during sinus rhythm using bipolar voltage mapping (voltage�0.5mV in-dicating scar, �1.5mv normal myocardium). Linear catheter ablation wasdirected to the intermediate zone (voltages between 0.5 to 1.5mV) asexit-area of re-entrant VT matched by pace-map.Results: 42 PT (mean EF�34%, 29�12VT-episodes/3months prior ad-mission) were included. 2.4�1.1 VTs were inducible per PT. Electroana-tomic mapping was performed and based on scar findings 68 linear abla-tions were performed (1.0�0.4 per VT). In 95% of patients (40) the clinicalVT was successfully ablated. In 22/40 PTs all inducible VTs were ablated(group A) and in 18 (45%) VTs were still inducible after the ablationprocedure (group B). During a mean follow-up of 18�9months no arrhyth-mia was documented on ICD-holter in 82.5% of ablated PTs. In PTs ofgroup A (complete success) 95% and in group B 61% (p�0.01) were freefrom VT. In group B the number of VT episodes on ICD-holter wassignificantly reduced from 54 to 2 episodes during a 3 month period(p�0.05). 2 PTs died (5%) due to progressive heart failure and acute MI.Conclusions: Substrate mapping during sinus rhythm and scar-basedlinear ablation strategies directed to zones of intermediate voltages arehighly effective in suppressing VT in remote myocardial infarction withlong-term arrhythmia-freedom in over 80%. In 55% complete suppressionof all inducible VTs can be achieved predicting freedom from VT in over90%. Ablation only of the clinical VT significantly reduces the number ofdetected VT-episodes even though new (faster) VTs often occur duringfollow-up. Exact detection of the zone in between scar and normal myo-cardium as target for catheter ablation strategies needs to be optimized.

P6-80

IDIOPATHIC VENTRICULAR TACHYCARDIA- IS IT ALL THATBENIGN?Sharada Kalavakolanu, MD, MBBS, Rajesh Badani, MD,MBBS, Hygriv B. Rao, MD, MBBS and NarasimhanCalambur, MD, MBBS. Care Hospitals, The Institute ofMedical Science, Secunderabad, India and Care Hospitals,The Institute of Medical Science, Hyderabad, India.

Idiopathic ventricular tachycardia (VT) in general is reported to have anexcellent prognosis being relatively benign as compared to scar VTs. Wereport our experience with idiopathic VT wherein there was varied clinicalpresentation with certain atypical and serious clinical features. A total of 83patients (59 males, 24 females) with idiopathic VT underwent electrophys-iological study at our institute between Jan 1999 and July 2004. Rightventricular VT (RV-VT) was present in 30 and left ventricular VT (LV-VT) in 53. Tachycardiomyopathy with significant LV dysfunction was seenin 8: 4 with fascicular tachycardia, 3 with LV outflow tract (LVOT-VT),1with RVOT-VT. Presyncope and syncope as presenting features wereseen in 24 patients, (RV-VT 9, LV-VT 15): 2 with RV-VT having veryrapid rate resembling ventricular flutter and one girl with LV-VT hadresuscitated sudden cardiac arrest (SCA). A 19 year old girl with LV-VTon medical therapy died in her sleep. Resistance to 2 or more anti arrhyth-mic drugs including amiodarone was seen in all these patients. DC cardio-versions for terminating tachycardia episodes were required in 11 patients.Radio frequency catheter ablation (RFCA) was attempted in 80 patientsand was successful in 77. All patients with tachycardiomyopathy under-went successful RFCA with rapid and remarkable improvement in LVfunction. Both the patients with very rapid RV-VT (resembling ventricularflutter) had successful RFCA. Our experience highlights the not so benignpresentation in our patients with idiopathic VT and the gratifying results ofRFCA.

Diagnosis No.LVDysfunction Syncope SCA Cardioversion

MultipleAAD

LV-VT 53 7 15 3 9 6RV-VT 30 1 9 - 5 5

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LOW VOLTAGE MAPPING AND DOMINANT FREQUENCYANALYSIS OF LEFT ATRIAL FIBRILLATIONYoung-Hoon Kim, MD, PhD, Hui-Nam Pak, MD, PhD, HongEuy Lim, MD, PhD, Jin Seok Kim, MD, PhD, Sung-Hee Shin,MD, Mi Young Park, MD, Wan Joo Shim, MD, PhD andYoung Moo Ro, MD, PhD. Korea University CardiovascularCenter, Seoul, Republic of Korea.

Background: We hypothesized that multiple overlay of low voltage zone(LVZ) defined by pacing at different sites relates to the heterogeneousatrial substrate for the initiation and/or maintenance of atrial fibrillation(AF), and also relates to the distribution of the dominant frequency (DF) ofthe atrial electrograms (EGs) during AF.Methods and Results: Eighteen patients (15 males, aged 52�11 years)undergoing noncontact mapping (ESI 3000) guided ablation of left atrial(LA) AF (paroxysmal 12, persistent 6) were included. The multiple overlayof LVZ (�30 % of peak amplitude) was analyzed by virtual unipolar EGs,which were obtained from 256 equally distributed LA endocardial sitesduring sinus rhythm (SR), during pacing at proximal and distal coronarysinus, and pacing at the roof. Fast Fourier transform (FFT) analysis of EGswas performed over 6.8 sec window. Atrial premature beats (APBs) drivenAF (n�6) were consistently originated from the border zone between lowand high amplitude. In parallel, these areas were in close proximity to theDF (6.0�1.2 Hz) registered sites. In contrast, in patients who have sus-tained AF, fixed LVZ rather than functional was related to occurrence ofwave break-up (n�5) or isthmus-like slow conduction area for the transientreentry during AF (n�7). DF (5.7�1.2 Hz) was localized at the areashowing frequent wave break-up responsible for the perpetuation of AF.Conclusions: LVZ defined by pacing at multiple sites of the LA wasclosely associated with wave dynamics when APB initiates AF or AFsustains. DF obtained by spectral analysis of EGs during AF reflects thetriggers in patients with APB-driven AF, whereas wave break-up in pa-tients with sustained AF.

P6-82

A NOVEL PORTABLE WIRELESS MULTI-CHANNEL ECG ANDINTRACARDIAC RECORDING SYSTEMMauricio Arruda, MD, Budimir S. Drakulic, PhD, Marko N.Kostic, BS, Sina Fakhar, PhD and Andrea Natale, MD.Cleveland Clinic Foundation, Cleveland, OH.

Current surface and intracardiac (IC) recording (Rec) systems used duringelectrophysiology (EP) procedures typically use large workstations inter-connected by complex set of cables which may result in significant noise.EP systems rely on a variety of digital filters (DF) to reduce noise. Thisstudy evaluated the use of signal processing technology that would enable12-lead ECG and IC Rec with high signal quality without use of DF.Methods: The wireless EP Rec system consisted of two portable dataacquisition units, one at bedside to provided 12-lead ECG Rec while thesecond unit, positioned next to the IC connection box, provided multi-channel IC Rec. Both units used wireless Bluetooth® technology to trans-mit data to laptop computer. Signal quality of wireless system was com-pared to a conventional (Conv) EP Rec system by simultaneous Rec ofECG and IC signals from the same subject. Also, the two systems wereevaluated using standard IC waveforms from an IC simulator.Results: ECG and 4 IC bipolar channels from the coronary sinus and theablation catheter were recorded in four pts by the Conv and the wirelesssystems. Signal quality (amplitude, morphology and duration) along withbaseline noise level were evaluated. The ECG and the IC signals from thewireless system showed significantly less baseline drift and noise com-pared to a Conv EP Rec system. Importantly, the ECG and IC signalamplitude and morphology appeared different in both systems. In order tobetter understand differences between systems, both were connected inparallel to IC simulator and Rec were analyzed. Waveforms were greatlydistorted by the Conv EP system, particularly when Rec with notch filters.

S328 Heart Rhythm, Vol 3, No 5, May Supplement 2006