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International Journal of Arrhythmia 2013;14(1): 33-37.
Untitled Document
ECG & EP CASES
Catheter Ablation of Atypical
Atrial Flutter after Cardiac Surgery
Using a 3-D Mapping System

 

               Myung-Jin Cha          Seil Oh

Myung-Jin Cha, MD, Seil Oh, MD, PhD, FHRS
Department of Internal Medicine, Seoul National University College of Medicine and Seoul National University Hospital, Seoul, Korea




   Introduction

   Electrophysiological study and fluoroscopyguided radiofrequency (RF) catheter ablation (RFCA) have become standard modalities for treatment of paroxysmal supraventricular tachycardia.1-2 However, there are serious limitations in fluoroscopy-guided ablation procedures, including poor resolution of soft tissue, poor visualization of the site of origin, difficulty in mapping complex arrhythmias, and exposure of patients and physicians to relatively high levels of radiation.3-4 During the last decade, clinical applications of the 3-dimensional (3D) mapping system have enabled real-time display of the ablation catheter in cardiac anatomy and led to an increased rate of procedure success in difficult cases.5-6
   In this report, we present the successful catheter ablation of atypical atrial flutter after open heart surgery, using a 3D mapping system.

Case

   In February of 2013, a 65-year-old man was admitted to the Arrhythmia Center of Seoul National University Hospital for the management of incessant atrial flutter. His current medical problems included hypertension and dyslipidemia. His medical history was significant for aortic valve-replacement surgery using a mechanical valve in 2006. He was regularly followed at the Cardiac Surgery Center and was taking warfarin, hydrochlorothiazide, and a statin. He had started to feel intermittent palpitations with chest pain after surgery, and was diagnosed with atrial flutter at a regional hospital. RFCA was performed at that hospital in 2011, but the patient’s symptoms were not improved because of failed ablation. His palpitations were sustained despite the use of antiarrhythmic agents such as beta-blockers or amiodarone. In addition, he experienced sudden syncope and was diagnosed with tachycardiabradycardia syndrome by Holter monitoring in June 2012. Although his syncope resolved after implantation of a permanent pacemaker, he continued experiencing intermittent palpitations despite an intensive regimen of antiarrhythmic medications. Consequently, he visited our Arrhythmia Clinic in January 2013.
   At his visit, 12-lead ECG showed a regular narrow-QRS tachycardia with 2:1 AV conduction (Figure. 1). The heart rate was 139 bpm; blood pressure, 109/78 mmHg. Echocardiography confirmed a well-functioning mechanical aortic valve with a normal transaortic pressure gradient and normal cavity size. However, it also showed global hypokinetics of the left ventricle, with decreased systolic function and an ejection fraction (EF) of 43%. Coronary CT angiography showed no significant stenosis in the coronary arteries.



   After the patient provided written informed consent, he was transferred to the electrophysiology laboratory while he was experiencing tachycardia. Tachycardia cycle length was 226 ms. Entrainment mapping showed that the difference between the post-pacing interval (PPI) and tachycardia cycle length was <50 ms at the lateral wall of the tricuspid annulus and >80 ms at the septal wall (Figure. 2).



Therefore, we concluded that the origin of the circuit was the right atrial free wall rather than the cavotricuspid isthmusdependent reentry, and we performed electroanatomical mapping using the CARTO® 3 system (Biosene Webster, Diamond Bar, Co USA). The activation map revealed that the tachycardia circuit was the right atriotomy scar-related reentry (Figure. 3). Ablation was performed at gaps in the scar area and at the isthmus between the scar and the tricuspid annulus using a Thermocool SF irrigated catheter (Biosene Webster, Diamond Bar, CA, USA) and RF energy with 20-25 W. Tachycardia was terminated during ablation, and bidirectional block was confirmed after ablation.







Discussion

   Intra-atrial reentrant tachycardia related to postoperative scar tissue often develops after open heart surgery; this tachycardia is difficult to manage and may result in significant postoperative morbidity. In this case, the patient had right atriotomy scar-related atypical atrial flutter, which was easy to be misdiagnosed as typical atrial flutter. The structural changes that occur after open heart surgery can serve as substrates for arrhythmias. Treatment of these types of arrhythmias sometimes requires an unconventional approach. Studies have reported that in patients with a history of open heart surgery, atypical arrhythmia can be successfully cured by catheter ablation.7-8 Catheter ablation procedures guided by 3D-mapping systems may increase the ablation success rate and improve patient outcomes.


References

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