bluuebunny/crossref_metadata_2025 huggingface dataset:
Early Postoperative Increase in Defibrillation Threshold with Nonthoracotomy System in Humans
Authors: HSIA HENRY H. , MITRA RAMAN L. , FLORES BELINDA T. , MARCHLINSKI FRANCIS E.
Published: July 2006

The stability of the defibrillation threshold (DFT) early after implantation of an implantable cardioverter defibrillator was evaluated in 15 patients. All but one patient had a three lead nonthoracotomy system using a subcutaneous patch, a right ventricular endocardial lead, and a lead in coronary sinus (n = 5) or superior vena cava (n = 9). Shocks were delivered using simultaneous in nine, sequential in three, and single pathway (coronary sinus not used) in one patient. DFTs were measured at implant (n = 15), 2–8 days postoperation (postop, n = 15), and 4–6 weeks later (n = 8). The DFT was defined as the lowest energy shock that resulted in successful defibrillation. The DFT was assessed with output beginning at 18 joules or 2–4 joules above the implant DFT. All shocks were delivered in 2‐ to 4‐joule increments or decrements. DFTs were significantly higher postoperatively than DFTs at implant (22.7 ± 7.0 J vs 16.9 ± 3.9 J; P < 0.05), Eight of 15 patients had DFT determined at all three study periods. In these patients, DFT increased at postop (22.8 ± 8.3 J vs 16.4 ± 3.9 J at implant: P < 0.05) and returned to baseline at 4–6 weeks (16 ± 7.1) vs 16.4 ± 3.9 J at implant; P = N.S.). Thus, in patients with a multilead nonthoracotomy system, a DFT rise was observed early after implant. The DFT appears to return to baseline in 4–6 weeks. These results have important implications for programming energy output after implantable cardioverter defibrillator implantation.
A Report Using a Hybrid ICD System: The Need for Compatibility Among Implanted Defibrillator Components
Authors: NEWMAN D. , DORIAN P. , YAO J. , HART J. , HARDY J.
Published: July 2006

The successful implantation of an ICD system with hardware from three different manufacturers is described. This case exemplifies the need for compatibility of components among different manufacturers. This is most relevant at a time when rapidly changing technology and hardware availability may require a mixing, by informed practitioners, of ICD system components. The parallel to the development of the uniform IS‐1 standard for bradycardia devices is made.
Stability of the DDD Pacing Mode in Patients 80 Years of Age and Older
Authors: RAY SIMON G. , CONNELLY DEREK T. , HUGHES MARK , BELLAMY CHRISTOPHER M. , CHARLES RICHARD G.
Published: July 2006

We reviewed the records of 119 consecutive patients aged 80 years or older (mean age 84 ± 3.7 years) in whom a dual chamber pacemaker was implanted between 1984 and 1991. Follow‐up data was available up to February 1993. Immediate postimplantation complications were rare. Nine patients were lost to follow‐up, all within 6 months of implantation. An additional seven patients died within 6 months of implantation. Long‐term follow up for at least 6 months from implantation was available for 103 of the 119 patients (87%). Of these 89 (66%) remained in functioning DDD mode for a mean of 22 ± 15 months from implantation. Nine patients were reprogrammed to VVI mode, six due to atrial fibrillation and three due to failure of atrial sensing or pacing. One patient was programmed DVI for failure of atrial sensing; 94 of 112 patients (84%) whose status was definitely known in February 1993 remained in functioning DDD mode until death or last follow‐up. Cumulative survival in DDD mode was 78% at 30 months. We conclude that DDD pacing is stable in the great majority of patients in their nineth and tenth decades who present with rhythms amenable to dual chamber pacing and who have no history of sustained atrial fibrillation.
Comparison of Simultaneous Versus Sequential Defibrillation Pulsing Techniques Using a Nonthoracotomy System
Authors: HSIA HENRY H. , KLEIMAN ROBERT B. , FLORES BELINDA T. , MARCHLINSKI FRANCIS E.
Published: July 2006

The defibrillation threshold (DFT) using simultaneous (SIML) versus sequential (SEQ) pathways for shock delivery was compared in 16 patients with an implanted cardioverter defibrillator. All patients had three‐lead nonthoracotomy systems (NTL) using a left chest subcutaneous patch, a right ventricular endocardial lead, and a lead in the coronary sinus (n = 5) or superior vena cava (n = 11). The DFT were determined 2–44 days (17 ± 17 days) after implantation. The DFT was defined as the lowest energy shock that resulted in successful defibrillation. The first pathway tested was SIML in 12 and SEQ in 4 patients with output beginning at or above the intraoperative DFT, routinely 18 J. The second pathway was tested beginning 2–4 J above the DFT of the first tested pathway. All shocks were delivered in 2–4 J decrement or increment steps. The SEQ pathway shocks resulted in a significantly lower DFT than SIML pathway shocks (14 ± 6 vs 18 ± 6 J; I < 0.01). There was no difference in the time delay after ventricular fibrillation initiation before shock delivery for the successful defibrillation between SIML versus SEQ pathways (7 ± 2 secs for both pathways). In 7 of 16 patients, defibrillation using SEQ pathway resulted in a > 5 J lowering of DFT, while only one patient had > 5 J lowering of DFT using SIML shocks (P <0.05). These results have important implications for selecting the optimal pathway for implantable cardioverter defibrillator therapy with a multilead NTL system.
The Role of Implantable Cardioverter Defibrillators in Non VT/VF Sudden Deaths
Authors: THAKUR RANJAN K. , AUFDERHEIDE THOMAS P. , TRESCH DONALD D. , GHANI MANSURA
Published: July 2006

Implantable cardioverter defibrillator (ICD) therapy has been an impressive success in preventing sudden cardiac death (SCD). Electrocardiographic documentation of SCD in ICD patients has been rare, but usually arrhythmias other than ventricular tachycardia/ventricular fibrillation (VT/VF; asystole and electromechanical dissociation [EMD]) have been implicated. This raises the question whether backup bradycardia pacing can prevent deaths due to asystole and EMD in such patients. We studied the outcome of 88 patients with permanent bradycardia pacemakers and compared them to 500 consecutive nonpacemaker patient controls, sustaining out‐of‐hospital cardiac arrest and undergoing resuscitation by paramedics. Mean age of the pacemaker patients was 73.5 ± 10.3 years and 64% males, compared to mean age of 68.2 ± 6.7 years and 67% males in the control group. Overall success of resuscitation and survival rates were similar. When the documented rhythm was VT/VF or asystole there were no differences in resuscitation or survival rates for the pacemaker or nonpacemaker patients. However, resuscitation rate was significantly higher in pacemaker patients than nonpacemaker patients with EMD: 47% versus 20% (P < 0.03). For EMD, survival rate for the pacemaker patients was 13% compared to 5% in the nonpacemaker patients, but this difference was not statistically significant. Backup bradycardia pacing in future generation devices may improve the outcome of non VT/VF sudden cardiac death in at least some of the ICD recipients.
Pseudo‐Oversensing of the T Wave by an Implantable Cardioverter Defibrillator: A Nonclinical Problem
Authors: FRAZIER DAVID W. , STANTON MARSHALL S.
Published: July 2006

Two patients are described who had pseudo‐oversensing of T waves during follow‐up testing of the Medtronic PCD. Each patient exhibited appropriate T wave sensing following closely coupled spontaneous QRS complexes to subthreshold stimuli without having T wave sensing following sensed or paced complexes. One patient also revealed T wave sensing following fusion beats. The occurrence of T wave sensing in these unique clinical situations was due to the auto‐adjusting sensitivity threshold function used by the PCD. Recognition of this normal sensing function will prevent inappropriate reprogramming of the sensitivity or postpace refractory period, interventions that could potentially lead to ventricular tachyarrhythmia undersensing.
Troubleshooting Implantable Cardioverter Defibrillator System Malfunctions: The Role of Impedance Measurements
Authors: HADDAD LUIGI , PADULA LUIS E. , MOREAU MARC , SCHOENFELD MARK H.
Published: July 2006

High impedance measurements may be used to troubleshoot ICD system malfunction. In four different cases a defective system was identified or confirmed by an abnormal impedance: two secondary to lead fractures, one to an adapter faulty connection, and one to a hose set‐screw connection. This led to further diagnostic procedures that ultimately localized the difficulty. Though the problems with ICD may be of diverse origins, routine use of impedance measurement for the troubleshooting of these systems may serve as an early sign of malfunction and would point the need for further investigation.
Effectiveness of Noninvasive Programmed Stimulation for Initiating Ventricular Tachyarrhythmias in Patients with Third‐Generation Implantable Cardioverter Definrillators
Authors: KLEIMAN ROBERT B. , CALLANS DAVID J. , HOOK BRUCE G. , MARCHLINSKI FRANCIS E.
Published: July 2006

Previous generations of implantable cardioverter defibrillators (ICDs) required invasive electrophysiological testing to assess defibrillator function. Newer third‐generation ICDs include the capability for performing noninvasive programmed stimulation (NIPS) and may reduce the need for invasive studies to assess tachycardia recognition and antitachycardia therapy algorithms. The effectiveness of ICD‐based NIPS for the induction of ventricular arrhythmias has not, however, been formally assessed. Third‐generation ICDs were implanted in 79 patients, who underwent a total of 166 postoperative defibrillator tests. NIPS with rapid ventricular pacing was performed in all patients in an attempt to induce ventricular fibrillation. In patients with prior sustained uniform ventricular tachycardia, programmed stimulation with up to three extrastimuli was performed in order to attempt to initiate the clinical ventricular tachcardia. Ventricular fibrillation was induced with NIPS in 146 of 166 studies (88%). Ventricular tachycardia was initiated with NIPS in 104 of 123 studies (85%). The type of defibrillator and the use of endocardial or epicardial rate sensing/ pacing leads did not influence the efficacy of NIPS. NIPS with third‐generation ICDs is generally effective at inducing ventricular fibrillation and clinically relevant ventricular tachycardias, and reduces the need to perform invasive electrophysiological testing following device implantation. In a minority of patients temporary transvenous pacing catheters must still be used to facilitate arrhythmia induction.
Clinical Surveillance of an Active Fixation, Bipolar, Polyurethane Insulated Pacing Lead, Part II: The Ventricular Lead
Authors: GLIKSON MICHAEL , VON FELDT LINDA K. , SUMAN VERA J. , HAYES DAVID L.
Published: July 2006

Since 1989, 72 Telectronics 330–201 active fixation, polyurethane insulated ventricular leads (Accufix) have been implanted at the Mayo Clinic. There were four (5.6%) acute lead related complications (perforation, microdislodgment, and macrodislodgment), three of which led to early reoperation. Over a follow‐up time of up to 2.7 years (median 9.4 months), there were six (8.3%) chronic lead related complications but no failures of lead material. Most of these complications developed during the first month, and half of them were transient, with documented improvement later. Two patients (2.6%) required reoperation for chronic complications. At follow‐up examination of the pacing thresholds, usually performed about 3 months after implantation, 14.3% of the examined patients had high pacing thresholds necessitating high‐output programming. The mechanisms and later evolution of this phenomenon should be further evaluated.
The Value of Rate Regularity and Multiplicity Measures to Detect Ventricular Tachycardia in the Presence of Atrial Fibrillation or Flutter
Authors: CHIANG CHIH‐MING JAMES , JENKINS JANICE M. , DiCARLO LORENZO A.
Published: July 2006

The predominant cause of inappropriate therapy by implantable antitachycardia devices with pacing and nonpacing cardioverter defibrillators, is mistaking a fast ventricular response during atrial fibrillation or flutter with true ventricular tachycardia (VT). The distinction between these arrhythmias is an important consideration in addressing the problem of reducing false‐positives in detection mechanisms for implantable devices. Dual chamber analysis that examines atrial and ventricular event ratios has been proposed as a solution to this problem, but would still fail in distinguishing paroxysmal VT requiring treatment from a fast but otherwise benign ventricular response during atrial fibrillation or flutter. In this study, two methods for discriminating these tachyarrhythmias were evaluated. Method 1 examined ventricular rate and rate regularity as a method for VT detection. Method 2 combined rate and regularity as well as an additional multiplicity criterion for recognition of atrial flutter with a fast ventricular response. In 20 patients. Method 1 had 100% sensitivity of VT detection and 80% specificity for detection of atrial fibrillation or flutter. Method 2 had 90% sensitivity and 90% specificity. These results suggest that use of these algorithms in future implantable devices would result in a decrease in false‐positive device therapies.
Flecainide Induced Atrial Tachycardia with 1:1 Ventricular Conduction During Exercise Testing
Authors: RANDAZZO DOMENICK N. , SCHWEITZER PAUL , STEIN ELLIOT , BANAS JOHN S. , WINTERS STEPHEN L.
Published: July 2006

Wide complex tachycardias may represent a rare proarrhythmic effect of some antiarrhythmic agents. The authors describe a patient who developed a wide complex tachycardia developing during stress testing while on therapy with flecainide, and the difficulty in interpreting the electrocardiogram. This article reviews potential proarrhythmic effects of flecainide in the treatment of atrial dysrhythmias and the difficulty in differentiating associated wide complex tachycardias.
Undersensing During Ventricular Tachyarrhythmias in a Third‐Generation Implantable Cardioverter Defibrillator: Diagnosis Using Stored Electrograms and Correction with Programming
Authors: MANN DAVID E. , KELLY PATRICIA A. , DAMLE ROGER S. , REITER MICHAEL J.
Published: July 2006

Third‐generation implantable cardioverter defibrillators with stored electrograms allow diagnosis of various sensing problems that may lead to an inappropriate device response. Undersensing of ventricular tachyarrhythmias is a potentially serious problem, as it may lead to failure to deliver therapy. To determine the incidence of this problem, we reviewed 98 patients with Ventritex Cadence defibrillator systems and found 2 patients in whom defibrillation therapy was delayed or aborted because of undersensing during induced ventricular tachyarrhythmias. In both cases, examination of stored electrograms revealed variation in electrogram amplitude, which presumably resulted in failure of the autogain feature to increase its sensitivity enough to count each complex. During charging, criteria for redetection of sinus rhythm were met because of this undercounting, leading to failure to deliver defibrillation therapy. This problem was detected in both patients 4–6 weeks following device implant during device testing, and both patients had been started on antiarrhythmic drug therapy prior to this testing. Programming the sinus redetection parameter from nominal to slow, increasing the number of beats necessary to confirm resumption of sinus rhythm, corrected the problem in both patients. Device testing in the electrophysiology laboratory, routinely postoperatively and following initiation of antiarrhythmic drug therapy, and the ability to retrieve stored electrograms are useful in detecting such sensing anomalies
Cardiac Involvement by Non‐Hodgkin's Lymphoma: An Unusual Presentation of Heart Conduction Disturbances
Authors: GIRO ANTONIO , VINCENTI ANTONIO , BOZZANO ALESSANDRO , TROCINO GIUSEPPE , VALAGUSSA FRANCO
Published: July 2006

A 57‐year‐old man with non‐Hodgkin's lymphoma presented with solitary sinus node dysfunction. Superior vena cava syndrome and progressive disturbance of the conduction system requiring dual chamber pacemaker implantation later appeared. Combination chemotherapy and radiation reversed abnormal sinus node function and the AV conduction disturbance, as demonstrated during electrophysiological evaluation.
Lead Dislodgment of a Permanent Pacemaker Due to Removal of a Temporary Pacing Electrode
Authors: JAEGER HORST J. , MATHIAS KLAUS , NEISE MICHAEL , KRABB HANS‐JURGEN
Published: July 2006

A 63‐year‐old male received a transvenous temporary pacemaker for bradyarrhythmia following mitral valve replacement and tricuspid valve annuloplasty. A transvenous permanent pacemaker was implanted the following day due to persistence of the bradyarrythmia and pacemaker dependency of the patient. Later the same day during removal of the temporary pacing electrode the permanent pacing lead was dislodged and had to be operatively repositioned. To avoid this complication, the position of pacemaker leads should be checked postoperatively with a frontal and lateral chest radiograph, and fluoroscopy should be used during removal of a temporary lead.
Sinus Node Modification Using Radiofrequency Current in a Patient with Persistent Inappropriate Sinus Tachycardia
Authors: WASPE LAWRENCE E. , CHIEN WALTER W. , MERILLAT JOHN C. , STARK STEPHEN I.
Published: July 2006

Radiofrequency catheter modification of the sinus node for persistent inappropriate sinus tachycardia has not been previously reported. This article describes a patient in whom radiofrequency current was used to ablate an incessant automatic tachycardia focus mapped to the region of the sinus node, where a discrete multicomponent electrogram demonstrating earliest atrial activation was recorded. A transient junctional rhythm developed immediately after ablation, with rapid subsequent emergence of a stable rhythm having normal sinus nodal characteristics.
Atrial Rate Adaptive Pacing: What Happens to AV Conduction?
Authors: LINDE CECILIA , NORDLANDER ROLF , ROSENQVIST MÅRTEN
Published: July 2006

To investigate if an nonphysiological prolongation of the AV inteii‐al is common during activity sensor modulated atrial rate adaptive (AAIR) pacing, 21 patients witb sinus node disease treated with fixed rate atrial (AAI) or AAIR pacemakers were examined. Spike‐Q intervals were compared at different beaii: rates obtained by overdrive pacing at rest and during exercise (Study I), measured during exercise at unresponsive (AAI), optimal (AAIR) and over responsive programming (AAIR +) of the activity sensor (Study II), and finally examined by 24‐hour Holter recording in AAI and AAIR pacing modes (Study III). Study I: The spike‐Q interval increased significantly with increasing heart rate at rest, but not during exercise. At rest the spike‐Q interval was significantly higher at all heart rates compared to exercise. There was a significant positive correlation between the maximal spike‐Q interval at rest and the maximal spike‐Q inteival during exercise (r = 0.63). Study II: The spike‐Q interval was shortest in the AAI and longest in the AAIR+ mode in all patients. Study III: During AAI or AAIR pacing the spike‐Q interval was longest at night and shortest in the morning. The mean spike‐Q interval was longer in AAIB than in AAI pacing. No statistical difference between the maximal spike‐Q intervals observed during the two modes was, however, found. Variations in spike‐Q interval are generally caused by changes in autonomic tone or medication with drugs with antiarrhythmic effect. Our results indicate that the risk for an nonphysiological prolongation of the AV interval during AAIR pacing is rather small and can be predicted by studying the spike‐Q interval at rest during overdrive pacing.
Power and Temperature Guided Radiofrequency Catheter Ablation of the Right Atrium in Pigs
Authors: KONGSGAARD ERIK , FOERSTER ARNOLD , AASS HALFDAN , MADSEN STEINAR , AMLIE JAN P.
Published: July 2006

The aim of the present study was twofold: to assess the safety of ablating the atrial free wall using RF current; and to assess the effect of a single dose of intravenous beparin foUowed by aspirin once daily to prevent tbrombas formation after RF ablation. Temperature and power guided catheter ablation were evaluated. Twenty pigs were randomized to power or temperature guided unipolar RF catheter ablation. Ten animals received a bolus of beparin (150 U/kg) followed by 150‐mg aspirin daily. and ten served as controls. A mid‐sternal tboracotomy was performed 5–7 days later. the ability of a lesion to resist an increased transmural atrial pressure was examined by inflating a cuff around the palmonal artery. Transmurai lesions were found in all animals. Rigbt atrial pressure was increased from 5 to 30 mmHg witb no sign of perforation. In 11 of 20 (55%) animals, 1–3 lesions were foand in the lungs (diameter 4–18 mm). the localization of these lesions corresponded to the lesions in the atria. there were no differences in the energy delivery modes witb regard to the number of animals witb lung lesions. Lesions witb thrombus formation were found in four animals in the heparin/aspirin group and in nine animals in the control group. The incidence of thrombi was significantly smaller in the treatment group. there were no differences between temperature and power guided catheter ablation witb regard to the size of the atrial lesions or to the incidence of tbrombus formation. Transmural lesions induced in the rigbt atrium by RF energy are resistant to increases in transmural pressure. However, lung tissue overlying the ablated target may be injured by the RF energy delivered. The combination of a single dose intravenous beparin followed by aspirin daily may reduce the incidence of tbrombus formation.
Regeneration of Pacemaker Battery After Explantation
Authors: DAS GOPAL
Published: July 2006

In an effort to evaluate changes in voltage output of a pulse generator after explantation, the output of 33 pulse generators was measured at the time ofexplant and following 3 days of rest (not pacing). Twenty generators were removed secondary to elective replacement indicators (ERI) and 13 for other causes. The output of ERI generators significantly increased, from 2.62 volts at explant, to 3.17 volts, 3 days later. The non‐ERI generators on the other hand, showed no significant change in their output. These observations are important when dealing with battery depletion.
Carotid Sinus Hypersensitivity and Syndrome in Patients with Chronic Atrial Fibrillation
Authors: CICOGNA RAOUL , MASCIOLI GIOSUÈ , BONOMI FELICE GIULIO , KIEVAL ROBERT S. , BERNABO MARGO GATTINI , TURELLI ANNALISA , VISIOLI ODOARDO
Published: July 2006

Carotid sinus hypersensitivity (CSH) has been studied in subjects in sinus rhythm, but it has never been studied in patients with chronic atrial fibrillation (AF). After a finding of CSH in a patient with chronic AF and syncope, we studied the effects of carotid sinus stimulation in a group of patients with AF. Ten patients with chronic AF and normal ventricular rates who complained of dizziness or loss of consciousness underwent right and left carotid sinus massage (CSM) during ECG monitoring. A control group of ten patients with AF but without neurological symptoms was likewise investigated. CSH was present in eight symptomatic patients (5 patients presented right CSH, 1 left and 2 bilateral CSH), but only in three of the control patients. The mean duration of asystole induced by right CSM was 5.94 ± 2.10 seconds; the mean asystolic interval induced by left CSM lasted 8.58 ± 1.42 seconds. Six patients in the symptomatic group had a recurrence of spontaneous symptomatology during CSM, so that a diagnosis of carotid sinus syndrome was established. All symptomatic patients (8 patients with CSH, 2 patients with ventricular standstills but without CSH) received a permanent ventricular pacemaker. Following pacing, all patients, except for one with a significant drop of systolic blood pressure during CSM. became completely asymptomatic. In elder patients with chronic AF, CSH can induce prolonged ventricular asystole, which may be responsible for neurological symptoms such as dizziness, presyncope, or syncope, as observed in patients in sinus rhythm with carotid sinus syndrome. Abnormal sensitivity of the carotid sinus could, therefore, be one of the causes of increased morbidity and mortality in patients with chronic AF. Permanent ventricular pacing may help reduce these complications.
Optical Recordings of Ventricular Excitability of Frog Heart by an Extracellular Stimulating Point Electrode
Authors: NEUNLIST MICHEL , TUNG LESLIE
Published: July 2006

To enhance understanding of the excitability of cardiac wusde during rest, an optical technique using the fluorescent voltage sensitive dye di‐4‐ANEPPS was used. Unlike conventional electrical recordings, optical recordings are free from electrical artifacts and. therefore, allow the observation of the transmembrane potential not only following the stimulation pulse, but also during the pulse itself Transmembrane potentials (V̄m) were recorded optically from frog ventricular epicardium in calcium containing Ringer's solution directly under an extracellular stimulating point electrode. Anodal and cathodal S stimuli were applied at rest. As observed by previous investigators, the post‐pulse excitatory responses for cathodal pulses, compared with anodal pulses were greater. Changes in transmembrane potential (ΔV̄m) during the pulse were as expected for a passive cable only for low intensity pulses (< 4 × the cathodal threshold of excitation in diastole. CTE). However, at the higher intensities necessary to produce an excitatory response (> 6–8 × CTE), an “irregular” response in V̄m was observed—a reversal of the hyperpolarization during an anodal stimulus pulse and a reversal of the depolarization during a cathodal stimulus pulse. To elucidate further the biophysical basis for this behavior, ΔV̄m was mapped around the stimulating electrode. During stimulation, regions could be observed having a response with opposite polarity to that under the electrode (i.e. depolarization for an anodal pulse and hyperpolarization for a cathodal pulse). Removal of the bath solution or the addition of channel Mockers did not eliminate the occurrence of these regions. These regions appear to be the basis for the irregular behavior of ΔV̄m directly under the electrode as well as for anodal excitation.
Clinical Experience with a New Lead Comhining Active Fixation with Steroid Elution
Authors: PAYNE GILLIAN E. , DUNHAM DAVID G. , RAO ASHOK C. , GROWTHER ANNA P. , JOSEPH SIMON P. , SKEHAN J. DOUGLAS
Published: July 2006

The Medtronic lead engineering model number 10335A represents a new concept in lead design combining active fixation with steroid elution. It aims for immediate stability and low chronic thresholds. Twenty‐one leads, 9 atrial and 12 ventricular, were implanted in 13 patients (10 males, mean age 68; range 22–91 years). The atrial leads showed no rise in pulse width threshold at a voltage of 1.6 volts (mean thresholds at implant, 1, and 26 weeks; 0.1 ± 0.09 msec, 0.15 ± 0.04 msec, and 0.1 ± 0.03 msec, respectively). The ventricular leads had a small but significant rise between implant and 1 week at an output of 1.6 volts (0.07 ± 0.03 msec increasing to 0.11 ± 0.04 msec; P < 0.02) but no significant later rise (0.1 ± 0.04 msec at 2 weeks and 0.1 ± 0.05 msec at 6 months). These low chronic thresholds would allow early reprogramming of the unit to low voltages resulting in a battery saving with prolongation of the unit's life. There were no significant changes in the P and R wave amplitudes, but there was a fall in lead impedance in the ventricular leads between implantation and 1 week (P < 0.02) but none subsequently, and there was no significant change in atrial impedance. There were no sensing failures and no lead displacements. Despite impressive pacing characteristics, the study was suspended because of a high level of mechanical complications. Of the 96 patients implanted worldwide with 136 leads there were eight helix deformations, which will require redesign. However, the concept of steroid elution combined with active fixation appears to be an attractive and valid concept and is supported by this data; further studies are planned.
Radiofrequency Catheter Ablation of Concealed Atrio‐His Bypass Tract Involved in Paroxysmal Supraventricular Tachycardia
Authors: OKUMURA KEN , YAMABE HIROSHIGE , YASUE HIROEUMI
Published: July 2006

In a patient with paroxysmal supraventricular tachycardia and without any evidence for preexcitation syndrome or dual atrioventricular (AV) nodal pathways, the tachycardia reentry circuit consisted of the AV node as an antegrade limb of the circuit and a concealed atrio‐His bypass tract located in the posterior septum as a retrograde limb. During the tachycardia, the atrial potentials in the septal region and coronary sinus were inscribed in the QRS complex, and the earliest atrial activation site was located in the posterior septum. Ventricular extrastimulation at critically short intervals reproducibly demonstrated a ventriculo‐His‐atrial activation sequence with the same earliest retrograde atrial activation site as that during the tachycardia. Radiofrequency energy (20 W) was applied to this earliest activation site during ventricular pacing, which resulted in complete ventriculo‐atrial block within 2 seconds after energy application. The antegrade AV conduction property was not affected and the tachycardia was no longer induced. The patient has been free from tachycardia attack for a follow‐up period of 8 months. Therefore, radiofrequency catheter ablation for an atrio‐His bypass tract is feasible without inducing any AV conduction disturbance.
Rate Adaptive Cardiac Pacing Using Right Ventricular Venous Oxygen Saturation: Quantification of Chronotropic Behavior During Daily Activities and Maximal Exercise
Authors: LAU CHU‐PAK , TAI YAU‐TING , LEUNG WING‐HUNG , LEUNG SUM‐KIN , LI JOHN P.‐S. , WONG CHEUK‐KIT , LEE IRIS S.‐F. , YERICH CHARLES , ERICKSON MARK
Published: July 2006

Central venous oxygen saturation (SvOz) closely reflects cardiac output and tissue oxygen consumption. In the absence of an adequate chronotropic response during exercise, SvO2 will decrease and the extent of desaturation maybe used as a parameter for rate adaptive cardiac pacing. Eight patients with sinoatrial disease received a DDDR pacemaker capable of DDDR pacing by sensing either SVO2 or piezoelectric detected body movement. Both sensors were programmed to attain a rate of about 100 beats/min during walking, and with the lower and upper rates set at 50% and 90% of age predicted maximum, respectively. Chronotropic behavior of the two sensors were compared in the DDD mode with measurement of sensor responses, during everyday activities (walking, stair climbing, postural changes, and physiological stresses) and at each quartile of workload during a continuous treadmill exercise test. During walking at 2.5 mph, both sensors showed no significant difference in delay time (both react within 15 sees) or half‐time (SVO2= 36 ± 12 sec and activity 24 ± 3 sec; P = NS), although SVO2 driven pacing achieved 90% target rate response slowerthan activity sensing (124 ± 16 sec vs 77 ± 10 sec; P < 0.02). SVO2 pacing was associated with a more physiological rate response during walking upslope (68 ± 12 beats/min vs 57 ± 10 beats/ min; P < 0.05), ascending stairs (59 ± 10 beats/min vs 31 ± 6 beats/min; P < 0.05), and standing (34 ± 7 beats/min vs 9 ± 2 beats/min; P < 0.05). The SvO2 sensor significantly overpaced in the first quartile of exercise (51.8 ± 25.6% in excess of heart rate expected from workload), but the rate was within 20% of expected for the remainder of exercise. “Underpacing” was observed with the activity sensor at the higher workload. In conclusion, the SvO2 sensor demonstrated a more physiological response to activities of daily living compared with the activity sensor. Using a quantitative method, the speed of onset of rate response of the SvO2 sensor was comparable to activity sensing, and was more proportional in rate response. Significant overpacing occurs at the beginning of exercise during SVO2 driven pacing, which may be improved with the use of a curvilinear algorithm.
Implantation of an Automatic Defibrillator Using a New Nonthoracotomy Approach
Authors: KELLY PATRICIA A. , MANN DAVID E. , HARKEN ALDEN H. , MANART FRANK D. , REITER MICHAEL J.
Published: July 2006

Most current nonthoracotomy systems for defibrillator implantation use monophasic devices. To determine the safety and efficacy of a new nonthoracotomy lead configuration when used in conjunction with a device that used biphasic waveforms, 38 consecutive patients were taken to the operating room for implantation of a Cadence tiered therapy defibrillator system. The lead system consisted of a transvenous coil electrode positioned at the right atrial‐superior vena caval junction, a bipolar endocardial right ventricular lead, and a large patch placed subcutaneously near the cardiac apex. Of the 38 nontboracotomy defibrillator implantations attempted, 36 (95%) were completed with adequate defibriliation thresholds. The mean defibriliation threshold in these 36 patients was ± 563 ± 10 V (± 20 ± 1 J). There was no perioperative mortality. Complications included coil lead migration (5). sensing lead migration (1), infection (3), pneumothorax (2), arterial embolism (1), and folding of the subcutaneous patch with an increase in defibriliation threshold (1). No patient died during a median follow‐up period of 22 weeks. Fourteen patients (39%) had spontaneous sustained ventricular tachyarrhythmias, which were all successfully terminated by the implanted device. Shocks for nonsustained arrhythmias were aborted in eight patients (22%). Spurious discharges for sinus tachycardia or atrial fibrillation occurred in six patients (17%) and were readily diagnosed by examination of the stored electrograms. Thus, implantation of a biphasic tiered therapy defibrillator system using this nonthoracotomy approach is feasible in the majority of patients. The major complication associated with this procedure is lead dislodgment. The clinical course of these patients compares favorably with that of patients who have undergone defibrillator implantation via an epicardial approach.
Heart Weight Affects Spontaneous Defibrillation But Not Ventricular Fibrillation Threshold
Authors: RUIZ ESTELA , VALENTINUZZI MAX E.
Published: July 2006

Among the factors involved in the induction, generalization, and reversion of cardiac fibrillation, the amount of tissue is a determinant factor. One question is whether an increase in myocardial mass would or would not require the same electrical threshold. Accordingly, one objective was to determine if ventricular weight (VW) has any effect on the fibrillation thresholds (FTs). A second objective was to find a possible relationship between spontaneous defibrillation (SPDE) and heart weight. Fifty mongrel dogs of both sexes were used, of which 26 were 2‐ to 10‐week‐old puppies. The rest were adult animals of undetermined age. Fibrillation was induced with two types of stimuli directly applied to the heart. The stimuli were a train of rectangular pulses (TP) not synchronized with the ECG, and single pulses (SP) synchronized with and delayed from the R wave. TP type was used in one group with paddle electrodes; and the TP and SP types were used in a second group with hook electrodes. For both types, stimulation started at a low current and was increased until fibrillation was triggered. Once defibrillated, either spontaneously or by electrical shock, the procedure was repeated. Correlation coefficients between FT and VW were low (< 0.4), and scaling of the thresholds to VW resulted in hyperbolic relationship, for all cases, thus suggesting independence of the two parameters. SPDE fell sharply with weight. For values higher than 12 grams it was essentially nonexistent. VW does not have any effect on the FT but it dramatically influences the capacity of the myocardium to revert the arrhythmia by itself.
Safety and Diagnostic Yield of Noninvasive Ventricular Stimulation Performed Via Tiered Therapy Implantable Defibrillators
Authors: PINSKI SERGIO L. , SHEWCHICK JEANNIE , TOBIN MICHELLE , CASTLE LON W.
Published: July 2006

Extensive electrophysiological testing is critical for the effective utilization of sophisticated tachycardia detection and termination algorithms available in tiered therapy ICDs. To evaluate the safety and diagnostic yield of electrophysiological testing via noninvasive ventricular stimulation, we performed 294 electrophysiological studies in 154 patients (age 65 ± 10; left ventricular ejection fraction 0.36 ± 0.15) with tiered therapy ICDs. Stimulation was performed under methohexital anesthesia. A total of 928 sustained ventricular tachyarrhythmias were induced (3.1 ± 2.5 per procedure); monomorphic VT, 550; ventricular flutter, 74; and VF, 246. The results of invasive and noninvasive programmed stimulation were compared for 79 patients wbo had both studies under similar treatment. Overall concordance iras 83%, and did not differ significantly between patients who bad the noninvasive stimulation via epicardial or endocardial pacing leads. VF could be induced in 206 of 257 studies (82%), and it was less likely to be induced in patients on amiodarone (74% vs 85%; P = 0.02), or beta blockers (55% vs 83%; P = 0.017). No patient presented a serious complication. Minor complications occurred during 39 studies; transient laryngospasm in 1, unintended delivery of an ICD sbock to a conscious patient in 4; induction of sustained atrial fibrillation in 8; need for external rescue defibrillation sbocks in 13; and delivery of inappropriate sbocks for supraventricular rhythms in 14 studies. Noninvasive ventricular stimulation performed under methobexital anestbesia is safe. Its diagnostic yield compares favorably with that of conventional electropbysiological studies. VF can be induced in a majority of patients. There is good correlation between invasive and noninvasive programmed stimulation for induction of VT. Noninvasive ventricular stimulation may emerge as standard procedure for the initial programming and follow‐up of ICDs.
The Usefulness of a Stretch‐Polyester Pouch to Encase Implanted Pacemakers and Defibrillators
Authors: PARSONNET VICTOR , BERNSTEIN ALAN D. , NEGLIA DONNA , OMAR ARIF
Published: July 2006

This study was undertaken to assess the effects of enclosing permanent pacemaker and ICD pulse generators in a stretch‐polyester pouch prior to implantation. Follow‐up of 223 patients with oversized pacemakers and with ICDs and 344 witb standard‐sized pacemaker pulse generators showed that the pouch was effective in decreasing the frequency of pulse generator migration and extrusion.
Safety of Pacemaker Implantation in Patients with Transvenous (Nonthoracotomy) Implantable Cardioverter Defibrillators
Authors: CLEMO HENRY F. , ELLENBOGEN KENNETH A. , BELZ MICHAEL K. , WOOD MARK A. , STAMBLER BRUCE S.
Published: July 2006

While several reports bave documented the safety of implantation of transvenous pacemakers in patients with epicardial patch‐based impiantable cardioverter defibrillators (ICDs), the implantation of transvenous pacemakers in patients with transvenous (nonthoracotomy) ICDs has not been well‐descrihed. We present three patients with transvenous ICDs who subsequently underwent implantation of transvenous pacemakers without complication. Technical considerations and a testing protocol for detection of pacemaker‐ICD interactions are discussed.
Unsatisfying Results in Long‐Term Atrial Pacing with a Bipolar Active Fixation Atrial Lead
Authors: BUYS EUGENE M. , van HEMEL NORBERT M. , KELDER JOHANNES C. , van DESSEL PASCAL F.H.M. , BAKEMA LEX
Published: July 2006

A high dislodgment rate during long‐term atrial pacing using the unipolar sickle‐shaped active fixation lead was recently reported; therefore, the long‐term results of atrial pacing in 118 consecutive patients with the bipolar sickle‐shaped active fixation lead (Biotronik FH60‐BP) were evaluated. Between January 1989 and September 1993, 87 leads (74%) were inserted for dual chamber pacing and 31 leads (26%) for atrial pacing only. At the time of implantation, the bipolar atrial electrogram had a mean voltage of 4.4 ± 1.6 mV, whereas the acute atrial threshold was 0.72 ± 0.38 V and 1.46 ± 0.67 ml at 0.5‐msec pulse duration and mean resistance 506 ± 79 Ω. Early lead dislodgment (< 1 month after implantation) occurred in 9 patients (7.6%). During a mean follow‐up of 21.8 months (median 20.9 months), late dislodgment (> 1 month after implantation) occurred in 6 patients (5.1%) after a mean interval of 7.9 months (range 3–14 months). Due to the unacceptably high late dislodgment rate, which to date remains unexplained, new implants of this lead are not recommended.
The Economic Impact of Transvenous Defibrillation Lead Systems
Authors: WILLIAMSON BRIAN D. , MAN K. CHING , NIEBAUER MARK , DAOUD EMILE , STRICKBERGER S. ADAM , HUMMEL JOHN D. , MORADY FRED
Published: July 2006

The purpose of this study was to compare implant charges and convalescence for transvenous and epicardial defibrillation systems. Hospital stay, intensive care utilization, professional fees, and hospital bills were compared in 44 patients who underwent implantation of a cardiac defibrillator between September 1991 and May 1993. Twenty‐five consecutive patients received an epicardial lead system, while 19 consecutive patients underwent implantation of the entire transvenous defibrillation system in the electrophysiology laboratory. There were no significant differences between the two groups in mean age or left ventricular ejection fraction. There was a significant reduction in postoperative hospital convalescence from 7.2 ± 2.0 days with epicardial systems to 3.1 ± 1.5 days with transvenous systems (P < 0.001). Postoperative intensive care unit stay was significantly reduced with transvenous systems compared with epicardial systems (0.1 ± 0.2 vs 1.5 ± 0.9 days; P < 0.001). Hospital charges were also significantly reduced with the transvenous lead system implants. Mean implant charges were lower with transvenous systems; $32,090 ±$2,620 vs $38,307 ±$2,701 (P < 0.001); convalescence charges were lower: $5,861 ±$5,010 vs $12,447 ±$4,969 (P < 0.001); the total hospital bill was also significantly lower with transvenous systems: $53,459 ±$12,588 vs $71,981 ±$16,172 (P < 0.001). Professional fees for implantation ($4,131 ±$1,724 vs $6,100 ± 0, P < 0.001), convalescence care ($1,258 ±$960 vs $2,846 ±$1,770; P < 0.001), and total professional fees ($12,925 ±$4,772 vs $15,731 ±$4,055, P < 0.05) were lower in the transvenous defibrillation group. In conclusion, transvenous defibrillation lead systems are associated with significantly shorter postoperative recovery and significantly lower hospital and professional charges.
Automated Precision Current Delivery: An Alternative Method for Cardiac Defibrillation
Authors: ZIMMERMAN DONALD , FARKHANI FARZAD , WESLEY ROBERT C.
Published: July 2006

Substantial evidence suggests that the current associated with the discharge is a more precise predictor of defibrillation success than is the total energy of the discharge. However, virtually all commercially available defibrillators are calibrated in terms of energy. This article describes an alternative type of experimental defibrillator, which provides a precisely controlled current throughout the discharge waveform, independent of the load presented to the discharge electrodes (or “paddles”). The discharge current waveform is designed to have the classical critically damped sinusoid waveform, identical to that of the traditional energy‐based defibrillator when it is properly matched with its ideal load (the heart/thorax combination). The techniques used to obtain a controlled current discharge are discussed in addition to special operational features.
Efficacy and Safety of Ventricular Rate Responsive Pacing in Children with Complete Atrioventricular Block
Authors: RAGONESE PIETRO , GUCCIONE PAOLO , DRAGO FABRIZIO , TURCHETTA ATTILIO , GALZOLARI ARMANDO , FORMIGARI ROBERTO
Published: July 2006

Single chamber rate responsive pacing offers many potential advantages over the more complex dual chamber atrial tracking pacing mode in children, and the preservation of atrioventricular synchrony could be unnecessary in selected groups of pediatric patients. Twenty‐two pediatric patients (age range 9 months to 12 years; mean 6.5 years) had implantation of ventricular rate responsive (VVIR) pacemakers over a 2‐year period. All patients had chronic third‐degree atrioventricular block, and a normal ventricular function at rest. During the follow‐up each patient underwent a 24‐hour Holter monitoring, and ten performed a graded treadmill test in both ventricular fixed rate (VVI) and rate responsive (VVIR) pacing mode. Paced ventricular rates were found to be normal for age in all 22 patients; maximum rate did not reach the higher programmed rate during daily activities in any patient. Comparing the mean paced ventricular rate to the mean rates of blocked P waves, six patients showed a difference of more than 20 beats/min, which induced the pacemaker parameters to be reprogrammed. In all patients a significant correlation was found between variations of paced ventricular rate and variations of spontaneous blocked atrial rhythm (P < 0.05); this correlation persisted in the subsequent Holter controls in the ten patients with longer follow‐up. Exercise tolerance resulted normal in the ten patients who performed a treadmill test either in VVIR or VVI mode, with increased maximal heart rates and maximal systolic blood pressure in VVIR mode (P < 0.0013). Rate responsive ventricular pacemakers seem to adequately respond to the physiological needs of daily life of this selected group of children requiring permanent pacing.
Plasma ANP and Cyclic GMP Levels Versus Left Ventricular Performance at Different AV Delays in AV Sequential Pacing
Authors: SURDACKI ANDRZEJ , BEDNAREK JACEK , RADZISZEWSKI WALDEMAR , SZCZEPKOWSKI JACEK , DUBIEL JACEK S. , RUSKOAHO HEIKKI , SEDZIWY LUDWIK , WIECZOREK EWA
Published: July 2006

Eleven resting patients with an implanted DDD pacemaker were studied. After 30 minutes of AV sequentiai pacing at a rate of 80 beats/min with three consecutive atrioventricular delays (AVDs; 100, 150, and 200 msec) peripheral venous blood was drawn for further analyses by specific radioimmunoassays of atrial natriuretic peptide (ANP) and the ANP second messenger, cyclic guanosine monophosphate (cGMP). Relative changes in left ventricular (LV) stroke volume following alterations of AVD were assessed by means of pulsed‐Doppler echocardiography through measurement of LV outflow time‐velocity integrals (TVI). The optimal AVD (oA VD) was defined in individual patients as that which was associated with the greatest TVI and with improvement over both other AVDs of more than 4%. The oA VD was found in nine patients. For these nine patients no significant differences in either plasma ANP or cGMP between various AVDs were observed. However, we found such differences with respect to values measured at oAVD; both ANP and cGMP levels were lowest at oAVD. Pooling together the data obtained in 11 patients at three AVDs, a positive correlation between ANP and cGMP levels was found (r = 0.7, P < 0.0001. n = 33). Moreover, changes of plasma ANP and cGMP induced by every A VD increment of 50 msec were also correlated (r = 0.6, P < 0.01, n = 22). It is concluded that in AV sequential pacing at rest piasma ANP reaches minimal levels at the AVD, which provides the best LV performance. Although levels of cGMP changed in parallel with those of ANP, low relative values of cGMP differences may limit the usefulness of cGMP assays in optimization of the AVD.