bluuebunny/crossref_metadata_2025 huggingface dataset:
Proposal of a Method for Automatic Optimization of Left Heart Atrioventricular Interval Applicable to DDD Pacemakers
Authors: CHIRIFE RAUL
Published: July 2006

Electrical pacing of the right heart is known to cause delays in the depolarization of left heart chambers, leading to abnormal left heart AV sequence. Interatrial conduction time, defined as the time from the right atrial pacing pulse or intrinsic P to the onset of left atrial P wave, and P wave sensing delay cause a shorter left heart AV interval during atrial pacing‐ventricular sensing and atrial sense‐ventricular pace. Interventricular conduction time (the time from the right ventricular pacing pulse to the onset of left ventricular depolarization), lengthens left heart AV interval during atrial sensing‐ventricular pacing. These delays may add up or partly cancel out, depending on pacing mode. Thus, an algorithm for DDD pacemakers to optimize left heart AV interval by compensating for the above delays is proposed. This algorithm takes into account pacing and sensing delays to deliver a certain AV sequence to the right heart, aimed at producing a physiological left heart AV interval. The optimization of left heart AV interval is achieved by automatically changing right heart AV interval and pacing mode in accordance with known interatrial and interventricular conduction delays, and P wave sense offset.
Comparison of Externally Strapped Versus Implanted Accelerometer‐ or Vibration‐Based Rate Adaptive Pacemakers During Various Physical Activities
Authors: ROBERTS DAVID H. , BAXTER SUSAN E. , BRENNAN PAULA T. , GAMMAGE MICHAEL D.
Published: July 2006

The ability of externally strapped accelerometer(Excel [Cardiac Pacemakers, Inc.]) and vibration‐based (Activitrax [Medtronic, Inc.]) rate adaptive pacemakers to reproduce the rate response of the same implanted devices with identical programming was evaluated in ten patients by ambulatory Holter monitoring. The resting and postexercise external pacemaker rates closely resembled those of the respective implanted devices. During short bursts and more prolonged exercise, both types of strapped‐on devices underestimated maximal implanted pacemaker rate response by4%‐10% when programmed to nominal rate adaptive settings. Studies evaluating chronotropic responses from either type of externally strapped activity sensor appear valid, provided the modest attenuation in maximal rate increase by this method is appreciated.
A Direct Comparison of Epicardial and Nonthoracotomy Defibrillation Using Monophasic and Biphasic Shocks
Authors: THAKUR RANJAN K. , SOUZA JOSEPH J. , TROUP PAUL J. , CHAPMAN PETER D. , WETHERBEE JULE N.
Published: July 2006

Defibrillation using epicardial patches may be associated with lower energy requirements than nonthoracotomy defibrillation although a direct comparison using various waveforms has not been reported. To directly compare defibrillation efficacy using these two configurations, nine mongrel dogs (20.9 ± 2.3 kg) first underwent nonthoracotomy defibrillation testing followed by a thoracotomy and implantation of epicardial patch electrodes and redetermination of defibrillation efficacy. Each dog served as its own control. Nonthoracotomy electrode configuration consisted of a right ventricular catheter (cathode) and a chest wall subcutaneous patch (anode). The epicardial configuration consisted of two 13.9 cm2 epicardial patches. Alternating current induced ventricular fibrillation was allowed to persist for 10 seconds, followed by either a monophasic or a single capacitor biphasic shock of 10‐msec total duration. Four trials of five leading edge voltages were performed for monophasic and biphasic pulses and stepwise logistic regression analysis was used to determine 80% probability of successful defibrillation (E80). For epicardial defibrillation E80s were: monophasic 19.2 ± 4.2 J and biphasic 12.6 ± 4.0 J; nonthoracotomy defibrillation E80s were: monophasic 24.2± 4.4 J and biphasic 17.8 ± 4.1 J. Epicardial patch defibrillation required less energy than nonthoracotomy electrode configuration. However, using biphasic pulses nonthoracotomy defibrillation could achieve lower defibrillation energy requirements than epicardial defibrillation with monophasic pulses.
Hemodynamic Recovery, Atrial Natriuretic Peptide, and Catecholamines During Simulated Ventricular Tachycardia: Effects of Ventriculoatrial Conduction
Authors: PEUHKURINEN KEIJO J. , UUSIMAA PAAVO A. , RUSKOAHO HEIKKI , LINNALUOTO MARKKU , HUIKURI HEIKKI
Published: July 2006

Ventriculoatrial (VA) sequence and neurohumoral responses may be important modulators of hemodynamic recovery during VT. We studied the effects of VA conduction on blood pressure recovery, and levels of atrial natriuretic peptide (ANP), epinephrine, and norepinephrine during simulated VT. After diagnostic coronary angiography, VT was simulated by rapid right ventricular pacing (150 beats/min, 3 mins) in a consecutive series of patients. Whenever the patients demonstrated VA dissociation during ventricular pacing, they were included in the study. After 10 minutes of recovery, a group of nine patients then underwent an additional VA pacing (150 beats/min, 3 mins, VA delay of 150 msec). Intra‐arterial blood pressure was continuously monitored, and plasma ANP and catecholamine levels were measured before, during, and after both pacing protocols. The mean arterial pressures declined rapidly by 26% and 30% after initiation of ventricular and VA pacing, respectively. The blood pressure then gradually recovered, the hemodynamic recovery being better during VA pacing. Plasma ANP and catecholamine levels increased toward the end of both pacing periods. The observed increase in ANP concentration was more prominent during VA pacing than ventricular pacing (P < 0.001), whereas catecholamine levels increased similarly. The results show that during simulated VT hemodynamic recovery is partially dependent on VA sequence. The increases in circulating ANP and Catecholamines occur too slowly to account for the rapid changes in blood pressures observed after initiation of simulated VT. Therefore, other mechanisms, such as reflex stimulation of the sympathoadrenergic nervous system, must be involved, too. ANP release increases when atrial contraction frequency increases, but the exact determinants for this release remain unknown.
Catheter Interruption of Atrioventricular Conduction Using Radiofrequency Energy in a Patient with Transposition of the Great Arteries
Authors: RUSSELL MARK W. , DOROSTKAR PARVIN C. , DICK MACDONALD , CRAENEN JOSEPHA , FRANKLIN WAYNE , ARMSTRONG BRIAN
Published: July 2006

Percutaneous catheter mapping andradiofrequency ablation of the AV node‐His bundle system (with subsequent transvenous endocardial ventricular pacing) were performed on an 18‐year‐old woman with transposition of the great arteries and intact ventricular septum and chronic arrhythmias 15 years following a Mustard operation. Exclusion of the AV conduction tissue from the systemic venous circulation by the complex anatomy and the Mustard repair was circumvented by a retrograde approach across the aortic valve to the morphological right ventricle yielding access to the AV node‐His bundle system.
Epicardial and Nonthoracotomy Defibrillation Lead Systems Combined with a Cardioverter Defibrillator
Authors: TRAPPE HANS‐JOACHIM , FIEGUTH HANS‐GERD , PFITZNER PETRA , HEINTZE JOHANNES , WENZLAFF PAUL , KIELBLOCK BIRGIT
Published: July 2006

The intraoperative and long‐term results were reviewed in 67 patients who underwent implantation of the Ventritex Cadence defibrillator with either epicardial patch (EPI, 25 patients) or nonthoracotomy CPI Endotak (ENDO, 42 patients) defibrillation lead systems. In the ENDO group, 35 patients (83 %) had a defibrillation threshold (DFT) of ≤ 20 joules and did not require a subcutaneous patch. Intraoperatively, the DFT was 13 ± 9 joules (mean ± SD) for EPI and 15 ± 8 joules for ENDO (P = NS). There was no perioperative death in either group. During a mean follow‐up of 12 ± 8 months, there was no sudden death, and four patients died from congestive heart failure (3 EPI, 1 ENDO). During follow‐up, 875 spontaneous arrhythmia episodes (AE) occurred in 15 of 25 EPI patients (60%). versus 652 in 28 of 42 ENDO patients (67%; P = NS). Ventricular tachycardia at a rate ≥ 222 beats/min or ventricular fibrillation represented 167 AE for EPI (19%) and 182 AE for ENDO (28%), and was terminated by the first shock in 76% and 75% of attempts, respectively. Ventricular tachycardia at a rate ≥ 222 beats/min represented a total of 1,178 AE and antitachycardia pacing was successful in 660 of 708 AE (93%) with EPI and 414 of 470 AE (88%) with ENDO lead systems (P= NS). Therefore, a nonthoracotomy approach using the Cadence V‐100 is safe and effective and has clinical results that are not significantly different from epicardial defibrillation lead systems.
Results of Delivered Therapy for VT or VF in Patients with Third‐Generation Implantable Cardioverter Defibrillators
Authors: RABINOVICH RAFAEL , MURATORE CLAUDIO , IGLESIAS RICARDO , GONZALEZ MIGUEL , SERAFRICA MARIO , LIPRANDI ALVARO SOSA
Published: July 2006

Third‐generation implantable cardioverter defibrillators (ICDs) offer tiered therapy and can provide significant advantage in the management of patients with life‐threatening arrhythmias. Three different types of ICDs were implanted in 21 patients with ventricular tachycardia (VT) or ventricular fibrillation (VF). Arrhythmia presentation was VT(76%), VF(10%), or both (14%). The mean left ventricular ejection fraction for the group was 32.4 ± 7%. No surgical mortality occurred. Prior to discharge individual EPS determined the final programmed settings of the ICDs. During a mean follow‐up of 13 ± 1.4 months (range 2–20) the overall patient survival was 85.7%. No sudden arrhythmic or cardiac death occurred. Twenty of 21 patients (95%) received therapy by their device. In 14 patients (67%) antitachycardia pacing (A TP) was programmed “on,” 13 of which was self‐adaptative autodecremental mode. There were 247 VT episodes, 231 of which were subjected to ATP with 97% success and 3% acceleration or failure. Low energy shocks reverted all other VT episodes. VF episodes were successfully reverted by a single shock (93%), two shocks (6%), or three shocks (1 %). We conclude that ATP therapy of VT is successful in the large majority of episodes with rare failures, and that VF episodes are generally terminated by a single ICD shock.
Safety of Antitachycardia Pacing in Patients with Implantable Cardioverter Defibrillators and Severely Depressed Left Ventricular Function
Authors: HEISEL ARMIN , NEUZNER JÖRG , HIMMRICH EWALD , PITSCHNER HEINZ F. , LIEBRICH ANDREAS , JUNG JENS , SEN SEMI
Published: July 2006

The purpose of this study was to investigate the efficacy and safety of antitachycardia pacing (ATP) in third‐generation implantable Cardioverter defibrillators (ICDs) for terminating spontaneously occurring ventricular tachycardias (VTs) in patients with severely depressed left ventricular (LV) function. Ninety‐one patients with active ATP were followed for 16 ± 13 months. During this period, 775 VT episodes occurring in 36 patients were treated by ATP. The patients were divided into two groups according to their LV ejection fraction (LVEF): group A with LVEF ± 30% (n = 20), and group B with LVEF ± 30% (n = 16). There were no differences between both groups in age, gender, underlying heart disease, indication for ICD therapy, or drug therapy. The VT rates were comparable (group A: 183 ± 16 beats/min; group B: 180 ± 21 beats/min; P = NS). Eighty‐three percent of all episodes (n = 332) in group A and 93% of the VTs (n = 443) in group B were ATP terminated (P ± 0.01). Ten percent of VTs in group A were accelerated by ATP into the ventricular fibrillation zone versus 2% in group B (P ± 0.01). The individual termination rate and acceleration rate per patient were comparable in both groups. All VT episodes unresponsive to ATP were converted by backup shocks. The efficacy of first‐shock therapy was similar in both groups (group A: 89%; group B: 97%; P = NS). The proportion of patients who needed at least one backup shock for unsuccessful ATP was comparable in both groups (group A: 65%; group B: 56%; P= NS). We conclude that ATP is effective and safe in patients with recurrent VTs and severely depressed LV function, and it can be safely programmed in this group of patients to minimize the use of shock therapy.
Subpectoral Implantation of ICD Generators: Long‐Term Follow‐Up
Authors: THAKUR RANJAN K. , IP JOHN H. , MEHTA DAVENDRA , JUNG JIA Y. , COLLAR ALONSO , CAMUNAS JORGE , GOMES J. ANTHONY
Published: July 2006

A nonthoracotomy surgical approach using an endocardial electrode and combined implantation of a subcutaneous patch and the implantable cardioverter defibrillator (ICD) generator in a Subpectoral pocket has been described. We report the long‐term follow‐up results in patients undergoing implantation using this approach. The patient population consisted of 28 patients (22 men and 6 women) with a mean age of 59 ± 12 years. The underlying heart disease consisted of coronary artery disease in 20 patients and dilated cardiomyopathy in 8 patients. Sustained ventricular tachycardia was the mode of presentation in 16 patients and sudden cardiac death in 12 patients. The mean left ventricular ejection fraction was 31%± 6%. The lead system consisted of an 8 French bipolar passive fixation rate sensing lead positioned at the right ventricular apex, an 11 French spring coil electrode positioned at the superior vena cava‐right atrial junction (surface area 700 mm2), and submuscular placement of a large patch (surface area 28 cm2) on the anterolateral chest wall near the cardiac apex via a submammary incision. A defibrillation threshold of ≤ 15 joules (J) was required for implantation. This criterion was not satisfied in five patients; thus, a limited thoracotomy was performed via the submammary incision, and the large patch was placed epicardially. The mean R wave amplitude was 12 ± 3 mV, the mean pacing threshold was 1.0 ± 0.5 V at 0.5 msec, and the mean defibrillation threshold was 12.6 ± 3 J. ICD generators implanted were the Ventak‐P in 17, PCD‐7217 in 5, and the Cadence V‐l00 in 6 patients. These patients have been followed for a mean of 14.6 ± 6 months. There was no perioperative mortality, and none of the patients developed an infection during follow‐up. Generator migration or significant discomfort requiring ICD repositioning was not observed, although one patient developed an erosion requiring surgical repair.Conclusions: Subpectoral implantation of the ICD generator is feasible and was well tolerated by all patients with an acceptable complication rate (3.5%). As the size of future generation ICDs is reduced, subpectoral implantation may become the preferred approach.
Cost and Length of Hospital Stay: Comparisons Between Nonthoracotomy and Epicardial Techniques in Patients Receiving Implantable Cardioverter Defibrillators
Authors: LUCERI RICHARD M. , ZILO PHILIP , HABAL SALEM M. , DAVID IRVING B.
Published: July 2006

Twenty‐five patients with implantable Cardioverter defibrillators (ICDs) implanted intrathoracically (group I) were compared with 25 patients who underwent implant using the nonthoracotomy approach (group II). AH systems were implanted by the same medical team, in the same high volume implanting center. Indications for implantation were comparable in both groups. Patient characteristics were not statistically different with the exception of age fee‐group I vs 71‐group II; P < 0.05). Although left ventricular ejection fractions appeared to differ (32% vs 37%, respectively), this difference was not statistically significant (P = 0.06). ICD models used in group I were: Ventritex Cadence (16), Telectronics Guardian 4211 (2), Medtronic PCD (7); in group II they were: Ventritex Cadence (15), Guardian 4211 (2), and CPI 1600 (1). Total length of hospital stay was 16 ± 6 days for group I versus 12 ± 5 for group II (P < 0.05). Number of postoperative days in an intensive care unit was 3.2 ± 2.8 for group I versus 0.5 ± 0.6 for group II (P < 0.0001). Postoperative length of stay was 8.2 ± 3.1 for group I versus 5.7 ± 4.4 for group II (P < 0.001). Mean total hospital charges for the entire length of stay were $72,918 ±$26,770 in group I versus $55,031 ±$42,870 in group II, representing a mean reduction of 21 % in global costs for group II patients. These data confirm that nonthoracotomy ICD implantation in an experienced center is associated with significantly shorter hospital stays, a virtual elimination of the need for postoperative intensive care, and globally lower total hospital costs. In addition, the presence of a statistically older population in group II does not negate these beneficial effects.
Low Incidence of Lead Related Complications Associated with Nonthoracotomy Implantable Cardioverter Defibrillator Systems
Authors: FAHY GERARD J. , KLEMAN JAMES M. , WILKOFF BRUCE L. , MORANT VICTOR A. , PINSKI SERGIO L.
Published: July 2006

Implantable cardioverter defibrillators (ICDs) are increasingly being implanted without the need for thoracotomy. Long‐term lead performance and stability were evaluated in 150 consecutive patients in whom 1 of 3 nonthoracotomy ICD lead systems was implanted over a 3‐year period from September 1990. Results: Twelve (8%) patients (7 males, 5 females) experienced 13 lead complications during a follow‐up period of 12 ± 10 months. Complications were related to intracardiac leads in 7 (4 dislodgments, 2 fractures, 1 right ventricular perforation) and patch leads in 6 (2 folding, 1 fracture, 1 erosion, and 2 hematomas) cases. Freedom from lead related complications at 1 year was 92% (95% confidence interval, 86%–95%). A significant difference in freedom from lead complications between the two most frequently implanted lead systems was observed (P = 0.02). Complication rates were similar in the initial 75 and the more recent 75 implants (P= 0.5). The median time between lead implant and detection of complications was 37 days (range 3–1,147). Complications were diagnosed before hospital discharge in only two cases. In five patients, complications were asymptomatic and in three of these, reoperation was required due to inadequate defibrillation thresholds. Reoperation was necessary in 9 of 12 patients. Conclusions: Nonthoracotomy ICD lead systems are associated with a low complication rate. Complications may or may not cause symptoms, usually occur after hospital discharge, and require reoperation. Complications are not related to a “learning curve.” There is a significant difference in performance between different lead systems.
Alternative Lead Positioning in the Right Ventricular Outflow Tract in Transvenous Implantation of ICDs
Authors: WOLFHARD ULRICH F. , JAGER H.P. , KNOCKS M. , DOETSCH N.
Published: July 2006

Pacing and sensing failure in apical right ventricular coil electrode PCD implantation due to ventricular scars or aneurysma may force the implanting surgeon to switch to more invasive procedures such as subxyphoidal pericardiotomy or thoracotomy for epimyocardial corkscrew electrode and for epicardial patch application. In order to avoid this more invasive operation in the most severely impaired patients, right ventricular outflow tract positioning of the RV electrode is suggested as an alternative RV electrode site for implantation. A study of four cases shows that this occasional procedure is a practicable method to avoid more invasive techniques. Excellent pacing, sensing, and defibrillation characteristics were obtained and application is relatively simple.
Effect of Implantable Nonthoracotomy Defibrillation System on Permanent Pacemakers: An In Vitro Analysis with Clinical Implications
Authors: VAN LAKE PAUL J. , LEVINE PAUL A. , MOUCHAWAR GABRIEL A.
Published: July 2006

Implantable cardioverter defibrillation systems are capable of delivering over 700 volts, and upwards of 40 joules (J) directly to the heart. Nonthoracotomy lead (NTL) systems allow the delivery of this energy to the inside of the heart, and potentially in close proximity to the leads of an endocardial pacing system. The effect of repeated maximal energy discharges (stored energy 40 J, delivered energy 38 J), utilizing both monophasic as well as biphasic shock pulses delivered via two different configuration NTL systems on a series of Pacesetter polarity programmable present generation single, and dual chamber pacemakers was evaluated in vitro using a saline test tank. All pulse generators studied demonstrated normal function and were not reprogrammed nor adversely affected by repeated defibrillation shocks. The current induced in the leads was assessed, and shown to be as high as 1.5 amps in the proximal conductor and 1.2 amps in the distal conductor of the ventricular lead, which may cause damage at the electrode‐myocardial interface, and explain some of the postshock rise in capture and sensing thresholds that have been reported with implanted pacing systems postdefibrillation.
Effects of Internal Defibrillation on an Implanted Pacing System with Programmable Polarity
Authors: KHOURY DIRAR S. , ZHU WEI‐XI , NITTA JUNICHI , RIZO‐PATRON CARLOS , MALONEY JAMES D.
Published: July 2006

Management of multiple cardiac arrhythmias in some patients with both an implantable cardioverter defibrillator (ICD) and a pacemaker has demonstrated several advantages. In such circumstances, it is imperative that pacemaker function and its programmed parameters be preserved following a deftbrillation shock. This article describes the effects encountered by a specific programmable polarity pacemaker (Relay® 294–03) when subjected to electrical defibrillation in a canine model. Three pacemakers were repeatedly tested in three separate dog experiments. Each pacemaker, with its leads implanted in the right atrium and the right ventricle, was subjected to a minimum total number of 24 high energy biphasic and monophasic shocks (600–700 V) delivered by a coexisting ICD system using three different defibrillating lead configurations. None of the pacemaker systems showed any failure in function; all pacemakers continued to function within preshock specification and conversion to unipolar pacing and/ or backup mode was not observed in any of the tests. Intracardiac electrical potentials measured directly off the ICD and the pacemaker leads, during a defibrillation shock (mean 566.6 V; 23.7 J), showed that potentials measured in a bipolar configuration (tip‐ring: mean 21.0 V in atrium, 12.0 V in ventricle) were significantly less than potentials measured in a unipolar configuration (tip‐can: mean 387.9 V in atrium, 394.0 V in ventricle; ring‐can: mean 405.6 V in atrium, 395.4 V in ventricle). Our compatibility tests demonstrate that use of this programmable‐polarity pacemaker in concert with an ICD system appears to be safe. Testing similar to the present study should be conducted prior to complete clinical acceptance of combined ICD and pacemaker implantation.
Implantable Defibrillation and Thromboembolic Events
Authors: BENEDINI GIUSEPPE , MARCHINI A. , CURNIS A. , BIANCHETTI F. , GARDINI A. , PINETTI P. , ZANELLI E.
Published: July 2006

In ICD patients thrombo‐embolic events (TEEs) are described as possible complications at implant or during the follow‐up. We report four cases of TEEs (two peripheral and two cerebral; 6.5% of patients) that occurred in our series during a mean follow‐up of 19.4 months. The patients had chronic postinfarction LV aneurysm (3) and idiopathic dilated cardiomyopathy (1). None had previous embolisms nor evidence of left atrial or LV clots at standard preoperative transthoracic echocardiography. No paroxysms of atrial fibrillation were documented prior or after ICD implant. We discuss the possible causes of embolization and the suitability of anticoagulant therapy in ICD patients.
Large Capacitor Defibrillation Waveform Reduces Peak Voltages Without Increasing Energies
Authors: HAHN STEPHEN J. , HEIL JOHN E. , LANG DOUGLAS J.
Published: July 2006

This study tested the hypothesis that increasing capacitance would allow a reduction in ICD size without reducing the deliverable energy. For example, the volume of a single 450 μF capacitor (390 V peak) is 1/3 less than that of two 250 μF capacitors (780 V), but it can store equivalent amounts of energy.Methods: Endocardial defibrillation electrodes (3.4 cm) were positioned in the RV apex and at the RA/ SVC junction in six mixed‐breed, isoflurane anesthetized pigs (41 ± 3 kg). Three 17‐cm ribbon wires were positioned subcutaneously on the left lateral chest (SQArray). Two CPI VENTAK ECDs were equipped to deliver 60/40 biphasic waveforms using either 125 μF (STD) or 500 μF (LD) of capacitance. A 15 shock up/down protocol was used to determine the 50% probability of success levels for each waveform in each animal. Shocks were delivered from RV(‐)→SVC + SQArray(+) in random order. Results were compared using paired Student'sf‐tests and are reported as mean ± SE. Results: The 500 μF long duration waveform reduced peak voltage 41% (374 ± 18 V [STD] vs 219 ± 14 V (LD], P < 0.001) and reduced peak current 38% (11.0 ± 1.1 A [STD] vs 6.8 ± 0.6 A [LD], P < 0.001) but did not significantly change the delivered energy(12.4 ± 1.3 J [STD] vs 13.4 ± 1.0 J [LD]). Durations increased from 10.0 ± 0.2 to 17.6 ± 0.5 msec (P < 0.001).Conclusions: Defibrillation with a 500 μF, long duration biphasic defibrillation waveform received similar amounts of energy but significantly reduced peak voltage and current compared to a waveform produced from 125 μF. A single large capacitor could be used to reduce the physical size of an ICD compared to the standard two capacitor system.
A Long Thin Electrode Is Equivalent to a Short Thick Electrode for Defibrillation in the Right Ventricle
Authors: LEONELLI FABIO M. , WRIGHT HART , LATTERELL SCOTT T. , NELSON RANDALL S. , ADAMS TED P. , KROLL MARK W.
Published: July 2006

We hypothesized that a long thin right ventricular (RV) electrode would have equivalent defibrillation threshold (DFT) performance to a short thick electrode with approximately the same surface area. This could lead to thinner transvenous lead systems, which would be easier to implant. A thin (5.1 French) lead was compared to a standard control (10.7 French). The thin lead had an 8‐cm RV electrode length with a surface area of 4.26 cm2. The standard lead had a RV electrode length of 3.7 cm and a surface area of 4.12 cm2. A 140‐μFrench capacitor 65%/65% tilt biphasic defibrillation shock was delivered between the RV electrode and a 14‐cm2 subcutaneous patch. DFTs were determined following 10 seconds of fibrillation in 11 dogs by a triple determination averaging technique. The thin lead had a lower resistance (77.1 ± 27.4 Ω vs 88.9 ± 30.3 Ω, P < 0.001) than did the thick lead. There was no significant difference in stored energy DFTs (9.9 ± 2.5 vs 10.3 ± 2.7, P = 0.098 2‐sided, P = 0.049 1‐sided). This was in spite of the fact that the long thin lead had a portion of its RV coil extending above the tricuspid valve and, thus, not contributing efficiently to the ventricular gradients in the small dog heart. We conclude that a long thin right ventricular electrode and a standard short thick electrode had equivalent defibrillation performance. This preliminary result should be confirmed in clinical studies as it could lead to significantly thinner transvenous lead systems.
Transseptal Defibrillation Is Superior for Transvenous Defibrillation
Authors: SINGER IGOR , GOLDSMITH JANE , MALDONADO CLAUDIO
Published: July 2006

The conventional electrode configuration of current internal defibrillation systems most commonly use superior vena caval (SVC) or combined SVC and subcutaneous (SC) electrodes as anode, and right ventricular apex (HVA) electrode as cathode. We have demonstrated earlier that the septal mass is important for defibrillation. The purpose of the present study was to compare a transseptal to a conventional electrode arrangement in the canine model. Three endocardial electrodes, 5 French EnGuard™ were positioned in RVA, SVC, and the right ventricular outflow (RVO) in eight dogs. A 5 French SC electrode was positioned in the fifth left intercostal space. RVA‐RVO‐/SC+ (configuration 2) was compared to SVC‐SC+/RVA‐(configuration 1). Defibrillation threshold testing was performed using asymmetrical biphasic shock, 6 msec+/2 msec‐. Probit fit was used to compare the results at 40%, 50%, 60%, and 90% probabilities, and the logistic regression analysis to estimate the impact of variables. Electrode configuration had the strongest predictive value. Configuration 2 was superior to configuration 1 (P = 0.0016). At any voltage settings the probability of success for configuration 2 was greater, and current less (P < 0.00005). The energy requirements were reduced by approximately 33% for configuration 2. There were no significant differences in impedance between the two configurations. We conclude that transseptal defibrillation is more effective because of the improved lead geometry and voltage gradient.
TiN: A Suitable Coating for Defibrillator Electrodes?
Authors: STROETMANN B. , SIEMSEN G. , STRAEHLER B.
Published: July 2006

The electrochemical behavior of porous TiN coating for defibrillator electrodes was investigated by in vitro studies. A commercially available Ti patch was compared with a Ti patch coated with a layer of porous TiN. Similarly, the influence of the TiN coating on a Pt/Ir intracardial electrode was tested. Porous TiN coatings were made by reactive sputtering on the plain electrodes. Electrode potential measurements were performed during monophasic anodic and cathodic defibrillator shocks delivering energies between 1 J and 49 J. Porous TiN coating of Pt/Ir coils was found suitable to deliver cathodal pulses, while a plain coil remains recommended for anodic shocks. TiN coating was of benefit for conventional Ti patches. Particularly, in the case of anodic shocks, the TiN layer protected the Ti‐mesh from immediate oxidation. However, above 70 anodic shocks of 49 J, the TiN coating underwent oxidation to an oxynitride. An estimated 180 anodic shocks of 10 J could be delivered before TiN oxidation became measurable by increased polarization.
Predictors of Defibrillation Energy Requirements with Nonepicardial Lead Systems
Authors: KOPP DOUGLAS E. , BLAKEMAN BRADFORD P. , KALL JOHN G. , OLSHANSKY BRIAN , KINDER CHARLES A. , WILBER DAVID J.
Published: July 2006

The determinants of high defibrillation energy requirements (DER) using nonepicardial lead systems (NELS) have not been well characterized. The goal of this study was to examine prospectively the influence of clinical, radiographic, echocardiographic, and procedural variables on DER during NELS placement. Data from 100 consecutive patients undergoing attempted NELS implantation were analyzed. Transve‐nous leads, subcutaneous patches, and monophasic shock devices from two manufacturers were used. Leads were successfully positioned for testing in 95% of patients. An adequate DER (≤ 25 J) was obtained in 73 of 95 (77%) of patients. Univariate analysis identified amiodarone therapy and left ventricular mass as predictors of high DER. With multivariate analysis, amiodarone therapy was the sole significant predictor of high DER (P = 0.002, odds ratio 5.46). The 22 patients with high NELS DER also had high epicardial DER (mean 24 ± 9 J). The two patch epicardial DER was > 25 joules in 12 of 22 patients. Thus, adequate DER with monophasic shock waveforms can be obtained in most patients undergoing NELS testing. However, amiodarone therapy significantly increases the probability of obtaining high DER.
Radioisotopic Pacemaker: Long‐Term Clinical Results
Authors: CHAUVEL CHRISTOPHE , LAVERGNE THOMAS , COHEN ARIEL , DUCIMETIÈRE PIERRE , YVES le HEUZEY JEAN , VALTY JEAN , GUIZE LOUIS
Published: July 2006

In order to prolong the service life of the generator, the isotopic pacemakers, powered by Pu238, have been developed and implanted since 1970. We report the follow‐up of 325 patients (mean age 39 ± 18 years) implanted with an isotopic pulse generator (Medtronic 9000/9090) between April 1970 and July 1982. The mean follow‐up was 12 years (range 6 days to 18.5 years). The generator was highly reliable; the mean value of pacing rate between implantation and last follow‐up decreased significantly but no more than 1 beat/min (72.7 vs 71.8 beats/ min; P < 0.001) and the pulse width did not change significantly. The actuarial survival of the device was 97% at 18.5 years. During the follow‐up period, 122 reoperations were performed in 85 patients: 88 explanations of the entire pacing system and 34 modifications of the lead system. Lead dysfunction accounted for 68% of the 122 reoperations, generator failure for 6%, and miscellaneous reasons for 26%. However, 72% of patients remain free of intervention during the follow‐up period and 61 patients (20%) died during this period. Most deaths (52%) were of nonsudden cardiovascular origin, 17% were related to cancer, and 13% to sudden death. After 5, 10, and 18.5 years, 94%, 89%, and 73% of the patients were alive, respectively. No side effect could be attributed to the radioisotope. We conclude that this isotopic pacemaker demonstrated its reliability for long‐term cardiac pacing.
Myocardial Temperature Response During Radiofrequency Catheter Ablation
Authors: WITTKAMPF FRED H.M. , SIMMERS TIMOTHY A. , HAUER RICHARD N.W. , ROBLES de MEDINA ETIENNE O.
Published: July 2006

During radiofrequency catheter ablation, steady‐state electrode‐tissue interface temperatures are reached within 5 seconds. Within the myocardium, however, a much slower temperature rise has been observed in vitro with stabilization after approximately 2 minutes. This discrepancy suggests that tissue temperature rise time depends on distance from the ablation electrode and, thus, that temperature rise measured at the electrode‐tissue interface does not correspond with temperature rise within the myocardium. In five beagles, closed‐chest radiofrequency catheter ablation was performed in the vicinity of intramural thermocouples. Sequences of 60 seconds, 10‐ and 25‐watt pulses were delivered in the unipolar mode via the 4‐mm distal electrode of a 7 French steerable catheter. At all distances > 3 mm from the ablation electrode, the rate of myocardial temperature rise was low: relative rise after 5, 10, 20, and 30 seconds was 22%, 32%, 48%, and 63% of that achieved at 60 seconds, and even then steady‐state temperatures had not yet been reached. Temperature rise was faster at sites closer to the ablation electrode. There was no difference in rate of rise between first and second pulses at the same site. A 6% higher myocardial temperature was reached with a second identical pulse at the same site. Tissue temperatures achieved with 25 watts were 2.4 times higher than with a preceding 10‐watt pulse at the same ablation site.
Programming of the Pacing Impulse in Pacemakers Connected to Steroid Lead Systems
Authors: SCHUCHERT ANDREAS , CAPPATO RICCARDO , KUCK KARL‐HEINZ , MEINERTZ THOMAS
Published: July 2006

The purpose of the study was to compare the feasibility of low amplitude output programming (2.5 V/0.5 msec) 3 or more months after pacemaker implantation in patients receiving steroid and nonsteroid lead systems. Chronic pacing voltage, current, and energy thresholds were determined from 0.05‐ to 1.0‐msec pulse duration in 44 patients with steroid lead systems, and in 36 patients with nonsteroid lead systems; all patients received pacemakers from the same manufacturer, which utilized the same programming and telemetry features. Chronaxie, pulse duration at the lowest pacing current, and energy were assessed from individual threshold curves. Steroid‐eluting leads had significantly lower pacing voltage, current, and energy thresholds than nonsteroid leads. A 100% safety threshold margin could be achieved in 43 (98%) patients with steroid lead systems and in 27 (75%;P < 0.05) patients with nonsteroid lead systems with output programming of 2.5 V/0.5 msec. Chronaxie (0.22 ± 0.17 msec vs 0.44 ± 0.31 msec; P < 0.05), pulse duration at lowest pacing current (0.28 ± 0.12 msec vs 0.49 ± 0.22 msec; P < 0.05), and pulse duration at lowest pacing energy (0.31 ± 0.17 msec vs 0.53 ± 0.22 msec; P < 0.05) were significantly shorter for steroid than for nonsteroid lead systems. In 42 patients of the former group, a 100% safety margin could be maintained either with a 2.5 V/0.3 msec or with a 1.6 V/0.5 msec output. Conclusions Low amplitude output programming can be obtained in almost all pacemakers connected to steroid‐eluting lead systems, and in a significantly higher number of patients than when connected with nonsteroid leads systems. Moreover, in most cases, a 100% safety margin can be achieved at settings as low as 1.6 V/0.5 msec or 2.5 V/0.3 msec; these different combinations offer potential different opportunies to select definitive programming and reduce pacing current requirements in patients undergoing pacemaker implantation.
Cellular Electrophysiological Changes Induced In Vitro by Radiofrequency Current: Comparison with Electrical Ablation
Authors: GE YU‐ZHI , SHAO PEI‐ZHEN , GOLDBERGER JEFFREY , KADISH ALAN
Published: July 2006

The purpose of this study was to examine the cellular electrophysiological effects of radiofrequency energy delivery in an in vitro canine epicardial preparation and compare the effects to those of high energy electrical ablation in a similar preparation. Ten joules of direct current energy or 40 volts of radiofrequency energy were delivered by a 6 French 2‐mm tip catheter to the epicardial surface of 2 × 3 cm epicardial strips superfused with Tyrode's solution. Direct current energy delivery produced a crater and central zone of necrosis surrounded by a border zone of viable but damaged tissue that extended up to 10–12 mm from the site of energy delivery. Cellular electrophysiological abnormalities that included a less negative resting membrane potential, decreased peak dV/dT, decreased action potential amplitude, and decreased action potential duration (APD) were approximately linearly related to the distance from the crater edge. In addition, viable and inexcitable cells were frequently interspersed. Between 2 and 5 mm from the crater edge, 36.4% of the cells were inexcitable whereas others displayed normal action potential characteristics. In contrast, radiofrequency current produced a central zone of necrosis surrounded by a smaller border zone. Cellular damage that was qualitatively similar to that produced by direct current energy extended only up to 6–8 mm from the edge of the crater. In addition, severe abnormalities were noted in intracellular potentials recorded within 2 mm of the ablation site, and only minor abnormalities further away. Lesions were relatively homogeneous. Between 2 and 5 mm from the ablation site only 2.6% of the cells were inexcitable (P < 0.05 vs direct current). In conclusion, radiofrequency current produces lesions that are smaller and more homogeneous than those produced by direct current ablation. Although the border zone is small, a region of partially depolarized but viable myocardium is present after radiofrequency current energy delivery. These findings provide a cellular basis for several clinical observations that have been made following radiofrequency current energy delivery.
Evaluation of a New Rate Adaptive Ventricular Pacemaker Controlled by Double Sensors
Authors: OVSYSHCHER ILYA , GULDAL MUHAREM , KARAOGUZ REMZI , KATZ AMOS , BONDY CHAVA
Published: July 2006

The LEGEND‐PLUS, a new rate adaptive pacemaker that combines activity and minute ventilation sensing for automatic rate adaptation was implanted in the right ventricle (VVIR) in 11 patients (mean age 62 ± 9 years). Initial programming was performed using the Programmer Exercise Protocol (a 3‐minute walk). This programming was evaluated by treadmill tests, up‐stairs and down‐stairs walking, and Holier recordings. Results: Following the final programming of LEGEND‐PLUS, the mean upper activity rate was 102 ± 7 beats/rain (range 90–120 beats/min), while the mean upper minute ventilation rate was 125 ± 16 beats/min (range 100–150 beats/min). The mean rate responses during the exercise protocol and the final programming in minute ventilation and activity sensing modes were 5.4 ± 2.3 (range 1–9), versus 4 ± 2.4 (range 1–8; P < 0.01) and 7.6 ±1.1 (range 5–9), versus 7.5 ± 0.8 (range 6–9; P = 0.8), respectively. In the combined sensing mode, the acceleration rate was identical to the activity rate response and the deceleration rate mimicked the minute ventilation. Conclusion: Dual sensor VVIR pacemakers have the potential to improve rate adaptation to exercise. The rate response to exercise in patients fitted with activity and minute ventilation sensors, VVIR pacemakers closely mimics the physiological rate response.
Cardiac Pacing in Fetal Lambs: Intrauterine Transvenous Cardiac Pacing for Fetal Complete Heart Block
Authors: KIKUCHI YUTAKA , SHIRAISHI HIROHIKO , IGARASHI HIROSHI , CHUNFENG LIU , YANAGISAWA MASAYOSHI
Published: July 2006

To evaluate the feasibility of intrauterine transvenous cardiac pacing, the right ventricular output was measured during pacing in six fetal lambs. Under maternal anesthesia, the uterus was opened, and, under local anesthesia, the pacing lead (Medtronic Capsure SP4023) was inserted via the fetal left internal jugular vein. Right ventricular output was estimated using an Aloka SSD‐730 ultrasound device, and tricuspid valve regurgitation was evaluated with an Aloka SSD‐880 using the transuterine approach. The ultrasonic right ventricular cardiac output was measured under three different conditions: (1) with the tip of the pacing lead in the superior vena cava (control); (2) with the tip of the pacing lead in the right ventricle; and (3) with pacing at 200 beats/min. The right ventricular output decreased when the pacing lead was inserted into the right ventricle, as well as during pacing at 200 beats/min ([1] = 107 ± 13.2 ml/kg per min; [2] = 73.8 ± 17. 5 ml/kg per min; and [3] = 78.3 ± 23.6 ml/kg per min), Tricuspid regurgitation did not change under any of the conditions tested. Intrauterine transvenous cardiac pacing was successfully achieved. Insertion of the pacing lead into the right ventricle decreased the ventricular output without increasing tricuspid valve regurgitation.
Use of Adenosine to Identify Patients at Risk for Recurrence of Accessory Pathway Conduction After Initially Successful Radiofrequency Catheter Ablation
Authors: WALKER KIRK W. , SILKA MICHAEL J. , HAUPT DAN , KRON JACK , McANULTY JOHN H. , HALPERIN BLAIR D.
Published: July 2006

Objectives: The use of adenosine after radiofrequency catheter ablation of accessory pathways was prospectively studied to determine its utility for identifying patients at risk for recurrence of accessory pathway conduction and to guide therapy that might reduce late recurrence in this group. Background: Accessory pathway conduction recursin 5%–12% of patients following initially “successful” radiofrequency catheter ablation. Adenosine may facilitate conduction over accessory pathways that have been modified by radiofrequency delivery, thus identifying patients at risk for recurrence. Methods: Radiofrequency catheter ablation was performed in 109 patients. Prior to ablation, 12–18 mg of adenosine was administered. After ablation, when all evidence of accessory pathway conduction remained absent for at least 30 minutes, adenosine 12–18 mg was again administered. Results: Adenosine given prior to radiofrequency catheter ablation did not block accessory pathway conduction in any patient. Adenosine given after elimination of accessory pathway conduction induced complete atrioventricular and ventriculoatrial block in 95 patients; 11 (11.6%) subsequently had recurrence of accessory pathway function. Accessory pathway conduction was unmasked by adenosine in 12 patients (11.2%). After further deliveries of radiofrequency energy, 7 of these 12 patients subsequently demonstrated adenosine induced atrioventricular and ventriculoatrial block; 1 of these 7 patients experienced recurrence of accessory pathway conduction. The remaining 5 patients demonstrated persistent accessory pathway conduction only with adenosine; all experienced clinical recurrence of accessory pathway function. Conclusion: The use of adenosine after presumed successful radiofrequency catheter ablation may reveal persistent accessory pathway conduction. Elimination of this latent accessory pathway conduction reduces the risk for recurrence.
Relationship Between Interatrial Conduction Times and Left Atrial Dimension in Patients Undergoing Atrioventricular Stimulation
Authors: RAYBAUD FLORENCE , CAMOUS JEAN PIERRE , BENOIT PHILIPPE , DOLISI CLAUDE , BAUDOUY MARCEL
Published: July 2006

Interatrial conduction time (IACT) and left atrial dimension (LAD) were determined in 75 patients (41 males, 34 females, mean age 78.2 ± 7,9 years) undergoing atrioventricular (AV) stimulation. The LAD was measured by M mode echocardiography as the distance between the posterior aortic wall and the posterior left atrial wall. The IACT was determined during a transvenous dual chamber pacemaker implant done under local anesthesia (lidocaine). The spontaneous interatrial conduction time (SIACT) was measured from the intrinsic deflection (ID) of the right atrium recorded in a unipolar mode (unipolar J‐shaped had positioned in the right appendage) to the ID of the left atrium (bipolar esophageal lead, left atrial positive deflection equal to the negative one) during sinus rhythm. The right atrium then was paced at a rate slightly greater than the spontaneous one. The paced interatrial conduction time (PIACT) was measured from the stimulus artifact to the left atrial ID. The PIACT was also measured during incremental right atrial pacing (10 beats/min step increase to 180 beats/min) and, from these measurements, the maximum increase of PIACT (MIPIACT) was deduced. The LAD was measured at 39.5 ± 8.7 mm, SIACT at 70.3 ± 24.8 msec, PIACT at 118.8 ± 27.9 msec, and MIPIACT at 16.5 ± 16.4 msec. We found highly significant relationships between SIACT and LAD(P = 0.0006, r ‐ 0.39), PIACT and LAD (P = 0.0001, r = 0.45), and MIPIACT and LAD (P = 0.0006, r = 0.38). We also noted that the LAD was greater in patients in whom MIPIACT was >10 msec than in patients in whom the MIPIACT was negligible (P < 0.002). However, the “r” values indicate that IACT is probably determined by multiple factors, and LAD appears to be one of the most important. Thus, we demonstrated the existence of highly significant relationships between the LAD determined by M mode echocardiography and the IACT when sensing and pacing the right atrium. We also demonstrated that the LAD was greater in patients in whom PIACT increased by an appreciable duration during fast atrial pacing. These results must be kept in mind when choosing a mode of stimulation and determining the AV delay (dual chamber pacemaker), particularly in patients with left atrial enlargement in whom the contribution of the atrial contraction and its timing are hemodynamically determinant.
Sotalol: From “Just Another Beta Blocker” to “The Prototype of Class III Antidysrhythmic Compound”
Authors: CLAUDEL JEAN PHILIPPE , TOUBOUL PAUL
Published: July 2006

Sotalol is a beta‐blocking drug devoid of membrane stabilizing properties, as well as intrinsic sympathomimetic actions, or cardioselectivity. In addition, sotalol prolongs atrial and ventricular repolarization (Class III antiarrhythmic activity). It appears to have less myocardial depressant effect than other beta‐blocking agents. Given orally, bioavailability of the drug reaches 100%. Sotalol's plasma half‐life is 15 hours (range 7–18) and is dependent only on renal function. In clinical practice, it has been found effective in the suppression of nearly all supraventricular and ventricular dysrrhythmias except those related to prolonged ventricular repolarization. Most common adverse effects are dyspnea, bradycardia, and fatigue, which results in drug termination in 16% of the cases. Torsades de pointes usually associated with bradycardia and drug induced QTc prolongation has been reported in 1.9%–3.5% of the patients receiving sotalol. This complication may be reduced by limiting the dose (< 640 mg/day) especially in patients with impaired renal function. In addition hypokalemia must be avoided. To sum up, the combination of Class II and Class III effects may carry additional benefits. However, further studies are required to test such hypotheses.