Atrial Bipolar Voltage Research Articles

Clinical Importance of Tissue Proximity Indication During Pulsed Field Ablation for Atrial Fibrillation: Insights from Initial Experience.

Pulsed field ablation (PFA) for paroxysmal atrial fibrillation (AF) has been gaining worldwide acceptance due to its efficacy and safety. A variable loop circular catheter (VLCC, VARIPULSE, Biosense Webster, Inc.) for PFA, recently launched in Japan, includes a Tissue Proximity Indication (TPI) feature to monitor catheter-tissue contact via impedance. However, the role of TPI during pulmonary vein (PV) isolation (PVI) is unclear. This study aims to evaluate TPI feasibility during PVI and its relationship with acute PV reconnection. Twenty-one paroxysmal AF patients underwent PFA (four ablations per PV at least) using the VLCC. We evaluated the association between TPI-positive site percentages, voltage, left atrial wall thickness on ADAS 3D software, and acute PVI failure sites. Four of 21 patients (8 failure sites) experienced PVI failure after primary PFA. Failure sites had significantly lower TPI-positive site percentages (0±0% vs. 63±27%, p< .001) and higher voltage (3.57±1.35 mV vs. 2.06±1.42 mV, p= .003), but not PV wall thickness. We found that a left atrial bipolar voltage amplitude ≥2.24 mV was determinants of PV gaps with an area under the curve of 0.83 calculating receiver operating characteristic curves. TPI-positive site percentages increased significantly (58±29% to 64±26%, p= .009), while PV gaps decreased from 3/28 PVs (11%) to 2/54 PVs (4%, p= .332) between the first 7 and last 14 cases. Acute PVI failure was significantly associated with poor tissue contact and higher voltage. However, acute PVI failure can be prevented with improved TPI-based contact information.

Electrophysiological assessment of atrial tachycardia substrates in patients with repaired tetralogy of Fallot

Abstract Introduction Adults with repaired tetralogy of Fallot (rToF) are most often referred to Adult Congenital Heart Disease centers for atrial tachycardia (AT) and radiofrequency catheter ablation (RFCA) is often required. A systematic evaluation of the mechanisms and recurrences of arrhythmias in these patients is lacking. Methods 28 patients with rToF referred for catheter ablation to the Interventional Electrophysiology Unit of our center between January 2013 and January 2023 were evaluated. Pts underwent electrophysiologic study (EPS) with 3D electroanatomic high density mapping. Evaluation of right atrial bipolar voltage and activation mapping of the AT was performed. Intra-atrial re-entrant tachycardias (IART), focal AT (FAT), other. Activation mapping was performed to identify the critical isthmus for IART. FATs were localized according to the earliest unipolar signal. Whenever possible, all the induced tachycardias were treated besides the arrhythmia which represented the clinical indication to EPS. RFCA was aimed at the earliest activation point for FAT and at the critical isthmus for IART, anchoring lesion to fixed obstacles (valve annuli or atriotomy scar). All patients provided written informed consent for participating in the study. Results Among 28 adult (age 47±13 years) patients (females n=14, 50%), 53 AT were documented: 34 (64%) IART, 11 (21%) FAT and 8 (15%) atrial fibrillation (AF). Mean tachycardia cycle length (excluding AF) was 307±95 ms. At least 2 ATs were induced in 12 pts during index EPS. Among IARTs, incisional IART (IARTinc, atriotomy and superior and inferior vena cava orifices, SVC and IVC, respectively) was the prevalent critical part of the circuit (n=22, 52%), while CTI was the second mechanism (n=20, 48%). In three pts, due to non-inducibility, a pre-emptive lesion set comprising in one case CTI and in two cases CTI+SVC-atriotomy-IVC line was performed. 2 patient underwent scheduled pulmonary veins isolation and CTI ablation. Among FAT, in 3 cases the AT was mapped in the coronary sinus, in two at the tricuspid annulus, in the remaining at the crista terminalis, at the right appendage base, at the posterolateral incision scar or between atriotomy and SVC. In 6 patients AF was induced but not ablated. During a median follow up of 23 months (interquartile range, 6-37) recurrence occurred in 8 pts (18% of pts, 15% of tachycardias). Patients with recurrences were younger (43±7 vs. 48±17 y, p=0.04); no differences were found according to critical isthmus location (4 CTI and 4 IARTinc, 50%, p=ns). Conclusions Among rToF pts with AT, IART is the prevalent mechanism and atriotomy scar is the prevalent critical isthmus. FAT location is much more variable. Atrial fibrillation burden is not negligible. Long-term freedom from AT in this clinical setting is encouraging.

Integrating clinical variables with magnetic resonance imaging and electroanatomic mapping parameters to predict response to first-time and repeat atrial fibrillation ablation procedures

Abstract Background The heterogeneity in patient response to atrial fibrillation ablation mandates the development of methods to predict clinical outcomes. Several clinical risk scores exist to prognosticate patients post ablation. Magnetic resonance imaging can quantify anatomical and functional atrial properties, whilst electroanatomic mapping data provides unparalleled atrial substrate characterisation. These data could be leveraged to predict ablation outcomes more accurately. Purpose To incorporate magnetic resonance imaging and electroanatomic mapping parameters with clinical variables to predict response to 1) first-time and 2) repeat atrial fibrillation ablation. Methods A retrospective analysis of 123 consecutive patients undergoing first-time atrial fibrillation ablation including pre-procedural atrial magnetic resonance imaging was performed. Data were split into training (n=68) and test (n=55) cohorts depending on data availability for clinical risk score calculation. The APPLE, DR-FLASH, FLAME, HATCH, HATCH+OSA, CHA2Ds2VASc and CAAP-AF scores were calculated for patients in the training cohort. Univariate logistic regression was used to identify variables associated with arrhythmia recurrence which were then combined into a multivariate logistic regression model. Area under the curve receiver operating characteristic (AUC-ROC) analysis was used to compare the ability of clinical risk scores and the combined model to predict arrhythmia recurrence risk after one procedure. The model's ability to predict repeat ablation response was tested in 38 patients who underwent redo procedures. The ROC optimal cut-off score was used to divide patients into two groups (high and low arrhythmia recurrence risk) for time-to-event analysis. Results In univariate analysis, weight, age, hypertension, left atrial ejection fraction and mean left atrial bipolar voltage were associated with arrhythmia recurrence after one procedure. The multivariate logistic regression model achieved an AUC of 0.7491 (95% confidence interval (CI) 0.6269-0.8712) in the training cohort and 0.7457 (95% CI 0.6137-0.8778) in the test cohort for predicting arrhythmia recurrence at 12 months (Figure 1A). Amongst clinical risk prediction tools, CAAP-AF had the highest predictive value (AUC 0.6529, 95% CI 0.5265-0.7793) (Figure 1B). In patients undergoing repeat ablations, the combined model had an AUC of 0.7585 (95% CI 0.5989-0.9182) for predicting arrhythmia recurrence (Figure 2A). The Kaplan-Meier curves showed a higher risk of arrhythmia recurrence in the ‘high recurrence risk’ group at 12 months (log-rank p=0.029) (Figure 2B). Conclusion A logistic regression model integrating clinical, anatomical, functional, and electrophysiological parameters improved the accuracy of atrial fibrillation ablation outcome prediction compared to existing clinical risk scores. The model may be used to predict response to repeat procedures offering the potential to improve the patient selection process.

Atrial functional mitral regurgitation as a marker of atrial remodeling and ablation outcomes in atrial fibrillation patients

Abstract Background Atrial fibrillation (AF) triggers a cascade of atrial remodeling processes, significantly impacting atrial function and the efficacy of ablation therapies. This remodeling fosters the development of atrial cardiomyopathy and atrial dilation, which is linked to the emergence of mitral regurgitation, paving the way for the concept of atrial functional mitral regurgitation (aFMR). Our study delves into the intricate relationship between aFMR and the electrical architecture of the atrium, specifically focusing on left atrial bipolar voltage and the prevalence and extent of low-voltage areas (LVAs) in AF patients. By exploring these associations, this research aims to deepen our understanding of the interplay between the atrial substrate alterations and the development of aFMR. Methods A total of 282 patients were enrolled, who had presented for a redo PVI procedure after experiencing AF recurrence following a previous PVI. All patients received echocardiography prior to the electrophysiological procedure. All procedures were performed using 3D mapping and radiofrequency ablation. Reconnected pulmonary veins were detected in all patients and were re-isolated. The voltage of the electroanatomical points was documented on each of the atrial walls. LVAs were calculated in selected HD maps. Patients were followed-up for one year after the blanking period. Results Our cohort comprised 282 patients, predominantly male (69.4%), with a mean age of 64 years. 56% of the patients presented with persistent AF. LA area was larger in patients with aFMR ≥ 1+ as compared to aFMR &amp;lt; 1+ (17.0 [14.6-19.7] vs 20.6 [16.6-24.7] cm2, p&amp;lt;0.001). We observed significant differences in left atrial voltage and LVA extent between patients with varying degrees of aFMR (Table 1). Upon further investigation Patients with aFMR = 1+ showed significantly lower atrial voltage compared with aFMR &amp;lt; 1+ yet no significant increase in LVAs area. Patients with aFMR = 2 exhibited lower average voltage amplitudes in all atrial regions and larger LVA in the posterior wall, atrial roof, and septum compared to their aFMR &amp;lt; 1+ counterparts. Notably, the recurrence of AF was significantly higher in the AFMR ≥ 1+ (59% vs 46% p=0.027) group within one year of follow-up. aFMR was associated with AF recurrence even after adjusting for sex, age and AF types (HR:1.517, 95% CI: 1.057-2.184, p=0.025). Conclusion The presence of aFMR in AF patients may serve as a marker of progressive atrial remodeling and the onset of left atrial cardiomyopathy, characterized by reduced atrial voltage and increased LVAs. Additionally, aFMR is linked to the outcomes of PVI, suggesting that aFMR should be considered in the decision-making process for AF therapy. Further research is needed to explore the potential reversibility of these changes.Left atrial voltage and low voltage area

Heterogenous atrial conduction in patients with hypertrophic cardiomyopathy and atrial fibrillation

Abstract Background/Introduction Hypertrophic cardiomyopathy (HCM) is characterised by myocardial thickening, fibrosis, and disarray, affecting both ventricles and atria. This pathology extends to atrial tissue, potentially influencing conductivity and contributing to arrhythmias, notably atrial fibrillation (AF). Pulmonary vein isolation to treat AF in HCM patients yields less satisfactory results compared to other patient groups. Improved understanding of the pathophysiology of AF in HCM patients could improve treatment stratification and delivery. Purpose This study aims to analyse atrial conduction properties in HCM patients with AF, compared to age, body mass index and sex-matched control patients. Methods Pre-ablation electroanatomic mapping data from 10 HCM patients and a matched control group of patients with structurally normal hearts undergoing AF ablation was retrospectively analysed. All patients underwent pre-ablation electroanatomic mapping during proximal coronary sinus pacing. This data was analysed using OpenEP software to quantify voltage mapping, conduction velocity and wave collision points. Conduction velocity was calculated using both plane fitting and triangulation methods. Wave collisions were identified by calculating the percentage of points with conduction velocity field divergence values less than -1.5. Results HCM patients exhibited significantly reduced mean left atrial bipolar voltage and greater low voltage burden &amp;lt;0.5mV than matched control patients (1.43mV vs. 2.14mV, p=0.0177; and 38.28% vs. 15.68%, p&amp;lt;0.0001), (Figure 1A and B). Wave collision points were significantly more prevalent in the HCM group (5.4% vs. 1.6%, p=0.0004), indicating more heterogeneous conduction (Figure 1C). Figure 2 shows example of divergence map with local electrograms around wave collision points. Both methods of quantifying conduction velocity showed comparable results. While average conduction velocity showed no statistically significant difference (plane fitting method - 0.61m/s in HCM group vs. 0.64m/s in control group, p = 0.465; triangulation method - 0.61m/s in HCM group, 0.64m/s in control group, p=0.393), a trend toward lower velocities in HCM patients was observed (Figure 1D and 1E). Conclusion HCM patients demonstrate significantly lower bipolar voltage and significantly greater low voltage areas than matched control patients. Atrial conduction in patients with HCM is significantly more heterogenous than matched control patients. These findings highlight marked conduction abnormalities in HCM patients which are likely to contribute to AF pathogenesis.

C46 ELECTROPHYSIOLOGICAL ASSESSMENT OF ATRIAL TACHYCARDIA SUBSTRATES IN PATIENTS WITH REPAIRED TETRALOGY OF FALLOT

Abstract Introduction Adults with repaired tetralogy of Fallot (rToF) experience episodes of atrial tachycardia (AT) and radiofrequency catheter ablation (RFCA) is often required but systematic evaluation of the mechanisms and recurrences is lacking. Methods Between January 2013 and October 2021, 20 rToF patients with AT referred for catheter ablation were enrolled. Electrophysiologic study with 3D electroanatomic mapping with multi–electrode mapping catheters was done, with right atrial bipolar voltage and activation mapping of the AT. Three mechanisms were searched: intra–atrial re–entrant tachycardias (IART), focal (FAT), other. Critical isthmus (CI) for IART was identified with activation mapping. FATs were localized according to the earliest uni/bipolar signal. All induced AT were treated. RFCA was aimed at the earliest activation point for FAT and at the critical isthmus for IART, anchoring lesion to fixed obstacles (valve annuli or scar). Written informed consent was provided. Results Among 20 adult (age 46±14 years) and mainly females (n=11, 55%) enrolled pts, 36 AT were documented: 25 (70%) IART, 10 (27%) FAT and only 1 (3%) had a typical atrioventricular nodal reentrant tachycardia. Mean tachycardia cycle length was 307±95 ms. Two ATs were induced in 11 pts, 3 in 4 pts and 4 in 2 during index EPS. Among IART, cavo–tricuspid isthmus (CTI) was the prevalent CI (n=14, 60%), while incisional IART (IARTinc, atriotomy and superior and inferior vena cava orifices, SVC and IVC, respectively) was the second mechanism (n=9, 39%). In two pts, due to non–inducibility, a pre–emptive lesion set comprising in one case CTI and in the second case CTI+SVC–atriotomy–IVC line was performed. Among FAT, in 3 cases the AT was mapped in the coronary sinus, in two at the tricuspid annulus, other at the crista terminalis, right appendage base, posterolateral scar or between atriotomy and SVC. During a median follow–up of 23 months (interquartile range, 6–37) recurrence occurred in 8 pts (25% of pts, 22% of tachycardias). Pts with recurrences were younger (43±7 vs. 48±17 y, p=0.04); no differences were found according to critical isthmus location (4 CTI and 4 IARTinc, 50%, p=ns). Conclusions Among rToF pts with AT, IART is the prevalent mechanism and CTI is the prevalent CI; atriotomy scar, however, is involved in a substantial portion of the critical isthmuses of the IART; FAT location is much more variable. Long–term freedom from AT in this clinical setting is encouraging.

Left atrial volume affects the correlation of voltage map with magnetic resonance imaging.

The low-voltage area detected by electroanatomic mapping (EAM) is a surrogate marker of left atrial fibrosis. However, the correlation between the EAM and late gadolinium enhancement magnetic resonance imaging (LGE-MRI) has been inconsistent among studies. This study aimed to investigate how LA size affects the correlation between EAM and LGE-MRI. High-density EAMs of the LA during sinus rhythm were collected in 22 patients undergoing AF ablation. The EAMs were co-registered with pre-ablation LGE-MRI models. Voltages in the areas with and without LGE were recorded. Left atrial volume index (LAVI) was calculated from MRI, and LAVI > 62ml/m2 was defined as significant LA enlargement (LAE). Atrial bipolar voltage negatively correlates with the left atrial volume index. The median voltages in areas without LGE were 1.1mV vs 2.0mV in patients with vs without significant LAE (p = 0.002). In areas of LGE, median voltages were 0.4mV vs 0.8mV in patients with vs without significant LAE (p = 0.02). A voltage threshold of 1.7mV predicted atrial LGE in patients with normal or mildly enlarged LA (sensitivity and specificity of 74% and 59%, respectively). In contrast, areas of voltage less than 0.75mV correlated with LGE in patients with significant LA enlargement (sensitivity 68% and specificity 66%). LAVI affects left atrial bipolar voltage, and the correlation between low-voltage areas and LGE-MRI. Distinct voltage thresholds according to the LAVI value might be considered to identify atrial scar by EAM.

Abstract 14068: Reduced Left Atrial Conduction Velocity in Patients With Hypertrophic Cardiomyopathy and Normal Left Atrial Voltage Presenting for Paroxysmal Atrial Fibrillation Ablation

Introduction: Patients with hypertrophic cardiomyopathy (HCM) exhibit abnormal cardiac tissue arrangement characterized as myocardial disarray. The incidence of atrial fibrillation (AF) is increased 4-fold in patient with HCM and confers a 4-fold increased risk of death. Catheter ablation is less effective in HCM, with a 2-fold increased risk of AF recurrence. The mechanisms of AF perpetuation and recurrence in HCM are poorly understood. We sought to investigate the left atrial conduction characteristics in patients with HCM, paroxysmal AF and normal left atrial bipolar voltage. Methods: We analyzed 24 consecutive patients with HCM and 24 consecutive controls, all presenting for radiofrequency (RF) ablation of paroxysmal atrial fibrillation. Only patients with normal left atrial voltage (mean voltage &gt;0.8 mV) were included in the study. Intracardiac electrograms were extracted from CARTO (Biosense Webster Inc.) mapping system and analyzed using custom Matlab/Python code interfacing with Core OpenEP software. Conduction velocity was calculated using local activation time gradients. Results: There was no difference in baseline demographic characteristics or atrial size measured by echocardiography between HCM and control patients. Patients with HCM had significantly reduced atrial conduction velocity and conduction velocity dispersion compared to controls (Fig A,C) [0.62±0.03 m/s vs 0.44±0.04 m/s, p=0.002], despite no differences in bipolar voltage (Fig B,D) or voltage dispersion. Patients with HCM had significantly less freedom from AF than controls after catheter ablation [OR for recurrence 3.3 (1.02-10.90), p&lt;0.05 vs control]. Conclusion: Atrial conduction velocity and dispersion is significantly reduced in patients with HCM and paroxysmal AF, possibly contributing to arrhythmia perpetuation and persistence after catheter ablation. This finding may be useful in characterizing left atrial properties beyond bipolar voltage.

An automatic single beat algorithm to discriminate farfield from nearfield bipolar voltage electrograms from the pulmonary veins

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): “Stiftung für Herzschrittmacher und Elektrophysiologie” Basel, Switzerland Background Confirmation of pulmonary vein (PV) isolation (PVI) during ablation of atrial fibrillation can be challenging due to superimposition of nearfield (NF) PV and farfield (FF) atrial bipolar voltage electrograms (BVE). Purpose To develop an automatic algorithm allowing to discriminate PV nearfield (PV-NF) from atrial farfield (atrial-FF) BVE from a circular mapping catheter during cryoballoon (CB) PVI based on a single-heartbeat analysis. Methods BVEs from a decapolar inner-lumen diagnostic catheter (Achieve, Medtronic) during CB PVI were manually classified as PV-NF, atrial-FF and combined FF-NF signal based on the characteristics and disappearance of the PV signal during isolation (Figure, upper row). BVE power spectra were computed using the fast Fourier transform (FFT) and the automatic classification of PV-NF, atrial-FF and combined FF-NF signals was performed using the power in different frequency bands (Figure, lower row). Support vector machine classifier was used to identify PV-NF BVE due to its highest predictive accuracy for the two classes PV-NF+ (PV-NF only and combined FF-NF) and PV-NF- (atrial-FF only). Validation of the approach was performed by comparison of a subset of 80 random samples, which were classified in addition by five experienced electrophysiologists. Results We analysed a dataset of 355 BVEs from 57 patients. The examples were balanced between the two classes PV-NF+ and PV-NF-. The mean duration (95% CI) of the BVE was 58 ms (26 to 86), 70 ms (50 to 100) and 94 ms (71 to 139) for PV NF, atrial-FF and combined FF-NF, respectively. The overall balanced accuracy including BVE from all PVs was 82.7% (95% CI: 80.3% to 85.1%). The analysis on individual PVs showed an accuracy of 96.6%, 85.2%, 80.8%, and 76.9% for the right inferior, right superior, left inferior and left superior PV, respectively. Validation of the algorithm in the subset of 80 patients showed a comparable accuracy, sensitivity and specificity in PV-NF detection between the automatic algorithm and the experienced electrophysiologists (82.8%, 89.2%, and 76.3%, compared to 85.2%, 91.9%, and 78.5%, respectively). Conclusion A reliable automatic based classification algorithm to identify PV-NF BVE could be developed based on a single-beat analysis. Real-time applications as well as using other electrode configurations may improve local signal interpretation.

Relationship between left atrial strain and left atrial bipolar voltage in patients undergoing catheter ablation for atrial fibrillation

Abstract Background Low-voltage zone (LVZ) in the left atrium (LA) seems to represent fibrosis. LA longitudinal strain assessed by speckle tracking method is known to correlate with the extent of fibrosis in patients with mitral valve disease. Purpose We sought to identify the relationship between LA longitudinal strain and LA bipolar voltage in patients with atrial fibrillation (AF). We tested the hypothesis that LA strain can predict LA bipolar voltage. Methods A total of 96 consecutive patients undergoing initial AF ablation were analyzed. All patients underwent transthoracic echocardiography including 2D speckle tracking measurement on the day before ablation during sinus rhythm (SR group, N=54) or during AF (AF group, N=42). LA longitudinal strain was measured at basal, mid, and roof level of septal, lateral, anterior, and inferior wall in apical 4- and 2-chamber view. Global longitudinal strain (GLS) was defined as an average value of the 12 segments. LA voltage map was created using EnSite system, and global mean voltage was defined as a mean of bipolar voltage of the whole LA excluding pulmonary veins and left atrial appendage. LVZ was defined as less than 1.0 mV. Results There was a significantly positive correlation between GLS and global mean voltage (r=0.708, p&amp;lt;0.001). Multivariate regression analysis showed that GLS and age were independent predictors of global mean voltage. There was a significant negative correlation between global mean voltage and LVZ areas. Conclusions There was a strong correlation between LA longitudinal strain and LA mean voltage. GLS can independently predict LA mean voltage, subsequently LVZ areas in patients with AF. Funding Acknowledgement Type of funding source: None

Determinants of atrial bipolar voltage: Inter electrode distance and wavefront angle

BackgroundLocal bipolar electrogram (EGM) peak-to-peak voltage (Vpp) is currently used to characterise mapped myocardial substrate. However, how interelectrode distance and angle of wavefront incidence affect bipolar, Vpp values, in the current era of multi-electrode mapping is unknown. ObjectivesTo elucidate the effects of tissue and electrode geometry on bipolar Vpp measurements, when mapping healthy versus diseased atrial regions. MethodsA bidomain model of human atrial tissue was used to quantify the influence on Vpp values of various electrode configurations in healthy tissue, and tissue containing an unexcitable region. The orientation angle and interelectrode spacing of a surface bipole, and thickness and depth of the unexcitable core were serially varied. Results were validated with data obtained from isolated porcine hearts. ResultsIn healthy tissue, bipolar Vpp values increased with increasing interelectrode spacing and plateaued beyond a spacing of approximately 4 mm. The bipolar Vpp values in healthy tissue were relatively less sensitive to wavefront orientation angle with large interelectrode spacing. In diseased tissue, on the contrary, with increasing interelectrode spacing, bipolar Vpp values increased linearly without a plateau and were more sensitive to orientation angle. The bipolar Vpp values decreased with increasing thickness of the scar, with larger relative decrease in small bipoles than larger ones. Bipolar Vpp values increased with a progressively intramural location of fixed-size scar and became less distinguishable from healthy tissue especially for smaller interelectrode spacings. ConclusionsThe scalable relationship established for interelectrode distances favour an electric-field-based assessment as opposed to traditional Vpp values as a tool for physiologically relevant measurement for mapping catheters with interelectrode spacing up to 4 mm. This will allow for universal assessment of myocardial health across catheters with varied spacing.

The effect of activation rate on left atrial bipolar voltage in patients with paroxysmal atrial fibrillation.

IntroductionBipolar voltage is used during electroanatomic mapping to define abnormal myocardium, but the effect of activation rate on bipolar voltage is not known. We hypothesized that bipolar voltage may change in response to activation rate. By examining corresponding unipolar signals we sought to determine the mechanisms of such changes.Methods and resultsLA extrastimulus mapping was performed during CS pacing in 10 patients undergoing first time paroxysmal atrial fibrillation ablation. Bipolar and unipolar electrograms were recorded using a PentaRay catheter (4‐4‐4 spacing) and indifferent IVC electrode, respectively. An S1S2 pacing protocol was delivered with extrastimulus coupling interval reducing from 350 to 200 milliseconds. At each recording site (119 ± 37 per LA), bipolar peak‐to‐peak voltage, unipolar peak to peak voltage and activation delay between unipole pairs was measured. Four patterns of bipolar voltage/extrastimulus coupling interval curves were seen: voltage attenuation with plateau voltage >1 mV (48 ± 15%) or <1 mV (22 ± 15%), and voltage unaffected by coupling interval with plateau voltage >1 mV (17 ± 10%) or <1 mV (13 ± 8%). Electrograms showing bipolar voltage attenuation were associated with significantly greater unipolar voltage attenuation at low (25 ± 28 mV/s vs. 9 ± 11 mV/s) and high (23 ± 29 mV/s vs. 6 ± 12 mV/s) plateau voltage sites (P < 0.001). There was a small but significant increase in conduction delay between unipole pairs at sites showing bipolar voltage attenuation (P = 0.026).ConclusionsBipolar electrogram voltage is dependent on activation rate at a significant proportion of sites. Changes in unipolar voltage and timing underlie these effects. These observations have important implications for use of voltage mapping to delineate abnormal atrial substrate.

Comparison of Left Atrial Bipolar Voltage and Scar Using Multielectrode Fast Automated Mapping versus Point-by-Point Contact Electroanatomic Mapping in Patients With Atrial Fibrillation Undergoing Repeat Ablation.

Bipolar voltage criteria to delineate left atrial (LA) scar have been derived using point-by-point (PBP) contact electroanatomical mapping. It remains unclear how PBP-derived LA scar correlates with multielectrode fast automated mapping (ME-FAM) derived scar. We aimed to correlate scar and bipolar voltages from LA maps created using PBP versus ME-FAM. In consecutive patients undergoing repeat AF ablation, 2 separate LA maps were created using PBP and ME-FAM during sinus rhythm before ablation. Contiguous areas in the LA with a bipolar voltage cutoff of ≤0.2 mV represented dense scar; LA scar percentage was calculated for each map. Each LA shell was divided into 9 regions and each region further subdivided into 4 quadrants for additional analysis; mean voltages of all points obtained using PBP versus ME-FAM in each region were compared. Forty maps (20 PBP: mean 228.5 ± 95.6 points; 20 ME-FAM: 923.0 ± 382.6 points) were created in 20 patients. Mapping time with ME-FAM was shorter compared with PBP (13.3 ± 5.3 vs. 34.4 ± 13.1 minutes; P < 0.001). Mean LA scar percentage was higher with PBP compared with ME-FAM (15.5 ± 17.1% vs. 12.8 ± 17.6%; P = 0.04). Mean PBP voltage distribution was lower (compared with ME-FAM) in the septum (0.95 ± 0.73 vs. 1.46 ± 0.99 mV; P = 0.009), posterior wall (0.84 ± 0.42 vs. 1.40 ± 0.83 mV; P = 0.0008), roof (0.78 ± 0.80 vs. 1.39 ± 1.09 mV; P = 0.0003), and right PV-LA junction (0.34 ± 0.25 vs. 0.59 ± 0.50 mV; P = 0.01) regions, while voltages were similar in all other LA regions (all P > 0.05). In AF patients undergoing repeat ablation, bipolar voltage is greater in certain LA segments with ME-FAM compared with PBP mapping.

56-23: Left Atrial Bipolar Voltage Map in a Large AF-Cohort: A prospective, systematic study and its fundamental findings

Aim: Fibro-fatty infiltration is widely considered as a leading cause of heterogenic conduction in experimental studies, further responsible atrial fibrillation (AF). Cardiac low voltage zone (LVZ) is a well-established surrogate of fibro-fatty infiltration by experimental studies and human studies using surgically removed cardiac tissues. However, lack of detailed data in human could systemically establish the baseline values and fundamental characteristics of distribution in a large cohort. We built a large database of patients with AF aiming to establish the fundamental characteristics of impaired myocardium in patients with AF, indicating fibrosis extent and fatty infiltration in atria, and further to correlate to clinical appearances. Subjects: Consecutive 539 patients (309 male (57.3%), age 65 ± 10 years) with highly symptomatic AF (paroxysmal AF: n = 292; persistent AF: n = 247), who underwent a bipolar voltage map (BVM) guided atrial fibrillation ablation, were enrolled into the current study. Methods: A detailed LA-BVM was carried out for each patient using 3D-mapping system (CARTO or NavX) during procedure. LA was divided into 5 zones, i.e. septum (S), anterior (AW), posterior (PW), inferior (IW) and lateral (LW) walls, except LA appendage (LAA). Each zone was further divided in to 9 equally sized blocks. The median value within each block and the area and localization of low voltage zone (LVZ, bipolar amplitude < 0.5 mV) was stored and used for further analysis. Results: Median area of LA-surface, including LA appendage, are 103.6 cm2 (percentiles 5–95% 70.9–160.9 cm2). Median area of LVZ are 0 cm2 (percentiles 5–95% 0.0–32.8 cm2). Median bipolar amplitude is 2.2 mV (percentiles 5–95% 1.0–4.2mV) for the entire LA, 1.8 mV (0.4–4.4mV) on AW, 1.7 mV (percentiles 5–95% 0.5–3.8 mV) on S, 2.4 mV (1.0–5.4 mV) on IW, 2.5 mV (1.1–5.3 mV) on LW, and 2.2 mV (0.6–5.5 mV) on PW, respectively. Median area of LVZ was 0 cm2 for all walls (percentile 5–95%: AW: 0.0–12.7, S: 0.0–12.7, IW: 0.0–2.0, LW: 0.0–0.0, PW: 0.0–8.5, LAA: 0.0–0.0 cm2). The existence of LVZ on AW (n = 113, 21%), S (n = 109, 20.2%) and PW (n = 75, 13.9%) are predominantly frequent than on IW (n = 42, 7.8%), LW (n = 25, 4.6%), and LAA (n = 3, 0.6%) (p < 0.001). The existence of LVZ in patients with persistent AF was significantly greater than those with paroxysmal AF (n = 135 vs. n = 57, p < 0.0001). The area of LVZ in patients with persistent AF was also significantly greater than those with paroxysmal AF (9.0 ± 16.4 vs. 2.1 ± 7.8 cm2, p < 0.001). For the entire LA, average bipolar amplitude in patients with paroxysmal AF is significantly greater than in patients with persistent AF (2.7 ± 1.0 mV vs. 2.0 ± 0.9 mV, p < 0.001). Conclusions: We report that the baseline characteristics on bipolar voltage in human heart in large cohort patients with AF. Further, the area of LVZ in patients with persistent AF is predominantly greater than in patients with paroxysmal AF in line with previous histological studies. The most frequent localization of LVZ is anterior wall, septum and posterior wall.

16-14: Relationship between the long-term results of pulmonary vein isolation and left atrial bipolar voltage during atrial fibrillation rhythm

16-14: Relationship between the long-term results of pulmonary vein isolation and left atrial bipolar voltage during atrial fibrillation rhythm

Image Intensity Ratio, a Novel Magnetic Resonance-Based Measure for Quantification of Left Atrial Fibrosis, Correlates with the Distribution of Atrial Bipolar Voltage

Background Recurrence of atrial fibrillation (AF) after catheter ablation has been associated with left atrial (LA) fibrosis. However, arbitrary units of measure limit the interpatient comparison of delayed enhancement intensity. We sought to quantify LA fibrosis using a novel normalized measure: the image intensity ratio (IIR) of late-gadolinium enhanced magnetic resonance imaging (LGE-MRI). Methods LGE-MRI images (1.5 Tesla) were obtained in 30 patients (37% female, mean age 62 ± 8) prior to first (60%), second (23%), or third (17%) ablation procedure for AF. Multiplanar reformatted images were reconstructed from the stack of 3-D axial image data. Epicardial and endocardial contours were manually drawn around LA myocardium. The IIR, defined as local LA myocardial signal intensity divided by the mean LA blood pool image intensity, was measured for each of 20 sectors created on contiguous axial planes through the LA. Electroanatomic map (EAM) points were registered to the corresponding LGE-MRI images using custom software. Results A total of 2569 EAM points were analyzed. The average bipolar voltage was 0.9 ± 1.0 mV (0.5 between and 0.9 within patient standard deviation). Local IIR was strongly associated with bipolar voltage (Figure, P <.001). Using a generalized estimating equations model clustered by patient and adjusting for age, LA volume, rhythm, gender, CHADS score, and type of AF, each unit increase in local IIR was associated with –1.4 mV decrease in bipolar LA voltage (P <.001). Conclusions Higher IIR values were observed in areas with lower bipolar voltage on EAM. The IIR obtained from LGE-MRI may improve the quantification of LA fibrosis Recurrence of atrial fibrillation (AF) after catheter ablation has been associated with left atrial (LA) fibrosis. However, arbitrary units of measure limit the interpatient comparison of delayed enhancement intensity. We sought to quantify LA fibrosis using a novel normalized measure: the image intensity ratio (IIR) of late-gadolinium enhanced magnetic resonance imaging (LGE-MRI). LGE-MRI images (1.5 Tesla) were obtained in 30 patients (37% female, mean age 62 ± 8) prior to first (60%), second (23%), or third (17%) ablation procedure for AF. Multiplanar reformatted images were reconstructed from the stack of 3-D axial image data. Epicardial and endocardial contours were manually drawn around LA myocardium. The IIR, defined as local LA myocardial signal intensity divided by the mean LA blood pool image intensity, was measured for each of 20 sectors created on contiguous axial planes through the LA. Electroanatomic map (EAM) points were registered to the corresponding LGE-MRI images using custom software. A total of 2569 EAM points were analyzed. The average bipolar voltage was 0.9 ± 1.0 mV (0.5 between and 0.9 within patient standard deviation). Local IIR was strongly associated with bipolar voltage (Figure, P <.001). Using a generalized estimating equations model clustered by patient and adjusting for age, LA volume, rhythm, gender, CHADS score, and type of AF, each unit increase in local IIR was associated with –1.4 mV decrease in bipolar LA voltage (P <.001). Higher IIR values were observed in areas with lower bipolar voltage on EAM. The IIR obtained from LGE-MRI may improve the quantification of LA fibrosis

Nature of Electrogram Fractionation During Atrial Fibrillation

The study by Jadidi et al1 described the locations of areas of continuously fractionated atrial electrograms during atrial fibrillation (AF) using high-resolution endocardial mapping in 9 patients with paroxysmal AF and 9 patients with persistent AF. This study then correlated these areas with the locations of fractionated atrial potentials during sinus rhythm and coronary sinus (CS) pacing in the same patients. Their premise was that fractionation resulted from conduction abnormalities (conduction slowing/block, pivot points, asynchronous activation, and wave collision).2,3 They postulated that areas exhibiting fractionation during all 3 rhythms (AF, sinus rhythm, and CS pacing) may differentiate fixed atrial/anatomic substrate (structural remodeling) from wave collision or functional slow conduction. They were hopeful that a better understanding of these patterns would help identify which of the areas of fractionation were optimal targets for ablation. Article see p 32 The study was carefully designed and executed, as expected from one of the premier AF laboratories in the world. Some of the findings were expected. The left atrial area was greater, the global left atrial bipolar voltage during AF was lower, and the area of continuously fractionated electrograms was greater (although not as a percentage of the overall area) in patients with persistent AF than in patients with paroxysmal AF. Perhaps most important were the findings that were not expected under the premise that fractionated electrograms were exclusively due to conduction abnormalities. First, the continuously fractionated areas during AF (CFE mean, <80 milliseconds) did not exhibit lower voltage than the surrounding areas during AF, nor did those sites exhibit low voltage (<1 mV) during sinus rhythm or CS pacing. The voltage during AF was actually higher in the fractionated areas than in the surrounding areas. There was a surprising inverse relationship between the mean bipolar voltage in AF and …

Relationship between the Long-Term Result of PVI and Left Atrial Bipolar Voltage during AF Rhythm

Background: Atrium scaring is associated with the result of pulmonary vein isolation (PVI) for the atrial fibrillation (AF). Previous reports have been the area or distribution of myocardium fibrosis correlated with the bipolar voltage map on sinus rhythm. We evaluated the relationship between the long-term result of PVI and left atrial bipolar voltage during AF rhythm as a left atrial substrate. Methods: Forty-six consecutive AF patients (61±10 years old, 31 males) from March to December in 2007 underwent electroanatomical mapping (CARTO) during AF prior to circumferential PVI, and were stored the mean peak-to-peak amplitude of the bipolar electograms as a voltage map. If needed, the multi-sessions including the substrate ablation were performed for the recurrence cases. We retrospectively observed the surface area and distribution of the low voltage zones (LVZ) changing cut-off limit from 0.1 mV to 0.8 mV and evaluated the extent of LVZ by counting the LVZ regions (LVZ score; 0–5) at baseline. Results: The mean LA volume was 116±35 ml. During the follow-up (mean; 28 months) 39 patients (84.7%) had no recurrence of AF without any anti-arrhythmic agents (AAAs). When we defined the LVZ areas as below 0.2 mV, the LVZ score correlated with clinical outcome (sensitivity 100%, specificity 87.2%, AUC 0.91). Conclusions: The distribution of the LVZs below 0.2 mV during AF associated the long-term outcome of the PV isolation.