Low-voltage Zones Research Articles

Characterization of atrial substrate to predict AF ablation success

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): The study has been financially supported by an investigator-initiated research grant by Biosense Webster (Study ID – IIS-532) (MRM) Background Left atrial (LA) substrate may have mechanistic relevance for ablation of atrial fibrillation (AF). We sought to analyze the relationship between low-voltage zones (LVZ), transition-zones (TrZ) and AF recurrence in patients undergoing pulmonary vein isolation (PVI). Methods We conducted a prospective multicenter study on consecutive patients undergoing PVI-only approach. LVZ and TrZ (0.5-1mV) were analyzed offline on high-density electroanatomical maps collected prior to PVI. Results 262 patients (61±11 years, 31% female) with paroxysmal (130 pts) or persistent (132 pts) AF were included. After 28 months of follow-up, 73 (28%) patients experienced recurrence. An extension of more than 5% LVZ in paroxysmal AF and more than 15% in persistent AF were associated with recurrence (HR=4.4 [2.0-9.8], p<0.001 and HR=1.9 [1.1-3.7], p=0.045, respectively). Significant linear association was found between LVZ and TrZ and between LVZ and left atrial volume index (LAVI) (both p<0.001). One-third of patients had significantly increased LAVI without LVZ. Eight percent of the patients had LVZ despite normal LAVI. Older age, female sex, oncological history and increased AF recurrence characterized this latter subgroup. Conclusions In patients undergoing first PVI, the impact of LVZ on outcomes occurs with lower burden in paroxysmal than persistent AF suggesting that not all LVZs have equal prognostic implications. A proportional area of moderately decreased voltages accompanies LVZ, suggesting a continuous fibrotic substrate instead of the dichotomous division of healthy or diseased tissue. LAVI generally correlates with LVZ but a small subgroup of patients may present with disproportionate atrial remodeling, despite normal LAVI.

Progression and regression in the left atrial substrate in patients with atrial fibrillation: the PROGRESS-AF study

Abstract Funding Acknowledgements Type of funding sources: None. Background Progression or regression of the atrial substrate in atrial fibrillation (AF) has been demonstrated in animal models and human right atrial maps. Dynamic changes over time of the left atrial (LA) substrate in patients with AF have not been evaluated in detail yet. Purpose To evaluate changes of the LA substrate between first and redo AF ablation procedures. Methods In our prospective single center observational study, consecutive patients undergoing first and redo AF ablation during sinus rhythm were included. The LA was divided into anterior, septal, lateral and inferior regions. The veins and posterior segments were excluded from the analysis. In each segment median voltages and area % of spontaneous low voltage zone (LVZ) of the LA (<0.5 mV) were measured and compared between first and second procedure in each patient. Progression/Regression was diagnosed if a significant concordant decrease/increase in the median voltage in at least two regions was observed, respectively. Results In the first procedure 34.055 (1.216 points/patient) and in the second 76.958 (2.748 points/patient) points were analyzed in 28 patients (age: 61.2±9.5 years, 39% female, 39% persistent AF). The time between first and second procedure was 1.2 (0.4-2.3) years. Eleven (39%) patients had spontaneous >5% LVZ at both first and second procedure (p=1). In 17 (60%) patients progression was identified; in 5 patients in all 4 segments, in 8 in 3 and in 4 in 2. In the Progression group the total mean LA voltage (1.28±1.30 vs. 0.76±0.71 mV, p<0.001) and the regional mean voltage in all atrial regions decreased significantly: anterior: 0.80±0.76 vs. 0.52±0.51, p<0.001; septal: 1.04±0.94 vs. 0.68±0.57,p<0.001; lateral: 1.71±1.60 vs. 1.04±1.01, p<0.001; and inferior 1.69±1.58 vs. 0.80±0.62, p<0.001. The % LVZ increased not significantly: 6.3±9.5% vs. 9.8±10.1%, p=0.3. In 11 (40%) patients regression was observed (in 3 patients in 3 regions and in 8 in 2). In the Regression group the total mean LA voltage (1.47±1.35 vs. 1.89±1.56, p<0.001) and the regional mean voltage in all but one atrial regions increased significantly: anterior: 1.60±1.55 vs. 1.84±1.58, p=0.001; lateral: 1.59±1.26 vs. 2.59±1.81, p<0.001; inferior: 1.29±1.10 vs. 1.84±1.33, p<0.001; and septal: 1.36±1.43 vs. 1.25±1.18, p=0.06. The % LVZ decreased not significantly (8.6±9.5% vs. 4.1±10.1%, p=0.1). There was no significant difference in any baseline clinical or echocardiographic parameter between the Progression and Regression group. Conclusions Our preliminary study is the first to report bidirectional dynamic properties of the LA substrate with concordant either progressive or regressive changes of atrial voltage in different atrial regions outside of the PVs following AF ablation. A better understanding of the dynamic changes of the LA substrate could help to differentiate between patients with reversible and despite ablation therapy progressive irreversible atrial structural remodeling.

Anterior mitral line in patients with persistent AF and anterior scar: a multicenter matched comparison. The MiLine Study

Abstract Funding Acknowledgements Type of funding sources: None. Background The benefit of an anterior mitral line (AML) in patients with persistent atrial fibrillation (AF) and anterior atrial scar undergoing ablation has never been investigated. Objective to evaluate the outcomes of AML on top of standard treatment, compared to standard treatment alone (no-AML), in this subset of patients. Methods Patients with persistent AF and anterior low voltage zone (LVZ) treated with AML in three Centers were retrospectively enrolled. These patients were matched in a 1:1 fashion with patients with persistent AF and anterior LVZ, who underwent conventional ablation, in the same centers. Matching parameters were: age, LVZ burden, and repeated ablation. Primary endpoint was AF/atrial tachycardia (AT) recurrence. Results 186 patients (66±9 years, 34% women) were selected and included into two matched groups. Bidirectional conduction block was achieved in 95% of AML. After a median follow-up of 2 years, AF/AT recurrence occurred in 29% of the patients in the AML-group, vs. 48% in the No-AML-group (log-Rank p=0.024) (Figure 1). At Cox-regression multivariate­-analysis left atrial volume (HR 1.03, p=0.006) and AML (HR 0.46, p=0.003) were significantly associated with the primary endpoint. At univariate logistic-regression, lower BMI, older age, extensive anterior LVZ and the position of the left atrial activation breakthrough away from the AML (Figure 2), were associated with first-pass AML block. Conclusion In this retrospective matched analysis of patients with persistent AF and anterior scar, AML on top of standard treatment was associated with improved AF/AT-free survival compared with matched patients treated with standard treatment alone.

In Atrial Fibrillation, Omnipolar Voltage Maps More Accurately Delineate Scar Than Bipolar Voltage Maps

BackgroundOptimal method for voltage assessment in AF remains unclear. ObjectivesThis study evaluated different methods for assessing atrial voltage and their accuracy in identifying pulmonary vein reconnection sites (PVRSs) in atrial fibrillation (AF). MethodsPatients with persistent AF undergoing ablation were included. De novo procedures: voltage assessment in AF with omnipolar voltage (OV) and bipolar voltage (BV) methodology and BV assessment in sinus rhythm (SR). Activation vector and fractionation maps were reviewed at voltage discrepancy sites on OV and BV maps in AF. AF voltage maps were compared with SR BV maps. Repeat ablation procedures: OV and BV maps in AF were compared to detect gaps in wide area circumferential ablation (WACA) lines that correlated with PVRS. ResultsForty patients were included: 20 de novo and 20 repeat procedures. De novo procedure: OV vs BV maps in AF; average voltage 0.55 ± 0.18 mV vs 0.38 ± 0.12 mV; P = 0.002, voltage difference of 0.20 ± 0.07 mV; P = 0.003 at coregistered points and proportion of left atrium (LA) area occupied by low-voltage zones (LVZs) was smaller on OV maps (42.4% ± 12.8% OV vs 66.7% ± 12.7% BV; P < 0.001). LVZs identified on BV maps and not on OV maps correlated frequently to wavefront collision and fractionation sites (94.7%). OV AF maps agreed better with BV SR maps (voltage difference at coregistered points 0.09 ± 0.03 mV; P = 0.24) unlike BV AF maps (0.17 ± 0.07 mV, P = 0.002). Repeat ablation procedure: OV was superior in identifying WACA line gaps that correlated with PVRS than BV maps (area under the curve = 0.89, P < 0.001). ConclusionsOV AF maps improve voltage assessment by overcoming the impact of wavefront collision and fractionation. OV AF maps correlate better with BV maps in SR and more accurately delineate gaps on WACA lines at PVRS.

Correlation of myocardial strain by CMR-feature tracking with substrate abnormalities detected by electro-anatomical mapping in patients with nonischemic cardiomyopathy

BackgroundLate gadolinium enhancement (LGE) detected by cardiac MRI (CMR) has low correlation with low voltage zones (LVZs) detected by electroanatomical mapping (EAM). We aim to study correlation of myocardial strain by CMR- Feature Tracking (FT) alongside LGE with LVZs detected by EAM.MethodsNineteen consecutive CMRs of patients with EAM were analyzed offline by CMR-FT. Peak value of circumferential strain (CS), longitudinal strain (LS), and LGE was measured in each segment of the left ventricle (17-segment model). The percentage of myocardial segments with CS and LS > −17% was determined. Percentage area of LGE-scar was calculated. Global and segment–wise bipolar and unipolar voltage was collected. Percentage area of bipolar LVZ (<1.5 mV) and unipolar LVZ (<8.3 mV) was calculated.ResultsMean age was 62±11 years. Mean LVEF was 37±13%. Mean global CS was −11.8±5%. Mean global LS was −11.2±4%. LGE-scar was noted in 74% of the patients. Mean percentage area of LGE-scar was 5%. There was significant correlation between percentage abnormality detected by LS with percentage bipolar LVZ (r = +0.5, p = 0.03) and combined percentage CS+LS abnormality with percentage unipolar LVZ (r = +0.5, p = 0.02). Per-unit increase in CS increased the percentage area of unipolar LVZ by 2.09 (p = 0.07) and per-unit increase in LS increased the percentage area of unipolar LVZ by 2.49 (p = 0.06). The concordance rates between CS and LS to localize segments with bipolar/unipolar LVZ were 79% and 95% compared to 63% with LGE.ConclusionsMyocardial strain detected by CMR-FT has a better correlation with electrical low voltage zones than the conventional LGE.

PO-03-095 SEX-RELATED DIFFERENCES IN ATRIAL SUBSTRATE IN PATIENTS UNDERGOING PULMONARY VEIN ISOLATION; A PROSPECTIVE, MULTICENTER STUDY

Sex-related differences have been reported among patients undergoing pulmonary vein isolation (PVI). Atrial substrate plays a major role in the outcomes after ablation but sex-related differences in atrial substrate have never been described in detail. We sought to analyze sex-related differences in atrial remodeling (spontaneous low-voltage zones (LVZ)) and their clinical relevance after PVI. We conducted a prospective multicenter study, including consecutive patients undergoing first PVI-only AF ablation. LVZs were analyzed on high-density electroanatomical maps collected with multipolar catheter, prior to PVI. 262 patients (61±11 years, 31% females, 50% persistent AF) were followed for 28 months. In women, LVZs were larger (10% vs. 4% of LA surface (p < 0.001)) and more women had high-burden (>15%) LVZs (24% vs. 8% (p < 0.001)). In spite of women having more advanced atrial remodeling, AF recurrence-free survival was similar between men and women (Log-Rank p=0.2). The presence of >5% LVZ was significantly associated with recurrence in men (HR:3.0, p<0.001) but not in women (HR:1.9, p=0.07). In women, only >15% LVZ was associated with recurrence (HR: 2.7, p=0.02). Women have more widespread LVZ in all LA regions. Despite more extensive atrial remodeling, the efficacy of first PVI-only ablation is similar in men and women, and LVZs become prognostic in women only at high burden (>15%). LVZs seem to have a different prognostic role in men and women.

PO-05-040 APPLICATION OF ELECTROGRAM PEAK FREQUENCY VALUE FOR IDENTIFICATION OF SCAR-RELATED VENTRICULAR TACHYCARDIA ISTHMUS DURING SINUS RHYTHM

Isolated late activation mappings (ILAMs) can identify possible ventricular tachycardia (VT) isthmus during sinus rhythm (SR). The interference of far-field potentials at the deceleration zone (DZ) may cause misleading results. Electrogram peak frequency (PF) has the potential to discriminate between far-field and near-field signals. We aimed to identify the VT isthmus by applying PF over SR substrate maps. Ten patients with scar-related VT (ischemic/nonischemic cardiomyopathy 6/4) were studied. VT isthmuses were identified based on the activation maps, entrainment, and ablation results during tachycardia. The accuracy of PF maps in detecting potential VT isthmuses during SR before ablation was assessed. Twelve VT isthmuses were identified. The bipolar mean voltage and PF of isthmus areas over the pre-ablation SR map were 0.25 ± 0.12 mV and 307.5 ± 54.3 Hz, respectively. All isthmuses were within low voltage zones (LVZ) with PF of more than 250Hz. Before ablation, 11 of 25 (44.0%) DZs identified from ILAM by annotating the last deflection EGMs in LVZ were compatible with VT isthmuses (mean PF 311.0 ± 66.0Hz); mean PF of DZs which were not isthmus locations was 177.6 ± 51.5 Hz. There were 12 of 15 (80.0%) DZs on ILAMs constructed by annotating PF EGMs compatible with VT isthmuses. VT isthmus is mostly located in LVZ (<0.5 mV) with PF value over 250Hz from pre-ablation SR maps. The DZs during SR with a low PF could be bystanders. Identifying DZs by annotating EGMs with PF, rather than last deflections, is better to discriminate critical VT substrates.

Temporal and Spatial Changes of Proarrhythmic Substrate in Premature Ventricular Contraction–Induced Cardiomyopathy

BackgroundThe changes in proarrhythmic substrates and malignant ventricular arrhythmia mechanisms caused by premature ventricular contraction–induced cardiomyopathy (PVCCM) remain unclear. ObjectivesThe goal of this study was to establish the electrophysiological mechanism of how high-load PVC causes malignant arrhythmia. MethodsThirteen swine were exposed to 50% paced PVC from the right ventricular apex for 12 weeks (PVCCM, n = 6) and no pacing for 12 weeks (control, n = 7). Cardiac function was quantified biweekly with echocardiography. Computed tomography scans and electrophysiological examinations were performed monthly to dynamically evaluate the changes in the cardiac structure and the arrhythmogenic substrate. ResultsThe decreases in the cardiac function and ventricular enlargement in the PVCCM group were significant after 12 weeks of PVC stimulation compared with the control group (P < 0.001). Electrophysiological examination found that the ventricular effective refractory period dispersion (0.071 ± 0.008), area of the low-voltage zone (9.41 ± 1.55 cm2), and malignant ventricular arrhythmia inducibility (33.3%) of the PVCCM group increased significantly at week 8 after pacing (P < 0.001 vs the control group); these changes slowed down after 8 weeks. Moreover, the distribution of the low-voltage zone presented obvious spatial heterogeneity, especially in the anterior wall of the right ventricle, accompanied by delayed activation in the sinus rhythm (67 ± 13 milliseconds). Consistently, the proportion of ventricular fibrosis– and expression-related proteins were significantly increased in the PVCCM group (P < 0.001), especially in the right ventricle. Moreover, proteomic analysis confirmed the spatial profile of these fibrotic changes in the PVCCM group. ConclusionsHigh-burden PVC can cause significant temporal and spatial heterogeneity changes in proarrhythmic substrates, which are potentially related to the upregulation of calcium signaling caused by asynchronous activation.

High-density characterization of the sinus rhythm: a new functional substrate map of scar-related atrial tachycardia.

Reentrant atrial tachycardias (ATs) utilize critical isthmus (CI) for the maintenance of the circuit. The electrophysiological characteristics and clinical implications of the targeted CI regions of reentrant ATs during sinus rhythm (SR) were not clear. Therefore, our research aims at studying the electrical properties of the CI sites for scar-related reentrant ATs and the functional substrate mapping identified during SR. Patients mapped with high-density catheters during SR and reentrant ATs were retrospectively analyzed. The CI regions of the reentrant ATs were confirmed by the combination of the activation map and the entrainment. The substrate mapping was analyzed for wavefront propagation, conduction velocity, and electrogram patterns. Twenty patients with 22 reentrant ATs that underwent high-density maps were analyzed at 2 hospitals. Mapping performed during SR identified a scar region of 23.0 ± 13.6% of the left atrium. Regions of the CI in SR were characterized by low voltage (0.3 ± 0.2 mV), conduction slowing (0.4 ± 0.2 m/s), and fractionated electrogram (duration 62.5 ± 13.9 ms). Substrate mapping during SR showed that the regions of the CI located with the low-voltage zone in 16 out of 22 CI (72.7%), the deceleration zone in 15 out of 22 CI (68.2%), and late atrial activation in 12 out of 22 CI (54.5%). Targeting regions of CI achieve 94% of termination or change of the reentrant circuit. At 6.2 ± 7.1 months, there was 75% freedom from atrial arrhythmia. Novel high-density mapping can identify the functional substrates during SR and guide ablation. Low-voltage areas with conduction slowing are putative predictors of the CI for the maintenance of the reentrant ATs.

Abnormal Conduction Zone Detected by Isochronal Late Activation Mapping Accurately Identifies the Potential Atrial Substrate and Predicts the Atrial Fibrillation Ablation Outcome After Pulmonary Vein Isolation.

The presence of abnormal substrate of left atrium is a predictor of atrial fibrillation (AF) recurrence after pulmonary vein isolation. We aimed to investigate the isochronal late activation mapping to access the abnormal conduction velocity for predicting AF ablation outcome. Forty-five paroxysmal AF patients (30 males, 57.8±8.7 years old) who underwent pulmonary vein isolation were enrolled. Isochronal late activation mapping was retrospectively constructed with 2 different windows of interest: from onset of P wave to onset of QRS wave on surface electrocardiography (W1) and 74 ms tracking back from the end of P wave (W2). Deceleration zone was defined as regions with 3 isochrones (DZa) or ≥4 isochrones (DZb) within a 1 cm radius on the isochronal late activation mapping, and the estimated conduction velocity (ECV) are 0.27 m/s and <0.20 m/s for DZa and DZb, respectively in W2. The distribution of deceleration zone was compared with the location of low-voltage zone (bipolar voltage ≤0.5 mV). Any recurrence of atrial arrhythmias was defined as the primary end point during follow ups after a 3-month blanking period. Pulmonary vein isolation was performed in all patients, and there were 2 patients (4.4%) received additional extrapulmonary vein ablation. After a mean follow-up of 12.7±4.5 months, recurrence of AF occurred in 14 patients (31.1%). Patients with the presence of DZb in W2 had higher AF recurrence (Kaplan-Meier event rate estimates: HR, 9.41 [95% CI, 2.61-33.90]; log-rank P<0.0001). There were 52.6% of the DZb locations in W2 comparable to the distributions of low-voltage zone and 47.4% DZb were distributed in the area without low-voltage zone. Deceleration zone detected by isochronal late activation mapping represents a critical AF substrate, it accurately predicts the AF recurrence following ablation in patients with paroxysmal AF.

Anterior mitral line in patients with persistent atrial fibrillation and anterior scar: A multicenter matched comparison—The MiLine study

The benefit of an anterior mitral line (AML) in patients with persistent atrial fibrillation (AF) and anterior atrial scar undergoing ablation has never been investigated. The purpose of this study was to evaluate the outcomes of AML in addition to standard treatment compared to standard treatment alone (no AML) in this subset of patients. Patients with persistent AF and anterior low-voltage zone (LVZ) treated with AML in 3 centers were retrospectively enrolled. The patients were matched in 1:1 fashion with patients having persistent AF and anterior LVZ who underwent conventional ablation in the same centers. Matching parameters were age, LVZ burden, and repeated ablation. Primary endpoint was AF/atrial tachycardia (AT) recurrence. One hundred eight-six patients (age 66 ± 9 years; 34% women) were selected and divided into 2 matched groups. Bidirectional conduction block was achieved in 95% of AML. After median follow-up of 2 years, AF/AT recurrence occurred in 29% of the patientsin the AML group vs 48% in the no AML group (log-rank P = .024). On Cox regression multivariate analysis, left atrial volume (hazard ratio [HR] 1.03; P = .006) and AML (HR 0.46; P = .003) were significantly associated with the primary endpoint. On univariate logistic regression, lower body mass index, older age, extensive anterior LVZ, and position of the left atrial activation breakthrough away from the AML were associated with first-pass AML block. In this retrospective matched analysis of patients with persistent AF and anterior scar, AML in addition to standard treatment was associated with improved AF/AT-free survival compared to standard treatment alone.

Left atrial epicardial adipose tissue exacerbates electrical conduction disturbance in normal-weight patients undergoing pulmonary vein isolation for atrial fibrillation.

Epicardial adipose tissue (EAT) exacerbates both electrical and structural remodeling in obese atrial fibrillation (AF) patients, but the impacts of EAT on atrial arrhythmogenicity remain unclear in normal-weight AF patients. Therefore, we sought to investigate this issue using electroanatomic mapping. We enrolled drug-refractory 105 paroxysmal AF patients in the normal body mass index range (18.5-24.9 kg/m2 ), who had undergone electroanatomic mapping after pulmonary vein isolation (PVI). One day before PVI, we assessed P-wave duration in a 12-lead electrocardiogram and left atrial (LA)-EAT volumes using contrast-enhanced computed tomography. The patients were divided into two groups based on the median LA-EAT volume (16.0 ml); the high LA-EAT group (≥16.0 ml, n = 53) and low LA-EAT group (<16.0 ml, n = 52). We compared P-wave duration, LA conduction velocity and bipolar voltage, the presence of low-voltage zone (<0.5 mV), and LA volume index on echocardiography between the two groups. The LA bipolar voltage, low-voltage zone, and LA volume index were not different between the high and low LA-EAT groups. However, P-wave duration was significantly longer in the high group than in the low group (p < .001). Additionally, the LA conduction velocity was significantly more depressed in the high group than in the low group (p < .001). Multivariate linear regression analysis revealed that LA-EAT volume was correlated with P-wave duration (β = .367, p < .001) and conduction velocity (β = -.566, p < .001), respectively. Increased LA-EAT volumes were associated with electrical conduction disturbance after PVI in normal-weight patients with AF. P-wave duration may be a clinically useful predictor of LA-EAT.

Empirical superior vena cava isolation improves outcomes of radiofrequency re-ablation in pulmonary vein isolation non-responders: A 2-center retrospective study in China.

Pulmonary vein isolation (PVI) is the standard ablation strategy for treating atrial fibrillation (AF). However, the optimal strategy of a repeat procedure for PVI non-responders remains unclear. This study aims to investigate the incidence of PVI non-responders in patients undergoing a repeat procedure, as well as the predictors for the recurrence of repeat ablation. A total of 276 consecutive patients who underwent repeat ablation from August 2016 to July 2019 in two centers were screened. A total of 64 (22%) patients with durable PVI were enrolled. Techniques such as low voltage zone modification, linear ablation, non-PV trigger ablation, and empirical superior vena cava (SVC) isolation were conducted. After the 20.0 ± 9.9 month follow-up, 42 (65.6%) patients were free from atrial arrhythmias. A significant difference was reported between the recurrent and non-recurrent groups in non-paroxysmal AF (50 vs. 23.8%, p = 0.038), diabetes mellitus (27.3 vs. 4.8%, p = 0.02), and empirical superior vena cava (SVC) isolation (28.6 vs. 60.5%, p = 0.019). Multivariate regression analysis demonstrated that empirical SVC isolation was an independent predictor of freedom from recurrence (95% CI: 1.64-32.8, p = 0.009). Kaplan-Meier curve demonstrates significant difference in recurrence between empirical and non-empirical SVC isolation groups (HR: 0.338; 95% CI: 0.131-0.873; p = 0.025). About 22% of patients in repeat procedures were PVI non-responders. Non-paroxysmal AF and diabetes mellitus were associated with recurrence post-re-ablation. Empirical SVC isolation could potentially improve the outcome of repeat procedures in PVI non-responders.

Abstract 14754: Peak Frequency Mapping in Low Voltage Zones Can Identify the Critical Isthmus in Atypical Atrial Flutters

Introduction: Atypical atrial flutters (AFL) are a heterogeneous group of reentrant arrhythmias and can be challenging to map. Peak frequency (PF) mapping is a novel method of identifying local conductivity and may help identify critical portions of myocardial substrate supporting reentry. Hypothesis: The critical isthmuses of left atrial (LA) AFLs demonstrate a combination of low-voltage and high PF. Methods: LA omnipolar voltage and PF maps were generated using the EnSite Precision Mapping System and HD-Grid catheter in 13 patients undergoing AFL ablation. For the purpose of this study, mapping was performed during AFL and normal voltage was defined as ≥ 0.5 mV, low-voltage (LV) 0.1 - 0.5 mV, and scar &lt; 0.1 mV. PF distributions were analyzed in each tissue type. Conduction velocity (CV) was characterized across PF with correlational analysis. The 1-cm radius from sites of arrhythmia termination with ablation were analyzed to characterize mean PF and voltage in nearby myocardial tissue. Results: Mean age was 65.8 ± 9.3 years and 54% were female. A total of 37,331 points were analyzed. Sites of slow conduction included the mitral isthmus (46%), LA roof (23%), pulmonary vein antra (15%), posterior wall (8%), and anterior wall (8%). In normal voltage tissue, mean PF was 337.7 ± 115.4 Hz. LV and scar tissue had left-skewed PF distributions and lower mean PF ( p &lt; 0.0001). While CV had no trend across PF in tissue with normal voltage ( R 2 , 0.0002 to 0.1), there was moderate conduction slowing at higher PF in LV tissue ( R 2 , 0.07 to 0.30). In PF-LV overlay maps, all termination sites resided in regions of LV and high PF ( Figure ). Of the 1-cm areas neighboring termination, 77% had significantly higher PF than the global LA ( p &lt; 0.05), of which 80% had significantly lower mean voltage ( p &lt; 0.01) or mean voltage &lt; 0.5 mV. Conclusions: Sites of arrhythmia termination can be identified in LV tissue at higher PF. Low-voltage, high-PF areas may be critical targets during catheter ablation of atypical AFL.

Abstract 14823: Atrial Electrical Substrates Associated With Atrial Fibrillation Drivers Analyzed With Real-Time Phase Mapping “ExTRa Mapping” in Patients With Persistent Atrial Fibrillation

Introduction: Elucidation of the mechanism of atrial fibrillation (AF) will lead to improved catheter ablation outcomes. However, the electrical substrates on which AF drivers such as meandering rotors and multiple wavelets are likely to appear are still unclear. Methods: Twenty-nine patients (age 68±10 years, eight females) with persistent AF were included in this study. Real-time phase mapping (ExTRa mapping) was performed in the left atrium during AF. After that, electroanatomical mapping such as voltage and activation mapping with HD-grid catheter was performed after conversion to sinus rhythm with cardioversion. According to the nonpassively activated ratio (%NP: the ratio of the form of rotors and/or multiple wavelets to the recording time), the recorded three highest %NP (Active-area) and three lowest %NP areas (Passive-area) were collected in each subject. Electrical property and overlapping with the low-voltage zone (LVZ, voltage amplitude &lt;0.5mV) or mid-voltage zone (MVZ, 0.5-1.0mV) within these areas were assessed and compared between the Active- and the Passive-areas. Results: We analyzed a total of 87 Active- and 84 Passive-areas and the mean %NP were 61±8% and 13±8%, respectively. Signals with ≥4 fractionated components (fractionated electrograms) were seen significantly more in the Active-areas than in the Passive-areas (53% vs. 26%, respectively; p&lt;0.001, Figure A ). However, there was no difference in the conduction velocity (0.70±0.34m/s vs. 0.73±0.30m/s; p=0.577), mean voltage amplitude (1.78±1.54mV vs. 1.71±1.53mV; p=0.794) and coinciding with LVA/MVA (43% vs. 41%; p=0.785) between the Active- and the Passive-areas ( Figure B-D ). Conclusion: AF drivers tended to appear in the area with fractionated electrograms. High %NP areas partly overlapped, but not always coincided with LVA/MVA, as much as low %NP areas.

Abstract 10034: Novel Late-Gadolinium Enhanced Cardiac Magnetic Resonance (LGE-CMR)-Based Computational Heart Paradigm Predicts Optimal Ventricular Tachycardia (VT) Ablation Targets in Arrhythmogenic Right Ventricular (RV) Cardiomyopathy (ARVC)

Introduction: ARVC is an inherited cardiac disease that increases risk of life-threatening VTs in young adults. Catheter ablation, a mainstay of VT treatment in ARVC, remains challenging due to difficulties in identifying optimal VT ablation targets. Hypothesis: Right Ventricular Cardiomyopathy Ablation Targeting (RVCAT) is a novel digital-heart paradigm that accurately predicts the optimal VT ablation targets of ARVC patients. Methods: We retrospectively enrolled 11 ARVC patients; 8 presented with clinical VTs and underwent VT ablation. In all patients, RV hyperenhancement on LGE-CMR was identified. For this study, we developed RVCAT, the first computational heart model integrating RV personalized diffuse and dense fibrosis as VT substrates. Each region was assigned ARVC-specific electrophysiologic properties. VT inducibility was assessed via rapid pacing in each model. If inducible, optimal ablation targets, which rendered the RV substrate non-inducible for each VT, were determined. Targets were compared to electroanatomic voltage maps (EAM), locations of clinical ablations, and clinical records. Results: Personalized model predictions correlated well with clinical observations. All 8 models of the patients with a history of clinical VT had inducible VTs (Fig A). Furthermore, model VT circuit locations matched the clinical description. Substrate distribution in models matched low-voltage zones in EAM. The predicted ablation targets coincided with clinical ablations (Fig B). Results showed that the volume of model ablation lesions was significantly smaller than that of clinical ablations (1.02±0.68 versus 1.45±0.91, p&lt;0.05, Fig C). For the 3 patients who did not have VTs, their corresponding heart models correctly predicted that no VTs would be induced. Conclusions: RVCAT is a novel digital-heart technology for optimal ARVC VT ablation guidance that can be potentially integrated into clinical workflows for augmenting therapeutic precision.

Low voltage area as a predictor of recurrence after a single pulmonary vein isolation procedure: results of the WAVE-MAP AF study

Abstract Background/Introduction Pulmonary vein isolation (PVI) is a recommended approach for atrial fibrillation (AF) ablation procedures. Substrate modification beyond PVI has mixed results but identifying and ablating low voltage zones and ablating those targets in addition to PVI may be beneficial. Electroanatomic mapping is critical to identify subjects that may require further substrate modification. Low voltage area may be predictive of optimal treatment approach. Purpose This was a prospective, multicenter, interventional study of a high-density grid-style mapping catheter (HD Grid) to characterize left atrial low voltage substrate during sinus rhythm (SR) and AF and identify associations with 12 month recurrence rates after a single de novo radiofrequency (RF) ablation using a PVI only approach. Methods This study (NCT03882021) enrolled 300 subjects at 18 centers in Europe and Israel. Subjects underwent de novo RF ablation for paroxysmal AF (PAF) (N=113), early persistent AF (PsAF; AF sustained 7 days to 3 months) (N=86) or non-early PsAF (AF sustained &amp;gt;3 months to 12 months) (N=101). High density voltage maps were collected with HD Grid. Two pre-ablation maps, in SR and AF, were created for each subject (N=196) followed by PVI only ablation. Low voltage area (using cutoffs of 0.1 mV to 1.5 mV) was investigated in SR and AF. Follow up visits were at 3, 6 and 12 months post-ablation, with a 24-hour Holter monitor at 12 months. A Cox proportional hazards model was used to identify associations between mapping data and 12 month AF/atrial flutter (AFL)/atrial tachycardia (AT) recurrence after a single PVI procedure. Results At 12 months, 75.5% of subjects were free from AF/AFL/AT recurrence. On average, PsAF subjects had more low voltage area than PAF subjects in SR and AF. However, while univariate analysis found no correlation between recurrence and PAF or PsAF diagnosis (p=0.1261), those with recurrence had a significantly larger percent left atrial low voltage area under 0.5 mV with simultaneous orthogonal bipole wave configuration (HDW) in both AF (p=0.0011) and SR (p=0.0210) than those without recurrence. Using HDW, low voltage area (identified as &amp;lt;0.5 mV) greater than 28% of the left atrium in SR (HR: 4.82, 95% CI: 2.08–11.18, p=0.0003) and greater than 72% in AF (HR: 5.66, 95% CI: 2.34–13.69, p=0.0001) were associated with a higher risk of AF/AFL/AT recurrence at one year. Conclusion(s) Using a standard cutoff of 0.5 mV, a larger percent low voltage area was associated with increased risk of recurrence in both SR and AF. Future analyses will explore optimal low voltage cutoffs and thresholds predictive of recurrence that may necessitate additional substrate modification beyond PVI. Funding Acknowledgement Type of funding sources: Private company. Main funding source(s): Abbott

Cardiac Computed Tomography-Based Epicardial Adipose Tissue Assessment Reveals Association With Electroanatomical Voltage Mapping in Patients With Atrial Fibrillation.

Epicardial adipose tissue (EAT) around the left atrium (LA) can change the electric conduction of the LA, potentially leading to atrial fibrillation (AF). The aim of this study was to evaluate whether an association existed between EAT and the electrophysiological properties of adjacent atrial myocardium in patients with AF. A total of 201 consecutive patients referred for initial AF catheter ablation were prospectively included. A preprocedural computed tomography scan was performed to assess total and LA-EAT parameters. Detailed point-by-point voltage mapping using an electroanatomical mapping system was realised to assess the LA low-voltage zone (LVZ), defined as an area with bipolar electrograms ≤0.5 mV during sinus rhythm. Ninety-one (91) patients (45.3%) presented at least one LVZ. They had a significantly more severe AF pattern (p=0.04) than patients without LVZ, and little difference existed with regard to other clinical variables. Patients with LVZ presented significantly more total EAT volume (162.4±71.3 mL vs 135.5±57.2 mL; p=0.03) and LA-EAT volume (26.4±15.9 mL vs 20.9±10.5 mL; p<0.01) than no-LVZ patients. Multivariable logistic regression analyses revealed total EAT volume index to be an independent predictor of the presence of LVZ (odds ratio [OR] 1.01; 95% confidence interval [CI] 1.01-1.04; p<0.01) and LA-EAT percentage to be an independent predictor of severe LVZ (OR 1.34; 95% CI 1.18-1.64; p<0.001). The EAT volume and its distribution around the LA may indicate the presence and severity of LVZ. The assessment of the volume of EAT and its distribution may lead to better risk stratification in patients with AF.

Coronary sinus electrogram characteristics predict termination of AF with ablation and long-term clinical outcome.

Markers predicting atrial fibrillation (AF) termination and freedom from AF/atrial tachycardia (AT) has been proposed. This study aimed to evaluate the role of novel coronary sinus (CS) electrogram characteristics in predicting the acute ablation response and freedom from AF/AT during follow-up. Patients undergoing ablation for persistent AF as part of the Stochastic Trajectory Analysis of Ranked signals mapping study were included. Novel CS electrogram characteristics including CS cycle length variability (CLV) and CS activation pattern stability (APS) and proportion of low voltage zones (LVZs) were reviewed as potential predictors for AF termination on ablation and freedom from AF/AT during follow-up. The relationship between localized driver characteristics and CS electrogram characteristics was also assessed. Sixty-five patients were included. AF termination was achieved in 51 patients and 80% of patients were free from AF/AT during a follow-up of 29.5 ± 3.7 months. CS CLV of <30 ms, CS APS of ≥30% and proportion of LVZ < 30% showed high diagnostic accuracy in predicting AF termination on ablation and freedom from AF/AT during follow-up (CS CLV odds ratio [OR] 25.6, area under the curve [AUC] 0.91; CS APS OR 15.9, AUC 0.94; proportion of LVZs OR 21.4, AUC 0.88). These markers were independent predictors of AF termination on ablation and AF/AT recurrence during follow-up. Ablation of a smaller number of drivers that demonstrate greater dominance strongly correlate with greater CS organization. Novel CS electrogram characteristics were independent predictors of AF termination and AF/AT recurrence during follow-up. These markers can potentially aid in predicting outcomes and guide ablation and follow-up strategies.

Left atrial epicardial adipose tissue is associated with low voltage zones in the left atrium in patients with non-valvular atrial fibrillation.

ObjectiveEpicardial adipose tissue (EAT) is related to atrial fibrillation (AF), but the specific mechanism is still unclear. Left atrial (LA) low voltage zones (LVZ) can well reflect atrial fibrosis. This study investigated the relationship between EAT and LVZ in non-valvular AF (NVAF) patients.MethodsThis observational study including patients with NVAF (n = 214) undergoing radiofrequency ablation (RFCA) for the first time in our hospital and 62 matched controls. The EAT volume and attenuation were measured by contrast-enhanced computed tomography. A three-dimensional mapping system was used to map the left atrial endocardium and evaluate LA-LVZ. Patients were divided into LVZ and non-LVZ groups according to the presence or absence of LVZ.ResultsPatients with AF showed higher LA-EAT volume and lower attenuation value than controls (29.7 ± 11.2 cm3 vs. 20.9 ± 8.6 cm3, P = 0.021; −91.2 ± 5.6 HU vs. −88.7 ± 5.9 HU, P < 0.001). Compared with the group without LVZ, there were significant differences in age [65 (59–71) vs. 60 (52–69), P = 0.006], LAVI [75.1 ± 20.7 ml/m2 vs. 67.2 ± 20.9 ml/m2, P = 0.018], LA-EAT volume (34.8 ± 11.5 cm3 vs. 28.1 ± 10.6 cm3, P < 0.001) and LA-EAT attenuation (−93.9 ± 5.3 HU vs. −90.4 ± 5.5 HU, P < 0.001). Multivariate regression analysis showed that age (OR = 1.040; 95%CI: 1.001–1.078, P = 0.042), LAVI (OR = 1.019; 95%CI: 1.002–1.037, P = 0.032), LA-EAT volume (OR = 1.193; 95%CI: 1.015–1.402, P = 0.034) and attenuation value (OR = 0.801; 95%CI: 0.701–0.916 P = 0.001) were independent predictors of LVZ. After LA-EAT attenuation was incorporated into the clinical model, the comprehensive discrimination and net reclassification tended to improve (IDI and NRI > 0, P < 0.05).ConclusionLA-EAT volume and attenuation values can independently predict the presence of LVZ, and LA-EAT attenuation has a better predictive value than LA-EAT volume.