We report a case of typical counterclockwise atrial flutter (AFL) with conduction block from
right to left atrium along the coronary sinus (CS) musculature, confirmed by discontinuous
CS activation sequence during pacing near the ostium and differential right atrial pacing.
AFL was associated with an atypical flutter wave morphology, due to the detour of the activation
wavefront from right to left atrium via alternate interatrial electrical connections, such as
Bachmann&#8217;s bundle, the interatrial septum, or both. (Cardiol J 2011; 18, 4: 450&#8211;453

Iijima, Takafumi

Irie, Tadanobu

Ito, Toshio

Kaneko, Yoshiaki

Kato, Toshimitsu

Kobayashi, Hiroaki

Kurabayashi, Masahiko

Manita, Mamoru

Nakajima, Tadashi

Ota, Masaki

Saito, Akihiro

Tamura, Mio

English

Via Medica Journals

INTERESTING ELECTROCARDIOGRAMSCardiology Journal2011, Vol. 18, No. 4, pp. 450–453Copyright © 2011 Via MedicaISSN 1897–5593450 www.cardiologyjournal.orgAddress for correspondence: Yoshiaki Kaneko, MD, PhD, Department of Medicine and Biological Science, Gunma UniversityGraduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma, 371-8511 Japan, fax: +81 27 220 8158,e-mail: kanekoy@gunma-u.ac.jpReceived: 21.11.2010 Accepted: 10.01.2011Typical atrial flutter with atypical flutter wavemorphology due to abnormal interatrial conductionTadanobu Irie, Yoshiaki Kaneko, Tadashi Nakajima, Akihiro Saito, Masaki Ota,Toshimitsu Kato, Takafumi Iijima, Mio Tamura, Hiroaki Kobayashi,Toshio Ito, Mamoru Manita, Masahiko KurabayashiDepartment of Medicine and Biological Science, Gunma UniversityGraduate School of Medicine, Maebashi, Gunma, JapanAbstractWe report a case of typical counterclockwise atrial flutter (AFL) with conduction block fromright to left atrium along the coronary sinus (CS) musculature, confirmed by discontinuousCS activation sequence during pacing near the ostium and differential right atrial pacing.AFL was associated with an atypical flutter wave morphology, due to the detour of the activa-tion wavefront from right to left atrium via alternate interatrial electrical connections, such asBachmann’s bundle, the interatrial septum, or both. (Cardiol J 2011; 18, 4: 450–453)Key words: atrial flutter, flutter wave, interatrial connection, diagnostic pacing,coronary sinus musculatureIntroductionTypical atrial flutter (AFL) is a macro-re-en-trant tachycardia rotating counterclockwise (CCW)in the right atrial (RA) wall and across the tricuspidannulus (TA)-inferior vena cava (IVC) isthmus.During ongoing AFL, the left atrium (LA) is acti-vated from the RA over one or more interatrial con-nections such as the coronary sinus (CS) muscula-ture, Bachmann’s bundle and the interatrial septum[1, 2]. The LA activation sequence is a major de-terminant of the characteristic saw tooth-like mor-phology of AFL, with predominantly negative po-larity of the flutter waves in the inferior and V6 leadsof the surface electrocardiogram (ECG), and posi-tive waves in lead V1 [3]. We describe a patient pre-senting with a typical CCW rotation of AFL and con-duction block through the CS ostial interatrial con-nection, producing an atypical morphology of theAFL waves.Case reportA 75 year-old woman was referred to our hos-pital for catheter ablation of paroxysmal AFL. The12-lead ECG during tachycardia showed negativeflutter waves in leads II, III, aVF and V5–V6, andpositive flutter waves in V1–V2, similar to thoseobserved in typical CCW AFL, although of unusu-ally low amplitude in all leads (Fig. 1A). After hav-ing given written informed consent, the patient un-derwent electrophysiological study. A 7 F deca-polar electrode (Irvine Biomedical, Irvine, CA, USA)with 5-mm inter-electrode spacing was placed inthe CS from the right subclavicular vein, and po-sitioned with its proximal poles (CS 9–10) at theostium and distal poles (CS 1–2) in a distal, leftlateral position confirmed by injection of contrastmaterial during fluoroscopy. A 7 F, 20-pole Halocatheter (Irvine Biomedical, Irvine, CA, USA) with2-20-2 mm inter-electrode spacing, was placed451Tadanobu Irie et al., Atrial flutter and interatrial conductionwww.cardiologyjournal.orgalong the TA, with the distal electrodes (H1–2)placed in the mid segment of the CS, and the H5––H6 electrodes at the ostium of the CS. A quadri-polar electrode catheter was placed in the His--bundle region. The atrial activation along the TAduring ongoing tachycardia at a cycle length of268 ms was CCW, and entrainment pacing from theIVC-TA isthmus, anterolateral or septal wall alongthe TA, showed a post-pacing interval equal to thetachycardia cycle length, confirming the diagnosisof typical CCW AFL. Recording of atrial activationalong the CS was proximal to distal, with a shortinterval between the proximal and distal atrialdeflections (Fig. 1B). Linear radiofrequency abla-tion blocked conduction across the IVC-TA isth-mus, terminated AFL, and restored sinus rhythm(Fig. 1B). Differential pacing from the low septaland low lateral RA confirmed the creation of bidi-rectional isthmus block.To test the hypothesis that the low AFL wavesamplitude and atypical atrial activation sequencealong the CS recordings during apparently typicalCCW AFL was due to LA propagation of the wave-front modified by abnormal conduction across inter-atrial connections, we paced alternatively from theCS ostium and from the right side of the interatrialseptum in search of interatrial conduction at theostium of the CS. During pacing from near the os-tium of the CS, the wavefront propagating from theisthmus to the lateral RA was blocked at the IVC--TA isthmus line of ablation, while the wavefrontpropagating from the isthmus to the CS was blockedat the proximal CS (Fig. 2A), suggesting that con-duction across the interatrial electrical connectionsat the ostium of the CS was blocked. Furthermore,the interval measured from the pacing spike to themid CS (H1–2), distal to the site of the presumedconduction block, was 75 ms (Fig. 2A), whereasduring pacing from the interatrial septum, the con-duction interval from pacing spike to the mid CS(H1–2) was 30 ms (Fig. 2B). Therefore, althoughthe anatomical distance between each pacing siteand the mid CS (H1–2) was nearly identical (Fig. 2C),the conduction time between the CS ostium and midCS (H1–2) was longer than between the interatrialseptum and mid CS (H1–2), strengthening the sug-gestion of an absence of interatrial connection at theostium of the CS.Figure 1. Surface and intracardiac electrocardiographic recordings during ongoing atrial flutter; A. Low-amplitudeflutter wave on 12-lead electrocardiogram; B. Linear ablation in the inferior vena cava (IVC)-tricuspid annulus (TA)isthmus terminated atrial flutter (AFL), which ended with the atrial electrogram in H11–12 (solid arrow and doubleline), indicating that the line of ablation was between H11–12 and H13–14; I, II, V1, V5 — surface electrocardiographicleads; HBE4–5 to HBE1–2 — proximal to distal His-bundle recordings; ABL1–2 and 3–4 — distal and proximalablation catheter recordings; H19–20 to H1–2 — proximal to distal Halo catheter recordings; CS9–10 to CS1–2 —proximal to distal coronary sinus recordings.A B452Cardiology Journal 2011, Vol. 18, No. 4www.cardiologyjournal.orgDiscussionIn this patient, who presented with typicalCCW AFL and atypical flutter wave morphology,conduction block across the interatrial connectionnear the ostium of the CS was confirmed by: 1) pac-ing near the ostium while recording activation be-tween the IVC-TA isthmus and the mid CS; and2) pacing alternatively from the CS ostium and fromthe right side of the interatrial septum, sites thatare nearly equidistant from the mid CS.These pacing maneuvers respectively showed:1) block of wavefront propagation at the CS ostiumtoward the distal CS; and 2) a distinctly longer con-duction time between ostium and mid CS than be-tween the interatrial septum and mid CS, despitethe nearly equal anatomical distance between eachpacing site and the mid CS.Previous anatomical studies have shown thatthe CS musculature is continuous with the RA atthe ostium and is connected to the LA myocardiumby multiple muscular strands [4]. In recent clinicalstudies of the earliest site of LA activation duringsinus rhythm, Bachmann’s bundle and the CS mus-culature were found to play a major role in the rightto left interatrial activation [5, 6]. However, thedelayed activation of the CS does not systematical-ly indicate conduction block over the CS muscula-ture, since during sinus rhythm the infero-medialRA, including the ostium of the CS and its muscularfibers, is often activated late. In fact, in some casesof delayed activation of the CS during sinus rhythm,pacing from the ostium of the CS only can unmaskthe transseptal propagation of the wavefront from RAto LA over the CS musculature [7]. Thus, activationmapping in the LA during sinus rhythm, as per-formed in previous studies [5, 6], cannot confirm theexistence of true conduction block over the CS mus-culature. To the best of our knowledge, there hasbeen no previous description of the electrophysio-logical characteristics diagnostic of conduction blockover the CS musculature in humans.During ongoing typical CCW AFL, the LA isan ‘innocent bystander’ activated predominantlyFigure 2. Intracardiac electrograms during pacing from near the ostium of the coronary sinus (CS) (A) and right-sidedinteratrial septum (B). Catheter position during pacing from near the ostium of the CS and right-sided interatrialseptum, in left anterior oblique fluoroscopic view (C); A. During pacing from near the ostium of the CS (H7–8), thewavefront propagating in an isthmus-to-lateral-left artrium direction (solid arrow) was interrupted at the isthmus lineof ablation, between H9–10 and H11–12, and the free wall of the right atrium, recorded from H11–12 to H19–20, wasactivated with a delay. The wavefront propagated in an isthmus-to-CS direction (dashed arrow) was interruptedbetween H3–4 and H1–2 in the proximal CS. Horizontal bars and numbers indicate the conduction times measuredfrom the pacing spike (S) to the atrial deflection in the mid CS (H1–2); B. Pacing from HBE1–2, on the right side of theinteratrial septum, near the bundle of His; C. Solid and dashed lines show the nearly identical distances between thepacing sites, H7–8 and HBE1–2, and the mid CS (H1–2); abbreviations are as in Figure 1.A B C453Tadanobu Irie et al., Atrial flutter and interatrial conductionwww.cardiologyjournal.orgfrom the CS ostium, and its activation sequencedetermines the flutter waves’ morphology [3]. Zren-ner et al. [8] reported a case of typical CCW AFLwhere the ablation of the CS ostial area during on-going AFL changed the flutter waves’ polarity with-out changing the RA activation sequence. Ashinoet al. [9] reported two patients with typical CCWAFL in whom spontaneous changes in the LA acti-vation sequence produced marked changes in theflutter wave polarity without changes in the RAactivation sequence. Yan et al. [10] observed anatypical flutter wave morphology in a significant sub-set of patients with typical CCW AFL, associatedwith atypical activation of the CS musculature. Thesereports suggested that alterations in the interatrialconnections play a role in the genesis of atypical mani-festations of typical CCW AFL, although they, incontrast to our own observations, did not show thepresence of conduction block over these connections.ConclusionsThe atypical morphology of the flutter wavesand fused CS activation observed in our case of ap-parently typical CCW AFL can be explained bya detour of the activation wavefront from RA to LAvia alternate interatrial connections, such as Bach-mann’s bundle, the interatrial septum, or both.AcknowledgementsThe authors do not report any conflict of inte-rest regarding this work.References1. Rodriguez LM, Timmermans C, Nabar A, Hofstra L, Wellens HJ.Biatrial activation in isthmus-dependent atrial flutter. Circula-tion, 2001; 104: 2545–2550.2. Marine JE, Korley VJ, Obioha-Ngwu O et al. Different patternsof interatrial conduction in clockwise and counterclockwiseatrial flutter. Circulation, 2001; 104: 1153–1157.3. Oshikawa N, Watanabe I, Masaki R et al. Relationship betweenpolarity of the flutter wave in the surface ECG and endocardialatrial activation sequence in patients with typical counterclock-wise and clockwise atrial flutter. J Interv Card Electrophysiol,2002; 7: 215–223.4. Chauvin M, Shah DC, Haïssaguerre M, Marcellin L, Brechen-macher C. The anatomic basis of connections between the coro-nary sinus musculature and the left atrium in humans. Circula-tion, 2000; 101: 647–652.5. Lemery R, Birnie D, Tang AS et al. Normal atrial activation andvoltage during sinus rhythm in the human heart: An endocardialand epicardial mapping study in patients with a history of atrialfibrillation. J Cardiovasc Electrophysiol, 2007; 18: 402–408.6. Tapanainen JM, Jurkko R, Holmqvist F et al. Interatrial right-to--left conduction in patients with paroxysmal atrial fibrillation.J Interv Card Electrophysiol, 2009; 25: 117–122.7. Lemery R, Soucie L, Martin B, Tang AS, Green M, Healey J.Human study of biatrial electrical coupling: Determinants of en-docardial septal activation and conduction over interatrial con-nections. Circulation, 2004: 110: 2083–2089.8. Zrenner B, Ndrepepa G, Karch M, Schneider M, Schmitt C.Block of the lower interatrial connections: insight into the sourc-es of electrocardiographic diversities in common typical atrialflutter. Pacing Clin Electrophysiol, 2000; 23: 917–920.9. Ashino S, Watanabe I, Okumura Y, Okubo K, Saito S. Change inatrial flutter morphology — insight into the sources of electro-cardiographic variants in common atrial flutter. Pacing Clin Elec-trophysiol, 2007; 30: 1023–1026.10. Yan SH, Cheng WJ, Wang LX, Chen MY, Hu HS, Xue M. Mecha-nisms of atypical flutter wave morphology in patients with isth-mus-dependent atrial flutter. 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Typical atrial flutter with atypical flutter wave morphology due to abnormal interatrial conduction

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Typical atrial flutter with atypical flutter wave morphology due to abnormal interatrial conduction

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