inducibility at redo ablation: Electrophysiological evidence of extra-pulmonary vein substrate progression.

BACKGROUND: The electrophysiological substrate underlying atrial fibrillation (AF) progression remains difficult to identify. OBJECTIVE: The goals of this study were to study the evolution of post-pulmonary vein isolation (PVI) AF inducibility (AFI) after AF ablation and to compare patients with organized atrial tachycardia recurrence (OATr) versus those with paroxysmal or persistent AF recurrence. METHODS: We studied 99 patients who underwent de novo AF ablation (p1) and redo ablation (p2) for AF recurrence (AFr) or OATr. Stepwise AF ablation was performed at p1 and p2: (1) PVI, (2) coronary sinus defragmentation, and (3) left atrial (LA) defragmentation. Burst pacing followed each step, with AFI defined as sustained AF >5 minutes, triggering the next step. Patients with OATr underwent OAT ablation and inducibility testing post-redo PVI. Inducibility progression (IP) was defined as AFI at further steps of p2 compared to p1. RESULTS: Among patients with AFr, 34 of 72 patients (47%) exhibited post-PVI IP vs 2 of 27 (7.4%) patients with OATr (P = .0002). Stratification for persistent AF/paroxysmal AF/OATr showed a consistent association between recurrence phenotype and IP. Pulmonary vein (PV) reconnection incidence was 90%, without association with recurrence type or IP. LA volume was larger in patients with IP than in those without IP (86.7 ± 25.3 mL vs 72.0 ± 28.9 mL; P = .001). Right atrial dimensions increased between p1 and p2 in patients with IP vs no IP and in patients with AFr vs OATr. CONCLUSION: Patients with AFr after first ablation exhibit IP more frequently at redo ablation than do patients with OATr. IP correlates with more advanced AFr type, larger LA volumes, and progressive right atrial enlargement. PV reconnection is not associated with AFr. Changes in post-PVI AFI may accurately indicate progression of extra-PV AF-maintaining substrate.

Electrophysiological and Anatomical Correlates of Sites With Postpacing Intervals Shorter Than Tachycardia Cycle Length in Atypical Atrial Flutter.

Background Although entrainment mapping is an established approach to atypical atrial flutter ablation, postpacing intervals shorter than tachycardia cycle length (difference between postpacing interval and tachycardia cycle length [dPPI] <0 ms) remain of unknown significance. We sought to compare anatomic and electrophysiological properties of sites with dPPI <0, dPPI=0-30, and dPPI >30 ms. Methods We studied 24 noncavotricuspid isthmus-dependent macroreentrant atypical atrial flutter in 19 consecutive patients. Ultra high-density electroanatomic activation maps were acquired with a 64-electrode basket catheter. Entrainment mapping was performed at multiple candidate sites. Ablation was performed at the narrowest accessible slow-conducting critical isthmuses. Results Of 102 entrainment mapping sites, dPPI <30 was observed at 72 sites on complete maps of 24 atypical atrial flutter. Compared with dPPI=0-30 sites (N=45), dPPI<0 sites (N=27) were more commonly located within isthmuses <15 mm wide (67% versus 6.7%, P<0.00001; odds ratio, 28.0; 95% CI, 6.8-115.7), more frequently located within 5 mm of the leading wavefront (93% versus 64%, P=0.008), exhibited slower local conduction velocity (0.49±0.43 versus 0.93±0.57 m/s, P=0.0005), lower voltages (0.48±0.79 versus 0.92±0.97 mV, P=0.04), and more frequently fractionated electrograms (67% versus 24%, P=0.0004). High rates of arrhythmia termination or cycle length increase >15 ms by ablation were observed in both dPPI groups (94% versus 86%, P=0.53). Compared with all dPPI <30, dPPI >30 sites (N=30) were less commonly observed within isthmuses (3.3%, P<0.001) or within 5 mm of the leading wavefront (30%, P<0.0001); conduction velocity (1.0±0.7 m/s, P=0.002) and voltage (1.1±1.4 mV, P=0.049) were higher compared with dPPI<0 but similar to dPPI=0-30 sites. Conclusions In atypical atrial flutter, sites with dPPI <0 are markers of limited width critical isthmuses with slower conduction velocity, whereas sites with dPPI=0-30 ms are often not in close proximity to the reentry circuit. Virtual electrode simultaneous down and upstream (antidromic) capture of a confined isthmus of slow conduction can explain a dPPI <0. Identifying these sites may improve selective and efficient ablation strategies compared with the standard 30-ms threshold.

Uptake of non-vitamin K antagonist oral anti coagulants in patients with atrial fibrillation - a prospective cohort study.

AIMS: We aimed to assess the uptake of non-vitamin K antagonist oral anticoagulants (NOACs) among patients with atrial fibrillation between 2010 and 2015 in Switzerland. METHODS: We performed a prospective observational cohort study. At the baseline examination and during yearly follow-ups, we used questionnaires to obtain information about clinical characteristics and antithrombotic treatment. Stroke risk was assessed using the CHA2DS2-VASc score. RESULTS: 1545 patients were enrolled across seven centres in Switzerland. Mean age was 68 ± 12 years and 29.5% were female. The percentage of anticoagulated patients with an indication for oral anticoagulation (CHA2DS2-VASc score ≥2 in women and ≥1 in men) was 75% in 2010 and 80% in 2015 (p = 0.2). There was a gradual increase in the use of NOACs from 0% in 2010 to 29.8% in 2015 (p <0.0001). Out of 888 patients, who initially received a vitamin K antagonist (VKA), 86 (9.7%) were switched to an NOAC during follow-up. Use of aspirin as a monotherapy decreased from 23% in 2010 to 11% in 2015 (p <0.0001). CONCLUSION: After regulatory approval, the use of NOACs in Switzerland steadily increased to about 30% in 2015, whereas switches from VKAs to NOACs were infrequent. In parallel, the prescription of aspirin as monotherapy was more than halved, suggesting significant guideline-concordant improvements in oral anticoagulation use among patients with atrial fibrillation.

Contact Force in Atrial Fibrillation: Role of Atrial Rhythm and Ventricular Contractions: Co-Force Atrial Fibrillation Study.

BACKGROUND: In an experimental model, variable and intermittent contact force (CF) resulted in a significant decrease in lesion volume. In humans, variability of CF during pulmonary vein isolation has not been characterized. METHODS AND RESULTS: In 20 consecutive patients undergoing CF-guided circumferential pulmonary vein isolation, 914 radiofrequency applications (530 in sinus rhythm and 384 in atrial fibrillation) were analyzed. The variability of the 60% CF range (CF(60%)) was 17±9.6 g. Hundred seventy-one (19%) applications were delivered with constant, 717 (78%) with variable, and 26 (3%) with intermittent CF. The mean CF and force-time integral were significantly higher during applications with variable than with intermittent or constant CF. There was no significant difference in CF variability, CF(60%) variability, and force-time integral between applications delivered in sinus rhythm and atrial fibrillation. The main reasons for CF variability were systolo-diastolic heart movement (29%) and respiration (27%). In 10 additional patients, during adenosine-induced atrioventricular block, the minimum CF significantly increased at 19 sites (5.3±4.4 versus 13.4±5.9 g; P<0.001) and at 16 sites intermittent or variable CF became constant. At only 1 site systolo-diastolic movement remained the main reason for variable CF. CONCLUSIONS: CF during pulmonary vein isolation remains highly variable despite efforts to optimize contact. CF and CF parameters were similar during sinus rhythm and atrial fibrillation. The main reasons for CF variability are systolo-diastolic heart movement and respiration. The systolo-diastolic peaks and nadirs of CF are because of ventricular contractions at the large majority of pulmonary vein isolation sites.

Relationship between catheter contact force and radiofrequency lesion size and incidence of steam pop in the beating canine heart: electrogram amplitude, impedance, and electrode temperature are poor predictors of electrode-tissue contact force and lesion size.

BACKGROUND: Electrode-tissue contact force (CF) is believed to be a major factor in radiofrequency lesion size. The purpose of this study was to determine, in the beating canine heart, the relationship between CF and radiofrequency lesion size and the accuracy of predicting CF and lesion size by measuring electrogram amplitude, impedance, and electrode temperature. METHODS AND RESULTS: Eight dogs were studied closed chest. Using a 7F catheter with a 3.5 mm irrigated electrode and CF sensor (TactiCath, St. Jude Medical), radiofrequency applications were delivered to 3 separate sites in the right ventricle (30 W, 60 seconds, 17 mL/min irrigation) and 3 sites in the left ventricle (40 W, 60 seconds, 30 mL/min irrigation) at (1) low CF (median 8 g); (2) moderate CF (median 21 g); and (3) high CF (median 60 g). Dogs were euthanized and lesion size was measured. At constant radiofrequency and time, lesion size increased significantly with increasing CF (P<0.01). The incidence of a steam pop increased with both increasing CF and higher power. Peak electrode temperature correlated poorly with lesion size. The decrease in impedance during the radiofrequency application correlated well with lesion size for lesions in the left ventricle but less well for lesions in the right ventricle. There was a poor relationship between CF and the amplitude of the bipolar or unipolar ventricular electrogram, unipolar injury current, and impedance. CONCLUSIONS: Radiofrequencylesion size and the incidence of steam pop increase strikingly with increasing CF. Electrogram parameters and initial impedance are poor predictors of CF for radiofrequency ablation.

Identifying far-field superior vena cava potentials within the right superior pulmonary vein.

BACKGROUND: Far-field extra-pulmonary vein (PV) potentials originating from the left atrial appendage and adjacent left atrium have been identified within the left PVs, but no systematic study of extra-PV potentials within the right superior PV (RSPV) has been described. OBJECTIVES: The purpose of this study was to prospectively analyze extra-PV contributions to RSPV potentials. METHODS: In a consecutive, prospective series of 114 patients (96 men and 18 women; 56 +/- 10 years) undergoing electrophysiologically guided ostial PV isolation, residual potentials recorded with a circular mapping catheter in the RSPV after ostial isolation were analyzed. Their extra-PV origin was validated by mapping a site with identical timing (in sinus rhythm or atrial fibrillation) within the adjacent superior vena cava (SVC) where, in sinus rhythm, local pacing (until threshold amplitude) concealed the residual potential within the stimulus artifact because of very short activation timing. The timing of residual potentials with respect to surface ECG P-wave onset was measured and compared with the earliest timing of ablated RSPV potentials. RESULTS: Residual low-amplitude (mean 0.29 +/- 0.17 mV, range 0.07-0.65 mV) extra-PV potentials were recorded from the anterior and superior aspect of the RSPV in 3.6 +/- 1 bipoles in 26 (23%) patients (all men, 51 +/- 10 years) with a timing from sinus P-wave onset of 17 +/- 12 ms (range 0-40 ms) vs 52 +/- 9 ms (range 35-70 ms) for the earliest RSPV potential (P <.001, t-test). Extra-PV potentials all originated from the posterior aspect of the SVC. The SVC potential was identified during ongoing atrial fibrillation in eight patients and later confirmed in sinus rhythm. An extra-PV potential of SVC origin could be identified by timing earlier than 30 ms from onset of the sinus P wave, with sensitivity of 92%, specificity 100%, positive predictive value 100%, and negative predictive value 89%. CONCLUSION: Extra-PV potentials of right-sided SVC origin were recorded within the RSPV in 23% of patients and can be identified with high sensitivity and specificity by a timing within 30 ms of sinus P-wave onset. Recognizing these potentials can avoid unnecessary additional ablation and possibly PV stenosis or phrenic paralysis.

Electrophysiologic and clinical consequences of linear catheter ablation to transect the anterior left atrium in patients with atrial fibrillation.

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.

Reverse remodeling of sinus node function after catheter ablation of atrial fibrillation in patients with prolonged sinus pauses.

BACKGROUND: Symptomatic prolonged sinus pauses on termination of atrial fibrillation (AF) are an indication for pacemaker implantation. We evaluated sinus node function and clinical outcome in patients with prolonged sinus pauses on termination of arrhythmia who underwent ablation of paroxysmal AF. METHODS AND RESULTS: Twenty patients with paroxysmal AF and prolonged sinus pauses (> or =3 seconds) on termination of AF underwent ablation between May 1995 and November 2002. Patients with sinus pauses independent of episodes of AF were excluded from the analysis. The procedure included pulmonary vein and linear atrial ablation. After ablation, sinus node function was assessed during the first week and at 1, 3, and 6 months, by 24-hour ambulatory monitoring to determine the mean heart rate and heart rate range, and by exercise testing to determine the maximal heart rate. Corrected sinus node recovery time was determined at the completion of ablation and at 24.0+/-11.3 months at 600 and 400 ms. After AF ablation, there was a significant improvement of sinus node function, with an increase in the mean heart rate (P=0.001), maximal heart rate (P<0.0001), and heart rate range (P<0.0001). The corrected sinus node recovery time decreased in all patients evaluated at 600 ms (P=0.016) and 400 ms (P=0.019). At 26.0+/-17.6 months, 18 patients (85%) had no recurrence of AF (in the absence of medication), with no symptoms attributable to bradycardia or sinus pauses on ambulatory monitoring. Two patients had infrequent episodes of AF, 1 requiring pacemaker implantation. CONCLUSIONS: Prolonged sinus pauses after paroxysms of AF may result from depression of sinus node function that can be eliminated by curative ablation of AF. This is accompanied by improvement in parameters of sinus node function, suggesting reverse remodeling of the sinus node.

Mapping and ablation of ventricular fibrillation associated with long-QT and Brugada syndromes.

BACKGROUND: The long-QT and Brugada syndromes are important substrates of malignant ventricular arrhythmia. The feasibility of mapping and ablation of ventricular arrhythmias in these conditions has not been reported. METHODS AND RESULTS: Seven patients (4 men; age, 38+/-7 years; 4 with long-QT and 3 with Brugada syndrome) with episodes of ventricular fibrillation or polymorphic ventricular tachycardia and frequent isolated or repetitive premature beats were studied. These premature beats were observed to trigger ventricular arrhythmias and were localized by mapping the earliest endocardial activity. In 4 patients, premature beats originated from the peripheral right (1 Brugada) or left (3 long-QT) Purkinje conducting system and were associated with variable Purkinje-to-muscle conduction times (30 to 110 ms). In the remaining 3 patients, premature beats originated from the right ventricular outflow tract, being 25 to 40 ms ahead of the QRS. The accuracy of mapping was confirmed by acute elimination of premature beats after 12+/-6 minutes of radiofrequency applications. During a follow-up of 17+/-17 months using ambulatory monitoring and defibrillator memory interrogation, no patients had recurrence of symptomatic ventricular arrhythmia but 1 had persistent premature beats. CONCLUSIONS: Triggers from the Purkinje arborization or the right ventricular outflow tract have a crucial role in initiating ventricular fibrillation associated with the long-QT and Brugada syndromes. These can be eliminated by focal radiofrequency ablation.

Nonpulmonary vein foci: do they exist?

Though the majority of foci triggering atrial fibrillation (AF) have been mapped to the pulmonary veins (PV), recurrence of paroxysmal AF after isolation of all four pulmonary veins indicates the presence of other foci. In a series of 160 consecutive patients who underwent PV ablation, endocardial mapping of AF and ectopy recurring after PV isolation was performed. Thirty-six patients (24%) had a total of 85 non-PV foci; 39 were mapped to the ostia of ablated PVs, 30 to the posterior left atrium (LA), 5 to other parts of the LA, 5 to the right atrium (RA), 4 to the coronary sinus (CS), and 3 to the superior vena cava (SVC) (including one persistent left SVC). Mapping was confirmed by successful ablation. At least 16 foci could not be localized and after a follow-up of 8 +/- 6 months, 68% of patients were free of AF without any antiarrhythmic treatment. The occurrence of non-PV foci correlated with recurrence of AF, perhaps as a correlate of insufficient ostial ablation. These data reinforce the requirement for more proximal disconnection of the PVs by performing ablation within the LA. In patients with non-PV foci that are difficult to map conventionally, the use of surface ECG data, or multielectrode contact or noncontact mapping arrays, or substrate modifying/excluding ablation may be helpful in ablating these foci and therefore eliminating AF.

Electrophysiologically guided pulmonary vein isolation during sustained atrial fibrillation.

INTRODUCTION: Sustained atrial fibrillation (AF) is frequently encountered during pulmonary vein (PV) isolation. The aim of this study was to evaluate the feasibility and safety of PV isolation during sustained AF. METHODS AND RESULTS: Thirty-seven patients (30 men, age 54 +/- 10 years) underwent Lasso-guided isolation of 87 PVs during sustained AF. Baseline PV electrogram patterns were classified into one of two types: organized, with consistent PV activation sequence; or disorganized, with constant variation of PV activation sequence. In disorganized activity, radiofrequency ablation was performed circumferentially around the Lasso while the earliest PV potential was targeted during organized activity. Complete left atrial (LA) to PV block during AF was identified by abolition or dissociation of all sharp potentials recorded within the vein. PV isolation then was verified during sinus rhythm. Baseline activation patterns of PV potential were organized in 32 PVs (37%) [more frequently in inferior veins than superior veins (53% vs 26%, P = 0.01)] and disorganized in 55 PVs (63%). In 59 of 87 PVs, isolation was begun and completed during AF. Radiofrequency ablation organized PV activation sequence in 75% prior to isolation. LA-PV block was confirmed during sinus rhythm in 54 (92%) of 59 PVs. In 28 of 87 PVs, sinus rhythm was restored before complete LA-PV block. Complete isolation was achieved in all 87 PVs without complications. CONCLUSION: PV isolation can be effectively and safely performed during sustained AF, preceded in most cases by organization of PV electrogram activity. This strategy may be the preferred alternative to multiple intraprocedural cardioversions.

Distinctive electrophysiological properties of pulmonary veins in patients with atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is frequently initiated from pulmonary veins (PVs), but little is known of the electrophysiological properties of PVs. METHODS AND RESULTS: Two groups were studied: 28 patients (49+/-13 years old) with paroxysmal AF and 20 control patients (49+/-14 years old) without AF. Effective and functional refractory period and conduction time from PV to left atrium (LA) were compared in the 2 groups by use of programmed stimulation with a single extrastimulus in the PVs and LA. In the AF group, the venous effective refractory periods (ERPs) were shorter than that of the LA: 185+/-71 versus 253+/-21 ms, P<0.001, whereas in the control group, they were longer (282+/-45 versus 253+/-41 ms, P=0.009). The venous ERPs and functional refractory periods in patients with AF were also shorter than that observed in control subjects (185+/-71 versus 282+/-45 ms and 210+/-77 versus 315+/-43 ms, respectively, P<0.001), whereas LA ERPs were not significantly different. Decremental conduction in PVs was more frequent (93% versus 56%, P=0.01) and had a greater increment (102+/-65 versus 42+/-40 ms, P<0.001) in patients with AF. Finally, AF was more frequently induced when pacing was performed in PVs (22 of 90) versus LA (1 of 81) in patients with AF (P<0.001). CONCLUSIONS: The PVs of patients with AF exhibited distinctive electrophysiological properties, which were strikingly different from those of patients devoid of AF, potentially explaining their arrhythmogenicity.

Electrophysiological evaluation and ablation of atypical right atrial flutter.

Right atrial reentry which does not critically depend upon activation through the cavotricuspid isthmus is considered to be a subtype of atypical flutter. Diagnosis is dependent upon demonstrating the nonparticipation of the cavotricuspid isthmus. Right atrial free wall atriotomy incisions, the superior vena cava, the inferior vena cava, electrically silent or mute areas, incomplete variants of the posterior intercaval crista terminalis line of block and other functional/anisotropic lines of block form the central barriers around which macroreentry occurs. The length, location and orientation of fixed lines of block such as atriotomy incisions are important determinants of their arrhythmogenicity. Successful catheter ablation depends upon delineating the circuit in order to choose the optimal isthmus for ablation and producing complete block across it.