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Residual Atrial Signal or Late Ventricular Signal after Accessory Pathway Ablation: How to Resolve the Problem? PRABHAT KUMAR, M.D.,* SUNITA J. FERNS, M.D.,† and ANIL K. GEHI, M.D.* From the *Department of Medicine, Division of Cardiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina; and †Department of Pediatrics, Division of Cardiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina

ablation, electrophysiology – clinical, SVT Case Presentation A 15-year-old boy presented to the electrophysiology laboratory with a history of paroxysmal narrow complex tachycardia. A sinus rhythm 12-lead surface electrocardiogram demonstrated ventricular pre-excitation with morphology suggestive of a left lateral accessory pathway. A short RP tachycardia at a cycle length of 220 beats/min was induced. The tachycardia had features of orthodromic atrioventricular (AV) reentrant tachycardia with earliest atrial signal in distal coronary sinus (CS) electrodes. Ventricular pacing showed earliest retrograde atrial signal in distal CS (Fig. 1A). Endocardial ablation lesion at the site of earliest atrial activation with fused ventricular and atrial signal during right ventricular pacing was placed with a 5-mm nonirrigated-tip radiofrequency ablation catheter. This eliminated anterograde accessory pathway conduction and altered the retrograde activation sequence of the atrium with ventricular pacing (Fig. 1B). However, there was evidence of persistent retrograde accessory pathway conduction with administration of adenosine. A single lesion placed in the CS guided by mapping inside the CS near bipoles CS 3,4 led to loss of retrograde atrial activation (Fig. 2). Sharp late signals at the end of the paced ventricular electrograms were still present in two of the distal electrode pairs of the CS (Fig. 2). What does the change in atrial activation sequence in the CS suggest? Are there more than one accessory pathways present? Are these late potentials at the end of the ventricular signals in the lateral CS electrode pairs a part of Disclosures: None Address for reprints: Anil K. Gehi, M.D., F.H.R.S., University of North Carolina at Chapel Hill, Heart and Vascular, 160 Dental Circle, CB 7075, Chapel Hill, NC 27599. Fax: 919-966-4366; e-mail: [email protected] Received September 27, 2014; revised October 30, 2014; accepted November 10, 2014. doi: 10.1111/pace.12555

the ventricular electrogram or are they atrial or accessory pathway potentials? Commentary Change in CS activation during left atrial ablation despite the continued evidence of accessory pathway conduction (Fig. 1B) suggests that there was an additional accessory pathway or an additional atrial insertion of the accessory pathway with an atrial breakout with a slower retrograde conduction compared to the lateral accessory pathway. It is interesting to note that the sharp late signals after the ventricular electrograms in the lateral electrodes of the CS catheter did not change with ablation of the atrial insertion site of the lateral accessory pathway, with a notable additional far-field atrial potential (Fig. 1B) recorded on these electrodes (bipoles CS 1,2 and 3,4). These sharp signals associated with ventricular electrograms in the lateral CS electrodes (CS 3,4 and 5,6) persisted even after further ablation in the CS, leading to dissociation of slower sinus activity from ventricular paced complexes due to lack of retrograde AV nodal conduction, and continued presence of atrial electrograms with sinus activity in addition to and dissociated from the sharp signals (Fig. 2), reaffirming isolation of the atrial tissue at the accessory pathway insertion site or alternatively isolation of accessory pathway potential from the atrial activity. On detailed review of recorded electrograms before catheter ablation, confirmatory evidence of the sharp electrograms after the ventricular electrograms in CS 3,4 and 5,6 electrodes not being part of ventricular signals was found. Atrial ectopics coming from the ablation catheter tip close to the atrial insertion site of the left atrium just before the ventricular activation dissociated these signals from the ventricular signals (Fig. 3). Successful catheter ablation of WolffParkinson-White syndrome is often challenging to achieve. Pathways with a broad insertion, oblique course, or deep location in an area of

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Figure 1. (A) Ventricular pacing showing eccentric retrograde conduction to the atrium with earliest atrial electrogram seen in coronary sinus (CS) electrode 3,4. (B) Retrograde activation pattern of the atrium after initial endocardial left atrial ablation showing change in activation sequence in the CS. The proximal CS activation pattern has changed; however, the distal CS electrodes still have early atrial activation signals showing no change. The distal CS electrodes (1,2 and 3,4) show a far-field atrial signal in addition to the sharp signal immediately following the ventricular signal.

Figure 2. Radiofrequency ablation within the coronary sinus (CS 3,4) during ventricular pacing leads to loss of retrograde atrial activation with dissociated sinus activity after the first two beats with retrograde atrial activation. Paced ventricular electrograms have no associated atrial activation in the last three beats. Despite ventriculo-atrial dissociation, the last three of the paced ventricular electrograms have persistent sharp electrograms following the ventricular electrograms in CS leads 3,4 and 5,6, and far-field atrial activity recorded in these two bipoles (CS 3,4 and 5,6) in time with the dissociated atrial activity.

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IS THE ACCESSORY PATHWAY ABLATED?

Figure 3. Atrial ectopics induced by ablation catheter just preceding the first three paced ventricular beats in this tracing. Note earliest atrial signal in the distal ablation catheter. The first two ventricular paced beats do not show any retrograde atrial activity, as atrium was already depolarized and refractory at that time. In these two beats the coronary sinus leads 3,4 and 5,6 do not show the terminal sharp deflection, seen at the end of the procedure, suggesting that those signals are not due to ventricular activity. Slightly earlier atrial ectopic in the third beat in this strip led to the presence of retrograde atrial activation with ventricular pacing as this small delay led to recovery of the atrial tissue.

thicker myocardium frequently make ablation procedures more difficult and prolonged.1,2 When endocardial ablation is unsuccessful, ablation through the CS or epicardial access may be required.3–6 Elimination of accessory pathway conduction by direct ablation of the pathway with radiofrequency ablation or cryo-ablation is well known to be effective in treating associated arrhythmias with high long-term success rate.

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However, energy delivery to ablate the pathway directly is not possible occasionally due to anatomic issues and limitations of the technology of ablation used. In this case, isolation of the atrial insertion site of the pathway was successful in achieving elimination of accessory pathway conduction. This mechanism of accessory pathway ablation may be more common, though under-recognized in the electrophysiology laboratories.

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References 1. Morady F, Strickberger A, Man KC, Daoud E, Niebauer M, Goyal R, Harvey M, et al. Reasons for prolonged or failed attempts at radiofrequency catheter ablation of accessory pathways. J Am Coll Cardiol 1996; 27:683–689. 2. Nakagawa H, Jackman WM. Catheter ablation of paroxysmal supraventricular tachycardia. Circulation 2007; 116:2465–2478. 3. Lam C, Schweikert R, Kanagaratnam L, Natale A. Radiofrequency ablation of a right atrial appendage-ventricular accessory pathway by transcutaneous epicardial instrumentation. J Cardiovasc Electrophysiol 2000; 11:1170–1173. 4. Langberg JJ, Man KC, Vorperian VR, Williamson B, Kalbfleisch

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SJ, Strickberger SA, Hummel JD, et al. Recognition and catheter ablation of subepicardial accessory pathways. J Am Coll Cardiol 1993; 22:1100–1104. 5. Valderrabano M, Cesario DA, Ji S, Shannon K, Wiener I, Swerdlow CD, Oral H, et al. Percutaneous epicardial mapping during ablation of difficult accessory pathways as an alternative to cardiac surgery. Heart Rhythm 2004; 1:311–316. 6. Schweikert RA, Saliba WI, Tomassoni G, Marrouche NF, Cole CR, Dresing TJ, Tchou PJ, et al. Percutaneous pericardial instrumentation for endo-epicardial mapping of previously failed ablations. Circulation 2003; 108:1329–1335.

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Residual atrial signal or late ventricular signal after accessory pathway ablation: how to resolve the problem?

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