bluuebunny/crossref_metadata_2025 huggingface dataset:
Complete Atrioventricular Block Following Mediastinal Irradiation: A Report of Six Cases
Authors: SLAMA MICHEL S. , LE GULUDEC DOMINIQUE , SEBAG CLAUDE , LEENHARDT ANTOINE R. , DAVY JEAN‐MARC , PELLERIN DENIS E. , DRIEU LUC H. , VICTOR JACQUES , BRECHENMACHER CLAUDE , MOTTÉ GILBERT
Published: July 2006

Complete atrioventricular block (AVB) following radiotherapy has been reported rarely, usually after high dose mediastinal irradiation for Hodgkin's disease or Jung or breast carcinoma. We report six new cases of episodic complete infranodal AVB, requiring permanent pacemaker implantation. The mean age was 48‐years old (ranging from 25–60) at the first Adams Stokes attack, mean delay was 12 years after irradiation (10–18), and mean radiation dose was 5.200 rads (4,000–6,500). All patients had abnormal interval electrocardiograms (right bundle branch block in two, left bundle branch block in three, alternating left and right bundle branch block in one). Electrocardiograms during the episode of AVB or Holter recordings were consistent with infranodal block in all patients; eleclrophysiological study performed in five patients confirmed infranodal AVB in four, and one was normal. Pericardial disease was constant, which included pericardial constriction in four patients. Two patients died after failure of pericardiectomy to improve congestive heart failure, due to epicardial, myocardial, and endocardial involvement. Noncardiac mediastinal lesions were present in four cases. Since this delayed complication may occur in patients of such age that the relation between the AVB and the chest irradiation is questionable, we propose the following etiologic criteria: high radiation dose (over 4,000 rads); delay of 10 years or more; abnormal interval tracings: pericardial involveinent; and associated cardiac or mediastinal radiation‐induced lesions.
Transesophageal Echocardiography to Improve Positioning of Radiofrequency Ablation Catheters in Left‐Sided Wolff‐Parkinson‐White Syndrome
Authors: GOLDMAN ANTHONY P. , IRWIN JAMES M. , GLOVER MATTHEW U. , MICK WIL
Published: July 2006

Two patients with the Wolff‐Parkinson‐White syndrome who underwent successful radiofrequency catheter ablation of their left‐sided bypass tracts are described. Transesophageal echocardiography, a relatively new echocardiographic technique, was utilized in both patients and provided excellent visualization of intracardiac anatomy as well as the catheter tip. Transesophageal echocardiography was also synergistic with fluoroscopy and the intracardiac electrogram in providing more precise catheter placement. In addition, the use of transesophageal echocardiography may reduce fluoroscopic exposure and shorten the procedure time.
Renal Extracorporeal Shock Wave Lithotripsy Performed in Patient with Implantable Cardioverter Defibrillator
Authors: VENDITTI FERDINAND J. , MARTIN DAVID , LONG AUDREY L. , ROTH ROBERT A.
Published: July 2006

The effect of extracorporeal shock wave lithotripsy on the automatic implantable Cardioverter defibrillator is unknown. To evaluate what effect might occur, a non‐implanted automatic implantable Cardioverter defibrillator was subjected to a full course of extracorporeal shock wave lithotripsy while inactive. Bench testing by the manufacturer after lithotripsy demonstrated normal function of the device. A patient with an automatic implanted Cardioverter defibrillator who required contralateral extracorporeal shock wave lithotripsy then underwent this procedure. The right renal calculus was destroyed successfully with no apparent damage to the automatic implantable Cardioverter defibrillator. A test of the automatic implantable Cardioverter defibrillator after lithotripsy demonstrated normal sensing and conversion of induced ventricular tachycardia.
Tachycardia Recognition and Diagnosis from Changes in Right Atrial Pressure Waveform—A Feasibility Study
Authors: KAYE GERRY C. , ASTRIDGE PENNY , PERRINS JOHN
Published: July 2006

Implantable defibrillators either monitor heart rate or use a probability density function to detect ventricularfibrillation/tachycardia. As a result, they are unable to discriminate sinus tachycardia and atrial arrhythmias from malignant ventricular rhythms. We have assessed high fidelity fiber‐optic pressure recordings in the right atrium during cardiac arrhythmias in 23 patients (mean age 44 years, 11 females) undergoing electrophysiological study. The unfiltered pressure signal was amplified and recorded on paper. During sinus rhythm, a constant amplitude deflection occurred during atrial systole (a wave), A characteristic waveform pattern was observed during each of the studied tachyarrhythmias. which included atrial flutter and fibrillation, atrioventricular nodal reentrant tachycardia, atriovenrricular reentrant tachycardia, and ventricular tachycardia with and without ventriculoatrial conduction. The waveform pattern allowed clear visual discrimination of the underlying arrhythmia. Mean atrial pressure was increased during all arrhythmias and did not allow discrimination of the nature of the tachycardia. High fidelity pressure recordings produced characteristic appearances for pattern recognition of each arrhythmia studied. They allowed determination of the temporal relation between electrical and mechanical cardiac events and may have potential in the detection and recognition of cardiac arrhythmias.
Advances in Applications of Radiofrequency Current to Catheter Ablation Therapy
Authors: HUANG SHOEI K. STEPHEN
Published: July 2006

In the past 5 years, numerous reports have appeared of the use of radiofrequency (RF) current as an energy source for catheter ablation therapy of cardiac arrhythmias. Laboratory investigations using in vitro and in vivo animal models to study the biophysical and histologic effects as well as to assess the efficacy and safety of this technique in ablating various cardiac structures have been extensively performed and have led to successful applications in humans. Clinical experience with RF catheter ablation of the AV junction and accessory pathway has proliferated each year. However, experience with RF ablation of the VT focus remains quite limited. With further advances in catheter electrode design for mapping and ablation, a widespread application of RF catheter ablation to the treatment of cardiac arrhythmias is anticipated.
Treatment of Thalamic Pain by Chronic Motor Cortex Stimulation
Authors: TSUBOKAWA TAKASHI , KATAYAMA YOICHI , YAMAMOTO TAKAMITSU , HIRAYAMA TERUYASU , KOYAMA SEIGOU
Published: July 2006

All forms of therapy, including chronic stimulation of the thalamic relay nucleus, can provide satisfactory pain control in only 20%‐30% of cases of thalamic pain syndrome. In order to develop a more effective treatment for fhalamic pain syndrome, we investigated the effects of stimulation of various brain regions on the burst hyperactivity of thalamic neurons recorded in cats after deafferentiation of the spinothalamic pathway. Complete, long‐ term inhibition of the burst hyperactivity was induced by stimulation of the motor cortex, Based on this experimental finding, we treated seven cases of thalamic pain syndrome by chronic motor cortex stimulation employing epidural plate electrodes. Excellent or good pain control was obtained in all cases without any complications or side effects. During the stimulation, an increase in regional blood flow of the cerebral cortex and thalamus, a marked rise in temperature of the painful skin regions, and improved movements of the painful limbs were observed. These results suggest that thalamic pain syndrome can be most effectively treated by chronic motor cortex stimulation.
Bipolar Atrial Triggered Pacing to Restore Normal Chronotropic Responsiveness in an Orthotopic Cardiac Transplant Patient
Authors: KACET SALEM , MOLIN FRANCK , LACROIX DOMINIQUE , PRAT ALAIN , POL ANNIE , WAREMBOURG HENRI , LEKIEFFRE JEAN
Published: July 2006

A not uncommon arrythmia in cardiac orthotopic transplantation patients is sinus node dysfunction with chronotropic incompetence. This is a result of the surgical procedure that denervates the donor heart while the native sinus node may be normal but isolated in the remnant of the recipient atrial wall that serves as the anastomotic site. We were able to restore “normal sinus node function” in a heart transplant patient utilizing a bipolar single chamber pacemaker programmed to the triggered mode. A single unipolar active fixation lead was positioned in each atria. Both leads were connected to a bipolar AAT pulse generator utilizing a Y adaptator. The native atrium with its innervated intact sinus node effectively drove the donor atrium and thus the heart.
Cardiac Electrophysiological Experiments in Numero, Part I: Concepts and Strategies of Mathematical and Computer Models
Authors: MALIK MAREK , CAMM A. JOHN
Published: July 2006

This article is the first of three articles that review mathematical and computer models of the heart and describe their construction, development, research potential, and clinical utility. This article explains the methodological principles of mathematical and computer simulation of biomedical systems. The strategies of model construction, testing, and application are presented; the advantages and limitations of computer simulation studies are explained, and the basic value of computer simulation for cardiological research and practice is discussed.
Fusion or Confusion on Holter Recording
Authors: VAN GELDER L.M. , BRACKE F.A.L.E. , EL GAMAL M.I.H.
Published: July 2006

Holter recording of a patient with an implanted dual chamber rate responsive pacemaker revealed an electrocardiogram, where ventricular depolarization seemed to be initiated by the atrial stimulus. In a second patient with a VVI pacemaker, Holter recording showed delay of the pacemaker impulse that was registered after the onset of ventricular depolarization. Misalignment in one of the recorder heads of the display system was responsible for this phenomenon, which in case of dual chamber pacing could have been easily misinterpreted as pacemaker malfunction.
Influence of Propranolol on the Ventricular Depolarization Gradient
Authors: LASARIDIS KYRIAKOS , PAUL VINCE E. , KATRITSIS DEMOSTHENES , WARD DAVID E. , CAMM A. JOHN
Published: July 2006

Sensing of the ventricular depolarization gradient (VDG) has recently been used as The basis of a closed‐loop rate responsive pacemaker. Factors influencing this aspect of the evoked response have not been fully evaluated although previous reports have suggested that sympathetic stimulation and circulating catecholamines are primarily responsible for the observed changes during stress and exercise. In five patients (Table I), four males and one female (mean age 60.4 ± 20.1 years) implanted with the Prism pacemaker, the pacing response to exercise and tilting was assessed before and after the infusion of propranolol. There was an increase in the pacing rate in all patients during the infusion of the drug (mean 27 ± 12.9 beats/min) suggestive of a direct drug effect on the VDG. The rate control parameter (RCP) of the pacemaker, the numerical equivalent of the VDG, was significantly different after the administration of propranolol (P < 0.01). However, exercise performance and pacing rate behavior were not different after beta blockade. The pacing rate increase observed when tilting patients to the supine position was not altered by propranolol. Out date suggest that factors other than adrenergic stimulation may be of importance in affecting the ventricular evoked response and accordingly the rate adaptation of the Prism pacemaker.
Catheter Ablation of Ventriculoatrial Conduction in the Treatment of Pacemaker‐Mediated Tachycardia
Authors: PITNEY MARK , DAVIS MICHAEL
Published: July 2006

Pacemaker generator reprogramming does not always present an adequate solution to the problem of pacemaker‐mediated tachycardia. A case is described where direct current shock catheter ablation of ventriculoatrial conduction prevented pacemaker‐mediated tachycardia and allowed optimal dual chamber pacemaker programming.
Activity‐Sensing Rate Responsive Versus Conventional Fixed‐Rate Pacing: A Comparision of Rate Behavior and Patient Well‐Being During Routine Daily Exercise
Authors: CANDINAS RETO A. , GLOOR HANS O. , AMANN FRANZ W. , SCHOENBECK MARIETTE , TURINA MARKO
Published: July 2006

Rate responsive single chamber pacing (WIR) may be the pacemaker of choice in pafients who are not suitable candidates for a dual chamber system. Several studies, most of them performed in an exercise laboratory, have shown a significantly higher exercise capacity demonstrating an improvement in cardiac output and anaerobic threshold compared to conventional fixed rate pacing (VVT). Expressing our idea that stress testing in an “artificial environment” on a bicycle or motor driven treadmill has its limitations and may be difficult to extend into patient's daily life, we designed an outdoor study imitating patient's daily activity. Twenty‐one patients with an activity‐sensing rate responsive pacemaker performed in a double blind fashion in VVI and VVIR mode the following test circuit: walking 170 meters on flat ground, 210 meters incline, climbing a flight of stairs, and the same circuit in reverse order, and therefore “downhill”. Heart rate behavior was recorded by Holter monitoring and patients subjective feelings of well‐being, i.e. fatigue and dyspnea were also evaluated, VVIR pacing responded promptly to exercise, i.e., walking on a flat ground, but no further significant increase in pacing rate was observed in relationship to the strength of physical activity while walking inclined or climbing stairs. While patients became exhausted, a nonphysiological decrease in heart rate sometimes occurred. Despite these limitations 6 of 12 patients who had a paced‐only rhythm while exercising in both VVI and VVIR mode reported feeling significantly belter in the VVIR mode, expressing less dyspnea and fatigue. In contrast, two of nine patients having only intermittently paced rhythm preferred the VVIR mode. Patients with lower ejection fraction (EF) were more likely to show subjectively a benefit while exercising in VVIR mode, compared to those with less reduced or normal EF. Despite the technical limitations of using a piezo crystal for rate adaptation, WIR pacing is an important option in paced‐only patients, but it seems less beneficial in patients with only intermittent paced rhythm.
Fate of Explanted ICD Patients
Authors: ZILO PHILIP , GROSS JAY N. , JOHNSTON DEBORAH , FISHER JOHN D. , FURMAN SEYMOUR
Published: July 2006

Of 56 consecutive patients who underwent an initial AICD implantation at our center, we analyzed eight patients who subsequently had their units explanted and not replaced by other antitachycardia devices. The mean age was 57.8 years, mean ejection fraction was 28.4%; six patients had coronary disease and two had cardiomyopathy. The presenting arrhythmia was sudden death in four patients and sustained ventricular tachycardia in four others. Mean follow‐up from implant to explant was 25 ± 22 months, and 22 ± 10 months from explant to end of follow‐up. Reasons for explantation were: infection in five patients, lead fracture in one patient, battery depletion in one patient, and one patient underwent cardiac transplantation. Devices were not reimplanted because of: patient refusal in three patients, physician discretion in two patients (one recurrent infection, one received no shocks over 24 months), cardiac transplantation in one patient, ablation of VT focus in one patient, and one patient died while being treated for infection. Three patients died 2, 21, and 26 months after device explantation of nonsudden cardiac, sudden cardiac and noncardiac causes, respectively. Conclusions: Preoperative clinical parameters were not indicative of a lower risk of arrhythmic events in these patients as compared to the general population of AICD implantees. Of eight patients, two received alternate nonmedical therapy, one died while receiving treatment for a device‐related infection; of the five remaining patients none died of cardiac causes. Termination of AICD therapy for malignant ventricular arrhythmias does not imply imminent sudden cardiac death for most patients treated by alternate modes of therapy.
Recognition of Mutiple Tachyarrhythmias by Rate‐Independent Means Using a Small Microcomputer
Authors: TOOLEY M.A. , DAVIES D.W. , NATHAN A.W. , CAMM A.J.
Published: July 2006

New implantable devices are now available that can offer different therapies for different arrhythmias but they need a method of discriminating between these rhythms. Heart rate analysis is predominantly used to discern between sinus rhythm (SR) and pathological tachycardias but this may be of limited value when the rates of the rhythms are similar. An enhanced form of Gradient Pattern Detection (GPD) has been developed using an 8‐bit microcomputer that can distinguish between Sfl and up to three other arrhythmias in real time. This is a method based on electrogram morphology where each rhythm s specific electrogram is classified by a sequence of gradient zones. The microprocessor of the computer is of similar processing power to ones used in current pacemakers. Five patients with multiple arrhythmias were studied. Four had ventricular tachycardia (VT) and one had three conduction patterns during supraventricular tachycardia (SVT). Bipolar endocardial right ventricular electrograms were recorded during SR and tachycardia in all patients. The computer would first learn about each different rhythm by a semi‐automatic means. Once all the rhythms were learned the program would enter the GPD analysis phase. The computer would output a series of real‐time rhythm specific marker codes onto a chart recorder as it recognized each rhythm. Sixteen different arrhythmias (13 VT, 3 SVT) were examined for this study. All rhythms (including SR) were distinguished from each other except in the case of one patient with six VTs where two VTs had identical shapes and therefore could not be detected apart. The method would be a useful addition to heart rate analysis for future generations of microprocessor assisted pacemakers.
A Packaged Solution to the Problems of Testing Arrhythmia Control Devices at Implant
Authors: HALUSKA EDWARD A. , CALFEE RICHARD V.
Published: July 2006

A composite implantable arrhythmia control device (ACD) implements the functions of a bradycardia pacemaker, an antitachycardia pacemaker, a cardioverter, and a defibrillator in an integrated fashion. Given this broad spectrum of functionality, the implant testing for these devices can become a formidable endeavor requiring a large ensemble of expensive, complex support equipment, and a significant amount of time. However, if this procedure is not carried out correctly, the device might later fail to defibrillate. This article presents a unique packaging system for an ACD that allows the device to be used while it is still in its sterile package. The device may then be used during implant testing as the defibrillation test unit. This collapses the amount of support equipment that is required to just the ACD, its programmer, and an optional switch box. By providing additional support specifically for implant testing through the ACD programmer, implant testing may be reduced to a quick, easy‐to‐manage procedure. Since the device used during implant testing is the same device that will be implanted, this packaging system offers the further advantage that the physician can be confident that, once implanted, the ACD will function correctly.
Differences in the Pathological Changes in Dogs' Hearts After Defibrillation with Extrapericardial Paddles and Implanted Defibrillator Electrodes
Authors: HARMAN DEIRDRE , MATTHEWS ROSS , GILLI NORMA , MCCULLOCH ROY
Published: July 2006

A comparison was made between the pathological changes in the myocardium of eight dogs, each receiving about 90 joules of energy in a series of defibrillation discharges, delivered either between paddles placed against the pericardium (3 dogs) or between implanted Telectronics 040–105 defibrillation patch electrodes (5 dogs). The changes in the myocardium were most pronounced where the paddles had been applied to the pericardium. There was transmural damage beneath the left and right paddle positions and in the surrounding tissues. Extensive subepicardial and subendocardial myocyte damage was obvious histologically in the right ventricle of one of the patch dogs and in all of the paddle dogs. The percentage of damaged myocardial mass, both right ventricular and total involvement, was higher in the three paddle dogs compared with the five patch dogs. There was septal damage in the heart of one paddle dog. Necrosis of the right ventricular wall was observed in three of the patch dogs and in all the three paddle dogs. Scattered necrotic myocytes and some patches of mild necrosis up to 1‐mm deep were observed in the left ventricle of the patch dogs (severity score 1–3). The necrosis was more extensive in the paddle dogs, ranging from mild necrosis < 1‐mm deep to marked necrosis incorporating half‐to‐whole ventricular wall thickness (severity score 3–5).
A Right Atrial Mass in the Presence of a Permanent Pacemaker Electrode in a Patient with Polycythemia Vera
Authors: HENDLER A. , KRAKOVER RICARDO , STRYJER DOV , SCHLESINGER ZWI
Published: July 2006

A case of a huge right atrial mass that developed 2 years after a permanent pacemaker implantation is described. The patient had a history of polycythemia vera, which is known to present a high tendency towards the development of thrombosis. In light of this fact, we suggest that in similar cases a full echocardiography follow‐up should be performed, and long‐term anticoagulant therapy should be considered in selected cases.
Lack of Physiological Adaptation of the Atrioventricular Interval to Heart Rate in Patients Chronically Paced in the AAIR Mode
Authors: MABO PHILIPPE , POUILLOT CHRISTOPHE , KERMARREC ALAIN , LELONG BERNARD , LEBRETON HERVÉ , DAUBERT CLAUDE
Published: July 2006

Seventeen consecutive patients, aged 56 ± 12, were chronically paced in the AAIR mode for a symptomatic sinus node disease with atrial chronofropic incompetence defined by a peak exercise heart rate (HR) < 75% of the maximal predicted heart rate (MPHR) mean = 65 ± 10%). Sensors used were activity sensing (n = 7), minute ventilation (n = 6), or respiratory rate (n = 4), Basic pacing rate was programmed at 71 ± 5 beats/min and the maximal sensor rate at approximately 85% MPHR (143 ± 10); other sensor parameters were programmed individually. Six months after implant, two standardized and symptom limited exercise tests were performed in random order, AAJ and AAIR modes, respectively. AAIR pacing significantly improved peak exercise HR (139 ± 14 vs 112 ± 30 beats/min; P < 0.01), maximal sustained workload (132 ± 42 vs 110 ± 38 watts; P < 0.02), and total exercise duration (724 ± 299 vs 594 ± 245 sec; p < 0.02) compared to the AAI mode. In all 17 patients, HR was continuously sensor driven in the AAJR mode, making it possible to precisely study the adaptation of the stimulus‐R interval and of the stimulus‐R: RR ratio during exercise. Six patients normally adapted with a progressive shortening. Six others did not adapt at all without any variation of interval. Five patients paradoxically increased their stimulus‐fl interval (286 ± 10 msec at peak Evs 220 ± 19 msec at rest) and their srimulus‐R:RR ratio (67 ± 20%vs29 ± 4%), producing P waves occurring immediately after, or even within the R wave of the preceding cycle; two patients complained of severe exercise related symptoms corresponding to the so‐called “AAIR pacemaker syndrome.” The principal factors involved in the nonadaptalion of AV interval to HR were related to the patient (organic heart disease, with the particular problem of the denervared heart; (he bradytachy syndrome; and the use of drugs, especially beta blockers and Class I antiarrhythmic drugs) or to the pacemaker (“overstimulation” phenomenon). These observations constitute an additional argument for wider indications of implanting DDDR units in these patients.
Myocardial Rupture After Pulling Out a Tined Atrial Electrode with Continuous Traction
Authors: GARCÍA‐JIMÉNEZ ANTONIO , MANUEL CARLOS , ALBÁ BOTANA , MANUEL JOSÉ , CORTÉS GUTIÉRREZ , GALBÁN CRISTÓBAL , ISABEL RODRÍGUEZ , DIÉGUEZ ALVAREZ , PELLEJERO FRANCISCO NAVARRO
Published: July 2006

Transvenous traction for the removal of retained pacemaker electrodes is common practice with few reported complications. This case reports a patient with a DDD pacemaker with extruded electrodes, who died of a myocardial rupture at the atrial lead site after prolonged (i.e., after 24 hours) traction was applied.
Follow‐Up of a Respiratory Rate Modulated Pacemaker
Authors: SANTOMAURO MAURIZIO , FAZIO SERAFINO , FERRARO SERGIO , MADDALENA GIOVANNI , PAPACCIOLI GIUSEPPE , PAPPONE CARLO , SACCA LUIGI , CHIARIELLO MASSIMO
Published: July 2006

The efficacy of 27 respiration sensitive rate modulated pacemakers (Biorate RDP‐3, Biotec) implanted in the left pectoral area was evaluated every 3 months during a mean follow‐up period of 29 months (range 10‐50 months]. Rate modulation function was unchanged other than for three patients in whom the auxiliary leads became displaced. Two implants lost ventricular sensing in this nonprogrammable model. In all but the three patients, Holter monitoring demonstrated pacing rate variation corresponding to daily activity. Stress test duration increased from 8.2 ± 1.5 minutes (in fixed rate WI rate) to 12.83 ± 2.0 minutes (in the VVIR mode) (P < 0.05). Right arm movement increased the pacing rate by 5 ± 3 beats/min (NS), while the left arm movement increase was 30 ± 5 beats/min (P < 0.05). Mental, arithmetic, and nifedipine tests did not change the rate modulated pacing rate. The system responded to a change in respiratory rate by an increase in stimulation rate. A satisfactory response in sensitivity and velocity was present only with medium‐high workloads. Interference with rate modulation occurred with movement of the arm ipsillateral to the implanted pulse generator.
Nd: YAG Laser‐Photocoagulation: Acute Electrophysiological, Hemodynamic, and Morphological Effects in Large Irradiated Areas
Authors: WIETHOLT DIETMAR , ALBERTY JÜRGEN , HINDRICKS GERHARD , VOGT BARBARA , HAVERKAMP WILHELM , BLASIUS SEBASTIAN , GÜLKER HARTMUT , BREITHARDT GÜNTER
Published: July 2006

Laser‐photocoagulation (LPC) of arrhythmogenic myocardium has been reported to successfully ablate ventricular tachycardia. The purpose of this study was to investigate the acute hemodynamic and electrophysiological effect of continuous laser energy (Nd: YAG, 1060 nm) applied via a 0.4‐mm quartz fiberoptic on the epicardial surface of the heart in nine dogs. A total of 51 ± 2.3 pulses was delivered in each animal to induce homogeneous tissue necrosis. Applied energy was 12.3 ± 2.7 J/mm2, irradiated surface measured 12.6 ± 3.0 cm2, lesion depth was 6.3 ±1.2 mm (range: 5.0–8.1 mm), lesion volume was 8.1 ± 2.8 cm3 (6.8% of left ventricular [LV] mass). After LPC, epicardial stimulation threshold significantly rose from 1.0 ± 0.3 to 10.2 ± 4.9 mA in the border zone to nontreated tissue and from 0.9 ± 0.4 to 32 ± 15.7 mA in the center of the lesions. Loss of epicardial activation in the irradiated areas could be demonstrated by epicardial mapping. Ventricular extrasystoles during LPC were seen in all dogs, ventricular tachycardia in seven, and ventricular fibrillation in two dogs. After LPC, cardiac output and LV dP/dtmax significantly decreased by 14.2% and 11.2%. LPC induced predictable homogeneous tissue edema, eosinophilic staining, contraction band necrosis, and sharp demarcated hemorrhagic border zones with a sharp electrical border zone to nontreated tissue and loss of epicardial activation. During LPC, various arrhythmogenic effects could be observed. However, no persistent arrhythmic activity developed after LPC. The results confirm the feasibility of epicardial LPC of the myocardium. Although not tested in this study, LPC of arrhythmogenic tissue may also be feasible as a treatment modality of ventricular tachycardia.
Differentiation Between Monomorphic Ventricular Tachycardia and Sinus Tachycardia Based on the Right Ventricular Evoked Potential
Authors: BELZ MICHAEL K. , ELLENBOGEN KENNETH A. , CAMM A. JOHN , PAUL VINCE E. , ROGERS REGINA , DAWSON ALBERT K.
Published: July 2006

The differentiation between ventricular tachycardia (VT) and smus tachycardia (ST) is problematic in some patients with implantable defibrillators and/ or antitachycardia pacemakers. The Integral of the ventricular endocardial evoked response, or paced depolarization integral (PDI), has been demonstrated to undergo characteristic changes with a variety of stimuli including catecholamines, pacing rate, and exercise. We hypothesized that the PDI recorded from a unipolar transvenous right ventricular endocardial catheter would differentiate VT from ST. The PDI was calculated from a unipolar pacing stimulus, delivered via a cathode in the right ventricular apex, and the reference electrode, a quadripolar catheter positioned in the superior vena cava. PDIs were measured in 22 patients during VT and sinus rhythm. The PDI measured during sinus rhythm was 579 ± 240 μV‐sec and the PDI during VT was 894 ± 411 μV‐sec (P < 0.001). In a subset of seven patients, PDIs were measured during VT, sinus rhythm, and ST induced by catecholamine infusion or exercise. In this subset, the PDI during sinus rhythm was 645 ± 295 μV‐sec, during ST 588 ± 308 μV‐sec (9% decrease from sinus, P = 0.05), and during VT 863 ± 342 μV‐sec (33.9% increase, P = 0.01). These data indicate that the measurement of the PDI is potentially useful in differentiating VT from ST.
Correlation of Electrophysiological Activation Patterns to Tension Generation in Stimulated Latissimus Dorsi Muscle
Authors: RHEE EDWARD K. , FURNARY ANTHONY P. , ELSON JAMES J. , KAO RACE L.
Published: July 2006

Skeletal muscle has been used for biomechanical assist in experimental and clinical studies. Central to the success of these procedures is the generation of sufficient muscle force for the lifetime of the subject. Burst (tetanic) stimulation results in summation of individual twitches and generates higher power output. However, the superiority of paraneural versus intramuscular as well as proximal versus middle and distal intramuscular stimulations remains unclear. Electrophysiological mapping and mechanical performance of seven canine latissimus dorsi muscles were analyzed. The mechanism of higher tension generation produced by: (1) increased temporal summation; (2) greater motor units activated; or (3) result of both were determined. The parameters primarily dependent on the number of activated motor units are significantly greater following paraneural and proximal intramuscular stimulations. The parameters mainly related to temporal summation are not different between various electrode configurations. For intramuscular stimulation, it is the location of interelectrode field rather than the location of the cathode perse that determines the mechanical performance of the skeletal muscle. Furthermore, tension development of skeletal muscle is primary nerve activation rather than direct muscle stimulation. The higher tension generation that resulted from different electrode configurations is produced by activating a higher number of muscle fibers through the neuromuscular junctions.
Multicenter Clinical Evaluation of a New SSIR Pacemaker
Authors: BONGIORNI MARIA GRAZIA , SOLDATI EZIO , ARENA GIUSEPPE , de SIMONE LUIGI , CAPUCCI ALESSANDRO , GALLI ROBERTO , PARLAPIANO MARIO , CAZZIN ROBERTO , MORACCHINI PIERVITTORIO , LEONARDI CRISTINA , ZARDO FABIO , OMETTO RENATO , VINCENZI MARIO , CHARLES RICHARD , MAKIN CAROLYN , BIAGINI ANDREA
Published: July 2006

A multicenter clinical evaluation of Sorin Swing 100, a new SSIR pacemaker with a gravimetric sensor, was performed by seven different centers enrolling a total of 89 patients, 56 men and 33 women, mean age 73.1 years, for pacemaker implantion (73 patients) or pacemaker replacement (16 patients). Pacing mode was VVIR in 73 patients and AAIR in 16. The behavior of pacing rate was evaluated 3 months after the implant by performing a 24‐hour Holter monitor, an exercise stress test, and tests for the assessment of mechanical external interference (MEI). A physiological behavior of the paced rate was always observed during Holter monitoring. In 52 completely paced patients mean diurnal, nocturnal, and maximal heart rate were, respectively, 74.9 ± 5.7 ppm, 58.1 ± 5.8 ppm, and 113.4 ± 12.7 ppm; a paced rate exceeding 100 ppm was reached on the average 5.6 times/Holter monitor. In all but two patients the sleep rate (55 ppm) was reached during the night or long resting time. During exercise stress test a direct correlation between the increase in pacing rate and the increase in workload was observed; the mean maximal heart rate reached in 49 completely paced patients was, respectively, 102.8 ± 9 ppm in 17 patients who accomplished stage 1, 116.2 ± 13.6 ppm in 28 patients who accomplished stage 2, and 133 ± 6.7 ppm in 10 patients who accomplished stage 3 of the Bruce protocol. MEI testing never increased the pacing rate over the noise rate (10 ppm over the basic rate). In only seven patients the results obtained suggested to change the nominal set up of the pacemaker. Our experience clearly indicates that Swing 100 is an effective, reliable, and easy to use SSIR pacemaker. The availability of the sleep rate allows a more physiological pattern of pacing rate and can lead to significant energy saving.
Clinical Results of Automatic Slope Adaptation in a Dual Sensor VVIR Pacemaker
Authors: van KRIEKEN FRITS M. , PERKINS JOHN P. , SIGMUND MARKUS
Published: July 2006

Manual slope programming in rate adaptive pacemakers can be time consuming. This may become worse with dual sensor devices. The remedy is to let the pacemaker automatically learn the slopes. Fast learning replaces initial manual slope programming. Daily learning is a continuous process to determine and optimize slopes during daily life. Both methods are known for a QT sensing pacemaker. Fast learning is known for other single sensor devices. The aim of this study was to follow daily learning in a QT and activity dual sensor pacemaker, starting with factory slope settings. Six patients were studied for about 8 weeks. The daily learning algorithm appeared to be elective, showing the desired regulation processes. It took 2–5 weeks to reach full rate response.
Clinical Interest of a Sensor Driven Algorithm Limiting Ventricular Pacing Rate During Supraventricular Tachycardia in Dual Chamber Pacing
Authors: MAHAUX VERONIQUE , VERBOVEN YVES , WALEFFE ANDRE , KULBERTUS HENRI
Published: July 2006

A sensor driven algorithm limiting ventricular pacing rate during supraventricular tachycardia (SVT) is included in a dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay, 294‐03, Intermedics Inc.). According to the intensity of concomitant exercise, the ventricular pacing rate is limited either to the programmed maximum pacing rate (MPR) or to an interim lower limit, called “conditional ventricular tracking limit” (CVTL). The MPR prevails over the CVTL when the sensor calculated pacing rate exceeds the minimal rate by more than 20 beats/mm. The purpose of the study is to determine the clinical safety and efficacy of this algorithm in patients with intermittent SVT. Method: a Relay was implanted in four patients with a bradycardia/tachycardia syndrome and in four patients with complete atrioventricular block (CAVB). All had episodes of paroxysmal atrial tachycardia. The units were programmed in DDDR: rate responsive parameters were adjusted by simulating the rate response during three levels of exercise to let the MPR override the CVTL only during strenuous exercise. Holter monitors and exercise testings were performed at 3‐month follow‐up. Results: in seven patients, Holter recordings showed Supraventricular arrhythmias at rest with a ventricular pacing rate limited to the CVTL. Appropriate rate increases during exercise testings were also demonstrated. Three devices had to be reprogrammed in DDIR tone patient suffering from nearly permanent atrial flutter and two patients not tolerating the CVTL pacing rate at rest). Conclusion: the CVTL algorithm is effective in protecting against high ventricular pacing rates during Supraventricular arrhythmias. It allows the selection of the DDDR mode even with a high MPR in patients with intermittent SVT.
Reliability of an Automatic Sensing Algorithm
Authors: BERG MONIKA , FRÖHLIG GERD , SCHWERDT HOLGER , BECKER RÜDIGER , SCHIEFFER HERMANN
Published: July 2006

Automatic adaptation of the atrial sensitivity was evaluated in 18 patients with dual chamber pacemakers (Intermedics, Inc., Relay) in the unipolar mode. After atrial sensitivity was stabilized in the upright position, patients underwent a 1.0 W/kg body weight exercise for 5 minutes. A 24‐hour Holter EGG was recorded, and the maximum and minimum atrial sensitivity values reached were stored in the memory of the pulse generator. In a second series of 12 patients, Holter ECGs were recorded twice, starting with the same sensitivity but with automatic adaptation alternately switched “on” or “off.” Results of the exercise test: mean atrial sensitivity declined from 2.30 ± 0.77 mV to 2.03 ± 0.68 mV. There was no change in five patients, a slight increase in two patients, and lowering of the atrial sensitivity was observed in 11 patients, the difference ranging from 0.2 to 1.0 mV. A total of two P waves in two patients were missed by the atrial amplifier. The minimum and maximum sensitivity reached during Holter monitoring averaged 2.31 ± 0.67 mV versus 1.72 ± 0.71 mV (difference 0‐1.7 mV). Normal pacemaker function was found in six patients, including one patient without any intrinsic atrial activity. Malsensing of less than five P waves occurred in four patients. More than 50 sensing defects resulted from ectopic atrial beats (four patients). We observed atrial oversensing in three cases; one patient showed atrial over‐ and undersensing. The comparison between fixed and variable sensitivity did not reveal any superiority of automatic adaptation. Conclusion: earlier findings of atrial signal variation during daily life are confirmed. Although quite reliable during exercise studies, automatic adaptation of atrial sensitivity is not able to compensate for sudden changes in atrial electrogram or to sufficiently suppress extracardiac noise.
Diastolic Mitral Regurgitation in Patients with First‐Degree Atrioventricular Block
Authors: ISHIKAWA TOSHIYUKI , KIMURA KAZUO , MIYAZAKI NAOMICHI , TOCHIKUBO OSAMU , USUI TAKASHI , KASHIWAGI MASANOBU , ISHII MASAO
Published: July 2006

Diastolic mitral regurgitation has been observed in patients with DDD pacemakers when the atrioventricular (AV) delay was prolonged. However, diastolic mitral regurgitation associated with first‐degree AV block has not been fully studied. We examined transmitral blood flow in 24 patients with first‐degree AV block and normal cardiac function (ages 35.3 ± 17.4 years), and in nine patients with DDD pacemakers and normal cardiac function (ages 73.1 ± 8.1 years), using pulsed Doppler echocardiography. Diastolic mitral regurgitation was observed in 19 of 24 patients with first‐degree AV block. Although PQ interval was shortened from 0.32 ± 0.06 to 0.20 ± 0.05 seconds (P < 0.01) after 1 mg atropine sulfate IV, the interval between P wave (ECG) and the beginning of diastolic mitral regurgitation did not change, while the duration of diastolic mitral regurgitation was shortened from 0.15 ± 0.03 to 0.05 ± 0.03 seconds (P < 0.01). There was a significant correlation between changes in PQ interval and changes in the duration of diastolic mitral regurgifation (r = 0.92, P < 0.001). Although cardiac output (3.9 ± 0.05 L/min) and pulmonary capillary wedge pressure (5.1 ± 1.5 mmHg) were normal in all patients with pacemakers, diastolic mitral regurgitation was observed when the AV delay was prolonged. The critical PQ interval for the appearance of diastolic mitral regurgitation was 0.23 ± 0.01 seconds. In patients with prolonged PQ intervals, delayed ventricular contraction following atrial contraction may be associated with mitral regurgitation in the presence of a reversed AV pressure gradient. The results of this study suggest that diastolic mitral regurgitation occurs not only in patients with DDD pacemakers, but also with AAIR pacemakers when the PQ interval is prolonged. The occurrence of diastolic mitral regurgitation is associated with the pacing mode or the setting of AV delay.
Orthostatic Responses in Patients with ODD Pacemakers: Signs of Autonomic Dysfunction
Authors: OVSYSHCHER ILYA , GROSS JAY N. , BLUMBERG STEPHEN , FURMAN SEYMOUR
Published: July 2006

Responses to orthostasis may be altered in states associated with autonomic dysfunction. Computerized impedance cardiography, a noninvasive method for continuous assessment of stroke volume and mean blood pressure, was utilized to study the postural hemodynamic changes in eight normal and 27 patients with DDD pacemakers. Twenty patients with complete heart block (five with heart failure) were studied in the VDD mode and seven patients with sick sinus syndrome were assessed in DVI (four] or VDD (three). The results with pacemaker patients are significantly different from those observed in normal. Pacemaker patient responses to standing included: (1) a reduction in systolic, diastolic, and mean blood pressure; (2) an increase in heart rate in patients with intact sinus node function and no change in patients with sick sinus syndrome; and (3) stroke volume was unchanged in patients with sick sinus syndrome or heart failure and only modest reduction occurred in the remaining patients. Conclusions: (1) No reduction in stroke volume during upright posture occurs in DDD patients with sick sinus syndrome and this appears to be a compensatory reaction to an inadequate heart rate response to standing; (2) The hemodynamic response of DDD patients to the assumption of an upright posture is consistent with autonomic dysfunction; and (3) The primary cause for autonomic dysfunction in DDD patients may be the asynchronous ventricular depolarization caused by right ventricular pacing.
Observations on Induction and Termination of Paroxysmal Supraventricular Tachycardia by External Pacing
Authors: GRUBB BLAIR P. , MARKEL MICHAEL L. , ARTMAN STEVEN E. , POST WILLIAM R. , LUCK JERRY C.
Published: July 2006

Paroxysmal Supraventricular tachycardia (PSVT) can be reproducibly induced and terminated by critically timed atrial or ventricular depolarizations. In this study, noninvasive trans‐cutaneous (external) cardiac pacing (NTCPJ was compared to endocardial ventricular pacing for the termination and induction of PSVT. In 24 patients, either atrioventricular (AV) nodal reentrant tachycardia or AV reciprocating tachycardia was reproducibly terminated with either critically timed ventricular depolarizations or overdrive ventricular pacing from an endocardial right ventricular site. There were 32 trials of NTCP attempts to interrupt PSVT in the 24 patients. External pacing was successful at terminating PSVT in 23 patients and in 30 of 32 (94%) trials. In 20 patients, there were 26 trials of external pacing attempts to induce PSVT. External pacing initiated PSVT in 21 of 26 trials (81%). The pacing sequences used to induce and terminate PSVT with external pacing were copied from the endocardial sequences. The external pacing threshold averaged 77 ± 22 mA but the current needed to terminate PSVT was about 1.5 greater than threshold at 117 ± 27 mA. Serial external pacing studies were performed in seven patients. The thresholds for external pacing were similar from trial to trial as were the mode of termination and induction between the endocardial and external methods. External pacing can terminate most AV reciprocating tachycardias and many AV nodal reentrant tachycardias. It appears promising as a means of inducing PSVT. However, the high stimulation amplitudes needed will prohibit wide acceptance of external pacing for induction and termination of PSVT.
Testing of Work Environments for Electromagnetic Interference
Authors: MARCO DAVID , EISINGER GEORGE , HAYES DAVID L.
Published: July 2006

A challenge for pacemaker therapists is whether a patient working in an environment with the potential for electromagnetic interference (EMI) can return to their work after a pacemaker has been implanted. Common practice has been to prohibit pacemaker patients from using electric welding machines. Twelve work environments and a new method for monitoring the pacemaker rhythm in the presence of EMI were tested. The new method uses a special memory called the event record found in several Siemens Pacesetter pacemaker models. Surface ECGs with a marking system, intracardiac electrograms, and a digital monitor were used to verify the results with event records. The results from several sources of EMI are reported. Twenty‐one in vivo and in vitro tests were performed in the work environments of 12 patients. Event records were useful and accurate both in vivo and in vitro. Electric arc welding machines up to 225 A did not affect these pacemakers. Arc welding machines using 1,000 A or more inhibited the in vitro test system within 1 or 2 meters of the weld or power generator. Electric welding machines with high frequency voltage superimposed on the welding current affected the pacemaker when it was within 2 meters of the power unit and 1 meter of the weld. Very large industrial degaussing coils affected pacemakers within 2 meters. The test method using event records was found to be an effective addition to monitoring the pacemaker. These results are specific for the pacemaker models tested. Such testing allows the physician to make a knowledgeable decision regarding return to work for the pacemaker patient in a high EMI environment.
Can the Heart be Chronically Paced with Electrodes on the Pericardial Surface?
Authors: SHEPARD R.B. , EPSTEIN A.E. , KAY G.N. , KIRKLIN J.K. , SLABAUGH J. , RENFROE D. , KEITH R. , PACIFICO A.D.
Published: July 2006

During implantable defibrillator (ICD) operations, we measured acute and chronic transpericardial bipolar pacing thresholds through standard myocardial surface electrodes sewn on the pericardium for chronic ICD QRS rate‐sensing use. We compared observations in 24 patients on day 0 with chronic measurements in seven patients at 27,4 ± 12.1 (median 31.7) months. The leads were used only for QRS rate‐sensing, not for pacing, during the time between acute and chronic measurements. Acute transpericardial pacing threshold at 0.5‐msec stimulus duration on day 0 was 4.5 ± 2.19 V (standard deviation), median 3.5 V, and at median time 964 days postimplantation was 3.8 ± 2.07 V, median 3.5 V. Mean acute pacing current threshold was 3.7 ± 1.90 mA, n = 23, and chronic was 2.7 ± 1.73 mA, n = 6. Acute bipolar impedance was 1,209 ± 383 ohms, median 1,138 ohms, and chronic was 1,550 ± 358 ohms, median 1,410 ohms, n = 7. Acute bipolar QRS amplitude was 12.3 ± 5.93 mV, median 12.1 mV, n = 24, and chronic was 13.5 ± 8.5 mV, median 17.2 mV, n = 7. None of the changes between the acute and chronic states was statistically significant, with the exception of bipolar impedance (P = 0.054). We concluded that: (1) transpericardial pacing threshold did not increase with time; (2) initial and chronic pacing impedances were high and current low; (3) QRS amplitudes were highly satisfactory for defibrillator rate‐sensing; and (4) this approach to ICD implantation left the surgically virgin heart unscarred to make future transplantation easier, and enhanced safety when previous cardiac operations had been done.
Cardiac Pacing in Neonates, Infants, and Preschool Children
Authors: GILLETTE PAUL C. , ZEIGLER VICKI L. , WINSLOW AMY T. , KRATZ JOHN M.
Published: July 2006

A series of 37 children < 5 years old at pacemaker implant were followed from 1 to 105 months. Five of 37 patients required reoperation for battery depletion while two required reoperation for exit block of epicardial ventricular leads. Each patient paced in the DDD or AAI mode was still in the original mode at the end of follow up.