CASE REPORT Isolated Left Atrial Standstill Identified during Catheter Ablation EDWARD DUNCAN, PH.D., RICHARD J SCHILLING, M.D., and MARK EARLEY, M.D. From the Department of Cardiology, Barts and the London NHS Trust, London, UK This report describes the incidental finding of complete left atrial standstill during successful ablation of a right-sided atrial tachycardia in a patient with severe dilated cardiomyopathy and a history of extensive catheter ablation within the left atrium. (PACE 2010; 1–5) ablation, atrial fibrillation Case A 64-year-old woman with a biventricu- lar (BiV) implantable cardioverter defibrillator (ICD) presented to our hospital complaining of increased breathlessness and fatigue. Past medical history includes idiopathic dilated car- diomyopathy, complete heart block, ventricular tachycardia, and persistent atrial fibrillation (AF). Three years previously, she had undergone two ablation procedures for persistent AF comprising pulmonary vein (PV) isolation, linear ablation, and ablation of fractionated electrograms in the left atrium (LA). On both occasions, it was necessary to DC cardiovert from an atrial tachycardia to sinus rhythm. Following device optimization, she had been maintained on war- farin, bisoprolol, and amiodarone until her recent presentation. Device interrogation confirmed a regular atrial tachycardia (cycle length 278 ms, Fig. 1A). Twelve-lead electrocardiogram revealed low am- plitude atrial activity in lead V1 with little other discernable activity (Fig. 1B). The patient was referred for a further catheter ablation. Ablation was performed using the Hansen Sensei robotic catheter navigation system (Hansen Medical Inc., Mount View, CA, USA) and the CARTO3 mapping system (Biosense Webster, Diamond Bar, CA, USA). A decapolar catheter was introduced to the coronary sinus (CS) and left atrial access was gained via two uncomplicated trans-septal punctures. Figure 1C demonstrates intracardiac electrograms recorded with a 20-pole PV catheter Address for reprints: Edward Duncan, Ph.D., Department of Cardiology, Barts and the London NHS Trust, London, EC1A 7BE, UK. Fax: 442076017642; e-mail: edward.duncan@ bartsandthelondon.nhs.uk Received May 11, 2010; revised July 6, 2010; accepted August 15, 2010. doi: 10.1111/j.1540-8159.2010.02957.x in the left atrial appendage (LAA). In Figure 1D the PV catheter has been repositioned in the right atrial appendage (RAA). Possible explanations for the electrogram appearance in Figure 1C include absence of atrial signal within the LA and poor tissue contact with the PV catheter. In the latter, one would expect to see atrial electrograms recorded by the CS catheter. To clarify this issue, a detailed geometry known as a fast anatomical map (FAM, CARTO3) was made of the LA using a 20-pole PV catheter to acquire points. Correlation with a computerized tomography segmentation of the LA confirmed the accuracy of the geometry and ensured that good tissue contact had been made by the PV catheter. Angiography confirmed the location of the PV catheter within the PVs and appendage. Throughout this maneuver, no atrial activity was identified in the PVs, the LAA, or the body of the LA, confirming complete left atrial electrical standstill (Fig. 1C). Consistent with this, no atrial activity was identified on the CS catheter. Furthermore, extremely sluggish dispersal of contrast was noted during left atrial angiography and large volumes of spontaneous LA echo contrast were noted during the preprocedure transesophageal echocardiogram (despite long- term therapeutic anticoagulation). Relocation of the PV catheter within the RAA confirmed a stable atrial tachycardia with a cycle length of 278 ms (Fig. 1D). A geometry and activation map of the right atrium (RA) was created (Fig. 2) and voltage mapping confirmed large areas of low voltage (<0.05 mV) within this chamber also. Notably, the septum appeared particularly scarred, while the lateral wall of the RA demonstrated more well-preserved voltages. This indicated a possible myopathic process encroaching from the LA. Acti- vation mapping demonstrated a likely focal origin of the tachycardia in a low-voltage area bordering the residual healthy tissue and ablation at this site restored sinus rhythm (30 W, 45 ◦ , Fig. 2C). Fol- lowing termination, the intracardiac electrograms demonstrated atrioventricular dissociation and C 2010, The Authors. Journal compilation C 2010 Wiley Periodicals, Inc. PACE 2010 1