AB13-4

S26

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

Background: Surgical interventions, including passive restraining devices, can decrease ventricular dilation and improve heart failure. We tested an implantable ventricular support device consisting of a self-anchoring selftensioning nitinol wireform harness containing 2 pair of integrated defibrillation electrodes (Paracor Medical) that connected to an ICD. The implant was placed on the epicardium of the left (LV) and right (RV) ventricles through a subxiphoid approach using an introducer and delivery system. We assessed the lead integrity, defibrillation threshold (DFT), hemodynamic responses, and histopathology following 42-180 days of implantation. Methods: The device was implanted into 12 healthy dogs (23-30 kg). The implant connector leads and a bipolar epicardial pace-sense lead (Medtronic) were tunneled to an ICD (Guidant). Shock lead impedance, DFT and blood pressures were determined at implantation and at the terminal study (42, 90, or 180 days). Results: Implantation was performed successfully in all 12 dogs. Shock lead impedance was significantly decreased at explant compared to baseline (Table). The DFT was unchanged over time. Mean LV and RV pressures were significantly less at explant but within expected normal ranges. No signs of constriction were evident. Histopathology (up to 90 days) indicated mild to moderate epicardial inflammation and fibrosis that did not extend into the myocardium, consistent with typical foreign body healing response. Conclusion: This novel defibrillation-enabled ventricular support system, implanted through a subxiphoid incision, induced typical chronic healing responses and provided defibrillation and mechanical functionality for up to 6 months.

Shock lead Mean ⫾ SD, impedance DFT *P⬍0.05 (Ohms) (Joules) Baseline Terminal Study

45 ⫾ 5 39 ⫾ 4*

8⫾3 7⫾2

Mean aortic pressure (mm Hg)

Mean Mean right Mean LV pulmonary atrial Mean RV pressure wedge pressure pressure (mm Hg) (mm Hg) (mm Hg) (mm Hg)

105 ⫾ 19 50 ⫾ 11 3 ⫾ 2 84 ⫾ 19* 38 ⫾ 8* 2 ⫾ 2

0⫾1 0⫾1

6⫾2 4 ⫾ 1*

Mean pulmonary artery pressure (mm Hg) 8⫾3 7⫾1

AB13-2 USE OF LEFT VENTRICULAR RATE-SENSING ELECTROGRAMS FOR VENTRICULAR FIBRILLATION DETECTION IN ICD PATIENTS Jian Cao, PhD, Paul R. Steiner, MD and Jeffrey M. Gillberg, MS. Medtronic, Inc., Minneapolis, MN and DartmouthHitchcock Medical Center, Lebanon, NH. Purpose: A coronary sinus lead and a biventricular implantable cardioverterdefibrillator (ICD) have been occasionally used for sensing in a patient with poor sensed right ventricular (RV) amplitude (e.g., RV dysplasia). However, detection of ventricular fibrillation (VF) with a left ventricular (LV) lead alone has not been well studied. We retrospectively compared the detection times of induced VF among LV and RV sensing vectors. Methods: Patients (pts) undergoing ICD implant or replacement were enrolled in this study (4 males, 7 females; 67 ⫾ 11 years, ejection fraction ⫽ 25 ⫾ 7%). An external system was used for recording high-fidelity intracardiac electrogram (EGM) directly from Medtronic ICD leads (4 LV true bipolar, 6 LV unipolar, and 10 RV true bipolar; 8 chronic, 12 acute). EGM signals from RV and LV sensing vectors were fed into a model for RV sense amplifier and the VF detection times were computed (VF detection interval ⫽ 320 ms, 12/16 initial detection). All patient data were tested at two programmed sensitivities and paired T-test was performed. Results: Table 1 Comparison of VF detection times (mean ⫾ std, seconds) Ventricular sensitivity (mV)

0.3 1.2

RV sensing

LV sensing

RVtip to RVring (10 pts)

RVtip to RVcoil (10 pts)

LVtip to LVring (4 pts)

LVtip to RVcoil (6 pts)

3.09 ⫾ 0.50 3.12 ⫾ 0.41

2.89 ⫾ 0.48 2.97 ⫾ 0.39

3.46 ⫾ 0.54 3.77 ⫾ 0.78

3.07 ⫾ 0.48 3.18 ⫾ 0.73

The intrinsic R-wave amplitude was high for RV (8-20 mV) and LV (6-29 mV). At sensitivity of 0.3 mV, LV and RV sensing configurations resulted in appropriate detection of all VF episodes with similar detection times (Table I). No significant VF undersensing was observed for all cases. At sensitivity of 1.2 mV, 2-3 beats of VF undersensing occurred in 6 cases from 3 pts (2 LVtip to RVing, 1 LVtip to RVcoil, 2 RVtip to RVring and 1 RVtip to RVcoil). The VF detection times (1.2 mV vs. 0.3 mV sensitivity) were not significantly different for each sensing vector (P ⬎ 0.4). Conclusions: Appropriate detection of ventricular fibrillation was not compromised by the use of left ventricular only sensing configurations (LVtip to LVring or RVcoil). VF sensing from a coronary sinus lead is feasible with a standard RV sense amplifier. AB13-3 COMPARISON OF DEFIBRILLATION EFFICACY WITH ICD LEADS IN THE RVA VS. RVOT S. Ingo Ender, Sr., MD, Mark Landers, MD, John Strobel, MD, Manisha Ashar, MD and Manish S. Gupta, MS. Ann Arundel Medical Center, Annapolis, MD, First Health Moore Regional Hospital, Pinehurst, NC, Bloomington Hospital, Bloomington, IN, Duke University Medical Center, Durham, NC and St. Jude Medical, Sylmar, CA. Background: Prior studies have shown that ventricular pacing from the right ventricular outflow tract (RVOT) may be more beneficial than pacing from the right ventricular apex (RVA). However, few studies have been designed to test whether patients requiring an implantable cardioverterdefibrillator (ICD) can be effectively defibrillated with a lead positioned at the RVOT. If subsequent studies demonstrate that successful defibrillation with sufficient safety margin can be obtained in the RVOT position, then placement of the ICD lead at the RVOT may be a preferred position in patients who require frequent pacing. Methods: This acute, paired-sample, randomized study included 47 ICD pts (64⫾13 years, 78% male, LVEF 27⫾11%). Each patient underwent defibrillation threshold (DFT) testing at two RV sites: RVA and RVOT with randomization of the initial site. A four-shock Bayesian up-down procedure was used to assess DFTs in each position. The shocking polarity and shocking coil configuration were held constant during each DFT testing. Results: The lead positioned in RVA resulted in a 2.5 J lower DFT compared to RVOT lead position (p⫽0.0037). All standard measurements were within normal limits in both RVA and RVOT groups (Table). Multivariate analysis revealed that the clinical baseline characteristics (age, gender, NYHA Class and EF), did not significantly affect DFT.

Shock Impedance (␻) DFT (J) DFT (V) Pacing threshold (V) @ 0.5 ms Pacing Impedance (␻) R-Waves (mV)

RVA

RVOT

P value

44.3 ⫾ 6.5 9.2 ⫾ 4.9 429.8 ⫾ 114.3 0.67 ⫾ 0.32

41.3 ⫾ 6.3 11.7 ⫾ 5.8 489.7 ⫾ 127.9 0.66 ⫾ 0.26

⬍0.0001 0.0037 0.0005 NS

570.8 ⫾ 106.6 12.7 ⫾ 5.5

549.8 ⫾ 109.7 10.2 ⫾ 4.4

NS 0.015

Conclusion: Safe and effective termination of ventricular arrhythmias with sufficient energy safety margin can be obtained with ICD leads placed at the RVOT. AB13-4 INITIAL CLINICAL EVALUATION OF A NEW FAR-FIELD SIGNAL REDUCTION (FSR) PACING LEAD IN THE RIGHT ATRIUM Cm Yu, MD, Johannes Sperzel, MD, W. H. Fung, MD, Gerd Fro¨hlig, MD, R. N. Gelder, MD, Michael Yang, PhD, Peter Boileau, MS, Eric Falkenberg, MS, Ryan Rooke, BS, John Helland, MS, Yougandh Chitre, MS, Gene A. Bornzin, PhD and Laura Fischer, MS. Prince of Wales Hospital, Hong Kong, SAR China, Kerckhoff Klinik GmbH, Bad Nauheim,

Session 13

S27

Germany, Universita¨tskliniken des Saarlandes, Homburg/ Saar, Germany, Monash Medical Center, Melbourne, Australia and St. Jude Medical, Sylmar, CA. Objectives: The efficacy of the new St Jude Medical (SJM) Far-Field Signal Reduction (FSR) lead, based upon optimization of the tip-to-ring electrode spacing (1.1 mm) and surface areas, has been demonstrated by chronic animal studies and acute human testing. This study, for the first time, was designed to evaluate the chronic sensing and pacing performance of the new FSR leads in pacemaker patients. Methods: 62 patients were randomized to receiving either the new FSR pacing lead or a control lead with conventional spacing (10 mm, SJM Tendril Model 1688T) at implant, with a dual chamber SJM Identity™ or ADx pacemaker. The majority of the leads were placed in the RA Appendage. Standard pacing/ sensing measurements and a far-field R-wave (FFRW) sensing threshold test were conducted for each patient at implant, prior to hospital discharge, and at 10, 40, and 90-day post implant follow-up visits, respectively. Results: At the 90 day follow up, none of 31 FSR lead patients exhibited any FFRW sensing at a threshold of 0.2mV, versus 5 of 24 control lead patients. 6 of 31 FSR lead patients exhibited FFRW sensing at a threshold of 0.1mV, versus 11 of 24 control patients. The average FFRW amplitude sensed by FSR leads was 0.02 mV versus 0.11 mV for the control leads. The mean bipolar pacing threshold, P-wave amplitude, and impedance of FSR leads at 90-day post implant were 0.6 V, 2.5 mV, and 409 ⍀, respectively - all typical values. Conclusions: FSR leads in the right atrium of these typical pacemaker patients performed safely, achieving a significant far-field signal reduction throughout the 90 day follow up. The FSR leads’ overall sensing and pacing performance was excellent, suggesting that the new FSR Lead has significant potential to provide improved pacemaker therapy and performance. AB13-5 DECLINING IMPEDANCE IN AGING BIPOLAR VENTRICULAR PACING LEADS: WHAT DOES IT MEAN AND WHAT DO I DO ABOUT IT? INTERIM RESULTS OF A 5 YEAR PROSPECTIVE STUDY W. Ben Johnson, MD, Beth Kaiser, RN, Deb French, MA, Loline Voegtlin, RN, Alan Braly, BS, Kenneth Cobian, BS and Rick McVenes, BS. Iowa Heart Center, P.C., Des Moines, IA and Medtronic, Inc., Minneapolis, MN. Mechanical properties of polyurethane (PU) provide clinically meaningful benefit in pacing leads. 55D PU clearly outperforms its predecessor 80A material, and will continue to be used in future implantable leads. Therefore, we need to understand PU lead (LD) aging and management. Methods: Models 4024 and 5024 are similar bipolar (BP) ventricular LDs except inner and outer insulation: 55D PU and MDX silicone, respectively. 140 (4024) and 102 (5024) pts with LDs implanted ⬎6 years were enrolled and followed 3⫹ times/year. Impedance (Z), stimulation thresholds (STs) and R-wave amplitudes were collected at each follow-up. The total populations were compared. For each model, data from year 3 of the study were compared to the 6-year enrollment point. Results: Comparison of Model 4024 and 5024 populations at enrollment and year 3 interim endpoints Endpoint time Enrollment Endpoint (⬃6 Yrs Implant Time) Year 3 Interim Endpoint (Last follow-up as of 11/14/05)

Follow-up data

4024 (N⫽140 enrolled)

5024 (N⫽102 enrolled)

P-Value

Lead Age (yrs) Bipolar Impedance (Ohms) Lead Age (yrs)

6.19⫹/⫺0.27 (131) 616⫹/⫺151 (128)

6.21⫹/⫺0.30 (92) 664⫹/⫺124 (90)

0.604 0.011

10.20⫹/⫺1.99 (140)

10.33⫹/⫺1.61 (102)

0.575

Bipolar Impedance (Ohms)

535⫹/⫺180 (129)

663⫹/⫺132 (95)

0.000

Bipolar Threshold at 2.5V (ms) Bipolar Threshold at 1.5V (ms)

0.11⫹/⫺0.06 (73)

0.11⫹/⫺0.13 (31)

1.000

0.18⫹/⫺0.17 (110)

0.13⫹/⫺0.09 (82)

0.009

(1) BP and UP Z for the populations were statistically different (SD) and continue to trend apart. (2) At 2.5V, 4024 and 5024 BP STs were not SD at the interim endpoint. BP STs at 1.5V were SD between the populations, confirming earlier observation suggesting subclinical performance changes occur in the aging 4024 LDs. (3) 19/140 4024 LDs had BP Z ⬍ 300 ␻. LDs with BP Z ⬍ 300 ␻ (but ⬎ 200 ␻) all had acceptable safety margin at outputs ⱖ 2.5 V. No oversensing was observed. 10/19 low Z LDs were replaced or capped. (4) Of these19 LDs, the shortest interval to sustained BP Z ⬍ 300 ␻ from ⬎450 ␻ was 8.3 months. Only 2/19 had intervals ⬍12 months, and they were both ⬎10 years old. Conclusions: Low Z evolution continues in the 4024 vs. the 5024 population. Slow change to BP Z ⬍ 300 ␻ has been observed in 19/140 LDs, detectable by standard follow-up practice. No oversensing was observed. No BP ST changes at ⱖ 2.5 volt outputs occurred in LDs with ⬎ 200 ␻. 4024 LDs exhibit an acceptable pattern of aging compatible with normal follow-up practice. We continue to follow these aging LDs as their performance past 10 years is unknown. AB13-6 ICD LEAD FAILURE - WHEN TO REPLACE THE ICD LEAD AND WHEN TO ADD A PACE / SENSE LEAD (P/S) Jens Eckstein, MD, Markus Zabel, MD, Dietrich Kalusche, MD, Beat Scha¨r, MD, Stefan Osswald, MD and Christian Sticherling, MD. University Maastricht Cardiovascular Research Institute, Maastricht, The Netherlands, University Hospital Benjamin Franklin, Charite´, Berlin, Germany, Herzzentrum, Bad Krozingen, Germany and University Hospital Basel, Basel, Switzerland. Background: Defibrillator-lead failure such as lead fracture, insulation defect, loss of sensing or oversensing is a potential problem in pts with implantable cardioverter defibrillator (ICD). The aim of this retrospective study was a) to determine the incidence of clinically relevant ICD-lead problems, b) to elicit the main causes of these problems, and c) to evaluate the feasibility and safety of solving the problem by implanting either an additional P/S lead only, or a new ICD-lead. Methods: 1484 patients implanted with an ICD at 3 European centers between March 1993 and January 2004 were followed for 77⫾ 39 months (range: 9 - 148 months). Patients with ICD-lead related problems (n⫽38) were identified and classified as to the kind of complication, the longevity and type of the implanted lead. If the integrity and correct function of the high voltage part of the ICD lead could be documented, only an additional P/S lead was implanted. After revision, these patients were followed for 36⫾ 29 months (range: 2 - 118 months). Results: The incidence of ICD-lead related problems was 2,6% (38 /1484 pts). Inappropriate sensing or lead dysfunction resulted in inappropriate ICD therapies in 29/38 pts (76%). Causes were artefact oversensing in 9/38 pts (24%), T-wave oversensing in 5/38 pts (13%), insulation defect in 10/38 pts (26%), lead fracture in 9/38 pts (24%), and other problems in 6/38 pts (13%). The therapeutic approach consisted of implantation of an additional P/S lead in 24 (63%) and placement of a new ICD lead in 13 pts (34%). Six pts (13%) had a third intervention due to recurrent lead problems after 45⫾ 33 months (range: 10 - 95 months). One of those required revision of an additionally implanted P/S-lead. 2 required placement of a new ICD lead after initial placement of a additional P/S lead (21 and 42 months later) and 3 patients required the placement of a P/S lead after previous implantation of a new ICD lead. Conclusion: ICD-lead failure is a clinical problem and occurs in 2.5 % of the ICD population. If it is possible to prove the integrity of the high voltage portion of the ICD lead, these problems can be solved by simply adding an additional P/S lead. This approach is feasible and safe.