Prospective STAR-Guided Ablation in Persistent Atrial Fibrillation Using Sequential Mapping With Multipolar Catheters.

BACKGROUND: A novel stochastic trajectory analysis of ranked signals (STAR) mapping approach to guide atrial fibrillation (AF) ablation using basket catheters recently showed high rates of AF termination and subsequent freedom from AF. METHODS: This study aimed to determine whether STAR mapping using sequential recordings from conventional pulmonary vein mapping catheters could achieve similar results. Patients with persistent AF<2 years were included. Following pulmonary vein isolation AF drivers (AFDs) were identified on sequential STAR maps created with PentaRay, IntellaMap Orion, or Advisor HD Grid catheters. Patients had a minimum of 10 multipolar recordings of 30 seconds each. These were processed in real-time and AFDs were targeted with ablation. An ablation response was defined as AF termination or cycle length slowing ≥30 ms. RESULTS: Thirty patients were included (62.4±7.8 years old, AF duration 14.1±4.3 months) of which 3 had AF terminated on pulmonary vein isolation, leaving 27 patients that underwent STAR-guided AFD ablation. Eighty-three potential AFDs were identified (3.1±1.1 per patient) of which 70 were targeted with ablation (2.6±1.2 per patient). An ablation response was seen at 54 AFDs (77.1% of AFDs; 21 AF termination and 33 cycle length slowing) and occurred in all 27 patients. No complications occurred. At 17.3±10.1 months, 22 out of 27 (81.5%) patients undergoing STAR-guided ablation were free from AF/atrial tachycardia off antiarrhythmic drugs. CONCLUSIONS: STAR-guided AFD ablation through sequential mapping with a multipolar catheter effectively achieved an ablation response in all patients. AF terminated in a majority of patients, with a high freedom from AF/atrial tachycardia off antiarrhythmic drugs at long-term follow-up. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02950844.

Drivers in AF colocate to sites of electrogram organization and rapidity: Potential synergy between spectral analysis and STAR mapping approaches in prioritizing drivers for ablation.

INTRODUCTION: Stochastic trajectory analysis of ranked signals (STAR) mapping has recently been used to ablate persistent atrial fibrillation (AF) with high rates of AF termination and long-term freedom from AF in small, single-arm studies. We hypothesized that rapidity and organization markers would correlate with early sites of activation (ESA). METHODS: Patients undergoing persistent AF ablation as part of the STAR mapping study were included. Five-minute unipolar basket recordings used to create STAR maps were used to determine the minimum-cycle length (Min-CL) and CL variability (CLV) at each electrode to identify the site of the fastest Min-CL and lowest CLV across the left atrium (LA). The location of ESA targeted with ablation was compared with these sites. Dominant frequency was assessed at ESA and compared with that of neighboring electrodes to assess for regional gradients. RESULTS: Thirty-two patients were included with 83 ESA ablated, with an ablation response at 73 sites (24 AF termination and 49 CL slowing ≥30 ms). Out of these, 54 (74.0%) and 56 (76.7%) colocated to sites of fastest Min-CL and lowest CLV, respectively. Regional CL and frequency gradients were demonstrable at majority of ESA. ESA colocating to sites of fastest Min-CL and lowest CLV were more likely to terminate AF with ablation (odds ratio, 34 and 29, respectively, P = .02). These showed a moderate sensitivity (74.0% Min-CL and 75.3% CLV) and specificity (66.7% Min-CL and 76.9% CLV) in predicting ESA with an ablation response. CONCLUSIONS: ESA correlate with rapidity and organization markers. Further work is needed to clarify any role for spectral analysis in prioritizing driver ablation.

STAR mapping method to identify driving sites in persistent atrial fibrillation: Application through sequential mapping.

INTRODUCTION: The optimal way to map localized drivers in persistent atrial fibrillation (AF) remains unclear. The objective of the study was to apply a novel vector mapping approach called Stochastic Trajectory Analysis of Ranked signals (STAR) in AF. METHODS AND RESULTS: Patients having persistent AF ablation were included. Early sites of activation (ESA) identified on global STAR maps created with basket catheters were used to guide AF ablation post-pulmonary vein isolation (PVI). All patients also had sequential STAR maps created with ≥10 PentaRay recordings of 30 seconds. These were validated offline in their ability to identify the ESA targeted with a study-defined ablation response (AF termination or cycle length [CL] slowing of ≥30 ms). Thirty-two patients were included in whom 92 ESA were identified on the global STAR maps, with 73 of 83 targeted sites demonstrating an ablation response (24 AF termination and 49 CL slowing). Sixty-one out of 73 (83.6%) ESA were also identified on the sequential STAR maps. These showed greater consistency (P < .001), were seen pre- and post-PVI (P < .001) and were more likely to be associated with AF termination on ablation (P = .007). The sensitivity and specificity of sequential mapping for the detection of ESA with an ablation response was 84.9% (95% confidence interval [CI] = 74.6-92.2) and 90.0% (95% CI = 55.5-99.8), respectively. During a follow-up of 19.4 ± 3.7 months, 28 (80%) patients were free from AF/atrial tachycardia. CONCLUSIONS: STAR mapping consistently identified ESA in all patients and the ablation response was compatible with ESA being driver sites. Mechanistically important ESA were successfully identified using sequential recordings.

Ablation in Persistent Atrial Fibrillation Using Stochastic Trajectory Analysis of Ranked Signals (STAR) Mapping Method.

OBJECTIVES: The aim of this study was to demonstrate that a stochastic vector-based mapping approach could guide ablation of atrial fibrillation (AF) drivers as evidenced by ablation response and long-term follow-up outcomes. BACKGROUND: The optimal method for mapping and ablation of AF drivers is yet to be defined. METHODS: Patients undergoing persistent AF ablation were recruited. Patients underwent pulmonary vein isolation (PVI) with further ablation guided by the stochastic trajectory analysis of ranked signals (STAR) mapping method. The proportion of the time an electrode's activation was seen to precede its neighboring electrodes activation was used to determine early sites of activation (ESA). A positive ablation response at ESA was defined as AF termination or cycle length slowing of ≥30 ms. Clinical outcome was defined as recurrence of AF/atrial tachycardia (AT) during a follow-up of 12 months. RESULTS: Thirty-five patients were included (AF duration of 14.4 ± 5.3 months). After PVI, an average of 2.6 ± 0.8 ESA were ablated per patient with study-defined ablation response achieved in all patients. Of the 86 STAR maps created post-PVI, the same ESA was identified on 73.8 ± 26.1% of maps. ESA that resulted in AF termination were more likely to be identified on both pre- and post-PVI maps than those associated with cycle length slowing (23 of 24 vs. 16 of 49; p < 0.001). During a follow-up of 18.5 ± 3.7 months, 28 (80%) patients were free from AF/AT. CONCLUSIONS: The ablation response at ESA suggests they may be drivers of AF. Ablation guided by STAR mapping produced a favorable clinical outcome and warrants testing through a randomized controlled trial. (Identification, Electro-mechanical Characterisation and Ablation of Driver Regions in Persistent Atrial Fibrillation [STAR MAPPING]; NCT02950844).

Development, in vitro validation and human application of a novel method to identify arrhythmia mechanisms: The stochastic trajectory analysis of ranked signals mapping method.

INTRODUCTION: Stochastic trajectory analysis of ranked signals (STAR) is a novel method for mapping arrhythmia. The aim was to describe its development and validation as a mapping tool. METHODS AND RESULTS: The method ranks electrodes in terms of the proportion of the time they lead relative to neighboring electrodes and ascribes a predominant direction of activation between electrodes. This was conceived with the aim of mapping atrial fibrillation (AF) drivers. Validation of this approach was performed in stages. First, in vitro simultaneous multi-electrode array and optical mapping were performed on spontaneously fibrillating HL1 cell cultures, to determine if such a method would be able to determine early sites of activation (ESA). A clinical study acquiring unipolar electrograms using a 64-pole basket for the purposes of STAR mapping in patients undergoing atrial tachycardia (AT) ablation. STAR maps were analyzed by physicians to see if arrhythmia mechanisms could be correctly determined. Mapping was then repeated during atrial pacing. STAR mapping of in vitro activation sequences accurately correlated to the optical maps of planar and rotational activation. Thirty-two ATs were mapped in 25 patients. The ESA accurately identified focal/micro-reentrant ATs and the mechanism of macro-reentrant ATs was effectively demonstrated. STAR method accurately identified four pacing sites in all patients. CONCLUSIONS: This novel STAR method correlated well with the gold standard of optical mapping in vitro and was able to accurately identify AT mechanisms. Further analysis is needed to determine whether the method might be of use mapping AF.

Differences in the upslope of the precordial body surface ECG T wave reflect right to left dispersion of repolarization in the intact human heart.

BACKGROUND: The relationship between the surface electrocardiogram (ECG) T wave to intracardiac repolarization is poorly understood. OBJECTIVE: The purpose of this study was to examine the association between intracardiac ventricular repolarization and the T wave on the body surface ECG (SECGTW). METHODS: Ten patients with a normal heart (age 35 ± 15 years; 6 men) were studied. Decapolar electrophysiological catheters were placed in the right ventricle (RV) and lateral left ventricle (LV) to record in an apicobasal orientation and in the lateral LV branch of the coronary sinus (CS) for transmural recording. Each catheter (CS, LV, RV) was sequentially paced using an S1-S2 restitution protocol. Intracardiac repolarization time and apicobasal, RV-LV, and transmural repolarization dispersion were correlated with the SECGTW, and a total of 23,946 T waves analyzed. RESULTS: RV endocardial repolarization occurred on the upslope of lead V1, V2, and V3 SECGTW, with sensitivity of 0.89, 0.91, and 0.84 and specificity of 0.67, 0.68, and 0.65, respectively. LV basal endocardial, epicardial, and mid-endocardial repolarization occurred on the upslope of leads V6 and I, with sensitivity of 0.79 and 0.8 and specificity of 0.66 and 0.67, respectively. Differences between the end of the upslope in V1, V2, and V3 vs V6 strongly correlated with right to left dispersion of repolarization (intraclass correlation coefficient 0.81, 0.83, and 0.85, respectively; P <.001). Poor association between the T wave and apicobasal and transmural dispersion of repolarization was seen. CONCLUSION: The precordial SECGTW reflects regional repolarization differences between right and left heart. These findings have important implications for accurately identifying biomarkers of arrhythmogenic risk in disease.

Prolonged action potential duration and dynamic transmural action potential duration heterogeneity underlie vulnerability to ventricular tachycardia in patients undergoing ventricular tachycardia ablation.

AIMS: Differences of action potential duration (APD) in regions of myocardial scar and their borderzones are poorly defined in the intact human heart. Heterogeneities in APD may play an important role in the generation of ventricular tachycardia (VT) by creating regions of functional block. We aimed to investigate the transmural and planar differences of APD in patients admitted for VT ablation. METHODS AND RESULTS: Six patients (median age 53 years, five male); (median ejection fraction 35%), were studied. Endocardial (Endo) and epicardial (Epi) 3D electroanatomic mapping was performed. A bipolar voltage of <0.5 mV was defined as dense scar, 0.5-1.5 mV as scar borderzone, and >1.5 mV as normal. Decapolar catheters were positioned transmurally across the scar borderzone to assess differences of APD and repolarization time (RT) during restitution pacing from Endo and Epi. Epi APD was 173 ms in normal tissue vs. 187 ms at scar borderzone and 210 ms in dense scar (P < 0.001). Endocardial APD was 210 ms in normal tissue vs. 222 ms in the scar borderzone and 238 ms in dense scar (P < 0.01). This resulted in significant transmural RT dispersion (ΔRT 22 ms across dense transmural scar vs. 5 ms in normal transmural tissue, P < 0.001), dependent on the scar characteristics in the Endo and Epi, and the pacing site. CONCLUSION: Areas of myocardial scar have prolonged APD compared with normal tissue. Heterogeneity of regional transmural and planar APD result in localized dispersion of repolarization, which may play an important role in initiating VT.

Automated detection of repetitive focal activations in persistent atrial fibrillation: Validation of a novel detection algorithm and application through panoramic and sequential mapping.

INTRODUCTION: Identifying drivers in persistent atrial fibrillation (AF) remains challenging. We sought to validate an automated system for detection of focal activation using basket and PentaRay catheters in AF. METHODS: Patients having ablation for atrial tachycardia (AT) and persistent AF were mapped. Thirty-second unipolar basket and PentaRay recordings were analyzed using CARTOFINDER. Focal activation or "region of interest" (ROI) was defined as more than or equal to 2 consecutive focal activations with one electrode leading relative to its neighbors with QS morphology on the unipolar electrogram. ROI was validated in AT. AF patients were mapped to (1) look for evidence of focal activations on wavefront maps, (2) evaluate whether these were detected as ROI on basket recordings, and (3) whether these sites could be identified on sequential PentaRay recordings. RESULTS: ROIs were identified in five focal ATs but none of 16 reentrant ATs. Twenty-eight AF patients had 35 focal drivers identified from basket wavefront maps with an ablation response in all (16 cycle length slowing and 19 AF termination). Thirty focal activations were detected on basket ROI maps (86%). Twenty-three of 28 patients had sequential PentaRay mapping and 22 of 30 focal drivers in these patients (73%) were identified as ROI. These drivers had greater temporal stability (3.6 ± 0.6 vs 2.7 ± 0.6; P < 0.001), higher recurrence rate (12.4 ± 2.7 vs 7.2 ± 0.9; P < 0.001), and more frequently were associated with AF termination ( P < 0.001) compared with those not identified as ROI. CONCLUSIONS: Focal activations can be detected in AF using sequential recordings. The ablation response at focal sources suggests they may be viable therapeutic targets.

Structural remodeling and conduction velocity dynamics in the human left atrium: Relationship with reentrant mechanisms sustaining atrial fibrillation.

BACKGROUND: Rate-dependent conduction velocity (CV) slowing is associated with atrial fibrillation (AF) initiation and reentrant mechanisms. OBJECTIVE: The purpose of this study was to assess the relationship between bipolar voltage, CV dynamics, and AF drivers. METHODS: Patients undergoing catheter ablation for persistent AF (<24 months) were enrolled. Unipolar electrograms were recorded with a 64-pole basket catheter during atrial pacing at 4 pacing intervals (PIs) during sinus rhythm. CVs were measured between pole pairs along the wavefront path and correlated with underlying bipolar voltage. CV dynamics within low-voltage zones (LVZs <0.5 mV) were compared to those of non-LVZs (≥0.5 mV) and were correlated to driver sites mapped using CARTOFINDER (Biosense Webster). RESULTS: Eighteen patients were included (age 62 ± 10 years). Mean CV at 600 ms was 1.59 ± 0.13 m/s in non-LVZs vs 0.98 ± 0.23 m/s in LVZs (P <.001). CV decreased incrementally over all 4 PIs in LVZs, whereas in non-LVZs a substantial decrease in CV was only seen between PIs 300-250 ms (0.59 ± 0.09 m/s; P <.001). Rate-dependent CV slowing sites measurements, defined as exhibiting CV reduction ≥20% more than the mean CV reduction seen between PIs 600-250 ms for that voltage zone, were predominantly in LVZs (0.2-0.5 mV; 75.6% ± 15.5%; P <.001). Confirmed rotational drivers were mapped to these sites in 94.1% of cases (sensitivity 94.1%, 95% CI 71.3%-99.9%; specificity 77.9%, 95% CI 74.9%-80.7%). CONCLUSION: CV dynamics are determined largely by the extent of remodeling. Rate-dependent CV slowing sites are predominantly confined to LVZs (0.2-0.5 mV), and the resultant CV heterogeneity may promote driver formation in AF.

A Novel Mapping System for Panoramic Mapping of the Left Atrium: Application to Detect and Characterize Localized Sources Maintaining Atrial Fibrillation.

Objectives: This study sought to use a novel panoramic mapping system (CARTOFINDER) to detect and characterize drivers in persistent atrial fibrillation (AF). Background: Mechanisms sustaining persistent AF remain uncertain. Methods: Patients undergoing catheter ablation for persistent AF were included. A 64-pole basket catheter was used to acquire unipolar signals, which were processed by the mapping system to generate wavefront propagation maps. The system was used to identify and characterize potential drivers in AF pre- and post-pulmonary vein (PV) isolation. The effect of ablation on drivers identified post-PV isolation was assessed. Results: Twenty patients were included in the study with 112 CARTOFINDER maps created. Potential drivers were mapped in 19 of 20 patients with AF (damage to the basket and noise on electrograms was present in 1 patient). Thirty potential drivers were identified all of which were transient but repetitive; 19 were rotational and 11 focal. Twenty-six drivers were ablated with a predefined response in 22 of 26 drivers: AF terminated with 12 and cycle length slowed (≥30 ms) with 10. Drivers with rotational activation were predominantly mapped to sites of low-voltage zones (81.8%). PV isolation had no remarkable impact on the cycle length at the driver sites (138.4 ± 14.3 ms pre-PV isolation vs. 137.2 ± 15.2 ms post-PV isolation) and drivers that had also been identified on pre-PV isolation maps were more commonly associated with AF termination. Conclusions: Drivers were identified in almost all patients in the form of intermittent but repetitive focal or rotational activation patterns. The mechanistic importance of these phenomena was confirmed by the response to ablation.

Characterization and consistency of interactions of triggers and substrate at the onset of paroxysmal atrial fibrillation.

AIMS: Initiating mechanisms of atrial fibrillation (AF) remain poorly understood, involving complex interaction between triggers and the atrial substrate. This study sought to classify the transitional phenomena, hypothesizing that there is consistency within and between patients in trigger-substrate interaction during transition to AF. METHODS AND RESULTS: Non-contact left atrial (LA) mapping was performed in 17 patients undergoing ablation for paroxysmal AF. All had spontaneous ectopy. Left atrial activation from the first ectopic to established AF was examined offline to characterize the initiating and transitional sequence of activation. In 57 fully mapped spontaneous AF initiations in 8 patients, all involved interaction of pulmonary venous/LA triggers with a septopulmonary line of block (SP-LOB) also evident in sinus rhythm, by 4 different transitional mechanisms characterized by (i) continuous focal firing: AF resulted from fragmentation of each ectopic wavefront through gaps in the SP-LOB and persisted only while focal firing continued (n = 18/32%) (ii) transient focal firing, wavefront fragmentation at the SP-LOB produced wavelet re-entry that persisted after cessation of an initiating ectopic source (n = 12/21%), (iii) of two separate interacting ectopic foci (n = 15/26%), or from (iv) transiently stable macroreentry (n = 12/21%), around the SP-LOB extending to the LA roof, resulting in progressive wavefront fragmentation. It was found that 79 ± 22% of each of the initiations in individual patients showed the same triggering mechanism. CONCLUSION: Onset of paroxysmal AF can be described by discrete mechanistic categories, all involving interaction of ectopic activity with a common SP-LOB. Within/between-patient consistency of initiations suggests constancy of the interacting triggers and substrate, and supports the concept of mechanistically tailored treatment.

Impact of Catheter Contact Force on Human Left Atrial Electrogram Characteristics in Sinus Rhythm and Atrial Fibrillation.

BACKGROUND: During left atrial mapping, optimal contact parameters minimizing variation secondary to catheter contact are not established. METHODS AND RESULTS: Across 30 patients undergoing first-time atrial fibrillation ablation, 1965 stable mapping points (1409 atrial fibrillation, 556 sinus rhythm), comprising 8-s contact force (CF) and bipolar electrogram data were analyzed. Points were taken in groups at locations with CF or catheter orientation actively changed between acquisitions. Complexes were less positive at higher CF (Spearman ρ, -0.2; P<0.005, both rhythms). Increasing CF at a location significantly increased complex size, but only where initial CF was <10 g, and if the change was ≥4.5 g in sinus rhythm and ≥8 g in atrial fibrillation (P<0.0005, both rhythms): if initial CF was ≥10 g, no change was observed, regardless of CF change (P>0.05, both). Atrial ectopics during sinus rhythm were observed more frequently when CF was ≥10 g (P<0.0005). Increasing CF at a location was associated with an increase in the complex fractionated atrial electrogram interval confidence level score, but only if initial CF was <10 g and CF increased ≥8 g (P=0.003). The dominant frequency and organization index were unaffected by CF (P>0.1 for both). Changing catheter orientation from perpendicular to parallel in atrial fibrillation was associated with smaller, more positive complexes (P=0.001 for both), but no changes in complex fractionated atrial electrogram scores, dominant frequency or organization index (P>0.08 for each). CONCLUSIONS: During left atrial electrogram mapping, including complex fractionated atrial electrogram but not spectral parameter mapping, CF and catheter orientation influence results: consequently, mapping CFs should be ≥10 g to negate the influence of CF. CLINICAL TRIALS REGISTRATION: URL: http://clinicaltrials.gov/. Unique identifier: NCT01587404.

Target indices for clinical ablation in atrial fibrillation: insights from contact force, electrogram, and biophysical parameter analysis.

BACKGROUND: In animal studies of radiofrequency ablation, lesion sizes plateau as the maximum lesion size is reached for an ablation. Lesion parameters are not available in clinical ablations, but preclinical work suggests that these correlate with impedance drop and electrogram attenuation. Characterization of the relationships between catheter contact force, ablation duration, and these surrogate markers of lesion formation may allow us to define targets for effective ablation. METHODS AND RESULTS: Fifteen patients undergoing first-time radiofrequency ablation for nonparoxysmal atrial fibrillation were studied. All were in atrial fibrillation at the time of the procedure. Ablations were performed with an irrigated-tip contact force-sensing catheter in temperature-controlled mode (temperature limited to 48°C, power to 30 W). Included were 285 left atrial static ablations, 247 with additional impedance data. The ablation force time integral (FTI) correlated with the attenuation of the electrogram with ablation (Spearman ρ, -0.14; P=0.02): the relationship plateauing from 500 g·s, a reduction in the electrogram amplitude of 20%. The FTI also correlated with the impedance drop during ablation (Spearman ρ, 0.79; P<0.0005): the relationship was logarithmic, the reduction in the impedance with an increasing FTI also plateauing from 500 g·s, an impedance drop of 7.5%. The ablation duration affected the impedance drop at an FTI if the duration was <10 s. Beyond this time point, the FTI achieved rather than the ablation duration or mean contact force applied determined the impedance drop. CONCLUSIONS: During nonparoxysmal atrial fibrillation ablation, an FTI of 500 g·s should be targeted with ablation duration of ≥10 s. Clinical Trials Registration- URL: http://clinicaltrials.gov/. Unique Identifier: NCT01587404.

Left atrial wall stress distribution and its relationship to electrophysiologic remodeling in persistent atrial fibrillation.

BACKGROUND: Atrial stretch causes remodeling that predisposes to atrial fibrillation. We tested the hypothesis that peaks in left atrial (LA) wall stress are associated with focal remodeling. METHODS AND RESULTS: Nineteen patients underwent LA mapping before catheter ablation for persistent atrial fibrillation. Finite Element Analysis was used to predict wall stress distribution based on LA geometry from CT. The relationship was assessed between wall stress and (1) electrogram voltage and (2) complex fractionated atrial electrograms (CFAE), using CFAE mean (the mean interval between deflections). Wall stress varied widely within atria and between subjects (median, 36 kPa; interquartile range, 26-51 kP). Peaks in wall stress (≥90th percentile) were common at the pulmonary vein (PV) ostia (93%), the appendage ridge (100%), the high posterior wall (84%), and the anterior wall and septal regions (42-84%). Electrogram voltage showed an inverse relationship across quartiles for wall stress (19% difference across quartiles, P=0.016). There was no effect on CFAE mean across quartiles of wall stress. Receiver operating characteristic analysis showed high wall stress was associated with low voltage (ie, <0.5 mV) and electrical scar (ie, <0.05 mV; both P<0.0001) and with absence of CFAE (ie, CFAE mean <120 ms; P<0.0001). However, peaks in wall stress and CFAE were found at 88% of PV ostia. CONCLUSIONS: Peaks in wall stress were associated with areas of low voltage, suggestive of focal remodeling. Although peaks in wall stress were not associated with LA CFAE, the PV ostia may respond differently.

Characterization of fractionated atrial electrograms critical for maintenance of atrial fibrillation: a randomized, controlled trial of ablation strategies (the CFAE AF trial).

BACKGROUND: Whether ablation of complex fractionated atrial electrograms (CFAE) modifies atrial fibrillation (AF) by eliminating drivers or atrial debulking remains unknown. This randomized study aimed to determine the effect of ablating different CFAE morphologies compared with normal electrograms (ie, debulking normal tissue) on the cycle length of persistent AF (AFCL). METHODS AND RESULTS: After pulmonary vein isolation left and right atrial CFAE were targeted, until termination of AF or abolition of CFAE before DC cardioversion. Ten-second electrograms were classified according to a validated scale, with grade 1 being most fractionated and grade 5 normal. Patients were randomly assigned to have CFAE grades eliminated sequentially, from grade 1 to 5 (group 1) or grade 5 to 1 (group 2). An increase in AFCL (mean of left and right atrial appendage) ≥5 ms after a lesion was regarded as significant. CFAE (n=968) were targeted in 20 patients. AFCL increased after targeting 51±35% of grade 1 CFAE, 30±15% grade 2, 12±5% grade 3, 33±12% grade 4, and 8±15% grade 5 CFAE (P<0.01 for grades 1, 2, and 4 versus 5; 3 versus 5, not significant). The proportion of lesions causing AFCL prolongation was unaffected by the order in which CFAE were targeted. CONCLUSIONS: Targeting CFAE is not simply atrial debulking. Ablating certain grades of CFAE increases AFCL, suggesting they are more important in maintaining AF. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00894400.

A broad complex tachycardia with conflicting information from pacing manoeuvres.

A patient with a biventricular implantable cardioverter defibrillator for heart failure had a recurrent broad complex tachycardia and underwent electrophysiologic testing. The tachycardia was induced only with ventricular pacing. There was a 1:1 atrioventricular relationship with simultaneous atrial and ventricular activation. However, atrial pacing during tachycardia suggested atrial dissociation from the circuit. The findings, potential mechanisms, and treatment are discussed.

Intra-coronary guidewire mapping-a novel technique to guide ablation of human ventricular tachycardia.

HYPOTHESIS: Endocardial catheter ablation of ventricular tachycardia (VT) may fail if originating from epicardial or intramural locations. We hypothesized that mapping could be achieved using an angioplasty guidewire in the coronary circulation, to guide trans-coronary ablation. METHODS AND RESULTS: Six patients (2 male), 64 +/- 14 years and previously unsuccessful endocardial VT ablation were studied. Using ECG and existing endocardial mapping data, a coronary artery supplying the predicted VT origin was selected. A 0.014-in angioplasty guidewire was advanced into branches of the artery and connected to an amplifier to record unipolar signals against an indifferent electrode within the inferior vena cava. An uninflated angioplasty balloon was advanced over the wire such that only the distal 5 mm was used for mapping. One VT per patient was mapped (CL 348 +/- 102.1 ms). Diastolic potentials were recorded from all (77.7 +/- 43.8 ms pre-QRS onset) and concealed entrainment demonstrated in 3. Pacemapping during sinus rhythm was used in the remainder due to failure of entrainment (n = 2) or degeneration to VF (n = 1). Following branch identification, cold saline injection causing VT termination was used for further confirmation. Five VTs were ablated using intra-coronary ethanol injection via the central lumen of the inflated over the wire balloon. The other was ablated using radiofrequency energy in a coronary vein adjacent to the target artery, which was too small for an angioplasty balloon. No complications or recurrence of ablated VT was seen over 19 +/- 17 months of follow up. CONCLUSIONS: Intracoronary guidewire mapping is a novel method of electrophysiological epicardial mapping to help guide trans-coronary VT ablation.

Validation of the noncontact mapping system in the left atrium during permanent atrial fibrillation and sinus rhythm.

OBJECTIVES: The aim of this study was to validate noncontact mapping (NCM) in the left atrium (LA) during sinus rhythm and atrial fibrillation (AF). BACKGROUND: Understanding the mechanisms of AF is crucial to the development of novel and effective treatments. Noncontact mapping records global electrical activation simultaneously and therefore has the potential to elucidate these mechanisms. METHODS: Patients underwent catheter ablation of permanent AF guided by NCM. Virtual and contact unipolar electrograms were recorded simultaneously during sinus rhythm and AF from sites spanning the LA and their morphology, amplitude, and timing were compared. The impact of distance from the array to the endocardial surface and electrogram amplitude were analyzed. RESULTS: A total of 22 patients age 52 +/- 9 (mean +/- SD) years were studied. During sinus rhythm, the median (range) morphology correlation and timing difference between contact and virtual atrial electrograms were 0.81 (0.27 to 0.98) and 4.2 (0 to 18.3) ms, respectively. These results were significantly worse than the corresponding far field individual ventricular electrograms; 0.91 (0.53 to 1.0) and 1.7 (0 to 18.3) ms (p < 0.001). For endocardial sites >40 mm from the array, the correlation was significantly worse than sites <40 mm: 0.73 (0.48 to 0.95) versus 0.87 (0.27 to 0.98) (p < 0.001). The correlation during AF was 0.72 (0.24 to 0.98), which deteriorated with increasing distance from the array. In the presence of adenosine induced atrioventricular block the correlation deteriorated 0.67 +/- 0.16 versus 0.79 +/- 0.11 (p < 0.001). CONCLUSIONS: Noncontact mapping can be performed in human LA; however, the accuracy of reconstructed electrograms is poor >40 mm from the center of the array, particularly during AF. Care must be taken interpreting isopotential maps if the entire endocardial surface of the LA is not close to the array.