Epicardial Mapping Research Articles

PO-04-062 CRYOABLATION OF INTRAMURAL SUBSTRATE IN AN IDIOPATHIC CRUX VT MAPPED BY NAVIGATING OTHERWISE INACCESSIBLE CS ANATOMY USING 2FR MAPPING CATHETER

Idiopathic cardiac crux VTs are are difficult to map and ablate due to their inaccessible location often requiring epicardial ablation. We report a unique case of a recurrent idiopathic crux VT originating near a trifurcated confluence of CS branches that required extensive mapping only accessible with the 2Fr EP catheter that was successfully ablated with cryoablation (due to proximity to coronary artery) from within the CS and the site-opposite (epicardially). Case Report A 40 year old man with idiopathic VT (normal Echo and cardiac MRI without LGE), prior endocardial VT ablation (RV septum and mid MCV), asthma, OSA, and the Arnold-Chiari malformation, was noted to have continued symptomatic PVCs and monomorphic wide-complex tachycardia at 164 bpm. A monomorphic VT (Figure) with CL 320-380 ms was only inducible with isoproterenol infusion at 20mcg/kg/min. We attempted to better define the CS anatomy and assess if there is a route via the CS to reach the Crux. The main body CS was noted to have a trifurcation into the MCV, a posterolateral branch and an anterior branch (extension of the CS main body) all meeting at an area of confluence (Figure 1). Detailed mapping was made possible using the CS-L telescoping catheter to carry the smaller 2French EP Star catheter deep into the multiple CS branches. We noted that the proximal MCV was 28ms early in VT (but not the best pace match) and the proximal lateral CS branch across from the MCV early site within the confluence had the best pace match. This suggests the origin was likely deep in between the two sites with the exit closer to the lateral branch site. Given that we noted that the PDA is in borderline proximity (5-6mm) to the site of ablation on coronary angiography, we chose to use to cryoablation (8 minute lesions) at the confluence of these branches at the marked sites to mitigate coronary injury. VT terminated with ablations at this site. Epicardial mapping was performed and no scar was noted. An additional single lesion was performed at the site opposite from the confluence with the best pace-map and VT was no longer inducible on repeat testing with isoproterenol. CSL telescoping catheter harboring the EP star catheter can be used to overcome challenging CS anatomy to bracket the Crux VT origin. Cryoablation (not without risk completely) can be potentially effective for Crux VTs approached from CS, especially if within borderline proximity to a coronary artery.

PO-01-142 ACUTE ATRIAL DILATION INCREASES REFRACTORY PERIOD AND CONDUCTION ABNORMALITIES: EVIDENCE FROM IN-VIVO MAPPING AND IN-VITRO LIVING ATRIAL SLICES

Atrial dilation shows strong clinical association with atrial fibrillation (AF) and its proarrhythmic nature is confirmed by various studies. However, previous (animal) models reproducing acute dilation yielded in conflicting effects on the functional refractory period (FRP). Shortcomings of previous studies included lack of in-human measurements, high-density mapping, atrial conduction characterization and titration of dilation. To evaluate the effect of acute atrial dilation on human atrial refractoriness and conduction with a two-way approach of in-vivo high-density mapping and in-vitro living atrial slices. Epicardial mapping with a 192-electrode array (inter-electrode distance 2.0 mm) was performed in 4 patients undergoing mitral valve surgery, without history of right atrial (RA) dilation and AF. Mapping was performed on the mid RA during baseline and overloaded conditions (echocardiographic RA diameter increase 10-20%) by positioning patients in Trendelenburg. Atrial FRP and conduction were evaluated with programmed extrastimulation, consisting of a S1-sequence with cycle length (CL) of 400ms followed by S2 stimuli of 300ms with decrements of 20ms. In addition, 23 living myocardial slices (LMS) (thickness: 300μm) were produced from RA left-over material from cardiac surgeries and cultured under electromechanical stimulation (diastolic preload 1mN, electrical stimulation 1.0Hz). These LMS were overloaded with 10–40% extra uniaxial lengthening for evaluation of FRP and early aftercontractions (EAC). FRP significantly increased during acute dilation both in in-vitro LMS (211±49 vs. 271±34ms, p=0.01) and during in-vivo electrophysiological mapping (255±30 vs. 280±23ms, p=0.042). FRP further increased with increasing dilation and EAC were more present in dilated LMS (Table 1). During acute dilation, S2 pacing (CL: 300ms) resulted in an increase in total activation time (TAT) (31 (29–39) vs. 67 (49–82) ms), conduction block (0.6 (0.0–3.0) vs. 12.9 (8.4-16.7)%) and total length of conduction block (2 (0–9) vs. 48 (21–72) mm). Moreover, the S2 stimulus with shortest coupling interval showed even more abnormalities in atrial conduction during dilation compared to baseline (Table 1). This first in-human study showed an unambiguous increase in atrial FRP and frequency-dependent conduction abnormalities during acute atrial dilation. These observations provide novel insights in the enhanced vulnerability for the development of AF in patients with dilated atria.Tabled 1Table 1In-vivo: EP mappingBaselineDilationRA Ø (cm)4.6 ± 1.05.6 ± 1.2CVP (mmHg)8 ± 418 ± 8FRP (ms)255 ± 30280 ± 23S1 400 msTAT (ms)34 (32 – 41)44 (40 – 52)CV (cm/s)85.5 (81.1 – 86.1)80.9 (77.7 – 83.8)CB (%)1.5 (1.1 – 2.1)3.1 (1.7 – 4.4)Length CB (mm)7 (5 – 9)16 (9 – 22)S2 300 msTAT (ms)31 (29 – 39)67 (49 – 82)CV (cm/s)82.1 (75.3 – 86.0)68.9 (61.6 – 79.8)CB (%)0.6 (0.0 – 3.0)11.7 (5.6 – 16.7)Length CB (mm)2 (0 – 9)48 (21 – 72)S2 with shortest coupling intervalTAT (ms)49 (41 – 61)82 (75 – 84)CV (cm/s)72.2 (67.0 – 78.3)66.7 (61.6 – 73.2)CB (%)6.0 (2.9 – 11.3)12.9 (8.4 – 16.7)Length CB (mm)30 (11 – 49)53 (33 – 72)In-vitro: LMSBaselineDilationAcute 20% (n=10)FRP (ms)211 ± 49271 ± 34EAC (%)0%50%Titration (n=13)10%20%30%40%FRP (ms)241 ± 46263 ± 68278 ± 63297 ± 75330 ± 79 Open table in a new tab

PO-04-077 EPICARDIAL ABLATION OF A PREVIOUSLY FAILED RIGHT LATERAL ACCESSORY PATHWAY

Catheter ablation is a potentially curative treatment for accessory pathways. However, ablation of right lateral accessory pathways is challenging and has a lower procedural success rate and high recurrence rate due to catheter instability and difficulty in catheter manipulation, inadequate tissue contact and structural heart disease like Ebstein's anomaly. We describe a challenging case of WPW syndrome with right lateral accessory pathway, where the pathway was located epicardially. N/A N/A A 23-year-old female with history of recurrent palpitations was evaluated and diagnosed as a case of WPW syndrome with right free wall pathway with structurally normal heart and normal biventricular function and failed ablation twice in 2018 and 2020. In view of recurrent symptoms, patient was started on anti-arrhythmic therapy. As the patient was refractory to flecainide, sotalol and amiodarone , she was referred to our center for a repeat ablation. Baseline ECG showed manifest pre-excitation. A standard electrophysiology study was performed under general anaesthesia with sequential endocardial and epicardial mapping approach. Retrograde ERP (effective refractory period) of the pathway was 240 ms whereas antegrade ERP was 340 ms (on amiodarone and general anaesthesia). Orthodromic atrio-ventricular reciprocating tachycardia was easily induced by programmed stimulation with a tachycardia cycle length of 470 ms with earliest atrial electrogram noted in the lateral right atrium. However, despite extensive mapping of the tricuspid annulus, ablation at the earliest endocardial site failed to terminate the tachycardia. Hence, epicardial access was obtained using Sosa’s tenchique and mapping along the tricuspid annulus was performed. At lateral tricuspid annulus epicardially, fused atrial and ventricular signals were obtained with local ventricular signal preceding the surface delta wave by 35 ms. Right coronary angiography revealed safe distance between the right coronary artery and the site of ablation. Epicardial ablation at this site led to loss of accessory pathway conduction within 5 seconds. Post ablation, no tachycardia was inducible despite aggressive pacing protocols and bidirectional AV block was demonstrated using intravenous adenosine. At 1-year follow-up, patient is asymptomatic with no evidence of accessory pathway conduction. Epicardial mapping and ablation should be considered in previously failed cases of endocardial ablation of right lateral accessory pathways.

PO-05-096 PROGNOSTIC VALUE OF NEAR-FIELD ELECTROGRAMS AT CRITICAL ABLATION SITES DURING VENTRICULAR TACHYCARDIA ABLATION

Electrogram (EGM) annotation during VT is challenging due to complexity of EGMs and difficulty in distinguishing far-field and near-field (NF) EGMs. EGM frequency increases with greater EGM proximity to the recording electrode. The prognostic value of high-frequency EGMs at critical ablation sites during VT ablation is unknown. The utility of recently developed algorithms to annotate local EGM frequency during 3D mapping (Ensite X, Abbott, Inc.) is unknown. The absence of high frequency EGMs at critical sites for VT ablation may suggest that the EGM of interest is deep to or remote from the recording electrode. To investigate the utility of the EGM frequency annotation at critical ablation sites during VT ablation. Consecutive patients with scar-related VT undergoing catheter ablation (RFA) were analyzed. High density substrate maps were created in presenting ventricular rhythm using a High-definition multi-electrode mapping catheter (HD Grid, Abbott, Inc.). Critical sites for induced VT were identified based on pace-mapping, activation mapping, entrainment mapping, or termination of VT with RFA. Substrate maps were retrospectively analyzed with EGM annotation based on NF EGM. The highest frequency EGM within 5mm of the critical ablation site was identified and analyzed. Thirty-four critical sites were identified and ablated in twenty-two patients, 14 (64%) with ischemic cardiomyopathy, age 65±10 years with LVEF was 33±13 %. VT recurred in 9 patients (41%). The peak frequency in the critical site using the NF annotation in patients with recurrence was significantly lower than in patients without recurrence (192 vs 397 Hz; p=0.01). Cox regression analysis shows statistically significant higher risk to have VT recurrence when the frequency is below the median frequency (HR 5.09, 95% C.I 1.05-24.68, p=0.04). Area under the receiver operator characteristic curve for peak EGM frequency at VT critical site as a predictor of VT recurrence was 0.81, with critical site EGM frequency < 286 Hz providing 89% sensitivity and 69% specificity for VT recurrence. Low frequency EGMs at VT critical sites measured by EGM frequency annotation software identify patients at greater risk of VT recurrence. A finding of low frequency EGMs at apparent critical site implies that the successful ablation may require additional mapping, including consideration of epicardial or venous mapping, to localize better the true critical site or ablation techniques to provide deeper ablation.

PO-05-001 TARGETING WAVEFRONT DISCONTINUITY LINES FOR SCAR-RELATED VENTRICULAR TACHYCARDIA ABLATION

Late activation mapping can identify wavefront discontinuities during functional substrate mapping. Automated visualization of wavefront discontinuity lines (WaDLs) representing conduction block or delay may be a suitable target for a focused VT ablation. To describe WaDLs in multiple types of cardiomyopathy undergoing VT ablation, with correlation to critical VT circuit sites and bipolar low voltage scar. Patients who underwent high density substrate ablation with late activation mapping in sinus or paced wavefront were retrospectively analyzed. An automated mapping algorithm was used to visually demarcate WaDLs by identifying adjacent points where mapped activation times were greater than a certain timing threshold (CARTO®,Biosense Webster) Extended Early Meets Late module). Timing threshold was set to 25-35% of the mapped activation time. The number, total length, and distance to critical VT site of WaDLs was compared at each threshold 34 patients (20 post-infarct, 10 dilated, 1 Chagas, 1 sarcoid, 1 ARVC, 1 lamin) with 46 endocardial or epicardial surface substrate maps (10 epicardial, 36 endocardial; mean 1898 points) were included. WaDLs were present in each cardiomyopathy and surface, and represented average timing discontinuities of 50-61 ms (25%-35% WaDL threshold) with no difference in number or length of WaDLs by the mapped chamber, cardiomyopathy type, or wavefront. Parallel WaDLs forming putative channels were present in 37.2% of mapped chambers. In 15 patients with a critical VT site identified, the median distance from critical site to nearest WaDL was 7.4 mm (IQR 2.2-18.6 mm), with shorter distances on the epicardial surfaces compared to endocardial (1.4 vs 13.9 mm at 30% WaDL, P = 0.015). Functional substrate ablation in this cohort covered a mean 26% of the bipolar low voltage scar area (< 1.5 mV). Automated WaDLs represent easily visualized significant discontinuities that correlate with clinical VT circuits, are present in a wide variety of cardiomyopathy types and both epicardial and endocardial surfaces. Targeting WaDLs requires a smaller ablation area than low voltage homogenization.

PO-02-184 MAPPING-GUIDED ATRIAL LEAD PLACEMENT DETERMINES OPTIMAL CONDUCTION ACROSS BACHMANN’S BUNDLE: A RATIONALE FOR PATIENT-TAILORED PACING THERAPY

Bachmann’s Bundle (BB) is the main preferential route for interatrial conduction and plays an important role in initiation and perpetuation of atrial tachyarrhythmia such as atrial fibrillation (AF). Conventional right atrial appendage (RAA) pacing is associated with increased atrial activation time resulting in higher incidences of AF. Optimal pacing sites ideally shorten inter-atrial conduction delay thereby decreasing atrial excitation time. However, it remains unknown how pacing from various sites affects conduction at BB. To examine the impact of programmed stimulation from the left- and right atrium on activation and electrophysiological features of BB. High-resolution epicardial mapping of BB was performed during sinus rhythm (SR) and PES in 34 patients undergoing cardiac surgery. PES included a fixed rate sequence of average SR cycle length minus 50 ms provided from the RAA, junction of the RA with inferior caval vein (LRA) and left atrial appendage (LAA). Electrophysiological features included unipolar voltage, conduction velocity, potential type (single, short/long double and fractionated) and conduction delay/block (CDCB). The average cycle length during SR was 967 [874–1,185] ms. Pacing from either RAA or LAA resulted in respectively right- and left-sided conduction across BB. However, during LRA pacing in most patients (n=15) activation started in the center of BB. Compared to SR, the least amount of differences in electrophysiological features was found during pacing from the RAA, followed by pacing from LRA and LAA. Total activation time of BB during RAA pacing (63 [55–78] ms) was similar to SR (61 [52–68] ms, P=0.464), while it decreased during LRA (45 [39–62] ms, P=0.003) and increased during LAA pacing (67 [61–75] ms, P=0.009). Reduction of both conduction disorders and total activation time was most often achieved during LRA pacing (N=13), especially in patients who already had a higher amount of conduction disorders during SR (9.8 [7.3–12.3] vs 4.5 [3.5–6.6]%, P<0.001). Pacing from LRA results in a remarkable decrease of total activation time compared to pacing from the LAA or RAA. As the most optimal pacing site varies between patients, individualized positioning of the atrial pacing lead guided by mapping of BB may be one of the new frontiers for atrial pacing.

PO-455617-1 EXPLORING THE INTERPLAY OF FUNCTIONAL AND STRUCTURAL REMODELING PROGRESSION IN ATRIAL FIBRILLATION IN A RAPID ATRIAL PACING CANINE MODEL

In sustained atrial fibrillation (AF) it is still unclear to what extent, at which time points functional and structural remodeling processes develop over time, and which parameters can measure the progression state. We hypothesized that persistent AF progression state induced by rapid atrial pacing (RAP) can be uncovered by measuring electrogram characteristics, OS levels, nerve activity, and the degree of fibrosis with MRI imaging. AF was induced in 15 dogs (25-35 kg, ≥1 year) by RAP (3-17 weeks RAP, 600 beats/min), and 8 controls were used. We performed high-resolution epicardial mapping (6 regions, 130 electrodes, distance 2.5mm) (Figure 1) and analyzed bipolar peak-to-peak voltage, cycle length (CL), and organization index (OI). We quantified OS levels as damaged nuclei against total number in 8-OHdG staining (N=36 samples, 6 animals) and degree of fibrosis (Masson’s trichrome) (N=24, 4 dogs). We also quantified in implantable telemetry recordings (DSI) parasympathetic nerve activity (PNA) (2 hours) assessed as the time between PNA spikes (3 AF dogs, 3 controls). MRI native T1, post-contrast T1, and T2 mapping, and late gadolinium enhancement (LGE) were assessed (1.5T clinical scanner, Siemens Aera) in the posterior left atrium (PLA) (7 AF, 8 at baselines). Voltage, CL, and OI decreased (R=0.9, P<0.05), (R=0.6, P<0.05), (R=0.5, P<0.05) over time of RAP (Figure 1). After 80 RAP days voltage changed, but no more changes in other EGM measures were observed. OS levels in AF were highest in the left atrial free wall and lowest in the appendages (Figure 2). The electrogram measures OI and CL decreased with increased oxidative stress levels (Figure 2). Fibrosis (R=0.6, P<0.05) increased with OS (R=0.6, P<0.05) in all atrial regions (Figure 2). Parasympathetic nerve activity increased by factor 5 after 120 RAP days, (Figure 3). Native T1, T2 times increased with RAP days (R=0.6, P<0.05), (R=0.4, P<0.05) in PLA (<120 pacing days) (Fig. 4). Functional and structural remodeling in persistent AF is the result of an interplay among the development of increased OS, fibrosis, and nerve activity in a RAP canine model and can moderately be uncovered using the electrogram measures CL and OI until the saturation point after 80 RAP days. Voltage also uncovers the AF progression state post 80- RAP days with a strong correlation coefficient. Additional parasympathetic nerve recordings and MRI imaging including T1 mapping may be complementary to detect AF remodeling states.

PO-02-208 CHARACTERIZATION OF ATRIAL ELECTROPHYSIOLOGICAL PROPERTIES IN PATIENTS WITH HYPERTROPHIC OBSTRUCTIVE CARDIOMYOPATHY

Atrial fibrillation (AF) occurs frequently in patients with hypertrophic obstructive cardiomyopathy (HOCM) and the success rate of pulmonary vein isolation in these patients is less effective compared to other populations. This may be explained by the presence of an extensive arrhythmogenic substrate in both atria due to a primary atrial myopathy, but electrophysiological properties of the right (RA) and left atrium (LA) have never been investigated. The aim of this study is to 1) quantify atrial electrophysiological properties during sinus rhythm and 2) to determine whether atrial electrogram morphology and conduction disorders differ between the RA and LA in patients with HOCM. Intra-operative epicardial mapping of both atria was performed in HOCM patients undergoing surgical myectomy. Conduction delay and/or block (CD, CB), unipolar electrograms characteristics (unipolar voltages, potential fractionation) and low voltage areas (LVA) were quantified during sinus rhythm. Fifteen patients (mean age: 50± 12 years) were included. Conduction disorders were found in both atria in all patients, but did not differ between the RA and LA (CD: 2.9 [1.9-3.6] % versus 2.6 [2.1-6.4] %, p=0.541; CB: 1.7 [0.9-3.1] % versus 1.5 [0.5-2.8] %, p=0.600; respectively). Though unipolar voltages histograms differed significantly between the RA and LA (Table 1), LVA were equally present in both RA and LA (RA: 4.7 % [1.6-7.7] % versus LA: 2.9 % [2.1-7.1] %, p=0.793). The magnitude of unipolar voltages of single- and complex fractionated potentials (SP, CFP) were higher in the LA compared to the RA (SP: P75 10.9 mV versus 7.3 mV, respectively; CFP: P75 3.7 mV versus 2.0 mV, respectively).(Table 1) CFP corresponded to LVA in only 18% of all LA sites compared to 36% of all RA sites. In patients with HOCM, the magnitude of unipolar voltages is considerably higher in the LA compared to the RA. Remarkably, fractionated potentials in both atria mainly contained high voltage deflections. Therefore, substrate modification strategies, consisting of low voltage or other electrogram morphology guided AF ablation strategies, should be disease-tailored in this population. The observed equal amount of conduction disorders and LVA in both atria support the concept of a primary atrial myopathy with a bi-atrial substrate in HOCM patients.

Reinventing Larrey’s approach for epicardial mapping: The closed pericardiostomy technique

Reinventing Larrey’s approach for epicardial mapping: The closed pericardiostomy technique

High-density and high coverage composite mapping of repetitive atrial activation patterns

BackgroundRepetitive atrial activation patterns (RAAPs) during atrial fibrillation (AF) may be associated with localized mechanisms that maintain AF. Current electro-anatomical mapping systems are unsuitable for analyzing RAAPs due to the trade-off between spatial coverage and electrode density in clinical catheters. This work proposes a technique to overcome this trade-off by constructing composite maps from spatially overlapping sequential recordings. MethodsHigh-density epicardial contact mapping was performed during open-chest surgery in goats (n=16, left and right atria) with 3 or 22 weeks of sustained AF (249-electrode array, electrode distance 2.4 mm). A dataset mimicking sequential recordings was generated by segmenting the grid into four spatially overlapping regions (each region 6.5 cm2, 48±10% overlap) without temporal overlap. RAAPs were detected in each region using recurrence plots of activation times. RAAPs in two different regions were joined in case of RAAP cross-recurrence between overlapping electrodes. We quantified the reconstruction success rate and quality of the composite maps. ResultsOf 1021 RAAPs found in the full mapping array (32±13 per recording), 328 spatiotemporally stable RAAPs were analyzed. 247 composite maps were generated (75% success) with a quality of 0.86±0.21 (Pearson correlation). Success was significantly affected by the RAAP area. Quality was weakly correlated with the number of repetitions of RAAPs (r=0.13, p<0.05) and not affected by the atrial side (left or right) or AF duration (3 or 22 weeks of AF). ConclusionsConstructing composite maps by combining spatially overlapping sequential recordings is feasible. Interpretation of these maps can play a central role in ablation planning.

Age-related increases in cardiac excitability, refractoriness and impulse conduction favor arrhythmogenesis in male rats.

The effects of excitability, refractoriness, and impulse conduction have been independently related to enhanced arrhythmias in the aged myocardium in experimental and clinical studies. However, their combined arrhythmic effects in the elderly are not yet completely understood. Hence, the aim of the present work is to relate relevant cardiac electrophysiological parameters to enhanced arrhythmia vulnerability in the in vivo senescent heart. We used multiple-lead epicardial potential mapping in control (9-month-old) and aged (24-month-old) rat hearts. Cardiac excitability and refractoriness were evaluated at numerous epicardial test sites by means of the strength-duration curve and effective refractory period, respectively. During sinus rhythm, durations of electrogram intervals and waves were prolonged in the senescent heart, compared with control, demonstrating a latency in tissue activation and recovery. During ventricular pacing, cardiac excitability, effective refractory period, and dispersion of refractoriness increased in the aged animal. This scenario was accompanied by impairment of impulse propagation. Moreover, both spontaneous and induced arrhythmias were increased in senescent cardiac tissue. Histopathological evaluation of aged heart specimens revealed connective tissue deposition and perinuclear myocytolysis in the atria, while scattered microfoci of interstitial fibrosis were mostly present in the ventricular subendocardium. This work suggests that enhanced arrhythmogenesis in the elderly is a multifactorial process due to the joint increase in excitability and dispersion of refractoriness in association with enhanced conduction inhomogeneity. The knowledge of these electrophysiological changes will possibly contribute to improved prevention of the age-associated increase in cardiac arrhythmias.

Intraoperative open chest epicardial high-density mapping and ablation for refractory ventricular tachycardia at time of magnetically levitated left ventricular assist device implantation

Intraoperative open chest epicardial high-density mapping and ablation for refractory ventricular tachycardia at time of magnetically levitated left ventricular assist device implantation

Catheter Ablation of Left Ventricular Summit Arrhythmias from Adjacent Anatomic Vantage Points.

Idiopathic ventricular arrhythmias (VA), particularly left ventricular outflow tract (LVOT) VA accounts for up to 10% of all VAs referred for ablative therapy. In addition to being infrequent, its intricate anatomy and its pathophysiology make catheter ablation (CA) of these arrhythmias a challenge even for experts. In this scenario, detailed right ventricular outflow tract as well as LVOT electroanatomic mapping including epicardial mapping are essential. In this article, we will emphasize our approach toward the CA technique used for LVOT VA, particularly IVS and/or LVS VA originating from intramural foci, along with its acute and long-term efficacy and safety.

Mapping-guided atrial lead placement determines optimal conduction across Bachmann's bundle: a rationale for patient-tailored pacing therapy.

Conventional right atrial appendage (RAA) pacing is associated with increased atrial activation time resulting in higher incidences of atrial tachyarrhythmia. Optimal pacing sites ideally shorten inter-atrial conduction delay, thereby decreasing atrial excitation time. We therefore examined the impact of programmed electrical stimulation (PES) from the right atrium (RA) and left atrium (LA) on the electrophysiological properties of Bachmann's bundle (BB). High-resolution epicardial mapping of BB was performed during sinus rhythm (SR) and PES in 34 patients undergoing cardiac surgery. Programmed electrical stimulation was performed from the RAA, junction of the RA with inferior caval vein (LRA), and left atrial appendage (LAA). Pacing from either the RAA or LAA resulted in, respectively, right- and left-sided conduction across BB. However, during LRA pacing in most patients (n = 15), activation started in the centre of BB. The total activation time (TAT) of BB during RAA pacing [63 (55-78) ms] was similar to that of SR [61 (52-68) ms, P = 0.464], while it decreased during LRA [45 (39-62) ms, P = 0.003] and increased during LAA pacing [67 (61-75) ms, P = 0.009]. Reduction of both conduction disorders and TAT was most often achieved during LRA pacing (N = 13), especially in patients who already had a higher amount of conduction disorders during SR [9.8 (7.3-12.3) vs. 4.5 (3.5-6.6)%, P < 0.001]. Pacing from the LRA results in a remarkable decrease of TAT compared with pacing from the LAA or RAA. As the most optimal pacing site varies between patients, individualized positioning of the atrial pacing lead guided by mapping of BB may be one of the new frontiers for atrial pacing.

Technical development and feasibility of a reusable vest to integrate cardiovascular magnetic resonance with electrocardiographic imaging

BackgroundElectrocardiographic imaging (ECGI) generates electrophysiological (EP) biomarkers while cardiovascular magnetic resonance (CMR) imaging provides data about myocardial structure, function and tissue substrate. Combining this information in one examination is desirable but requires an affordable, reusable, and high-throughput solution. We therefore developed the CMR-ECGI vest and carried out this technical development study to assess its feasibility and repeatability in vivo. MethodsCMR was prospectively performed at 3T on participants after collecting surface potentials using the locally designed and fabricated 256-lead ECGI vest. Epicardial maps were reconstructed to generate local EP parameters such as activation time (AT), repolarization time (RT) and activation recovery intervals (ARI). 20 intra- and inter-observer and 8 scan re-scan repeatability tests. Results77 participants were recruited: 27 young healthy volunteers (HV, 38.9 ± 8.5 years, 35% male) and 50 older persons (77.0 ± 0.1 years, 52% male). CMR-ECGI was achieved in all participants using the same reusable, washable vest without complications. Intra- and inter-observer variability was low (correlation coefficients [rs] across unipolar electrograms = 0.99 and 0.98 respectively) and scan re-scan repeatability was high (rs between 0.81 and 0.93). Compared to young HV, older persons had significantly longer RT (296.8 vs 289.3 ms, p = 0.002), ARI (249.8 vs 235.1 ms, p = 0.002) and local gradients of AT, RT and ARI (0.40 vs 0.34 ms/mm, p = 0,01; 0.92 vs 0.77 ms/mm, p = 0.03; and 1.12 vs 0.92 ms/mm, p = 0.01 respectively). ConclusionOur high-throughput CMR-ECGI solution is feasible and shows good reproducibility in younger and older participants. This new technology is now scalable for high throughput research to provide novel insights into arrhythmogenesis and potentially pave the way for more personalised risk stratification. Clinical trial registration: Title: Multimorbidity Life-Course Approach to Myocardial Health—A Cardiac Sub-Study of the MRC National Survey of Health and Development (NSHD) (MyoFit46). National Clinical Trials (NCT) number: NCT05455125. URL: https://clinicaltrials.gov/ct2/show/NCT05455125?term=MyoFit&draw=2&rank=1

Premature atrial contractions promote local directional heterogeneities in conduction velocity vectors.

Loss of cell-to-cell communication results in local conduction disorders and directional heterogeneity (LDH) in conduction velocity (CV) vectors, which may be unmasked by premature atrial contractions (PACs). We quantified LDH and examined differences between sinus rhythm (SR) and spontaneous PACs in patients with and without atrial fibrillation (AF). Intra-operative epicardial mapping of the right and left atrium (RA, LA), Bachmann's bundle (BB) and pulmonary vein area (PVA) was performed in 228 patients (54 with AF). Conduction velocity vectors were computed at each electrode using discrete velocity vectors. Directions and magnitudes of individual vectors were compared with surrounding vectors to identify LDH. Five hundred and three PACs [2 (1-3) per patient; prematurity index of 45 ± 12%] were included. During SR, most LDH were found at BB and LA [11.9 (8.3-14.9) % and 11.3 (8.0-15.2) %] and CV was lowest at BB [83.5 (72.4-94.3) cm/s, all P < 0.05]. Compared with SR, the largest increase in LDH during PAC was found at BB and PVA [+13.0 (7.7, 18.3) % and +12.5 (10.8, 14.2) %, P < 0.001]; CV decreased particularly at BB, PVA and LA [-10.0 (-13.2, -6.9) cm/s, -9.3 (-12.5, -6.2) cm/s and -9.1 (-11.7, -6.6) cm/s, P < 0.001]. Comparing patients with and without AF, more LDH were found during SR in AF patients at PVA and BB, although the increase in LDH during PACs was similar for all sites. Local directional heterogeneity is a novel methodology to quantify local heterogeneity in CV as a possible indicator of electropathology. Intra-operative high-resolution mapping indeed revealed that LDH increased during PACs particularly at BB and PVA. Also, patients with AF already have more LDH during SR, which becomes more pronounced during PACs.

Epicardial high-resolution mapping of advanced interatrial block: Relating ECG, conduction abnormalities and excitation patterns.

Impairment of conduction across Bachmann's Bundle (BB) may cause advanced interatrial block (a-IAB), which in turn is associated with development of atrial fibrillation. However, the exact relation between a complete transverse line of conduction block (CB) across BB and the presence of a-IAB has not been studied. The aims of this study are to determine whether (1) a complete transversal line of CB across BB established by high resolution mapping correlates with a-IAB on the surface ECG, (2) conduction abnormalities at the right and left atria correlate with a-IAB, and (3) excitation patterns are associated with ECG characteristics of a-IAB. We included 40 patients in whom epicardial mapping revealed a complete transverse line of CB across BB. Pre-operative ECGs and post-operative telemetry were assessed for the presence of (a) typical a-IAB and de novo early post-operative AF (EPOAF), respectively. Total atrial excitation time (TAET) and RA-LA delay were calculated. Entry site and trajectory of the main sinus rhythm wavefront at the pulmonary vein area (PVA) were assessed. Thirteen patients were classified as a-IAB (32.5%). In the entire atria and BB there were no differences in conduction disorders, though, patients with a-IAB had an increased TAET and longer RA-LA delay compared to patients without a-IAB (90.0 ± 21.9 ms vs. 74.9 ± 13.0 ms, p = 0.017; 160.0 ± 27.0 ms vs. 136.0 ± 24.1 ms, p = 0.012, respectively). Patients with typical a-IAB solely had caudocranial activation of the PVA, without additional cranial entry sites. Prevalence of de novo EPOAF was 69.2% and was similar between patients with and without a-IAB. A transverse line of CB across BB partly explains the ECG characteristics of a-IAB. We found atrial excitation patterns underlying the ECG characteristics of both atypical and typical a-IAB. Regardless of the presence of a-IAB, the clinical impact of a complete transverse line of CB across BB was reflected by a high incidence of de novo EPOAF.

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

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. 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. 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.

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

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

Beta-Receptor Blockade Reproduces Electrophysiological Effects of Early Diabetes Mellitus in Ventricular Myocardium

Diabetes mellitus (DM) increases the risk of sudden cardiac death, which suggests the involvement of arrhythmogenic mechanisms. Among other changes, DM causes cardiac autonomic neuropathy (CAN), but its role in electrophysiological myocardial remodeling is unclear. The objective of the present study was to test the effects of β-adrenergic blockade regarding ventricular spatiotemporal electrophysiological properties in an experimental DM model. Epicardial mapping (64-lead sock electrode array) was done in 13 control and 11 alloxan-induced DM rabbits. Activation times (AT), end of repolarization times (RT), and activation-repolarization intervals (ARI) were determined as dV/dt min during QRS, dV/dt max during T-wave, and RT-AT difference, respectively. The β-adrenergic blockade was produced by esmolol infusion (0.5 mg/kg, i.v.). It was found that the early-stage DM in rabbits was characterized by relatively mild changes in ventricular myocardium, which did not involve ventricular activation and the average duration of repolarization. The signature of this stage was the local prolongation of repolarization, which pertained to the RV apical region. The blockade of β-adrenergic receptors in healthy animals produced a ventricular spatiotemporal repolarization pattern similar to that observed in diabetic rabbits with the local apical prolongation of repolarization. On the other hand, the blockade of β-adrenergic receptors in diabetics prolonged the relatively short basal repolarization. It can be concluded that β-adrenergic blockade in healthy animals reproduced the early-stage DM effects on the spatiotemporal electrophysiological properties of the ventricular myocardium. This demonstrated the role which CAN could play in the electrical remodeling of ventricular myocardium in early-stage DM.