Identification of Human Ventricular Tachycardia Demarcated by Fixed Lines of Conduction Block in a 3-Dimensional Hyperboloid Circuit.

BACKGROUND: The circuit boundaries for reentrant ventricular tachycardia (VT) have been historically conceptualized within a 2-dimensional (2D) construct, with their fixed or functional nature unresolved. This study aimed to examine the correlation between localized lines of conduction block (LOB) evident during baseline rhythm with lateral isthmus boundaries that 3-dimensionally constrain the VT isthmus as a hyperboloid structure. METHODS: A total of 175 VT activation maps were correlated with isochronal late activation maps during baseline rhythm in 106 patients who underwent catheter ablation for scar-related VT from 3 centers (42% nonischemic cardiomyopathy). An overt LOB was defined by a deceleration zone with split potentials (≥20 ms isoelectric segment) during baseline rhythm. A novel application of pacing within deceleration zone (≥600 ms) was implemented to unmask a concealed LOB not evident during baseline rhythm. LOB identified during baseline rhythm or pacing were correlated with isthmus boundaries during VT. RESULTS: Among 202 deceleration zones analyzed during baseline rhythm, an overt LOB was evident in 47%. When differential pacing was performed in 38 deceleration zones without overt LOB, an underlying concealed LOB was exposed in 84%. In 152 VT activation maps (2D=53, 3-dimensional [3D]=99), 69% of lateral boundaries colocalized with an LOB in 2D activation patterns, and the depth boundary during 3D VT colocalized with an LOB in 79%. In VT circuits with isthmus regions that colocalized with a U-shaped LOB (n=28), the boundary invariably served as both lateral boundaries in 2D and 3D. Overall, 74% of isthmus boundaries were identifiable as fixed LOB during baseline rhythm or differential pacing. CONCLUSIONS: The majority of VT circuit boundaries can be identified as fixed LOB from intrinsic or paced activation during sinus rhythm. Analysis of activation while pacing within the scar substrate is a novel technique that may unmask concealed LOB, previously interpreted to be functional in nature. An LOB from the perspective of a myocardial surface is frequently associated with intramural conduction, supporting the existence of a 3D hyperboloid VT circuit structure. Catheter ablation may be simplified to targeting both sides around an identified LOB during sinus rhythm.

Automated prediction of isthmus areas in scar-related atrial tachycardias using artificial intelligence.

INTRODUCTION: Ablation of scar-related reentrant atrial tachycardia (SRRAT) involves identification and ablation of a critical isthmus. A graph convolutional network (GCN) is a machine learning structure that is well-suited to analyze the irregularly-structured data obtained in mapping procedures and may be used to identify potential isthmuses. METHODS: Electroanatomic maps from 29 SRRATs were collected, and custom electrogram features assessing key tissue and wavefront properties were calculated for each point. Isthmuses were labeled off-line. Training data was used to determine the optimal GCN parameters and train the final model. Putative isthmus points were predicted in the training and test populations and grouped into proposed isthmus areas based on density and distance thresholds. The primary outcome was the distance between the centroids of the true and closest proposed isthmus areas. RESULTS: A total of 193 821 points were collected. Thirty isthmuses were detected in 29 tachycardias among 25 patients (median age 65.0, 5 women). The median (IQR) distance between true and the closest proposed isthmus area centroids was 8.2 (3.5, 14.4) mm in the training and 7.3 (2.8, 16.1) mm in the test group. The mean overlap in areas, measured by the Dice coefficient, was 11.5 ± 3.2% in the training group and 13.9 ± 4.6% in the test group. CONCLUSION: A GCN can be trained to identify isthmus areas in SRRATs and may help identify critical ablation targets.

Peak frequency mapping of atypical atrial flutter.

INTRODUCTION: Peak frequency (PF) mapping is a novel method that may identify critical portions of myocardial substrate supporting reentry. The aim of this study was to describe and evaluate PF mapping combined with omnipolar voltage mapping in the identification of critical isthmuses of left atrial (LA) atypical flutters. METHODS AND RESULTS: LA omnipolar voltage and PF maps were generated in flutter using the Advisor HD-Grid catheter (Abbott) and EnSite Precision Mapping System (Abbott) in 12 patients. Normal voltage was defined as ≥0.5 mV, low-voltage as 0.1-0.5 mV, and scar as <0.1 mV. PF distributions were compared with ANOVA and post hoc Tukey analyses. The 1 cm radius from arrhythmia termination was compared to global myocardium with unpaired t-testing. The mean age was 65.8 ± 9.7 years and 50% of patients were female. Overall, 34 312 points were analyzed. Atypical flutters most frequently involved the mitral isthmus (58%) or anterior wall (25%). Mean PF varied significantly by myocardial voltage: normal (335.5 ± 115.0 Hz), low (274.6 ± 144.0 Hz), and scar (71.6 ± 140.5 Hz) (p < .0001 for all pairwise comparisons). All termination sites resided in low-voltage regions containing intermediate or high PF. Overall, mean voltage in the 1 cm radius from termination was significantly lower than the remaining myocardium (0.58 vs. 0.95 mV, p < .0001) and PF was significantly higher (326.4 vs. 245.1 Hz, p < .0001). CONCLUSION: Low-voltage, high-PF areas may be critical targets during catheter ablation of atypical atrial flutter.

Use of three-dimensional electroanatomic mapping for epicardial access: needle tracking, electrographic characteristics, and clinical application.

AIMS: Pericardiocentesis is usually completed under fluoroscopy. The electroanatomic mapping (EAM) system allows visualizing puncture needle tip (NT) while displaying the electrogram recorded from NT, making it possible to obtain epicardial access (EA) independent of fluoroscopy. This study was designed to establish and validate a technique by which EA is obtained under guidance of three-dimensional (3D) EAM combined with NT electrogram. METHODS AND RESULTS: 3D shell of the heart was generated, and the NT was made trackable in the EAM system. Unipolar NT electrogram was continuously monitored. Penetration into pericardial sac was determined by an increase in NT potential amplitude and an injury current. A long guidewire of which the tip was also visible in the EAM system was advanced to confirm EA. Epicardial access was successfully obtained without complication in 13 pigs and 22 patients. In the animals, NT potential amplitude was 3.2 ± 1.0 mV when it was located in mediastinum, 5.2 ± 1.6 mV when in contact with fibrous pericardium, and 9.8 ± 2.8 mV after penetrating into pericardial sac (all P ≤ 0.001). In human subjects, it measured 1.54 ± 0.40 mV, 3.61 ± 1.08 mV, and 7.15 ± 2.88 mV, respectively (all P < 0.001). Fluoroscopy time decreased in every 4-5 cases (64 ± 15, 23 ± 17, and 0 s for animals 1-4, 5-8, 9-13, respectively, P = 0.01; 44 ± 23, 31 ± 18, 4±7 s for patients 1-7, 8-14, 15-22, respectively, P < 0.001). In five pigs and seven patients, EA was obtained without X-ray exposure. CONCLUSION: By tracking NT in the 3D EAM system and continuously monitoring the NT electrogram, it is feasible and safe to obtain EA with minimum or no fluoroscopic guidance.

Optimizing transseptal puncture guided by three-dimensional mapping: the role of a unipolar electrogram in a needle tip.

AIMS: A three-dimensional electroanatomic mapping system-guided transseptal puncture (3D-TSP), without fluoroscopy or echocardiography, has been only minimally reported. Indications for 3D-TSP remain unclear. Against this background, this study aims to establish a precise technique and create a workflow for validating and selecting eligible patients for fluoroless 3D-TSP. METHODS AND RESULTS: We developed a new methodology for 3D-TSP based on a unipolar electrogram derived from a transseptal needle tip (UEGM tip) in 102 patients (the derivation cohort) with intracardiac echocardiography (ICE) from March 2018 to February 2019. The apparent current of injury (COI) was recorded at the muscular limbus of the foramen ovalis (FO) on the UEGM tip (sinus rhythm: 2.57 ± 0.95 mV, atrial fibrillation: 1.92 ± 0.77 mV), which then disappeared or significantly reduced at the central FO. Changes in the COI, serving as a major criterion to establish a 3D-TSP workflow, proved to be the most valuable indicator for identifying the FO in 99% (101/102) of patients compared with three previous techniques (three minor criteria) of reduction in atrial unipolar or bipolar potential and FO protrusion. A total of 99.9% (1042/1043) patients in the validation cohort underwent successful 3D-TSP through the workflow from March 2019 to July 2023. Intracardiac echocardiography guidance was required for 6.6% (69/1042) of patients. All four criteria were met in 740 patients, resulting in a 100% pure fluoroless 3D-TSP success rate. CONCLUSION: In most patients, fluoroless 3D-TSP was successfully achieved using changes in the COI on the UEGM tip. Patients who met all four criteria were considered suitable for 3D-TSP, while those who met none required ICE guidance.

Histological validation of atrial structural remodelling in patients with atrial fibrillation.

BACKGROUND AND AIMS: This study aimed to histologically validate atrial structural remodelling associated with atrial fibrillation. METHODS AND RESULTS: Patients undergoing atrial fibrillation ablation and endomyocardial atrial biopsy were included (n = 230; 67 ± 12 years old; 69 women). Electroanatomic mapping was performed during right atrial pacing. Voltage at the biopsy site (Vbiopsy), global left atrial voltage (VGLA), and the proportion of points with fractionated electrograms defined as ≥5 deflections in each electrogram (%Fractionated EGM) were evaluated. SCZtotal was calculated as the total width of slow conduction zones, defined as regions with a conduction velocity of <30 cm/s. Histological factors potentially associated with electroanatomic characteristics were evaluated using multiple linear regression analyses. Ultrastructural features and immune cell infiltration were evaluated by electron microscopy and immunohistochemical staining in 33 and 60 patients, respectively. Fibrosis, intercellular space, myofibrillar loss, and myocardial nuclear density were significantly associated with Vbiopsy (P = .014, P < .001, P < .001, and P = .002, respectively) and VGLA (P = .010, P < .001, P = .001, and P < .001, respectively). The intercellular space was associated with the %Fractionated EGM (P = .001). Fibrosis, intercellular space, and myofibrillar loss were associated with SCZtotal (P = .028, P < .001, and P = .015, respectively). Electron microscopy confirmed plasma components and immature collagen fibrils in the increased intercellular space and myofilament lysis in cardiomyocytes, depending on myofibrillar loss. Among the histological factors, the severity of myofibrillar loss was associated with an increase in macrophage infiltration. CONCLUSION: Histological correlates of atrial structural remodelling were fibrosis, increased intercellular space, myofibrillar loss, and decreased nuclear density. Each histological component was defined using electron microscopy and immunohistochemistry studies.

Ripple map delineation of the reentrant circuit in a tricuspid annular atrial tachycardia mimicking focal activity.

A 70-year-old man with hypertensive heart disease underwent catheter ablation of persistent atrial fibrillation. After completing the pulmonary vein isolation, atrial burst pacing induced an annular atrial tachycardia (AT). Overdrive pacing exhibited constant fusion, indicating a macroreentrant mechanism of the AT. However, the CARTO3 activation map created using the Octaray catheter (both Biosense Webster, Irvine, CA) exhibited a centrifugal spread with the earliest activation site at the 4 o'clock position of the tricuspid annulus. In contrast, the Ripple map revealed a clear reentrant circuit with its isthmus located at the 4-6 o'clock position of the tricuspid annulus. The local electrograms in these areas recorded systolic and diastolic potentials simultaneously, and the misannotation of the large far-field potentials caused this discrepant result. Handling low-amplitude complex fractionated electrograms remains a challenge in creating a precise activation mapping. The Ripple map, especially when combined with the Octaray catheter, was effective in dynamically visualizing all these electrograms and accurately delineating the reentrant circuit.

Longitudinal reduction in fluoroscopy with continued use of 3-dimensional electroanatomic mapping systems in catheter ablation of supraventricular tachycardia - then and now.

BACKGROUND: Catheter ablation is a first-line treatment for symptomatic, recurrent supraventricular tachycardia (SVT). This study aims to demonstrate if 3D-electroanatomic mapping (EAM) during SVT ablation reduces fluoroscopy time (FT) and determine if further reductions in FT are observed longitudinally. METHODS: All cases of SVT ablation between May 2011-May 2022 at a single tertiary centre were prospectively recruited. FT between the cohorts with and without EAM were compared. Within the EAM subset, the trend of FT across the years was analysed. RESULTS: There were 1758 cases included, 563 without EAM, 1195 with EAM. EAM was associated with a longer procedure time (mean + 8.8 min, p = 0.001), but with mean reductions in FT and dose area product (DAP) by 19.6 min and 18 621 mGy*cm2 respectively (p < 0.001). There was comparable efficacy without any increase in complication rates. Over time (2011-2022), further reduction in FT of 0.9 min year on year was observed (p = 0.001). Between 2011 and 2017, there was a significant reduction in FT of 1.1 min year on year (p = 0.019), which was not observed from 2017 onwards (p = 0.061). The greatest reduction in FT was after the first year of adoption. CONCLUSION: EAM in SVT ablation reduces fluoroscopy use. FT was initially observed to reduce further over time before plateauing, likely due to increased operator experience. While there is increased interest in zero fluoroscopy SVT ablation, complementary use of fluoroscopy may still be necessary in complex cases.

Three-dimensional-guided and ICE-guided transseptal puncture for cardiac ablations: A propensity score match study.

INTRODUCTION: Transseptal puncture (TSP) is routinely performed for left atrial ablation procedures. The use of a three-dimensional (3D) mapping system or intracardiac echocardiography (ICE) is useful in localizing the fossa ovalis and reducing fluoroscopy use. We aimed to compare the safety and efficacy between 3D mapping system-guided TSP and ICE-guided TSP techniques. METHODS: We conducted a prospective observational study of patients undergoing TSP for left atrial catheter ablation procedures (mostly atrial fibrillation ablation). Propensity scoring was used to match patients undergoing 3D-guided TSP with patients undergoing ICE-guided TSP. Logistic regression was used to compare the clinical data, procedural data, fluoroscopy time, success rate, and complications between the groups. RESULTS: Sixty-five patients underwent 3D-guided TSP, and 151 propensity score-matched patients underwent ICE-guided TSP. The TSP success rate was 100% in both the 3D-guided and ICE-guided groups. Median needle time was 4.00 min (interquartile range [IQR]: 2.57-5.08) in patients with 3D-guided TSP compared to 4.02 min (IQR: 2.83-6.95) in those with ICE-guided TSP (p = .22). Mean fluoroscopy time was 0.2 min (IQR: 0.1-0.4) in patients with 3D-guided TSP compared to 1.2 min (IQR: 0.7-2.2) in those with ICE-guided TSP (p < .001). There were no complications related to TSP in both group. CONCLUSIONS: Three-dimensional mapping-guided TSP is as safe and effective as ICE-guided TSP without additional cost.

Right atrial collision time (RACT): A novel marker of propensity for typical atrial flutter.

INTRODUCTION: The risk of typical atrial flutter (AFL) is increased proportionately to right atrial (RA) size or right atrial scarring that results in reduced conduction velocity. These characteristics result in propagation of a flutter wave by ensuring the macro re-entrant wave front does not meet its refractory tail. The time taken to traverse the circuit would take account of both of these characteristics and may provide a novel marker of propensity to develop AFL. Our goal was to investigate right atrial collision time (RACT) as a marker of existing typical AFL. METHODS: This single-centre, prospective study recruited consecutive typical AFL ablation patients that were in sinus rhythm. Controls were consecutive electrophysiology study patients >18 years of age. While pacing the coronary sinus (CS) ostium at 600 ms, a local activation time map was created to locate the latest collision point on the anterolateral right atrial wall. This RACT is a measure of conduction velocity and distance from CS to a collision point on the lateral right atrial wall. RESULTS: Ninety-eight patients were included in the analysis, 41 with atrial flutter and 57 controls. Patients with atrial flutter were older, 64.7 ± 9.7 versus 52.4 ± 16.8 years (<.001), and more often male (34/41 vs. 31/57 [.003]). The AFL group mean RACT (132.6 ± 17.3 ms) was significantly longer than that of controls (99.1 ± 11.6 ms) (p < .001). A RACT cut-off of 115.5 ms had a sensitivity and specificity of 92.7% and 93.0%, respectively for diagnosis of atrial flutter. A ROC curve indicated an AUC of 0.96 (95% CI: 0.93-1.0, p < .01). CONCLUSION: RACT is a novel and promising marker of propensity for typical AFL. This data will inform larger prospective studies.

Use of Ripple mapping to enhance localization and ablation of outflow tract premature ventricular contractions.

INTRODUCTION: Accurate localization of septal outflow tract premature ventricular contractions (PVCs) is often difficult due to frequent mid-myocardial or protected origin. Compared with traditional activation mapping, CARTO Ripple mapping provides visualization of all captured electrogram data without assignment of a specific local activation time and thus may enhance PVC localization. METHODS: Electroanatomic maps for consecutive catheter ablation procedures for septal outflow tract PVCs (July 2018-December 2020) were analyzed. For each PVC, we identified the earliest local activation point (EA), defined by the point of maximal -dV/dt in a simultaneously recorded unipolar electrogram, and the earliest Ripple signal (ERS), defined as the earliest point at which three grouped simultaneous Ripple bars appeared in late diastole. Immediate success was defined as full suppression of the clinical PVC. RESULTS: Fifty-seven unique PVCs in 55 procedures were included. When ERS and EA were in the same chamber (RV, LV, or CS), the odds ratio for the successful procedure was 13.1 (95% confidence interval [CI] 2.2-79.9, p = .005). Discordance between sites was associated with a higher likelihood of needing multi-site ablation (odds ratio [OR] 7.9 [1.4-4.6; p = .020]). Median EA-ERS distance in successful versus unsuccessful cases was 4.6 mm (interquartile range 2.9-8.5) versus 12.5 mm (7.8-18.5); (p = .020). CONCLUSION: Greater EA-ERS concordance was associated with higher odds of single-site PVC suppression and successful septal outflow tract PVC ablation. Visualization of complex signals via automated Ripple mapping may offer rapid localization information complementary to local activation mapping for PVCs of mid-myocardial origin.

Baseline left atrial low-voltage area predicts recurrence after pulmonary vein isolation: WAVE-MAP AF results.

AIMS: Electro-anatomical mapping may be critical to identify atrial fibrillation (AF) subjects who require substrate modification beyond pulmonary vein isolation (PVI). The objective was to determine correlations between pre-ablation mapping characteristics and 12-month outcomes after a single PVI-only catheter ablation of AF. METHODS AND RESULTS: This study enrolled paroxysmal AF (PAF), early persistent AF (PsAF; 7 days-3 months), and non-early PsAF (>3-12 months) subjects undergoing de novo PVI-only radiofrequency catheter ablation. Sinus rhythm (SR) and AF voltage maps were created with the Advisor HD Grid™ Mapping Catheter, Sensor Enabled™ for each subject, and the presence of low-voltage area (LVA) (low-voltage cutoffs: 0.1-1.5 mV) was investigated. Follow-up visits were at 3, 6, and 12 months, with a 24-h Holter monitor at 12 months. A Cox proportional hazards model identified associations between mapping data and 12-month recurrence after a single PVI procedure. The study enrolled 300 subjects (113 PAF, 86 early PsAF, and 101 non-early PsAF) at 18 centres. At 12 months, 75.5% of subjects were free from AF/atrial flutter (AFL)/atrial tachycardia (AT) recurrence. Univariate analysis found that arrhythmia recurrence did not correlate with AF diagnosis, but LVA was significantly correlated. Low-voltage area (<0.5 mV) >28% of the left atrium in SR [hazard ratio (HR): 4.82, 95% confidence interval (CI): 2.08-11.18; P = 0.0003] and >72% in AF (HR: 5.66, 95% CI: 2.34-13.69; P = 0.0001) was associated with a higher risk of AF/AFL/AT recurrence at 12 months. CONCLUSION: Larger extension of LVA was associated with an increased risk of arrhythmia recurrence. These subjects may benefit from substrate modification beyond PVI.

Coherent mapping of atrial tachycardias in patients with congenital heart disease.

AIMS: Coherent mapping (CM) uses a new algorithm to identify critical conduction isthmuses of atrial tachycardias (ATs). We analysed our experience of ablation of AT in patients with congenital heart disease (CHD) with this new technology. METHODS AND RESULTS: All patients with CHD who had CM of AT using the high-density mapping PENTARAY™ catheter and three-dimensional electroanatomic mapping system Carto3 between June 2019 and June 2021 were included retrospectively (n = 27). As a control group, 27 patients with CHD and mapping of AT without CM between March 2016 and June 2019 were included. In total, 54 ablation procedures were performed in 42 patients [median age 35 (interquartile range, IQR 30-48) years] and 64 ATs were induced and mapped (thereof 50 AT intraatrial re-entrant tachycardia and 14 AT ectopic AT). The median procedure duration was 180 (120-214) min and median fluoroscopy time was 10 (5.2-14) min. Acute success was 100% (27/27) in the Coherence group and 74% (20/27) in the non-Coherence group (P = 0.01). During follow-up [median 26 (12-45) months], AT recurred in 28/54 patients, thereof 15 patients needed a re-ablation procedure. Log-rank test showed no difference in recurrence rate between the two groups (P = 0.29). Three minor complications occurred (5.5%). CONCLUSION: Mapping of AT in patients with CHD using the PENTARAY™ mapping catheter and the CM algorithm led to excellent acute success. All ATs were possible to map and no complications related to the PENTARAY™ mapping catheter were observed. Thus, the use of the CM algorithm represents a promising tool in patients with CHD and complex AT.

Electroanatomic visualization of coronary arteries: a case series to elicit safety, feasibility, and diagnostic value in complex ablation procedures.

AIMS: The goal of this case series was to evaluate the feasibility, safety, and advantages of a wire-based approach for the live visualization of coronary arteries (CAs) in an electroanatomic mapping (EAM) system and to assess its diagnostic information. METHODS AND RESULTS: For this single-centre case series, we included procedures in which close proximity of a possible ablation site to any epicardial vessel was suspected. An uncoated-tip guidewire was introduced into the relevant CAs after exclusion of critical CA stenosis by coronary angiography. By connecting this wire to the EAM system using a clip and pin connection, mapping and live visualization of the wire tip is possible, as well as the assessment of the local electrograms within the respective CAs. Procedural wire insertion and intracoronary mapping was performed by EP specialists and was assisted to judge the relevance of CA disease by an interventional cardiologist. A total of nine procedures in nine patients were included in this case series, four ventricular tachycardia ablation procedures and five procedures for the ablation of premature ventricular contractions. The left CAs were mapped in eight cases and the right CA was mapped in one case. In two cases, epicardial mapping was combined with visualization of the right or left CAs. There were no complications attributed to coronary wiring and mapping in this case. CONCLUSION: We demonstrated the feasibility and safety of CA visualization and integration in an EAM. The live visualization of the CAs added valuable information without the need for preprocedural planning or the purchase of separate software. Electroanatomic visualization was achieved intraprocedurally in a safe and straightforward manner, adding critical diagnostic information without excessive costs or risks.

Wavefront directionality and decremental stimuli synergistically improve identification of ventricular tachycardia substrate: insights from personalized computational heart models.

AIMS: Multiple wavefront pacing (MWP) and decremental pacing (DP) are two electroanatomic mapping (EAM) strategies that have emerged to better characterize the ventricular tachycardia (VT) substrate. The aim of this study was to assess how well MWP, DP, and their combination improve identification of electrophysiological abnormalities on EAM that reflect infarct remodelling and critical VT sites. METHODS AND RESULTS: Forty-eight personalized computational heart models were reconstructed using images from post-infarct patients undergoing VT ablation. Paced rhythms were simulated by delivering an initial (S1) and an extra-stimulus (S2) from one of 100 locations throughout each heart model. For each pacing, unipolar signals were computed along the myocardial surface to simulate substrate EAM. Six EAM features were extracted and compared with the infarct remodelling and critical VT sites. Concordance of S1 EAM features between different maps was lower in hearts with smaller amounts of remodelling. Incorporating S1 EAM features from multiple maps greatly improved the detection of remodelling, especially in hearts with less remodelling. Adding S2 EAM features from multiple maps decreased the number of maps required to achieve the same detection accuracy. S1 EAM features from multiple maps poorly identified critical VT sites. However, combining S1 and S2 EAM features from multiple maps paced near VT circuits greatly improved identification of critical VT sites. CONCLUSION: Electroanatomic mapping with MWP is more advantageous for characterization of substrate in hearts with less remodelling. During substrate EAM, MWP and DP should be combined and delivered from locations proximal to a suspected VT circuit to optimize identification of the critical VT site.

Rapid detection of isthmus block and rhythm change using local electrogram changes during complex atrial flutter ablation.

AIMS: Multiple re-entry circuits may operate simultaneously in the atria in the form of dual loop re-entry using a common isthmus, or multiple re-entrant loops without a common isthmus. When two or more re-entrant circuits coexist, ablation of an individual isthmus may lead to a seamless transition (without significant changes in surface electrocardiogram, coronary sinus activation or tachycardia cycle length) to a second rhythm, and the isthmus block can go unnoticed. METHODS AND RESULTS: We hypothesize and subsequently illustrate in three patient cases, methods to rapidly identify a transition in the rhythm and isthmus block using local electrogram changes at the ablation site. CONCLUSION: Local activation sequence changes, electrogram timing, and the behaviour of pre-existing double potentials can reveal isthmus block promptly when rhythm transitions occur during ablation of multiloop re-entry tachycardias.

Electrographic flow mapping guided catheter ablation offers advantages for patients with persistent atrial fibrillation.

BACKGROUND: Catheter ablation (CA) remains challenging due to suboptimal success rates in persistent atrial fibrillation (AF). Existing mapping technologies cannot reliably distinguish sources in this patient population. Recently, the novel electrographic flow (EGF) mapping system was developed using a modified Horn-Schunk optical flow algorithm to detect and quantify patterns of electrical wavefront propagation in the atria. OBJECTIVES: To test the hypothesis that targeted source ablation based on EGF mapping is superior to empiric AF ablation. METHODS: We included all consecutive patients undergoing EGF guided ablation for persistent AF. All patients underwent pulmonary vein isolation (PVI) and were treated with the same EAM system (CARTO). The outcome of PVI+EGF guided CA was compared with data of PVI-only procedures (PVI-only group) and PVI plus additional empiric adjunctive linear and substrate ablations (PVI+LINES group). 12-months outcome as freedom from AF and atrial tachycardia/flutter (AT/AFL), procedural safety and efficiency characterized by procedure duration, fluoroscopy use, radiofrequency applications and duration, were analyzed. Both intention-to-treat and per protocol analysis were conducted. RESULTS: A total number of 70 patients (39 in PVI+EGF, 16 in PVI-only and 15 patients in PVI+LINES group) were enrolled. Intention-to-treat analysis showed fewer AF recurrences in PVI+EGF as compared with the PVI-only or PVI+LINES groups at 12 months (25.6% vs. 62.5% vs. 53.3%, p = .02). There were no differences in AT/AFL recurrence (17.9% vs. 37.5% vs. 20.0%, p = .37). Procedure times were longer in PVI+EGF group (p < .01), and there were no differences in fluoroscopy use (p = .67). CONCLUSION: Our data suggest that patients treated with EGF-guided CA developed fewer AF recurrences. Although the procedure times are longer, it seems to be safe and offers a more targeted, patient-specific ablation strategy beyond PVI than adjunctive empiric lines and substrate ablation in this complex group of patients.

Open-window mapping for ablation of Wolff-Parkinson-White syndrome related hemodynamically unstable tachycardia.

During catheter ablation (CA) of tachycardia, conventional point-by-point mapping may be hindered due to hemodynamic instability. We performed open-window mapping (CARTO, Biosense Webster, USA) in a patient who developed hemodynamic instability during orthodromic atrioventricular reciprocating tachycardia (AVRT) and unwarranted induction of AVRT during attempts to map accessory pathway (AP) with ventricular pacing. With over 11,000 points acquired rapidly, the system accurately identified AP at the mitral valve (MV) annulus where the application of single radiofrequency (RF) lesion promptly eliminated AP's conduction. Our case illustrates the utility of open-window mapping for the ablation of AVRT.

Uric acid significantly correlates with the presence of low-voltage areas at the endocardial mapping in patients with non-valvular atrial fibrillation.

BACKGROUND AND AIMS: Interest in the role of atrial substrate in maintaining Atrial Fibrillation (AF) is growing. Fibrosis is the culprit in the electrical derangement of the myocytes. Many cardiovascular risk factors are known to be linked to atrial scarring; among them Uric Acid (UA) is emerging. The purpose of our study is to find whether UA is associated with Left Atrium (LA) with pathological substrate. METHODS AND RESULTS: 81 patients who underwent radiofrequency transcatheter ablation for nonvalvular AF at the cardiological department of the Niguarda Hospital were enrolled in an observational, cross-sectional, single-center study. UA levels were analysed before the procedure. High density electroanatomic mapping of the LA was performed and patients were divided according to the presence or not of areas of pathological substrate (bipolar voltage <0.5 mV in sinus rhythm). 19 patients showed a LA with pathological substrate. These subjects showed a significant higher prevalence of persistent phenotype of AF (84.2 vs. 25.8%, p < 0.001). UA levels were significantly higher in the group of patients with LA with pathological substrate (6.8 ± 1.9 vs 5.3 ± 1.4 mg/dL, p < 0.001) as well as the prevalence of hyperuricemia (26.5 vs. 6.5%, p = 0.021). The association between uric acid LA with pathological substrate remains significant even after correction for confounding factors (age, left ventricular dysfunction, valvular disease, arrythmia phenotype and furosemide use) and also when the ratio UA/creatinine was evaluated. CONCLUSIONS: In a population of patients who underwent AF ablation, higher UA levels were significantly associated with pathological LA substrate at electro-anatomical mapping.

To go left or right? Driving towards the best direction in paediatric pacing.

BACKGROUND: Permanent pacing in children with isolated congenital complete atrioventricular block may cause left ventricular dysfunction. To prevent it, alternative pacing sites have been proposed: left ventricular epicardial or selective right ventricular endocardial pacing. AIMS: To compare the functional outcome (left ventricular systolic function and synchrony) in paediatric patients with congenital complete atrioventricular block and left ventricular apical epicardial or right ventricular transvenous mid-septal pacing. METHODS: Retrospective study. Epicardial leads were implanted by standard surgical technique, transvenous leads by 3D electroanatomic mapping systems. 3D mapping acquired 3D right ventricular local pacing map and defined the narrowest paced QRS site. 3D mapping guided screw-in bipolar leads on that ventricular site. Electrocardiogram (ECG) (QRS duration) and echocardiographic data (synchrony: interventricular mechanical delay, septal to posterior wall motion delay, systolic dyssynchrony index; contractility: global longitudinal strain, ejection fraction) were recorded. Data are reported as median [interquartile ranges]. p < 0.05 was significant. RESULTS: There were 19 transvenous systems (age 8.8 [6-14] years; right ventricular mid-septum) and 17 epicardial systems (0.04 [0.001-0.6] years; left ventricular apex). Post-implantation QRS significantly widened either in endocardial or in epicardial patients. Most patients reached 4-year follow-up. One-year and 4-year ejection fraction and global longitudinal strain were mostly within normal limits and did not show significant differences between the two groups and between the same endocardial/epicardial group. Synchrony parameters were within normal limits in the two groups. CONCLUSIONS: Left ventricular apical epicardial pacing and 3D mapping-guided right ventricular mid-septal pacing preserved left ventricular contractility and synchrony in children and adolescents with congenital complete atrioventricular block at short-/mid-term follow-up, without relevant significant differences between the two groups.