EP ROUNDS

Where Is the Initiation of Atrial Fibrillation?SHINSUKE MIYAZAKI, M.D., TAKASHI UCHIYAMA, M.D., and YOSHITO IESAKA, M.D.From the Tsuchiura Kyodo Hospital, Ibaraki, Japan

ablation, atrial fibrillation

Figure 1. A circular mapping catheter was placed in the RSPV. The earliest activity was recordedin the RSPV when AF initiated. RSPV = right superior pulmonary vein, HRA = high right atrium,CS = coronary sinus.

Case PresentationA 67-year-old woman with drug-resistant

paroxysmal atrial fibrillation (AF) without anystructural heart disease was referred to ourcenter for catheter ablation. The procedure wasperformed under conscious sedation, and thestarting rhythm was sinus rhythm. A 14-polemapping catheter (Irvine Biomedical Inc., Irvine,CA, USA) was inserted through the right jugularvein and positioned in the coronary sinus. A de-capolar circular mapping catheter (Lasso, BiosenseWebster, Diamond Bar, CA, USA) was advancedin the left atrium through a transseptal hole,

Conflict of interest: none declared.

Address for reprints: Shinsuke Miyazaki, Cardiology Division,Cardiovascular Center, Tsuchiura Kyodo Hospital 11-7,Manabeshin-machi, Tsuchiura, Ibaraki 300-0053, Japan. Fax:+81 29 826 2411; e-mail: mshinsuke@k3.dion.ne.jp

Received March 5, 2012; revised April 15, 2012; accepted April16, 2012.

doi: 10.1111/j.1540-8159.2012.03462.x

and was placed in the right superior pulmonaryvein (RSPV). A spontaneous initiation of AF wasobserved after the placement of the catheters(Fig. 1). Where is the initiation of AF?

CommentaryPVs have been recognized as the most

important trigger of AF; therefore, PV isolation isthe cornerstone of AF ablation.1 Nonpulmonaryvein foci are also an important initiator of AF.2In this case, the earliest activity was recorded onthe mapping catheter placed in the RSPV, whichsuggested AF originated from the RSPV (Fig. 1).Figure 2 shows the intracardiac recordingswhich were recorded a few seconds after theinitiation of AF. PV tachycardia spontaneouslyoccurred from RSPV during AF, then disorga-nized activity was observed in the left atrium.These findings suggested that AF occurred inthe right atria initially, then AF occurred inthe left atria from the RSPV, which subse-quently conducted to the right inferior PV(Fig. 2). P waves did not reflect right atrial activity,

C©2012, The Authors. Journal compilation C©2012 Wiley Periodicals, Inc.

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Figure 2. Two circular mapping catheters were placed in the ipsilateral right PVs. A few secondsafter the initiation of AF, PV tachycardia was recorded in the RSPV. Note that AF initiated fromthe RSPV in the left atrium during AF in the right atrium. RIPV = right inferior pulmonary vein.

but left atrial activity. This image also clarifiedwhat was the PV potential and that the earliestactivity in Figure 1 was the far-field signal. Figure3 shows the intracardiac mapping of the superiorvena cava (SVC) when AF initiated. BigeminalSVC activity was recorded in the sinus rhythm,

and earliest activity was recorded in the SVCwhen AF initiated, which suggested that boththe SVC and RSPV were an independent onsetof fibrillation. After the electrical isolation of theSVC and right PVs, any atrial tachyarrhythmiawas not observed. Although right atrial fibrillation

Figure 3. A circular mapping catheter was placed in the SVC. AF initiated from the SVC. Notethe close relationship between the SVC and RSPV. SVC = superior vena cava.

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which was driven by the SVC did not last forlong time, the precise mechanism why it wasindependent from other areas was not clear. Apossible explanation is the electrophysiologicalproperty of interatrial conduction. That is, therefractory period of interatrial conduction mightbe longer than the AF cycle length of the rightatria. RSPV firing seemed to occur coincidentlyfollowing RA fibrillation.

Myocardial extension to the SVC with associ-ated arrhythmogenic activity in the SVC has beendemonstrated.3–5 Previous evidence indicates thatfocal electric firing originating from the SVC caninitiate paroxysmal AF,3 and sometimes the SVCacts as a driver for AF.6 Anatomically, the SVCand the RSPV are close to each other. Bothstructures are separated by a portion of the atrialseptum; however, the posterior aspect of the SVC

is adjacent to the anterior aspect of the RSPV.Sleeves of right atrial myocardium can extend upinto the SVC for a varying distance, sometimes upto a few centimeters. Therefore far-field potentialof the SVC can often be recorded within theRSPV, and some have reported the existence ofthis phenomenon in up to 23% of patients.7 Also,the recording of far-field potential from the RSPVwithin the SVC has been described.8 In this case,the RSPV alone seemed to be the initiator ofAF because the activity of the high right atriumwas recorded later than that of the RSPV whenAF initiated. However, subsequent detail mappingrevealed that the SVC was also the initiator of AFand that both the SVC and RSPV were associatedwith AF. Careful mapping and identifying near-field signal are important to identify the precisetrigger, especially at adjacent structures.

References1. Haıssaguerre M, Jaıs P, Shah DC, Takahashi A, Hocini M, Quiniou G,

Garrigue S, Le Mouroux A, Le Metayer P, Clementy J. Spontaneousinitiation of atrial fibrillation by ectopic beats originating from thepulmonary veins. N Engl J Med 1998; 339:659–666.

2. Shah D, Haissaguerre M, Jais P, Hocini M. Nonpulmonary vein foci:Do they exist? Pacing Clin Electrophysiol 2003; 26:1631–1635.

3. Higuchi K, Yamauchi Y, Hirao K, Sasaki T, Hachiya H, SekiguchiY, Nitta J, Isobe M. Superior vena cava as initiator of atrialfibrillation: Factors related to its arrhythmogenicity. Heart Rhythm2010; 7:1186–1191.

4. Shah DC, Haıssaguerre M, Jaıs P, Clementy J. High-resolution map-ping of tachycardia originating from the superior vena cava: Evidenceof electrical heterogeneity, slow conduction, and possible circusmovement reentry. J Cardiovasc Electrophysiol 2002; 13:388–392.

5. Miyazaki S, Kobori A, Kuwahara T, Takahashi A. Adenosine triphos-phate exposes dormant superior vena cava conduction responsiblefor recurrent atrial fibrillation. J Cardiovasc Electrophysiol 2010;21:464–465.

6. Miyazaki S, Kuwahara T, Takahashi A. Confined driver of atrialfibrillation in the superior vena cava. J Cardiovasc Electrophysiol2012; 23:440.

7. Shah D, Burri H, Sunthorn H, Gentil-Baron P. Identifyingfar-field superior vena cava potentials within the rightsuperior pulmonary vein. Heart Rhythm 2006; 3:898–902.

8. Miyazaki S, Liu X, Nault I, Haıssaguerre M, Hocini M. Dissociatedpotential within superior vena cava: What is the origin? HeartRhythm 2011; 8:946.

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