Two-to-one Conduction Block Between Left Atrium andRight Lower Pulmonary Vein Preceding Complete VeinIsolation During Radiofrequency Current AblationSTEFAN WEBER,* GJIN NDREPEPA,† MICHAEL SCHNEIDER,† and CLAUS SCHMITT†From the *Klinik und Poliklinik fur Innere Medizin II, Universitat Regensburg and †Deutsches HerzzentrumMunchen, Germany

WEBER S., ET AL.: Two-to-one Conduction Block Between Left Atrium and Right Lower Pulmonary VeinPreceding Complete Vein Isolation During Radiofrequency Current Ablation. A 56-year-old patient withparoxysmal atrial fibrillation who developed a transient 2:1 block between the left atrium and right inferiorpulmonary vein during a single application of radiofrequency current was described. The production oftransient and complete atriovenous block by a single application of radiofrequency current demonstratesthat a single connection between the pulmonary veins muscle and the left atrium may exist. (PACE 2004;27[Pt. I]:829–830)

atrial fibrillation, pulmonary vein, muscle connections

IntroductionPulmonary veins are considered to be the most

common origin of focal activity that triggers theonset of atrial fibrillation in humans.1,2 The tech-nique of isolation of the pulmonary veins from theleft atrium, developed by Haissaguerre et al.,1 iscurrently being used in many electrophysiologylaboratories to treat patients with atrial fibrillation.The anatomic structure of muscle connections be-tween the left atrium and pulmonary vein(s) ischaracterized by a high degree of variability interms of anatomic extent and localization and elec-trical behavior.3

Case PresentationA 56-year-old man with a 3-year history

of paroxysmal atrial fibrillation was referred toour electrophysiological laboratory for radiofre-quency ablation. The patient had several ECG-documented episodes of paroxysmal atrial fibril-lation triggered by atrial premature contractions.Pharmacological treatment with Class I, II, andIII antiarrhythmic drugs (including amiodarone)failed to prevent atrial fibrillation recurrences.Coronary artery disease, arterial hypertension, car-diomyopathies, valvular heart disease, and hyper-thyroidism were excluded; thus the patient wasconsidered to have lone atrial fibrillation. A three-catheter approach (one catheter was inserted in thecoronary sinus for mapping and pacing and two

Address for reprints: Stefan Weber M.D., Department of Cardi-ology, Internal Medicine II, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93042 Regensburg, Germany. Fax: +49-941-9447202; e-mail: stefan.weber@klinik.uni-regensburg.de

Received October 21, 2003; revised December 11, 2003; ac-cepted January 19, 2004.

catheters, one circumferential mapping and oneablation catheter, were inserted in the left atriumfor mapping and isolation of pulmonary veins)was used. During ablation procedure all four pul-monary veins were mapped consecutively by aLasso-Catheter (Biosense Webster, Inc., DiamondBar, CA, USA). Local pulmonary vein potentialscould be detected in all four pulmonary veins dur-ing sinus rhythm and/or coronary sinus pacing,reflecting the presence of pulmonary vein mus-cle connecting them with the left atrium. Electri-cal disconnection of the two left-sided pulmonaryveins and the right superior pulmonary vein wasachieved by application of five to nine radiofre-quency current deliveries at each vein. In order toachieve a complete vein isolation, radiofrequencycurrent had to be applied in three to five discretelocations within the ostial region of each vein,possibly reflecting extensive connections betweenpulmonary veins and the left atrial musculature inthese veins. After successful ablation of the threepulmonary veins, there was still ectopic activityemerging from the right inferior pulmonary veinthat triggered the onset of atrial fibrillation. TheLasso catheter was positioned within the right in-ferior pulmonary vein, a few millimeters distal tothe ostial region. Sharp local potentials were ob-served circumferentially at the ostial region of thevein (Fig. 1). Since the earliest potentials were ob-served at the electrode pair 1/2 (Fig. 1), the ablationcatheter was directed to that location and radiofre-quency current was delivered. After a few secondsof radiofrequency current delivery at this location,a 2:1 conduction block between left atrium andpulmonary vein muscle appeared. Continuation ofradiofrequency application for another 5 secondsresulted in complete disappearance of local poten-tials in all electrodes and thus in a complete leftatrium – right lower pulmonary vein block (Fig.1).

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Figure 1. Electrical disconnection of the right inferior pulmonary vein by radiofrequency application. From top tobottom, 3 surface ECG leads, 2 electrograms recorded from the mapping catheter inside the right inferior pulmonaryvein, and 10 bipolar electrograms recorded by the Lasso catheter located a few millimeters distal to the ostial region ofthe right inferior pulmonary vein are shown. Radiofrequency energy delivery at electrode pair (1/2) initially resulted ina 2:1 conduction block between the left atrium and the right inferior pulmonary vein. Continuation of energy deliveryin the same place for another 5 seconds resulted in a complete block between the right inferior vein and the left atrium.Immediately before appearance of complete left atrium-right inferior pulmonary vein block, a sequence of 3:1 blockwas observed.

No other radiofrequency current applications wereperformed. Following the complete atriovenousblock, no autonomous activity from inside thevein was observed. The complete block persistedafter provocative pacing and orciprenaline infu-sion applied 30 minutes following the last appli-cation of radiofrequency current. At the end ofthe procedure, angiography of all four pulmonaryveins was performed. No anatomic anomalies orsigns of acute stenosis for any of the veins wereobserved.

During a follow-up period of 6 months (Holtermonitoring performed at 1, 3, and 6 monthsafter ablation) no episodes of atrial fibrillationoccurred.

DiscussionThis case offers electrophysiological evidence

that electrical connections between the left atriumand the pulmonary veins show a high degree ofvariability even in the same subject. Despite thelarge local potentials throughout the circumferen-tial region, in contrast to the other three veins,the right lower pulmonary vein muscle seemedto have a single connection with the left atrialmusculature. Although the exact mechanisms thatenable this architecture and this type of conduc-tion remain uncertain, a single band of muscleoriginating from the left atrium and spiraling theright lower pulmonary vein could be a possibleexplanation.

References1. Haissaguerre M, Jais P, Shah DC, et al. Spontaneous initiation of

atrial fibrillation by ectopic beats originating in the pulmonary veins.N Engl Med 1998; 339:659–666.

2. Chen SA, Hsieh MH, Tai CT, et al. Initiation of atrial fibrillation byectopic beats originating from the pulmonary veins: Electrophysi-

ological characteristics, pharmacological responses, and effects ofradiofrequency ablation. Circulation 1999; 100:1879–1886.

3. Weiss C, Gocht A, Willems S, et al. Impact of the distribution andstructure of myocardium in the pulmonary veins for radiofrequencyablation of atrial fibrillation. PACE 2002; 25:1352–1356.

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