Endocardial Electroanatomic Mapping Research Articles

Optimal pixel signal intensity threshold for the assessment of endocardial left-ventricular scar by 3D dark blood MRI compared to bipolar voltage electro-anatomical mapping

Abstract Background Late gadolinium enhancement (LGE) MRI is considered the standard for noninvasive assessment of 3D scar architecture. Intraprocedural integration of 3D scar models improve the outcome of catheter ablation for ventricular tachycardia (VT). A pixel signal intensity (PSI) cut-off of 40 to 60% has been widely used for conventional bright-blood LGE MRI. Novel 3D MRI acquisitions with dark-blood (DB) nulling with higher spatial resolution and superior detection of (subendocardial) scar patterns are increasingly available, but the optimal pixel signal intensity (PSI) value remains unknown. Purpose To compare the accuracy of the 3D DB MRI-derived endocardial scar reconstructions at three different PSI cut-offs with endocardial electro-anatomical contact mapping in patients with scar-related VT. Methods Preprocedural 3D DB LGE MRIs were retrospectively compared to high-density endocardial left-ventricular (LV) bipolar voltage mapping (cut-off 0.5-1.5mV) obtained during endocardial mapping at sinus rhythm using the ADAS3D software. The LV scar models were aligned using the mitral valve, left ventricular apex and aorta cusps. Points with a Euclidean node-to-node distance of ≥10 mm were excluded. Variable upper PSI thresholds were set at 50%, 60% and 70%; the lower threshold at two-thirds of the upper limit. The 10% LV layer from the 3D MRI was used. The pairs of points were checked for agreement for scar or healthy (%). The Pearson correlation was used to analyze the agreement between core scar, border zone and healthy tissue area (in %) at three thresholds. Results Ten patients (90% male, mean age 65±11 year, 8 ischemic/2 nonischemic, LV ejection fraction 41±6%) were analyzed. A mean of 2024 (range 385-6810) pairs were analyzed per patient at three PSI thresholds. A correct correlation for scar or healthy was present in 67%, 69% and 69% for the upper PSI thresholds of 50%, 60% and 70% respectively. The optimal match was obtained for an upper PSI cutoff value of 70%, for healthy (r2=0.57; P=0.01), border zone (r2=0.73; P=0.01), 50% for core (r2=0.09; P=0.39). Using a 60% PSI cutoff the scar core % increased significantly compared to the 70% cutoff (12.8 ±13.8 versus 4.9±7.3, P=0.001). Conclusion The optimal depiction of the boundary between healthy and border zone scar by 3D DB MRI is best depicted at an upper PSI threshold of 70%.

Endomyocardial substrate of ventricular arrhythmias in patients with autoimmune rheumatic diseases.

Delayed enhancement-magnetic resonance imaging (DE-MRI) has demonstrated that nonischemic cardiomyopathy is mainly characterized by intramural or epicardial fibrosis whereas global endomyocardial fibrosis suggests cardiac involvement in autoimmune rheumatic diseases or amyloidosis. Conduction disorders and sudden cardiac death are important manifestations of autoimmune rheumatic diseases with cardiac involvement but the substrates of ventricular arrhythmias in autoimmune rheumatic diseases have not been fully elucidated. 20 patients with autoimmune rheumatic diseases presenting with ventricular tachycardia (VT) (n = 11) or frequent ventricular extrasystoles (n = 9) underwent DE-MRI and/or endocardial electroanatomical mapping of the left ventricle (LV). Ten patients with autoimmune rheumatic diseases underwent VT ablation. Global endomyocardial fibrosis without myocardial thickening and unrelated to coronary territories was detected by DE-MRI or electroanatomical voltage mapping in 9 of 20 patients with autoimmune rheumatic diseases. In the other patients with autoimmune rheumatic diseases, limited regions of predominantly epicardial (n = 4) and intramyocardial (n = 5) fibrosis or only minimal fibrosis (n = 2) were found using DE-MRI. Endocardial low-amplitude diastolic potentials and pre-systolic Purkinje or fascicular potentials, mostly within fibrotic areas, were identified as the targets of successful VT ablation in 7 of 10 patients with autoimmune rheumatic diseases. Global endomyocardial fibrosis can be a tool to diagnose severe cardiac involvement in autoimmune rheumatic diseases and may serve as the substrate of ventricular arrhythmias in a substantial part of patients.

Association between left ventricular wall-thickness by CT and endocardial voltage potentials in patients with ischemic cardiomyopathy

Abstract Funding Acknowledgements Type of funding sources: None. Background Although cardiac magnetic resonance (CMR) is the gold standard for planning ventricular tachycardia (VT) ablation, its accuracy is hindered in patients with implanted cardiac defibrillators (ICD) and resynchronization therapy (CRT). Cardiac computed tomography (CT) has emerged as an alternative for ablation planning in these patients. This pilot study aimed to evaluate the relationship between wall thickness (WT) on CT and voltage of electrical potentials on endocardial electroanatomic mapping (EAM) in patients with ischemic cardiomyopathy. Methods Single centre retrospective study enrolling consecutive patients with ischemic cardiomyopathy referred for endocardial VT ablation that underwent cardiac CT for procedure planning since 2021. Patients were excluded if EAM had < 1000 data points. ADAS 3D® software was used to analyse CT images, automatically segmenting the left ventricle (LV) into the 17 American Heart Association segments and calculating end-diastolic WT for each one. Four standardized views (anterior-posterior, posterior-anterior, superior, and inferior) of the segmented LV on ADAS 3D® were used to aid in manual segmentation of the EAM. The endocardial voltage maps were created using CARTO3® software (Figure 1). For each patient, EAM was interpreted to create 2 different bulls’ eye maps, according to the presence or absence of bipolar potentials < 0.5 (dense scar) or < 1.5mV (low voltage). Only segments with >20% extension of low bipolar voltage were considered as altered. Results We included a cohort of 8 patients (mean age 67±12 years, 87.5% male, median LVEF of 32% [IQR 25-49]). All but one patient had implanted cardiac device (6 ICD, 1 CRT-D). Cardiac CT was performed 1 day (IQR 0-2) before the ablation. Overall, 136 segments were analysed, 8 of which did not have voltage information. Of the remaining 128, 51 (39.8%) had dense scar and 57 (41.9%) had low voltage. There was a good correlation between mean WT and the presence or absence of both dense scar (area under de curve (AUC) 0.799, p<0.001) and low voltage (AUC 0.838, p<0.001) in each LV segment. Conclusion WT measured by CT appears to have a strong correlation with dense scar and low voltage in EAM in patients with ischemic cardiomyopathy undergoing VT ablation. This technique may be useful to plan interventions in patients in whom CMR is not feasible.

Clinical evaluation of the new 12-lead ECG noninvasive epi-endocardial mapping technology

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): XSpline S.p.a. Aim Noninvasive electrocardiographic mapping systems may require multichannel (150-250) ECG body surface recordings which is a huge limitation for the adoption into clinical practice. However, most of the currently available noninvasive mapping systems accurately represent epicardial activation. Over the last few years, various technical solutions have been implemented to increase the accuracy of ECG forward-inverse calculations including machine learning algorithms. We developed a novel 12-lead ECG-based, fully automated system for noninvasive full transmural (epi-endocardial) mapping. The aim of this study was to evaluate accuracy of this system in heart failure patients with typical LBBB. Methods Eight consecutive patients (median age: 65; 25-75% range 59-64; 5 male) with typical LBBB QRS morphology (QRS duration 146–224 ms), scheduled for CRT implantation underwent a cardiac CT scan and 12-lead ECG recording, followed by detailed bi-ventricular endocardial electroanatomical contact mapping (EAM). A median of 258 (181-576) local electrograms in LV and 86 (70-139) in RV were collected during EAM. Cardiac CT data were semiautomatically processed using a Unet-like neural network to obtain meshes containing the heart (each chamber with both endocardial and epicardial contour as well as coronary sinus and its branches), lungs and torso using different segmentation module. Noninvasive epi-endocardial activation maps were calculated using state-of-the-art mathematical models including machine learning methods. These data were compared with EAM from the invasive mapping system using Spearman correlation (r), mean absolute error (MAE) and relative distance metrics. Results All early and latest activation patterns were correctly identified (see figure). The average correlation (r) of endocardial activation maps was 0.92 for all cases (min-max: 0.82-0.96). MAE was rather small (9-15 mm) when the non-invasive late activation zone nearly matches the CARTO data (average distance error 14 mm). Overall, the QRS complex was correctly reproduced by our method in all cases (r = 0.96). Conclusions This study shows that new mapping technique can accurately reconstruct endocardial electrical activation maps based on 12-lead ECG and cardiac CT scan. The approach may be very useful in pre-procedural planning of device implantation and catheter ablation. Larger validation studies are however needed for confirming method accuracy at epicardial site.

PO-05-069 ASSOCIATION BETWEEN LEFT VENTRICULAR WALL-THICKNESS BY CT AND ENDOCARDIAL VOLTAGE POTENTIALS IN PATIENTS WITH ISCHEMIC CARDIOMYOPATHY UNDERGOING VT ABLATION

Although cardiac magnetic resonance (CMR) is the gold standard for planning ventricular tachycardia (VT) ablation, its accuracy is hindered in patients with implanted cardiac defibrillators (ICD) and resynchronization therapy (CRT). Cardiac computed tomography (CT) has emerged as an alternative for ablation planning in these patients. This pilot study aimed to evaluate the relationship between wall thickness (WT) on CT and voltage of electrical potentials on endocardial electroanatomic mapping (EAM) in patients with ischemic cardiomyopathy. Single centre retrospective study enrolling consecutive patients with ischemic cardiomyopathy referred for endocardial VT ablation that underwent cardiac CT for procedure planning since 2021. Patients were excluded if EAM had < 1000 data points. ADAS 3D® software was used to analyse CT images, automatically segmenting the left ventricle (LV) into the 17 American Heart Association segments and calculating end-diastolic WT for each one. Four standardized views (anterior-posterior, posterior-anterior, superior, and inferior) of the segmented LV on ADAS 3D® were used to aid in manual segmentation of the EAM. The endocardial voltage maps were created using CARTO3® software (Biosense Webster®). For each patient, EAM was interpreted to create 2 different bulls’ eye maps, according to the presence or absence of bipolar potentials < 0.5 (dense scar) or < 1.5mV (low voltage). Only segments with >20% extension of low bipolar voltage were considered as altered. We included a cohort of 8 patients (mean age 67±12 years, 87.5% male, median LVEF of 32% [IQR 25-49]). All but one patient had an implanted cardiac device (6 ICD, 1 CRT-D). Cardiac CT was performed 1 day (IQR 0-2) before the ablation. Overall, 136 segments were analysed, 8 of which did not have voltage information. Of the remaining 128, 51 (39.8%) had dense scar and 57 (41.9%) had low voltage. There was a good correlation between mean WT and the presence or absence of both dense scar (area under de curve (AUC) 0.799, p<0.001) and low voltage (AUC 0.838, p<0.001) in each LV segment. WT measured by CT appears to have a strong correlation with dense scar and low voltage in EAM in patients with ischemic cardiomyopathy undergoing VT ablation. This technique may be useful to plan interventions in patients in whom CMR is not feasible.

161 ABLATION OF EPICARDIAL VENTRICULAR TACHYCARDIA ORIGINATING IN THE AREA OF PERICARDIAL ADHESIONS INDUCED BY STEREOTACTIC RADIOABLATION IN A PATIENT WITH ISCHEMIC CARDIOMYOPATHY

Abstract This is the case of a 64-year-old male patient with prior inferior wall myocardial infarction, wearing a cardiac resynchronization therapy defibrillator and suffering from recurrent ventricular tachycardia (VT). The patient had undergone a transitory successful endocardial radiofrequency catheter ablation (RFCA) in 2013 and a stereotactic ablative body radiotherapy (SABR) in 2021, targeting the VT originating in the inferior wall myocardial scar. The patient was referred to our institution due to recurrent highly symptomatic slow-VT. A coronary angiography ruled out coronary artery disease (CAD) progression and a RFCA was rescheduled. Given the suspected epicardial origin of VT based on a 12-lead ECG, the decision was made to perform a combined epi-endocardial ablation. SABR-induced pericardial adhesions prevented posterior pericardial access, thus requiring an anterior access approach (Figure 1, Panel A, yellow star). Following epicardial and endocardial electroanatomic mapping (EAM), VT ablation relied on a substrate-based approach. Local abnormal ventricular activities (LAVAs), detected both in the accessible epicardial inferior wall of the left ventricle and at the opposite endocardial site, were eliminated by radiofrequency (RF) current. Upon completion of endocardial ablation, ventricular pacing induced hemodynamically unstable VT, exiting from the epicardial region corresponding to the SABR-induced pericardial adhesions. Mechanical adhesiolysis, using the elbow of the open-irrigated ablation catheter, was performed to disrupt SABR-induced pericardial adhesions in the inferior wall. The epicardial EAM performed with the open-irrigated catheter recorded LAVAs in the infero-posterior wall of the left ventricle, corresponding to the SABR-disrupted pericardial adhesions. A RF current was delivered, targeting LAVAs at this site (Figure 1, Panel B: the central green dot corresponds to the area of disrupted pericardial adhesions). At the end of the procedure, no sustained VT was induced by programmed ventricular stimulation. Conclusion SABR constitutes a novel and promising non-invasive radioablative treatment of VT, potentially associated with cardiac toxicity. To our knowledge, this is the first reported case of combined epicardial and endocardial RFCA of recurrent VT after SABR. Based on the first RFCA report and exclusion of CAD progression, we hypothesized that SABR might have favoured progression of the inferior low voltage area. With this case report, we would like to demonstrate that even if pericardial adhesions could be a consequence of SABR, gentle catheter-driven manoeuvres can be enough to disrupt the adhesions and to achieve full EAM. Further research is mandatory to shed light on SABR's long-term arrhythmogenic role.

Intrapericardial cardiosphere-derived cells hinder epicardial dense scar expansion and promote electrical homogeneity in a porcine post-infarction model.

The arrhythmic substrate of ventricular tachycardias in many structural heart diseases is located in the epicardium, often resulting in poor outcomes with currently available therapies. Cardiosphere-derived cells (CDCs) have been shown to modify myocardial scarring. A total of 19 Large White pigs were infarcted by occlusion of the mid-left anterior descending coronary artery for 150min. Baseline cardiac magnetic resonance (CMR) imaging with late gadolinium enhancement sequences was obtained 4 weeks post-infarction and pigs were randomized to a treatment group (intrapericardial administration of 300,000 allogeneic CDCs/kg), (n = 10) and to a control group (n = 9). A second CMR and high-density endocardial electroanatomical mapping were performed at 16weeks post-infarction. After the electrophysiological study, pigs were sacrificed and epicardial optical mapping and histological studies of the heterogeneous tissue of the endocardial and epicardial scars were performed. In comparison with control conditions, intrapericardial CDCs reduced the growth of epicardial dense scar and epicardial electrical heterogeneity. The relative differences in conduction velocity and action potential duration between healthy myocardium and heterogeneous tissue were significantly smaller in the CDC-treated group than in the control group. The lower electrical heterogeneity coincides with heterogeneous tissue with less fibrosis, better cardiomyocyte viability, and a greater quantity and better polarity of connexin 43. At the endocardial level, no differences were detected between groups. Intrapericardial CDCs produce anatomical and functional changes in the epicardial arrhythmic substrate, which could have an anti-arrhythmic effect.

Assessing the field of view of multisize electrodes in ischemic cardiomyopathy by validating against ex-vivo high resolution cardiac magnetic resonance

Abstract Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): Leiden University Medical Centre Background Substrate identification after myocardial infarction (MI) relies on voltage mapping. Early reperfusion results in non-transmural scar (NTS). Narrow-spaced microelectrodes (ME) are thought to have a limited field of view (FOV). The role of ME for delineation of NTS is unclear. Purpose To evaluate mapping with multi-size electrodes for identifying NTS, validated against high-resolution ex-vivo cardiac magnetic resonance imaging (HR-LGE-CMR). Methods Nine swine with early reperfusion MI underwent endocardial electroanatomical voltage mapping (EAVM) with the QDOT catheter which incorporates three ME in the 3.5mm tip electrode. HR-LGE-CMR (0.3mm slices) were obtained and merged with EAVM. At each EAVM point a transmural cylinder (5mm radius) was projected on the CMR and the volume of viable myocardium (VM) in the cylinder quantified (Otsu method). Unipolar (UV) and bipolar (BV) voltages from conventional (c) and microelectrodes (µ) were related to VM. Cut-off values for normal myocardium were based on 5th percentiles of areas without fibrosis. Results In each swine 220 (IQR 216-260) mapping points were collected (total 2322 points). Cut-off for normal myocardium were 3.18 mV, 0.85 mV, 3.28mV and 1.93 mV for UVc, BVc, UVµ and BVµ, respectively. Wall thickness (WT) was reduced in areas with fibrosis vs. no fibrosis (5.4mm, IQR 3.2- 6.9 vs. 7.4mm, IQR 5.3 - 9.6). All voltages were reduced at sites with fibrosis vs. no fibrosis (UVs 4.4mV vs. 6.8mV; BVc 1.2mV vs. 2.1mV; UVµ 2.5mV vs. 5.5mV, and BVµ 2.9mV vs. 5.4mV, all p&amp;lt;0.001). For areas with any fibrosis, all voltages increased with increasing WT up to the maximal WT of 13mm (fig. 1). Similarly, all voltages increased with an increase in VM volumes from &amp;gt;200mm3 to &amp;gt;600 mm3 (equivalent to a cylinder with h=7.64mm) (fig. 2) with the strongest correlation for UVµ (r=0.47). Below a volume of 200mm3 VM voltages did not correlate significantly with VM. Conclusion In NTS, UVc, BVc, and, notably, BVµ and UVµ increase with increasing WT and increasing transmural volume of VM, with the biggest role perhaps laid out for UVµ to estimate transmural VM. EAVM cannot accurately delineate areas with the lowest amount of VM, potentially due to insufficient far field cancellation in NTS. Both these findings argue against a limited FOV of ME.

Right Ventricular Endocardial Mapping and a Potential Arrhythmogenic Substrate in Cardiac Amyloidosis—Role of ICD

Patients with cardiac amyloidosis (CA) have an increased risk of sudden cardiac death. (SCD). However, the role of an implantable cardioverter-defibrillator in the primary prevention of SCD in this group of patients is still controversial. We present a case with CA with recurrent syncope and non-sustained ventricular tachycardia. In order to further stratify the risk of SCD, an electrophysiological study with endocardial electroanatomic voltage mapping was performed prior to the ICD placement.

Excision of a rare cardiac tumor aided by endocardial electroanatomical mapping

Glomus tumors are rare benign soft tissue lesions, most commonly found on the skin. They are an extremely rare cause of the cardiac tumor. We report a case of right atrial glomus tumor excised using a novel technique utilizing cardiac electroanatomical mapping techniques ordinarily used for arrhythmia surgery.

Accuracy of electroanatomical mapping guided cardiac radiotherapy for ventricular arrhytmias: pitfalls and solutions

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was partially supported by the grant AZV NU20-02-00244 from the Ministry of Health of the Czech Republic OnBehalf WECAM Background One of the main limitations of Radiofrequency catheter ablation (RFCA) is the difficulty in targeting specific VT substrate locations when they are deep intramural, covered by epicardial fat or in the proximity of a coronary artery. Stereotactic body radiotherapy (SBRT) has emerged as an alternative treatment for VT after RFCA failure. However, the accuracy of substrate volume delineation, the gross target volume (GTV), based on electroanatomical mapping (EAM) and interobserver agreement are still unknown. Aim To analyze and optimize the interobserver agreement for GTV delineation on cardiac CT (CCT) based on EAM data acquired to guide radiotherapy for ventricular arrhythmias. Method Available EAM data was exported and merged with the segmented CCT using manual registration by two observers. A GTV was created by the observers for predefined left ventricular (LV) areas based on preselected endocardial EAM points, indicating the 2D-surface area of interest. The interobserver (non)overlapping GTV volumes were analyzed. The influence of (interobserver) registration accuracy and availability of EAM data on the final GTV and 2D-surface location within each LV area was evaluated. Results The median distance between the CCT and EAM after registration was 2.7 mm, 95%th percentile 6.2 mm for observer #1 and 3.0 mm, 95%th percentile 7.6 mm for observer #2 (p = 0.9). Created GTVs were significantly different (8 vs 19 ml) with lowest GTV overlap (35%) for lateral wall target areas. Similar, the highest shift between 2D-surfaces was observed for the lateral LV (6.4mm (3.0-9.9)). The same trend is seen in the (non) overlapping volume for lateral area (P = 0.004). The optimal surface registration accuracy (2.6 mm) and interobserver agreement (Δ interobserver EAM surface registration accuracy 1.32 mm) on final GTVs could be achieved if at least three cardiac chambers were mapped, including high-density LV EAM. Conclusion Detailed EAM of at least three chambers allows for accurate co-registration of EAM data with CCT and high interobserver agreement on GTVs to guide radiotherapy of ventricular arrythmias. However, the substrate location should be taken in consideration when creating a treatment volume margin. Gross target volume (GTV) and InterobserGTV volume Observer #1 (cc)GTV volume Observer #2 (cc)Surface shift (mm)Basal anterior, (IQR)7.6 (6.2-11.5)9.3 (5.3-10)3.8 (2.2-4.5)Lateral, (IQR)8.0 (6.9-12.7)19.1 (15.7-21.4)6.2 (5.3-6.4)Septal, (IQR)10.1 (6.2-12.8)13.9 (7.7-14.6)6.4 (3.0-9.9)Abstract Figure. Graphical abstract

In-vivo validation of non-invasive electrocardiographic imaging based on the equivalent double layer source model using epicardial and endocardial electroanatomical mapping

Abstract Background Noninvasive electrocardiographic imaging (ECGi) using the equivalent double layer (EDL) source model enables both epicardial and endocardial reconstruction of electroanatomical activation patterns during sinus rhythm. The EDL source model has been validated in torso-tank models and animal experiments, however validation in humans using invasive electroanatomical mapping is limited. Purpose Validation of EDL based ECGi using invasive electroanatomical mapping. Methods Ten patients referred for epicardial and endocardial electroanatomical mapping underwent 67 electrode body surface potential mapping (BSPM), cardiac CT imaging and 3D imaging of electrode positions. Anatomical models of the ventricles, lungs and thorax were created and supplemented with electrode positions. Invasive epicardial (4020±1514 contact points), right ventricle endocardial (724±113 contact points) and left ventricle endocardial (459±117 contact points) local activation timing (LAT) maps were compared to ECGi derived LAT maps. Results Included patients (mean age 48±21 years, 80% males) were diagnosed with either arrhythmogenic cardiomyopathy (N=4), dilated cardiomyopathy (N=1), symptomatic premature ventricular complexes (N=3) or myocarditis (N=2). Measured BSMP highly correlated with simulated BSPM (97±2%) with a relative difference of 24% ± 6%. Source models consisted of a mean of 2614±214 nodes with a mean distance between nodes of 8.3±1 mm. Overall, invasive LAT maps and ECGi derived LAT maps showed reasonable correlation for epicardial maps (49% ± 18%) and endocardial maps of the right ventricle (48% ± 27%). Endocardial left ventricular LAT maps showed less correlation (23% ± 28). The absolute difference between invasive and ECGi LAT maps was 16.7±14.2 ms for epicardial maps, 17.2±12.9 ms for right ventricle endocardial maps and 34.0±19.8 ms for left ventricle endocardial maps. Visual comparison showed corresponding areas of breakthrough and regions of latest activation in all cases (Figure). Quantitative comparison of these areas showed a mean absolute difference of 33±7mm or 19±10 ms for epicardial maps, 25±10 mm or 17±13 ms for right ventricle endocardial maps and 39±16 mm or 20±6 ms for left ventricular endocardial maps. Conclusion Overall agreement was observed between EDL based ECGi LAT maps and electroanatomical LAT maps. Future research will focus on further quantification of this agreement and improvement of ECGi mapping accuracy. Funding Acknowledgement Type of funding source: Foundation. Main funding source(s): Netherlands Cardiovascular Research Initiative, an initiative with support of the Dutch Heart Foundation and UCL Hospitals NIHR Biomedical Research Centre.

Multipolar mapping for catheter ablation of premature ventricular complexes originating from papillary muscles in the structurally normal heart: a case series

BackgroundPrevious studies on radiofrequency catheter ablation of premature ventricular complexes (PVCs) arising from the left ventricle (LV) papillary muscles (PM) show a modest procedural success rate with higher recurrence rate. Our study sought to explore the utility of using a multipolar mapping with a steerable linear duodecapolar catheter for ablating the PM PVCs.MethodsDetailed endocardial multipolar mapping was performed using a steerable linear duodecapolar catheter in 6 consecutive PM PVCs patients with structurally normal heart. The clinical features and procedural data as well as success rate were analysed.ResultsLV endocardial electroanatomic mapping was performed in all patients via a retrograde aortic approach using a duodecapolar mapping catheter. All patients displayed a PVC burden with 16.2 ± 5.4%. Duodecapolar catheter mapping demonstrated highly efficiency with an average procedure time (95.8 ± 7.4 min) and fluoroscopy time (14.2 ± 1.5 min). The mean number of ablation applications points was 6.8 ± 1.9 with an average overall ablation duration of 6.1 ± 3.0 min. The values of earliest activation time during mapping using duodecapolar catheter were 37.8 ± 7.2 ms. All patients demonstrated acute successful ablation, and the PVC burden in all patients after an average follow-up of 8.5 ± 2.0 months was only 0.7%. There were no complications during the procedures and after follow-up.ConclusionsMapping and ablation of PM PVCs using a duodecapolar catheter facilitated the identification of earliest activation potentials and pace mapping, and demonstrated a high success rate during follow-up.

P565First characterization of high-power short-duration radiofrequency ablation with remote magnetic navigation assistance

Abstract Funding Acknowledgements MEYS- CR (ref#LQ1605 and LM2015062) Background/Introduction High-power short-duration (HPSD) radiofrequency (RF) ablation relies on the application of intense thermal fields for a carefully restricted time, in order to quickly obtain deep but precise lesions that spare the structures surrounding the heart. The approach is still under evaluation across different therapies and catheter technologies. To the present day there is no available characterization of HPSD ablation supported by remote magnetic navigation (RMN). Purpose To describe the safety issues regarding HPSD ablation in atria and ventricles with RMN systems, while characterizing the thermal lesion size and continuity in an acute closed-chest swine model. Methods The animal trial was divided in two arms (left ventricular and atrial). 10 female large white pigs (6-month-old weight 55-65 kg) were employed in each arm. Endocardial electroanatomical mapping and ablation were performed with RMN assistance to provide stable contact and flexible maneuvering. The ventricular cohort was divided in 5 power settings (30-40-50-60-70W). Multiple RF applications (10 ca./animal) were delivered until a pop occurred or up to 60s. In the atrial cohort the animals were divided by a combination of power/application time (50W/20s – 70W/10s – 90W/4s). Intracaval right atrial ablation lines and postero-lateral left atrial lines were performed in a point-by-point fashion (ca. 4mm distance). Irrigation rate was 30ml/min. The ventricular lesions were measured via software after 9.4T MRI of fixed hearts. The atrial lesions were measures during pathological examination after explanation. Results In the ventricular arm, we obtained a safety calibration curve linking the imposed power setting to the maximal time of application. The time before a pop decreased non-linearly from 60s down to 17.69 ± 8.21 s at 70W. No statistically significant differences were observed when comparing lesions depth, width and volume among the selected power settings. In the atrial arm we observed on the post-ablation maps a significant decrease of intracaval lesions (i.e. area with bipolar voltage &amp;lt;1.5mV) width (17.57 ± 1.89 mm for 50W/4s down to 10.16 ± 1.56 mm for 90W/4s). Pericardial, pleural and aortic damages were visible across all the employed settings, with less pronounced alterations for 90W/4s. Transmural lesions were visible both on the right and left atrium, with evident gaps for 50W/20s. Conclusion The presented work assesses for the first time the safety limits of HPSD ablation on healthy ventricular myocardium. We provide a calibration curve for faster RF ablation with comparable lesion features. Furthermore, we expanded the previously reported application in the atrium adding the benefits of stable controlled contact provided by RMN systems. We highlighted the benefits (e.g. faster, continuous and localized lesion formation) and risks for peripheral structures using HPSD ablation for supraventricular tachycardia interventions. Abstract Figure.

P1010Association between left atrial fibrosis detected by cardiac magnetic resonance and endocardial electroanatomic mapping in the evaluation of the electrophysiological substrate in atrial fibrillation

Abstract Background Atrial fibrillation (AF) is related to left atrial fibrosis, but its identification by late magnetic resonance imaging (LGE) with gadolinium (LGE) persists in controversy due to heterogeneous results in its correlation with the electroatomic map (EAM) and the difficulty of perform histological studies in humans. Purpose We try to examine the point-by-point association between high density EAM and LGE-MRI using an automatic and reproducible method. Methods A LGE-MRI was performed in 16 patients prior to ablation. Three different areas were established depending on the intensity of normalized enhancement for each patient according to their blood group with the image intensity ratio (IIR) (healthy &amp;lt;1.20, border area (BZ) ≥1.20 &amp;lt;1.32 and scar ≥1.32). The high density electroanatomic maps of the left atrium (LA) were projected onto the MRI, obtaining an automatic correlation point by point. Results The study obtained significant differences (p &amp;lt; 0.001) between voltage (mV) and CV (mm/ms) among healthy, BZ and scar areas, as well a significant inverse correlation (p &amp;lt; 0.001) between voltage and IIR (R=-0.39). It obtained too a significant correlation between CV and IIR (R=-0.24), but this showed a greater correlation in those patients who have the least dilated LA (p = 0.02). Conclusions LGE-MRI and EAM showed good correlation in delineating potential pathologic substrate in AF, but left atrium dilation could reduce the performance of the CMR in this task. Conduction velocity could be more sensitive than voltage and LGE-MRI to detect incipient substrate in AF. Voltage and conduction velocity values Area /IIR Velocity (mm/ms) Voltage (mV) I / &amp;lt;.20 1.036(0.913-1.158) 1.593(1.489-1.696) 2 / ≥1.20 and &amp;lt;1.32 0.722(0.590-0.850) 0.792 (0.649-0,935) 3 / ≥1.32 0.623(0.473-0,733) 0.444(0.245-0.642) Voltage and conduction velocity values in the three areas of the LGE-RMN. Abstract Figure. Correlation among voltage, VC and LA

Endocardial electro-anatomic mapping in healthy horses: Normal sinus impulse propagation in the left and right atrium and the ventricles

Understanding the depolarisation pattern of the equine heart under normal physiologic conditions, and its relationship to the surface electrocardiogram (ECG), is of uppermost importance before any further research can be done about the pathophysiology of complex arrhythmias. In the present study, a 3D electro-anatomical mapping system was used to evaluate the qualitative and quantitative depolarisation patterns and correlation to the surface ECG of both the atrial and ventricular endocardium in seven healthy horses in sinus rhythm under general anaesthesia. Bipolar activation maps of the endocardium were analysed.The first atrial activation was located at the height of the terminal crest. Only one interatrial conduction pathway was recognised. The first and second P wave deflections represent the right and left atrial depolarisation, respectively. Bundle of His electrograms could be recorded in 5/7 horses. Left ventricular activation started at the mid septum and right ventricular activation started apically from the supraventricular crest. This was followed by separate depolarisations at the height of the mid free wall. Further ventricular depolarisation occurred in an explosive pattern. Electrically active tissue could be found in all pulmonary veins. In contrast to findings of previous studies, all parts of the ventricular depolarisation contributed to the surface ECG QRS complex. This study provides a reference for the normal sinus impulse endocardial propagation pattern and for conduction velocities in equine atria and ventricles.

A left bundle branch block activation sequence and ventricular pacing influence voltage amplitudes: an in vivo and in silico study.

The aim of this study was to investigate the influence of the activation sequence on voltage amplitudes by evaluating regional voltage differences during a left bundle branch block (LBBB) activation sequence vs. a normal synchronous activation sequence and by evaluating pacing-induced voltage differences. Twenty-one patients and three computer models without scar were studied. Regional voltage amplitudes were evaluated in nine LBBB patients who underwent endocardial electro-anatomic mapping (EAM). Pacing-induced voltage differences were evaluated in 12 patients who underwent epicardial EAM during intrinsic rhythm and right ventricular (RV) pacing. Three computer models customized for LBBB patients were created. Changes in voltage amplitudes after an LBBB (intrinsic), a normal synchronous, an RV pacing, and a left ventricular pacing activation sequence were assessed in the computer models. Unipolar voltage amplitudes in patients were approximately 4.5 mV (4.4-4.7 mV, ∼33%) lower in the septum when compared with other segments. A normal synchronous activation sequence in the computer models normalized voltage amplitudes in the septum. Pacing-induced differences were larger in electrograms with higher voltage amplitudes during intrinsic rhythm and furthermore larger and more variable at the epicardium [mean absolute difference: 3.6-6.2 mV, 40-53% of intrinsic value; interquartile range (IQR) differences: 53-63% of intrinsic value] compared to the endocardium (mean absolute difference: 3.3-3.8 mV, 28-30% of intrinsic value; IQR differences: 37-40% of intrinsic value). In patients and computer models without scar, lower septal unipolar voltage amplitudes are exclusively associated with an LBBB activation sequence. Pacing substantially affects voltage amplitudes, particularly at the epicardium.

Association of regional myocardial conduction velocity with the distribution of hypoattenuation on contrast-enhanced perfusion computed tomography in patients with postinfarct ventricular tachycardia

Cardiac magnetic resonance imaging has been shown to be beneficial for identification of the ventricular tachycardia (VT) substrate before catheter ablation. Contrast-enhanced perfusion multidetector computed tomography (CEP-MDCT) is more generalizable to clinical practice, and wall thickness and regional hypoenhancement on CEP-MDCT can identify potential substrate sites, albeit with decreased specificity. The purpose of this study was to evaluate the association between wall thickness and attenuation on CEP-MDCT with local conduction velocity (CV) and electrogram abnormalities in patients with postinfarct VT. Fourteen patients with postinfarct VT underwent preprocedural CEP-MDCT followed by endocardial electroanatomic mapping (EAM) and ablation. Myocardial attenuation and wall thickness were calculated from 3-dimensional MDCT images using ADAS-VT software (Galgo Medical). EAM was registered with 3-dimensional MDCT images using the CartoMERGE module of CARTO3 software (Biosense Webster). Local CV was calculated by averaging the velocity between each point and 5 adjacent points with concordant wavefront direction. A total of 3689 points were included. In multivariable regression analysis clustered by patient, local CV was positively associated with myocardial attenuation, bipolar voltage, unipolar voltage, and wall thickness. Each 10-HU drop in full-thickness attenuation correlated to 2.6% decrease in CV (P <.001) and 5.5% decrease in bipolar voltage amplitude (P <.001), after adjusting for wall thickness. Myocardial attenuation distribution on CEP-MDCT is associated with regional CV and electrogram amplitude. Regions with low CV identified with low attenuation on CEP-MDCT may serve as important VT substrates in postinfarct patients.

Evaluation of the Mandibular Incisive Canal by Panoramic Radiography and Cone-Beam Computed Tomography

Background: Radiofrequency ablation (RFA) in Brugada syndrome (BrS) has been performed both endocardially and epicardially. The substrate in BrS is thus unclear. Objectives: To investigate the functional endocardial substrate and its correlation with clinical, electrophysiological and ECG findings in order to guide an endocardial ablation. Methods: Thirteen patients (38.7±12.3 years old) with spontaneous type 1 ECG BrS pattern, inducible VF with programmed ventricular stimulation (PVS) and syncope without prodromes were enrolled. Before to endocardial mapping the patients underwent flecainide testing with the purpose of measuring the greatest ST-segment elevation for to be correlated with the size and location of substrate in the electro-anatomic map. Patients underwent endocardial bipolar and electro-anatomic mapping with the purpose of identify areas of abnormal electrograms (EGMs) as target for RFA and determine the location and size of the substrate. Results: When the greatest ST-segment elevation was in the 3rd intercostal space (ICS), the substrate was located upper in the longitudinal plane of the right ventricular outflow tract (RVOT) and a greatest ST-segment elevation in 4th ICS correspond with a location of substrate in lower region of longitudinal plane of RVOT. A QRS complex widening on its initial and final part, with prolonged transmural and regional depolarization time of RVOT corresponded to the substrate locateded in the anterior-lateral region of RVOT. A QRS complex widening rightwards and only prolonged transmural depolarization time corresponded with a substrate located in the anterior, anterior-septal or septal region of RVOT. RFA of endocardial substrate suppressed the inducibility and ECG BrS pattern during 34.7±15.5 months. After RFA, flecainide testing confirmed elimination of the ECG BrS pattern. Endocardial biopsy showed a correlation between functional and ultrastructural alterations in two patients.

Arterial hypertension drives arrhythmia progression via specific structural remodeling in a porcine model of atrial fibrillation

Arterial hypertension (HT) contributes to progression of atrial fibrillation (AF) via unknown mechanisms. We aimed to characterize electrical and structural changes accounting for increased AF stability in a large animal model of rapid atrial pacing (RAP)-induced AF combined with desoxycorticosterone acetate (DOCA)-induced HT. Eighteen pigs were instrumented with right atrial endocardial pacemaker leads and custom-made pacemakers to induce AF by continuous RAP (600 beats/min). DOCA pellets were subcutaneously implanted in a subgroup of 9 animals (AF+HT group); the other 9 animals served as controls (AF group). Final experiments included electrophysiology studies, endocardial electroanatomic mapping, and high-density mapping with epicardial multielectrode arrays. In addition, 3-dimensional computational modeling was performed. DOCA implantation led to secondary HT (median [interquartile range] aortic pressure 109.9 [100-137] mm Hg in AF+HT vs 82.2 [79-96] mm Hg in AF; P < .05), increased AF stability (55.6% vs 12.5% of animals with AF episodes lasting >1 hour; P < .05), concentric left ventricular hypertrophy, atrial dilatation (119 ± 31 cm2 in AF+HT vs 78 ± 23 cm2 in AF; P<.05), and fibrosis. Collagen accumulation in the AF+HT group was mainly found in non-intermyocyte areas (1.62 ± 0.38 cm3 in AF+HT vs 0.96 ± 0.3 cm3 in AF; P < .05). Left and right atrial effective refractory periods, action potential durations, endo- and epicardial conduction velocities, and measures of AF complexity were comparable between the 2 groups. A 3-dimensional computational model confirmed an increase in AF stability observed in the invivo experiments associated with increased atrial size. In this model of secondary HT, higher AF stability after 2 weeks of RAP is mainly driven by atrial dilatation.