Opposite evolution on voltage and thickness from paroxysmal to persistent AF

Background

There is a controversy about correlation between voltage and thickness in the atrial myocardium and their evolution from paroxysmal to persistent atrial fibrillation (AF).

Purpose

This is an observational study to compare voltage and thickness of different areas on the left atrium in paroxysmal and persistent atrial fibrillation.

Methods

Twenty-one patients underwent atrial fibrillation ablation. Points with electrical information from an electroanatiomical map in sinus rhythym were acquiered during the ablation procedure covering the whole atrial surface. CT was acquired in all patients before the procedure and endo- and epicardium from the atrium was segmented for the atrial thickness calculation. All the points from the electromecanical map were projected on the thickness map to have both information on the same location. 3D atrium was segmented in 5 areas for the analysis: Lateral, Anterior, Septal, Inferior-Posterior and Superior-Posterior (Figure 1). Voltage and thickness values among different areas and between AF type were compared.

Results

11 paroxysmal and 10 persistent AF patients were analyzed acquiring 452±207 points per patient and 1897±750 points per area. There was no linear correlation between voltage and thickness comparing all the patients nor among different areas nor between AF type (R<0.2 in all cases).

Regarding paroxysmal AF patients, septum showed significatly lower voltage compared with the other segments, posterior, lateral, anterior and roof (1.3±1.4, 2±1.8, 2±1.6, 1.7±1.5, 2±1.6, P<0.001). Posterior segment showed the highest voltage. The thickness analysis showed the septum segment as thinner segment and lateral as thicker segment (1.3±1.5,1.7±0.8, P<0.001) (Figure 2).

Regarding persisten AF patients: septum showed significatly lower voltage compared with the other segments, posterior, lateral, anterior and roof who shows higher voltage (1±0.8*, 1.5±1.2, 1.9±1.7, 1.5±1.4, 2±1.6) (Figure 2). The thickness analysis showed the anterior segment as thinner segment and lateral as the thickest segment (1.6±0.8, 1.9±0.9 (P<0.001), different like on paroxysmal AF population.

Comparing voltage and thicknes between paroxysmal and persistent AF, all the segments on persistent population showed lower voltage values, with significant differences on septal, posterior and anterior walls (1±0.8 vs 1.3±1.4, 1.5±1.2 vs 2±1.8, 1.5±1.4 vs 1.7±1.5, P<0.001). On the other hand, all segments on persistent population showed statisticaly signignificant thicker myocardium in camparison with paroxysmal population (Figure 2).

Conclusions

According to our findings, there is no linear correlation between voltage and thickness. Persistent AF atria show thicker walls but with lower voltages in comparison with paroxysmal AF atria.

Funding Acknowledgement

Type of funding sources: None.

A novel weighted hybrid clinical and electrocardiographic score to predict the origin of outflow tract ventricular arrhythmias: a multicenter study

Funding Acknowledgements

Type of funding sources: None.

Background

To correctly predict the outflow tract ventricular arrhythmia (OTVA) site of origin (SOO) before the ablation is still a procedural major step, having important implications for correct patient counseling, ablation planning, and periprocedural complication evaluation. Although multiple ECG criteria have been proposed for predicting OTVA SOO, their accuracy and usefulness are still limited as recently (1).

Purpose

The present study sought to prospectively evaluate the accuracy of a previously published Hybrid Score (HS) for prediction of OTVAs with LVOT origin. Besides, multiple ECG measurements of patients with V3 precordial transition (V3PT) OTVA were analyzed to identify potential variables useful to improve the accuracy of the HS (2).

Methods

Consecutive patients (n=105) referred for OTVA ablation were prospectively enrolled from three referral centers. Vascular access and first-mapped ventricle were decided based on the previously published HS, which includes ECG (R/S precordial transition) and clinical information (age, hypertension, and gender). Surface ECGs during the OTVA were analyzed by two independent electrophysiologists to compare the discriminative performance of HS and previous published ECG-alone criteria, to assess their inter-observer variability and to identify potential variables useful to improve the proposed model.

Results

Of the 105 VAs, 70.5% had an RVOT origin and 29.5% an LVOT origin. HS achieved a correct prediction in 90% patients. This rate dropped to 75% in the subgroup of patients with V3PT OTVA. The correct prediction rate of the other ECG-alone criteria in the whole population ranged from 74 to 82% and from 41 to 76% in V3PT patients, and their Cohen’s Kappa coefficient for inter-observer variability assessment ranged from 0.63 to 0.81. R-wave amplitude in V3 was the best ECG parameter for discriminating LVOT origin in V3PT patients. When this parameter was incorporated in the novel Weighted Hybrid Score (WHS) (Figure 1), it correctly classified 99 (94.2%) patients (90% sensitivity, 96% specificity, AUC: 0.97). The WHS discriminatory capacity was maintained in V3PT subgroup, (87% sensitivity, 91% specificity AUC: 0.95). WHS showed a Cohen’s kappa coefficient of 0,82. Finally, WHS was validated in an additional population of 97 patients with OTVAs referred for catheter ablation from three additional external centers; in this testing sample the WHS correctly predicted the SOO in 90% patients and proved to have 89% sensitivity and 90% specificity (AUC: 0.94) for a score ≥2 to predict a LVOT origin.

Conclusions

The novel simple-to-use WHS proved to accurately anticipate the PVC’s SOO and can be introduced in clinical practice for choosing the first chamber to map.

Reproducibility of non-invasive VT substrate characterization: finding the same paths

Background

Delayed enhancement gadolinium MRI is a useful technique to identify myocardial scar. The objective of this study is compare the reproducibility of the scar quantification and characterization based on cardiac MRI.

Methods

10 patients with ischemic ethology underwent to 1,5T DE-MRI acquisition for myocardial scar analysis. Images were processed using a commercial software (ADAS3D-Galgo Medical) and different parameters from scar tissue (mass of the scar, core of scar and border zone expressed in grams) were analysed. Conducting channels evaluation was obtained by the number of corridors and the mass of the border zone of those corridors. To perform this analysis, 2 experienced and 1 non experienced users segmented DE-MRI acquisition in order to evaluate the inter observer variability. Bland-Altman analysis was employed to evaluate the comparison between the measurements.

Results

Inter observer agreement between experienced users was high (table). The mean and the standard deviation of the differences between two measurements for the scar mass was −3,9±14,66 gr. Analysing the scar tissue divided in core and border zone, the mass of these volume tissues were very similar (−3,51±4,56gr and −0,4±12,87gr respectively. Regarding conducting channels characteristics, the mean of the differences was 0±2 for the number of channels and 1,71±7,76 gr for the mass on the border zone of the corridors. Comparing the measurements between one of the experienced users and the beginner user, results were similar but significant differences were found on the mass of the core and the number of channels, with a variability of ±2 channels (table).

Conclusions

Left ventricular scar size and characteristics derived from late gadolinium enhanced post-processed images are highly reproducible between experienced observers.

Funding Acknowledgement

Type of funding sources: None. Table 1Scar analysis performed by 3 users

Safety and Outcomes of Ventricular Tachycardia Substrate Ablation During Sinus Rhythm: A Prospective Multicenter Registry

OBJECTIVES

This study sought to analyze safety and outcomes of ventricular tachycardia (VT) substrate ablation during sinus rhythm (SR), without baseline VT induction.

BACKGROUND

Safety and outcomes after scar-related VT ablation during SR are not well known. Hemodynamic instability and need for electrical cardioversion can compromise safety of VT ablation procedures.

METHODS

Four hundred twelve consecutive patients with structural heart disease undergoing VT ablation were included in a prospective multicenter registry. Substrate ablation during SR, without baseline VT induction, was the first step of the ablation procedure and the standard protocol. Scar dechanneling was the substrate ablation technique used. VT inducibility was tested after substrate ablation.

RESULTS

VT induction protocol was negative after substrate ablation in 289 patients (70.1%), completing the procedure in SR. Procedure-related complication rate was 6.5%, including 1 death (0.2%). Thirty-day mortality after first VT ablation procedure was 1.7%. Overall survival was 95.8% and 88.6% at 1 and 3 years of follow-up, respectively. In a multivariable proportional hazards regression model, age ≥70 years (hazard ratio [HR]: 4.95 [2.59 to 9.47]; p < 0.001), chronic obstructive pulmonary disease (HR: 2.37 [1.24 to 4.52]; p = 0.008), left ventricular ejection fraction <30% (HR: 2.43 [1.37 to 4.33]; p = 0.002), and incomplete substrate ablation (HR: 2.37 [1.24 to 4.52]; p = 0.026) were independent predictors of overall mortality. At 12 months' follow-up, VT-free survival was 82.5% after 1 procedure and 87.8% after n procedures CONCLUSIONS: Substrate ablation during SR avoiding multiple VT induction has low procedure-related complications and low early mortality. Age, chronic obstructive pulmonary disease, and reduced left ventricular ejection fraction, but also incomplete substrate elimination, are predictors of mortality.

Prospective evaluation of a hybrid clinical and electrocardiographic algorithm to predict the origin of outflow tract PVCs. A prospective multicenter study

Funding Acknowledgements

Type of funding sources: Public Institution(s). Main funding source(s): Beca de la Asociación del Ritmo Cardiaco para Formación en Investigación Post-Residencia en centros españoles.

Background

To predict the premature ventricular complex (PVC) site of origin (SOO) before the ablation procedure has important implications. 12 lead ECG information as well clinical characteristics are related with the PVC-SOO, but there is no prospective data validation.

Purpose

This prospective multicenter study sought to analyze the applicability and accuracy of a simple hybrid algorithm that includes electrocardiographic and clinical information in a consecutive patient population with outflow tract (OT) PVCs undergoing catheter ablation.

Methods

Consecutive patients with frequent OT-PVCs and indication for catheter ablation were prospectively included in 4 centers. The vascular access (femoral vein vs femoral artery) and the first outflow tract to be mapped were decided based on a two-steps hybrid algorithm (see Figure 1) including ECG information [R/S PVC precordial transition (PT): early PT if it occurs before V3; late PT if beyond V3) and clinical information [the following variables compute 1 point in a clinical score: age (&gt;59 y.o); presence of hypertension; and gender (man)].

Results

115 consecutive patients [42 (37%) man, 52 + 15 y.o] were included. Mean PVC burden at baseline was 20 ± 13% and mean LVEF was 59 ± 8%. Mean procedure time was 55 ± 26 min. Complete acute abolition of the PVC was achieved in 110 (96%) patients. 84 (73%) patients had the PVC’s SOO in the right ventricle OT (RVOT) whereas 31 (27%) in the left ventricular OT (LVOT). Compared with patients with a RVOT-SOO, those with a LVOT-SOO were more frequently man [18 (58%) vs 24 (29%), p = 0.004], more frequently suffered from hypertension [18 (58%) vs 15 (18%), p &lt; 0.001) and had an early R/S PVC transition [17 (55%) early PT, 3 (10%) late PT) in the case of LVOT-SOO vs 4 (5%) early PT, 55 (65%) late PT in the case of RVOT-SOO, p &lt; 0.001]. The hybrid algorithm accurately anticipated the PVC’s SOO in 101 (88%) patients. A reduction of at least 80% of PVC burden was achieved by 90% of patients at 6 months.

Conclusions

The hybrid algorithm, prospectively evaluated in an international multicenter study, has proved to permit to accurately anticipate the PVC’s SOO (right vs left) in a consultive population of patients with OT PVCs. Abstract Figure 1

Cardiovascular magnetic resonance determinants of ventricular arrhythmic events after myocardial infarction

Funding Acknowledgements

Type of funding sources: None.

Background

 Late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) permits to identify the arrhythmogenic substrate in chronic post-myocardial infarction (MI) patients. It is unknown why a minority of chronic post-MI patients develop sustained ventricular tachycardias (VT) over follow-up, regardless of their left ventricular ejection fraction (LVEF).

Objectives

 To noninvasively characterize scar differences and potential predictors of VT occurrence in chronic post-MI patients.

Methods

 A case-control study was designed through retrospective LGE-CMR data analysis of chronic post-MI patients i) consecutively referred for VT substrate ablation after a first VT episode (n = 66), and ii) from a control group (n = 84) with no arrhythmia evidence. The myocardium was characterized differentiating core, border zone (BZ) and BZ channels (BZC) using the ADAS 3D post-processing imaging platform. Clinical and scar characteristics, including a novel parameter, the BZC mass, were compared between both groups.

Results

 150 post-MI patients were included for analysis. Four multivariate Cox proportional hazards regression models were created for total scar mass (model 1), BZ mass (model 2), core mass (model 3), and BZC mass (model 4, see table). All of them were adjusted by age, sex, and LVEF. In the corresponding models, only total scar mass, BZ mass, core mass, and BZC mass were independent variables associated with the development of VT. BZC mass showed the best performance: a cut-off of 5.15 g identified the cases with 92.4% sensitivity and 86.9% specificity  [AUC 0.93 (0.89–0.97); p &lt; 0.001], with a significant increase in the AUC compared to the other scar parameters (p &lt; 0.001 for all pairwise comparisons using the De Long’s test). By using BZC mass as a risk stratification parameter together with LVEF, the net reclassification improvement (NRI) was 33.3% for the cases, and 39.3% for the controls. The net proportion of patients reclassified correctly was 36.7%

Conclusions

 The mass of BZC, automatically obtained with a commercially available CMR post-processing software, is the strongest independent variable associated with the occurrence of clinical SMVT in post-MI patients after covariate adjustment for age, sex, and LVEF. The measurement of BZC mass could permit a more accurate arrhythmia risk stratification than LVEF in chronic post-MI patients (NRI 36.7%). Scar characteristics analyzed from LGE-CMR imaging should be taken into consideration to better stratify ventricular arrhythmia risk in chronic post-MI patients. Abstract Figure. ROC curves for predicting VT occurrence

P1111Arrhythmogenic substrate detection in ischemic patients undergoing ventricular tachycardia ablation using multi-detector computed tomography: compared evaluation with cardiac magnetic resonance

Background

 Cardiac magnetic resonance (CMR) is capable of accurately identifying arrhythmogenic substrate (AS), leading to longer arrhythmia-free survival when used to guide ventricular tachycardia (VT) substrate ablation procedures. However, the use of CMR may be limited in certain centers or patient subsets. 

Purpose

 To evaluate the performance of multidetector cardiac computed tomography (MDCT) imaging in identifying heterogeneous tissue channels (HTCs) detected by CMR in ischemic patients undergoing VT substrate ablation.

Methods

 Thirty ischemic patients undergoing both CMR and MDCT before VT substrate ablation were included. Using a dedicated post-processing software, two blinded operators, assigned either to CMR or MDCT analysis, characterized the presence of CMR- and CT-channels, respectively. CMR-channels were classified as endocardial (layers &lt;50%), epicardial (layers ≥50%) or transmural. CMR- vs. CT-channel concordance was considered when the orientation was the same and they were located in the same AHA segment.

Results

 Mean age was 69 ± 10 years; 90% were male. Mean left ventricular ejection fraction (LVEF) was 35 ± 10%. All patients had CMR-channels (n = 76), whereas only 26/30 (86.7%) had CT-channels (n = 91). Global sensitivity (Se) and positive predictive values (PPV) for detecting CMR-channels were 61.8% and 51.6%, respectively. MDCT performance improved in patients with epicardial CMR-channels (Se 80.5%), and transmural scars (Se 72.2%). In 4/11 (36%) patients with subendocardial MI, MDCT was unable to identify the AS.

Conclusion

 MDCT fails to detect the presence of AS in 36% of patients with subendocardial MI and shows a modest sensitivity identifying the presence of HTCs, although its performance improves in patients with transmural scar.

Abstract Figure. Multimodality imaging AS detection

P1106Fundamental differences and predictors of scar arrhythmogenicity in ischemic patients using cardiac magnetic resonance: a propensity score-matching study

Introduction

 Late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) permits to identify the arrhythmogenic substrate (AS) in ischemic patients. However, it is unknown why the majority of them never develop ventricular tachycardias (VT), irrespectively of their left ventricular ejection fraction (LVEF). 

Purpose

 To characterize the fundamental differences and potential predictors of scar arrhythmogenicity in post-myocardial infarction (MI) patients with and without VT.

Methods

 36 consecutive ischemic patients with no arrhythmia evidence underwent a LGE-CMR study 4 years after the MI (controls). Scar data were compared with those obtained from 49 ischemic patients referred for VT substrate ablation (cases). Propensity score matching (PSM) was performed to adjust for age, LVEF, scar mass, and time from MI. The myocardium was segmented in 10 layers (endo- to epicardium), characterizing the core, border zone (BZ) and BZ channels (BZCs) using a dedicated post-processing software.

Results

 Compared to controls, cases were significantly older (67.3 ± 9.1 vs. 56.5 ± 11), had lower LVEF (33.1 ± 10.1 vs. 51 ± 9.4), greater scar mass (33.9 ± 17.2 vs. 14.2 ± 11.6 g), BZ mass (21.1 ± 9.9 vs. 9.6 ± 7.6 g), core mas (12.6 ± 8.8 vs. ± g), number of BZC (2.9 ± 1.4 vs. 1.1 ± 1.1) and BZC mass (10.5 ± 4.2 vs. 2.3 ± 2.4 g) (p &lt; 0.001 in all cases). After PSM (2:1) adjustment[BJG1] , cases had more BZCs (2.9 ± 1.4 vs. 2.2 ± 0.6; p = 0.01) and a greater BZC mass (10.5 ± 4.2 vs. 4.6 ± 2.6 g; p &lt; 0.001). In the multivariable logistic regression analysis, the BZC mass was the only independent predictor of being a case [OR 2.3 (1.5–3.4); p &lt; 0.001]. Receiver operating characteristic curve analysis identified a cut-off point of BZC mass &gt;4.28 g (AUC 0.98; p &lt; 0.001), showing 100% sensitivity and 91% specificity for cases’ discrimination.

Conclusions

 Compared with the cases, an otherwise similar control group (PS-matched for age, LVEF, scar mass, and time from MI) showed fewer BZC and a reduced BZC mass. BZC mass was the only independent predictor of being a case. A BZC mass cut-off point of &gt; 4.28 g showed a 100% sensitivity and 91% specificity for the identification of ischemic patients with documented VT.

Abstract Figure. Mean BZC mass and ROC curve analysis

130Long-term outcomes of ventricular tachycardia substrate ablation incorporating hidden slow conduction analysis

Introduction

Ventricular tachycardia substrate ablation (VTSA) incorporating hidden slow conduction (HSC) analysis allows further arrhythmic substrate identification. This study evaluates whether the analysis and elimination of HSC electrograms (HSC-EGMs) during VTSA procedures result in better short and long-term outcomes. 

Methods

Consecutive patients (n = 70, 63% ischaemic, 64 ± 14.6 years) undergoing VTSA were prospectively included. Bipolar EGMs with &gt;3 deflections and duration &lt;133 ms were considered as potential HSC-EGM, if located within/surrounding the scar area. Whenever a potential HSC-EGM was identified, a double ventricular extrastimulus was delivered. If a local potential showed up as a delayed component, it was annotated as HSC-EGM. The incidence of HSC-EGM in core, border-zone, and normal-voltage regions was determined. Ablation was delivered at conducting channel entrances and HSC-EGMs. Procedure time, radiofrequency time, VT inducibility after VTSA and VT recurrence at 12 months after the procedure were compared with data from a historic control group (n = 66, 70% ischaemic, 65.2 ± 12 years).

Results

5076 EGMs were analyzed. 1029 (20.2%) qualified as potential HSC-EGM, and 453 of them were tagged as HSC-EGMs. Scars in patients with HSC-EGMs (n = 43, 61.4%) were smaller (39.66 ± 28.2 vs 69.4 ± 38.2 cm2; p = 0.005) and more heterogeneous (core/scar area ratio 0.24 ± 0.2 vs 0.43 ± 0.17; p = 0.03). 29.6% of HSC-EGMs were located in normal-voltage tissue; 83.5% were targeted for ablation. Patients undergoing VTSA incorporating HSC analysis needed less procedure time (213 ± 75 vs 242 ± 60 min; p = 0.018), less RF time (15.9 ± 10 vs 25 ± 12,7 minutes; p &lt; 0.001), had a lower rate of VT inducibility (27.5% vs 51.5%; p = 0.005) and a higher 2-year VT/VF-free survival (82.8% vs 59.7%; log rank p = 0.047) after VTSA than the historic controls .

Conclusion

VTSA incorporating HSC analysis allowed further arrhythmic substrate identification (especially in normal-voltage areas) and resulted in increased  VTSA efficiency and better short and long-term outcomes.

Abstract Figure. VT Recurrence-Free Survival

125Manual vs. automatic local activation time annotation for guiding premature ventricular complex ablation procedures (MANIaC - PVC study)

Funding Acknowledgements

Financial support was provided in form of a research grant from Biosense Webster

Introduction

 The use of an algorithmic method (wavefront, WF) based on automatic annotation of the maximal negative slope of the unipolar electrogram (uni-EGM) within the window demarcated by the bipolar EGM (bi-EGM) may accurately identify the earliest activation site (EAS) during premature ventricular complex (PVC) ablation procedures.

Purpose

 To assess the potential benefits of a local activation time (LAT) automatic acquisition protocol using WF plus an automatic algorithm for ECG pattern matching recognition (AUT-arm) instead of a manual LAT annotation plus ECG visual inspection (MAN-arm) during premature ventricular complexes (PVCs) ablation procedures.

Methods

 Prospective, randomized, controlled and international multicenter study (NCT03340922). 69 consecutive patients with indication for PVC ablation were enrolled and randomized to AUT (n = 34) or MAN (n = 35) annotation protocols using the CARTO3 navigation system. The primary endpoint was mapping success, defined as complete PVC abolition after a maximum of 2 radiofrequency (RF) applications or up to 90 seconds at the identified EAS, considered the site of origin (SOO). Complete PVC abolition was considered as the procedure success, whereas clinical success was defined as the PVC-burden reduction of &gt;80% in the 24-h Holter at least 1 month after the procedure. Concordance analysis of the maps obtained with both methods was performed.

Results

 Mean age was 69 ± 15, 58% men. The mean baseline PVC burden was 26 ± 13%, mean LVEF 55 ± 12%. Baseline characteristics were similar between groups. The most frequent PVC-SOO were RVOT (41%), LV (25%; being the summit the most frequent location), and LVOT (16%), with no MAN-AUT differences. Total mapping time, number of RF applications, RF time, and procedure time were similar for both groups. The AUT-arm had a higher number of mapping points acquired (164 vs. 61; p = 0.002). There was a delayed detection of LAT at the EAS in the AUT-arm (mean 23 ± 13 ms), being more significant in left-sided PVCs (30 ± 12 vs. 15 ± 9 ms, p &lt; 0.001). The 10-ms isochronal area was significantly bigger in the MAN-arm (1.95 ± 2.7 vs. 1.0 ± 1.0; p = 0.05). The median (interquartile range) distance between AUT-EAS and MAN-EAS was 4 (0–6.8) mm. Mapping success was similar for AUT (65%) and MAN (63%) (p = 1.0). Procedure success was significantly better for the AUT-arm (100% AUT vs. 86% MAN; p = 0.04), but without differences in clinical success (87% AUT vs. 82% MAN; p = 0.7). There were no procedure-related complications.

Conclusions

 The use of a complete automatic protocol for LAT annotation (WF + ECG pattern matching) during PVC ablation procedures is feasible and safe, allowing to achieve equivalent procedural and clinical endpoints as compared to manual procedures carried out by expert operators.

Quantitative Analysis of Electro-Anatomical Maps: Application to an Experimental Model of Left Bundle Branch Block/Cardiac Resynchronization Therapy

Electro-anatomical maps (EAMs) are commonly acquired in clinical routine for guiding ablation therapies. They provide voltage and activation time information on a 3-D anatomical mesh representation, making them useful for analyzing the electrical activation patterns in specific pathologies. However, the variability between the different acquisitions and anatomies hampers the comparison between different maps. This paper presents two contributions for the analysis of electrical patterns in EAM data from biventricular surfaces of cardiac chambers. The first contribution is an integrated automatic 2-D disk representation (2-D bull’s eye plot) of the left ventricle (LV) and right ventricle (RV) obtained with a quasi-conformal mapping from the 3-D EAM meshes, that allows an analysis of cardiac resynchronization therapy (CRT) lead positioning, interpretation of global (total activation time), and local indices (local activation time (LAT), surrogates of conduction velocity, inter-ventricular, and transmural delays) that characterize changes in the electrical activation pattern. The second contribution is a set of indices derived from the electrical activation: speed maps, computed from LAT values, to study the electrical wave propagation, and histograms of isochrones to analyze regional electrical heterogeneities in the ventricles. We have applied the proposed methods to look for the underlying physiological mechanisms of left bundle branch block (LBBB) and CRT, with the goal of optimizing the therapy by improving CRT response. To better illustrate the benefits of the proposed tools, we created a set of synthetically generated and fully controlled activation patterns, where the proposed representation and indices were validated. Then, the proposed analysis tools are used to analyze EAM data from an experimental swine model of induced LBBB with an implanted CRT device. We have analyzed and compared the electrical activation patterns at baseline, LBBB, and CRT stages in four animals: two without any structural disease and two with an induced infarction. By relating the CRT lead location with electrical dyssynchrony, we evaluated current hypotheses about lead placement in CRT and showed that optimal pacing sites should target the RV lead close to the apex and the LV one distant from it.

How to recognize epicardial origin of ventricular tachycardias?

Percutaneous pericardial access for epicardial mapping and ablation of ventricular arrhythmias has expanded considerably in recent years. After its description in patients with Chagas disease, the technique has provided relevant in-formation on the arrhythmia substrate in other cardiomyopathies and has improved the results of ablation procedures in various clinical settings. Electrocardiographic criteria proposed for the recognition of the epicardial origin of ventricular tachycardias are mainly based on analysis of the first QRS components. Ventricular activation at the epicardium has a slow initial component reflecting the transmural activation and influenced by the absence of Purkinje system in the epicardium. Various parameters (pseudodelta wave, intrinsicoid deflection and shortest RS interval) of these initial intervals predict an epicardial origin in patients with scar-related ventricular tachycardias with right bundle branch block morphology. Using the same concept, the maximum deflection index was defined for the location of idiopathic epicardial tachycardias remote from the aortic root. Electrocardiogram criteria based on the morphology of the first component of the QRS (q wave in lead I) have been proposed in patients with nonischemic cardiomyopathy. All these criteria seem to be substrate-specific and have several limitations. Other information, including type of underlying heart disease, previous failed endocardial ablation, and evidence of epicardial scar on magnetic resonance imaging, can help to plan the ablation procedure and decide on an epicardial approach.

CMR-guided approach to localize and ablate gaps in repeat AF ablation procedure

OBJECTIVES

The aim of this study was to test the feasibility and usefulness of a new delayed-enhancement cardiac magnetic resonance (DE-CMR)-guided approach to ablate gaps in redo procedures.

BACKGROUND

Recurrences of atrial fibrillation (AF) after pulmonary vein isolation (PVI) may be related to gaps at the ablation lines. DE-CMR allows identification of radiofrequency lesions and gaps (CMR gaps).

METHODS

Fifteen patients undergoing repeated AF ablations were included (prior procedure was PVI in all patients and roof-line ablation in 8 patients). Pre-procedure 3-dimensional (3D) DE-CMR was performed with a respiratory-navigated (free-breathing) and electrocardiographically gated inversion-recovery gradient-echo sequence (voxel size 1.25 × 1.25 × 2.5 mm). Endocardium and epicardium were manually segmented to create a 3D reconstruction (DE-CMR model). A pixel signal intensity map was projected on the DE-CMR model and color-coded (thresholds 40 ± 5% and 60 ± 5% of maximum intensity). The DE-CMR model was imported into the navigation system to guide the ablation of CMR gaps, with the operator blinded to electrical data. Fifteen conventional procedures were used as controls to compare procedural duration, radiofrequency, and fluoroscopy times.

RESULTS

Fifteen patients (56 pulmonary veins [PVs]; 57 ± 8 years of age; 9 with paroxysmal AF) were analyzed. In total, 67 CMR gaps were identified around PVs (mean 4.47 gaps/patient; median length 13.33 mm/gap) and 9 at roof line. All of the electrically reconnected PVs (87.5%) had CMR gaps. The site of electrical PV reconnection (assessed by circular mapping catheter) matched with a CMR gap in 79% of PVs. CMR-guided ablation led to reisolation of 95.6% of reconnected PVs (median radiofrequency time of 13.3 [interquartile range: 7.5 to 21.7] min/patient) and conduction block through the roof line in all patients (1.4 [interquartile range: 0.7 to 3.1] min/patient). Compared with controls, the CMR-guided approach shortened radiofrequency time (1,441 ± 915 s vs. 930 ± 662 s; p = 0.026) but not the procedural duration or fluoroscopy time.

CONCLUSIONS

DE-CMR can successfully guide repeated PVI procedures by accurately identifying and localizing gaps and may reduce procedural duration and radiofrequency application time.

Epicardial ablation: prevention of phrenic nerve damage by pericardial injection of saline and the use of a steerable sheath

Because of the close proximity of the phrenic nerve to the pericardium, phrenic nerve damage caused by epicardial ablation can easily occur. We report two cases of epicardial VT ablation where pericardial injection of saline, combined with the use of a steerable sheath, successfully prevents the phrenic nerve from being damaged.

Interventional endocardial motion estimation from electroanatomical mapping data: application to scar characterization

Scar presence and its characteristics play a fundamental role in several cardiac pathologies. To accurately define the extent and location of the scar is essential for a successful ventricular tachycardia ablation procedure. Nowadays, a set of widely accepted electrical voltage thresholds applied to local electrograms recorded are used intraoperatively to locate the scar. Information about cardiac mechanics could be considered to characterize tissues with different viability properties. We propose a novel method to estimate endocardial motion from data obtained with an electroanatomical mapping system together with the endocardial geometry segmented from preoperative 3-D magnetic resonance images, using a statistical atlas constructed with bilinear models. The method was validated using synthetic data generated from ultrasound images of nine volunteers and was then applied to seven ventricular tachycardia patients. Maximum bipolar voltages, commonly used to intraoperatively locate scar tissue, were compared to endocardial wall displacement and strain for all the patients. The results show that the proposed method allows endocardial motion and strain estimation and that areas with low-voltage electrograms also present low strain values.