Atypical atrial flutter in a patient with atrial septal ...

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doi:10.1093/europace/eup265 Online publish-ahead-of-print 3 October 2009

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Atypical atrial flutter in a patient with atrial septal defect without previous surgery: the role of septal defect as a part of the arrhythmia substrate Evgeny Mikhaylov1*, Sergey Gureev1, Tamas Szili-Torok2, and Dmitry Lebedev1 1 Department of Electrophysiology and Cardiac Pacing, Almazov Federal Heart, Blood and Endocrinology Centre, 2 Akkuratova Street, 197341 Saint-Petersburg, Russian Federation and 2Electrophysiology Unit, Department of Cardiology, Thoraxcentre, Erasmus MC, 230 s’ Gravendijkwal, 3015 CE Rotterdam, The Netherlands

* Corresponding author. Tel/Fax: þ7 812 5111616, Email: [email protected] Received 13 May 2009; accepted after revision 21 August 2009

This case report describes an atypical right atrial septal flutter in a patient with a non-corrected atrial septal defect. The unique feature of this case report is that reentrant tachycardia with a cycle around the atrial septal defect was non-scar related. The slow conduction around this atrial septal defect was probably formed by right atrial dilatation and intra-cardiac haemodynamic alterations.

Reentrant circuits for atrial flutters are usually related to a slow-conducting zone around different anatomical structures. Atypical atrial flutters are generally related to previous surgical or catheter interventions and require a scarred slow-conducting area. However, atypical atrial flutter can also develop in patients without previous cardiac interventions. The aim of this case report is to describe an atypical atrial flutter with a reentry circuit around an atrial septal defect, in a patient with no history of cardiac interventions. Case presentation

A 70-year-old female patient presented with a history of continuous atrial tachycardia during the last 2 years. She had required no previous cardiac surgery or cardiac interventions. A baseline 12-lead electrocardiogram (ECG) suggested atypical atrial flutter with 2:1 atrioventricular conduction (Figure 1) and right bundle branch block. A trans-thoracic echo was performed and revealed mild pulmonary hypertension and a left-to-right atrial shunt. The following transoesophageal echo revealed an ostium secundum atrial septal defect of 20 12mm. The patient was admitted to the electrophysiology department for catheter ablation of the atrial flutter.

Figure 1 ECG with atypical atrial flutter with negative flutter waves in leads II, III, aVF, and V1 – V4, isoelectric flutter waves in leads I, aVL, V5, and V6, and positive waves in lead aVR.

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Figure 2 (A) The activation map of the right atrium (left posterior oblique projection) shows a clockwise circular activation around the atrial septal defect (grey area). Note narrow isochronal lines in the antero-superior septal wall indicating localized slower conduction. The red dots mark the ablation line at the anatomic isthmus between the superior vena cava and the septal defect. The green point shows the entrainment pacing site (Figure 3A). The pink points show thoracic veins’ ostia. His, points of His electrogram registration; IVC, inferior caval vein; SVC, superior caval vein. (B) The bi-atrial bipolar voltage map demonstrates right atrial activity of low amplitude in the septal and inferior areas of the right atrium. Dotted line denotes the atrial septal defect. LAA, left atrial appendage; LIPV, left inferior pulmonary vein; LSPV, left superior pulmonary vein; RIPV, right inferior pulmonary vein; RSPV, right superior pulmonary vein. (C) The colour-coded 3D entrainment map of the right atrium (left posterior oblique projection). Red area shows points with a good post-pacing interval. Scar area shows the atrial septal defect. Electrophysiological study

Two catheters were placed through the right subclavian and femoral veins—a 6 F decapolar catheter (Biosense Webster, Diamond Bar, CA, USA) into the coronary sinus (CS) and an 8 F catheter (NaviStar ThermoCool, Biosense Webster) was used for electroanatomical mapping and ablation. The baseline tachycardia cycle length (CL) was 295 ms. The activation time on the CS electrode was 80 ms with the earliest activation from the mid-CS pair (CS 5 –6). By extending entrainment mapping to include multiple points in the right atrium, different poles on the CS electrode showed return CL longer than the tachycardia CL and suggested a reentrant circuit in the atrial septum. Bi-atrial activation mapping was performed with CARTO XP navigation system (Biosense Webster). The mapping catheter was introduced into the left atrium through the septal defect. The earliest activity was registered at the upper septal wall, although entrainment mapping showed a post-pacing interval exceeding a CL of 25 ms. Then electro-anatomical map of the right atrium was constructed. The tachycardia circuit was identified in the inter-atrial septum, around the ostium secundum atrial septal defect (Figure 2A). Entrainment mapping showed a satisfactory return cycle at several different points around the septal defect. Bipolar voltage mapping showed atrial electrograms of very low amplitude around the septal area (Figure 2B). In patients with macroreentrant tachycardias, colour-coded three-dimensional (3D) entrainment mapping was reported to be feasible to determine the exact localization of the reentrant circuit.1 According to this technique, the 3D location points were paired with colour-coded entrainment information in order to directly visualize the reentrant circuit (Figure 2C). Catheter ablation

A linear lesion was applied using a Stockert generator (Biosense Webster) from the superior caval vein to the atrial septal defect using open irrigated 3.5 mm tip ablation catheter. Energy delivery parameters were set at the following values: 488C, 35 W at the beginning of the ablation (from superior caval vein) with increased energy to 50 W at the lower part of the ablation line. Irrigation via the Cool Flow pump (Biosense Webster) was set at 17 mL/min. The ablation caused significant CL prolongation, and termination of the tachycardia occurred when the line was completed. Sinus rhythm (72 bpm) was spontaneously restored after a 3.5 s pause. The patient was discharged without antiarrhythmic therapy. Four months later, a septal occluder device was implanted. At 7-month follow-up, the patient reported no recurrence of atrial flutter. Discussion

It has been previously shown that among adults undergoing trans-catheter atrial septal defect closure, atrial tachyarrhythmias are present in 15%.2 Among patients undergoing surgical atrial septal defect closure, atrial flutter is found in 5%.3 In the described case, a relatively slow conduction zone was shown by the isochronal map on the antero-superior septal wall, some distance ‘upstream’ from the narrow segment of the circuit delimited by the superior vena cava orifice and the superior rim of the septal defect. The clear anatomic delimitation of this narrow isthmus made it an ideal ablation target.


Figure 3 (A) Entrainment pacing from the right atrium at the site between the upper margin of the atrial septal margin and the superior caval vein ostium (showed at Figure 2 by the green point). The atrial electrogram registered from the ablation is of low amplitude. (B) Termination of the tachycardia during radiofrequency ablation between the superior caval vein ostium and the septal defect. The sinus rhythm was restored after a 3.5 s pause and an escaped junctional complex.

Interestingly, there were no previous surgical or catheter interventions predisposing to the development of scar-related reentry tachycardia. Our theory is that a left-to-right atrial blood shunt led to overloading and significant enlargement of the right atrium, thereby promoting atrial tissue impairment and slowing conduction4 at the septal area.

Acknowledgements We thank Richard Alloway for language revision of the article. Conflict of interest: none declared.


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