Conventional Activation Mapping Research Articles

Optimizing ablation sites in recurrent atrial fibrillation cases: a novel approach using emphasize settings

Abstract Backgrounds Although catheter ablation techniques for atrial fibrillation (AF) have advanced, a certain number of cases of re-conduction after pulmonary vein isolation (PVI) still exist and are the most common cause of recurrence of atrial tachyarrhythmias. In some cases, the diversity of anatomical wall thickness and fiber orientation around the PVs might contribute to re-conduction. Identification of optimal target ablation site of re-conduction could reduce unnecessary ablation and decrease the risk of complications. However, in cases where local electrograms consisted with far filed and near filed potentials were coexist, conventional activation mapping with bipolar electrograms sometimes fails to identify the re-conduction sites. Purpose We investigated the utility of using the Emphasize settings in the emphasis map obtained by combining activation mapping and peak frequency mapping in the EnSite X system to determine the optimal ablation sites compared to the conventional map based on the activation mapping. Methods Patients undergoing AF ablation of PVI with the EnSite X system who had recurrent cases or had PVI re-conduction at the initial ablation were included. We retrospectively analyzed the cases from January 2022 to November 2023. In all cases, bipolar voltage and activation maps for left atrium and PVs were obtained by a 16-pole grid catheter (Advisor HD Grid) during atrial pacing or sinus rhythm. Local activation timing and peak frequency maps of the left atrium were performed to obtain the Emphasize settings indicating the optimal ablation sites (E-group). The Emphasize settings obtained from the maps were adjusted to make the site of re-conduction most apparent (Figures). Another group determined the ablation sites based on the activation mapping (A-group). The clinical backgrounds, laboratory data, and echocardiography data were also evaluated. Intravenous administration of ATP was performed in all targeted PVs after successful re-isolation of PVs. Results Total 44 patients (69±10 years, 32 males) and 90 PVs were found to be re-conducted and analyzed. The gaps of 34 and 40 points of PVI were observed in the E-group and C-group, respectively. The number of needs for the ablation points to successful elimination of gap was markedly smaller in the E-group (1.3±0.7 vs. 6.2±3.2, p<0.001). The optimal Emphasize settings was 340 ±75 Hz in the E-group. None of the cases showed dormant conductions by ATP administration in both groups. There were no differences in age, gender, left atrial volume index, left ventricular ejection fraction, serum creatinine levels, and N-terminal pro-brain natriuretic peptide levels between the two groups. Conclusion The optimal ablation site was visualized by adjusting the Emphasize settings, and the number of ablation points to re-isolation of PV might be markedly reduced.

PO-01-106 ATRIAL ISOCHRONAL LATE ACTIVATION MAPPING KEEPS THE DIAPHRAGM ALIVE

Isochronal late activation mapping (ILAM) is a well-established mapping method for ventricular arrhythmias. However, the role of ILAM mapping during atrial arrhythmias is less clear. This case provides an example of ILAM use during right atrial flutter ablation using the high-density Optrell (Biosense Webster, CARTO) catheter in a patient with congenital heart disease. N/A N/A A 27-year-old female with D-transposition of the great arteries status post Nikaidoh (arterial switch operation with ventricular septal defect repair, pulmonary valve replacement, and typical atrial flutter status post ablation presented with SVT and was referred for catheter ablation. During EPS, conventional activation mapping of fleeting atrial flutter was attempted utilizing the Optrell catheter, which localized the region of interest to a large section of the inferior posterolateral RA, which also had diffuse phrenic nerve capture (figure 1, panel A). However, during periods of sinus rhythm, ILAM and voltage mapping was conducted that demonstrated a distinct, confined, region of isochronal crowding along the mid-posterolateral right atrium, distant from the phrenic nerve (figure 1, panel B). The ILAM site was addressed with catheter ablation rendering the atrial flutter non-inducible with preservation of phrenic nerve function. The patient has remained free of atrial arrhythmias in the 6 months period since the ablation. The application of ILAM is well-established for ventricular tachycardia, however, its role in atrial arrhythmias is less clear. ILAM may be especially useful in adults with congenital heart disease given the complexity of atrial arrhythmia and the benefit of ablation in this unique population. Novel high-density mapping catheters, such as Optrell, allow for rapid and granular voltage data and translate well to ILAM regions within the atrium. Application of ILAM within atrial substrate, particularly for congenital heart disease which predisposes to higher recurrence rates, may improve both recurrence rates and safety, like in this case where the use of this method allowed avoiding ablation on the phrenic nerve.

Stepwise mapping and ablation algorithm in patients undergoing ablation of unstable, unmappable scar-based atrial tachycardias.

Scar based atrial tachycardia (AT)'s usually presents with a complex electrophysiological substrate. It is not uncommon that multiple instable ATs are present in a single patient. The aim of this study was to analyze clinical and electrophysiological characteristics of patients who had undergone ablation for instable ATs, and report outcomes of the stepwise substrate ablation procedure during the follow-up. Patients scheduled to undergo AT ablation were screened for enrollment to the study. When instable ATs were diagnosed a stepwise mapping and ablation algorithm was applied to all patients. After the procedure, patients were clinically and electrocardiographically followed. Twenty-six patients were enrolled in the study. The mean number of ATs observed during the procedures is 3.1±0.7. At the end of the procedure, 18 (69.2%) patients had isolated posterior wall. Anterior mitral line ablation was successfully performed in 13 (50%), mitral isthmus line in 4 (15.4%), roof line in 4 (15.4%) patients. The mean follow-up was 13.5±5.4 months. During the follow-up period 6(23.1%) patients developed arrhythmia recurrence. A reasonable mid-term success can be expected in patients with instable ATs undergoing ablation according to the stepwise substrate modification algorithm, however due to extensive ablation it should be reserved for patients where conventional activation mapping cannot be performed.

Unique feature of novel activation mapping to identify the successful ablation site of atrial tachycardia

A 49-year-old man was referred to our hospital for catheter ablation of atrial tachycardia (AT; cycle length 360 ms). He previously underwent pulmonary vein isolation and cavotricuspid isthmus ablation for paroxysmal atrial fibrillation (AF). Conventional activation mapping with the high-density Rhythmia mapping system (Boston Scientific, Marlborough, MA) revealed the following features: (1) activation breaking out at the inferior wall below the left inferior pulmonary vein in a centrifugal pattern (Online Supplemental Figure 1) and (2) AF was observed inside the left pulmonary vein (LPV) (Figure 1A, a).

Multi-electrode mapping of complex macroreentry atrial tachycardia

BackgroundMulti-electrode mapping (MEM) is increasingly applied in ablation of complex atrial arrhythmias. This study aimed to evaluate MEM for analysis and treatment of complex macroreentry atrial tachycardia (MAT). MethodsPatients with MAT related to scarring, history of heart surgery or atrial linear ablation were studied. Patients were mapped with conventional activation mapping (CAM) or MEM. After characterizing the mechanism of atrial tachycardia (AT), the ablation was performed. ResultsThe study consisted of 114 eligible patients, 74 in the CAM and 40 in MEM. Compared with CAM, MEM had a shorter procedure duration (156.7 ± 59.1 ms vs. 127.3 ± 59.3 ms, P = 0.003) and mapping duration (62.6 ± 35.7 ms vs. 30.5 ± 15.3 ms, P < 0.001) and more mapping points (1364.9 ± 828.7 points vs. 148.3 ± 79.6 points, P < 0.001). There were no significant differences between CAM and MEM in acute ablation success rate, complication, postoperative AADs, and ablation duration. The mean disease-free survival time in CAM versus MEM was 20.8 (95% CI: 17.6–24.1) months versus 26.6 (95% CI: 22.7–30.4) months. The median disease-free survival time in the CAM versus MEM was 20.0 (95% CI: 13.9–26.1) months versus 30.0 (95% CI: 26.7–36.3) months. The AT recurrence risk of MEM was 0.522 times that of CAM (HR 95% CI: 0.282–0.968; P = 0.039). ConclusionMEM is strongly recommended in ablation of complex MAT.

Basic Principles of Conventional Mapping

Fluoroscopy-based cardiac mapping techniques can be used for mapping atrial tachycardia after atrial fibrillation ablation. The local atrial activation time can be determined with intracardiac bipolar electrograms alone, providing a sharp local activation time in combination with unipolar electrograms, the morphology of which provides important information regarding wave genesis and propagation. Using conventional activation mapping and entrainment mapping techniques, most atrial tachycardia can be mapped accurately.

Mapping rabbit whisker barrels using discriminant analysis of high field fMRI data

High field (>4T) functional magnetic resonance imaging (fMRI) techniques provide increased spatial resolution that enables the noninvasive, repeatable study of the sensory cortices at the level of their basic functional units. The examination of these units is important for studies of sensory information processing, learning- or experience-related brain plasticity, or the fundamental relationship between hemodynamic and neuronal activity. However functional units cannot always be distinguished from their surrounding areas by conventional activation mapping methods such as correlation or hypothesis tests, which only consider temporal variation within each individual voxel. We report a novel method to detect individual whisker barrels by using discriminant analysis to jointly characterize high order dependency among multiple voxels. Our results in the whisker barrel cortex of the awake rabbit indicate that the proposed method can differentiate reliably small clusters of activated voxels corresponding to individual whisker barrels within larger areas of functional activation, even in the case of adjacent whiskers in unanesthetized subjects. This method is computationally efficient, requires no specific experimental design for fMRI acquisition, and should be applicable to studies of other sensory systems.

Percutaneous Cardiopulmonary Support for Catheter Ablation of Unstable Ventricular Arrhythmias in High-Risk Patients

In patients with severe cardiomyopathy, recurrent episodes of nontolerated ventricular tachycardia (VT) or electrical storm (ES) frequently cause acute heart failure and cardiac death; the suppression of the arrhythmia is therefore lifesaving, but feasibility of catheter ablation (CA) is precluded by the adverse hemodynamic conditions together with the characteristics of the arrhythmia that interdicts efficacious mapping. The use of the percutaneous cardiopulmonary support (CPS) for circulatory assistance may allow patient's stabilization and enhance efficacy and safety of CA in this emergency setting. 19 patients (19 males; mean age 61 +/- 6 years; chronic ischemic cardiomyopathy, eleven patients; primary dilated cardiomyopathy, six patients; arrhythmogenic right ventricular dysplasia/ cardiomyopathy, two patients) with recurrent nontolerated VT episodes undergoing CPS-assisted CA were retrospectively evaluated. Twelve patients had acute hemodynamic failure refractory to inotropic agents and ventilatory assistance, seven patients had undergone a failing nonconventional CA procedure. 14 patients presented with ES, and in twelve the procedure was undertaken under emergency conditions within 24 h from admission. Patients were ventilated under general anesthesia and assisted by a multidisciplinary team. The CPS system consisted in a Medtronic Bio-Medicus centrifugal pump and in a Maxima Plus oxygenator, a 15-F arterial cannula, and a 17-F venous cannula. Flows between 2 and 3 l/min were activated after induction of 56/62 forms of nontolerated VT, achieving hemodynamic stabilization in all patients. CA was mainly guided by conventional activation mapping and was effective in abolishing 45/56 supported VTs; in 10/19 patients all clinical VTs were suppressed by CA. Mean procedural time was 4 h and 20 min. Complete stabilization was achieved in 13 patients (68%) without VT recurrence during a 7-day in-hospital monitoring. A significant clinical improvement was observed in two patients (11%); one patient (5%) with persistent VT episodes acutely died after heart transplant. At a mean follow-up of 42 months (range 15-60 months), 5/18 patients (28%) were free from VT recurrence, 7/18 (39%) had a clear clinical improvement with reduced implantable cardioverter defibrillator interventions. 5/14 patients (36%) had ES recurrence; among them, three died because of acute heart failure. No serious CPS-related complications were observed. The CPS warrants acceptable hemodynamic stabilization and efficacious mapping in high-risk patients undergoing CA for unstable VT in the emergency setting. Safety and efficacy of this technique translate into significant clinical improvement in the majority of patients. Even if only relatively invasive, CPS should be reserved to patients with ES or intractable arrhythmia causing acute heart failure; moreover, the need for an experienced team of multidisciplinary operators implies that its use is restricted to selected high-competency institutions.

Detecting functional nodes in large‐scale cortical networks with functional magnetic resonance imaging: A principal component analysis of the human visual system

This study aimed to demonstrate how a regional variant of principal component analysis (PCA) can be used to delineate the known functional subdivisions of the human visual system. Unlike conventional eigenimage analysis, PCA was carried out as a second-level analysis subsequent to model-based General Linear Model (GLM)-type functional activation mapping. Functional homogeneity of the functional magnetic resonance imaging (fMRI) time series within and between clusters was examined on several levels of the visual network, starting from the level of individual clusters up to the network level comprising two or more distinct visual regions. On each level, the number of significant components was identified and compared with the number of clusters in the data set. Eigenimages were used to examine the regional distribution of the extracted components. It was shown that voxels within individual clusters and voxels located in bilateral homologue visual regions can be represented by a single component, constituting the characteristic functional specialization of the cluster(s). If, however, PCA was applied to time series of voxels located in functionally distinct visual regions, more than one component was observed with each component being dominated by voxels in one of the investigated regions. The model of functional connections derived by PCA was in accordance with the well-known functional anatomy and anatomical connectivity of the visual system. PCA in combination with conventional activation mapping might therefore be used to identify the number of functionally distinct nodes in an fMRI data set in order to generate a model of functional connectivity within a neuroanatomical network.

Ablation of electrograms with an isolated, delayed component as treatment of unmappable monomorphic ventricular tachycardias in patients with structural heart disease

ObjectivesWe sought to evaluate the feasibility of identifying and ablating the substrate of unmappable ventricular tachycardia (VT). BackgroundNoninducible and nonstable VT cannot be ablated by the conventional approach. MethodsWe studied 24 patients with documented monomorphic VT. Twenty-one patients had ischemic cardiomyopathy, two had nonischemic cardiomyopathy, and one had tetralogy of Fallot. Twelve patients had an implantable cardioverter-defibrillator. Conventional activation mapping was not possible in 18 patients: at least 1 of the clinical VTs or the clinical VT was not inducible in 12 patients, and VT was not tolerated in 6 patients. This group had experienced between 1 and 106 VT episodes in the month before the ablation procedure. Endocardial electroanatomic activation maps (Carto System) during sinus rhythm (SR) and right ventricular apex (RVA) pacing were obtained to define areas for which an electrogram displayed isolated, delayed components (E-IDC). These electrograms were characterized by double or multiple components separated by ≥50 ms. ResultsOne area of E-IDC was recorded in 20 patients, and 2 or more were recorded in 4 patients. In 23 patients, these areas were detected during RVA pacing; in only 14 during SR. An E-IDC area related to the clinical VT was identified in each patient. Ablation guided by E-IDC suppressed all but one clinical VT whose inducibility suppression was tested. During a follow-up period of 9 ± 4 months, three patients had recurrences of the ablated VT and two of a different VT. ConclusionsElectrograms with IDCs related to clinical VT can be identified in the majority of patients during RVA pacing. Radiofrequency ablation of E-IDC seems effective in controlling unmappable VT.

Linear ablation lesions for control of unmappable ventricular tachycardia in patients with ischemic and nonischemic cardiomyopathy.

Conventional activation mapping is difficult without inducible, stable ventricular tachycardia (VT). We evaluated 16 patients with drug refractory, unimorphic, unmappable VT. Nine patients had ischemic and 7 had nonischemic cardiomyopathy. All patients had implantable defibrillators and had experienced 6 to 55 VT episodes during the month before treatment. Patients underwent bipolar catheter mapping during baseline rhythm. The amount of endocardium with an abnormal electrogram amplitude was estimated using fluoroscopy in 3 patients and a magnetic mapping system (CARTO) in 13 patients. For the magnetic mapping, normal endocardium was defined by an amplitude >1.5 mV; this measurement was based on sinus rhythm maps in 6 patients who did not have structural heart disease. Radiofrequency point lesions extended linearly from the "dense scar," which had a voltage amplitude <0.5 mV, to anatomic boundaries or normal endocardium. To limit radiofrequency applications, 12-lead ECG during VT and pacemapping guided placement of linear lesions. No new antiarrhythmic drug therapy was added. The amount of endocardium demonstrating an abnormal electrogram amplitude ranged from 25 to 127 cm(2). A total of 8 to 87 radiofrequency lesions (mean, 55) produced a median of 4 linear lesions that had an average length of 3.9 cm (range, 1.4 to 9. 4 cm). Twelve patients (75%) have been free of VT during 3 to 36 months of follow-up (median, 8 months); 4 patients had VT episodes at 1, 3, 9, and 13 months, respectively. Only one of these patient had frequent VT. Radiofrequency linear endocardial lesions extending from the dense scar to the normal myocardium or anatomic boundary seem effective in controlling unmappable VT.