High-density Electroanatomical Mapping Research Articles

Low-voltage areas detected by high-density electroanatomical mapping predict recurrence after ablation for paroxysmal atrial fibrillation.

We aimed to evaluate the extent of atrial fibrosis in paroxysmal atrial fibrillation (AF) and the correlation with ablation outcomes after pulmonary vein antral isolation (PVΑI) using a mapping system with high-resolution and high-spatial sampling. We prospectively enrolled 80 consecutive patients (45 males, median age 60.26 years) with symptomatic paroxysmal AF who were scheduled for PVAI. Prior to PVAI, high-density bipolar voltage mapping (median number of 2,485 points) was carried out during sinus rhythm in all patients. Criteria for an adequate left atrium (LA) shell were>2,000 points. Each acquired point was classified according to the peak-to-peak bipolar voltage electrogram based on two criteria (criterion A: healthy>0.8mV, border zone: 0.4-0.8mV and scarred:<0.4mV, criterion Β: healthy:>0.5mV, border zone: 0.25-0.5mV and scarred:<0.25mV). The extent of low-voltage area<0.4mV significantly predicted atrial tachyarrhythmia recurrence after the blanking period (P=0.002). In univariate analysis, the presence of LA voltage areas<0.4mV more than 10% of the total surface area was the only significant predictor of arrhythmia recurrence. The analysis based on window B cutoff values failed to demonstrate any predictors of arrhythmia recurrence. These data demonstrate that the existence of LA voltage areas<0.4mV more than 10% of the total LA surface area predicts arrhythmia recurrence following PVAI for paroxysmal AF.

Atrial Fibrillation Ablation Guided by a Novel Nonfluoroscopic Navigation System

Introduction and objectivesRhythmia is a new nonfluoroscopic navigation system that is able to create high-density electroanatomic maps. The aim of this study was to describe the acute outcomes of atrial fibrillation (AF) ablation guided by this system, to analyze the volume provided by its electroanatomic map, and to describe its ability to locate pulmonary vein (PV) reconnection gaps in redo procedures. MethodsThis observational study included 62 patients who underwent AF ablation with Rhythmia compared with a retrospective cohort who underwent AF ablation with a conventional nonfluoroscopic navigation system (Ensite Velocity). ResultsThe number of surface electrograms per map was significantly higher in Rhythmia procedures (12 125 ± 2826 vs 133 ± 21 with Velocity; P < .001), with no significant differences in the total procedure time. The Orion catheter was placed for mapping in 99.5% of PV (95.61% in the control group with a conventional circular mapping catheter; P = .04). There were no significant differences in the percentage of PV isolation between the 2 groups. In redo procedures, an ablation gap could be identified on the activation map in 67% of the reconnected PV (40% in the control group; P = .042). The measured left atrial volume was lower than that calculated by computed tomography (109.3 v 15.2 and 129.9 ± 13.2 mL, respectively; P < .001). There were no significant differences in the number of complications. ConclusionsThe Rhythmia system is effective for AF ablation procedures, with procedure times and safety profiles similar to conventional nonfluoroscopic navigation systems. In redo procedures, it appears to be more effective in identifying reconnected PV conduction gaps.

“Window Sliding” analysis combined with high-density and rapid electroanatomical mapping: its efficacy and the outcome of catheter ablation of atrial tachycardia

Atrial tachycardia (AT) is a clinically challenging arrhythmia that can occur based on atrial substrates. Nowadays, a rapid construction of three-dimensional electroanatomical maps, which has an analysis function for complex arrhythmias, named 'Window Sliding' (WS) is available. However, little data has revealed the efficacy of this mapping strategy. The aim of this study was to investigate the efficacy of the WS analysis for AT treatments. All patients underwent electrophysiological studies during ATs and the characteristics of the ATs were analyzed using rapid high-density mapping followed by the WS analysis. RFA was then performed. Fifty-five ATs were identified in 34 patients (63 ± 17 year-old) and in 51 activation maps (cycle length, 322 ± 120 milliseconds) were successfully constructed with 644 ± 433 points per map during 5.3 ± 2.5min. The types of detected ATs were macro-reentries around the mitral (8) and, tricuspid (12) valves, roof-dependent reentry (5), others (13), and focal patterns (13). Of those that underwent RFA, 46 (98%) were treated successfully. Two ATs were abandoned since their critical sites were close to the His bundle and sinoatrial node. During a mean follow-up period of 179 ± 176 days, 7 patients had documented recurrences of AT. This high-density mapping using the WS analysis was useful for creating the entire picture of the ATs in a short time, resulting in favorable RFA outcomes.

Ablación de fibrilación auricular guiada por un nuevo sistema de navegación no fluoroscópica

Introduction and objectivesRhythmia is a new nonfluoroscopic navigation system that is able to create high-density electroanatomic maps. The aim of this study was to describe the acute outcomes of atrial fibrillation (AF) ablation guided by this system, to analyze the volume provided by its electroanatomic map, and to describe its ability to locate pulmonary vein (PV) reconnection gaps in redo procedures. MethodsThis observational study included 62 patients who underwent AF ablation with Rhythmia compared with a retrospective cohort who underwent AF ablation with a conventional nonfluoroscopic navigation system (Ensite Velocity). ResultsThe number of surface electrograms per map was significantly higher in Rhythmia procedures (12 125 ± 2826 vs 133 ± 21 with Velocity; P < .001), with no significant differences in the total procedure time. The Orion catheter was placed for mapping in 99.5% of PV (95.61% in the control group with a conventional circular mapping catheter; P = .04). There were no significant differences in the percentage of PV isolation between the 2 groups. In redo procedures, an ablation gap could be identified on the activation map in 67% of the reconnected PV (40% in the control group; P = .042). The measured left atrial volume was lower than that calculated by computed tomography (109.3 v 15.2 and 129.9 ± 13.2 mL, respectively; P < .001). There were no significant differences in the number of complications. ConclusionsThe Rhythmia system is effective for AF ablation procedures, with procedure times and safety profiles similar to conventional nonfluoroscopic navigation systems. In redo procedures, it appears to be more effective in identifying reconnected PV conduction gaps.Full English text available from: www.revespcardiol.org/en

High Density Mapping of Atrial Fibrillation: Regional Atrial Substrate Abnormalities and Implications for Substrate Ablation

Background: It is well-known that there are progressive changes in AF. However, the use of high density mapping to demonstrate atrial remodelling has not been reported. Objective: We sought to evaluate the utility of high density electroanatomic mapping to demonstrate progressive substrate in patients with paroxysmal and persistent AF. Methods: 33 consecutive patients with AF underwent high-density electroanatomic maps of the LA prior to PVI. The LA was divided into 5 segments for regional analysis of mean bipolar voltage. The Confidense® algorithm was used to collect EGMs from a multipolar Lasso® catheter during distal CS pacing at 600msec (Biosense Webster). Patients with structural heart disease were excluded and comorbidities were evenly matched across both groups. Results: 15 paroxysmal AF and 18 persistent AF patients were studied. Mean age was similar (58.4 ± 10 vs 58.1 ± 7years) and 26 (78%) were male. A mean total of 1600 ± 770 and 1483 ± 773 points were collected in each group. The global mean LA voltage was significantly lower in the persistent AF group (2.05 ± 0.6 vs 1.46 ± 0.4 mV, p < 0.001) and consistent across all 5 segments (Figure). The posterior segment demonstrated the greatest difference in regional voltage between groups (2.13 ± 0.9 vs 1.34 ± 0.5 mV, p < 0.002). Conclusion: High density atrial mapping demonstrates regional LA substrate abnormalities in persistent AF not present in paroxysmal AF. These regions may represent targets for substrate modification in persistent AF

Preliminary experience with high-density electroanatomical mapping for ablation of atrial fibrillation – Comparison of mini-basket and novel open irrigated magnetic ablation catheter in consecutive patients

BackgroundRecently, a novel electroanatomic mapping system enabling rapid and automatic acquisition of high-resolution maps has been introduced. Previous reports focused on system use in combination with a mini-basket catheter. However, a novel system-specific, magnet-enabled ablation catheter eliminates the need for the mini-basket catheter and can potentially reduce procedure complexity and cost. Here we present our first experience from two consecutive case series using both procedural settings. MethodsIn 14 consecutive patients (67±9years, 5 male) with paroxysmal (n=10) or persistent AF (n=4) undergoing de-novo (n=8) or repeat (n=6) AF ablation, left atrial electroanatomical maps were acquired with a mini-basket and in 22 patients (64±9years, 17 male) with paroxysmal (n=4) or persistent AF (n=18) undergoing de-novo (n=12) or repeat (n=10) AF ablation with the new ablation catheter. ResultsBoth complete (7.9 [IQR 4.5–16.2] vs 18.8 [IQR 12.0–25.5] minutes, p=0.005) and partial maps (3.0 [IQR 2.0–4.6] vs 4.5 [IQR 2.0–6.0] minutes, p=0.014) acquired with mini-basket required significantly shorter mapping time and had higher point density: 8832±4809 vs 4460±3914 (p=0.014) and 2483±1774 vs 1111±1926 data points (p=0.002) in partial maps.However, procedural (201±52 vs 159±29min, p=0.004) and fluoroscopy time (33±11 vs 25±6min, p=0.005) was significantly higher in the mini-basket group. Procedural endpoints and complications rates were similar in both groups. ConclusionThe high-density mapping system can successfully be used with both mini-basket catheters and ablation catheters employed for electro-anatomic reconstruction of the left atrium. While mapping is faster and point density higher with the mini-basket, procedure and fluoroscopy times are longer. The clinical significance of those findings needs to be investigated in future and larger studies.

A guide to the porcine anatomy for the interventional electrophysiologist. Fluoroscopy and high density electroanatomical mapping.

Invasive electrophysiology is a rapidly developing field of cardiovascular science with a constant need for inventions and testing of new technologies and concepts. Despite the swine model being an established tool in biomedical research no comprehensive guide for interventional electrophysiologists exists. The aim of the current article is to provide a practical overview of the pig anatomy, fluoroscopic views, and corresponding high density electroanatomic maps using a novel mapping system and a practical guide for interventions and techniques. In 17 pigs, fluoroscopic images of the right atrium, coronary sinus (CS), left atrium, and pulmonary veins as well as the right and left ventricles were obtained and correlated with ultra-high density electroanatomic maps and gross anatomy. Pitfalls of the porcine anatomy are precisely addressed, and alternative access techniques to overcome those issues are suggested. Important differences to human electrophysiological studies are highlighted. Complementary models such as cardiac ischemia induction or renal and pulmonary artery denervation are discussed in detail.

First Case of Automatic His Potential Detection With a Novel Ultra High-density Electroanatomical Mapping System for AV Nodal Ablation

A 74-year old was considered for atrioventricular (AV) nodal ablation in view of atrial fibrillation (AF) with poorly controlled ventricular rate despite being on amiodarone. Targeted AV nodal ablation was successfully performed after identifying the target site for ablation by reviewing an ultra high-density map of the His region produced by automatic electrogram annotation.

Insights from preclinical ultra high-density electroanatomical sinus node mapping

Although sinus node modification by catheter ablation is an established therapy for the treatment of inappropriate sinus tachycardia, there is incomplete understanding of sinus node anatomy and function but also limited electroanatomical mapping data. Recently, an automatic, ultra high-resolution mapping system has been presented to accurately and quickly identify right atrial (RA) geometry and activation patterns but detailed assessment of sinus node activation has not been performed which was one aim of this study. Preclinical experiences are compared with previous sinus node mapping studies in animals and humans, and potential clinical implications for catheter ablation are discussed. In anaesthetized and ventilated 14 pigs, 30 endocardial and 2 eipcardial RA maps were generated using the Rhythmia™ mapping system without complications and earliest activation sites (EAS) and sinus break-out (SBO) were determined. At baseline, EAS and SBO were located anterior to the middle (n = 6) or lower third (n = 8) of the crista terminalis exhibiting a unicentric activation pattern in all cases. Conduction pathways were directed anterior, posterior, superior, or inferior with substantial inter-individual variation in direction, pathway distance, and conduction time. Orciprenaline, propranolol, or amiodarone shifted endocardial activation with considerable variation between animals with inconsistent patterns. Multicentric activation was found in one case after orciprenaline infusion. Sequential endocardial and epicardial high-density mapping of the RA was performed in two animals and showed a high congruence of the sinus node activation in the endo- and the epicardial map. Ultra high-density mapping allows fast, simple, and very detailed assessment of sinus node activation. Future studies are clearly needed to evaluate novel mapping and ablation strategies for an improved understanding of sinus node disease and better outcomes.

Arrhythmogenic Right Ventricular Cardiomyopathy

A 52-year-old male patient, a former competitive athlete, was admitted to the hospital because of recurrent episodes of palpitations and presyncope, which occurred while he was running in the course of the previous 12 months. Family history was significant for a first-degree cousin who received an implantable cardioverter-defibrillator (ICD) at 38 years of age because of an unclassified cardiomyopathy. An initial resting 12-lead ECG showed sinus rhythm at a heart rate of 57 beats per minute with an atypical right bundle-branch block, extensive notching of the QRS complex in leads V1 to V3, visible late potentials (resembling epsilon waves) in the inferolateral leads, T-wave inversions in leads V1 to V4, and one ventricular beat with left bundle branch block morphology and superior axis as well (Figure 1, top). Exercise testing induced a sustained ventricular tachycardia (VT) at a rate of 200 beats per minute with left bundle-branch block morphology. Ischemic heart disease was ruled out by coronary angiography. Transthoracic echocardiography (TTE), cardiac magnetic resonance (CMR), and right ventricular (RV) angiography demonstrated RV dilatation, a reduced RV function with wall thinning, and akinesis/dyskinesis of the RV apex, inferior wall, and the subtricuspid area (white arrows), and late gadolinium enhancement within the RV and left ventricular (LV) lateral wall, as well (Figure 2). Subsequently, an electrophysiological (EP) study including high-density electroanatomic voltage mapping was performed with the induction of a nonsustained VT with left bundle-branch block morphology and superior axis (Figure 1, bottom) at a rate of 230 beats per minute. Electroanatomic voltage mapping demonstrated low-voltage areas and scar within the RV corresponding to the regional wall motion abnormalities (Figure 3). Endomyocardial biopsies taken from the RV septum revealed some fibrotic infiltration surrounding the myocytes. Genetic testing yielded a severe heterozygous mutation of desmoplakin at position E1181, resulting in a …

Electrical Homogenization of Ventricular Scar by Application of Collagenase

Background— Radiofrequency ablation for ventricular tachycardia is an established therapy. Use of chemical agents for scar homogenization represents an alternative approach. The purpose of this study was to characterize the efficacy of collagenase (CLG) application on epicardial ventricular scar homogenization. Methods and Results— Myocardial infarcts were created in Yorkshire pigs (n=6) by intracoronary microsphere injection. After 46.6±4.3 days, CLG type 2, type 4, and purified CLG were applied in vitro (n=1) to myocardial tissue blocks containing normal myocardium, border zone, and dense scar. Histopathologic studies were performed to identify the optimal CLG subtype. In vivo high-density electroanatomic mapping of the epicardium was also performed, and border zone and dense scar surface area and late potentials were quantified before and after CLG-4 application (n=5). Of the CLG subtypes tested in vitro, CLG-4 provided the best scar modification and least damage to normal myocardium. During in vivo testing, CLG-4 application decreased border zone area (21.3±14.3 to 17.1±11.1 mm 2 , P =0.043) and increased dense scar area (9.1±10.3 to 22.0±20.6 mm 2 , P =0.043). The total scar area before and after CLG application was 30.4±23.4 and 39.2±29.5 mm 2 , respectively ( P =0.08). Late potentials were reduced by CLG-4 application (28.8±21.8 to 13.8±13.1, P =0.043). During CLG-4 application (50.0±15.5 minutes), systolic blood pressure and heart rate were not significantly changed (68.0±7.7 versus 61.8±5.3 mmHg, P =0.08; 77.4±7.3 versus 78.8±6.0 beats per minute, P =0.50, respectively). Conclusions— Ventricular epicardial scar homogenization by CLG-4 application is feasible and effective. This represents the first report on bioenzymatic ablation of arrhythmogenic tissue as an alternative strategy for lesion formation.

Characterization of myocardial scars: Electrophysiological imaging correlates in a porcine infarct model

Definition of myocardial scars as identified by electroanatomic mapping is integral to catheter ablation of ventricular tachycardia (VT). Myocardial imaging can also identify scars prior to ablation. However, the relationship between imaging and voltage mapping is not well characterized. The purpose of this study was to verify the anatomic location and heterogeneity of scars as obtained by electroanatomic mapping with contrast-enhanced MRI (CeMRI) and histopathology, and to characterize the distribution of late potentials in a chronic porcine infarct model. In vivo 3-dimensional cardiac CeMRI was performed in 5 infarcted porcine hearts. High-density electroanatomic mapping was used to generate epicardial and endocardial voltage maps. Scar surface area and position on CeMRI were then correlated with voltage maps. Locations of late potentials were subsequently identified. These were classified according to their duration and fractionation. All hearts underwent histopathological examination after mapping. The total dense scar surface area and location on CeMRI correlated to the total epicardial and endocardial surface scar on electroanatomic maps. Electroanatomic mapping (average of 1,532 ± 480 points per infarcted heart) showed that fractionated late potentials were more common in dense scars (<0.50 mV) as compared with border zone regions (0.51 to 1.5 mV), and were more commonly observed on the epicardium. In vivo, CeMRI can identify areas of transmural and nontransmural dense scars. Fractionated late diastolic potentials are more common on the epicardium than the endocardium in dense scar. These findings have implications for catheter ablation of VT and for targeting the delivery of future therapies to scarred regions.

Ablation of Ventricular Tachycardia in Patients with Ischemic Heart Disease Using Rotational Angiography (DynaCT) Guided Substrate Mapping Exclusively: Intermediate Term Results

Aim: We evaluated the safety, procedural efficacy and outcomes of ablation of Ventricular Tachycardia (VT) in Ischemic Heart Disease patients using Rotational Angiography and Electroanatomical 3D based substrate mapping strategy exclusively. Methods: Six consecutive patients with a history of MI and hemodynamically unstable drug resistant VT were studied. High-density electroanatomic mapping was performed during sinus rhythm using the NavX velocity (SJM) system. In four patients real time 3D reconstruction of Left Ventricle was done using DynaCT system (Seimens). The scar tissue (Local Voltage- 0.2–0.5 mV) and Low Voltage Areas (Local voltage- 0.5–1.5 mV) were identified. The RF ablation was performed using a 4 mm ablation catheter and the isthmus ablated in 4 patients whereas scar tissue isolation was done in 2 patients. VT induction was done only after RF ablation. Result: Post ablation the no VT was inducible. During the follow-up (18±3.9 months), spontaneous VT was not recorded in any patient on regular ICD interrogation. Conclusion: Substrate mapping can be used to identify the arrhythmogenic tissue and guide VT ablation. This therapeutic strategy may be considered routinely/increasingly in the management of patients with multiple hemodynamically unstable VTs. The use of real time 3D reconstruction (DynaCT) can increase the safety of the procedure.

Efficacy of bundle ablation for cavotricuspid isthmus-dependent atrial flutter: combination of the maximum voltage-guided ablation technique and high-density electro-anatomical mapping

Pathological studies have demonstrated that the cavotricuspid isthmus (CTI) is often composed of discrete muscle bundles, which are thought to be represented electrically as high-amplitude electrograms. Based on this observation, we visualized the bundles using an electro-anatomical mapping system (EAMS) and investigate the efficacy of bundle ablation which is an ablation method for selectively targeting high-voltage sites obtained by high-density electro-anatomical mapping along the CTI. Sixty patients with atrial flutter were randomly assigned to cavotricuspid isthmus ablation using a conventional anatomical approach (Group 1) or bundle ablation approach (Group 2). In Group 2, CTI was mapped in detail with EAMS, and we visualized the bundles that were 1.5 mV or more on a bipolar voltage map. Radiofrequency (RF) ablation was delivered sequentially from the maximum voltage site at the shortest distance of the bundle until bidirectional block was achieved. Bidirectional block was achieved in all patients. Mean ablation times (Group 1, 1,392 + or - 960 s; Group 2, 638 + or - 342 s, p < 0.01), the mean number of RF applications (Group 1, 31.7 + or - 23.6; Group 2, 13.0 + or - 7.0, p < 0.01), and fluoroscopy times (Group 1, 50.4 + or - 28.3 min; Group 2, 42.3 + or - 21.3 min, p < 0.01) were significantly shorter in Group 2 than those in Group 1. Bundle ablation at CTI is highly effective for achieving a bidirectional block requiring shorter ablation times, shorter fluoroscopy times, and fewer RF applications.

Distinguishing epicardial fat from scar: Analysis of electrograms using high-density electroanatomic mapping in a novel porcine infarct model

The presence of epicardial fat can confound the quantification of scar during transpericardial electroanatomic mapping. The electrogram (EGM) characteristics of epicardial fat have not been systematically compared with infarct scar using gross and histopathological analysis as a gold standard. The purpose of this study was to compare the EGM characteristics of epicardial fat with infarct scar. A closed-chest infarction was created in 40-50 kg pigs by occlusion of the circumflex artery for 150 minutes using an angioplasty balloon. This artery was chosen to minimize any potential overlap of epicardial fat with infarct and to spare any septal involvement. After 4-12 weeks of infarct healing, epicardial mapping was performed. EGMs in low-voltage regions (<1.5 mV) were analyzed, and bipolar amplitude, duration, number of deflections, and the presence of late potentials were recorded. Statistical analysis was performed using unpaired t-test and chi(2) analysis. Gross and histopathological examination was used to confirm areas of fat and infarct scar. Seven porcine hearts were analyzed after high-density epicardial mapping (364 +/- 92 points) was performed 48 +/- 19 days after infarction. The mean bipolar EGM amplitude was similar in fat and scar (0.77 +/- 0.34 vs. 0.75 +/- 0.38 mV; P = not significant). The mean EGM duration was longer in scar than in fat (68.8 +/- 18.9 vs. 50.1 +/- 11.6 ms; P <.0001) and exhibited more fractionation (8.5 +/- 3.1 vs. 4.7 +/- 1.8 deflections; P <.0001). The presence of late potentials was 99% specific for scar. Further, areas of fat >4 mm in thickness registered low-voltage bipolar EGMs. Scar from healed myocardial infarction exhibits more fractionation and longer EGM duration when compared with fat. Late potentials are highly specific for locating infarct scars.

Synchronous Ventricular Pacing without Crossing the Tricuspid Valve or Entering the Coronary Sinus—Preliminary Results

Right ventricular apical (RVA) pacing promotes tricuspid regurgitation (TR), electromechanical dyssynchrony, and ventricular dysfunction. We tested a novel intramyocardial bipolar lead to assess whether stimulation of the atrioventricular septum (AVS) produces synchronous ventricular activation without crossing the tricuspid valve (TV). A lead with an active external helix and central pin was placed on the AVS and the RVA in three dogs. High-density electroanatomic (EA) mapping was performed of both ventricles endocardially and epicardially. Intracardiac echocardiography was used to access ventricular synchrony. The lead was successfully deployed into the AVS in all cases with consistent capture of the ventricular myocardium without atrial capture or sensing. The QRS duration was less with AVS compared with RVA pacing (89 +/- 4 ms vs. 100 +/- 11 ms [P < 0.0001, GEE P = 0.03]). There was decreased delay between color Doppler M-mode visualized peak contraction of the septum and the mid left ventricular free wall with AVS compared with RVA pacing (89 +/- 91 ms vs. 250 +/- 11 ms [P < 0.0001, GEE P = 0.006]). Activation time between the mid septum and mid free wall was shorter with AVS versus RVA pacing (20.4 +/- 7.7 vs. 30.8 +/- 11.6 [P = 0.01, GEE P = 0.07]). The interval between QRS onset to earliest free wall activation was shorter with AVS vs. RVA pacing (19.2 +/- 6.4 ms vs. 31.1 +/- 11.7 ms [P = 0.005, GEE P = 0.02]). The AVS was successfully paced in three dogs resulting in synchronous ventricular activation without crossing the TV.

Pathophysiologic basis of autonomic ganglionated plexus ablation in patients with atrial fibrillation

The intrinsic cardiac autonomic nervous system (ganglionated plexuses [GP]) plays a significant role in the initiation and maintenance of atrial fibrillation (AF) in both experimental models and AF patients. Left atrial GP, located in epicardial fat pads and the ligament of Marshall, contain afferent neurons from the atrial myocardium and the central autonomic nervous system, efferent neurons (cholinergic and adrenergic neurons), and interconnecting neurons, which allow communication between GP. Stimulation of the GP produces both parasympathetic stimulation (markedly shortens action potential duration) and sympathetic stimulation (increases calcium transient) in the pulmonary vein (PV) myocardium and atrial myocardium. In a canine model, GP stimulation resulted in early afterdepolarizations, and calcium transient triggered firing in the adjacent PV and initiated AF. Fractionated atrial potentials (FAP) were consistently located in the left atrium close to the stimulated GP. Ablation of the stimulated GP eliminated the FAP surrounding the GP. In patients with paroxysmal AF, epicardial and endocardial high-frequency stimulation produced a positive vagal response (transient AV block during AF and hypotension), allowing the identification and localization of five major left atrial GP (superior left GP, inferior left GP, Marshall tract GP, anterior right GP, inferior right GP). High-density electroanatomic maps of the left atrium and PVs obtained during AF showed the FAP are located in four main left atrial areas (left atrial appendage ridge FAP area, superior-left FAP area, inferoposterior FAP area, anterior-right FAP area). All five GP are located within one of the four FAP areas. In 63 patients with paroxysmal AF, GP ablation alone (before PV antrum isolation) significantly decreased the occurrence of PV firing (47/63 patients before ablation vs 9/63 patients after ablation, P <.01). GP ablation also decreased the inducibility of sustained AF (43/63 patients vs 23/63 patients, P <.01) and markedly reduced or eliminated the left atrial FAP areas.

Abstract 4646: Visually-Guided Ablation of the Pulmonary Venous Antrum Using a Compliant Balloon Catheter

Introduction: During AF ablation, placing contiguous point ablations to electrically isolate the PVs can be technically challenging. While balloon ablation catheters (BACs) using various energy sources can facilitate this procedure, they are limited by the relatively distal nature of the level of isolation; the PV antra remain largely un-ablated. This report details the in vivo evaluation of a compliant BAC with 1) the capability for endoscopic real-time visualization of the target tissue, and 2) an adjustable short arc of light energy for ablation. Methods: In 3 normal pigs, transseptal access was achieved followed by placement of a deflectable sheath and the BAC (Cardiofocus Inc). Once in position, a 30° arc of laser energy (980 nm) was manipulated to create an isolating antral lesion set. PV isolation was confirmed using a circular mapping catheter. The level of isolation was also visualized by high-density electroanatomical mapping (NavX, St Jude Medical Inc). Results: The BAC was able to conform to the PV antra (Fig-A/B ); a 3D reconstruction of the BAC while in position is shown in Fig C . Circumferential endoscopic contact was observed for all 4 PVs targeted for ablation (3-RSPVs, 1-LSPV). Electrical PV isolation was achieved for all 4 PVs. The level of RSPV (arrow) isolation is seen on the voltage maps at baseline (Fig D ), post-partial ablation (Fig E ) and post-isolation (Fig F ); shown are PA views. There was no PV stenosis, thrombus formation or atrial perforation. Pathological examination confirmed the lesions to be both transmural and antral in location. Conclusions: The PV antra can be targeted for ablation using this visually-guided compliant balloon ablation system.

Nonlinear Ablation Targeting an Isthmus of Critically Slow Conduction Detected by High-Density Electro anatomical Mapping for Atypical Atrial Flutter

Focused high-density atrial endocardial mapping was performed with a three-dimensional electroanatomical mapping system or a multielectrode basket catheter in six men and two women (mean age = 54 years) with atypical atrial flutter (AFL) to characterize its reentry circuit and identify its isthmus of critically slow conduction (ICSC). Activation mapping revealed figure-8 reentry with ICSC between a surgical atrial scars in three atypical AFLs following atriotomy, and between the crista terminalis (CT) and the inferior (IVC) or superior (SVC) vena cavae in atypical right atrial (RA) AFL in absence of prior atriotomy. Figure-8 double loop reentry was documented in one RA atypical AFL. ICSC was characterized by concealed entrainment with a post-pacing interval identical to the AFL cycle length, and a mid-diastolic fractionated electrogram, 129 +/- 23 ms in duration, spanning the isoelectric line between double potentials on adjacent area of conduction block. All AFLs were successfully ablated with 4.9 +/- 4.3 RF pulses applied at ICSC. A possible mechanism of atypical AFL consists of figure-8 reentry with ICSC between surgical scars in postoperative AFL, and between the CT and the IVC/SVC in RA AFL not preceded by cardiac surgery. Late and partial regeneration of conduction across the atriotomy scar can create an ICSC. Nonlinear ablation targeting ICSC can cure atypical AFL, whether it follows surgery or not.

Atypical atrial flutter originating in the right atrial free wall.

Data from experimental models of atrial flutter indicate that macro-reentrant circuits may be confined by anatomic and functional barriers remote from the tricuspid annulus-eustachian ridge atrial isthmus. Data characterizing the various forms of atypical atrial flutter in humans are limited. In 6 of 160 consecutive patients referred for ablation of counterclockwise and/or clockwise typical atrial flutter, an additional atypical atrial flutter was mapped to the right atrial free wall. Five patients had no prior cardiac surgery. Incisional atrial tachycardia was excluded in the remaining patient. High-density electroanatomic maps of the reentrant circuit were obtained in 3 patients. Radiofrequency energy application from a discrete midlateral right atrial central line of conduction block to the inferior vena cava terminated and prevented the reinduction of atypical atrial flutter in each patient. Atrial flutter has not recurred in any patient (follow-up, 18+/-17 months; range, 3 to 40 months). Atrial flutter can arise in the right atrial free wall. This form of atypical atrial flutter could account for spontaneous or inducible atrial flutter observed in patients referred for ablation and is eliminated with linear ablation directed at the inferolateral right atrium.