Transvenous ICD Systems Research Articles

Single center experience with a totally subcutanous implantable cardioverter defibrillator system

Objectives: Transvenous and epicardial ICD systems are associated with substantial short- and long-term complications concerning lead dysfunction, venous stenosis and infection. Therefore we report our single center expierience with a novel completely subcutanous implantable cardioverter-defibrillator (S-ICD) system.

Advances in ICD Therapy

Amin Al-Ahmad, MD, Guest EditorView Large Image Figure ViewerDownload Hi-res image Download (PPT)We are honored and privileged to serve as editors for this volume on advances in ICD therapy. Since the introduction of the first transvenous ICD systems, there have been numerous advances that have made significant improvements in ICD performance and safety. We have invited experts in the field to discuss many of these important developments. Drs Dewland, Olgin, and Lee lead off the issue with a discussion of the indications for a novel technology, the wearable cardioverter defibrillator. Drs Hill and Dubin then discuss the role of the implantable cardioverter defibrillator in pediatric patients and patients with congenital heart disease. Drs Maytin and Epstein provide a thorough overview of the indications, techniques, and outcomes of ICD lead extraction. Drs Gard and Friedman review the role of supraventricular tachycardia–ventricular tachycardia discriminators to reduce ICD shocks. Drs Prutkin and Poole discuss the topic of complications of ICD generator change and implantations. Drs Refaat and Saba introduce a new technology, the subcutaneous defibrillator. Drs Koneru, Kaszala, Huizar, and Ellenbogen focus on the topic of ICD lead fracture and review its incidence, diagnosis, and strategies to prevent inappropriate ICD therapy. Drs Freeman, Ullal, and Turakhia review the analysis of cost effectiveness of implantable cardioverter defibrillators and cardiac resynchronization therapy. Dr Rea provides insights into novel and unusual methods for ICD lead access. Drs Ford, Cutitta, Woodrow, Kirian, and Sears discuss caring for the heart and mind in ICD patients. Drs Varma and Wilkoff focus on important advances in the remote monitoring of implantable cardiac devices. Drs Hsia, Chia, and Evans discuss the testing of the upper limit of vulnerability and methods of assessing defibrillation threshold. Drs Schoenhard and Zei review methods of reducing ICD shocks for ventricular arrhythmias. Dr Wang discusses new developments in ICD leads and ICD lead configurations. The articles in this issue are designed to highlight the advances in ICDs and how they may translate into improved outcomes and care of patients with ICDs.

Transvenous dual site left ventricular pacing plus biventricular pacing for the management of refractory ventricular tachycardia

This is a case report of a male patient with nonischemic cardiomyopathy who had severely depressed left ventricular systolic function and functional class III congestive heart failure (CHF). He also had left bundle branch block (LBBB) and recurrent ventricular tachycardia (VT). Though the patient's CFH functional class improved after implantation of a transvenous biventricular ICD system, recurrent VT episodes required the initiation of amiodarone. After an improved condition for 28 months, recurrent VT episodes led to multiple consecutive ICD shocks, which constituted an electrical storm and a battery status of elective replacement indicator (ERI). The recurrent VT episodes were suppressed with intravenous amiodarone and lidocaine. As Radiofrequency ablation was declined by the patient, a new left ventricular (LV) lead was transvenously added, providing biventricular and dual site LV pacing. After this intervention the arrhythmia subsided and the intravenous antiarrhythmic medications were stopped. No episodes of sustained VT leading to ICD shocks were observed for the following 9 months. The events in this case suggest that dual site LV pacing with biventricular pacing could be an alternative strategy for the management of refractory VT.

ICD-Schrittmachertherapie bei Kindern und Jugendlichen

The compelling safety and efficacy data in numerous large, blinded trials on adult patients, and the progress in device- and leadtechnology have led to increasing use of implantable cardioverter defibrillators in pediatric patients. The purpose of our study was to assess the efficacy and safety of ICD in the pediatric age group of a tertiary referral centre. Between March 1998 and October 2003 12 patients underwent ICD-implantation. The mean age at implantation was 14,8 years with a range between 10-17 years. The underlying cardiac disorders included long QT-syndrome in 4 patients, ventricular fibrillation in 3 patients, dilated cardiomyopathy in 4 patients, and congenital heart disease in 1 patient (pulmonary atresia with ventricular septal defect after Rastelli repair). All patients received a transvenous ICD-system (VVI-ICD in 4 patients, DDD-ICD in 8 patients). The mean follow up was 35 months (6-68 months). During this period there were no severe complications nor mortality. We haven't seen infections, thromboembolic complications or lead-perforations. 2 patients (17 %) received appropriate DC-shocks, 1 patient (8 %) received an inappropriate DC-shock. 10 patients (83 %) had no malignant ventricular arrhythmia under medical therapy. 2 patients (17 %) required revision because of lead-dysfunction. In 2 patients with DCM the device was explanted during orthotopic heart transplantation. Our data demonstrate that advances in device- and leadtechnology have resulted in a decrease of severe complications in the pediatric age group. We conclude that ICD-implantation represents a safe and effective therapy for children and adolescents with lifethreatening ventricular dysrhythmias. Since it represents an invasive therapy, indication should be confined to patients with lifethreatening dysrhythmias according to the guidelines of the American Heart Association.

A prospective, randomized comparison in humans of defibrillation efficacy of a standard transvenous ICD system with a totally subcutaneous ICD system (The S-ICD® system)

A prospective, randomized comparison in humans of defibrillation efficacy of a standard transvenous ICD system with a totally subcutaneous ICD system (The S-ICD® system)

Correlation of acute and chronic defibrillation threshold with upper limit of vulnerability determined in normal sinus rhythm.

The upper limit of vulnerability (ULV) is the stimulus strength above which ventricular fibrillation cannot be induced, even when the stimulus occurs during the vulnerable period of the cardiac cycle. Determination of ULV using T-wave shocks during ventricular pacing has been shown to closely correlate with the defibrillation threshold (DFT) at ICD implantation. However, there are no data correlating ULV determined in sinus rhythm at ICD implantation, with DFT determined at implantation or during long-term follow-up. This is of clinical importance since ULV may be used to estimate DFT during ICD implantation, both during ventricular pacing or sinus rhythm. Twenty-one patients receiving a transvenous ICD system were studied prospectively. There were 16 males and 5 females, mean age 68 +/- 15 years, with mean ejection fraction 37.4 +/- 17.4%. All had structural heart disease. The ULV was defined as the lowest energy that did not induce ventricular fibrillation with shocks at 0, 20 and 40ms before the peak of the T-wave, using a step-down protocol. The initial energy tested was 15J and the lowest energy 2J. DFT was determined following a similar step-down protocol. The DFT was defined as the lowest energy that successfully defibrillated the ventricles. The linear correlation coefficient between ULV and DFT was r = 0.73 (p < 0.001). At implant, mean ULV was 9.2 +/- 5J, not statistically different from mean DFT 9.4 +/- 4J. ULV plus 5J successfully defibrillated 19 of 21 patients. During long-term follow-up of 10.1 +/- 1.8 months in eight patients, DFT was 8.8 +/- 5.8J, not significantly different than the DFT of 7.5 +/- 4.1J or ULV of 8.0 +/- 5.3 at implant. 1) When determined during normal sinus rhythm the ULV significantly correlates with DFT. 2) ULV testing might be used in lieu of standard DFT testing to confirm adequate lead placement thus minimizing or eliminating VF inductions, particularly in hemodynamically unstable patients. 3) Since ULV + 5J has a high probability of successful defibrillation in most patients, programming ICD first shock energy for VF at ULV + 5J may result in lower first shock energies compared to the standard methods of programming first shock energy at twice DFT. The purpose of this study was to determine if the upper limit of vulnerability (ULV) determined during normal sinus rhythm correlates with the defibrillation threshold (DFT), as has been previously shown when determined during ventricular pacing. The linear correlation coefficient between the ULV and DFT was r = 0.73 (p < 0.001). Mean ULV at implant was 9.2 +/- 5J, not statistically different from mean DFT of 0.4 +/- 4J. During long-term follow-up of 10.1 +/- 1.8 months in 8 patients, DFT was 8.75 +/- 8J, not significantly different than the DFT of 7.5 +/- 4.1J or ULV of 8.0 +/- 5.3 at implant. Shocks energies of ULV + 5J successfully defibrillated 19 of 21 patients at implant and 8 of 8 at follow-up. This study indicates that the ULV determined in normal sinus rhythm closely correlates with the DFT, and that ULV + 5J defibrillated most patients. ULV testing could be used to predict DFT and reduce or eliminate the need for DFT testing and VF induction. Programming ICD first shock energy for VF to ULV + 5J will result in lower energy than that used with standard DFT testing.

Implantable cardioverter-defibrillator dysfunction after coronary artery bypass grafting

Displacement of an ICD electrode is a possible complication after changes in heart size after CABG and simultaneous implantation of an epicardial lead ICD. To prevent potentially life-threatening ICD dysfunction in patients who are candidates for CABG and ICD implantation, we suggest the use of transvenous ICD systems or a staged procedure (CABG followed by ICD implantation) rather than a simultaneous operation.

992-110 Finite Element Analysis of Post-shock Sensing Performance in Transvenous Implantable Defibrillator Lead Systems

Post-shock sensing abnormalities have been observed in transvenous (TV) implantable defibrillator (ICD) lead systems. This may be related to the proximity of the sensing and defibrillation (DF) electrodes, and due to local conduction block in areas of high potential gradients. Potential gradients of &gt; 64 V/cm have been shown to cause local conduction block. To study the effect of lead geometry on potential gradient at the sensing circuit following a high voltage shock, a finite element model was constructed to simulate three TV ICD leads: Endotak 60 TM , TVL TM , and Transvene TM . The first two lead systems use integrated bipolar sensing (tip to distal DF coil); the latter uses true bipolar sensing (tip to ring electrode). The model consisted of a three-dimensional, cylindrically symmetric right ventricle, with the lead surrounded by blood except at the distal electrode, which was in contact with myocardium. The model was calculated assuming an applied voltage of 650 V at the distal DF coil, with the proximal DF coil at 0 V. The potential gradient at each point of a 635 to 824 node finite element model was solved using LaPlace's equation, assuming typical values for conductivity of blood (0.01 S/cm) and myocardium 10.002 S/cm). Potential gradient values at the distal sensing electrode were &lt; 30 V/cm in all TV ICD systems. The potential gradient at the proximal sensing electrode in the Transvene TM was &lt; 30 V/cm. Potential gradients of &gt; 64 V/cm (range 64 to 660 V/cm) were seen at all nodes within 3 mm of the distal DF electrode. Nodes adjacent to the sensing circuit in the true bipolarsensing lead had potential gradients &lt; 30 V/cm, whereas the area surrounding the sensing cathode of integrated bipolar systems had potential gradients &gt; 64 V/cm. This model demonstrates: 1) how post-shock sensing performance may be significantly affected by lead geometry; 2) that integrated bipolar sensing systems may be affected more by shock delivery than true bipolar sensing systems

960-85 Implantation of a Single-Lead Unipolar Transvenous Cardioverter/Defibrillatior (ICD) Under Local Anesthesia

The purpose of this study was to prospectively evaluate single-lead unipolar transvenous ICD implantation under local anesthesia and defibrillator threshold testing under mild sedation. In 12 consecutive patients (mean age. 61 ± 10 years) transvenous ICD implantation was performed (9 patients had ischemic heart disease, 3 patients dilated cardiomyopathy). The presenting arrhythmia was ventricular fibrillation in 4 patients, and monomorphic ventricular tachycardia in 8 patients. Mean LVEF was 26 ± 11%. A single-lead unipolar transvenous ICD with biphasic defibrillation pulse was implanted subpectorally in all patients under local anesthesia with 1% lidocaine. During defibrillation threshold (DFT) testing sedation was applied with 11.5 ± 5.1 mg (0.14 ± 0.05 mg/kg) midazolam. For DFT determination 5.8 ± 1.3 episodes of ventricular fibrillation (mean total ventricular fibrillation time 52.4 ± 14.7 seconds) were induced. Mean OFT was 12.8 ± 4.3 J, mean duration of the implantation procedure was 58 ± 13 minutes. Heart rate. mean arterial blood pressure. and arterial oxygen saturation were not significantly different before and after DFT determination. One patient had moderate pain during DFT testing, and 3 patients had mild pain during the surgical procedure. Symptoms during the procedure were evaluated using a standardized questionnaire. Severe feeling of panic and surprise, and discomfort of moderate degree was reported by 2 patients. There were no complications. Hospital length of stay: all patients were discharged on the second postoperative day. Postimplant ICD testing was performed successfully without sedation 35 ± 1.4 days after ICD implantation, in 6 patients as an outpatient procedure. Single-lead unipolar transvenous ICD systems can safely be implanted under local anesthesia and mild sedation during defibrillation threshold testing. The procedure is well tolerated.

992-112 Compromised Time to Shock Therapy in a Noncommitted Transvenous ICD System

Reduction in electrogram size after an endocardial shock has been associated with sensing problems in some transvenous integrated bipolar shock/sense lead systems. We have previously reported that redetection time (RDT) after a failed defibrillation shock is not prolonged in the 60 series Endotak lead (CPI, St Paul, MN) combined with the Ventak P (committed shock) pulse generator. We performed this study to examine RDT in the non-committed Ventak P2 using the same lead system. In 25 patients (20 male, 15 with coronary disease) undergoing follow-up testing, 84 episodes of failed defibrillation shock were examined for initial detection time (lDT) and RDT as well as failed arrhythmia reconfirmation during capacitor charge (FTR). Event marker output and telemetered data were used to analyze each ventricular fibrillation episode for detection duration excluding the programmed delay and charge time. Mean ( ± SEM) age was 61 ± 3 and ejection fraction was 31 ± 2%. In seconds (s), lDT was 2.83 ± 0.14 and RDT was 4.01 ± 0.31 (p &lt; 0.0001). There were 7 lDT and 18 RDT events ≥ 5s (p = 0.03) and no lDT and 4 RDT events ≥10s. There were 5 FTR events prior to failed shocks, and 19 after such shocks (p = 0.004). Mean energy of failed shocks was 10.8 ± 0.9J. Sensing of VF after a failed shock is significantly prolonged in this ICD system; our data suggest that the requirement for reconfirmation may delay therapy delivery after an initial shock that fails to defibrillate.

Fully transvenous cardioverter defibrillators: Rare need for subcutaneous patch with two newer-generation systems

In published series of nonthoracotomy ICDs, there has invariably been a need for combining transvenous lead(s) with a subcutaneous patch to obtain adequate DFTs. Since the newer generation transvenous lead ICD systems became available for clinical investigation, we have tested and implanted 38 such systems in patients with drug-refractory malignant ventricular arrhythmias who were first seen with aborted sudden death ( n = 10), syncope ( n = 3), or sustained ventricular tachycardia ( n = 25). These patients (mean age 60 ± 15 years) had coronary artery disease ( n = 25), congenital heart disease ( n = 1), or cardiomyopathy ( n = 12) as the underlying heart disease and a mean left ventricular ejection fraction of 34% ± 16%. Seventeen (45%) patients had previous cardiac surgery (coronary bypass and/or valve replacement). The transvenous lead system included the Endotak C (single) lead of CPI ( n = 27) or the EnGuard double-lead system of Telectronics ( n = 11). The integrated pace/sense/defibrillation lead(s) were usually introduced via the left cephalic vein; after endocardiac positioning and testing, the leads were tunneled to the abdominal pocket in which the ICD device was implanted. DFTs were adequate for all patients (100%) and averaged 13.5 ± 5.4 J (range 2.4 to 25 J). A subcutaneous patch or array was needed in only three patients. Because of protocol requirements, a subcutaneous patch or electrode array was intraoperatively tested in another three patients but was finally not implanted because better DFTs were achieved with the transvenous lead-alone configuration. The leads were combined with second-generation devices in 12 patients and third-generation ICDs in 26 (68%) patients. Lead dislodgement required revision in 2 patients; 1 patient had ipsilateral venous thrombosis successfully treated with anticoagulation. At predischarge testing, all devices functioned well. We conclude that with the newer generation transvenous lead ICD systems there is rarely need for a subcutaneous patch, making possible pure transvenous ICD implants in the majority (92%) of patients.