Comparing Non-invasive Inverse Electrocardiography With Invasive Endocardial and Epicardial Electroanatomical Mapping During Sinus Rhythm

This study presents a novel non-invasive equivalent dipole layer (EDL) based inverse electrocardiography (iECG) technique which estimates both endocardial and epicardial ventricular activation sequences. We aimed to quantitatively compare our iECG approach with invasive electro-anatomical mapping (EAM) during sinus rhythm with the objective of enabling functional substrate imaging and sudden cardiac death risk stratification in patients with cardiomyopathy. Thirteen patients (77% males, 48 ± 20 years old) referred for endocardial and epicardial EAM underwent 67-electrode body surface potential mapping and CT imaging. The EDL-based iECG approach was improved by mimicking the effects of the His-Purkinje system on ventricular activation. EAM local activation timing (LAT) maps were compared with iECG-LAT maps using absolute differences and Pearson’s correlation coefficient, reported as mean ± standard deviation [95% confidence interval]. The correlation coefficient between iECG-LAT maps and EAM was 0.54 ± 0.19 [0.49–0.59] for epicardial activation, 0.50 ± 0.27 [0.41–0.58] for right ventricular endocardial activation and 0.44 ± 0.29 [0.32–0.56] for left ventricular endocardial activation. The absolute difference in timing between iECG maps and EAM was 17.4 ± 7.2 ms for epicardial maps, 19.5 ± 7.7 ms for right ventricular endocardial maps, 27.9 ± 8.7 ms for left ventricular endocardial maps. The absolute distance between right ventricular endocardial breakthrough sites was 30 ± 16 mm and 31 ± 17 mm for the left ventricle. The absolute distance for latest epicardial activation was median 12.8 [IQR: 2.9–29.3] mm. This first in-human quantitative comparison of iECG and invasive LAT-maps on both the endocardial and epicardial surface during sinus rhythm showed improved agreement, although with considerable absolute difference and moderate correlation coefficient. Non-invasive iECG requires further refinements to facilitate clinical implementation and risk stratification.

Prolonged Right Ventricular Outflow Tract Endocardial Activation Duration and Presence of Deceleration Zones in Patients With Idiopathic Premature Ventricular Contractions. Association With Low Voltage Areas

Background and AimsThe wavefront propagation velocity in the myocardium with fibrosis is characterized by the presence of deceleration zones and late activated zones, that are absent in the normal myocardium. Our aim was to study the right ventricular outflow tract (RVOT) endocardial activation duration in sinus rhythm, and assess the presence of deceleration zones, in patients with premature ventricular contractions (PVCs) and in controls.MethodsWe studied 29 patients with idiopathic PVCs from the outflow tract, subjected to catheter ablation that had an activation and voltage map of the RVOT in sinus rhythm. A control group of 15 patients without PVCs that underwent ablation of supraventricular arrhythmias was also studied. RVOT endocardial activation duration and number of 10 ms isochrones across the RVOT were assessed. Propagation speed was calculated at the zone with the higher number of isochrones per cm radius. Deceleration zones were defined as zones with >3 isochrones within 1 cm radius. Low voltage areas were defined as areas with local electrogram with amplitude <1.5 mV.ResultsThe two groups did not differ in relation to age, gender or number of points in the map. RVOT endocardial activation duration and number of 10 ms isochrones were higher in the PVC group; 56 (41–66) ms vs. 39 (35–41) ms, p = 0.001 and 5 (4–8) vs. 4 (4–5), p = 0.001. Presence of deceleration zones and low voltage areas were more frequent in the PVC group; 20 (69%) vs. 0 (0%), p < 0.0001 and 21 (72%) vs. 0 (0%), p < 0.0001. The wavefront propagation speed was significantly lower in patients with PVCs than in the control group, 0.35 (0.27–0.40) vs. 0.63 (0.56–0.66) m/s, p < 0.0001. Patients with low voltage areas had longer activation duration 60 (52–67) vs. 36 (32–40) ms, p < 0.0001, more deceleration zones, 20 (95%) vs. 0 (0%), p < 0.0001, and lower wavefront propagation speed, 0.30 (0.26–0.36) vs. 0.54 (0.36–0.66) m/s, p = 0.002, than patients without low voltage areas.ConclusionRight ventricular outflow tract endocardial activation duration was longer, propagation speed was lower and deceleration zones were more frequent in patients with PVCs than in controls and were associated with the presence of low voltage areas.

Characteristics of Macroreentries Using an Epicardial Bypass: Pseudo-Focal Atrial Tachycardia Case Series

Introduction: Human atria comprise distinct epicardial layers, which can bypass endocardial layers and lead to downstream centrifugal propagation at the “epi-endo” connection. We sought to characterize anatomical substrates, electrophysiological properties, and ablation outcomes of “pseudo-focal” atrial tachycardias (ATs), defined as macroreentrant ATs mimicking focal ATs. Methods and Results: We retrospectively analyzed ATs showing centrifugal propagation with post-pacing intervals (PPIs) after entrainment pacing suggestive of a macroreentry. A total of 26 patients had pseudo-focal ATs consisting of 15 perimitral, 7 roof-dependent, and 5 cavotricuspid isthmus (CTI)-dependent flutters. A low-voltage area was consistently found at the collision site and co-localized with epicardial layers like the: (1) coronary sinus-great cardiac vein bundle (22%); (2) vein of Marshall bundle (15%); (3) Bachmann bundle (22%); (4) septopulmonary bundle (15%); (5) fossa ovalis (7%); and (6) low right atrium (19%). The mean missing tachycardia cycle length (TCL) was 67 ± 29 ms (22%) on the endocardial activation map. PPI was 9 [0-15] ms and 10 [0-20] ms longer than TCL at the breakthrough site and the opposite site, respectively. While feasible in 25 pseudo-focal ATs (93%), termination was better achieved by blocking the anatomical isthmus than ablating the breakthrough site [24/26 (92%) vs. 1/6 (17%); p < 0.001]. Conclusion: Perimitral, roof-dependent, and CTI-dependent flutters with centrifugal propagation are favored by a low-voltage area located at well-identified epicardial bundles. Comprehensive entrainment pacing maneuvers are crucial to distinguish pseudo-focal ATs from true focal ATs. Blocking the anatomical isthmus is a better therapeutic option than ablating the breakthrough site.

Prolonged right ventricular outflow tract endocardial activation duration and presence of deceleration zones in patients with idiopathic premature ventricular contractions. Association with low voltage areas

Background and aims: Activation wavefront is rapid and uniform in normal myocardium. Fibrosis is associated with deceleration zones (DZ) and late activated zones. Our aim was to study the right ventricular outflow tract (RVOT) endocardial activation duration (EAD) in sinus rhythm, and assess the presence of DZs, in patients with PVCs and controls. Methods: We studied 29 patients with idiopathic PVCs from the outflow tract, subjected to catheter ablation and an activation and voltage map of the RVOT in sinus rhythm. A control group of 15 patients without PVCs that underwent ablation of supraventricular arrhythmias was also studied. The RVOT EAD and number of 10 ms isochrones were assessed. DZ were defined as a zone with>3 isochrones within 1 cm radius. Low voltage areas (LVA) defined as areas with local electrogram amplitude <1.5mV. Results: The two groups did not differ in relation to age, gender or number of points in the map. EAD and number of 10 ms isochrones were higher in the PVC group; 56 (41-66) ms vs 39 (35-41) ms, p=0.001 and 5 (4-8) vs 4 (4-5), p=0.001. Presence of DZs and LVAs were more frequent in the PVC group; 20 (69%) vs 0 (0%), p<0.0001 and 21 (72%) vs 0 (0%), p<0.0001. Patients with LVAs had longer EAD 60 (52-67) vs 36 (32-40) ms, p<0.0001. Conclusions: EAD was longer and DZs were more frequent in patients with PVCs and were associated with presence of LVAs.

P3756Diverse activation patterns during persistent atrial fibrillation characterised by dipole density non-contact mapping

Background Global simultaneous recording of activation during atrial fibrillation (AF) can elucidate underlying mechanisms contributing to AF maintenance. A better understanding of these mechanisms may allow for a personalised ablation strategy to treat persistent AF. Purpose To characterise left atrial endocardial activation patterns during AF using a novel non-contact dipole density mapping. Methods Activation patterns were characterised into three sub-types: (i) focal with centrifugal activation (FCA); (ii) localised rotational activation (LRA); (iii) localised irregular activation (LIA). Continuous activation patterns were quantified and distributed in the left atrium. Results A total of 144 persistent AF segments with 1068 activation patterns from 25 patients were analysed. The most common pattern was LIA (63%), which consist of four disparate features: slow conduction (45%), pivoting (30%), collision (16%) and acceleration (7%). LRA was the second commonest pattern (20%). FCA (17%) arose frequently from the PVs/ostia. Continuous AF activations comprise multiple combinations of FCA, LRA and LIA, transitioning from one to the next without a discernible order. Preferential conduction areas were typically seen in mid-anterior (48%) and lower-posterior (40%) walls where dominant activations were made up of LRA and LIA. Conclusion AF is characterised by heterogenous activation patterns that vary between individuals. Clinical implications of individualised ablation strategies guided by dipole density mapping will have to be determined. Acknowledgement/Funding None