Atrial Wall Research Articles

The critical isthmus of left atrial anterior wall flutter is mostly circumscribed into a small area immediately behind the aortic root. Implications for catheter ablation

Abstract Funding Acknowledgements Type of funding sources: None. Background Left atrial flutters (LAFL) are typically observed in patients with previous ablation lines or surgery in the left atrium (LA). Less frequently, scar-related left atrial anterior wall (LAAW) flutters may occur. Although the presence of low-voltage areas (LVAs, a surrogate of scar) in the LA is considered an arrhythmogenic substrate and a marker of atrial cardiomyopathy, the pathophysiologic factors responsible for its formation remain unclear. We hypothesized that compression of the LAAW by the aortic root could be responsible of LVAs found in the LAAW, and therefore, be the substrate for the development of LAAW flutter. Purpose We aimed to describe: 1) the relationship between the aortic root and the presence of LVAs in the LAAW, which is the substrate for reentry; and 2) the clinical and electrophysiological characteristics of LAAW atrial flutter. Methods Consecutive patients referred for LAFL ablation between April 2019 and September 2022 in a single center were retrospectively collected. Among 55 patients with LAFL, 10 (18%) demonstrated a macroreentrant circuit with a critical isthmus identified in the LAAW, in the absence of previous ablation lines or surgery, and were included in the analysis. Previous pulmonary vein isolation (PVI) was not an exclusion criterion. All patients underwent a multidetector computerized tomography (MDCT) prior to the procedure and the images were analyzed using ADAS 3DTM imaging platform. Activation mapping was performed in all patients using a multielectrode mapping catheter and CARTO 3 navigation system. Results 9 of 10 patients were male (mean age 74,3 ± 6,3 years). LA enlargement was present in all patients (48,3 ± 4,7 mm) and the mean aortic root diameter was 34,8 ± 3,4 mm. The mean LAAW flutter cycle length was 293,4 ± 68,3 ms. In 9 of the patients (90%), the LAAW flutter critical isthmus was just behind the aortic root, separated by < 1 mm according to the LA-aortic root fingerprinted isodistance map (mean fingerprinted isodistance area was 5,8 ± 2,5 cm2). The remaining patient had the critical isthmus just below the aortic root, between the area in contact with the latter and the mitral annulus. Furthermore, in all cases, the critical isthmus was immersed in LVAs. All but 1 LAAW flutter terminated during radiofrequency (RF) energy applications and rendered it non-inducible. After a median follow-up of 13,6 months (IQ range 5,3-21,6), 7 patients (70%) remained without recurrences. Conclusion In patients with LAAW atrial flutter, the presence of LVAs and the critical isthmus of the tachycardia are mostly circumscribed into small areas immediately behind the aortic root. Knowledge of this close relationship and the use of the isodistance map could be useful when mapping and ablating LAAW flutter, helping to straightforward the ablation procedure.

Effect of right and left-sided programmed atrial extrasystoles on conduction across Bachmanns Bundle and initiation of atrial fibrillation

Abstract Funding Acknowledgements Type of funding sources: None. Background Atrial extrasystoles (AES) originating from the pulmonary veins are notorious for triggering episodes of atrial fibrillation (AF). However, non-pulmonary vein triggers, emerging from e.g. the superior vena cava, left atrial posterior free wall, left atrial appendage (LAA), terminal crest and interatrial septum, play also an important role in a significant part of AF patients. AES provoke conduction disorders due to (dispersion in) refractoriness and enhanced non-uniform anisotropy of atrial tissue, which are related to initiation and perpetuation of AF. Bachmann’s bundle (BB) is the main route for interatrial conduction and plays a key role in AF development. However, the exact mechanistic effects of AES on BB in AF initiation are still unknown. Purpose To examine the impact of programmed electrical stimulation (PES) from the left and right atrium on activation and electrophysiological features of BB. Methods Intra-operative high-resolution epicardial mapping of BB was performed during sinus rhythm (SR) in 30 patients (27 male, 64±10 years). PES included a S1 sequence of 400 ms followed by a S2 of 300, 250 and 200 ms provided from the left and right atrial appendage (LAA/RAA). Electrophysiological features included unipolar voltage, conduction velocity, potential type (single, short/long double and fractionated) and conduction delay/block (CDCB). Features of the shortest captured S2 were compared to the S1 sequence. Results The average cycle length during SR was 962 [869–1085] ms. Compared to SR, during S1 pacing from both the RAA and LAA, voltage (RAA: -0.49 [-1.25–0.06] mV; LAA: -0.17 [-0.97–0.42] mV, P<0.001) and conduction velocity (RAA: -2.72 [-6.85–0.36] cm/s; LAA: -1.28 [-12.37–0.85] cm/s, P<0.001) decreased, and the amount of fractionation increased. In addition, CDCB increased specifically during RAA S1 pacing (+1.8 [0.1–3.2]%, P<0.001), while total activation time increased during LAA pacing (+16 [-1–29] ms, P<0.001). Applying the maximal captured S2, 12 patients had a refractory period of 250 ms, 13 patients of 200 ms and 3 patients <200 ms. In 4 patients, AF was induced by a S2 of 250 or 200 ms from either RAA or LAA. During both RAA and LAA S2 pacing, voltage (RAA: -1.33 [-2.51–-0.64] mV; LAA: -0.91 [-1.64–-0.46] mV, P<0.001) and conduction velocity (RAA: -16.34 [-24.49–-6.70] cm/s; LAA: -8.63 [-19.95–-1.25] cm/s, P<0.001) decreased, while total activation time (RAA: +26 [11–59] ms; LAA: +21 [2–46] ms, P<0.001) and CDCB (RAA: +5.7 [3.5–11.7] %; LAA: +4.1 [0.4–6.5] %, P<0.001) increased. Specifically, the average length of CDCB lines increased remarkably during LAA S2 pacing (+22 [8–39] mm, P<0.001) and even more during RAA S2 pacing (+36 [19–80] mm, P<0.001). Conclusions Premature AES affect interatrial conduction via BB by enhancing conduction disorders. This indicates that BB is involved in AF initiation by ectopic beats, independently of their origin from the right or left atrium.

Determinants of left atrial local impedance: relationships with contact force, atrial fibrosis and rhythm

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Boston Scientific Background The relationships between baseline tissue local impedance (LI), contact force (CF), atrial fibrosis and atrial rhythm are uninvestigated in a clinical setting. Objectives To compare the relationship of LI and CF between atrial fibrillation (AF) and sinus rhythm (SR). Establish the effects of atrial fibrosis as assessed by bipolar voltage and LI. Methods Patients undergoing persistent AF ablation were recruited. The ablation catheter was placed against the left atrial wall and CF levels varied from 1-40g. LI was recorded concurrent to changes in CF at these locations, with data collected at the same locations in AF and SR following DC cardioversion. LI values were referenced to patient blood pool, (LIr). Results 20 patients were recruited. 109 locations were sampled obtaining 1903 datapoints (SR: 966, AF: 937). CF correlated strongly with LI (repeated measures correlation = 0.64). The relationship between CF and LIr was logarithmic. Rhythm and CF had a significant main (both p < 0.0005) and interaction effect (p = 0.022) on tissue LI: AF demonstrated higher LIr values than SR for similar CF (Figure 1). Furthermore, AF modelled a more predictable relationship between CF and LI than SR (R2 = 0.21 vs 0.13). Bipolar voltage had no effect on the relationship of CF to LIr in either rhythm when using conventional cut-offs to determine scar (0.05mV and 0.5mV). Cut-offs for assessing scar using LIr used values of 0.5Ω and 10.5Ω based on concurrent work. Through assessing fibrosis using these values, LIr showed an interaction effect with CF for LIr in SR and AF, (SR: p <0.0005, AF: p = 0.01), with more fibrosis demonstrating shallower CF-LIr curves than healthier tissue, (Figure 2). Conclusions CF and rhythm significantly affect the measured LIr of LA myocardium. Optimal catheter-tissue coupling may be better achieved with higher levels of CF and in AF rather than SR. Atrial fibrosis as assessed by bipolar voltage did not affect the CF-LI relationship, but was when assessed by LIr.

Dielectric response in relation to other ablation parameters

Abstract Funding Acknowledgements Type of funding sources: None. Background Dielectric imaging is used by the KODEX-EPD system to provide information that can be used to guide catheter ablation of cardiac arrhythmia. This includes assessment of catheter-tissue contact (No touch, Touch, or High touch) and local atrial wall thickness (mm). Additionally, the system can detect changes in local dielectric tissue properties to assess the effect of a radiofrequency energy application. This assessment is used to classify ablation points into low or high dielectric response (LDR or HDR), which was designed to indicate the extent of lesion transmurality. Objectives To evaluate the relation between dielectric response and other ablation parameters. Methods The KODEX-EPD system was used to guide ablation in patients with prior pulmonary vein isolation. Ablation included re-isolation of the pulmonary veins and isolation of the superior vena cava if deemed necessary. We downloaded system data from all procedures that were performed with software that provided dielectric response (version 1.5.0, 1.5.0a, 1.5.1 and 1.5.1a) and analyzed the parameters of all individual ablation points. Results The cohort includes 55 patients, in which 135 pulmonary veins and 19 superior venae cavae were targeted. A total of 860 energy applications were applied, resulting in 1458 ablation points. The system classified 31% of ablation points as HDR and 19% as LDR. The system did not provide a dielectric response in 49%. The system’s ability to determine dielectric response was related to the software version(oldest version 71% no DR, newest version 18%) and duration of ablation. High dielectric response (versus LDR or no DR) was multivariably associated with longer energy applications, higher mean ablation power and lower local wall thickness (Table). Mean ablation temperature and impedance drop were not multivariably associated with dielectric response. Conclusion Dielectric response is independently associated with local wall thickness, ablation power and duration, but not with ablation temperature and impedance drop. Newer software versions have reduced the proportion of ablation points for which no dielectric response was provided.

Impact of ultra-short pauses between stacked lesions with and without active esophageal cooling

Abstract Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Research reported in this abstract was supported by the National Heart, Lung, And Blood Institute of the National Institutes of Health under Award Number R44HL158375 (the content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health). Background Placing lesions at the same point (stacking lesions) in the left atrium during radiofrequency (RF) ablation can increase the risk of collateral injury. The use of active esophageal cooling has been shown to significantly reduce the risk of thermal injury to the esophagus, but stacking of lesions may overcome these protective effects. Longer pauses between lesions may reduce this risk, but the effect of very short pauses has not been previously quantified. Purpose To examine the impact of ultra-short pauses between stacked lesions with and without active esophageal cooling. Methods Using a computational model of the left atrium, we measured the effect of RF ablation in the left atrium on injury formation in the esophagus. Models with and without active esophageal cooling, using a dedicated esophageal cooling device, were created. Using a power of 50 W for 10 s, with up to 3 sequential lesions placed in the same location, we used the Arrhenius equation to quantify the fraction of damage (FOD) in the esophageal wall. The time between lesions was set to as short as 1 s, and results were compared to prior studies using longer pauses of up to 20 s. To account for thermal latency, measures of esophageal damage were taken both immediately after RF ablation, and again 90 s afterwards. Results With active cooling in place, esophageal injury was eliminated with active esophageal cooling after the first lesion placement, but reached 21% transmurality without cooling. Lesion transmurality increased after each lesion due to thermal latency, but active esophageal cooling prevented this effect when only one lesion was placed. Subsequent lesions resulted in esophageal injury when placed in the same location. After 3 lesions with 1 s pauses between each, esophageal injury transmurality reached 91% without cooling in place, and 22% with active cooling in place (Figure 1). In contrast, analysis of the intended lesions in the atrial wall demonstrated minimal effects from cooling (Figure 2). Conclusions Active esophageal cooling significantly reduces esophageal injury from RF ablation, but placing additional lesions at the same point can overcome the heat extraction capacity of a dedicated cooling device. Decreased time between lesions exacerbates this risk, with an ultra-short pause of one second posing the greatest risk.

Causes for recurrence after personalized radiofrequency catheter ablation for paroxysmal atrial fibrillation and pulmonary vein reconnection site characteristics

Abstract Funding Acknowledgements Type of funding sources: None. Background Personalized pulmonary vein isolation (PVI) for paroxysmal atrial fibrillation (PAF), tailoring the ablation index (AI) to the left atrial wall thickness (LAWT), has proven to be a highly efficient method with excellent arrhythmia free survival rates. However, the number and location of pulmonary vein (PV) reconnection sites in patients with arrhythmic recurrences after personalized PVI is not known. Purpose We aimed to analyze the PV reconnection sites and the probable causes responsible for these PV reconnections during REDO procedures after personalized atrial fibrillation (AF) ablation. Methods Consecutive patients referred for a REDO procedure, after a personalized ablation protocol for PAF, were included in the analysis. During the index procedure and using ADAS 3DTM imaging platform for segmentation, the LAWT maps were obtained from multidetector computerized tomography (MDCT) and, thereafter, imported into CARTO 3 navigation system. If reconnection of a PV was confirmed, the LAWT of the reconnection site was analyzed. Patients who lost follow-up were excluded. Results Among 251 consecutive patients who underwent personalized PVI from April 2019 to July 2021, 45 (17,9%) had recurrence of atrial tachyarrhythmias after a mean follow-up of 1,4 ± 0,8 years. Of them, 28 underwent a REDO AF ablation procedure. 26 patients (93%) had PV reconnections [17 (60%) had both right and left reconnected PVs, 5 (18%) isolated right PV reconnection and 4 (14%) isolated left PV reconnection]. Overall, there were 76 reconnection points (40 in right PVs and 36 in left PVs). Mean LAWT in right and left PV reconnection sites was 2 ± 0,8 mm and 3,1 ± 1,2 mm, respectively. Most frequent sites of PV reconnections were anterosuperior and anterior carina for RPV (accounting for 55% of reconnection points) and anterosuperior, anterior ridge and anteroinferior for LPV (75%). Only 2 PV reconnections (3%) occurred in areas with LAWT < 1 mm. Analyzing the possible causes for PV reconnections, we found a causal relationship in 20 reconnected points (26%): gaps in the ablation line (distance between two adjacent VISITAG™ > 6 mm) in 5, lower ablation index than pre-specified in the personalized ablation protocol at a given point in 15, and absence of right carina ablation line in 5 cases. Catheter instability and misinterpretation of the color-coded LAWT were the main causes of these suboptimal (under target RF dosing) ablation lesions. Conversely, among 6 patients with no gaps and optimal ablation lesions according to the pre-specified protocol, only 1 had PVs isolated during the REDO procedure. Conclusion Most of the patients with AF recurrence after a personalized AF ablation had PV reconnections. Reconnection points were more frequently present in thicker segments of both PVs. GAPS in the ablation line, suboptimal ablation lesions and catheter instability are associated with PV reconnections.

Volumetric quantification of peri-atrial fat inflammation in atrial fibrillation patients

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): British Heart Foundation Centre for Research Excellence Award III (RE/18/5/34216). SEW is supported by the British Heart Foundation (FS/20/26/34952). MCW is supported by the British Heart Foundation (FS/ICRF/20/26002) Introduction Peri-atrial fat may have pro-inflammatory and pro-fibrotic effects on atrial myocardium and increase the risk of developing atrial fibrillation. Both peri-atrial fat volume and density have been proposed as markers for atrial fibrillation risk, but prior studies considered only single-plane analysis or peri-atrial fat attenuation limited to the posterior left atrium. Purpose We aimed to assess total peri-atrial fat volume and attenuation and to explore the relationship between both parameters and the occurrence of atrial fibrillation. Methods Contrast-enhanced cardiac computed tomography (CT) imaging was performed pre-ablation in atrial fibrillation patients (n=32) and in control patients (n=37) without atrial fibrillation undergoing investigation for chest pain. We developed a volumetric method for peri-atrial fat segmentation and quantification using seg3D2 and CEMRGapp. Peri-atrial fat volume and attenuation (Hounsfield units, HU) were compared between patients with and without atrial fibrillation in univariable and multivariable analyses. A sensitivity analysis was performed to assess the impact of fat proximity to the left atrial wall. Results Atrial fibrillation participants were older (64±11 years vs 58±7 years, P=0.004) and more likely to have a history of coronary artery disease (50% vs 25%, P=0.03). Participants with atrial fibrillation had greater left atrial volume (88±28 ml vs 69±19 ml, P=0.002) and mass (29±6 g vs 14±0.9 g, P=0.018) compared to controls. Peri-atrial fat volume was greater in those with than without atrial fibrillation (18.5±6.6 ml vs 14.2±7.0 ml, adjusted odds ratio (AOR) per ml 1.21; 95% confidence interval [CI] 1.03-1.48), after adjusting for age, body mass index, comorbidities, left atrial dimensions and mass. However, total peri-atrial fat attenuation was not significantly different between groups (-74.8 vs -73.0 HU; AOR per HU 1.01; 95% CI 0.82-1.22). Sensitivity analysis did not identify an interaction between interrogation distance from the left atrial wall and peri-atrial fat attenuation on prevalent atrial fibrillation (p=0.872). Conclusion Peri-atrial fat volume, but not attenuation, is associated with prevalent atrial fibrillation. Further mechanistic studies are needed to study the role of peri-atrial fat in atrial fibrillation pathogenesis.

Using computed tomogram atrial myocardial thickness maps in high-power short-duration radiofrequency pulmonary vein isolation: a prospective randomized clinical study

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by a grant [HI21C0011] from the Ministry of Health and Welfare, a grant [NRF-2020R1A2B5B01001695] from the Basic Science Research Program run by the National Research Foundation of Korea (NRF) which is funded by the Ministry of Science, ICT & Future Planning (MSIP), and a grant [RS-2022-00141473] from Cross-ministerial tasks. Background High-power short-duration (HPSD) ablation generates wide and contiguous but shallow lesions by radiofrequency (RF) resistive heating. It is unknown whether RF energy titration has additional benefits depending on the atrial wall thickness. Purpose We aimed to compare the efficacy and safety of HPSD energy titration depending on left atrial wall thickness (LAWT) during circumferential pulmonary vein isolation (CPVI) in patients with paroxysmal atrial fibrillation (PAF). Methods We prospectively randomized 224 patients with PAF (69.2% males, 59.3±12.0-years-old) into either the LAWT-guided CPVI group (WT, n=113) or the conventional CPVI group (Control, n=111). We delivered 15s of constant RF (contiguous lesion 2mm dots, FlexAbility) at 60W in the Control group but titrated the RF duration in the WT group (15 s at LAWT>2.1mm, 13s at 1.4–2.1mm, and 11s at <1.4mm) referencing the computed tomogram-myocardial thickness color map. The primary endpoints were safety and AF recurrence after a single procedure; the secondary endpoints were the procedure time, cardioversion rate, and response to anti-arrhythmic drugs (AADs). Results After a mean follow-up of 13.4±7.0 months, the clinical recurrence rate (13.3% vs. 8.1%, log-rank p=0.302) and the complication rate (8.0% vs. 4.5%, p=0.427) did not differ between the two groups. The total procedure time (p=0.391) and cardioversion rate (p=1.000) did not significantly differ between the two groups. During the final follow-up, sinus rhythm was maintained without AADs in 72.6% of the WT group and 80.2% of the Control group (p=0.237). Conclusions LAWT-guided energy titration resulted in efficacy and safety equivalent to that of constant 15s 60W-HPSD CPVI in patients with PAF.

Multidetector computed tomography-derived left atrial wall thickness maps of patients undergoing persistent atrial fibrillation ablation

Abstract Funding Acknowledgements Type of funding sources: None. Background Pulmonary vein isolation (PVI) has proven to be effective in treating persistent atrial fibrillation (PeAF), although long-term ablation outcomes have been significantly less favorable than in paroxysmal AF. Purpose We sought to analyze multidetector computed tomography (MDCT)-derived left atrial wall thickness (LAWT) maps of patients undergoing PeAF radiofrequency ablation with a personalized approach aimed for adapting the ablation index (AI) of contiguous lesions to the local LAWT. Methods PeAF was defined in the presence of at least one AF episode sustained beyond 7 days, long-standing PeAF was defined as continuous AF of >12 months duration when decided to adopt a rhythm control strategy. For each patient included in the analysis, LAWT three-dimensional map were obtained from MDCT. LAWT was categorized into 1 mm layers and AI was titrated according to the LAWT. Results One hundred twenty-one patients (79.4% male, age 64.5±9.5 years) were included. Procedure time was 67 minutes (IQR 50-67), fluoroscopy time was 43 seconds (IQR 20-71), and radiofrequency time was 16.5 minutes (IQR 14.3-18.4). LAWT of the circumferential PV line was thicker in the LPVs as compared to the RPVs (1.64 mm [1.5-1.81] vs. 1.29 mm [1.16-1.57], p<0.01). More specifically, anterior wall segments were thicker in the LPVs as compared to the RPVs (2.1 mm [1.9-2.4] vs. 1.4 mm [1.1-1.9], p<0.01), while posterior wall segments had similar WT. Ablation index applied according to local LAWT was 387 (IQR 360-410) for the anterior wall and 335 (IQR 300-375) for the posterior wall. Overall first pass rate was 73.6%; median LAWT values were higher for PVs with no first pass during radiofrequency ablation with respect to the whole cohort (1.73 mm [1.57-1.98] vs. 1.64 mm [1.50-1.81] p=0.02 for LPVs; 1.46 mm [1.21-1.65] vs. 1.29 mm [1.16-1.57] p=0.03, for RPVs). LAWT values for each PV segment are represented in Figure 1. At a 12 months of follow-up the rate of recurrence-free survival was 79%. Recurrence-free survival rate was significantly higher in patients with PeAF with respect to those with long-standing PeAF diagnosis (p=0.044). A second ablation was performed in 18 patients out of those with AT/AF recurrence. Median LAWT values were higher for PVs with reconnection found in the redo procedures comparing to the median LAWT of the corresponding PVs of the whole cohort (1.77 mm [1.65-2.14] vs. 1.64 mm [1.50-1.81] p=0.01 for LPVs; 1.43 mm [1.25-1.61] vs. 1.29 mm [1.16-1.57] p=0.05, for RPVs). Methods and results are summarized in Figure 2. Conclusion This proof-of-concept study proves that personalized local LAWT-guided PVI ablation for PeAF is efficient and have good long-term outcomes. No first-pass segments during first procedure and reconnection sites within redo procedures were mostly found in thickest regions. A randomized trial comparing the LAWT-guided PVI with the standard of practice is in progress.

Percutaneous management of atrial wall perforation during transeptal puncture with an Amplatzer vascular plug in 3 patients: keep calm, think fast

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Atrial wall perforation is a rare but serious complication of transeptal puncture in AF catheter ablation procedure. In patients with uninterrupted anticoagulation associated to non-fractionated heparin bolus this may lead to cardiac tamponade and dramatic consequences. Urgent surgical drainage and repair is mandatory in the most dramatic cases. We report the successful closure of such complication by an Amplatzer vascular plug leading to a rapid and total recovery in 3 patients. Methods Three patients (male, 43, 77 and 84 yo) referred for persistent atrial fibrillation ablation (1 RF and 2 cryoablations). After transeptal puncture, they became severely hypotensive with echographic evidence of tamponade. Results Heart perforation with massive leakage of contrast in the pericardial space was evident. The perforation was anterior near aorta in one, on the posterior wall of the right atrium in one and on the posterior wall of the left atria though the right atria in one. After heparin antagonization by protamin, the pericardial space was drained percutaneously (1 to 3 l drained and in 1 reinjected through a "cell saver" system). Rapidly, a 0,035 J guide wire was passed through the perforation and an Amplatzer vascular Plug 2 (4 mm in 2 patients and 6 mm in one) was released resulting in an immediate closure of the leak and recovery of the patient after completion of the pericardial drainage. The drainage was monitored 24h and patients were discharged on Day 2 with a good evolution over a median follow-up of 1.5 year. CT scan at 3 and 6 month showed total recovery. Conclusion In patients with left atrial wall perforation and tamponade related to failed transeptal puncture in patients under uninterrupted oral anticoagulation for AF ablation, rapid release of a closure device and pericardial evacuation allowed to successfully manage the cardiac tamponade and avoid a surgical option.

Mitral annular disjunction prevalence and its association with ventricular arrythmias in Upper Egypt

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Mitral annular disjunction (MAD) was first described more than 3 decades ago as an abnormal atrial displacement of the hinge point of the mitral valve away from the ventricular myocardium. MAD was associated with ventricular arrythmias and sudden cardiac death, yet some studies suggested that the presence of MAD can be potentially normal physiological function . (1) Purpose Our primary end point was assessment of the incidence of mitral annular disjunction among the cohort of mitral valve prolapse at our center and the secondary end point was the incidence and predictors of ventricular arrythmias(VAs) in our cohort. Methods It is an observational cross section study where we recruited all the patients who were diagnosed to have MAD at our center representing the area of Upper Egypt, MAD was defined as distinct separation of the mitral valve annulus and the left atrial wall and myocardial continuum, and it was initially diagnosed by the means of transthoracic echocardiography. All patients’ demographics and family history (FH) of sudden cardiac death (SCD) were collected,symptoms were assessed as regard palpitations, shortness of breathing, chest pain, pre syncope and syncope, data from echocardiography including LV internal dimensions, leaflets affection, degree of mitral regurgitation, careful ECG analysis was done extracting the data for PR interval, corrected QTc, T wave inversion, PVCs in surface ECG and in 24 hours Holter, cardiac MRI parameters including late gadolinium enhancement, its distribution and systolic curling. Results We analyzed the data of 300 patients with mitral valve prolapse, 7 % of them showed mitral annular disjunction, 33 % of the cohort were female patients, the mean age was 34 years old, the mean follow up period was 3 years, main presenting complain was palpitations with an incidence of 66 %, FH of SCD was noticed in 9 % of our cohort, Mean QRS width was 81 mseconds, mean QTc was 423 mseconds, the mean EF was 60 %, mean displacement distance was 3 mm, while the mean LA volume was 36 cm3, 80 % of the cohort showed bileaflet affection, while only 19 % of them had late gadolinium enhancement, 50 % of them had fibrosis in the papillary muscles, while systolic curling was noticed in only 9 %.VAs were defined as having premature ventricular complexes in the surface ECG or documented monomorphic ventricular tachycardia and it was noticed in 19 % of our cohort with an average burden of 10 % during a 24 hours Holter.There was a positive correlation between the FH of SCD and the Prescence of PVCs in surface ECG with a significant P value of 0.02, while there was no correlation between fibrosis and the incidence of ventricular arrythmias. Conclusions Incidence of MAD was 7 % among the MVP population at our center. Only FH of SCD was a predictor of the incidence of VAs, while ECG, echo and cardiac MRI parameters couldn`t be proved to be positively correlated with the VAs.

Preclinical safety and biodistribution assessment of Ad-KCNH2-G628S administered via atrial painting in New Zealand white rabbits.

Post-operative atrial fibrillation (POAF) is the most common complication after cardiac surgery. Despite implementation of several pharmacological strategies, incidence of POAF remains at approximately 30%. An adenovirus vector encoding KCNH2-G628S has proven efficacious in a porcine model of AF. In this preclinical study, 1.5 × 1010 or 1.5 × 1012 Ad-KCNH2-G628S vector particles (vp) were applied to the atrial epicardium or 1.5 × 1012 vp were applied to the whole epicardial surface of New Zealand White rabbits. Saline and vector vehicle served as procedure controls. Animals were followed for up to 42 days. Vector genomes persisted in the atria up to 42 days, with no distribution to extra-thoracic organs. There were no adverse effects attributable to test article on standard toxicological endpoints or on blood pressure, left atrial or ventricular ejection fractions, electrocardiographic parameters, or serum IL-6 or troponin concentrations. Mononuclear infiltration of the myocardium of the atrial free walls of low-dose, but not high-dose animals was observed at 7 and 21 days, but these changes did not persist or affect cardiac function. After scaling for heart size, results indicate the test article is safe at doses up to 25 times the maximum proposed for the human clinical trial.

C18 A FISTULA BETWEEN LVOT AND LEFT ATRIUM: AN UNKNOWN ORIGIN

Abstract History of presentation A 76–year–old woman presented to our EchoLab for worsening exertional dyspnea. Few weeks prior the patient underwent cardiological examination that showed heart failure with preserved ejection fraction (HFpEF) with bilateral pleuric effusion, severe mitralic regurgitation (MR), moderate tricuspid regurgitation (TR) with an estimated systolic pulmonary artery pressure (sPAP) of 50 mmHg and a mildly increased mean gradient on bioprothesic aortic valve (26 mmHg). Past medical history The patient had a medical history significant for arterial hypertension, hyperlipidemia, diabetes mellitus, permanent atrial fibrillation and HCV–related liver disease. She received double surgical aortic valve replacement in 2015 and 2019, the second procedure was complicated by intraoperatory stretching of mitral anterior leaflet and atrioventricular block treated with implantation of bicameral PMK. In the following weeks, the patient was admitted to hospital for exposure of the PMK generator pocket associated to catether cultures positivity for S. Aureus oxacilline–resistant, thus undergoing to device removal and positioning of a new PMK. Investigations The cardio–thoracic auscultation revealed a bilateral basal reduction of vesicular breath sounds, an apical sweet systolic murmur (suggestive of MR) and a systolic small aortic murmur best heard at the second intercostal space. The transthoracic echocardiography showed a blood flow apparently originating from interatrial septum heading towards the free left atrial wall. The Transoesophageal Echocardiography (TEE) with bubble test ruled out any interatrial communication. The 3D TEE acquisitions clarified that the shunt arose from the left ventricular outflow tract (LVOT), thus allowing the diagnosis of fistula between the LVOT and the left atrium. Follow–up and conclusions The patient underwent a procedure of percutaneous closure of the fistula. One month after this intervention, the patient presented to our department for the cardiological follow–up. We noticed that the closure had been successful with no left residual shunts and a reduction of the transprothesic mean aortic gradient (18 mmHg). This case report highlights the importance of the 3D echocardiography in order to settle uncertain diagnostics whereas the 2D echocardiography alone is not sufficient. Nevertheless, the diagnostic challenge that remains open is to understand whether the etiology of the fistula is iatrogenic or post–infectious.

P61 VIP–AF. CORRELATION BETWEEN VOLTAGE AND IMPEDANCE MAPPING IN PATIENTS AFFECTED BY ATRIAL FIBRILLATION: A FURTHER STEP TOWARDS SUBSTRATE CHARACTERIZATION

Abstract Background Pulmonary veins isolation (PVI) represents the main strategy for paroxysmal atrial fibrillation (AF) treatment. Due to the poor clinical outcomes of PVI in case of non–paroxysmal AF, significant efforts have been made to develop new ablative strategies to modify the atrial substrate. Up to now, in order to characterise atrial substrate, only bipolar voltage maps have been used and impedance mapping has never been evaluated. Purpose Our aim is to demonstrate the potential correspondence among atrial wall thickness, bipolar voltage and impedance. Atrial impedance mapping could represent an additional tool for atrial substrate characterization, providing further information on tissue conductive properties and confirming bipolar substrate analysis. Methods The study includes the retrospective analysis of 60 electro–anatomical (EA) maps of patients with paroxysmal (40 patients) and persistent (20 patients) AF admitted to our institution for treatment. The clinical procedures have been performed with the support of CARTO3 mapping system. Map points have been collected with Navistar RMT Thermocool ablation catheter in order to enable the evaluation of atrial impedance values. To perform the correspondence analysis between the voltage map and impedance map, the atrial endocardial surface has been divided in six sections. Before ablation, for all patients a computed tomography has been performed in order to evaluate atrial endocardial thickness. Parameters of interest that have been evaluated in this study are EGMs voltage amplitude (mV) and fractionation (> five deflections per signal) and the corresponding impedance value (Ohm) at the considered acquisition point. Results In all PAF cases no voltages lower than 0.5 mV have been reported. The corresponding impedance values ranged from 140.6 to 169.9 Ohm, with an average value of 151.5 ± 5.4 Ohm. In PsAF cases, instead, voltage values inferior to 0.05 mV have been reported in the posterior wall, anterior wall and roof in 19/20 patients. In these low voltage areas, long duration fractionated signals have been reported and the average impedance value dropped to 129.1 ± 3.8 Ohm, ranging from 110.2 Ohm to 139.6 Ohm. Conclusion Our study supports the association between left atrial thickness, voltage amplitude and impedance values. This allows the correct substrate evaluation in case of uncertain bipolar values thanks to additional information provided by impedance mapping.

P193 A MYXOMA IN THE LEFT ATRIUM ADHERENT TO THE INTERATRIAL SEPTUM

Abstract A 73–year–old woman came to our observation to perform a routine echocardiographic examination. The patient had arterial hypertension, dyslipidemia, hypothyroidism, and paroxysmal atrial fibrillation. She underwent a bilateral mastectomy for breast cancer about 5 years ago, and she was undergoing chemotherapy and radiation therapy for a stage IV lung adenocarcinoma. The clinical evaluation was normal, as was the electrocardiogram. The transthoracic echocardiographic evaluation showed the presence of a rounded formation with variable echogenicity, with an irregular surface (4 x 3 cm), adherent to the interatrial septum at the level of the fossa ovalis, which did not hinder the excursion of the mitral valve. No other significant cardiac abnormalities were detected.Transesophageal echocardiography confirmed the presence of atrial mass adhered to the oval fossa (panels A, B). of coarsely rounded shape, and variable echogenicity, in the absence of interference with the movement of the valve leaflets and of anomalies of the interatrial septum (panel C). Coronary angiography showed right–dominant coronary circulation (panel D) and mild stenosis of the mid–left anterior descending artery. Abundant arterial perfusion of the atrial mass, with several vessels originating from the circumflex artery, was also evident at the coronary angiography (panels E, F). The patient underwent cardiac surgery; the surgical exeresis of the left atrial mass was performed through right mini–thoracotomy (panels I and L). Because the neo–formation was adherent not only to the atrial septum but also to the left atrial roof, to obtain a radical excision, a large portion of the atrial wall and the septum were removed and totally reconstructed with the pericardium. The main artery supplied the mass–related vascular network was ligated. The postoperative course was uneventful, and the patient was discharged at home on day six. The pre–discharge echocardiography and the cardiac magnetic resonance ( panels G, H) showed the absence of any residual mass in the left atrium that appears anatomically reshaped, no shunt at the level of the interatrial septum, and preserved ventricular function of both ventricles. Histological analysis confirmed the diagnosis of atrial myxoma. At the six–month follow–up the patient was asymptomatic and the echocardiography was superimposable to discharge.

P151 UTILITY OF MULTIMODALITY IMAGING IN A CASE OF MULTIPLE AORTIC POST–ENDOCARDITIS PSEUDOANEURYSMS

Abstract Introduction First–line therapy for infective endocarditis is antibiotic treatment to avoid the occurrence of complications such as septic embolization, septic shock (1), pseudoaneurysm or abscess formation (1). A pseudoaneurysm is a cavity that communicates with the vascular lumen and develops as a result of necrosis of the infected tissue (1). Case report: An 81–year–old man with past medical history of aortic valve replacement with bioprosthesis for severe stenosis and re–intervention for infective Enterococcus faecalis endocarditis was admitted to hospital for hyperpyrexia. PET–CT scan was performed. An aortic bioprosthesis hypercaptation suggestive of endocarditis recurrence was found. Blood cultures were positive for Staphylococcus epidermidis. Transesophageal echocardiography was initially negative for vegetations. Therefore, it was decided for a conservative approach with antibiotic therapy. About 2 months later the patient presented in our emergency department with atypical chest pain. At a transthoracic echocardiogram was reported an eccentric paravalvular regurgitation jet on bioprosthesis in atypical position and thickening of the periaortic tissue (Fig 1A). A contrast enhanced cardio–synchronized CT scan was performed confirming the presence of three paravalvular aortic pseudoaneurysms, the largest of 16x8 mm and located on the posterolateral portion of the valvular ring near to the left atrial wall (Fig 1B). Finally, a transesophageal echocardiogram was repeated finding a fistula from the posterior pseudoaneurysm to the left ventricular outflow tract (Fig 1C). The patient underwent re–intervention of aortic valve and ascending aorta replacement. Conclusions In this case–report, the use of multimodality imaging allowed adequate diagnosis of fistulizing paravalvular aortic pseudoaneurysms and proper subsequent surgical planning. The results of this case report suggest that following infective endocarditis presence of paravalvular aortic regurgitation with eccentric jet should be investigated with second–level diagnostic examinations for better anatomic resolution, such as cardio–synchronized CT and transesophageal echocardiogram. Bibliography: 1. Okada K et al. doi: 10.1007/s11748–012–0152–x

P104 LASER BALLOON APPROACH FOR PULMONARY VEIN ISOLATION IN MARFAN SYNDROME

Abstract Background Marfan syndrome (MFS) is an autosomal dominant disorder of the connective tissue and it’s associated with an increased incidence of atrial fibrillation (AF), due to scar–mediated processes and sites of atrial ectopy. Limited data exist regarding ablation techniques in these patients. The frailty of atrial walls correlated to connective disease makes the ablation challenging with an increased risk of complications. Laser–balloon (LB) approach for pulmonary vein isolation (PVI) could be a promising strategy due to the possibility to ablate a large volume of tissue with a single application of energy, short procedure times, and real–time monitoring of balloon–tissue contact. We present a case in which LB technology was applied for PVI in an MFS patient Clinical case A 44–year–old woman with MFS and paroxysmal AF underwent PVI. The echocardiographic examination showed mild aortic and mitral valve regurgitation, the first due to a slight dilation of the aortic root, the latter associated with mitral valve prolapse. Atrial volume was normal. No other comorbidities were present. The procedure was executed in general anesthesia. A decapolar catheter was inserted in the coronary sinus and used later to stimulate the phrenic nerve during the ablation of the right pulmonary veins (Fig.1C). Left atria (LA) was reached after an ultrasound–guided transeptal puncture. High–density mapping of the LA was performed to assess the number and geometry of PVs (Fig.1A). A LB catheter was used to perform laser ablation at the level of PV antrum, delivering 13 W in automatic rapid mode in regions with optimal contact and 5.5 W in areas with more represented blood–tissue interface. LA mapping after ablation assessed the effective isolation of pulmonary veins (Fig.1B). No complications occurred during the procedure. Conclusion a laser–balloon approach for PVI in MFS patients seems feasible and safe. To our knowledge, this is the first application of this technology on MFS patients. Larger data are needed to confirm our findings.

Post-processing methodology for the multimodal study of the left atrium during atrial fibrillation

In the context of a prospective study for the multimodal characterization of the left atrium in patients undergoing atrial fibrillation ablation, we developed a systematic pipeline to allow the co-registration and analysis of three different imaging modalities: LGE-CMR, 3D catheter-based invasive voltage maps and FDG uptake measured by PET. The software SLICER3D was choosed as the primary building block. As a free, open source software, it allows for the quick building and deployment of custom solutions thanks to its python wrapper. Several software solutions were developped in python using both the SLICER3D innate capabilities and the Vizualisation toolkit library (VTK) powerful post-processing power. Building on a previous work from Hohmann S. we developed a program allowing the importation in SLICER3D of CARTOv7 (biosense) voltage maps. Using built-in tools, 3D meshes were created from LGE-CMR and PET studies. Unto those 3D meshes, a custom program calculated a maximum intensity projection of the atrial wall along normal vectors, allowing for the creation of LGE and SUV 3D maps. Lastly, iterative point cloud registration permitted the fusion of all 3 mappings. Point-by-point test of association between low voltage, low FDG uptake and high-LGE was used. We were able to fusion and do a point-by-point analysis of three different imaging studies of the left atrium in atria fibrillation: voltage maps, LGE-CMR, and PET. Software solutions developed for this post-processing pipeline are generic and could be adapted for other multimodalities studies. A prospective study using this methodology and involving patients in AF undergoing ablation is underway and will be presented at the ESC congress 2023 (Fig. 1).

PO-03-097 DEFINING ELECTRODE CONFIGURATION FOR MAPPING MICROANATOMIC REENTRIES SUSTAINING ATRIAL FIBRILLATION

A major challenge in mapping atrial fibrillation (AF) to guide ablation is that it is unclear what resolution is required to map potential regions of interest such as those microanatomic reentries revealed by optical mapping of ex-vivo human hearts (fig. A). The goal of the study was to define the electrode configurations that can identify potential ablation targets as specific EGM traces generated during the conduction through the common path of AF microanatomic reentry. We simulated a microanatomic reentry sustaining AF in anisotropic 3D model of atrial tissue of 40x40x3 mm with an endocardial pectinate muscle of 3x3x15 mm (0.25 mm resolution, fig. B), using Koivumäki-cellular model of human atrial action potential. The simulation also included recordings of endocardial unipolar and bipolar electrodes (3 mm inter-electrode distance, 1 mm length, 2 mm diameter) with different distances and orientations from the pectinate muscle (fig. B). Local activation time map (fig. C) of the simulation showed sub-endocardial microanatomic reentry, with the common path through the pectinate muscle with a cycle length of 110 ms. The electrical activation through the pectinate muscle and atrial wall below the electrodes (Fig. D) was compared to the simulated EGM traces at different distances from the common path (fig. E). On EGMs close to the pectinate muscle (<2mm) electrical activity of reentrant common path can be identified in both unipolar and bipolar EGM signals by peak with amplitude similar or larger than the main atrial wall activation (figs E-F). When bipolar electrodes were perpendicular to the pectinate muscle, the peak amplitude of the common path activity was lower than 25% of the atrial wall peak amplitude. Our simulation suggested that inter-electrode distance to detect sub-endocardial microanatomic reentries sustaining AF should be < 4mm. Mapping was more reproducible for unipolar than for bipolar mapping, as bipolar electrodes were highly sensitive to orientation relative to the common path conduction.

PO-02-077 HYBRID CONVERGENT PROCEDURE FOR THE TREATMENT OF PERSISTENT AND LONG-STANDING PERSISTENT ATRIAL FIBRILLATION: A SINGLE CENTER EXPERIENCE

Pulmonary vein isolation by endocardial ablation is an effective treatment strategy for paroxysmal atrial fibrillation (AF). However, its effectiveness for treatment of persistent forms of AF is limited. In patients with advanced AF, there are extra-pulmonary vein foci that initiate and perpetuate AF. The left atrial posterior wall has been shown to have the highest proportion of such triggers. The Hybrid Convergent procedure is a novel procedure that combines epicardial and endocardial ablation to obtain isolation of the left atrial posterior wall and pulmonary veins. There is paucity of real world and long-term outcomes data regarding the Hybrid Convergent procedure. The purpose of this study is to describe the outcomes of Hybrid Convergent procedures for treatment of persistent and long standing persistent atrial fibrillation at 1 and 3 year follow up. A retrospective review of prospectively maintained single center Hybrid Convergent database was performed. Demographics, clinical, procedural, and outcomes data were collected on all patients. Atrial fibrillation burden was tracked using ECGs, wearable monitors, ICDs/pacemakers, implantable recorders and Holter monitors. Fifty patients with persistent and long-standing persistent AF underwent Hybrid Convergent procedure (age 62.6 ±9.1; male: 78%). Prior to ablation, the mean number of failed antiarrhythmic drugs was 2.3, mean number of previous ablations was 1.7, and mean left atrial volume index was 47.5 ± 17.9 ml/m2. 29 of 41 (71%) patients were free from AF recurrence at one year and 16 of 32 (50%) were free from AF at 3 years. The mean pre-operative AF burden for the group was 65.6 ± 40.2% on antiarrhythmics. Postoperatively, the total AF burden at 1 and 3 years were 23. 8 ± 40.9%, and 27.9 ± 41.1%, respectively. The Hybrid Convergent procedure is effective for the treatment of persistent and long-standing persistent AF with a 1- and 3-year freedom from AF recurrence of 71% and 50%, respectively. In this patient population, this procedure was able to reduce the mean burden of AF by 63.7% (41.8% absolute) at 1 year and by 57.4% (37.7% absolute) at 3 years. Our single center experience is consistent with the success rate from the Converge randomized trial at one year and provides additional 3 year follow up data.