Gender-based clinical outcomes for atrial fibrillation ablation

Session 13 width above the 8 week threshold. Severe increase was defined as ⬎/⫽ 2V or a ⬎ 3 fold increase in pulse width above the 8 week threshold. Results: Two of 66 (3.0%) patients had a moderate increase in RV threshold at 3 and 15 months. Both thresholds stabilized and did not require lead revision. Moderate to severe increases (3-43 months post implant) in LV pacing thresholds (12 patients, 18.2%) were significantly more common (P⫽ 0.0088). Ten of these 12 patients were reprogrammed to maintain clinical efficacy with or without a standard energy (2 times voltage threshold or 3 times pulse width threshold) safety margin. Severe threshold increases (6) were seen only in LV leads (P⫽ 0.0112). Two patients with severe threshold increases required lead revision. Conclusion: Changes in pacing thresholds are significantly more common in LV than RV leads. Moderate pacing threshold changes did not require lead revision. Severe LV threshold changes may not require invasive intervention. A prospective trial designed to examine the impact of specific lead technologies on chronic LV lead performance seems warranted. AB13-3 EVALUATION OF AUTOMATED ELECTROCARDIOGRAM INTERPRETATION IN CHILDREN: MODELING INFLUENTIAL FACTORS Christine C. Chiu, BSc, *Robert M. Hamilton, MD, FRCP, Robert M. Gow, MD, *Joel A. Kirsh, MD, FRCP, Mary Corey, PhD, Edward Etchells, MD, Elizabeth A. Stephenson, MD, Gabriele Bronzetti, MD, Gil J. Gross, MD and *Brian W. McCrindle, MD, MPH. The Hospital for Sick Children, Toronto, Ontario, Canada and Sunnybrook & Woman’s College Health Sciences Center, Toronto, Ontario, Canada. Background: Computer assisted interpretation (CAI) of electrocardiogram (ECG) has not been widely used by pediatric cardiologists (MD) due to a perceived high interpretation error rate. Objective: We sought to determine the factors affecting disagreements between MD and CAI (Marquette 12SL™). Methods: ECG from patients with congenital heart disease (CHD, n⫽586) or structurally normal heart (NOR, n⫽561) were reviewed to compare disagreement between the overreading pediatric electrophysiologist (MD1 or MD2) and CAI using the kappa and McNemar’s statistics. Logistic regression was used to model for significant independent factors impacting on disagreement and the adjusted odds ratios (OR) are reported. Results: There were more disagreements in ECG from CHD (146/586, 25%) compared with NOR (64/561, 11%) (p ⬍0.001). Kappa values (95% confidence interval) for agreement between MD and CAI were as follows:

McNemar’s statistics were significant in the following areas(p⬍0.05): CAI overcalling prolonged QT, sinus rhythm ⫹ ectopy and RVH in CHD; CAI undercalling sinus rhythm, sinus arrhythmia and RBBB in CHD. Logistic modeling showed that disagreement with CAI was independently associated with CHD (OR 2.7), and patient age at ECG: age ⬍ 1 years old (OR 1.7) and age 16 - 18 years old (OR 2.4) compared to age 1 to 7 and 8 to 15 years olds (OR 1.0). Disagreement was also more likely for MD1 vs. MD2 (OR 2.9), consistent with substantial interobserver variability (5060%). Conclusions: The independent predictors of disagreement between MD and CAI were presence of CHD, extremes of age at ECG (younger than 1 years or older than 16 years) and the overreading MD. In general, despite good agreement between MD and CAI interpretation of ECG, verification by experienced overreader remains crucial. Areas of CAI that required improvements included rhythm diagnosis, recognition of RBBB and RVH.

S25 AB13-4 PREDICTION OF PACING LEAD ELECTRODE HEATING IN THE MRI RADIO FREQUENCY FIELD USING A TRANSMISSION LINE MODEL *Piotr T. Przybyszewski, PhD and *Stephen Kuehn. Medtronic, Minneapolis, MN. Background: Interaction between Radio Frequency (RF) fields, generated by an MRI scanner, with pacing leads in a patient may lead to significant heating near the pacing electrode. The lead may act as a transmission line, picking up electromagnetic energy distributed along its length. This distributed set of sources excites an electromagnetic wave within the lead body. Part of this wave is dissipated near the pacing electrode causing heating. In order to prevent thermogenic tissue damage and to design MRI safe leads, it is important to understand the physics of these effects. Methods: Pacing leads were modeled as lossy transmission lines with distributed sets of voltage sources. Lead model parameters were obtained via simulations based on the Finite Difference Time Domain (FDTD) method. %Distributed voltage was obtained from FDTD simulations of a human body inside an MRI RF coil. A transmission line simulator was used to calculate the power dissipated in the tissue near the lead electrode surface. Power was converted to temperature rise using bio-heat equation solvers. Results: Simulations were performed for different lead types, lengths, and various anatomically correct lead paths. Results were compared with measurement data for a body phantom placed in an RF coil. In both cases, good agreement between results of simulations and measurements were observed. The model was able to predict the worst-case heating scenarios: resonant lead lengths and lead paths corresponding to the highest heating. Conditions for MRI safety for different leads were established. Conclusion: A transmission line lead model enables accurate prediction of electrode heating in the MRI RF field. The model contributes to a better understanding of heating effects, lead design, and MRI safety conditions. AB13-5 GENDER-BASED CLINICAL OUTCOMES FOR ATRIAL FIBRILLATION ABLATION *Liza A. Prudente, RN, CNP, *John D. Ferguson, MD, MBBS, *J. Paul Mounsey, MD, PhD, James P. Hummel, MD, *John P. Dimarco, MD, PhD, Adam Clark, MD, *Robert A. Vernooy, MD and *J. Michael Mangrum, MD. University of Virginia, Charlottesville, VA. Data from the RACE study has recently shown that a rate-control treatment strategy for persistent atrial fibrillation (AF) in females may be preferable to a rhythm-control strategy due to adverse effects of antiarrhythmic drugs. Catheter ablation for the treatment of AF is becoming a more common treatment for both paroxysmal and persistent AF. Little is known about gender differences on patient selection or clinical outcomes for ablation therapy for AF. Methods: We performed a retrospective analysis of pts with paroxysmal or persistent atrial fibrillation who underwent ablation for AF using NavX (Endocardial Solutions, Inc) and intracardiac echocardiography (ICE) (Boston Scientific). The cohort consisted of pts who underwent initial ablation for AF from 11-03 to 11-04. Collected demographic data included gender, age, type of AF, type of ablation strategy, follow-up time since procedure, and clinical response. Atrial ablation strategies were pulmonary vein isolation (PVI) or left atrial circumferential ablation (LACA). Success is defined as no symptomatic recurrence. Results: A total of 76 pts (male 48, female 28) were evaluated. Age: M 52 ⫾ 10, F 59 ⫾ 10; p ⫽ 0.003; Follow-up (days): 205 ⫾ 113, F 163 ⫾ 97; p ⫽ 0.01 More males with persistent AF, 21 (44%) were referred for ablation than females, 8 (28%). (See table below) Overall, the clinical success rates were 73% for males, 82% for females; p ⫽ NS. In subgroup analysis, clinical success rates were high for both genders with PVI for pts with paroxysmal AF ( M - 96%; F - 95%; p ⫽ NS) and LACA for pts with persistent AF (M - 67%; F - 100%; p ⫽ 0.04). Conclusions: In our cohort more males are referred for AF ablation but clinical success rates are equally high for both genders.

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Heart Rhythm, Vol 2, No 5, May Supplement 2005 and Claus Schmitt, MD. German Heart Center, Munich, Germany.

AB13-6 ANTICOAGULATION DURING ATRIAL FIBRILLATION ABLATION *Cindy L. Russell, RN, Liza A. Prudente, RN,MSN,ACNP-C, John D. Ferguson, MD, MBBS, J. Paul Mounsey, PhD, PhD, James P. Hummel, MD, John P. Dimarco, MD, PhD and J. Michael Mangrum, MD. University of Virginia, Charlottesville, VA. Background: Radio Frequency (RF) ablation of Atrial fibrillation (AF) has become a viable option for those patients with symptomatic AF (paroxysmal and persistent). RF ablation of AF requires extended procedure time in the left atrium (LA). Adequate procedural anticoagulation is necessary in order to prevent thromboembolic events, such as stroke. There is no standard anticoagulation protocol for LA procedures. We sought to determine the optimal, safe anticoagulation dosage and protocol to achieve and maintain ACT of 300-350 seconds. Methods: All patients undergoing ablation for AF from April-November 2004 participated in the study. After the trans-septal puncture patients were then anticoagulated with one of three pre-determined weight based dosage regimens, beginning with the standard protocol heparin administration for Acute Coronary Syndrome (ACS). The regimen included an initial bolus and continuous infusion. Group 1(ACS) ⫽ 80units/kg(bolus); 18units/kg/ hr(infusion)(80/18): Group 2⫽ 90/19: Group 3⫽100/20. Results: A total of 62 (45 males) were studied. Mean age 57 ⫹/-(10). At 30 minutes the mean ACT’s were 246 ⫹/-30; 282 ⫹/-55; 292 ⫹/-36, ( P⫽0.02; group1 vs2 : P⫽⬍0.001; group 1 vs 3 ). Therapeutic ACT at 30 minutes was achieved in 5%, 22%, 45% of patients with subsequent heparin adjustment neccessary in 95%, 83% and 45%, Groups 1-3, respectively. No thromboembolic or hemorrhagic events were seen. Conclusion: Weight based nomogram for heparin use during prolonged LA procedure is safe. Standard dosing regimen used in ACS is inadequate. A dose of at least 100/20 is necessary to achieve target ACT levels for most patients. Further study is needed at higher doses.

ABSTRACT SESSION 14: CATHETER ABLATION IV: Clinical Outcomes II Thursday, May 5, 2005 2:15 p.m.–3:45 p.m. AB14-1 LEFT ATRIAL REENTRANT TACHYCARDIA AFTER CIRCUMFERENTIAL PULMONARY VEIN ABLATION FOR ATRIAL FIBRILLATION - INCIDENCE, ELECTROPHYSIOLOGICAL CHARACTERISTICS AND RESULTS OF RADIOFREQUENCY ABLATION Isabel Deisenhofer, MD, Heidi Estner, MD, Ju¨rgen Schreieck, MD, Bernhard Zrenner, MD, Konstanze Scharf, MD, Christian Von Bary, MD, Etienne Luciani, MD, Agathe Konietzko, MD, Martin R. Karch, MD, Gjin Ndrepepa, MD

Background: Circumferential pulmonary vein ablation (CPVA) has emerged as a curative approach for ablation of atrial fibrillation (AF). However, left atrial reentrant tachycardia (LART) as a sequel after CPVA is increasingly recognized as a clinical issue. Methods and Results: This study included 67 patients (P; 57⫾7 years, 43 male) with paroxysmal (57 P) or persistent (10 P) AF who underwent CPVA guided by electroanatomical mapping. Overall, 29/67 P (43%) experienced atrial tachycardia after CPVA. In 8 P, atrial tachycardia occurred only transiently, the remaining 21 (31%) P developed incessant left atrial tachycardia 3.2 ⫾ 3.1 months after initial CPVA. Of them, 16 patients underwent one or two (mean 1.3 ⫾ 0.5 per P) mapping/ablation procedures for LART. A total of 55 LARTs (3.4⫾2.4 per P and 2.7 ⫾ 1.5 LART per procedure) were mapped. Of these, 18 (33%) LART were related to macro-reentry around an anatomic electrical barrier: 7 LART circled around the mitral annulus and 11 around one ore more ipsilateral pulmonary veins. In 20 LART (36%), a “small loop” reentry could be identified: They were related to gaps in prior linear lesions (7 LART) or were determined by an area of extremely slow conduction adjacent to the former lesions (11 LART) with fractionated potentials covering up to 60% of the cycle length. The remaining 17 tachycardias could not be mapped due to instability of arrhythmias. In 34/38 (89%) completely mapped LARTs, ablation was primarily successful. In a follow-up of 10.4 ⫾ 6.7 months (range 3-24 months), LART relapsed in 7 patients and 3 patients experienced episodes of AF in addition to LART. Conclusion: CPVA with PV-encircling lesions and an additional left isthmus line is associated with the development of sustained LART in a high percentage of patients. The underlying mechanisms differ (macro-reentry and small loop reentry), there are multiple and often instable variants of LART in one patient and the reentry circuits tend to be very small. Thus, mapping and ablation of these LART can be challenging and long-term success is yet not satisfactory. AB14-2 THE ADDITIVE EFFICACY OF A NOVEL BALLOON CRYOABLATION CATHETER TO STANDARD CRYOABLATION FOR PV ISOLATION IN PATIENTS WITH SYMPTOMATIC ATRIAL FIBRILLATION Shephal K. Doshi, MD, Margaret Laragy, *Heinz F. Pitchner, MD, *Jim Irwin, MD, *Christopher Cole, MD, *Petr Neuzil, MD, PhD, *Malte Kuniss, MD, *Jeremy N. Ruskin, MD and *Vivek Y. Reddy, MD. Massachusetts General Hospital, Boston, MA, Kerckhoff Klink, Bad Nauheim, Germany, St. Joseph’s Hospital, Tampa, FL, Memorial Hospital, Colorado Springs, CO and Homolka Hospital, Prague, Czech Republic. Background: Cryothermal energy is thought to be safe for PV isolation, and there is increasing interest in its use for treating patients with AF. A novel balloon cryoablation catheter (BC) has been developed to rapidly isolate the PVs. This report examines the efficacy of the BC when used in conjunction with linear (Arctic Circler⫽AC) and focal (Freezor Extra or Max) cryocatheters in symptomatic, paroxysmal AF (PAF) patients. Methods: The population included symptomatic drug-resistant paroxysmal AF patients from 2 separate studies: A) a 3-center study of 24 pts undergoing PVI using the AC and focal (Extra) catheters, or B) a 2-center study of 20 pts undergoing PVI using the BC in addition to the AC and focal (Max) catheters (Cryocath Technologies, Inc.). In both studies, all 4 PVs were treated and patients were followed for symptomatic AF recurrences. Results: Procedural success for PVI in both studies was similar: 88/89 (98%) in A vs 74/78 (95%) in B; in study B, 50/67 PVs (75%) were isolated using the BC alone. One pt in B underwent repeat cryoablation at 5 months. MR imaging at 3 months revealed no PV stenosis in all pts in