High-density Electroanatomical Mapping Research Articles

Understanding electrical pulmonary vein antrum for paroxysmal atrial fibrillation: Further look into super high-density electroanatomic mapping of the left atrium

Isolation line placed at the pulmonary vein antrum (PVA) area is superior to ostium level in atrial fibrillation (AF) control. However, less is known about the electrophysiological characteristics of PVA. To describe the electrophysiological properties of PVA. High-density mapping of the left atrium was performed in 18 paroxysmal AF (PAF) patients and 9 age- and sex-matched paroxysmal supraventricular tachycardia (PSVT) patients. Each PVA was divided into 8, pulmonary vein (PV) into 4 segments. The electrophysiological properties included slow conduction, complex fractionated electrograms, and effective refractory period (ERP). The slow conduction was more prevalent at PVA (43.2±19.5 vs. 14.7±13.0 %, P=0.001) and PV (61.9±16.4 vs. 9.1±9.0 %, P<0.001) in PAF patients than in PSVT patients during sinus rhythm (SR). Similarly, the area with complex fractionated electrograms was significantly larger at PVA (133.8 [61.6, 233.2] vs. 0.0 [0.0, 41.4] mm2, P=0.011) in PAF patients during SR. The ERP of PVA was longer in PAF patients than in control at the drive length of 600 ms (260 [230, 280] vs. 220 [190, 250] ms, P=0.001) and 400 ms (230 [205, 250] vs. 200 [190, 220] ms, P=0.007). The ERP net difference between the PV and PVA is larger in PAF patients than in control both at 600 ms (40 [20, 70] vs. 10 [10, 30] ms, P<0.001) and (40 [20, 60] vs. 20 [10, 30] ms, P<0.001) at 400 ms pacing, respectively. PAF patients have the PVA electrical substrate including slow conduction, complex fractionated electrograms and ERP dispersion.

Atrial Fibrillation Substrate and Catheter Ablation Outcomes in MYBPC3- and MYH7-Mediated Hypertrophic Cardiomyopathy

BackgroundThe effects of disease-causing MYBPC3 or MYH7 genetic variants on atrial myopathy, atrial fibrillation (AF) clinical course, and catheter ablation efficacy remain unclear. ObjectivesThe aim of this study was to characterize the atrial substrate of patients with MYBPC3- or MYH7-mediated hypertrophic cardiomyopathy (HCM) and its impact on catheter ablation outcomes. MethodsA retrospective single-center study of patients with HCM who underwent genetic testing and catheter ablation for AF was performed. Patients with MYBPC3- or MYH7-mediated HCM formed the gene-positive cohort; those without disease-causative genetic variants formed the control cohort. High-density electroanatomical mapping was performed using a 3-dimensional mapping system, followed by radiofrequency ablation. ResultsTwelve patients were included in the gene-positive cohort (mean age 55.6 ± 9.9 years, 83% men, 50% MYBPC3, 50% MYH7, mean ejection fraction 59.3% ± 13.7%, mean left atrial [LA] volume index 51.7 ± 13.1 mL/m2, mean LA pressure 20.2 ± 5.4 mm Hg) and 15 patients in the control arm (mean age 61.5 ± 12.6 years, 60% men, mean ejection fraction 64.9% ± 5.1%, mean LA volume index 54.1 ± 12.8 mL/m2, mean LA pressure 19.6 ± 5.41 mm Hg). Electroanatomical mapping demonstrated normal voltage in 87.7% ± 5.03% of the LA in the gene-positive cohort and 94.3% ± 3.58% of the LA in the control cohort (P < 0.001). Of the abnormal regions, intermediate scar (0.1-0.5 mV) accounted for 6.33% ± 1.97% in the gene-positive cohort and 3.07% ± 2.46% in the control cohort (P < 0.01). Dense scar (<0.1 mV) accounted for 5.93% ± 3.20% in the gene-positive cohort and 2.61% ± 2.19% in the control cohort (P < 0.01). Freedom from AF at 12 months was similar between the gene-positive (75%) and control (73%) cohorts (P = 0.92), though a greater number of procedures were required in the gene-positive cohort. ConclusionsPatients with MYBPC3- or MYH7-mediated HCM undergoing AF ablation have appreciably more low-amplitude LA signals, suggestive of fibrosis. However, catheter ablation remains an effective rhythm-control strategy.

The evaluation of the efficacy of automated peak frequency annotation algorithm for the identification of critical isthmus of ventricular tachycardia and deceleration zones

Abstract Background Substrate modification techniques have widely been adopted due to hemodynamic instability and non-inducibility of clinical ventricular tachycardia (VT). Accurate annotation of local near field EGMs is paramount to better evaluate the ventricular substrate. Furthermore, annotation of late potentials (LP) necessitates substantial manual input and isochronal late activation mapping (ILAM) involves constant sensitivity adjustments, potentially affecting the accuracy of local ventricular signal representation. Objective This study aims to assess the utility of novel automated peak frequency (PF), which aims to determine near field local activity in low voltage regions in the prediction of the CI of scar related reentrant VTs. Furthermore, the effectiveness of automated PF annotation of near field EGMs to identify deceleration zone (DZ) during ILAM was also evaluated. Methods A total of 18 patients with scar-related VT were analyzed. In all patients, VT isthmuses were identified based on activation maps and acute termination achieved during radiofrequency ablation. Automated PF annotation using Ensite X system (Abbott) was retrospectively performed in all cases specifically in areas of low voltage with fractioned signals. The accuracy of applying the PF value and automated ILAM map for detecting VT isthmus was also assessed. Results Among the study group, 12 (66.7%) had ischemic cardiomyopathy, while 6 (33.3%) had nonischemic cardiomyopathy [3 (16.7%) with arrhythmogenic right ventricular cardiomyopathy, 2 (11.1%) with idiopathic dilated cardiomyopathy, and 1 (5.6%) with hypertrophic cardiomyopathy]. All identified isthmuses were located in areas exhibiting bipolar voltage below 0.5 mV and a PF of 250 Hz with fractionated EGMs Automated NF DZ annotation predicted the VT isthmus in 16/18 (88.9%) of the cases similar to the conventional ILAM with manual adjustment (88.9%). Conclusion Using high-density electroanatomical mapping with near field algorithm, a PF cutoff of 250 Hz accurately identified the low voltage regions to predict the CI of VT. In addition, automated annotation of EGMs during ILAM similarly identified the DZs compared with conventional last deflection algorithm with manual adjustments, which were colocalized with CI of VTs.

Endocardial repolarization dispersion in BrS: A novel automatic algorithm for mapping activation recovery interval.

Repolarization dispersion in the right ventricular outflow tract (RVOT) contributes to the type-1 electrocardiographic (ECG) phenotype of Brugada syndrome (BrS), while data on the significance and feasibility of mapping repolarization dispersion in BrS patients are scarce. Moreover, the role of endocardial repolarization dispersion in BrS is poorly investigated. We aimed to assess endocardial repolarization patterns through an automated calculation of activation recovery interval (ARI) estimated on unipolar electrograms (UEGs) in spontaneous type-1 BrS patients and controls; we also investigated the relation between ARI and right ventricle activation time (RVAT), and T-wave peak-to-end interval (Tpe) in BrS patients. Patients underwent endocardial high-density electroanatomical mapping (HDEAM); BrS showing an overt type-1 ECG were defined asOType1, while those without (latent type-1 ECGandLType1) received ajmaline infusion. BrS patients only underwent programmed ventricular stimulation (PVS). Data were elaborated to obtain ARI corrected with the Bazett formula (ARIc), while RVAT was derived from activation maps. 39 BrS subjects (24 OType1 and 15 LTtype1) and 4 controls were enrolled. OType1 and post-ajmaline LType1 showed longer mean ARIc than controls (306 ± 27.3 ms and 333.3 ± 16.3 ms vs. 281.7 ± 10.3 ms, p = .05 and p < .001, respectively). Ajmaline induced a significant prolongation of ARIc compared to pre-ajmaline LTtype1 (333.3 ± 16.3 vs. 303.4 ± 20.7 ms, p < .001) and OType1 (306 ± 27.3 ms, p < .001). In patients with type-1 ECG (OTtype1 and post-ajmaline LType1) ARIc correlated with RVAT (r = .34, p = .04) and Tpec (r = .60, p < .001), especially in OType1 subjects (r = .55, p = .008 and r = .65 p < .001, respectively). ARIc mapping demonstrates increased endocardial repolarization dispersion in RVOT in BrS. Endocardial ARIc positively correlates with RVAT and Tpec, especially in OType1.

Redefining left bundle branch block from high-density electroanatomical mapping

BackgroundThe existing ECG criteria for diagnosing left bundle branch block (LBBB) are insufficient to distinguish between true and false blocks accurately. MethodsWe hypothesized that the notch width of the QRS complex in the lateral leads (I, avL, V5, V6) on the LBBB-like ECG could further confirm the diagnosis of true complete left bundle branch block (t-LBBB). We conducted high-density, three-dimensional electroanatomical mapping in the cardiac chambers of 37 patients scheduled to undergo CRT. These patients' preoperative electrocardiograms met the ACC/AHA/HRS guidelines for the diagnosis of complete LBBB. If the left bundle branch potential could be mapped from the base of the heart to the apex on the left ventricular septum, it was defined as a false complete left bundle branch block (f-LBBB). Otherwise, it was categorized as a t-LBBB. We conducted a comparative analysis between the two groups, considering the clinical characteristics, real-time correspondence between the spread of ventricular electrical excitation and the QRS wave, QRS notch width of the lateral leads (I, avL, V5, V6), and the notch width/left ventricular end-diastolic diameter (Nw/LVd) ratio. We performed the ROC correlation analysis of Nw/LVd and t-LBBB to determine the sensitivity and specificity for diagnostic authenticity. ResultsTwenty-five patients were included in the t-LBBB group, while 12 patients were assigned to the f-LBBB group. Within the t-LBBB group, the first peak of the QRS notch correlated with the depolarization of the right ventricle and septum, the trough corresponded to the depolarization of the left ventricle across the left ventricle, and the second peak aligned with the depolarization of the left ventricular free wall. In contrast, within the f-LBBB group, the first peak coincided with the depolarization of the right ventricle and a majority of the left ventricle, the second peak occurred due to the depolarization of the latest, locally-activated myocardium in the left ventricle, and the trough was a result of delayed activation of the left ventricle that did not align with the usual peak timing. The QRS notch width (45.2 ± 12.3 ms vs. 52.5 ± 9.2 ms, P < 0.05) and the Nw/LVd ratio (0.65 ± 0.19 ms/mm vs. 0.81 ± 0.17 ms/mm, P < 0.05) were compared between the two groups. After conducting the ROC correlation analysis, a sensitivity of 56% and a specificity of 91.7% for diagnosing t-LBBB using Nw/LVd were obtained. ConclusionBy utilizing the current diagnostic criteria for LBBB, an increased Nw/LVd value can enhance the effectiveness of diagnosing LBBB.

Cardiac radiotherapy transiently alters left ventricular electrical properties and induces cardiomyocyte-specific ventricular substrate changes in heart failure.

Ongoing clinical trials investigate the therapeutic value of stereotactic cardiac radioablation (cRA) in heart failure patients with ventricular tachycardia. Animal data indicate an effect on local cardiac conduction properties. However, the exact mechanism of cRA in patients remains elusive. Aim of the current study was to investigate in vivo and in vitro myocardial properties in heart failure and ventricular tachycardia upon cRA. High-density 3D electroanatomic mapping in sinus rhythm was performed in a patient with a left ventricular assist device and repeated ventricular tachycardia episodes upon several catheter-based endocardial radio-frequency ablation attempts. Subsequent to electroanatomic mapping and cRA of the left ventricular septum, two additional high-density electroanatomic maps were obtained at 2- and 4-month post-cRA. Myocardial tissue samples were collected from the left ventricular septum during 4-month post-cRA from the irradiated and borderzone regions. In addition, we performed molecular biology and mitochondrial density measurements of tissue and isolated cardiomyocytes. Local voltage was altered in the irradiated region of the left ventricular septum during follow-up. No change of local voltage was observed in the control (i.e. borderzone) region upon irradiation. Interestingly, local activation time was significantly shortened upon irradiation (2-month post-cRA), a process that was reversible (4-month post-cRA). Molecular biology unveiled an increased expression of voltage-dependent sodium channels in the irradiated region as compared with the borderzone, while Connexin43 and transforming growth factor beta were unchanged (4-month post-cRA). Moreover, mitochondrial density was decreased in the irradiated region as compared with the borderzone. Our study supports the notion of transiently altered cardiac conduction potentially related to structural and functional cellular changes as an underlying mechanism of cRA in patients with ventricular tachycardia.

Predictors of Low Voltage Zone and Sex Differences in Low Voltage Zone Distribution in Patients with Atrial Fibrillation.

Previous studies have revealed the left atrial (LA) low voltage zone (LVZ) are tightly linked to the recurrence of atrial fibrillation (AF). Furthermore ablation that targets the LA LVZ can improve patient prognosis. The aim of this study was to identify potential clinical predictors of the LA LVZ, to investigate possible sex differences in the distribution of LA LVZ, and to examine the relationship between LA LVZ and AF recurrence. A total of 108 patients who underwent AF catheter ablation and LA high-density electro-anatomic mapping were enrolled in the study. Of these, 56 patients with LA LVZ 5% were assigned to the LVZ group, while the remaining 52 patients with LA LVZ 5% were assigned to the non-LVZ group. Clinical characteristics and laboratory results for all patients were collected and compared between the two groups. Multivariate logistic regression analysis revealed that persistent AF (odds ratio [OR] = 4.563, 95% confidence interval [CI]: 1.194-17.431, p = 0.026), left atrial volume (LAV, OR = 1.030, 95% CI: 1.001-1.061, p = 0.044) and brain natriuretic peptide (BNP, OR = 1.010, 95% CI: 1.002-1.019, p = 0.015) were independent predictors for the presence of LA LVZ. In addition, female sex (OR = 7.161, 95% CI: 1.518-33.792, p = 0.013), LAV (OR = 1.028, 95% CI: 1.002-1.055, p = 0.035) and BNP (OR = 1.009, 95% CI: 1.001-1.016, p = 0.018) were independent predictors of severe LA LVZ (LA LVZ 20%). The extent of LVZ was significantly greater in females than in males (32.8% 15.5% vs. 23.5% 12.7%, p = 0.021), especially in the anterior (34.5% 16.7% vs. 20.0% 16.4%, p = 0.003) and septal (44.9% 17.1% vs. 29.0% 18.9%, p = 0.004) walls. During follow-up, AF recurrence was significantly higher in patients with LA LVZ than in those without LA LVZ (31.3% vs. 12.8%, respectively, p = 0.023). In this study cohort, persistent AF, LAV and BNP were independent predictors of LA LVZ. Furthermore, female sex, LAV and BNP were independent predictors of severe LA LVZ. Females had a significantly greater extent of LVZ than males, especially in the anterior and septal walls. Patients with LA LVZ had a higher risk of recurrent AF.

Results of atypical flutter ablation in the era of high density electroanatomical mapping (the RAFAELA study)

Abstract Introduction Atypical flutter (AFL) ablation is a technically challenging procedure with limited long-term efficacy according to prior studies and not exempt from risks. Purpose The aim of this study was to describe the efficacy, in terms of acute and long-term rhythm management, and safety of AFL ablation guided by high-density electroanatomical mapping in a population of contemporary patients. We aimed also to compare results between different patient populations. Methods From june 2015 to November 2021, all consecutive AFL ablation procedures guided by high-density electroanatomical mapping were included in the study. Patients were classified in 4 groups according to history of atrial catheter ablation, cardiac surgery, congenital heart disease or none of the above (considered as primary disease). Activation and voltage mapping were used to define AFL circuits and substrate. After AFL characterization, radiofrequency lesions were performed to operator’s discretion until AFL termination. Programmed atrial stimulation was repeated to test AFL inducibility, and any sustained induced atrial arrhythmia was ablated. Procedural success was defined as termination of every induced AFL and no-inducibility. A 3-month blanking period was considered. Follow-up included visits with ECG and/or 24h Holter-ECG at 3, 6, 12, 24 months, and from there on according to physician’s discretion. Results 190 AFL procedures in 160 patients were included. Patient and procedural characteristics of the global cohort as well as different patient populations (27% primary, 37.9% post-ablation, 15.3% post-surgery, 20% congenital heart disease (CHD)) can be found in figure 1 (table). Survival free from atrial arrhythmias in pre-specified groups is shown in figure 2 (left). Overall, a 2-year ∼50% recurrence rate was observed, with a tendency to better outcome in patients with congenital heart disease (∼70%), over the rest of the groups, which behaved similarly (p=0.281). Progression to permanent atrial arrhythmia was lower in this subgroup (2.7% vs 23.5%, p=0.028), as shown in figure 2 (right), probably related to higher rhythm control efforts and stricter follow-ups. CONCLUSIONS In the era of high-density electroanatomical mapping, acute procedural success is achievable in the majority of patients, but recurrence rate remains high, with an approximate 50% 2-year recurrence rate except for congenital heart disease patients, which tend to show better survival free from atrial arrhythmias.Figure 1Figure 2

The electrophysiological substrate of biopsy-proven cardiac amyloidosis

Abstract Background Cardiac amyloidoses (CA) are an increasingly recognized group of infiltrative cardiomyopathies associated with high risk of major adverse cardiac events. Endomyocardial biopsy (EMB) may be required to differentiate the amyloid type (mainly, Immunoglobulin light chain [AL] versus transthyretin-related [ATTR]) in some cases. Purpose The aim of this study was to provide the first description of the right ventricular (RV) electroanatomical substrate of CA, and assess its association with EMB findings and clinical outcomes. Methods We enrolled ten consecutive patients undergoing EMB for suspected CA (median age, 68[63-77]; male, 50%) in a monocentric, observational, retrospective study. All patients had a clinical diagnosis of CA, but a diagnosis of CA type was hampered by the presence of inconclusive or discordant laboratory-imaging findings (abnormal serum free light chain assay and positive bone scintigraphy, n=5; ambiguous imaging results, n=4; abnormal serum free light chain assay and TTR gene mutation, n=1). Therefore, each patient underwent RV high-density electroanatomical voltage mapping (EVM) and EMB. The primary outcome was death or hospitalization at 1-year follow-up. We recorded electrogram features at EMB sampling sites and in the overall RV, and explored their correlations with histopathological findings and primary outcomes events. Results A final EMB-proven diagnosis of AL or ATTR CA was formulated in 6 and 4 patients, respectively. Electrogram amplitudes in the bipolar and unipolar configurations averaged 1.58±0.65 mV, and 5.38±1.41 in the overall RV. We found a significant inverse correlation between unipolar electrogram amplitude and amyloid burden at EMB (p&amp;lt;0.001); the unipolar voltage cutoff that best identified regions with &amp;gt;15% amyloid tissue infiltration according to Youden index was 9.1 mV (sensitivity, 43%; specificity, 100%; accuracy, 77%). At 1-year follow-up, 6 patients (60%) experienced a primary outcome event. Compared to subjects with uneventful follow-up, patients with a primary outcome event had larger unipolar low-voltage zones (32.3 [6.1] cm2 vs. 20.7 [6.5] cm2, p=0.043) and bipolar dense scar areas (6.1 [2.3] cm2 vs. 1.8 [0.7] cm2, p=0.005), and after pooling mapping points from all patients, unipolar electrogram amplitude was moderately associated with primary outcome events (AUC: 0.65 [95% CI, 0.64-0.65]). Conclusions In CA, electrogram amplitudes are around the lower limit of normal, yet disproportionately low compared to the increased wall thickness. We found evidence that unipolar electrogram amplitude may be a quantitative marker of amyloid burden, possibly associated with adverse clinical outcomes.EVM and EMB in ATTR cardiac amyloidosisEVM and EMB in AL cardiac amyloidosis

Invasively diagnosed HFpEF in AF associated with functional remodelling of the left atrial appendage: implications for stroke risk

Abstract Background HFpEF commonly coexists with atrial fibrillation (AF). The influence of coexisting HFpEF on function of the left atrial appendage (LAA) and risk of stroke remains unknown. Objective To use invasive hemodynamic assessment and multi-modality imaging to evaluate the influence of underlying HFpEF on LAA function in patients with symptomatic AF. Methods Patients with AF and preserved ejection fraction undergoing AF ablation were prospectively recruited. All participants underwent invasive diagnosis of HFpEF using established hemodynamic criteria. Participants were classified as ‘HFpEF’ when mean left atrial pressure (mLAP) was &amp;gt;15mmHg and ‘early HFpEF’ when mLAP rose to above 15mmHG after infusion of 500mls saline. For LAA assessment, participants underwent 1) contrast-enhanced cardiac CT to evaluate LAA volume, 2) transesophageal echocardiography to investigate emptying velocities (LAAEV), filling velocities (LAAFV) and LAA ejection fraction (LAAEF) and 3) high-density electroanatomic mapping to assess LAA bipolar voltages. Results Of 115 participants recruited, 55 had ‘HFpEF’, whilst 29 had ‘early HFpEF’ and 31 had ‘no HFpEF’. Table 1 demonstrates the baseline characteristics and LAA structural and functional parameters across the three groups. The HFpEF group was characterized by higher BMI (p=0.008) and higher prevalence of hypertension (p=0.023) but there was no significant difference in age (p=0.194) or gender (p=0.376). LAA volume was not significantly different across the three groups (p=0.509). However, the HFpEF group demonstrated reduced LAAEV (p=0.021) and LAAFV (p=0.015) compared to early HFpEF and no HFpEF. HFpEF was also associated with reduced LAAEF (p=0.015) and reduced LAA bipolar voltages in sinus rhythm (p=0.028) compared to no HFpEF. In a multivariable analysis HFpEF group was the only independent predictor of reduced LAAEV (p=0.015). Conclusions Invasively diagnosed HFpEF in AF is common and associated with significantly reduced LAA function. The coexistence of HFpEF may therefore be a determinant of future stroke risk in patients with AF.

Optimizing fibrosis detection: a comparison of electroanatomical mapping and late enhancement gadolinium magnetic resonance imaging.

Fibrotic atrial cardiomyopathy plays an important role in determining the outcome of ablation in patients with atrial fibrillation (AF). Two main methods are being used for the evaluation of fibrosis: voltage-based high-density (HD) electroanatomical mapping (EAM) and late gadolinium enhancement MRI (LGE-MRI). The comparability between both methods in detecting fibrosis has not been systematically investigated. LGE-MRIs of the left atrium (LA) were performed in 21 patients. LA-fibrosis was evaluated using a custom-designed software generating a 3D-model of the LA. HD-electroanatomical maps were recorded in each patient. After processing the maps and the MRI models by excluding the mitral valve, pulmonary veins, and the left atrial appendage, the LGE areas were measured and compared to the low voltage areas (LVA) in the HD maps using three different cutoff values of 0.5 mV, 0.7 mV, and 1.0 mV. The analysis revealed significant differences between EAM and LGE-MRI in assessing LA-fibrosis at 0.5-mV (for anterior and posterior walls) and 1.0-mV cutoffs (for anterior and posterior wall and septum). However, no significant differences were found between EAM and LGE-MRI when using a 0.7-mV cutoff for all the investigated areas. A voltage cutoff of 0.7 mV provided the best correlation between EAM and LGE MRI for detecting left atrial fibrosis. It supports the idea that a 0.5-mV cutoff may underestimate fibrosis, as areas with local signal voltages between 0.6 and 0.8 mV could also show LGE on MRI. Further research is needed to determine the ideal voltage cutoff for detecting left atrial fibrosis.

Wide Antral Circumferential Re-Ablation for Recurrent Atrial Fibrillation after Prior Pulmonary Vein Isolation Guided by High-Density Mapping Increases Freedom from Atrial Arrhythmias.

Performing repeated pulmonary vein isolation (re-PVI) after recurrent atrial fibrillation (AF) following prior PVI is a standard procedure. However, no consensus exists regarding the most effective approach in redo procedures. We assessed the efficacy of re-PVI using wide antral circumferential re-ablation (WACA) supported by high-density electroanatomical mapping (HDM) as compared to conventional re-PVI. Consecutive patients with AF recurrences showing true PV reconnection (residual intra-PV and PV antral electrical potentials within the initial ablation line) or exclusive PV antral potentials (without intra-PV potentials) in the redo procedure were prospectively enrolled and received HDM-guided WACA (Re-WACA group). Conventional re-PVI patients treated using pure ostial gap ablation guided by a circular mapping catheter served as a historical control (Re-PVI group). Patients with durable PVI and no antral PV potentials were excluded. Arrhythmia recurrences ≥30 s were calculated as recurrences. In total, 114 patients were investigated (Re-WACA: n = 56, 68 ± 10 years, Re-PVI: n = 58, 65 ± 10 years). There were no significant differences in clinical characteristics including the AF type or the number of previous PVIs. In the Re-WACA group, 11% of patients showed electrical potentials only in the antrum but not inside any PV. At 402 ± 71 days of follow-up, the estimated freedom from arrhythmia was 89% in the Re-WACA group and 69% in the Re-PVI group (p = 0.01). Re-WACA independently predicted arrhythmia-free survival (HR = 0.39, 95% CI 0.16-0.93, p = 0.03), whereas two previous PVI procedures predicted recurrences (HR = 2.35, 95% CI 1.20-4.46, p = 0.01). The Re-WACA strategy guided by HDM significantly improved arrhythmia-free survival as compared to conventional ostial re-PVI. Residual PV antral potentials after prior PVI are frequent and can be easily visualized by HDM.

Electroanatomical features of biopsy-proven cardiac amyloidosis

Abstract Funding Acknowledgements Type of funding sources: None. Background Cardiac amyloidoses (CA) are an increasingly recognized group of infiltrative cardiomyopathies associated with high risk of heart failure, thromboembolic events, arrhythmias, and sudden death. Endomyocardial biopsy may be required to differentiate the amyloid type (mainly, Immunoglobulin light chain [AL] versus transthyretin-related [ATTR]) in some cases. Purpose to provide a first description of electroanatomical characteristics of amyloid cardiomyopathy, and relate them to endomyocardial biopsy findings. Methods we enrolled ten consecutive patients (median age, 68 [63-77]; male, 50%) in an observational, retrospective study. All of them had a clinical diagnosis of CA, but a diagnosis of CA type was hampered by the presence of inconclusive or discordant laboratory-imaging findings (abnormal serum free light chain assay and positive bone scintigraphy, n=5; ambiguous imaging results, n=4; abnormal serum free light chain assay and TTR gene mutation, n=1). Therefore, all patients underwent right ventricular high-density electroanatomical mapping (EAM) using a multipolar catheter (Advisor HD Grid, Abbott), and EAM-guided endomyocardial biopsy (EMB). We recorded electrogram features at EMB sampling site, and explored their correlation with histological findings with mixed effect models. Results The clinical, electroanatomical, and histological features of enrolled patients according to the EMB-proven type of CA (AL, n=6; ATTR, n=4) are resumed in Table. Electrogram amplitudes in both the bipolar and the unipolar configuration were generally normal both in the overall right ventricle, and at EMB sites. We found a significant correlation between both unipolar and bipolar electrogram amplitude and the percentage of both amyloid tissue (p&amp;lt;0.01 and p=0.016, respectively) and fibrous tissue (both p&amp;lt;0.01) at EMB (Figure). We observed the strongest linear association (i.e., highest R2) between unipolar electrogram amplitude and amyloid tissue, as well as between bipolar electrogram amplitude and fibrous tissue. On the other hand, electrogram duration and the number of electrogram peaks were unrelated to histological findings. The unipolar voltage cutoff that best identified regions with &amp;gt;15% amyloid tissue infiltration according to Youden index was 9.1 mV (sensitivity, 43%; specificity, 100%; accuracy, 77%). Conclusion CA is associated with normal electrogram amplitudes using ahigh density mapping catheter and conventional voltage cutoffs. Nevertheless, unipolar electrogram amplitude is strongly related to the extent of amyloid infiltration, and unipolar voltage&amp;lt;9.1 mV is 100% specific for &amp;gt;15% amyloid tissue deposition.

PO-02-195 ADJUNCTIVE VEIN OF MARSHALL ETHANOL ABLATION FOR ATRIAL FIBRILLATION: SINGLE CENTER EXPERIENCE AND PROCEDURAL LEARNING CURVE

Retrograde ethanol infusion into the vein of Marshall (EI-VOM) has been demonstrated to be an effective adjunct to pulmonary vein isolation (PVI) for ablation of atrial fibrillation (AF). This study sought to assess the temporal change in procedural volume and associated success rate of VOM ethanol ablation. All patients undergoing PVI with EI-VOM at The Ohio State University Wexner Medical Center from January 2021 to November 2022 were included. Procedural success was defined as successful retrograde infusion of ethanol into the vein of Marshall followed the development of a characteristic distribution of low voltage scar in a semicircular pattern around the left inferior pulmonary vein on high-density electroanatomical mapping. The scar was adjudicated by two blinded high-volume operators. The primary endpoint was procedural success over 6-month intervals. Statistical significance was assessed via Fisher's exact test. 201 patients underwent attempted EI-VOM. Patient characteristics were notable for age 65.2 ± 9.0 years, 56 (28%) females, body mass index 33.1 ± 7.3 kg/m2, left ventricular ejection fraction 52.3 ± 11.3%, and CHA2DS2-VASc 2.9 ± 1.5. 113 (56%) patients had non-paroxysmal AF. 173 (86%) patients had failed antiarrhythmic drugs, 113 (56%) patients had a prior cardioversion, and 105 (52%) patients had a prior catheter ablation for AF. Over 23 months, procedural volume increased from an average of 2 cases/month to 12 cases/month, and the procedural success rate increased from 33% to 68% (p=0.020). Figure 1 demonstrates the case volume and procedural learning curve over time. Notable complications included 1 (0.5%) case of cardiac tamponade requiring pericardiocentesis. VOM ethanol ablation is associated with a significant learning curve, and procedural success rate significantly improves with increased case volume.

PO-01-189 IMPACT OF CORONARY SINUS BALLOON UTILIZATION ON IDENTIFICATION OF THE VEIN OF MARSHALL FOR ADJUNCTIVE ETHANOL ABLATION FOR ATRIAL FIBRILLATION

Retrograde ethanol infusion into the vein of Marshall (EI-VOM) as an adjunct to pulmonary vein isolation (PVI) has been reported to improve success of atrial fibrillation (AF) ablation. However, identification and cannulation of the VOM remains technically challenging. It has been proposed that balloon occlusion of the coronary sinus (CS) allows for improved contrast opacification and facilitates identification of the VOM as well as differentiation of other branching veins. This study sought to assess the impact of CS balloon use on the success rate of VOM identification and time to VOM identification during adjunctive VOM ethanol ablation for AF. All patients undergoing PVI with EI-VOM at The Ohio State University Wexner Medical Center from January 2021 to November 2022 with known use or non-use of CS balloon were included. The primary endpoint was success rate of VOM identification and time to identification of VOM. The secondary endpoints were fluoroscopy time, procedure time, successful VOM cannulation, successful scar formation as defined by development of a characteristic low voltage area around the left inferior pulmonary vein on high-density electroanatomical mapping after ethanol infusion, and procedural complications. 106 patients underwent VOM ethanol ablation, 36 (34%) with and 68 (66%) without CS balloon use respectively. There was a significantly increased success rate in identification of VOM with CS balloon use (balloon 32 (89%) vs no balloon 50 (71%) patients, p=0.042). There was no significant difference in time to VOM identification. Notably, overall procedure time was significantly longer with CS balloon use (balloon 210.4 ± 51.7 vs no balloon 181.4 ± 37.1 minutes, p=0.004). There was no significant difference with balloon use in terms of fluoroscopy time, successful VOM cannulation, or successful scar formation (Table I). Notably, there were 3 (4%) cases of CS or VOM dissection in patients without balloon use as compared to 0 (0%) cases with balloon use, but this difference did not meet statistical significance. Figure 1 demonstrates the use of CS balloon during EI-VOM to facilitate identification of the VOM as well as atrial branches. CS balloon use is associated with significantly improved success in identification of the VOM during adjunctive ethanol ablation for AF. However, this is balanced by an associated increased procedure time.Tabled 1Table I: Procedural characteristicsProcedural characteristicsCoronary Sinus Balloon Used (N=36)Coronary Sinus Balloon Not Used (N=70)Total (N=106)P valueTimingTime to VOM identification, mins43.2 ± 15.546.1 ± 14.445.1 ± 14.80.419Fluoroscopy time, mins33.4 ± 10.031.4 ± 11.532.1 ± 11.00.374Procedure time, mins210.4 ± 51.7181.4 ± 37.1191.3 ± 44.60.004Key Procedural StepsCS cannulated36 (100%)68 (97%)104 (98%)0.547VOM identified32 (89%)50 (71%)82 (77%)0.042VOM cannulated29 (81%)46 (66%)75 (71%)0.112Able to advance balloon to VOM29 (81%)46 (66%)75 (71%)0.112Ethanol infused into VOM29 (81%)46 (66%)75 (71%)0.112OutcomeSuccessful formation of characteristic scar / low voltage area on high-density EAM15 (42%)35 (50%)50 (47%)0.853ComplicationsCS or VOM dissection0 (0%)3 (4%)3 (3%)0.549Values presented as mean ± 1 standard deviation for continuous variables and n (%) for categorical variables. Abbreviations: CS = coronary sinus, EAM = electroanatomical map, VOM = Vein of Marshall. Open table in a new tab

PO-02-213 ELECTROANATOMICAL ASPECTS OF BIOPSY-PROVEN CARDIAC AMYLOIDOSIS

Cardiac amyloidoses (CA) are a common and increasingly recognized group of infiltrative cardiomyopathies associated with high risk of heart failure, thromboembolic events, arrhythmias, and sudden death. Endomyocardial biopsy may be required to differentiate the amyloid type (mainly, Immunoglobulin light chain [AL] versus transthyretin-related [ATTR]) in selected cases. To describe electroanatomical characteristics of amyloid cardiomyopathy, and relate them to endomyocardial biopsy findings. We included ten consecutive patients (median age, 68 [63-77]; male, 50%) in an observational, retrospective study. All of them had a clinical diagnosis of CA, but a diagnosis of CA type was uncertain based on non-invasive findings. Therefore, all patients underwent right ventricular high-density electroanatomical mapping (EAM) using a multipolar catheter (Advisor HD Grid, Abbott), and EAM-guided endomyocardial biopsy (EMB). We recorded electrogram features at EMB sampling site, and assessed their correlation with histological findings with mixed effect models. The clinical, electroanatomical, and histological features of enrolled patients according to the EMB-proven type of CA (AL, n=6; ATTR, n=4) are resumed in Table. Electrogram amplitudes in both the bipolar and the unipolar configurations were largely preserved in the overall right ventricle, and at EMB sites. There were highly significant correlations among electrogram amplitudes in both the unipolar and bipolar configurations, and the extent of amyloid and fibrous tissue substitution at EMB (all p<0.01, Figure). We observed the strongest linear associations (i.e., highest R2) between unipolar electrogram amplitude and the percentage of amyloid tissue, as well as between bipolar electrogram amplitude and the percentage of fibrous tissue. On the other hand, electrogram duration and the number of electrogram peaks were unrelated to histological findings. The unipolar voltage cutoff that best identified regions with >15% amyloid tissue infiltration according to Youden index was 9.1 mV (sensitivity, 43%; specificity, 100%; accuracy, 77%). CA is associated with preserved electrogram amplitudes at high-density electroanatomical mapping with conventional voltage cutoffs. Nevertheless, unipolar electrogram amplitude is strongly related to the extent of amyloid infiltration, and unipolar voltage<9.1 mV is 100% specific for >15% amyloid tissue deposition.

PO-01-192 USE OF A LARGE-FOOTPRINT FOCAL LATTICE CATHETER FOR MAPPING AND ABLATION OF ATRIAL FLUTTERS

Catheter ablation of atrial flutters (AFL), in particular atypical (ie non-cavotricupid isthmus dependent) AFL, can be eliminated with high-density electroanatomical mapping using multielectrode catheters used in concert with radiofrequency ablation (RFA). However, this requires 2 separate complex catheters: for mapping and for ablation. Further challenges include difficulties in establishing durable block across the isthmus of identified circuits, in particular (but not exclusively) the mitral isthmus. Recently, a large footprint lattice-tip catheter (Sphere-9, Affera-Medtronic Inc.) has been developed capable of both delivering either pulsed field (PF) energy or high-power RF energy, and performing high-density mapping using mini-electrodes located throughout the lattice-tip. To determine the feasibility and efficacy, both acute and chronic, of mapping and ablation of AFL using the lattice-tip catheter. As part of a 3-center, single-arm, first-in-human study of AF ablation with the lattice-tip catheter (NCT04141007, NCT04194307), spontaneous or induced AFLs were mapped and ablated using the lattice-tip catheter, in conjunction with a compatible mapping-system. The 7Fr lattice-tip catheter has a compressible 9-mm nitinol tip with 9 embedded mini-electrodes, and is able to deliver either RF or PF energy (each lesion 2-5 sec). During AF ablation in the 178-pt cohort (39% paroxysmal, 61% persistent), AFL was identified in 47 (26%) pts. This included typical AFL in 22 (12%) pts, peri-mitral AFL in 17 (10%) and other AFLs in 26 (15%). Mapping of the AFL circuits was performed exclusively using the lattice catheter. Cavo-tricuspid isthmus (CTI), LA roof, and mitral isthmus lines were targeted in 94%, 83%, and 70% of patients in whom AFLs were identified (some flutters were not targeted flutters if not considered clinically-relevant). Bidirectional conduction block was achieved in all (100%) of attempted lines. Over a 12-month follow-up, 37 of 47 pts (79%) were free from AFL recurrence. Atrial flutters are noted in a substantial number of patients undergoing catheter ablation of atrial fibrillation. The flexibility of a large-tip focal lattice catheter allows for facile post-PVI mapping and ablation of such flutters, while minimizing the need for additional equipment and catheter exchanges. Ablation using either RF or PF energy resulted in successful block across attempted linear lesions and excellent long-term success.

3D-electroanatomical mapping of the left atrium and catheter-based pulmonary vein isolation in pigs: A practical guide.

To propose a standardized workflow for 3D-electroanatomical mapping guided pulmonary vein isolation in pigs. Danish female landrace pigs were anaesthetized. Ultrasound-guided puncture of both femoral veins was performed and arterial access for blood pressure measurement established. Fluoroscopy- and intracardiac ultrasound-guided passage of the patent foramen ovale or transseptal puncture was performed. Then, 3D-electroanatomical mapping of the left atrium was conducted using a high-density mapping catheter. After mapping all pulmonary veins, an irrigated radiofrequency ablation catheter was used to perform ostial ablation to achieve electrical pulmonary vein isolation. Entrance- and exit-block were confirmed and re-assessed after a 20-min waiting period. Lastly, animals were sacrificed to perform left atrial anatomical gross examination. We present data from 11 consecutive pigs undergoing pulmonary vein isolation. Passage of the fossa ovalis or transseptal puncture was uneventful and successful in all animals. Within the inferior pulmonary trunk 2-4 individual veins as well as 1-2 additional left and right pulmonary veins could be cannulated. Electrical isolation by point-by-point ablation of all targeted veins was successful. However, pitfalls including phrenic nerve capture during ablation, ventricular arrhythmias during antral isolation close to the mitral valve annulus and difficulties in accessing right pulmonary veins were encountered. Fluoroscopy- and intracardiac ultrasound-guided transseptal puncture, high-density electroanatomical mapping of all pulmonary veins and complete electrical pulmonary vein isolation can be achieved reproducibly and safely in pigs when using current technologies and a step-by-step approach.

Biophysical Tissue Characterization of Ventricular Tachycardia Substrate With Local Impedance Mapping to Predict Critical Sites

BackgroundNew tools are needed to improve ventricular tachycardia (VT) substrate characterization and optimize outcomes. LI provides biophysical tissue characterization. ObjectivesThe purpose of this study was to test local impedance (LI)-based mapping to predict critical ventricular tachycardia components after myocardial infarction (MI). MethodsOne month after a nonreperfused anterior MI, endo-epicardial high-density electroanatomic mapping and endocardial LI mapping were performed in 23 Landrace Large X White pigs. LI thresholds were set using the blood pool value to define a 10 Ω range: low (<blood pool −1Ω), intermediate (≥blood pool −1Ω and ≤blood pool +9Ω), and high (normal) tissue resistance (>blood pool +9Ω). ResultsLow LI was detected in low-voltage areas in 100% of cases, but intermediate LI was found in both core (87%) and border zone (12.5%) voltage areas. A total of 17 VTs were induced (VT isthmus identified in 9 animals). VT inducibility was associated with the size of intermediate LI area (OR: 1.19 [95% CI: 1.0-1.4]; P = 0.039) and the presence of specific LI patterns: LI corridor (OR: 15.0 [95% CI: 1.3-169.9]; P = 0.029); LI gradient (OR: 30.0 [95% CI: 2.1-421.1]; P = 0.012), high LI heterogeneity (OR: 21.7 [95% CI: 1.8-260.6]; P = 0.015), and presence of ≥2 low LI regions (OR: 11.3 [95% CI: 1.0-130.2]; P = 0.053). Potential VT isthmuses were in areas of intermediate LI and colocalized to LI patterns associated with VT inducibility in all cases (LI corridors or LI gradient). Low LI regions did not actively participate in the VT circuit (0%). ConclusionsLI mapping is feasible and may add useful characterization of the VT substrate. Specific LI patterns (ie, corridors, gradients) were associated with VT inducibility and colocalized with the VT isthmus, thus representing a potential new target for ablation in substrate-based procedures.

Atrial fibrillatory wave amplitude revisited: A predictor of recurrence after catheter ablation independent of the degree of left atrial structural remodeling.

The fibrillatory wave amplitude (FWA) during atrial fibrillation (AF) is thought to reflect structural atrial remodeling, but it remains unclear what determines the FWA. 114 consecutive patients were prospectively studied who underwent catheter ablation of AF. The mean FWA was computed by automated surface ECG analyses. The extent of the left atrial (LA) voltage-defined atrial fibrosis and conduction properties were estimated by a three-dimensional high-density electroanatomical mapping system. The LA size was evaluated by transthoracic echocardiography. The study patients were divided into 2 groups according to an FWA in lead V1 above the median value of 46 µV (high FWA group, n=57) or below 46 µV (low FWA group, n=57). There were no differences in the age, gender, CHADS2 score, prevalence of paroxysmal AF, medications, ablation strategy, and LA volume index between the two groups. The LA low voltage areas in the low FWA group were not different from those in the high FWA group. The total LA activation time and local LA conduction velocity did not differ between the two groups. During a median follow-up of 710 days, the recurrence rate after ablation was significantly higher in patients with a low FWA than a high FWA (log-rank P=0.02). In a multivariate analysis, non-paroxysmal AF, the LA volume index, and FWA were independent predictors of recurrence after ablation. The FWA was not correlated with the markers of atrial structural remodeling. Nevertheless, the FWA could still provide information for predicting the clinical outcome after AF ablation.