Europace Advance Access published October 7, 2015 Europace doi:10.1093/europace/euv256
CLINICAL RESEARCH
Focal atrial tachycardia originating from the septal mitral annulus: electrocardiographic and electrophysiological characteristics and radiofrequency ablation Yunlong Wang 1†, Ding Li 2†, Junmeng Zhang 1, Zhihong Han 1, Ye Wang1, Xuejun Ren 1*, Xuebin Li 2*, and Fang Chen 1 1 Department of Cardiology, Beijing Anzhen Hospital, Capital University of Medical Sciences, 2 Anzhen Rd, Beijing 100029, China; and 2Department of Cardiology, People’s Hospital, Peking University, 11 S Xizhimen St, Beijing 100044, China
Received 9 March 2015; accepted after revision 6 July 2015
Aims
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Atrial tachycardia † Surrounding the septal mitral annulus † Mapping † Ablation
Introduction Atrial tachycardia (AT) is a relatively uncommon cause of supraventricular tachycardia, for which radiofrequency ablation (RFA) is the treatment of choice.1,2 The characteristic anatomic distribution for focal AT is also well recognized. In the left atrium (LA), these foci tend to cluster around the pulmonary veins, near the
mitral annulus, within the left atrial appendage and the left septum.3,4 There are only isolated reports of AT originating from the mitral annulus–aorta junction [anterior paraseptal mitral annulus (APS-MA)].5,6 In this study, we assessed the electrocardiographic (ECG) features, electrophysiological features, and ablation outcomes in 13 patients with focal AT originating from the septal mitral annulus.
* Corresponding author. Tel/fax: +86 10 64456503. E-mail address: [email protected] (X.R.); Tel/fax: +86 10 88326500. E-mail address: [email protected] (X.L.) †
These authors contributed equally.
Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2015. For permissions please email: [email protected].
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This study sought to investigate electrocardiographic characteristics, electrophysiological features, and radiofrequency ablation in patients with focal atrial tachycardia (AT) originating from the septal mitral annulus. ..................................................................................................................................................................................... Methods In 13 patients with AT originating from the septal mitral annulus, activation mapping was performed to identify the and results earliest activation site. Successful ablation was performed through either a transseptal (n ¼ 12) or a retrograde aortic approach (n ¼ 1). As confirmed by electrogram recordings, fluoroscopy, and three-dimensional (3D) mapping, successful ablation sites were located in the anterior paraseptal, mid- to anteroseptal, and posterior septal mitral annulus in eight, three, and two patients, respectively. Foci for all locations demonstrated a negative/positive appearance in lead V1. Mapping in the right atrium demonstrated that the earliest right atrial activation was near the septum (His-bundle region or proximal coronary sinus). The electrograms at the successful ablation sites were fractionated in 9 patients, and presented with an atrial:ventricular ratio of ,1 in all 13 patients. There were no complications in any patients and long-term success was achieved in 12 of 13 patients during the 23 + 6 months following ablation. ..................................................................................................................................................................................... Conclusion The area surrounding the septal mitral annulus, most commonly the anterior paraseptal, is an unusual, but important site of origin for focal AT, which is associated with a distinctive P-wave morphology and atrial endocardial activation sequence. Radiofrequency ablation of AT originating from the septal mitral annulus, through either a transseptal or a retrograde aortic approach appears to be safe and effective.
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What’s new? † In this study, we performed extensive activation mapping of AT originating from the septal mitral annulus using a 3D electroanatomic mapping system. † Our study suggested that mapping and ablation of AT originating from the septal mitral annulus is feasible through either a transseptal or a retrograde aortic approach.
HB
Anterior paraseptal
Mid-to anteroseptal
Posteroseptal
MA
Methods Study population This study was approved by the Institutional Committee of Human Research at Anzhen Hospital. From a consecutive series of 314 patients undergoing RF between July 2005 and March 2012 at two institutes for focal origin of 328 ATs, this retrospective analysis included 13 consecutive patients with 13 clinically documented paroxysmal or persistent ATs. None of the patients had clinical documentation of atrial fibrillation. Four of the 13 patients had a previous failed ablation attempt.
TA LAO Projection
CS
Figure 1 Schematic diagram of the mitral annulus and tricuspid annulus showing the location of 13 ATs surrounding the septal mitral annular. Eight, three, and two tachycardias were located in the APS-MA, MAS-MA, and PS-MA, respectively. CS, coronary sinus; HB, His bundle; TA, tricuspid annulus; MA, mitral annulus; lilac area, the roof of the proximal CS.
Electrophysiological study Anatomic definition The area surrounding the septal mitral annulus was arbitrarily defined as an annular location between 6 and 12 o’clock when the mitral annulus was viewed in the left anterior oblique (LAO). It was classified as APSMA, mid- to anteroseptal mitral annulus (MAS-MA) and posterior septal mitral annulus (PS-MA) (Figure 1). An annular signal was defined as an atrial:ventricular (A:V) ratio of ,1. The location surrounding the septal mitral annulus where the tachycardia originated from was defined by four characteristics: (i) the RF catheter tip demonstrating the characteristic mitral annular location (between 6:00 and 12:00) and motion when viewed in the right and LAO fluoroscopic views; (ii) the RF catheter positioned in an MA location (between 6:00 and 12:00) when viewed in the right and LAO in 3D electroanatomic mapping; (iii) an A:V ratio of ,1 at the successful RF site; and (iv) a successful elimination of tachycardia by RF at the targeted site.
Ablation and outcome Mapping of atrial tachycardia Anatomic localization of the atrial focus was performed during tachycardia by analysis of surface ECG P-wave morphology, atrial endocardial activation sequence at a standard catheter setting, and three-dimensional (3D) activation mapping using the Biosense-Carto system. Tachycardia originating from the LA was suspected when the earliest right atrial activation occurred in the fossa ovalis, triangle of Koch, or CS ostium, but the earliest A wave was not significantly ahead of P-wave onset. Access to the LA for mapping and ablation was obtained through a transseptal or retrograde aortic approach. If the earliest right atrial activation occurred in the HB region and the P-wave morphology is similar to that of AT originating in the para-Hisian area, initial mapping was performed in the coronary cusp through a retrograde aortic approach before LA mapping. After the LA was accessed, an intravenous injection of heparin was started to maintain an activated clotting time of .250 s. Threedimensional mapping was performed using the Biosense-Carto system in 7 patients, while conventional fluoroscopy alone was used for the remaining patients.
A RF current was delivered to the tip of the NaviStar Thermocool catheter (irrigated at 17 mL/min) with 30 – 40 W of power and a temperature limit of 438C, or a 4-mm non-irrigated ablation was used with 30 – 40 W of power and a temperature limit of 558C at the site of earliest local activation. If the tachycardia was not affected within the first 15 s, energy delivery was discontinued; otherwise, 60 – 90 s of RF energy was delivered. Acute procedural success was defined as the absence of tachycardia or ectopy 30 min after ablation despite infusion of isoproterenol (up to 6 mg/min) and burst atrial pacing. Local electrograms were analysed at the successful site (A:V ratio, fractionated potentials).
P-wave analysis Surface 12-lead ECG P-wave morphology was assessed as previously described.2 P-wave analysis was applied during periods of atrioventricular (AV) blocking or post-ventricular pacing. P-waves were described by the deviation from the baseline during the T – P interval in four ways: (i) positive if there was a positive deviation from the isoelectric baseline; (ii) negative if there was a negative deviation; (iii) isoelectric, when there
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All patients underwent electrophysiological study after providing written informed consent. The procedure was performed with patients in the fasting state under light sedation. All antiarrhythmic drugs were discontinued at a minimum of five half-lives before the procedure. Three catheters including two 6 Fr quadripolar catheters and one 6 Fr octapolar catheter were deployed to the His-bundle (HB) position, right ventricular apex, and coronary sinus (CS), respectively. Bipolar intracardiac electrograms were filtered between 30 and 500 Hz, recorded, and stored digitally on a computerized system simultaneously with 12-lead surface ECGs (Bard Labsystem). An ablation catheter was initially introduced into the right femoral vein and advanced to the right atrium (RA) for atrial mapping and ablation. Standard electrophysiological criteria were used to diagnose AT.2 Attempts at AT induction were made through atrial programmed extra stimulation and burst atrial pacing; if unsuccessful or when AT was not occurring spontaneously, isoproterenol was infused (1 – 4 mg/min).
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Focal atrial tachycardia
was no P-wave deviation from the baseline of .0.05 mV; and (iv) biphasic if there were both positive and negative deviations from the baseline. All P-wave amplitudes were measured from peak to nadir.
Results Patient characteristics This study included 13 patients [age 35 + 12 (range 12– 59) years, 7 female] with AT originating from the area surrounding the septal mitral annulus. Successful ablation sites were located in the APS-MA, MAS-MA, and PS-MA in eight, three, and two patients, respectively (Figure 1). These 13 patients represented 4.1% of a consecutive series of 314 patients undergoing RF of a focal AT. All patients failed to respond to 1 –3 oral antiarrhythmic drugs. Mild dilated cardiomyopathy was present in two patients and one of them recovered after ablation of tachycardia.
Tachycardia characteristics
P-wave morphology In eight patients with APS-MA AT, the P-wave was characterized as (i) isoelectric in two and negative in six patients in leads aVL, (ii) positive in inferior leads with low amplitude, and (iii) followed a negative/positive pattern with a prominent positive component in lead V1 (Figure 2A). In the three patients with MAS-MA AT, the P-wave duration was shorter during tachycardia than during sinus rhythm (85 + 15 vs. 118 + 26 ms, P , 0.05) with low amplitude. The P-wave for these patients had three attributes: (i) biphasic with negative followed by positive deflection in the inferior and V1 leads; (ii) positive in leads I and aVL; and (iii) a negative component in leads V2–V6 (Figure 2B). In the two patients with PS-MA AT, the P-wave displayed four characteristics: (i) positive with low amplitude in lead aVL; (ii) negative or biphasic with negative followed by positive deflection in the inferior leads for two patients; (iii) a negative/positive pattern in lead V1 where the positive component was dominant; and (iv) a negative component during tachycardia in leads V2–V6 (Figure 2C).
Mapping and ablation All patients underwent successful ablation through a transseptal or retrograde aortic approach. Successful ablation was achieved in the sites of APS-MA in eight patients (Carto system was used in six of these patients), MAS-MA in another three patients, and PS-MA in the remaining two patients (Carto system was used in one patient). Among the eight patients with AT originating from APS-MA, the earliest RA activation was recorded near the superior septum that
Discussion Major findings The major findings in this study of 13 patients with AT originating from the septal mitral annulus who underwent successful RFA are
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The mean tachycardia cycle length was 376 + 65 ms. A spontaneous or adenosine-induced AV block was present, and dissociation was noted during tachycardia with ventricular overdrive pacing in all of the cases. Adenosine was successful in terminating AT in only 4 of the 13 patients. Three patients with AT originating from the APS-MA had incessant tachycardia. Three other patients had repetitive monomorphic AT originating from the MAS-MA. Tachycardia was inducible or terminated with programmed extrastimulation or burst atrial pacing in the remaining eight patients (six from APS-MA and two from PS-MA).
was superior and posterior to the HB and the activation time preceded P-wave onset by 16 + 5.2 ms. Proximal CS activation occurred earlier than distal activation in four patients and distal CS activation occurred before proximal activation in four patients (Figure 3). Through a transseptal approach, the earliest atrial activation was located in the APS-MA (mitral annulus–aorta junction) in eight patients (Figure 3) and the activation time preceded P-wave onset by 35.4 + 6.7 ms. In all the cases, successful ablation was achieved at this site. Among the three patients with AT originating from MAS-MA, the earliest RA activation was located near the HB and the atrial activation sequence of the CS was proximal to distal in all patients. The local A wave preceded the P-wave onset by 19, 18, and 18 ms, respectively. In all patients, subsequent mapping was attempted in aortic cusps through a retrograde aortic approach. The earliest activation in the aortic non-coronary cusp (NCC) and in the RA was the same. Ablation was attempted and failed in the NCC. Further mapping and ablation was performed in the RA, adjacent to the HB, but RF also failed and resulted in transient prolongation of the PR interval in one patient. In this patient, mapping of the LA septal and mitral annulus was performed by introducing the catheter into the LA over the aorta and left ventricle via a retrograde aortic approach. The earliest activation was recorded in the anteroseptal mitral annulus opposite to the HB area and the activation time preceded the P-wave by 32 ms (Figure 4). In the remaining two patients, further mapping of the LA through a transseptal approach registered the earliest atrial activation at the MAS-MA and the activation time preceded the P-wave onset by 35 ms and 36 m, respectively. In all three patients, successful RF was achieved in MAS-MA. Junctional rhythm occurred during ablation at the successful site in one patient. For the two patients with focal AT from PS-MA, right activation mapping recorded the earliest activation on the roof of the proximal CS and CS activation occurred proximally then distally in both patients (Figures 1 and 5). The local A wave preceded the P-wave onset by 19 and 18 ms in the two patients, respectively. Radiofrequency was delivered at the earliest activation site, without termination of tachycardia in either patient. Through a transseptal approach, LA mapping located the earliest activation in the PS-MA and the activation time preceded the P-wave onset by 32 and 30 ms, respectively. Tachycardia was terminated by RF application in both patients. The electrogram, at successful sites, was complex or fractionated in 9 of 13 patients and presented with an A:V ratio of ,1 in all 13 patients. At the site of successful ablation, acceleration and deceleration of tachycardia occurred before termination in five patients. After ablation, tachycardia was not inducible in all 13 patients by atrial stimulation with or without isoproterenol infusion. No complications occurred during or after catheter ablation. During a follow-up at a mean of 23 + 6 months without antiarrhythmic drugs, there was one recurrence, which occurred 3 days after ablation. This patient’s AT originated from APS-MA. Since they refused to repeat ablation they were left on oral medical therapy.
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A
B 47
I II III
C 48
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Figure 2 Representative P-wave morphological features on a 12-lead ECG in three separate patients with AT from the APS-MA (A), MAS-MA (B), and PS-MA (C ). Each boxed P-wave is enlarged to show the negative/positive P-wave in lead V1 (arrow). Time caliper: 1 s.
as follows: (i) AT can be successfully ablated through a transseptal or aortic retrograde approach; (ii) AT at all locations demonstrated a negative/positive appearance in lead V1; and (iii) the earliest atrial activation during RA activation mapping of tachycardia is recorded near the septum (HB region or proximal CS).
P-wave morphology Characteristic ECG morphological features of AT originating from the APS-MA are similar to those initially reported by Kistler et al. 5 The appearance in leads V1 and aVL is suggestive of a LA focus. In our series, P-wave morphologies in leads I, aVL and inferior leads are more useful to distinguish APS-MA from MAS-MA and PS-MA AT. An isoelectric or negative P-wave in leads I and aVL was more likely to be APS-MA AT, which can be reasonably explained by the more leftward position of the APS-MA compared with the MAS-MA and PS-MA AT (Figure 1). For MAS-MA and PS-MA AT, the P-wave morphology demonstrated a negative or negative/positive appearance in lead V1 and inferior leads similar to neighbouring sites at the CS ostium and para-AV node. Therefore, based on surface P-wave morphologic features alone, we speculate that it may be difficult to differentiate MAS-MA and PS-MA AT from CS ostium and para-AV node AT. The P-wave duration was shorter during tachycardia than during sinus
rhythm with MAS-MA AT. This could be related to a rapid biatrial spread from a focal septal origin of activation.
Activation mapping and radiofrequency ablation In this series of ATs originating from the area surrounding the septal mitral annulus, we showed that most were APS-MA ATs (8 of 13), while the remaining were MAS-MA (3 of 13) or PS-MA (2 of 13) ATs. All ATs were first mapped from the RA, with the earliest activation occurring adjacent to the HB (APS-MA and MAS-MA) or on the roof of the proximal CS (PS-MA). Two previous studies5,6 indicated that with AT arising from the APS-MA (mitral-aortic continuity), the earliest RA activation was recorded in the HB and CS activation occurred proximally then distally. However, in the present study, the earliest RA activation was recorded near the superior septum, and superior and posterior to the HB. The discrepancy may be attributed to the relatively small sample sizes and different mapping techniques. Kistler et al. 5 used a conventional mapping technique; however, 3D activation mapping (Biosense-Carto system) was used in 6 of 8 patients in the present study. We presume that in the present study, the earliest RA activation is due to the short distance of conduction to activate the RA via the interatrial septum rather than via the roof of the LA (Bachmann’s bundle). Roithinger et al. 7 has shown that during pacing from the LA,
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Figure 3 (A) Three-dimensional electroanatomic map of right and left atrial activation pattern during tachycardia. The earliest atrial activation was recorded near APS-MA. (B) Three-dimensional electroanatomic map of the right atrial activation pattern during tachycardia. The earliest atrial activation was recorded near the superior septum, and superior and posterior to the HB. (C) Intracardiac tracings at successful ablation site on the APS-MA during tachycardia. The earliest atrial activation preceded the P-wave onset in lead II by 38 ms. An A:V ratio of ,1 was observed in the local distal ablation electrogram. Radiofrequency application at this site successfully terminated the tachycardia. ABL, ablation catheter; CS, coronary sinus; HBE, His-bundle electrogram.
the putative insertion site of Bachmann’s bundle and interatrial septum is the preferential pathways for conduction to the RA. In our patients, conduction over the interatrial septum could explain the characteristic right atrial activation. In the present study, for APS-MA AT, CS activation occurred distally then proximally in 4 of 8 patients (Figure 3C), which is not consistent with the CS activation sequence (from proximal to distal) in all seven patients reported by Kistler et al. 5 This finding may reflect the fact that the electrical pulse from the APS-MA activates the LA roof and the lateral LA quickly, and the CS catheter was placed deeply in some patients. Based on the present study, if the P-wave morphological feature is suggestive of an APS-MA, we propose to place a CS
catheter deep inside the patient, and use a subsequent transseptal approach for ablation. In the three patients with AT originating from MAS-MA, RA activation mapping registered the earliest activation near the HB, and the local A wave preceded the P-wave onset by 10 – 15 ms. It has been reported that the NCC may be a target for some ATs that appear to arise in close proximity to the AV node.8 – 10 The P-wave morphology during tachycardia was very similar to the morphology of AT originating from the NCC, therefore, the initial mapping was performed in the coronary cusps. Although, the earliest atrial activation in the NCC and in the RA was the same, RF in the NCC and near the His-bundle electrogram in the RA both failed in all three
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Figure 4 (A and B) Left and right anterior oblique projections of the catheter positions are shown with the mapping catheter at the successful ablation site on the MAS-MA through an aortic retrograde approach. (C) Intracardiac tracings of the successful ablation target on the MAS-MA during tachycardia. The earliest atrial activation preceded the P-wave onset by 32 ms. An A:V ratio of ,1 was observed in the local ablation electrogram. Radiofrequency application at this site successfully terminated the tachycardia. ABL, ablation catheter; CS, coronary sinus; HBE, Hisbundle electrogram.
patients. This finding may be explained by the anatomical relationship. The NCC is anatomically closer to the HB region in the RA compared with the anteroseptal mitral annulus. Findings in the current study suggest that careful mapping in MAS-MA might be necessary to minimize the potential risk of injuring the AV node in focal AT with the earliest activation at the HB region before attempted RF at the HB region of the RA, especially with previous failed ablation in the NCC. The close anatomical localization between the NCC and MAS-MA explains the similarity of P-wave morphology between NCC AT and MAS-MA AT. Generally, AT with a left atrial origin is mapped and ablated via a transseptal approach. However, prior studies have suggested that through a retrograde approach left-sided accessory pathways can also be mapped and ablated at the atrial side of the mitral annulus.11,12 Our study has shown that ATs originating from MAS-MA can also be mapped and ablated via retrograde introduction of the catheter into the LA over the aorta and left ventricle. In one patient, junctional rhythm occurred
during RF at MAS-MA suggesting close proximity to left-sided extensions of the slow pathway or AV nodal tissue. In patients with PS-MA AT, careful mapping in the RA and CS indicated that the earliest activation occurred at the roof of the proximal CS. Prior studies have suggested that the CS is an important site of origin for focal AT, but the majority of foci is ostial, and only a very small percentage occur from deep within the CS. In the report by Nakagawa et al.,13 RA mapping indicated that the earliest activation occurred at the roof of the proximal CS in patients with a left PS accessory pathway. However, further mapping along the mitral annulus is commonly performed because ablation at the roof of the proximal CS (close to the atrial side of the PS-MA) usually fails to eliminate or only transiently eliminates accessory pathway conduction. These findings suggest that careful mapping in the posteriorseptal mitral annulus might be necessary in focal AT with the earliest activation at the roof of the proximal CS, especially with previous failed ablation in the CS.
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Figure 5 (A) Left anterior oblique projections of the catheter positions are shown with the mapping catheter at the roof of the proximal CS where the earliest right atrial activation site is located. (B) Left anterior oblique projections of the catheter positions are shown with the mapping catheter at the successful ablation site on the PS-MA through the transseptal approach. (C) Intracardiac tracings at the earliest right atrial activation site during tachycardia. The earliest atrial activation preceded P-wave onset in lead II by 19 ms. (D) Intracardiac tracings at the successful ablation target on the PS-MA during tachycardia. The earliest atrial activation preceded P-wave onset by 32 ms. An A:V ratio of ,1 was observed in the local distal ablation electrogram. Radiofrequency application at this site successfully terminated the tachycardia. ABL, ablation catheter; CS, coronary sinus; HBE, His-bundle electrogram.
Arrhythmogenic substrate and characteristic potential at target The mechanism of AT in the area surrounding the septal mitral annulus is unknown. McGuire et al.14 reported that atrial tissue surrounding the mitral annulus was specialized and different from other atrial myocytes. Wit and Cranefield15 reported that the myocardial cells at the mitral-aortic continuity exhibited AV node-like electrophysiological properties and gave rise to catecholamine-induced triggered
activities. Recently, Gonzalez et al.6 reported the existence of the remnants of a specialized conduction system at the APS-MA and they concluded that these remnant tissues might be a possible substrate of atrial arrhythmia. Furthermore, the septal mitral annulus has been shown to originate from inferior extensions of the AV node.16 In the present study, junctional rhythm occurred during ablation at the successful site in one patient with MAS-MA AT. These findings may play a potential role in arrhythmogenicity of this region.
Page 8 of 8 So far there are controversial opinions in regarding local potentials as a characteristic at the target sites area. Kay et al. 2 found fractionated or complex potentials at 8 of 13 target sites of focal AT. However, Liuba et al. 17 only found fractionated potentials at the target sites in 4 of 35 focal ATs (11%). In our study, fractionated or complex potential was found in 9 of 13 focal tachycardias (70%) at the target sites.
Limitations This study was limited by the relatively small number of patients included, particularly when patients were divided by AT origin location in the area surrounding the septal mitral annulus.
Conclusion The area surrounding the septal mitral annulus, particularly the APS, is an unusual but important site of origin for focal AT. The tachycardias are associated with a distinctive P-wave morphology and atrial endocardial activation sequence. Ablation of AT originating from the septal mitral annulus through a transseptal or retrograde approach is safe and effective. Knowledge of anatomic distribution and associated P-wave morphology allows targeted mapping and facilitates successful RFA.
This study was supported by the National Natural Science Foundation of China (Grant No. 81100126). We thank Dr Kelsey Moriarty and Dr Zhiqiang Liu at the University of Texas MD Anderson Cancer Center for their kind editorial help and advice. Conflict of interest: none declared.
References 1. Lesh MD, Van Hare GF, Epstein LM, Fitzpatrick AP, Scheinman MM, Lee RJ et al. Radiofrequency catheter ablation of atrial arrhythmias. Results and mechanisms. Circulation 1994;89:1074 –89.
2. Kay GN, Chong F, Epstein AE, Dailey SM, Plumb VJ. Radiofrequency ablation for treatment of primary atrial tachycardias. J Am Coll Cardiol 1993;21:901 – 9. 3. Kistler PM, Sanders P, Fynn SP, Stevenson IH, Hussin A, Vohra JK et al. Electrophysiological and electrocardiographic characteristics of focal atrial tachycardia originating from the pulmonary veins: acute and long-term outcomes of radiofrequency ablation. Circulation 2003;108:1968 –75. 4. Yang Q, Ma J, Zhang S, Hu JQ, Liao ZL. Focal atrial tachycardia originating from the distal portion of the left atrial appendage: characteristics and long-term outcomes of radiofrequency ablation. Europace 2012;14:254 – 60. 5. Kistler PM, Sanders P, Hussin A, Morton JB, Vohra JK, Sparks PB et al. Focal atrial tachycardia arising from the mitral annulus: electrocardiographic and electrophysiologic characterization. J Am Coll Cardiol 2003;41:2212 –9. 6. Gonzalez MD, Contreras LJ, Jongbloed MR, Rivera J, Donahue TP, Curtis AB et al. Left atrial tachycardia originating from the mitral annulus-aorta junction. Circulation 2004;110:3187 –92. 7. Roithinger FX, Cheng J, SippensGroenewegen A, Lee RJ, Saxon LA, Scheinman MM et al. Use of electroanatomic mapping to delineate transseptal atrial conduction in humans. Circulation 1999;100:1791 –7. 8. Ouyang F, Ma J, Ho SY, Bansch D, Schmidt B, Ernst S et al. Focal atrial tachycardia originating from the non-coronary aortic sinus: electrophysiological characteristics and catheter ablation. J Am Coll Cardiol 2006;48:122 –31. 9. Liu X, Dong J, Ho SY, Shah A, Long D, Yu R et al. Atrial tachycardia arising adjacent to noncoronary aortic sinus: distinctive atrial activation patterns and anatomic insights. J Am Coll Cardiol 2010;56:796 –804. 10. Beukema RJ, Smit JJ, Adiyaman A, Van Casteren L, Delnoy PP, Ramdat Misier AR et al. Ablation of focal atrial tachycardia from the non-coronary aortic cusp: case series and review of the literature. Europace 2015;17:953 –961. 11. Jackman WM, Wang XZ, Friday KJ, Roman CA, Moulton KP, Beckman KJ et al. Catheter ablation of accessory atrioventricular pathways (Wolff-Parkinson-White syndrome) by radiofrequency current. N Engl J Med 1991;324:1605 –11. 12. Calkins H, Sousa J, el-Atassi R, Rosenheck S, de Buitleir M, Kou WH et al. Diagnosis and cure of the Wolff-Parkinson-White syndrome or paroxysmal supraventricular tachycardias during a single electrophysiologic test. N Engl J Med 1991;324:1612 – 8. 13. Nakagawa H, Jackman WM. Catheter ablation of paroxysmal supraventricular tachycardia. Circulation 2007;116:2465 –78. 14. McGuire MA, de Bakker JM, Vermeulen JT, Moorman AF, Loh P, Thibault B et al. Atrioventricular junctional tissue. Discrepancy between histological and electrophysiological characteristics. Circulation 1996;94:571 –7. 15. Wit AL, Cranefield PF. Triggered activity in cardiac muscle fibers of the simian mitral valve. Circ Res 1976;38:85– 98. 16. Yanni J, Boyett MR, Anderson RH, Dobrzynski H. The extent of the specialized atrioventricular ring tissues. Heart Rhythm 2009;6:672 – 80. 17. Liuba I, Walfridsson H. Focal atrial tachycardia: increased electrogram fractionation in the vicinity of the earliest activation site. Europace 2008;10:1195 –204.
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Funding
Y. Wang et al.
CLINICAL RESEARCH
Focal atrial tachycardia originating from the septal mitral annulus: electrocardiographic and electrophysiological characteristics and radiofrequency ablation Yunlong Wang 1†, Ding Li 2†, Junmeng Zhang 1, Zhihong Han 1, Ye Wang1, Xuejun Ren 1*, Xuebin Li 2*, and Fang Chen 1 1 Department of Cardiology, Beijing Anzhen Hospital, Capital University of Medical Sciences, 2 Anzhen Rd, Beijing 100029, China; and 2Department of Cardiology, People’s Hospital, Peking University, 11 S Xizhimen St, Beijing 100044, China
Received 9 March 2015; accepted after revision 6 July 2015
Aims
----------------------------------------------------------------------------------------------------------------------------------------------------------Keywords
Atrial tachycardia † Surrounding the septal mitral annulus † Mapping † Ablation
Introduction Atrial tachycardia (AT) is a relatively uncommon cause of supraventricular tachycardia, for which radiofrequency ablation (RFA) is the treatment of choice.1,2 The characteristic anatomic distribution for focal AT is also well recognized. In the left atrium (LA), these foci tend to cluster around the pulmonary veins, near the
mitral annulus, within the left atrial appendage and the left septum.3,4 There are only isolated reports of AT originating from the mitral annulus–aorta junction [anterior paraseptal mitral annulus (APS-MA)].5,6 In this study, we assessed the electrocardiographic (ECG) features, electrophysiological features, and ablation outcomes in 13 patients with focal AT originating from the septal mitral annulus.
* Corresponding author. Tel/fax: +86 10 64456503. E-mail address: [email protected] (X.R.); Tel/fax: +86 10 88326500. E-mail address: [email protected] (X.L.) †
These authors contributed equally.
Published on behalf of the European Society of Cardiology. All rights reserved. & The Author 2015. For permissions please email: [email protected].
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This study sought to investigate electrocardiographic characteristics, electrophysiological features, and radiofrequency ablation in patients with focal atrial tachycardia (AT) originating from the septal mitral annulus. ..................................................................................................................................................................................... Methods In 13 patients with AT originating from the septal mitral annulus, activation mapping was performed to identify the and results earliest activation site. Successful ablation was performed through either a transseptal (n ¼ 12) or a retrograde aortic approach (n ¼ 1). As confirmed by electrogram recordings, fluoroscopy, and three-dimensional (3D) mapping, successful ablation sites were located in the anterior paraseptal, mid- to anteroseptal, and posterior septal mitral annulus in eight, three, and two patients, respectively. Foci for all locations demonstrated a negative/positive appearance in lead V1. Mapping in the right atrium demonstrated that the earliest right atrial activation was near the septum (His-bundle region or proximal coronary sinus). The electrograms at the successful ablation sites were fractionated in 9 patients, and presented with an atrial:ventricular ratio of ,1 in all 13 patients. There were no complications in any patients and long-term success was achieved in 12 of 13 patients during the 23 + 6 months following ablation. ..................................................................................................................................................................................... Conclusion The area surrounding the septal mitral annulus, most commonly the anterior paraseptal, is an unusual, but important site of origin for focal AT, which is associated with a distinctive P-wave morphology and atrial endocardial activation sequence. Radiofrequency ablation of AT originating from the septal mitral annulus, through either a transseptal or a retrograde aortic approach appears to be safe and effective.
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What’s new? † In this study, we performed extensive activation mapping of AT originating from the septal mitral annulus using a 3D electroanatomic mapping system. † Our study suggested that mapping and ablation of AT originating from the septal mitral annulus is feasible through either a transseptal or a retrograde aortic approach.
HB
Anterior paraseptal
Mid-to anteroseptal
Posteroseptal
MA
Methods Study population This study was approved by the Institutional Committee of Human Research at Anzhen Hospital. From a consecutive series of 314 patients undergoing RF between July 2005 and March 2012 at two institutes for focal origin of 328 ATs, this retrospective analysis included 13 consecutive patients with 13 clinically documented paroxysmal or persistent ATs. None of the patients had clinical documentation of atrial fibrillation. Four of the 13 patients had a previous failed ablation attempt.
TA LAO Projection
CS
Figure 1 Schematic diagram of the mitral annulus and tricuspid annulus showing the location of 13 ATs surrounding the septal mitral annular. Eight, three, and two tachycardias were located in the APS-MA, MAS-MA, and PS-MA, respectively. CS, coronary sinus; HB, His bundle; TA, tricuspid annulus; MA, mitral annulus; lilac area, the roof of the proximal CS.
Electrophysiological study Anatomic definition The area surrounding the septal mitral annulus was arbitrarily defined as an annular location between 6 and 12 o’clock when the mitral annulus was viewed in the left anterior oblique (LAO). It was classified as APSMA, mid- to anteroseptal mitral annulus (MAS-MA) and posterior septal mitral annulus (PS-MA) (Figure 1). An annular signal was defined as an atrial:ventricular (A:V) ratio of ,1. The location surrounding the septal mitral annulus where the tachycardia originated from was defined by four characteristics: (i) the RF catheter tip demonstrating the characteristic mitral annular location (between 6:00 and 12:00) and motion when viewed in the right and LAO fluoroscopic views; (ii) the RF catheter positioned in an MA location (between 6:00 and 12:00) when viewed in the right and LAO in 3D electroanatomic mapping; (iii) an A:V ratio of ,1 at the successful RF site; and (iv) a successful elimination of tachycardia by RF at the targeted site.
Ablation and outcome Mapping of atrial tachycardia Anatomic localization of the atrial focus was performed during tachycardia by analysis of surface ECG P-wave morphology, atrial endocardial activation sequence at a standard catheter setting, and three-dimensional (3D) activation mapping using the Biosense-Carto system. Tachycardia originating from the LA was suspected when the earliest right atrial activation occurred in the fossa ovalis, triangle of Koch, or CS ostium, but the earliest A wave was not significantly ahead of P-wave onset. Access to the LA for mapping and ablation was obtained through a transseptal or retrograde aortic approach. If the earliest right atrial activation occurred in the HB region and the P-wave morphology is similar to that of AT originating in the para-Hisian area, initial mapping was performed in the coronary cusp through a retrograde aortic approach before LA mapping. After the LA was accessed, an intravenous injection of heparin was started to maintain an activated clotting time of .250 s. Threedimensional mapping was performed using the Biosense-Carto system in 7 patients, while conventional fluoroscopy alone was used for the remaining patients.
A RF current was delivered to the tip of the NaviStar Thermocool catheter (irrigated at 17 mL/min) with 30 – 40 W of power and a temperature limit of 438C, or a 4-mm non-irrigated ablation was used with 30 – 40 W of power and a temperature limit of 558C at the site of earliest local activation. If the tachycardia was not affected within the first 15 s, energy delivery was discontinued; otherwise, 60 – 90 s of RF energy was delivered. Acute procedural success was defined as the absence of tachycardia or ectopy 30 min after ablation despite infusion of isoproterenol (up to 6 mg/min) and burst atrial pacing. Local electrograms were analysed at the successful site (A:V ratio, fractionated potentials).
P-wave analysis Surface 12-lead ECG P-wave morphology was assessed as previously described.2 P-wave analysis was applied during periods of atrioventricular (AV) blocking or post-ventricular pacing. P-waves were described by the deviation from the baseline during the T – P interval in four ways: (i) positive if there was a positive deviation from the isoelectric baseline; (ii) negative if there was a negative deviation; (iii) isoelectric, when there
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All patients underwent electrophysiological study after providing written informed consent. The procedure was performed with patients in the fasting state under light sedation. All antiarrhythmic drugs were discontinued at a minimum of five half-lives before the procedure. Three catheters including two 6 Fr quadripolar catheters and one 6 Fr octapolar catheter were deployed to the His-bundle (HB) position, right ventricular apex, and coronary sinus (CS), respectively. Bipolar intracardiac electrograms were filtered between 30 and 500 Hz, recorded, and stored digitally on a computerized system simultaneously with 12-lead surface ECGs (Bard Labsystem). An ablation catheter was initially introduced into the right femoral vein and advanced to the right atrium (RA) for atrial mapping and ablation. Standard electrophysiological criteria were used to diagnose AT.2 Attempts at AT induction were made through atrial programmed extra stimulation and burst atrial pacing; if unsuccessful or when AT was not occurring spontaneously, isoproterenol was infused (1 – 4 mg/min).
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Focal atrial tachycardia
was no P-wave deviation from the baseline of .0.05 mV; and (iv) biphasic if there were both positive and negative deviations from the baseline. All P-wave amplitudes were measured from peak to nadir.
Results Patient characteristics This study included 13 patients [age 35 + 12 (range 12– 59) years, 7 female] with AT originating from the area surrounding the septal mitral annulus. Successful ablation sites were located in the APS-MA, MAS-MA, and PS-MA in eight, three, and two patients, respectively (Figure 1). These 13 patients represented 4.1% of a consecutive series of 314 patients undergoing RF of a focal AT. All patients failed to respond to 1 –3 oral antiarrhythmic drugs. Mild dilated cardiomyopathy was present in two patients and one of them recovered after ablation of tachycardia.
Tachycardia characteristics
P-wave morphology In eight patients with APS-MA AT, the P-wave was characterized as (i) isoelectric in two and negative in six patients in leads aVL, (ii) positive in inferior leads with low amplitude, and (iii) followed a negative/positive pattern with a prominent positive component in lead V1 (Figure 2A). In the three patients with MAS-MA AT, the P-wave duration was shorter during tachycardia than during sinus rhythm (85 + 15 vs. 118 + 26 ms, P , 0.05) with low amplitude. The P-wave for these patients had three attributes: (i) biphasic with negative followed by positive deflection in the inferior and V1 leads; (ii) positive in leads I and aVL; and (iii) a negative component in leads V2–V6 (Figure 2B). In the two patients with PS-MA AT, the P-wave displayed four characteristics: (i) positive with low amplitude in lead aVL; (ii) negative or biphasic with negative followed by positive deflection in the inferior leads for two patients; (iii) a negative/positive pattern in lead V1 where the positive component was dominant; and (iv) a negative component during tachycardia in leads V2–V6 (Figure 2C).
Mapping and ablation All patients underwent successful ablation through a transseptal or retrograde aortic approach. Successful ablation was achieved in the sites of APS-MA in eight patients (Carto system was used in six of these patients), MAS-MA in another three patients, and PS-MA in the remaining two patients (Carto system was used in one patient). Among the eight patients with AT originating from APS-MA, the earliest RA activation was recorded near the superior septum that
Discussion Major findings The major findings in this study of 13 patients with AT originating from the septal mitral annulus who underwent successful RFA are
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The mean tachycardia cycle length was 376 + 65 ms. A spontaneous or adenosine-induced AV block was present, and dissociation was noted during tachycardia with ventricular overdrive pacing in all of the cases. Adenosine was successful in terminating AT in only 4 of the 13 patients. Three patients with AT originating from the APS-MA had incessant tachycardia. Three other patients had repetitive monomorphic AT originating from the MAS-MA. Tachycardia was inducible or terminated with programmed extrastimulation or burst atrial pacing in the remaining eight patients (six from APS-MA and two from PS-MA).
was superior and posterior to the HB and the activation time preceded P-wave onset by 16 + 5.2 ms. Proximal CS activation occurred earlier than distal activation in four patients and distal CS activation occurred before proximal activation in four patients (Figure 3). Through a transseptal approach, the earliest atrial activation was located in the APS-MA (mitral annulus–aorta junction) in eight patients (Figure 3) and the activation time preceded P-wave onset by 35.4 + 6.7 ms. In all the cases, successful ablation was achieved at this site. Among the three patients with AT originating from MAS-MA, the earliest RA activation was located near the HB and the atrial activation sequence of the CS was proximal to distal in all patients. The local A wave preceded the P-wave onset by 19, 18, and 18 ms, respectively. In all patients, subsequent mapping was attempted in aortic cusps through a retrograde aortic approach. The earliest activation in the aortic non-coronary cusp (NCC) and in the RA was the same. Ablation was attempted and failed in the NCC. Further mapping and ablation was performed in the RA, adjacent to the HB, but RF also failed and resulted in transient prolongation of the PR interval in one patient. In this patient, mapping of the LA septal and mitral annulus was performed by introducing the catheter into the LA over the aorta and left ventricle via a retrograde aortic approach. The earliest activation was recorded in the anteroseptal mitral annulus opposite to the HB area and the activation time preceded the P-wave by 32 ms (Figure 4). In the remaining two patients, further mapping of the LA through a transseptal approach registered the earliest atrial activation at the MAS-MA and the activation time preceded the P-wave onset by 35 ms and 36 m, respectively. In all three patients, successful RF was achieved in MAS-MA. Junctional rhythm occurred during ablation at the successful site in one patient. For the two patients with focal AT from PS-MA, right activation mapping recorded the earliest activation on the roof of the proximal CS and CS activation occurred proximally then distally in both patients (Figures 1 and 5). The local A wave preceded the P-wave onset by 19 and 18 ms in the two patients, respectively. Radiofrequency was delivered at the earliest activation site, without termination of tachycardia in either patient. Through a transseptal approach, LA mapping located the earliest activation in the PS-MA and the activation time preceded the P-wave onset by 32 and 30 ms, respectively. Tachycardia was terminated by RF application in both patients. The electrogram, at successful sites, was complex or fractionated in 9 of 13 patients and presented with an A:V ratio of ,1 in all 13 patients. At the site of successful ablation, acceleration and deceleration of tachycardia occurred before termination in five patients. After ablation, tachycardia was not inducible in all 13 patients by atrial stimulation with or without isoproterenol infusion. No complications occurred during or after catheter ablation. During a follow-up at a mean of 23 + 6 months without antiarrhythmic drugs, there was one recurrence, which occurred 3 days after ablation. This patient’s AT originated from APS-MA. Since they refused to repeat ablation they were left on oral medical therapy.
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A
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C 48
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Figure 2 Representative P-wave morphological features on a 12-lead ECG in three separate patients with AT from the APS-MA (A), MAS-MA (B), and PS-MA (C ). Each boxed P-wave is enlarged to show the negative/positive P-wave in lead V1 (arrow). Time caliper: 1 s.
as follows: (i) AT can be successfully ablated through a transseptal or aortic retrograde approach; (ii) AT at all locations demonstrated a negative/positive appearance in lead V1; and (iii) the earliest atrial activation during RA activation mapping of tachycardia is recorded near the septum (HB region or proximal CS).
P-wave morphology Characteristic ECG morphological features of AT originating from the APS-MA are similar to those initially reported by Kistler et al. 5 The appearance in leads V1 and aVL is suggestive of a LA focus. In our series, P-wave morphologies in leads I, aVL and inferior leads are more useful to distinguish APS-MA from MAS-MA and PS-MA AT. An isoelectric or negative P-wave in leads I and aVL was more likely to be APS-MA AT, which can be reasonably explained by the more leftward position of the APS-MA compared with the MAS-MA and PS-MA AT (Figure 1). For MAS-MA and PS-MA AT, the P-wave morphology demonstrated a negative or negative/positive appearance in lead V1 and inferior leads similar to neighbouring sites at the CS ostium and para-AV node. Therefore, based on surface P-wave morphologic features alone, we speculate that it may be difficult to differentiate MAS-MA and PS-MA AT from CS ostium and para-AV node AT. The P-wave duration was shorter during tachycardia than during sinus
rhythm with MAS-MA AT. This could be related to a rapid biatrial spread from a focal septal origin of activation.
Activation mapping and radiofrequency ablation In this series of ATs originating from the area surrounding the septal mitral annulus, we showed that most were APS-MA ATs (8 of 13), while the remaining were MAS-MA (3 of 13) or PS-MA (2 of 13) ATs. All ATs were first mapped from the RA, with the earliest activation occurring adjacent to the HB (APS-MA and MAS-MA) or on the roof of the proximal CS (PS-MA). Two previous studies5,6 indicated that with AT arising from the APS-MA (mitral-aortic continuity), the earliest RA activation was recorded in the HB and CS activation occurred proximally then distally. However, in the present study, the earliest RA activation was recorded near the superior septum, and superior and posterior to the HB. The discrepancy may be attributed to the relatively small sample sizes and different mapping techniques. Kistler et al. 5 used a conventional mapping technique; however, 3D activation mapping (Biosense-Carto system) was used in 6 of 8 patients in the present study. We presume that in the present study, the earliest RA activation is due to the short distance of conduction to activate the RA via the interatrial septum rather than via the roof of the LA (Bachmann’s bundle). Roithinger et al. 7 has shown that during pacing from the LA,
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Figure 3 (A) Three-dimensional electroanatomic map of right and left atrial activation pattern during tachycardia. The earliest atrial activation was recorded near APS-MA. (B) Three-dimensional electroanatomic map of the right atrial activation pattern during tachycardia. The earliest atrial activation was recorded near the superior septum, and superior and posterior to the HB. (C) Intracardiac tracings at successful ablation site on the APS-MA during tachycardia. The earliest atrial activation preceded the P-wave onset in lead II by 38 ms. An A:V ratio of ,1 was observed in the local distal ablation electrogram. Radiofrequency application at this site successfully terminated the tachycardia. ABL, ablation catheter; CS, coronary sinus; HBE, His-bundle electrogram.
the putative insertion site of Bachmann’s bundle and interatrial septum is the preferential pathways for conduction to the RA. In our patients, conduction over the interatrial septum could explain the characteristic right atrial activation. In the present study, for APS-MA AT, CS activation occurred distally then proximally in 4 of 8 patients (Figure 3C), which is not consistent with the CS activation sequence (from proximal to distal) in all seven patients reported by Kistler et al. 5 This finding may reflect the fact that the electrical pulse from the APS-MA activates the LA roof and the lateral LA quickly, and the CS catheter was placed deeply in some patients. Based on the present study, if the P-wave morphological feature is suggestive of an APS-MA, we propose to place a CS
catheter deep inside the patient, and use a subsequent transseptal approach for ablation. In the three patients with AT originating from MAS-MA, RA activation mapping registered the earliest activation near the HB, and the local A wave preceded the P-wave onset by 10 – 15 ms. It has been reported that the NCC may be a target for some ATs that appear to arise in close proximity to the AV node.8 – 10 The P-wave morphology during tachycardia was very similar to the morphology of AT originating from the NCC, therefore, the initial mapping was performed in the coronary cusps. Although, the earliest atrial activation in the NCC and in the RA was the same, RF in the NCC and near the His-bundle electrogram in the RA both failed in all three
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CS90 CS78 CS56 CS34 CS12 ABLd
Figure 4 (A and B) Left and right anterior oblique projections of the catheter positions are shown with the mapping catheter at the successful ablation site on the MAS-MA through an aortic retrograde approach. (C) Intracardiac tracings of the successful ablation target on the MAS-MA during tachycardia. The earliest atrial activation preceded the P-wave onset by 32 ms. An A:V ratio of ,1 was observed in the local ablation electrogram. Radiofrequency application at this site successfully terminated the tachycardia. ABL, ablation catheter; CS, coronary sinus; HBE, Hisbundle electrogram.
patients. This finding may be explained by the anatomical relationship. The NCC is anatomically closer to the HB region in the RA compared with the anteroseptal mitral annulus. Findings in the current study suggest that careful mapping in MAS-MA might be necessary to minimize the potential risk of injuring the AV node in focal AT with the earliest activation at the HB region before attempted RF at the HB region of the RA, especially with previous failed ablation in the NCC. The close anatomical localization between the NCC and MAS-MA explains the similarity of P-wave morphology between NCC AT and MAS-MA AT. Generally, AT with a left atrial origin is mapped and ablated via a transseptal approach. However, prior studies have suggested that through a retrograde approach left-sided accessory pathways can also be mapped and ablated at the atrial side of the mitral annulus.11,12 Our study has shown that ATs originating from MAS-MA can also be mapped and ablated via retrograde introduction of the catheter into the LA over the aorta and left ventricle. In one patient, junctional rhythm occurred
during RF at MAS-MA suggesting close proximity to left-sided extensions of the slow pathway or AV nodal tissue. In patients with PS-MA AT, careful mapping in the RA and CS indicated that the earliest activation occurred at the roof of the proximal CS. Prior studies have suggested that the CS is an important site of origin for focal AT, but the majority of foci is ostial, and only a very small percentage occur from deep within the CS. In the report by Nakagawa et al.,13 RA mapping indicated that the earliest activation occurred at the roof of the proximal CS in patients with a left PS accessory pathway. However, further mapping along the mitral annulus is commonly performed because ablation at the roof of the proximal CS (close to the atrial side of the PS-MA) usually fails to eliminate or only transiently eliminates accessory pathway conduction. These findings suggest that careful mapping in the posteriorseptal mitral annulus might be necessary in focal AT with the earliest activation at the roof of the proximal CS, especially with previous failed ablation in the CS.
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Figure 5 (A) Left anterior oblique projections of the catheter positions are shown with the mapping catheter at the roof of the proximal CS where the earliest right atrial activation site is located. (B) Left anterior oblique projections of the catheter positions are shown with the mapping catheter at the successful ablation site on the PS-MA through the transseptal approach. (C) Intracardiac tracings at the earliest right atrial activation site during tachycardia. The earliest atrial activation preceded P-wave onset in lead II by 19 ms. (D) Intracardiac tracings at the successful ablation target on the PS-MA during tachycardia. The earliest atrial activation preceded P-wave onset by 32 ms. An A:V ratio of ,1 was observed in the local distal ablation electrogram. Radiofrequency application at this site successfully terminated the tachycardia. ABL, ablation catheter; CS, coronary sinus; HBE, His-bundle electrogram.
Arrhythmogenic substrate and characteristic potential at target The mechanism of AT in the area surrounding the septal mitral annulus is unknown. McGuire et al.14 reported that atrial tissue surrounding the mitral annulus was specialized and different from other atrial myocytes. Wit and Cranefield15 reported that the myocardial cells at the mitral-aortic continuity exhibited AV node-like electrophysiological properties and gave rise to catecholamine-induced triggered
activities. Recently, Gonzalez et al.6 reported the existence of the remnants of a specialized conduction system at the APS-MA and they concluded that these remnant tissues might be a possible substrate of atrial arrhythmia. Furthermore, the septal mitral annulus has been shown to originate from inferior extensions of the AV node.16 In the present study, junctional rhythm occurred during ablation at the successful site in one patient with MAS-MA AT. These findings may play a potential role in arrhythmogenicity of this region.
Page 8 of 8 So far there are controversial opinions in regarding local potentials as a characteristic at the target sites area. Kay et al. 2 found fractionated or complex potentials at 8 of 13 target sites of focal AT. However, Liuba et al. 17 only found fractionated potentials at the target sites in 4 of 35 focal ATs (11%). In our study, fractionated or complex potential was found in 9 of 13 focal tachycardias (70%) at the target sites.
Limitations This study was limited by the relatively small number of patients included, particularly when patients were divided by AT origin location in the area surrounding the septal mitral annulus.
Conclusion The area surrounding the septal mitral annulus, particularly the APS, is an unusual but important site of origin for focal AT. The tachycardias are associated with a distinctive P-wave morphology and atrial endocardial activation sequence. Ablation of AT originating from the septal mitral annulus through a transseptal or retrograde approach is safe and effective. Knowledge of anatomic distribution and associated P-wave morphology allows targeted mapping and facilitates successful RFA.
This study was supported by the National Natural Science Foundation of China (Grant No. 81100126). We thank Dr Kelsey Moriarty and Dr Zhiqiang Liu at the University of Texas MD Anderson Cancer Center for their kind editorial help and advice. Conflict of interest: none declared.
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Funding
Y. Wang et al.
