Stable chronic trans-coronary venous left ventricular pacing using an active fixation lead

Poster 1 P1-58 EXPERIENCE WITH CARDIOVERTER-DEFIBRILLATOR IMPLANTATION IN HIGH-RISK PATIENTS WITH HYPERTROPHIC CARDIOMYOPATHY Adrian K. Almquist, MD, Julia V. Montgomery, MD, Tammy S. Haas, RN and Barry J. Maron, MD. Hypertrophic Cardiomyopathy Center, Minneapolis Heart Institute Foundation, Minneapolis, MN. Objectives: Implantable defibrillators (ICD) are frequently employed in patients with hypertrophic cardiomyopathy (HCM), for primary and secondary sudden death prevention. Due to the unique clinical and phenotypic expression of HCM, including extreme left ventricular (LV) hypertrophy, obstruction to LV outflow, electrically unstable myocardium, and youthful age of some candidates, clinical concerns not uncommonly arise regarding the safety and efficacy of device implantation. Methods: We analyzed the single institution experience at the Minneapolis Heart Institute, 1993 to 2004, involving ICDs with transvenous lead systems in 72 consecutive high-risk HCM patients. Results: The study group was 12 to 79 years of age (mean 37 ⫾ 15) at the time of implant. Four patients received ICDs for secondary prevention and 68 had implants for primary prevention of sudden death i.e. with ⱖ 1 risk factors. Twenty-eight patients demonstrated disease features potentially impacting the methodology and safety of implant, i.e. massive LV hypertrophy (n ⫽ 20); LV outflow obstruction ⱖ 50 mm Hg at rest (n ⫽ 10) and disabling heart failure symptoms (n ⫽ 5). There were no procedure-related deaths, and ICD implants were considered successful and uneventful in 69 of the 72 patients (96%). Of note, in the 3 other patients (4%), defibrillation via standard transvenous leads was unsuccessful due to high defibrillation thresholds (DFT), i.e. associated with massive LV hypertrophy (wall thickness, 48 mm and 55 mm) in 2, and ongoing therapy with amiodarone in one. In 2 of these patients, thoracotomy with epicardial lead placement was necessary to achieve successful defibrillation; ICD therapy was ultimately abandoned in the other patient. Conclusions: ICD implantation in children and adults with HCM is generally safe and effective. However, in some patients with massive LV hypertrophy and/or prior administration of amiodarone, transvenous defibrillation proved difficult and epicardial lead placement was required. High-energy ICD devices and DFT testing are recommended for high-risk HCM patients. P1-59

S123 without complications. Chest x-rays showed no instances of lead dislodgment. Pacing threshold and sensing values are shown in the table below (mean ⫾ 1 SD):

None of the changes in pacing threshold and sensing were statistically significant. Gross and histopathologic evaluations of the two canines showed: no evidence of lead dislodgement, perforation, or coronary venous-arterial injury. These CDAF lead electrical and pathologic findings are similar to historical canine testing of passive fixation LV lead Model 4193. Conclusion: Trans-coronary venous left ventricular pacing is feasible using active fixation leads and provides acceptable chronic electrical lead performance and stability, validated by benign gross and histopathologic evaluations. P1-60 RELATIONSHIP BETWEEN LV PACING THRESHOLDS, R-WAVE AMPLITUDES, AND IMPEDANCES TO LV VEIN SIZE AND LOCATIONS IN A BIPOLAR LV LEAD *W. Ben Johnson, MD, Robert Hoyt, MD, *Steve Bailin, MD, *Mark J. Mayotte, MS, *Alex Shih, PhD and *Amy Boschee, BA. Iowa Heart, DesMoines, IA and Medtronic, Inc., Minneapolis, MN. Purpose: The Medtronic Model 4194 (Attain® Bipolar OTW) US Clinical Study was a prospective, non-randomized, multicenter clinical trial that evaluated a new 6 Fr. LV bipolar lead in patients receiving a CRT system. A CRT system, including a CRT device and a Model 4194 LV lead was successfully implanted in 165 patients. Data was collected on LV bipolar (LVB) and LVtip-RVring (LVRV) pacing thresholds, bipolar R-wave amplitudes (BRW) and impedances during implant. Additional data was collected on LV lead location and LV vein size. There have been previous reports suggesting that LV pacing thresholds (in linear or non-curved or non-canted leads) may get worse as the vessel size gets larger relative to the electrode diameter (due to lack of electrode contact). We investigated the relationships between LV vein size and location and the LV pacing thresholds, R-wave amplitudes, and impedances. Results: The results are shown in the tables below.

STABLE CHRONIC TRANS-CORONARY VENOUS LEFT VENTRICULAR PACING USING AN ACTIVE FIXATION LEAD *Raymond Yee, MD, *Laurie Foerster, *John Sommer, *Terry Williams and *Zan Tyson, MD. London Health Sciences Center, London, Ontario, Canada, Medtronic, Inc., Minneapolis, MN and Carolina Regional Heart Center, High Point, NC. Background: We previously demonstrated successful acute trans-coronary venous (TCV) left ventricular pacing using active fixation (AF) leads in an animal model, but the chronic performance of AF leads in coronary veins is unknown. Accordingly, we sought to characterize the chronic electrical performance and tissue changes of a novel catheter delivered active fixation (CDAF) lead during long-term implantation. Methods: Six isoflurane-anesthetized closed chest canines were implanted with a unipolar steroid eluting CDAF lead. The coronary sinus was cannulated and coronary venogram obtained using an Attain guide sheath. A sub-selecting delivery catheter was advanced through the guide sheath and over a guide wire into the desired coronary vein branch. The lead was then advanced through the delivery catheter and fixation was achieved by lead rotation. Chest X-rays, pacing threshold and R waves were taken at prespecified intervals. In order to verify safety, necropsies were performed on two canines at twelve weeks post implant. Results: TCV AF leads were successfully implanted in all six animals

There were no statistically significant differences between LV tip locations (basal, middle, or apical) with respect to LVB, LVRV, BRW, and Bipolar ⍀ (p-values 0.914, 0.867, 0.506, and 0.455, respectively). The correlation between LV vein size and LVB was non-significant (p⫽0.166, adj. R2⫽0.006). Nor was there a significant correlation between LV vein size and LVRV (p⫽0.082, adj. R2⫽0.013). Conclusions: Contrary to previous reports on non-curved or non-canted LV leads, there does not appear to be a significant relationship between the LV vein size or tip location and LV pacing thresholds in the Attain® Bipolar OTW lead. Additionally, LV R-waves, or bipolar impedances did not vary significantly with LV lead location. The compound curve in the