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P1-67
Poster 1 transvenous ICD implantation volunteered for defibrillation threshold (DFT) testing of 4 distinct electrode configurations: 1) 60cc lateral can-8cm parasternal coil electrode; 2) 60cc lateral can-5cm2 parasternal disk electrode; 3) 60cc pectoral can-8cm inframammary coil electrode; and 4) a 60cc pectoral can-4cm paraxiphoid coil electrode. Configurations were randomly tested. Defibrillation testing followed 10 seconds of induced ventricular fibrillation starting at 40J using a standard step-up, skip-down protocol and a 50-50 tilt biphasic waveform. Results: DFTs were: 1) LCan-8cm ⫽ 27J (⫾11); 2) LCan-5cm2 ⫽ 32J (⫾12); 3) PCan-8cm ⫽ 38J (⫾10); 4) PCan-4cm ⫽ 39J (⫾15). There were significant differences between configurations 1 and 3, p ⫽ 0.03 and 1 and 4, p ⫽0.04. Conclusion: Optimal defibrillation appears to require a lateral canister position. However, DFT differences for the various S-ICD systems appear relatively insensitive to configuration if a high-energy output S-ICD (60-80J delivered) was used. This finding suggests that the insertion technique for the S-ICD system may be somewhat forgiving to precise location, similar to transthoracic defibrillation, but unlike transvenous systems.
P1-66 PREDICTIVE VALUE OF T-WAVE ALTERNANS RECORDED FROM ELECTROGRAMS OF IMPLANTABLE CARDIOVERTERDEFIBRILLATOR Offir Paz, MD, Xiaohong Zhou, MD, Tracey Gerez, RN, Jennifer Grannis, MS, Hsiang-Jer Tseng, MS, Athula Abeyratne, PhD, Eli S. Gang, MD and Charles D. Swerdlow, MD. Cedars-Sinai Medical Center, Los Angeles, CA and Medtronic, Inc., Minneapolis, MN. Microvolt T-wave alternans (TWA) on the surface ECG increases acutely prior to VT/VF in animals, suggesting that TWA recorded from ICD electrograms (EGMs) may warn of VT/VF in ICD pts. We have shown TWA has greater amplitude on ICD EGMs than on the ECG. But it is not known if EGM TWA represents the same pathophysiological process as ECG TWA, which is a good long-term predictor of spontaneous VT/VF. This study investigated the predictive value of EGM and ECG TWA. Methods: In 25 pts with dual-chamber ICDs and intact AV conduction, we recorded TWA during trials of atrial and AV pacing. Each trial consisted of 3 min of pacing at each of 3 rates (80, 95, and 110 bpm) for a total of 9 min per trial. EGM TWA was measured off line by spectral analysis. EGM TWA was positive (⫹) if either pacing method produced sustained alternans ⱖ 30 V with K score (signal-to-noise ratio) ⱖ 3. Simultaneously, ECG TWA was analyzed by a commercial system (CHS2000, Cambridge Heart, Inc). ECG TWA was positive if either pacing method produced sustained alternans ⱖ 1.9 V with K score ⱖ 3. The endpoint was appropriate ICD therapy for VT/VF during follow-up ⱖ 6 months. Results: TWA tests were positive in 10 pts (40%) by ECG and in 13 pts (52%) by EGM. ECG and EGM TWA results were concordant in 21 pts (84%). During median follow-up of 7 months (range 6 - 13 months), 7 pts had appropriate ICD therapy. Of these, 6 pts had positive TWA tests by both ECG and EGM, and 1 pt had negative (⫺) TWA tests by both ECG and EGM. The Figure shows that both ECG TWA (p ⫽ .006) and EGM TWA (p ⫽ .035) predicted event-free survival rate from appropriate ICD therapies. Conclusion: In ICD pts, ECG and EGM TWA have a high degree of concordance and similar predictive value for spontaneous VT/VF. This suggests that they represent the same pathophysiological process. Further studies are needed to determine if EGM TWA can serve as an immediate warning for VT/VF in ICD pts.
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P1-67 EFFECTS OF A RATE SMOOTHING ALGORITHM FOR PREVENTION OF VENTRICULAR ARRHYTHMIAS: RESULTS OF THE VENTRICULAR ARRHYTHMIA SUPPRESSION TRIAL (VAST) Paul A. Friedman, MD, Scott Brown, PhD, Darin R. Lerew, PhD and The VAST Investigators. Mayo Clinic, Rochester, MN and Guidant Corporation, St. Paul, MN. Background: Rate Smoothing (RS), available in some pacemakers and implantable cardioverter defibrillators (ICDs), has been used in an attempt to prevent torsade de pointes in patients with long QT syndrome. Its efficacy in general ventricular arrhythmia prevention however, has not been determined. The objective of the VAST was to prospectively investigate whether RS could significantly reduce the incidence of ventricular tachyarrhythmias in a large, broad population of patients with ICDs. Methods: Five-hundred-sixty-nine patients with standard indications for ICDs were enrolled at 57 participating centers and implanted with a commercially available Guidant ICD. A single blinded crossover design was used, in which each patient was randomized at implant to one of two treatment sequences, either RS ON followed by RS OFF, or RS OFF followed by RS ON. This mode sequence was randomly determined, and assigned in a 1:1 fashion using randomized permuted blocks by site. Each mode was followed for six months. Programming of RS was prescribed as 12% DOWN and 12% UP for the duration of the RS ON period. Event electrograms were adjudicated. Results: Of enrolled patients, 281 were randomized to RS OFF, then ON, and 288 to RS ON, then OFF. Seventy-five patients (23%) experienced a reduction in arrhythmias with RS ON, while 76 (23%) saw an increase, and the remaining 176 (54%) had no difference in arrhythmias with RS ON versus RS OFF. We found no significant difference (p⫽ 0.58) in frequency of arrhythmias with RS ON versus RS OFF. Data were also analyzed using from the first six-month crossover period only; neither frequency of arrhythmias (p⫽0.24) nor number of patients experiencing arrhythmias (p⫽0.17) demonstrated a significant difference between randomization groups. Conclusion: VAST is the largest prospective study to investigate the applicability of RS in the prevention of arrhythmias. Although RS may benefit certain patient subpopulations such as those with Torsades de pointes type arrhythmias, current results do not indicate effectiveness of RS for reduction in ventricular arrhythmias in a heterogenous ICD population. P1-68 FOUR YEAR SURVIVAL IN 1285 PATIENTS UNDERGOING CARDIAC RESYNCHRONIZATION THERAPY (CRT): THE IMPORTANCE OF ATRIOVENTRICULAR JUNCTION ABLATION IN PATIENTS WITH PERMANENT ATRIAL FIBRILLATION Maurizio Gasparini, MD, Angelo Auricchio, MD, PhD, Barbara Lamb, MD, Antonio Curnis, MD, Catherine Klersy, MD, DMSc, Marco Metra, MD, Ju¨rgen Voigt, MD, Mihoko Kawabata, MD, PhD, Franc¸ois Regoli, MD and Edoardo Gronda, MD. IRCCS, Instituto Clinico Humanitas, Milano, Italy, University Hospital Magdeburg, Magdeburg, Germany, Heart Center, Bad Oeynhausen, Germany, Division of Cardiology, Brescia, Italy and IRCCS, Policlinico S. Matteo, Pavia, Italy.
P1-66 PREDICTIVE VALUE OF T-WAVE ALTERNANS RECORDED FROM ELECTROGRAMS OF IMPLANTABLE CARDIOVERTERDEFIBRILLATOR Offir Paz, MD, Xiaohong Zhou, MD, Tracey Gerez, RN, Jennifer Grannis, MS, Hsiang-Jer Tseng, MS, Athula Abeyratne, PhD, Eli S. Gang, MD and Charles D. Swerdlow, MD. Cedars-Sinai Medical Center, Los Angeles, CA and Medtronic, Inc., Minneapolis, MN. Microvolt T-wave alternans (TWA) on the surface ECG increases acutely prior to VT/VF in animals, suggesting that TWA recorded from ICD electrograms (EGMs) may warn of VT/VF in ICD pts. We have shown TWA has greater amplitude on ICD EGMs than on the ECG. But it is not known if EGM TWA represents the same pathophysiological process as ECG TWA, which is a good long-term predictor of spontaneous VT/VF. This study investigated the predictive value of EGM and ECG TWA. Methods: In 25 pts with dual-chamber ICDs and intact AV conduction, we recorded TWA during trials of atrial and AV pacing. Each trial consisted of 3 min of pacing at each of 3 rates (80, 95, and 110 bpm) for a total of 9 min per trial. EGM TWA was measured off line by spectral analysis. EGM TWA was positive (⫹) if either pacing method produced sustained alternans ⱖ 30 V with K score (signal-to-noise ratio) ⱖ 3. Simultaneously, ECG TWA was analyzed by a commercial system (CHS2000, Cambridge Heart, Inc). ECG TWA was positive if either pacing method produced sustained alternans ⱖ 1.9 V with K score ⱖ 3. The endpoint was appropriate ICD therapy for VT/VF during follow-up ⱖ 6 months. Results: TWA tests were positive in 10 pts (40%) by ECG and in 13 pts (52%) by EGM. ECG and EGM TWA results were concordant in 21 pts (84%). During median follow-up of 7 months (range 6 - 13 months), 7 pts had appropriate ICD therapy. Of these, 6 pts had positive TWA tests by both ECG and EGM, and 1 pt had negative (⫺) TWA tests by both ECG and EGM. The Figure shows that both ECG TWA (p ⫽ .006) and EGM TWA (p ⫽ .035) predicted event-free survival rate from appropriate ICD therapies. Conclusion: In ICD pts, ECG and EGM TWA have a high degree of concordance and similar predictive value for spontaneous VT/VF. This suggests that they represent the same pathophysiological process. Further studies are needed to determine if EGM TWA can serve as an immediate warning for VT/VF in ICD pts.
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P1-67 EFFECTS OF A RATE SMOOTHING ALGORITHM FOR PREVENTION OF VENTRICULAR ARRHYTHMIAS: RESULTS OF THE VENTRICULAR ARRHYTHMIA SUPPRESSION TRIAL (VAST) Paul A. Friedman, MD, Scott Brown, PhD, Darin R. Lerew, PhD and The VAST Investigators. Mayo Clinic, Rochester, MN and Guidant Corporation, St. Paul, MN. Background: Rate Smoothing (RS), available in some pacemakers and implantable cardioverter defibrillators (ICDs), has been used in an attempt to prevent torsade de pointes in patients with long QT syndrome. Its efficacy in general ventricular arrhythmia prevention however, has not been determined. The objective of the VAST was to prospectively investigate whether RS could significantly reduce the incidence of ventricular tachyarrhythmias in a large, broad population of patients with ICDs. Methods: Five-hundred-sixty-nine patients with standard indications for ICDs were enrolled at 57 participating centers and implanted with a commercially available Guidant ICD. A single blinded crossover design was used, in which each patient was randomized at implant to one of two treatment sequences, either RS ON followed by RS OFF, or RS OFF followed by RS ON. This mode sequence was randomly determined, and assigned in a 1:1 fashion using randomized permuted blocks by site. Each mode was followed for six months. Programming of RS was prescribed as 12% DOWN and 12% UP for the duration of the RS ON period. Event electrograms were adjudicated. Results: Of enrolled patients, 281 were randomized to RS OFF, then ON, and 288 to RS ON, then OFF. Seventy-five patients (23%) experienced a reduction in arrhythmias with RS ON, while 76 (23%) saw an increase, and the remaining 176 (54%) had no difference in arrhythmias with RS ON versus RS OFF. We found no significant difference (p⫽ 0.58) in frequency of arrhythmias with RS ON versus RS OFF. Data were also analyzed using from the first six-month crossover period only; neither frequency of arrhythmias (p⫽0.24) nor number of patients experiencing arrhythmias (p⫽0.17) demonstrated a significant difference between randomization groups. Conclusion: VAST is the largest prospective study to investigate the applicability of RS in the prevention of arrhythmias. Although RS may benefit certain patient subpopulations such as those with Torsades de pointes type arrhythmias, current results do not indicate effectiveness of RS for reduction in ventricular arrhythmias in a heterogenous ICD population. P1-68 FOUR YEAR SURVIVAL IN 1285 PATIENTS UNDERGOING CARDIAC RESYNCHRONIZATION THERAPY (CRT): THE IMPORTANCE OF ATRIOVENTRICULAR JUNCTION ABLATION IN PATIENTS WITH PERMANENT ATRIAL FIBRILLATION Maurizio Gasparini, MD, Angelo Auricchio, MD, PhD, Barbara Lamb, MD, Antonio Curnis, MD, Catherine Klersy, MD, DMSc, Marco Metra, MD, Ju¨rgen Voigt, MD, Mihoko Kawabata, MD, PhD, Franc¸ois Regoli, MD and Edoardo Gronda, MD. IRCCS, Instituto Clinico Humanitas, Milano, Italy, University Hospital Magdeburg, Magdeburg, Germany, Heart Center, Bad Oeynhausen, Germany, Division of Cardiology, Brescia, Italy and IRCCS, Policlinico S. Matteo, Pavia, Italy.