Identification of repetitive atrial activation patterns in persistent atrial fibrillation by direct contact high-density electrogram mapping.

INTRODUCTION: Recent studies have characterized drivers in persistent atrial fibrillation using automated algorithm detection with panoramic endocardial mapping by means of basket catheters. We aimed to identify repetitive atrial activation patterns (RAAPs) during ongoing atrial fibrillation (AF) based upon automated annotation of unipolar electrograms (EGMs) recorded with a high-density regional endocardial contact mapping catheter. METHODS: In 14 persistent AF patients, high-resolution EGMs were recorded for 30 seconds at sequential PentaRay (Biosense Inc) positions covering the entire biatrial surface. All recordings were reviewed off-line with dedicated software allowing automated annotation of the local activation time of the unipolar fibrillatory EGMs (CARTOFINDER; Biosense Inc). RAAPs were defined as a consistent activation pattern (for ≥3 consecutive beats) of either focal activity with centrifugal spread (RAAPfocal ) or rotational activity across the PentaRay splines spanning the AF cycle length (RAAProtational ). RESULTS: A total of 498 PentaRay recordings were analyzed (35.6 ± 7.6 per patient). The number of PentaRay recordings displaying RAAP was 9.8 ± 3.1 per patient (range = 3-15), of which 2.4 ± 2.4 RAAProtational (range = 0-7), and 7.4 ± 4.4 RAAPfocal (range = 1-13). 77% of RAAPs portrayed focal firing. The median number of repetitions per 30 second recording was 11 (range = 3-225) per recording. RAAPs were observed both in the right atrium (RA) (35%) and left atrium (LA) (65%), with the majority being near the left PVs/appendage (35% of all RAAPs) and the superior vena cava/right appendage (23% of all RAAPs). CONCLUSION: High-resolution, sequential endocardial EGM-based mapping allows identification of RAAPs in persistent AF. In our series, focal firing was the most frequently observed pattern.

Evaluation of a simple technique aiming at optimizing point-by-point isolation of the left pulmonary veins: a randomized study.

AIMS: We sought to evaluate the efficacy and the safety of a simple technique for stabilizing the ablation catheter during anterior pulmonary vein (PV) encirclement in patients ablated for paroxysmal atrial fibrillation. This consisted of bending the ablation catheter in the left atrium, creating a loop that was cautiously advanced together with the long sheath at the ostium and then within the left superior PV. The curve was then progressively released to reach a stable contact with the anterior part of the left PVs. METHODS AND RESULTS: Eighty consecutive patients (age 64 ± 11 years, left atrial diameter 43 ± 8 mm) undergoing 'CLOSE'-guided PV isolation were prospectively randomized into two groups depending on whether the loop technique was used or not. When using the loop technique, the encirclement of the left PVs was shorter [20 min (interquartile range, IQR 17-24) vs. 26 min (IQR 18-33), P < 0.01] with a high rate of first pass isolation [(100%) vs. (97%), P = 0.9] and adenosine proof isolation [(93%) vs. (95%), P = 0.67]. Most specifically, at the anterior part of the left PVs, there were less dislocations [0 (IQR 0-0) vs. 1 (IQR 0-4), P < 0.001], radiofrequency duration was shorter (272 ± 85 s vs. 378 ± 122 s, P < 0.001), force-time integral was higher [524 gs (IQR 427-687) vs. 398 gs (IQR 354-451), P < 0.001], average contact force was higher [20 g (IQR 13-27) vs. 11g (IQR 9-16), P < 0.001], and impedance drop was higher [12 Ω (IQR 9-19) vs. 10 Ω (IQR 7-14), P < 0.001]. CONCLUSION: This study describes a simple technique to facilitate catheter stability at the anterior part of the left PVs, resulting in more efficient left PV encirclement without compromising safety.

Pulmonary Vein Reconnection No Longer Occurs in the Majority of Patients After a Single Pulmonary Vein Isolation Procedure.

OBJECTIVES: This study sought to determine the prevalence of patients with 4 isolated veins at repeat ablation after "CLOSE" -guided pulmonary vein isolation (PVI), a strategy based on delivery of contiguous and optimized radiofrequency lesions. BACKGROUND: The likelihood of finding 4 isolated veins at a repeat ablation for atrial fibrillation (AF) recurrence after a first PVI is low. METHODS: Patients undergoing repeat ablation for AF recurrence after first CLOSE-guided PVI were included. At repeat: 1) the status of the PV was evaluated; and 2) high-density voltage mapping was performed. In case of pulmonary vein reconnection (PVR), veins were reisolated. In patients with 4 isolated veins, empirical trigger or substrate ablation was performed. RESULTS: Of 326 patients undergoing CLOSE-guided PVI for paroxysmal AF, 45 patients underwent repeat ablation for AF recurrence (11 ± 7 months after first PVI). In 28 patients, all veins were still isolated (62%). They showed similar clinical characteristics and similar time from first PVI to AF recurrence (8 ± 7 vs. 6 ± 6 months, respectively, p = 0.453) compared with patients with PVR. In contrast, they were characterized by a higher incidence of low voltage (57% vs. 17%, p = 0.033). Patients with 4 isolated veins, compared with patients treated for PVR, showed a lower 12-month freedom from AF after repeat ablation (61% vs. 88%, p = 0.045). CONCLUSIONS: After CLOSE-guided ablation, PVR is no longer the rule in patients with AF recurrence. Patients with AF recurrence and 4 isolated veins present with a similar clinical profile and time to recurrence as patients with PVR.

Failure to detect life-threatening arrhythmias in ICDs using single-chamber detection criteria.

BACKGROUND: There are anecdotal reports of sudden death despite a functional implantable cardioverter defibrillator (ICD). We sought to describe scenarios leading to fatal or near-fatal outcome due to inappropriately inhibited ICD therapy in devices programmed with single-chamber detection criteria. METHODS: Programmed settings, episode lists, and intracardiac electrograms from 24 patients with a life-threatening event (n = 12) or fatal outcome (n = 12) related to failed ventricular arrhythmia detection were used to clarify the underlying scenario. RESULTS: Fifty episodes of failed ventricular arrhythmia detection were identified and categorized into six scenarios: (1) spontaneous ventricular tachycardia (VT) or ventricular fibrillation (VF) with a rate below the detection limits, (2) misclassification of polymorphic VT (PVT) or VF as supraventricular tachycardia (SVT), (3) misclassification of VT/VF as cluster of nonsustained VT episodes, (4) misclassification of monomorphic VT (MVT) as SVT, (5) inappropriate shock abortion, and (6) false termination detection. These scenarios occurred respectively 6, 9, 3, 9, 8, and 15 times. In 9/9 (100%) patients with PVT/VF classified as SVT, rate stability was active for rates ranging from 222 to 250 beats/min. MVT detected as SVT was due to the sudden onset criterion in 7/9 (78%) patients and twice a consequence of the rate stability criterion active for rates ranging from 200 to 250 beats/min. CONCLUSION: We describe six scenarios leading to failure of ventricular arrhythmia detection in a single-chamber detection setting withholding life-saving therapy. These scenarios are more likely to occur with high-rate programming and long detection times, especially if combined with rate stability and sudden onset.

Clinical assessment and comparison of annotation algorithms in high-density mapping of regular atrial tachycardias.

BACKGROUND: High-density automated mapping of regular atrial tachycardias (ATs) requires accurate assessment of local activation times (LATs). OBJECTIVE: To evaluate high-density mapping of ATs and compare the accuracy of different automated LAT annotation algorithms. METHODS: Fifteen patients underwent AT ablation guided by the automated ConfiDENSEۛ high-density mapping module (Carto 3 v4) allowing manual reannotation (edited maps). For each AT, unedited automated maps were reconstructed offline by three algorithms: maximum unipolar slope (LATSlope ), bipolar peak (LATPeak ), and a new hybrid annotation algorithm (LATHybrid ). Five blinded experts were asked to define the (1) tachycardia mechanism, (2) ablation target, and (3) level of difficulty of these unedited maps. RESULTS: Twenty-one ATs (cycle length 300 ± 46 ms, activation points 955 ± 421) were successfully ablated using LATHybrid guided ablation with manual editing in a small number of points. At 6 months, 14 (93%) of the patients were free of AT recurrences. Unedited LATHybrid maps showed the highest accuracy in defining the tachycardia mechanism (LATHybrid : 49% vs. LATPeak : 27% vs. LATSlope : 28%, P < 0.001) and ablation target (LATHybrid : 65% vs. LATPeak : 39% vs. LATSlope : 31%, P < 0.001). Overall, LATHybrid -annotated maps were graded as "easier to interpret" by the experts (difficulty score 2.3 ± 0.9) versus LATPeak (2.8 ± 1) and LATSlope (3.2 ± 0.8) (P < 0.001). Only 12% of the LATHybrid maps were annotated as uninterpretable compared to 31% of LATSlope and 45% of the LATPeak maps (P < 0.001). CONCLUSION: Automated LATHybrid annotation allows better and easier recognition of the tachycardia mechanism compared to automated LATPeak and LATSlope algorithms, although fully automated mapping still requires further improvements.

Five-year outcome of catheter ablation of persistent atrial fibrillation using termination of atrial fibrillation as a procedural endpoint.

BACKGROUND: This study aimed to determine 5-year efficacy of catheter ablation for persistent atrial fibrillation (AF) using AF termination as a procedural end point. METHODS AND RESULTS: One hundred fifty patients (57±10 years) underwent persistent AF ablation using a stepwise ablation approach (pulmonary vein isolation, electrogram-guided, and linear ablation) with the desired procedural end point being AF termination. Repeat ablation was performed for recurrent AF or atrial tachycardia. AF was terminated by ablation in 120 patients (80%). Arrhythmia-free survival rates after a single procedure were 35.3%±3.9%, 28.0%±3.7%, and 16.8%±3.2% at 1, 2, and 5 years, respectively. Arrhythmia-free survival rates after the last procedure (mean 2.1±1.0 procedures) were 89.7%±2.5%, 79.8%±3.4%, and 62.9%±4.5%, at 1, 2, and 5 years, respectively. During a median follow-up of 58 (interquartile range, 43-73) months after the last ablation procedure, 97 of 150 (64.7%) patients remained in sinus rhythm without antiarrhythmic drugs. Another 14 (9.3%) patients maintained sinus rhythm after reinitiation of antiarrhythmic drugs, and an additional 15 (10.0%) patients regressed to paroxysmal recurrences only. Failure to terminate AF during the index procedure (hazard ratio 3.831; 95% confidence interval, 2.070-7.143; P<0.001), left atrial diameter≥50 mm (hazard ratio 2.083; 95% confidence interval, 1.078-4.016; P=0.03), continuous AF duration≥18 months (hazard ratio 1.984; 95% confidence interval, 1.024-3.846; P<0.04), and structural heart disease (hazard ratio 1.874; 95% confidence interval, 1.037-3.388; P=0.04) predicted arrhythmia recurrence. CONCLUSIONS: In patients with persistent AF, an ablation strategy aiming at AF termination is associated with freedom from arrhythmia recurrence in the majority of patients over a 5-year follow-up period. Procedural AF nontermination and specific baseline factors predict long-term outcome after ablation.

Inverse relationship between fractionated electrograms and atrial fibrosis in persistent atrial fibrillation: combined magnetic resonance imaging and high-density mapping.

OBJECTIVES: This study sought to evaluate the relationship between fibrosis imaged by delayed-enhancement (DE) magnetic resonance imaging (MRI) and atrial electrograms (Egms) in persistent atrial fibrillation (AF). BACKGROUND: Atrial fractionated Egms are strongly related to slow anisotropic conduction. Their relationship to atrial fibrosis has not yet been investigated. METHODS: Atrial high-resolution MRI of 18 patients with persistent AF (11 long-lasting persistent AF) was registered with mapping geometry (NavX electro-anatomical system (version 8.0, St. Jude Medical, St. Paul, Minnesota)). DE areas were categorized as dense or patchy, depending on their DE content. Left atrial Egms during AF were acquired using a high-density, 20-pole catheter (514 ± 77 sites/map). Fractionation, organization/regularity, local mean cycle length (CL), and voltage were analyzed with regard to DE. RESULTS: Patients with long-lasting persistent versus persistent AF had larger left atrial (LA) surface area (134 ± 38 cm(2) vs. 98 ± 9 cm(2), p = 0.02), a higher amount of atrial DE (70 ± 16 cm(2) vs. 49 ± 10 cm(2), p = 0.01), more complex fractionated atrial Egm (CFAE) extent (54 ± 16 cm(2) vs. 28 ± 15 cm(2), p = 0.02), and a shorter baseline AF CL (147 ± 10 ms vs. 182 ± 14 ms, p = 0.01). Continuous CFAE (CFEmean [NavX algorithm that quantifies Egm fractionation] <80 ms) occupied 38 ± 19% of total LA surface area. Dense DE was detected at the left posterior left atrium. In contrast, the right posterior left atrium contained predominantly patchy DE. Most CFAE (48 ± 14%) occurred at non-DE LA sites, followed by 41 ± 12% CFAE at patchy DE and 11 ± 6% at dense DE regions (p = 0.005 and p = 0.008, respectively); 19 ± 6% CFAE sites occurred at border zones of dense DE. Egms were less fractionated, with longer CL and lower voltage at dense DE versus non-DE regions: CFEmean: 97 ms versus 76 ms, p < 0.0001; local CL: 153 ms versus 143 ms, p < 0.0001; mean voltage: 0.63 mV versus 0.86 mV, p < 0.0001. CONCLUSIONS: Atrial fibrosis as defined by DE MRI is associated with slower and more organized electrical activity but with lower voltage than healthy atrial areas. Ninety percent of continuous CFAE sites occur at non-DE and patchy DE LA sites. These findings are important when choosing the ablation strategy in persistent AF.

Prevalence and types of pitfall in the assessment of mitral isthmus linear conduction block.

BACKGROUND: To identify and understand clinically encountered pitfalls in the assessment of transmitral conduction block using differential coronary sinus and left atrial appendage pacing techniques in patients with left mitral isthmus linear ablation. METHODS AND RESULTS: All the available assessments of mitral isthmus block were thoroughly reviewed in 271 mitral isthmus ablation procedures undertaken among 236 patients from October 2008 to April 2011. Bidirectional block was established in 186 of 271 (69%) procedures. Careful evaluation of electrograms recorded on the multipolar coronary sinus and ablation catheters was undertaken to identify and understand the characteristics of pitfall, if any. Pitfall was encountered in 55 of 271 (20%) procedures among 51 patients and categorized into 6 types (types 1, 3, 4, and 5 led to spurious diagnosis of block; types 2 and 6 led to erroneous diagnosis of absence of block). There were 14, 10, 17, 2, 15, and 3 (total=61) cases of pitfall types 1 through 6, respectively. Operator recognized 42 of 61 (69%) pitfalls intraprocedurally. Recognition of types 1 and 5 was difficult because of indiscernible electrograms at usual amplifier settings or presence of slow conduction mimicking block. CONCLUSIONS: Every fifth assessment of bidirectional block across mitral isthmus linear lesion using differential coronary sinus and left atrial appendage pacing techniques encounters a pitfall, which can lead to erroneous clinical diagnosis of block or absence of block. Recognition of pitfall during the procedure is feasible and necessitates careful distinction of far-field left atrium from the local coronary sinus electrograms besides appropriate adjustments in catheter position and pacing outputs.

Disparate activation of the coronary sinus and inferior left atrium during atrial tachycardia after persistent atrial fibrillation ablation: prevalence, pitfalls, and impact on mapping.

INTRODUCTION: Persistent atrial fibrillation (AF) ablation may lead to partial disconnection of the coronary sinus (CS). As a result, disparate activation sequences of the local CS versus contiguous left atrium (LA) may be observed during atrial tachycardia (AT). We aimed to evaluate the prevalence of this phenomenon and its impact on activation mapping. METHODS: AT occurring after persistent AF ablation were investigated in 74 consecutive patients. Partial CS disconnection during AT was suspected when double potentials with disparate activation sequences were observed on the CS catheter. Endocardial mapping facing CS bipoles was performed to differentiate LA far-field from local CS potentials. RESULTS: A total of 149 ATs were observed. Disparate LA-CS activations were apparent in 20 ATs after magnifying the recording scale (13%). The most common pattern (90%) was distal to proximal endocardial LA activation against proximal to distal CS activation, the latter involving the whole CS or its distal part. Perimitral macroreentry was more common when disparate LA-CS activations were observed (67% vs 29%; P = 0.002). Partial CS disconnection also resulted in "pseudo" mitral isthmus (MI) block during LA appendage pacing in 20% of patients as local CS activation was proximal to distal despite distal to proximal activation of the contiguous LA. CONCLUSION: Careful analysis of CS recordings during AT following persistent AF ablation often reveals disparate patterns of activation. Recognizing when endocardial LA activation occurs in the opposite direction to the more obvious local CS signals is critical to avoid misleading interpretations during mapping of AT and evaluation of MI block.

Functional nature of electrogram fractionation demonstrated by left atrial high-density mapping.

BACKGROUND: Complex fractionated atrial electrograms (CFAE) are targets of atrial fibrillation (AF) ablation. Serial high-density maps were evaluated to understand the impact of activation direction and rate on electrogram (EGM) fractionation. METHODS AND RESULTS: Eighteen patients (9 persistent) underwent high-density, 3-dimensional, left-atrial mapping (>400 points/map) during AF, sinus (SR), and CS-paced (CSp) rhythms. In SR and CSp, fractionation was defined as an EGM with ≥4 deflections, although, in AF, CFE-mean <80 ms was considered as continuous CFAE. The anatomic distribution of CFAE sites was assessed, quantified, and correlated between rhythms. Mechanisms underlying fractionation were investigated by analysis of voltage, activation, and propagation maps. A minority of continuous CFAE sites displayed EGM fractionation in SR (15+/-4%) and CSp (12+/-8%). EGM fractionation did not match between SR and CSp at 70+/-10% sites. Activation maps in SR and CSp showed that wave collision (71%) and regional slow conduction (24%) caused EGM fractionation. EGM voltage during AF (0.59+/-0.58 mV) was lower than during SR and CSp (>1.0 mV) at all sites. During AF, the EGM voltage was higher at continuous CFAE sites than at non-CFAE sites (0.53 mV (Q1, Q3: 0.33 to 0.83) versus 0.30 mV (Q1, Q3: 0.18 to 0.515), P<0.00001). Global LA voltage in AF was lower in patients with persistent AF versus patients with paroxysmal AF (0.6+/-0.59 mV versus 1.12+/-1.32 mV, P<0.01). CONCLUSIONS: The distribution of fractionated EGMs is highly variable, depending on direction and rate of activation (SR versus CSp versus AF). Fractionation in SR and CSp rhythms mostly resulted from wave collision. All sites with continuous fractionation in AF displayed normal voltage in SR, suggesting absence of structural scar. Thus, many fractionated EGMs are functional in nature, and their sites dynamic.

Mitral isthmus ablation with and without temporary spot occlusion of the coronary sinus: a randomized clinical comparison of acute outcomes.

OBJECTIVE: To evaluate the safety and outcomes of mitral isthmus (MI) linear ablation with temporary spot occlusion of the coronary sinus (CS). BACKGROUND: CS blood flow cools local tissue precluding transmurality and bidirectional block across MI lesion. METHODS: In a randomized, controlled trial (CS-occlusion = 20, Control = 22), MI ablation was performed during continuous CS pacing to monitor the moment of block. CS was occluded at the ablation site using 1 cm spherical balloon, Swan-Ganz catheter with angiographic confirmation. Ablation was started at posterior mitral annulus and continued up to left inferior pulmonary vein (LIPV) ostium using an irrigated-tip catheter. If block was achieved, balloon was deflated and linear block confirmed. If not, additional ablation was performed epicardially (power ≤25 W). Ablation was abandoned after ∼30 minutes, if block was not achieved. RESULTS: CS occlusion (mean duration -27 ± 9 minutes) was achieved in all cases. Complete MI block was achieved in 13/20 (65%) and 15/22 (68%) patients in the CS-occlusion and control arms, respectively, P = 0.76. Block was achieved with significantly small number (0.5 ± 0.8 vs 1.9 ± 1.1, P = 0.0008) and duration (1.2 ± 1.7 vs 4.2 ± 3.5 minutes, P = 0.009) of epicardial radiofrequency (RF) applications and significantly lower amount of epicardial energy (1.3 ± 2.4 vs 6.3 ± 5.7 kJ, P = 0.006) in the CS-occlusion versus control arm, respectively. There was no difference in total RF (22 ± 9 vs 23 ± 11 minutes, P = 0.76), procedural (36 ± 16 vs 39 ± 20 minutes, P = 0.57), and fluoroscopic (13 ± 7 vs 15 ± 10 minutes, P = 0.46) durations for MI ablation between the 2 arms. Clinically uneventful CS dissection occurred in 1 patient CONCLUSIONS: Temporary spot occlusion of CS is safe and significantly reduces the requirement of epicardial ablation to achieve MI block. It does not improve overall procedural success rate and procedural duration. Tissue cooling by CS blood flow is just one of the several challenges in MI ablation.

Localized reentry within the left atrial appendage: arrhythmogenic role in patients undergoing ablation of persistent atrial fibrillation.

BACKGROUND: Left atrial appendage (LAA) is implicated in maintenance of atrial fibrillation (AF) and atrial tachycardia (AT) associated with persistent AF (PsAF) ablation, although little is known about the incidence and mechanism of LAA AT. OBJECTIVE: The purpose of this study was to characterize LAA ATs associated with PsAF ablation. METHODS: In 74 consecutive patients undergoing stepwise PsAF ablation, 142 ATs were encountered during index and repeat procedures. Out of 78 focal-source ATs diagnosed by activation and entrainment mapping, 15 (19%) arose from the base of LAA. Using a 20-pole catheter, high-density maps were constructed (n = 10; age 57 ± 6 years) to characterize the mechanism of LAA-AT. The LAA orifice was divided into the posterior ridge and anterior-superior and inferior segments to characterize the location of AT. RESULTS: Fifteen patients with LAA AT had symptomatic PsAF for 17 ± 15 months before ablation. LAA AT (cycle length [CL] 283 ± 30 ms) occurred during the index procedure in four and after 9 ± 7 months in 11 patients. We could map 89% ± 8% AT CLs locally with favorable entrainment from within the LAA, which is suggestive of localized reentry with centrifugal atrial activation. ATs were localized to inferior segment (n = 4), anterior-superior segment (n = 5), and posterior ridge (n = 6) with 1:1 conduction to the atria. Ablation targeting long fractionated or mid-diastolic electrogram within the LAA resulted in tachycardia termination. Postablation, selective contrast radiography demonstrated atrial synchronous LAA contraction in all but one patient. At 18 ± 7 months, 13/15 (87%) patients remained in sinus rhythm without antiarrhythmic drugs. CONCLUSION: LAA is an important source of localized reentrant AT in patients with PsAF at index and repeat ablation procedures. Ablation targeting the site with long fractionated or mid-diastolic LAA electrogram is highly effective in acute and medium-term elimination of the arrhythmia.

Early temporal and spatial regularization of persistent atrial fibrillation predicts termination and arrhythmia-free outcome.

BACKGROUND: Termination of persistent atrial fibrillation (AF) is a valuable ablation endpoint but is difficult to anticipate. We evaluated whether temporal and spatial indices of AF regularization predict intraprocedural AF termination and outcome. OBJECTIVE: The purpose of this study was to test whether temporospatial organization of AF after pulmonary vein isolation (PVI) predicts whether subsequent stepwise ablation will terminate persistent AF or predict outcome. METHODS: In 75 patients with persistent AF, we measured AF cycle length (AFCL), temporal regularity index (TRI, a spectral measure of timing regularity), and spatial regularity index (SRI, cycle-to-cycle variations in spatial vector) between right atrial appendage and proximal and distal coronary sinus before and during stepwise ablation to the endpoint of AF termination. RESULTS: AF termination was achieved in 59 patients (79%) by ablation. AF terminated during PVI in 11 patients, who were excluded from analysis. In the remaining 48 patients, TRI and SRI increased during stepwise ablation, as compared with 16 patients without termination (P<.05). AFCL was prolonged in both groups. From receiver operating characteristics analysis of the first 22 patients (training set), a post-PVI TRI increase predicted AF termination in the latter 42 patients (test set) with a positive predictive value of 96%, negative predictive value of 53%, sensitivity of 71%, and specificity of 91%. Results were similar for SRI. After 36 months, higher arrhythmia-free outcome was observed in patients in whom PVI caused temporospatial regularization in AF. CONCLUSIONS: Temporal and spatial regularization of persistent AF after PVI identifies patients in whom stepwise ablation subsequently terminates AF and prevents recurrence.

Impact of pharmacological autonomic blockade on complex fractionated atrial electrograms.

INTRODUCTION: The influence of the autonomic nervous system on the pathogenesis of complex fractionated atrial electrograms (CFAE) during atrial fibrillation (AF) is incompletely understood. This study evaluated the impact of pharmacological autonomic blockade on CFAE characteristics. METHODS AND RESULTS: Autonomic blockade was achieved with propanolol and atropine in 29 patients during AF. Three-dimensional maps of the fractionation degree were made before and after autonomic blockade using the Ensite Navx system. In 2 patients, AF terminated following autonomic blockade. In the remaining 27 patients, 20,113 electrogram samples of 5 seconds duration were collected randomly throughout the left atrium (10,054 at baseline and 10,059 after autonomic blockade). The impact of autonomic blockade on fractionation was assessed by blinded investigators and related to the type of AF and AF cycle length. Globally, CFAE as a proportion of all atrial electrogram samples were reduced after autonomic blockade: 61.6 +/- 20.3% versus 57.9 +/- 23.7%, P = 0.027. This was true/significant for paroxysmal AF (47 +/- 23% vs 40 +/- 22%, P = 0.003), but not for persistent AF (65 +/- 22% vs 62 +/- 25%, respectively, P = 0.166). Left atrial AF cycle length prolonged with autonomic blockade from 170 +/- 33 ms to 180 +/- 40 ms (P = 0.001). Fractionation decreases only in the 14 of 27 patients with a significant (>6 ms) prolongation of the AF cycle length (64 +/- 20% vs 59 +/- 24%, P = 0.027), whereas fractionation did not reduce when autonomic blockade did not affect the AF cycle length (58 +/- 21% vs 56 +/- 25%, P = 0.419). CONCLUSIONS: Pharmacological autonomic blockade reduces CFAE in paroxysmal AF, but not persistent AF. This effect appears to be mediated by prolongation of the AF cycle length.

Peri-mitral atrial flutter in patients with atrial fibrillation ablation.

BACKGROUND: Peri-mitral atrial flutter (PMFL) is commonly encountered in patients undergoing atrial fibrillation (AF) ablation. OBJECTIVE: The purpose of this study was to determine the electrophysiologic characteristics, procedural success, and medium-term outcomes in patients with PMFL. METHODS: The study consisted of 50 consecutive patients (45 men and 5 women, age 57 +/- 12 years) with PMFL following or during AF ablation. Of the 50 PMFLs, 24 occurred during AF ablation (16 at index ablation and 8 at repeat procedure for recurrent AF), and 26 developed during follow-up. Ablation of PMFL was performed by creating a linear lesion joining the mitral annulus to the left inferior pulmonary vein. RESULTS: The incidence of PMFL was higher in patients with mitral isthmus (MI) ablation performed during AF ablation, prior to the development of PMFL, than in those in whom MI ablation was not performed (23% vs 8%, P = .04). Following the procedure, PMFL was more frequent in patients with prior MI ablation than in those without (41% vs 15%, P <.01). Seventy percent (35/50) were terminated by ablation with 6.4 +/- 6.9 minutes of radiofrequency application. Among patients in whom PMFL terminated, supplemental ablation was required for bidirectional conduction block in 66% (23/35). MI block was achieved in 92% (46/50) using 13.6 +/- 7.4 minutes of ablation. At mean follow-up of 19 +/- 4 months, 96% of patients were free from PMFL. CONCLUSION: PMFL can be terminated by MI ablation, but the procedure is proarrhythmic. Supplemental ablation is necessary to establish bidirectional block of the line despite termination of PMFL in the majority of patients.

Catheter ablation of atrial tachycardia following atrial fibrillation ablation.

Atrial tachycardias represent the second front of atrial fibrillation (AF) ablation. They are frequently encountered during the index ablation for patients with persistent AF and are common following ablation of persistent AF, occurring in half of all patients who have had AF successfully terminated. An atrial tachycardia is rightly seen as a failure of AF ablation, as these tachycardias are poorly tolerated by patients. This article describes a simple, practical approach to diagnosis and ablation of these atrial tachycardias.

Characterization of electrograms associated with termination of chronic atrial fibrillation by catheter ablation.

OBJECTIVES: This study sought to determine the characteristics of atrial electrograms predictive of slowing or termination of atrial fibrillation (AF) during ablation of chronic AF. BACKGROUND: There is growing recognition of a role for electrogram-based ablation. METHODS: Forty consecutive patients (34 male, 59 +/- 10 years) undergoing ablation for chronic AF persisting for a median of 12 months (range 1 to 84 months) were included. After pulmonary vein isolation and roof line ablation, electrogram-based ablation was performed in the left atrium and coronary sinus. Targeted electrograms were acquired in a 4-s window and characterized by: 1) percentage of continuous electrical activity; 2) bipolar voltage; 3) dominant frequency; 4) fractionation index; 5) mean absolute value of derivatives of electrograms; 6) local cycle length; and 7) presence of a temporal gradient of activation. Electrogram characteristics at favorable ablation regions, defined as those associated with slowing (a >or=6-ms increase in AF cycle length) or termination of AF were compared with those at unfavorable regions. RESULTS: The AF was terminated by electrogram-based ablation in 29 patients (73%) after targeting a total of 171 regions. Ablation at 37 (22%) of these regions was followed by AF slowing, and at 29 (17%) by AF termination. The percentage of continuous electrical activity and the presence of a temporal gradient of activation were independent predictors of favorable ablation regions (p = 0.016 and p = 0.038, respectively). Other electrogram characteristics at favorable ablation regions were not significantly different from those at unfavorable ablation regions. CONCLUSIONS: Catheter ablation at sites displaying a greater percentage of continuous activity or a temporal activation gradient is associated with slowing or termination of chronic AF.

Focal arrhythmia confined within the coronary sinus and maintaining atrial fibrillation.

INTRODUCTION: The coronary sinus (CS) is a complex structure comprising a mesh of circumferential muscular fibers with oblique connections to both atria. We describe further evidence for the clinical importance of CS arrhythmogenicity in maintaining atrial fibrillation (AF) in humans. METHODS: Since January 2004, following a sequential approach, the CS and the inferior left atrium were ablated in 144 patients with symptomatic drug refractory AF. Patients were included for analysis when this step resulted in the electrical dissociation of the CS from both atria with restoration of sinus rhythm, but with continued arrhythmic activity in the CS. The electrophysiologic mechanism of the confined arrhythmia was considered as focal activity (automaticity or triggered activity) by the presence of electrograms spanning less than 75% of the cycle length in the CS. RESULTS: After restoration of sinus rhythm, four male patients (3% of the patients, three persistent and one permanent AF) were identified in whom arrhythmia continued within the CS. Repetitive activity confined to the disconnected CS was inconsistent in occurrence, as well as in duration (1 sec to 15 min) and cycle length (from 158 to 380 ms). For all four patients, electrogram mapping of the entire CS was compatible with a focal mechanism. In two patients, bursts alternating with slow dissociated activity suggested automaticity. In one patient, local activity consistently coupled to the previous sinus beat favored triggered activity. CONCLUSIONS: This study provides evidence that the CS may be a potential source of focal rapid activity maintaining AF.