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      Atrioventricular nodal reentrant tachycardia and persistent left superior vena cava: A tough nut to crack. Successful ablation with transseptal approach

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          Abstract

          Key Teaching Points • Patients with persistent left superior vena cava have a significantly enlarged coronary sinus ostium, and the location of the slow pathway and His bundle area may be displaced, making the atrioventricular nodal reentrant tachycardia (AVNRT) ablation more challenging and increasing the risks of damage to the atrioventricular node. • The transseptal approach should be remembered and may be a simple, low-cost, and effective choice for the ablation in this situation. • When a left-side AVNRT ablation is performed, it may be necessary to position the ablation catheter in the ventricular aspect of the mitral annulus to achieve successful slow pathway elimination. Introduction Atrioventricular nodal reentrant tachycardia (AVNRT) ablation presents a high success rate with the classical approach, with the ablation catheter positioned in the right posterior septal region. Persistent left superior vena cava (PLSVC), although rare, is the most common venous anomaly in the chest, with a prevalence of 0.3%–0.5% in the general population. Patients with PLSVC have a significantly enlarged coronary sinus (CS) ostium, and the location of the slow pathway and His bundle area may be displaced, making the procedure more difficult and increasing the risk of damage to the atrioventricular (AV) node during ablation. Here we describe a patient with successful ablation of a typical AVNRT associated with PLSVC using the transseptal approach. Interestingly, the successful ablation site was on the ventricular aspect of the mitral annulus. Case report A 47-year-old woman without prior cardiovascular disease, with several episodes of paroxysmal supraventricular tachycardia refractory to drug treatment, was admitted for radiofrequency (RF) ablation. The electrophysiological study was performed after 8 hours of fasting and under general anesthesia. Antiarrhythmic medication was suspended for at least 5 half-lives before the procedure. Triple puncture of the femoral vein was performed with 2 7F decapolar catheters positioned inside the CS and right chambers. Atrial pacing with extrastimuli showed dual AV node physiology and inducted the clinical tachycardia easily, with the earliest atrial activation seen at the His catheter with a His–atrial time of 30 ms (Figure 1A). During tachycardia, an atrial extrastimulus was delivered when the junction was refractory, with advancement of the next His potential in 15 ms by early engagement of the slow pathway (Supplemental Figure 1), confirming a common type (slow–fast) of AVNRT. Figure 1 A: Atrial pacing with extrastimuli showed dual atrioventricular (AV) node physiology and inducted the clinical tachycardia easily, with the earliest atrial activation seen at the His catheter with a His–atrial time of 30 ms. B: Ablation catheter positioned at the anatomic slow pathway area in the right atrium (unsuccessful target). C: Ablation catheter positioned after transseptal access with a far-field atrial signal followed by a large ventricular electrogram, suggesting the ventricular side of the mittral annulus (successful target). D: Atrial pacing with extrastimuli confirmed the slow pathway ablation. I, II, II, avF, V1, and V6 indicate electrocardiography leads. A = atrial electrogram; Abl = Ablation catheter; d = distal; H = His electrogram; His = His area; p = proximal; SC = coronary sinus; V = ventricular electrogram. RF energy applications with a 4-mm catheter at the anatomic slow pathway area in the right atrium with a typical intracardiac electrogram (Figure 1B) and in the roof of the CS were unsuccessful despite the occurrence of a slow junctional rhythm. Owing to the long duration of the procedure and difficulty in stabilizing the catheter near the CS ostium, we performed CS venography, and the presence of a PLSVC was observed (Figure 2A and B). Figure 2 A, B: Coronary sinus (CS) venography in left anterior oblique (LAO; panel A) and right anterior oblique (RAO; panel B) fluoroscopy views showing persistent left superior vena cava (PLSVC). C, D: Position of the ablation catheter in the ventricular side of the mitral annulus at the posterior septal region through transseptal access (LAO: panel C; RAO: panel D). We chose to perform transseptal puncture under fluoroscopy, and the catheter was positioned on the left posterior septal region (Figure 2C and D) with the intention of targeting left-sided slow pathway inputs and an AV ratio of 1:8. Several RF energy applications were performed, but tachycardia was still inducible. In a region where there was only a small far-field atrial potential and a large ventricular electrogram, suggesting the ventricular aspect of the mitral annulus (Figure 1C), RF pulses resulted in an accelerated junctional rhythm. The tachycardia was no longer inducible, and tests confirmed the slow pathway elimination (Figure 1D). The procedure was well tolerated, with no complications. During 5 months of follow-up, the patient has remained clinically free of symptoms, without medications. Discussion AVNRT ablation presents a high success rate with the classical approach, with the ablation catheter positioned in the right posterior septal region. However, in less than 1% of cases, the left approach may be necessary in cases when the right-sided slow pathway ablation has failed. 1 PLSVC, although rare, is the most common venous anomaly in the chest, with a prevalence of 0.3%–0.5% in the general population and of 3% in patients with congenital heart defects. Usually, the left superior vena cava of the embryo involutes and becomes the ligament of Marshall in the mature heart. As an isolated anomaly PLSVC is most often detected during thoracic surgery or cardiac catheterization. 2 It typically drains into the right atrium through the CS, which becomes dilated owing to volume overload. Patients with PLSVC have a significantly enlarged CS ostium, and the location of the slow pathway and His bundle area may be displaced, making the procedure more difficult and increasing the risk of damage to the AV node during ablation.3, 4 Owing to these difficulties, several approaches besides fluoroscopy have been suggested and reported, such as the use of 3-dimensional electroanatomic mapping,5, 6 intracardiac echocardiography, 7 and even a magnet navigation system, 8 but to the best of our knowledge, this is the first case with the successful ablation of a typical AVNRT associated with PLSVC using the transseptal approach. This simple and low-cost strategy allowed for greater catheter stability and contact during the attempted mapping and ablation. Interestingly, as in the previous report by Green and colleagues, 9 the successful ablation site was on the ventricular aspect of the mitral annulus. This region is accessed through the AV part of the cardiac septum, where the left ventricular inlet shares a close relationship with the right atrium and slow pathway location owing to the inferior displacement of the tricuspid valve relative to the mitral valve, known as valvar offsetting (illustrated in Figure 3). While some morphologists describe this part of the cardiac septum as the muscular portion of the AV septum, some others argue that the region is not a true septum, since it carries a layer of epicardial fibroadipose tissue with the artery originating in the U-turn of the dominant coronary artery responsible for irrigation of the AV node. The proposed name for this particular region is, according to such authors, “muscular atrioventricular sandwich.” 10 We believe that this anatomic particularity must be considered for an adequate mapping of the slow pathway left inputs in all cases in which a left-side AVNRT ablation is necessary. Figure 3 A: Longitudinal section through the posteroinferior septal part of the atrioventricular junction in a normal heart. Note the valvar offsetting, with the septal leaflet of the tricuspid valve (T) inserting toward the apex relative to the mitral valve (Mi). The asterisk shows the area of the so-called “muscular atrioventricular sandwich.” B: Photomicrography of the septal structures at the atrioventricular junction. Note the atrioventricular septum separating the right atrium (RA) from the left ventricle (LV). The atrioventricular node is marked with arrows. The fibrous body is marked with the asterisk. Masson’s trichrome. Original image from the Anatomy Lab of Heart Institute – Incor, São Paulo, Brazil. MV = mitral valve; TV = tricuspid valve. Conclusion In cases where the classic AVNRT ablation approach fails, CS venography may diagnose PLSVC; and knowing the particularities of this association, the transseptal approach should be remembered and may be a simple, low-cost, and effective choice for the ablation of these arrhythmias. It may also be necessary to position the ablation catheter in the ventricular aspect of the mitral annulus to achieve successful slow pathway elimination.

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          Most cited references9

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          Cardiac anatomy revisited.

          In tomorrow's world of clinical medicine, students will increasingly be confronted by anatomic displays reconstructed from tomographically derived images. These images all display the structure of the various organs in anatomical orientation, this being determined in time-honoured fashion by describing the individual in the 'anatomical position', standing upright and facing the observer. It follows from this approach that all adjectives used to describe the organs should be related to the three orthogonal planes of the body. Unfortunately, at present this convention is not followed for the heart, even though most students are taught that the so-called 'right chambers' are, in reality, in front of their 'left' counterparts. Rigorous analysis of the tomographic images already available, along with comparison with dissected hearts displayed in attitudinally correct orientation, calls into question this continuing tendency to describe the heart in terms of its own orthogonal axes, but with the organ positioned on its apex, so that the chambers can artefactually be visualized with the right atrium and right ventricle in right-sided position. Although adequate for describing functional aspects, such as 'right-to-left' shunting across intracardiac communications, this convention falls short when used to describe the position of the artery that supplies the diaphragmatic surface of the heart. Currently known as the 'posterior descending artery', in reality it is positioned inferiorly, and its blockage produces inferior myocardial infarction. In this review, we extend the concept of describing cardiac structure in attitudinally correct orientation, showing also how access to tomographic images clarifies many aspects of cardiac structure previously considered mysterious and arcane. We use images prepared using new techniques such as magnetic resonance imaging and computerized tomography, and compare them with dissection of the heart made in time-honoured fashion, along with cartoons to illustrate contentious topics. We argue that there is much to gain by describing the components of the heart as seen in the anatomical position, along with all other organs and structures in the body. We recognize, nonetheless, that such changes will take many years to be put into practice, if at all.
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            "Left-variant" atypical atrioventricular nodal reentrant tachycardia: electrophysiological characteristics and effect of slow pathway ablation within coronary sinus.

            Recent anatomical and electrophysiological studies have demonstrated the presence of leftward posterior nodal extension (LPNE); however, its role in the genesis of atrioventricular nodal reentrant tachycardia (AVNRT) is poorly understood. This study was performed to characterize successful slow pathway (SP) ablation site and to elucidate the role of LPNE in genesis of atypical AVNRT with eccentric activation patterns within the coronary sinus (CS). Among 45 patients with atypical AVNRT (slow-slow/fast-slow/both = 20/22/3 patients) with concentric (n = 37, 82%) or eccentric CS activation (n = 8, 18%), successful ablation site was evaluated. Among 35/37 patients (95%) with concentric CS activation, ablation at the conventional SP region outside CS eliminated both retrograde SP conduction and AVNRT inducibility. Among eight patients with eccentric CS activation, the earliest retrograde atrial activation was found at proximal CS 16 +/- 4 mm distal to the ostium during AVNRT. The earliest retrograde activation site was located at inferior to inferoseptal mitral annulus, consistent with the presumed location of LPNE. Ablation at the conventional SP region with electroanatomical approach only rendered AVNRT nonsustained without elimination of retrograde SP conduction in seven of eight patients (88%). Ablation targeted to the earliest retrograde atrial activation site within proximal CS (15 +/- 4 mm distal to the ostium); however, eliminated retrograde SP conduction and rendered AVNRT noninducible in six of eight patients (75%). In 75% of "left-variant" atypical AVNRT, ablation within proximal CS was required to eliminate eccentric retrograde SP conduction and render AVNRT noninducible, suggesting LPNE formed retrograde limb of reentrant circuit.
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              Modulation of the slow pathway in the presence of a persistent left superior caval vein using the novel magnetic navigation system Niobe.

              This is the first report of a young female with typical AVNRT in the presence of a persistent left superior caval vein that underwent catheter ablation using the novel magnetic navigation system (MNS) Niobe (Stereotaxis Inc.). The MNS consists of two outer permanent magnets (about 0.1 T) that align a third small magnet integrated in the tip of a mapping and ablation catheter along its magnetic field lines. By changing the orientation of the outer magnets, the orientation of the magnetic field lines also change, thereby allowing navigation of the ablation catheter. In combination with an automated advancer system, this novel technique allows for the first time complete remote catheter ablation. Successful slow pathway modulation was performed using a total of seven radiofrequency current applications via the magnetic ablation catheter. No complication occurred. The novel magnetic navigation system proved to be a safe and feasible tool for remote catheter ablation of common type AVNRT in the presence of a persistent left superior caval vein.
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                Author and article information

                Contributors
                Journal
                HeartRhythm Case Rep
                HeartRhythm Case Rep
                HeartRhythm Case Reports
                Elsevier
                2214-0271
                19 September 2018
                December 2018
                19 September 2018
                : 4
                : 12
                : 589-593
                Affiliations
                []Heart Institute (Incor), University of São Paulo Medical School, São Paulo, Brazil
                []Hospital Brasil – Rede D’or, Santo André, Brazil
                Author notes
                [] Address reprint requests and correspondence: Dr Mauricio Ibrahim Scanavacca, Instituto do Coração (InCor) do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Av. Dr. Enéas de Carvalho Aguiar, 44, São Paulo, SP, Brazil, 05403-900. mauricio.scanavacca@ 123456gmail.com
                Article
                S2214-0271(18)30267-7
                10.1016/j.hrcr.2018.09.004
                6301891
                45569ac6-649a-47b9-b258-e535263413f3
                © 2018 Heart Rhythm Society. Published by Elsevier Inc.

                This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

                History
                Categories
                Case Report

                atrioventricular nodal reentrant tachycardia,left-side atrioventricular nodal reentrant tachycardia,muscular atrioventricular sandwich,persistent left superior vena cava,transseptal approach

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