Sinus Rhythm Mapping Research Articles

Impact of Multidirectional Pacing on Activation and Repolarization Parameters to Localize Ischemic Ventricular Tachycardia Circuits.

In ventricular tachycardia (VT), optimal substrate mapping strategies identifying arrhythmogenic sites are not established. This study sought to evaluate multidirectional pacing on the distribution of specific conduction and repolarization metrics to localize re-entrant VT sites in a porcine infarct model. Substrate maps were created in 13 pigs with chronic myocardial infarction using the Advisor HD Grid (Abbott) during right ventricular (RV), left ventricular, biventricular pacing (BIV), and sinus rhythm (SR). Critical VT sites of early-, mid-, and late-diastolic signals were delineated. Vulnerable sites to re-entry were defined as sites of latest activation timing within and post-QRS complex, largest activation and activation-recovery interval gradients. Distances between the 20 most vulnerable sites and diastolic VT points were measured, and identification of VT points was assessed using the area under the receiver-operating characteristic curve. A total of 34 VTs were mapped, and 48 sinus and pacing maps were obtained (10 BIV, 13 left ventricular, 13 RV, 12 SR). Late potential mapping in SR was taken as the established clinical standard for comparison. Latest activation time with BIV pacing provided the closest localization for VT isthmus (median 5.5mm; IQR: 7.15mm; P< 0.005). The gradient of activation-recovery interval using RV pacing had closest localization for VT exit and entrance (median 10.6mm; IQR: 5.0mm; P< 0.005 and 9.4mm; IQR: 8.0mm; P< 0.05). Global sensitivity and specificity analysis showed that gradient of activation-recovery interval in SR achieved the highest area under the receiver-operating characteristic curve, with similar results from the gradient of activation timing. Multidirectional pacing in combination with conduction and repolarization parameters enables better localization of VT diastolic critical sites vs SR late potentials.

Sinoatrial node function and the role of sinoatrial conduction in the typical atrial flutter substrate

BackgroundSinoatrial node (SAN) activation and sinoatrial conduction pathways (SACPs) have been assessed in animals but not in humans. ObjectivesWe used ultrahigh-density mapping and simulated models to characterize the SAN and to investigate whether slowed SAN conduction may contribute to the atrial flutter (AFL) substrate. MethodsTwenty-seven patients undergoing electrophysiologic procedures had right atrial mapping. SAN activation patterns and conduction block were analyzed. The interaction between the SAN and the intercaval line of block (LOB) was analyzed, and right atrial simulations with different degrees of block were created to investigate arrhythmia mechanisms. ResultsFifteen AFL patients and 12 reference patients were enrolled. SACPs were identified in all patients with sinus rhythm maps. An SAN-adjacent LOB was observed in AFL patients. SAN conduction velocity was slower in AFL vs reference (0.60 m/s [0.56–0.78 m/s] vs 1.13 m/s [1.00–1.21 m/s]; P = .0021). Coronary sinus paced maps displayed an intercaval LOB in AFL patients but not in reference patients, which was completed superiorly by the SAN-adjacent LOB. Corrected sinus node recovery time was longer in AFL patients (552.3 ± 182.9 ms vs 325.4 ± 138.3 ms; P < .006) and correlated with degree of intercaval block (r = 0.7236; P = .0003). Computer modeling supported an important role of SAN-associated block in the flutter substrate. ConclusionUltrahigh-density mapping accurately identifies SAN activation and SACPs. The LOB important for typical AFL was longer in AFL patients, and when partial, it was always present inferiorly and completed superiorly because of slowed conduction across the SAN. Corrected sinus node recovery time correlated with intercaval block, suggesting a role for SAN disease in the genesis of the typical AFL substrate.

Detailed analysis of electrogram peak frequency to guide ventricular tachycardia substrate mapping.

Differentiating near-field (NF) and far-field (FF) electrograms (EGMs) is crucial in identifying critical arrhythmogenic substrate during ventricular tachycardia (VT) ablation. A novel algorithm annotates NF-fractionated signals enabling EGM peak frequency (PF) determination using wavelet transformation. This study evaluated the algorithms' effectiveness in identifying critical components of the VT circuit during substrate mapping. A multicentre, international cohort undergoing VT ablation was investigated. VT activation maps were used to demarcate the isthmus zone (IZ). Offline analysis was performed to evaluate the diagnostic performance of low-voltage area (LVA) PF substrate mapping. A total of 30 patients encompassing 198 935 EGMs were included. The IZ PF was significantly higher in sinus rhythm (SR) compared to right ventricular paced (RVp) substrate maps (234 Hz (195-294) vs. 197 Hz (166-220); P = 0.010). Compared to LVA PF, the IZ PF was significantly higher in both SR and RVp substrate maps (area under curve, AUC: 0.74 and 0.70, respectively). The LVA PF threshold of ≥200 Hz was optimal in SR maps (sensitivity 69%; specificity 64%) and RVp maps (sensitivity 60%; specificity 64%) in identifying the VT isthmus. In amiodarone-treated patients (n = 20), the SR substrate map IZ PF was significantly lower (222 Hz (186-257) vs. 303 Hz (244-375), P = 0.009) compared to amiodarone-naïve patients (n = 10). The ≥200 Hz LVA PF threshold resulted in an 80% freedom from VT with a trend towards reduced ablation lesions and radiofrequency times. LVA PF substrate mapping identifies critical components of the VT circuit with an optimal threshold of ≥200 Hz. Isthmus PF is influenced by chronic amiodarone therapy with lower values observed during RV pacing.

Omnipolar conduction velocity mapping for ventricular substrate characterization: Impact of CV estimation method and EGM type on in vivo conduction velocity measurements

BackgroundAreas of abnormal or heterogeneous conduction velocity (CV) are important ablation targets for ventricular tachycardias, yet precise assessment of CV in clinical contact mapping remains challenging. Numerous different CV estimation methods have been proposed. ObjectiveThis study aimed to compare the automated local activation time (LAT)–independent omnipolar-based CV estimation method termed wave speed (WS) with 4 established LAT-based methods to formally establish the quantitative differences between them. MethodsHigh-density contact maps in patients with structurally normal hearts during sinus rhythm (SR) and ventricular ectopy (VE) were retrospectively analyzed. CV was assessed and compared by 5 methods: omnipolar WS, gradient method, planar wavefront fitting, circular wavefront fitting, and radial basis function. CV variations based on electrogram (EGM) type (unipolar, bipolar, and omnipolar), catheter movement, and surrogate markers for catheter contact were analyzed. ResultsThe study included 23 patients (47.8% male; 45.7 ± 17.3 years) with 22 SR maps (11 left ventricle, 11 right ventricle) and 16 VE maps (9 left ventricle, 7 right ventricle). The WS algorithm yielded statistically significant higher CV estimates in SR (mean, 1.41 ± 0.18 m/s) and VE (mean, 1.23 ± 0.18 m/s) maps compared with all LAT-based estimation methods, with absolute differences ranging from 0.1 m/s to 0.81 m/s. Median pointwise differences in SR and VE between WS and LAT-based methods were high, ranging from 0.55 ± 0.15 m/s (WS vs planar wavefront fitting) to 0.67 ± 0.16 m/s (WS vs radial basis function). For LAT-based methods, use of unipolar EGMs yielded significantly higher CV estimates than bipolar or omnipolar EGMs in SR. ConclusionThe CV estimation method has an important, statistically significant impact on ventricular CV measurements. Future work will focus on how these differences affect identification of pathologic conduction slowing in scar-related substrate.

Localization of critical isthmus in left atrial macroreentrant tachycardias: insights from peak frequency mapping during sinus rhythm and coronary sinus pacing

Abstract Background Successful ablation of left atrium macroreentrant tachycardia (LAMRT) has advanced significantly, benefiting from an enhanced understanding of reentrant mechanisms and technological innovations. However, challenges like difficult inductions and the presence of multiple coexistent LAMRTs can complicate tachycardia mapping, potentially resulting in recurrences during follow-up. Consequently, there is a growing need for strategies that focus on pinpointing the critical isthmus of conduction (CIC) in LAMRT circuits outside of tachycardia episodes. Peak frequency (PF) mapping, with its ability to discern near-field (NF) from far-field (FF) electrograms (EGMs) in low voltage areas, emerges as a valuable tool for precisely identifying these critical isthmuses. Purpose This study aims to investigate whether the accurate identification of the CIC in LAMRT circuits is achievable through PF mapping during sinus rhythm or coronary sinus pacing. Methods Patients with sustained LAMRT undergoing radiofrequency (RF) ablation were enrolled. Utilizing a 16-pole grid catheter (HD-Grid), bipolar voltage and activation maps were generated during LAMRT. PF maps were retrospectively computed. Voltage, activation, and PF maps were also created during sinus rhythm and coronary sinus pacing (500 ms). Potential CICs (P-CICs) were defined as areas with low voltage (&amp;lt;0.2 mV) and high PF (&amp;gt;250 Hz), covering a surface area of &amp;lt;2 cm2 by adjusting the PF threshold above 250 Hz. Only instances of LAMRT terminated by focal RF lesions (boundary &amp;lt;1.5 cm diameter) were included. Confirmed CICs (C-CICs) were identified at sites where LAMRT termination occurred due to RF application. The localization of P-CICs found during LAMRT, sinus rhythm (SR), and coronary sinus pacing (CSP) mapping, in relation to that of CIC, was analyzed, considering them matching if separated by &amp;lt;10 mm. Results Twenty-four consecutive patients with 26 atrial tachycardias (ATs) were prospectively enrolled, including 18 LAMRTs (270±63 ms) terminated by 2.2±2.9 focal RF lesions after 9.4±8.2 sec of energy delivery. A P-CIC was consistently identified at the tachycardia termination site during LAMRT mapping, with a visual cutoffs discrimination score (1-5) of 4.1±0.7, a mean P-P voltage cutoff &amp;lt;0.22±0.09 mV, and a mean PF cutoff &amp;gt;330±67 Hz in all patients. Importantly, P-CICs found during SR and CSP mapping matched those found during LAMRT mapping in all patients (figure). Conclusion PF mapping demonstrates precision in identifying the critical isthmus in LAMRT circuits during actual tachycardia episodes. Notably, the consistent identification of the CIC through PF mapping during sinus rhythm or coronary sinus pacing exhibits a high correlation with findings during LAMRT mapping. This approach holds promising potential for reducing arrhythmia recurrences, especially in scenarios involving multiple or unmappable LAMRTs.

Cardiac radiotherapy transiently alters left ventricular electrical properties and induces cardiomyocyte-specific ventricular substrate changes in heart failure.

Ongoing clinical trials investigate the therapeutic value of stereotactic cardiac radioablation (cRA) in heart failure patients with ventricular tachycardia. Animal data indicate an effect on local cardiac conduction properties. However, the exact mechanism of cRA in patients remains elusive. Aim of the current study was to investigate in vivo and in vitro myocardial properties in heart failure and ventricular tachycardia upon cRA. High-density 3D electroanatomic mapping in sinus rhythm was performed in a patient with a left ventricular assist device and repeated ventricular tachycardia episodes upon several catheter-based endocardial radio-frequency ablation attempts. Subsequent to electroanatomic mapping and cRA of the left ventricular septum, two additional high-density electroanatomic maps were obtained at 2- and 4-month post-cRA. Myocardial tissue samples were collected from the left ventricular septum during 4-month post-cRA from the irradiated and borderzone regions. In addition, we performed molecular biology and mitochondrial density measurements of tissue and isolated cardiomyocytes. Local voltage was altered in the irradiated region of the left ventricular septum during follow-up. No change of local voltage was observed in the control (i.e. borderzone) region upon irradiation. Interestingly, local activation time was significantly shortened upon irradiation (2-month post-cRA), a process that was reversible (4-month post-cRA). Molecular biology unveiled an increased expression of voltage-dependent sodium channels in the irradiated region as compared with the borderzone, while Connexin43 and transforming growth factor beta were unchanged (4-month post-cRA). Moreover, mitochondrial density was decreased in the irradiated region as compared with the borderzone. Our study supports the notion of transiently altered cardiac conduction potentially related to structural and functional cellular changes as an underlying mechanism of cRA in patients with ventricular tachycardia.

Comparison of voltages between atria: differences in sinus rhythm and atrial fibrillation

BackgroundUltra high-density mapping systems allow for comparison of atrial electroanatomical maps in unprecedented detail. Atrial scar determined by voltages and surface area between atria, rhythm and atrial fibrillation (AF) types was assessed.MethodsLeft (LA) and right atrial (RA) maps were created using Rhythmia HDx in patients listed for ablation for paroxysmal (PAF, sinus rhythm (SR) maps only) or persistent AF (PeAF, AF and SR maps). Electrograms on corresponding SR/AF maps were paired for direct comparison. Percentage surface area of scar was assigned low- (LVM, ≤ 0.05 mV), intermediate- (IVM, 0.05–0.5 mV) or normal voltage myocardium, (NVM, > 0.5 mV).ResultsThirty-eight patients were recruited generating 96 maps using 913,480 electrograms. Paired SR-AF bipolar electrograms showed fair correlation in LA (Spearman’s ρ = 0.32) and weak correlation in RA (ρ = 0.19) and were significantly higher in SR in both (LA: 0.61 mV (0.20–1.67) vs 0.31 mV (0.10–0.74), RA: 0.68 mV (0.19–1.88) vs 0.47 mV (0.14–1.07), p < 0.0005 both). Voltages were significantly higher in patients with PAF over PeAF, (LA: 1.13 mV (0.39–2.93) vs 0.52 mV (0.16–1.49); RA: 0.93 mV (0.24–2.46) vs 0.57 mV (0.17–1.69)). Minimal differences were seen in electrogram voltages between atria.Significantly more IVM/LVM surface areas were seen in AF over SR (LA only, p < 0005), and PeAF over PAF (LA: p = 0.01, RA: p = 0.04). There was minimal difference between atria within patients.ConclusionsUltra high-density mapping shows paired electrograms correlate poorly between SR and AF. SR electrograms are typically (but not always) larger than those in AF. Patients with PeAF have a lower global electrogram voltage than those with PAF. Electrogram voltages are similar between atria within individual patients.

Sinus rhythm QRS morphology reflects right ventricular activation and anatomical ventricular tachycardia isthmus conduction in repaired tetralogy of Fallot

Patients with repaired tetralogy of Fallot (TOF) are at risk for ventricular tachycardia (VT) related to well-described anatomical isthmuses. The purpose of this study was to explore QRS morphology as an indicator of anatomical isthmus conduction. Patients with repaired TOF and complete right bundle branch block referred for transcatheter pulmonary valve replacement (PVR) or presenting with sustained VT underwent comprehensive 3-dimensional mapping in sinus rhythm. Electrocardiographic characteristics were compared to right ventricular (RV) activation and anatomical isthmus conduction properties. Twenty-two patients (19 pre-pulmonary valve replacement and 3 clinical VT) underwent comprehensive 3-dimensional mapping (median 39 years; interquartile range [IQR] 27-48 years; 12 [55%] male). Septal RV activation (median 40 ms; IQR 34-46 ms) corresponded to the nadir in lead V1 and free wall activation (median 71 ms; IQR 64-81 ms) to the transition point in the upstroke of the R' wave. Patients with isthmus block between the pulmonary annulus and the ventricular septal defect patch and between the ventricular septal defect patch and the tricuspid annulus (when present), were more likely to demonstrate lower amplitude R' waves in lead V1 (5.8 mV vs 9.4 mV; P = .005), QRS fragmentation in lead V1 (15 [94%] vs 2 [13%]; P < .001), and terminal S waves in lead aVF (15 [94%] vs 6 [40%]; P < .001) than those with intact conduction. During catheter ablation, these QRS changes developed during isthmus block. For patients with repaired TOF, the status of septal isthmus conduction was evident from sinus rhythm QRS morphology. Low-amplitude, fragmented R' waves in lead V1 and terminal S waves in the inferior leads were related to septal isthmus conduction abnormalities, providing a mechanistic link between RV activation and common electrocardiographic findings.

Differences in atrial substrate localization using late gadolinium enhancement-magnetic resonance imaging, electrogram voltage, and conduction velocity: a cohort study using a consistent anatomical reference frame in patients with persistent atrial fibrillation.

Electro-anatomical voltage, conduction velocity (CV) mapping, and late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) have been correlated with atrial cardiomyopathy (ACM). However, the comparability between these modalities remains unclear. This study aims to (i) compare pathological substrate extent and location between current modalities, (ii) establish spatial histograms in a cohort, (iii) develop a new estimated optimized image intensity threshold (EOIIT) for LGE-MRI identifying patients with ACM, (iv) predict rhythm outcome after pulmonary vein isolation (PVI) for persistent atrial fibrillation (AF). Thirty-six ablation-naive persistent AF patients underwent LGE-MRI and high-definition electro-anatomical mapping in sinus rhythm. Late gadolinium enhancement areas were classified using the UTAH, image intensity ratio (IIR >1.20), and new EOIIT method for comparison to low-voltage substrate (LVS) and slow conduction areas <0.2 m/s. Receiver operating characteristic analysis was used to determine LGE thresholds optimally matching LVS. Atrial cardiomyopathy was defined as LVS extent ≥5% of the left atrium (LA) surface at <0.5 mV. The degree and distribution of detected pathological substrate (percentage of individual LA surface are) varied significantly (P < 0.001) across the mapping modalities: 10% (interquartile range 0-14%) of the LA displayed LVS <0.5 mV vs. 7% (0-12%) slow conduction areas <0.2 m/s vs. 15% (8-23%) LGE with the UTAH method vs. 13% (2-23%) using IIR >1.20, with most discrepancies on the posterior LA. Optimized image intensity thresholds and each patient's mean blood pool intensity correlated linearly (R2 = 0.89, P < 0.001). Concordance between LGE-MRI-based and LVS-based ACM diagnosis improved with the novel EOIIT applied at the anterior LA [83% sensitivity, 79% specificity, area under the curve (AUC): 0.89] in comparison to the UTAH method (67% sensitivity, 75% specificity, AUC: 0.81) and IIR >1.20 (75% sensitivity, 62% specificity, AUC: 0.67). Discordances in detected pathological substrate exist between LVS, CV, and LGE-MRI in the LA, irrespective of the LGE detection method. The new EOIIT method improves concordance of LGE-MRI-based ACM diagnosis with LVS in ablation-naive AF patients but discrepancy remains particularly on the posterior wall. All methods may enable the prediction of rhythm outcomes after PVI in patients with persistent AF.

Utility of Substrate Mapping Using Extrasystole to Localise Comprehensive Ventricular Tachycardia Circuits: Results From Intra-operative Mapping Studies.

Substrate mapping-based identification of all ventricular tachycardia (VT) circuits (diastolic activation), including partial and complete diastolic circuits in clinical and nonclinical VT, could be beneficial in guiding VT ablation to prevent VT recurrence. The utility of extrasystole induced late potentials has not been compared with late potentials in sinus rhythm (SR) and right ventricular pacing (RVp). Intraoperative simultaneous panoramic endocardial mapping of 21 VTs in 16 ischemic heart disease patients was performed with the use of a 112-bipole endocardial balloon. The decrement of near-field electrogram later than surface QRS during extrasystole (eLP) was studied. Patients had a mean age of 52 ± 9 years and were predominantly (75%) male. The mean sensitivity of eLP (0.75 [95% confidence interval [CI] 0.72-0.78]) to detect VT circuits was better than SR (0.33 [0.30-0.36]; P < 0.001) and RVp (0.36 [0.33-0.39]; P < 0.001) without significant differences in specificity, eLP (0.77 [0.74-0.81], SR (0.82 [0.80-0.84]; P= 0.23), and RVp (0.81 [0.78-0.83]; P= 0.11). Both negative (NPV) and positivie (PPV) predictive values were significantly better for eLP mapping. The mean NPV was 0.77 (95% CI 0.74-0.81), 0.57 (0.55-0.59), and 0.58 (0.55-0.61) for eLP, SR, and RVp, respectively (P < 0.0001). PPV was 0.75 (95% CI 0.72-0.78), 0.63 (0.59-0.67), and 0.63 (0.59-0.67) for eLP, SR, and RVp, respectively (P < 0.001). Overall diagnostic performance (area under the receiver operating characteristic curve) was significantly better for eLP (0.85 [95% CI 0.80-0.90] compared with SR (0.63 [0.56-0.72]; P < 0.001) or RVp (0.61 [0.52-0.74]; P < 0.001). Evoked late potential mapping is a better tool to detect comprehensive diastolic circuits activated during VT, compared with eLP mapping in sinus rhythm or RV pacing.

Spatial correlation of left atrial low voltage substrate in sinus rhythm versus atrial fibrillation: The rhythm specificity of atrial low voltage substrate.

Improved sinus rhythm (SR) maintenance rates have been achieved in patients with persistent atrial fibrillation (AF) undergoing pulmonary vein isolation plus additional ablation of low voltage substrate (LVS) during SR. However, voltage mapping during SR may be hindered in persistent and long-persistent AF patients by immediate AF recurrence after electrical cardioversion. We assess correlations between LVS extent and location during SR and AF, aiming to identify regional voltage thresholds for rhythm-independent delineation/detection of LVS areas. (1) Identification of voltage dissimilarities between mapping in SR and AF. (2) Identification of regional voltage thresholds that improve cross-rhythm substrate detection. (3) Comparison of LVS between SR and native versus induced AF. Forty-one ablation-naive persistent AF patients underwent high-definition (1 mm electrodes; >1200 left atrial (LA) mapping sites per rhythm) voltage mapping in SR and AF. Global and regional voltage thresholds in AF were identified which best match LVS < 0.5 mV and <1.0 mV in SR. Additionally, the correlation between SR-LVS with induced versus native AF-LVS was assessed. Substantial voltage differences (median: 0.52, interquartile range: 0.33-0.69, maximum: 1.19 mV) with a predominance of the posterior/inferior LA wall exist between the rhythms. An AF threshold of 0.34 mV for the entire left atrium provides an accuracy, sensitivity and specificity of 69%, 67%, and 69% to identify SR-LVS < 0.5 mV, respectively. Lower thresholds for the posterior wall (0.27 mV) and inferior wall (0.3 mV) result in higher spatial concordance to SR-LVS (4% and 7% increase). Concordance with SR-LVS was higher for induced AF compared to native AF (area under the curve[AUC]: 0.80 vs. 0.73). AF-LVS < 0.5 mV corresponds to SR-LVS < 0.97 mV (AUC: 0.73). Although the proposed region-specific voltage thresholds during AF improve the consistency of LVS identification as determined during SR, the concordance in LVS between SR and AF remains moderate, with larger LVS detection during AF. Voltage-based substrate ablation should preferentially be performed during SR to limit the amount of ablated atrial myocardium.

Role of diagnosis-to-ablation time in paroxysmal atrial fibrillation: preliminary results of the MULTI AF trial

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Diagnosis-to-ablation time (DAT) has been already defined as a predictor of atrial fibrillation (AF) ablation outcome. AF promotes pathological atrial remodelling at electrical, cellular, and structural levels. The aims of this study were to determine the role of DAT in atrial electrical remodelling and its impact on AF recurrencies. Methods Between January 2020 and February 2022, 122 patients (62% male, age 63.5±10.8 y) underwent pulmonary veins isolation (PVI) for paroxysmal atrial fibrillation in 7 Italian centres. For each patient, a high-density bipolar voltage map (BVM) of the left atrium (LA) was acquired by sequential multielectrode mapping in sinus rhythm through the Pentaray™ Catheter and the CARTO3® mapping system. More than 200 voltage points per map were acquired in different segments of the LA (posterior, anterior, lateral, superior, septal and inferior ). The procedural endpoint was PVI by circumferential ablation around the pulmonary vein antra. On top of PVI no "adjunctive" ablations, were performed. All patients were monitored as outpatients for AF recurrence. Results For the 122 patients enrolled the mean DAT was 37.6±35.2 months. Two groups were identified according to DAT: 51 patients in Group A with DAT ≤ 12 months and 71 patients in Group B with DAT &amp;gt; 12 months. The two groups have similar clinical, electrocardiographic and echocardiographic characteristics. Intraprocedural pulmonary vein isolation was achieved in all patients. At the high-density left atrial BVM a concealed electrical remodelling was detected in group B in each LA segment (Fig.1), with the mean global LA voltage amplitude significantly lower in patients with DAT&amp;gt;12 months (group A 2.32±0.81 mV vs group B 1.47±0.74 mV, p&amp;lt;0.01). After a median follow-up of 11.9±9.4 months, 14 patients (11.4%) had AF recurrencies following the first ablation procedure. A significant lower rate of AF recurrence was found among patients with DAT &amp;lt; 12 months (Fig. 2): 2 patients in group A vs 12 patients in group B (4% vs 18.2%, p&amp;lt;0.01). Conclusion Patients with paroxysmal atrial fibrillation with DAT&amp;gt;12 months have significantly lower bipolar LA voltages, revealing a concealed atrial remodelling. Furthermore, DAT&amp;gt;12 months is associated with poor AF ablation outcome.

A new workflow including Coherent algorithm in sinus rhythm for the treatment of Ventricular Tachycardia in patients with scar related heart disease

Abstract Funding Acknowledgements Type of funding sources: None. Background Catheter ablation is a well establish therapy in patients with structural heart disease (SHD) and sustain ventricular tachycardia (VT). Scar substrate modification is one of the two endpoint of a VT ablation procedure. Dechanneling is one of the described successful techniques that shown to be effective for substrate modification Aim This is a pilot study aiming to evaluate the feasibility and the acute efficacy of a new mapping approach for VT ablation with the combination of high density (HD) mapping and Coherent mapping algorithm. Methods All enrolled patients underwent radio frequency catheter ablation (RFCA) for drug-refractory VT or VT storm. Before mapping, programmed ventricular stimulation was performed in all patients for the induction of clinical VT or any other ventricular arrhythmias (VA), if VA was inducible, then electrical cardioversion was conducted to restore sinus rhythm. After transseptal puncture, left ventricular (LV) HD mapping was conducted using a 3D mapping system aiming &amp;gt;5000 mapping points during sinus rhythm, intrinsic atrial rhythm, or ventricular pacing with a multielectrode catheter. During HD mapping, all late potentials (LPs) were tagged as double potentials (DP) and all potentials below 0,2 mV were tagged as scar. Then, Coherent mapping was used to visualize electrical propagation through the LV, based on velocity vector identification, highlighting how the electrical signal enters the scar and identifying the "entrance points" (EP). RFCA was delivered in a power-controlled mode on all the individuated EPs using an open, irrigated-tip ablation catheter with contact force sensor. After RFCA, a second remap was conducted to evaluate the LPs abolition. Then, a programmed ventricular stimulation was performed to validate non inducibility of any VAs. Results 10 consecutive patients (age 71,25±10,32 years, 100% male) undergoing RFCA for drug-refractory VT or VT storm (50%). Acute procedural end-point were: abolition of the LPs and non-inducibility of any VA at the end of the procedure. Abolition of LPs was reached in all cases while non inducibility was reached in 9 patients (90%). Mean procedural time was 214±33,81 min, mean mapping time was 89±15,40 min with mean number of acquired points of 5218±359,56. Mean fluoroscopy time and dose were 15±33,81 min and 5218±7149,8 µGm2, respectively. Mean entrance points identified was 2,6±0,84. In 5 patents (50%), after ablation a modification in the refractory period of the left ventricular myocardium was observed. Mean RF time was 1216±565,46 seconds, with mean number of Visitag of 33±29,98. No acute complication were reported. Conclusion High-density mapping in sinus rhythm combined with Coherent algorithm facilitates the understanding of the substrate and provides targets for effective ablation. This approach has been proven safe and with high acute success rates.

Assessment of scar between atria, rhythms and atrial fibrillation types: does ultra high density mapping offer new insights?

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Boston Scientific Background 3D electroanatomical mapping systems demonstrate atrial scar by recording local tissue voltages as a surrogate. Increased scar has been shown with both progression of atrial fibrillation, (AF, paroxysmal (PAF) to persistent (PeAF)), and between sinus rhythm (SR) and AF on low density mapping systems. The introduction of ultra high density mapping allows a more detailed comparison. Objectives Assessment of atrial scar determined by voltages and surface area between atria, rhythm, and AF type. Methods Ultra high density 3D electroanatomical maps of left and right atria (LA, RA) were created. PeAF patients had maps created in AF and SR following DC cardioversion. PAF patients had maps created in SR only. Electrograms (EGMs) on corresponding AF and SR maps were paired using exported co-ordinates. Percentage surface area of scar was and assigned as low voltage myocardium (LVM, ≤ 0.05mV), intermediate, (IVM, 0.05 - 0.5mV), or normal, (NVM, &amp;gt; 0.5mV). Results 95 maps were produced using 913480 EGMs. Paired SR-AF EGM voltages had a moderate correlation in the LA (Bipolar: Pearson’s R = 0.32, unipolar: R = 0.36, both p &amp;lt;0.0005), and weak correlation in the RA, (Bipolar: R = 0.19, unipolar: R = 0.25, both p &amp;lt; 0.0005). Paired voltages were significantly higher in SR in both atria, LA/RA, bipolar/unipolar all p &amp;lt; 0.0005). There was significantly more LVM/IVM percentage surface area in AF over SR in the LA, (SR to AF - LVM: 6.4 ± 6.9 to 12.2 ± 9.5; IVM 41.0 ± 12.1 to 50.5 ± 10.0; NVM: 51.7 ±17.2 to 37.3 ± 16.1, p &amp;lt; 0.0005), but not in the RA (SR to AF – LVM: 6.5 ± 5.3 to 8.4 ± 8.3; IVM 42.0 ± 10.1 to 44.6 ± 6.9;NVM: 51.5 ± 13.6 to 47.0 ± 13.8, p = 0.62) Figure 1A. Global tissue voltages in SR were significantly higher in PAF over PeAF in both atria, (LA –bipolar: 1.13 vs 0.52mV, unipolar 1.96 vs 1.44mV, RA – bipolar 0.93 vs 0.57mV, unipolar: 1.68 vs 1.33mV all p &amp;lt; 0.0005). There was significantly more LVM/IVM surface area demonstrated in PeAF over PAF in the LA, (PAF to PeAF - LVM: 0.6 ± 0.7 to 6.6 ± 6.8; IVM 29.5 ± 12.3 to 43.1 ±11.4; NVM: 69.8 ± 12.8 to 50.3 ± 16.4, p = 0.01), but not in the RA, (PAF to PeAF - LVM: 4.6 ± 3.6 to 6.5 ± 5.3; IVM 32.7 ± 9.5 to 42.0 ±10.1; NVM: 62.7 ± 12.1 to 51.5 ± 13.6, p = 0.20). Figure 1B Comparing atria, the LA had a significantly lower voltage in SR, but this difference was small (LA/RA = 0.89, p &amp;lt; 0.0005). The percentage surface area of scar was comparable, (LA to RA - LVM: 4.0 ± 5.6 to 5.6 ± 4.5; IVM: 38.4 ± 37.6 to 37.6 ± 10.6; NVM: 57.5 ±18.4 to 56.8 ± 13.8). Figure 1C Conclusions Ultra high density mapping confirms atrial voltages are higher in SR over AF, and PAF over PeAF. The RA is comparable to the LA for tissue voltages but does not demonstrate a change in surface area of scar between AF and SR or PAF and PeAF. This may reflect the complexity of AF wavefronts in the LA compared to the RA leading to more bipole orientation related overestimation of scar in the fibrillating LA.

Functional mapping: a new approach for substrate characterization in patients affected by atrial fibrillation

Abstract Funding Acknowledgements Type of funding sources: None. Background The ongoing challenge is to generate meaningful data during electrophysiological (EP) studies, integrating the knowledge on atrial fibrillation (AF) progression gained by the EP community in the latest years. At the present time there is a lack of EP protocols: most of the centers perform electroanatomical (EA) ablation to isolate pulmonary veins or, in persistent AF forms, some centers propose the performance of additional lines for atrial compartmentalization. However, none of these approaches take in consideration neither the wavefront propagation nor the analysis of functional phenomena. Purpose To investigate whether zones of delayed conduction (slow conduction, SC) or functional propagation (pivot sites, PS) may play a role in terms of maintenance of paroxysmal (PAF) and persistent (PsAF) AF. Methods Twenty-seven consecutive patients with PAF (14 patients) and PsAF (13 patients) have been enrolled in this study. For each patient, a sinus rhythm activation map and a paced map have been created with a multipolar catheter exploiting the parallel mapping feature. According to these activation maps, we analyzed the wavefront propagation. Abnormal conduction was defined as a delimited zone in which the propagation became suddenly slower (&amp;lt;0.5 m/s, slow conduction corridors) or changed in direction (&amp;gt;90°, pivot sites). At each of these sites, EGMs were collected and analysed in terms of amplitude (mV), location and fractionation. Results In sinus rhythm maps, a total number of 65 pivot sites and slow conduction corridors was identified. In the PAF group 22 PS and SC were found (1,6/pt), whereas those included in the PsAF one showed a significantly higher number: 43 (3,3/pt). The bipolar voltage value reported at abnormal conduction areas amounted to 1,95 ± 0,93 mV and 1,78 ± 0,54 mV for PAF and PsAF patients, respectively, showing a lower value with respect to healthy tissue areas (2,94 ± 4,81 mV). More than four deflections per signal were identified in 57/65 PS and SC zones. In PsAF cases, these areas were mainly found on the posterior wall. A concordance with esophagus location occurred in the 89%. In paced maps, instead, we documented an average value of 38 PS and SC zones (1,5/pt), of which 27 in persistent patients. As for bipolar values, a lower voltage value was reported in PS and SC zones (1,91 ± 0,69 mV for PAF and 1,52 ± 0,36 mV for PsAF) with respect to normal conductive tissue. Fractionation of EGMs was confirmed in almost all cases. Conclusion The main findings of this analysis are: (i) in PsAF patients the number of pivot sites is higher with respect to PAF cases; (ii) In PsAF patients, abnormal conduction phenomena are predominantly localized on the posterior wall, with a strong correlation with esophagus location; (iii) slow conduction zones and pivot sites are characterized by lower voltage amplitude and higher fractionation with respect to normal conduction areas.

In Atrial Fibrillation, Omnipolar Voltage Maps More Accurately Delineate Scar Than Bipolar Voltage Maps

BackgroundOptimal method for voltage assessment in AF remains unclear. ObjectivesThis study evaluated different methods for assessing atrial voltage and their accuracy in identifying pulmonary vein reconnection sites (PVRSs) in atrial fibrillation (AF). MethodsPatients with persistent AF undergoing ablation were included. De novo procedures: voltage assessment in AF with omnipolar voltage (OV) and bipolar voltage (BV) methodology and BV assessment in sinus rhythm (SR). Activation vector and fractionation maps were reviewed at voltage discrepancy sites on OV and BV maps in AF. AF voltage maps were compared with SR BV maps. Repeat ablation procedures: OV and BV maps in AF were compared to detect gaps in wide area circumferential ablation (WACA) lines that correlated with PVRS. ResultsForty patients were included: 20 de novo and 20 repeat procedures. De novo procedure: OV vs BV maps in AF; average voltage 0.55 ± 0.18 mV vs 0.38 ± 0.12 mV; P = 0.002, voltage difference of 0.20 ± 0.07 mV; P = 0.003 at coregistered points and proportion of left atrium (LA) area occupied by low-voltage zones (LVZs) was smaller on OV maps (42.4% ± 12.8% OV vs 66.7% ± 12.7% BV; P < 0.001). LVZs identified on BV maps and not on OV maps correlated frequently to wavefront collision and fractionation sites (94.7%). OV AF maps agreed better with BV SR maps (voltage difference at coregistered points 0.09 ± 0.03 mV; P = 0.24) unlike BV AF maps (0.17 ± 0.07 mV, P = 0.002). Repeat ablation procedure: OV was superior in identifying WACA line gaps that correlated with PVRS than BV maps (area under the curve = 0.89, P < 0.001). ConclusionsOV AF maps improve voltage assessment by overcoming the impact of wavefront collision and fractionation. OV AF maps correlate better with BV maps in SR and more accurately delineate gaps on WACA lines at PVRS.

C5 FUNCTIONAL MAPPING: A NEW APPROACH FOR SUBSTRATE CHARACTERIZATION IN PATIENTS AFFECTED BY ATRIAL FIBRILLATION

Abstract Background The ongoing challenge is to generate meaningful data during electrophysiological (EP) studies, integrating the knowledge on atrial fibrillation (AF) progression gained by the EP community in the latest years. At the present time there is a lack of EP protocols and none of the most used approaches take in consideration neither the wavefront propagation nor the analysis of functional phenomena. Purpose. To investigate whether zones of delayed conduction (slow conduction, SC) or functional propagation (pivot sites, PS) may play a role in terms of maintenance of paroxysmal (PAF) and persistent (PsAF) AF. Methods Twenty–seven consecutive patients with PAF (14 patients) and PsAF (13 patients) have been enrolled in this study. For each patient, a sinus rhythm activation map and a paced map have been created. Abnormal conduction was defined as a delimited zone in which the propagation became suddenly slower (slow conduction zones) or changed its direction (pivot sites). At each of these sites, EGMs were collected and characterized in terms of amplitude (mV), location and fractionation. Results In sinus rhythm maps, a total number of 65 pivot sites and slow conduction corridors was identified. In the PAF group 22 PS and SC were found (1,6/pt), whereas those included in the PsAF one showed a significantly higher number: 43 (3,3/pt). The bipolar voltage value reported at abnormal conduction areas amounted to 1,95 ± 0,93 mV and 1,78 ± 0,54 mV for PAF and PsAF patients, respectively, showing a lower value with respect to healthy tissue areas (2,94 ± 4,81 mV). More than four deflections per signal were identified in 57/65 zones. In PsAF cases, these areas were mainly found on the posterior wall. A concordance with esophagus location occurred in the 89%. In paced maps, instead, we documented an average value of 38 PS and SC zones (1,5/pt), of which 27 in persistent patients. As for bipolar values, a lower voltage value was reported in PS and SC zones. Fractionation of EGMs was confirmed in almost all cases. Conclusion The main findings of this analysis are: (i) in PsAF patients the number of pivot sites is higher with respect to PAF cases; (ii) In PsAF patients, abnormal conduction phenomena are predominantly localized on the posterior wall, with a strong correlation with esophagus location; (iii) slow conduction zones and pivot sites are characterized by lower voltage amplitude and higher fractionation with respect to normal conduction areas.

PO-04-158 INTRACARDIAC ECHOCARDIOGRAPHY GUIDES ANATOMICAL ISTHMUS ABLATION IN PATIENTS WITH VENTRICULAR TACHYCARDIA AND REPAIRED TETRALOGY OF FALLOT

Successful catheter ablation of monomorphic ventricular tachycardia (VT) in patients with repaired Tetralogy of Fallot (TOF) can be achieved by targeting one or more of four common anatomical isthmuses. However, variability in the size and location of surgical patches means careful mapping is required to design ablation lines to block the critical isthmus. Intracardiac echocardiography (ICE) may assist ablation by accurate identification of individual TOF anatomy. To determine whether the routine use of ICE aids linear ablation of VT isthmuses in patients with repaired TOF. Retrospective study of repaired TOF patients undergoing VT ablation at our centre from January 2017 to November 2022. Cases were divided into those which used ICE to assist anatomical mapping versus those which used voltage mapping to identify patches and valve annuli. Once anatomy was defined, we started with a VT stimulation study where haemodynamically stable VTs were mapped. Non-inducible or unstable VTs underwent substrate mapping in sinus rhythm. All cases underwent ablation and had no inducible monomorphic VT as the endpoint. Data are presented as median and [interquartile range]. Twenty-six patients were identified, of which 15 were guided by ICE. The baseline demographic data is presented in the table and a representative figure shows the use of ICE to identify surgical patches. The use of ICE allowed linear ablation of the critical anatomical isthmus in 12/15 patients (80%) compared to 4/11 (36%) without ICE (p=0.023). The remaining patients without linear ablation underwent substrate-based ablation only to sites of local abnormal ventricular activity. There was no significant difference in overall procedure time (ICE: 165 [60] minutes versus no ICE: 145 [50] minutes; p=0.24), nor in fluoroscopy time (ICE: 25 [17] minutes versus no ICE: 31 [16] minutes; p=0.9). Over time, the introduction of ICE was associated with improved workflow. When comparing the first and last five cases using ICE, both median procedure times (from 196 to 160 minutes) and fluoroscopy times (from 35 to 20 minutes) were shorter. Intracardiac echocardiography improves targeted linear ablation of the critical anatomical isthmus for VT in patients with repaired TOF. ICE provides real-time individualised identification of surgical patches and valve anatomy to guide optimal linear lesion sets across isthmuses, with routine use over time showing a trend towards shorter procedural and fluoroscopy times.Tabled 1Baseline demographicsICE (n=15)No ICE (n=11)Age (years)53 [26]41 [23]Male10 (67%)7 (64%)Number of sternotomies2 [1]3 [2]History of syncope5 (33%)1 (9%)QRS width (milliseconds)176 [59]172 [54]Left ventricular ejection fraction (%)50 [25]54 [9]Right ventricular ejection fraction (%)29 [8]27 [7]Implantable cardiac defibrillator7 (47%)5 (45%)History of sustained VT12 (80%)8 (73%)VT ablation15 (100%)11 (100%)Inducible VT at electrophysiology study11 (73%)6 (55%)Linear anatomical isthmus ablation12 (80%)4 (36%)Procedure time (minutes)165 [60]145 [50]Fluoroscopy time (minutes)25 [17]31 [16] Open table in a new tab

EN-452414-1 IMPACT OF MULTI-DIRECTIONAL PACING ON LATE SIGNAL ACTIVATION, ACTIVATION SLOWING AND REPOLARIZATION GRADIENTS TO LOCALIZE RE-ENTRANT VENTRICULAR TACHYCARDIA CIRCUITS IN A PORCINE INFARCT MODEL.

Optimal signal parameters and substrate mapping strategies for identifying key arrhythmogenic sites in ventricular tachycardia (VT) ablation are not established. To evaluate multi-directional pacing on the distribution of late signal activation, activation slowing and repolarization gradients in relation to critical sites of re-entrant VT, in a porcine infarct model. Electrophysiology studies were performed 4 weeks post-infarction in 13 pigs using the EnSite Precision system (Abbott, IL, USA), and the Advisor HD Grid (Abbott) multi-electrode catheter. Substrate maps were created during right ventricular (RV), left ventricular (LV), and biventricular pacing (BIV), and sinus rhythm (SR). Sites of early, mid-, and late-diastolic signals of induced VT’s were delineated. Off-line analysis compared these critical VT sites to algorithmically identified 20 most vulnerable sites of latest activation timing within and post-QRS, and the largest activation (GradAT) and activation recovery interval gradients (GradARI). 34 VTs were mapped with at least one diastolic recorded component, with a mean tachycardia cycle length of 236.5 ± 32.4 ms. 48 sinus rhythm and pacing maps were obtained, 10 using BIV pacing (mean points 375 ± 263), 13 using LV pacing (mean points 610 ± 334), 13 from RV pacing (mean points 603 ± 263) and 12 in sinus rhythm (mean points 1078 ± 654). Late potential (LP) mapping in sinus rhythm was taken as the established clinical standard for statistical comparison with all other protocols, displayed in Figure 1. GradARI using RV pacing provided the closest localization for VT exit and entrance, with a median distance of 10.6mm (IQR 5.0mm, p <0.05) and median 9.4mm (IQR 8.0mm, p <0.05) compared to LP in sinus rhythm, respectively. LAT with BIV pacing provided closest VT isthmus localization for VT isthmus, with a median of 5.5mm (IQR 7.15mm, p <0.05) compared to LP in sinus rhythm (Figure 1). A global sensitivity and specificity analysis was performed on all points. GradARI mapping in SR reported the highest AUC (area – under curve) for early diastolic VT signals (AUC 0.96, sensitivity 93%, specificity 91%), mid-diastolic signals (AUC 0.92, sensitivity 84%, specificity 88%) and late diastolic signals (AUC 0.92, sensitivity 88%, specificity 84%). Sites with the largest ARI gradients in sinus rhythm best predict critical sites of VT in this model, with the most effective protocol being RV pacing examining ARI gradients.

PO-05-040 APPLICATION OF ELECTROGRAM PEAK FREQUENCY VALUE FOR IDENTIFICATION OF SCAR-RELATED VENTRICULAR TACHYCARDIA ISTHMUS DURING SINUS RHYTHM

Isolated late activation mappings (ILAMs) can identify possible ventricular tachycardia (VT) isthmus during sinus rhythm (SR). The interference of far-field potentials at the deceleration zone (DZ) may cause misleading results. Electrogram peak frequency (PF) has the potential to discriminate between far-field and near-field signals. We aimed to identify the VT isthmus by applying PF over SR substrate maps. Ten patients with scar-related VT (ischemic/nonischemic cardiomyopathy 6/4) were studied. VT isthmuses were identified based on the activation maps, entrainment, and ablation results during tachycardia. The accuracy of PF maps in detecting potential VT isthmuses during SR before ablation was assessed. Twelve VT isthmuses were identified. The bipolar mean voltage and PF of isthmus areas over the pre-ablation SR map were 0.25 ± 0.12 mV and 307.5 ± 54.3 Hz, respectively. All isthmuses were within low voltage zones (LVZ) with PF of more than 250Hz. Before ablation, 11 of 25 (44.0%) DZs identified from ILAM by annotating the last deflection EGMs in LVZ were compatible with VT isthmuses (mean PF 311.0 ± 66.0Hz); mean PF of DZs which were not isthmus locations was 177.6 ± 51.5 Hz. There were 12 of 15 (80.0%) DZs on ILAMs constructed by annotating PF EGMs compatible with VT isthmuses. VT isthmus is mostly located in LVZ (<0.5 mV) with PF value over 250Hz from pre-ablation SR maps. The DZs during SR with a low PF could be bystanders. Identifying DZs by annotating EGMs with PF, rather than last deflections, is better to discriminate critical VT substrates.