bluuebunny/crossref_metadata_2025 huggingface dataset:
Ventricular Thrombosis During Permanent Endocardial Pacing in a Pediatric Patient with Hemorrheological Disorders
Authors: BASTIANON VITTORIA , MENICHELLI ADRIANA , COLLORIDI VINCENZO , CAPUTO VELIA , TRES JOLANDA , DEL PRINCIPE DOMENICO
Published: July 2006

Thrombosis in the right atrium or ventricle is a rare compli cation of permanent endocardial pacing in adults. To the best of our knowledge, this complication has not been previously reported at all in the pediatric age group. We report on a case of a 7‐year‐oId boy who had large left ventricular thrombi that occurred during permanent endocardial electrical stimulation. Subsequent pulmonary emboli complicated congestive heart failure in this patient. As a diagnostic approach, echocardiography and pulmonary perfusion scintigraphy were used. We comment on possible causes of this serious complication and suggest hemorrheological and platelet activation studies in patients with permanent endocardial pacing.
The Control of Atrial Contraction by Ventriculo‐Atrial Pacing in the Dog With AV Block
Authors: AIZAWA YOSHIFUSA , SCHER ALLEN M.
Published: July 2006

Atrial conlruction in dogs with atriuventncular (AV) block was controlled by multiple atrial stimuli delivered during ventricular diastole. Acute hemodynamic changes were assessed. At a ventricular rate of 60 bpm. the spontaneous atrial rate averaged 83, and atrial cannon waves were frequent, When the atria were given two stimuli at an interval of 500 ms during ventricular diastole, the cannon waves were eliminated completely, and a fall in mean central venous pressure and a rise in systemic blood pressure were found. At a pacing rate of 90 bpm, similar changes in the cannon waves, mean central venous pressure, and systemic blood pressure were found when two atrial sfimuli followed ventricular stimu lation. Ventriculo‐atrial multiple pacing may be useful in both clinical and experimental AV block.
Surgical Removal of Entrapped Endocardial Leads Without Using Extracorporeal Circulation*
Authors: DUBERNET JUAN , IRARRÁZAVAL MANUEL J. , LEMA GUILLERMO , MATURANA GUSTAVO , URZÚA JORGE , MORÁN SERGIO , NAVARRO MIGUEL , FAJURI ALEJANDRO
Published: July 2006

Of 267 patients having a tined endocardial lead implanted from 1978 to December 1983, three (1.1%) developed pulse generator pocket infection. Proper treatment of this complication involves removal of the pulse generator, continued external pacing via the implanted lead, pocket drainage and administration of specific antibiotics until the infected area clears. In two patients, the electrode could not be removed by traction. A sternotomy was performed, the pericardium was opened, the endocardial electrode was located by palpation, and a purse string suture (PSS) was prepared around it on the right ventricular wall. A new myocardial electrode with its corresponding generator was then implanted to reestablish pacing. Through the PSS the myocardium was incised, the distal end of the endocardial lead was exteriorized and severed, and the PSS was tied. The remaining lead was withdrawn proximally and the surgical wounds were closed. The results of this procedure have been been excellent, allowing the removal of the entrapped leads, with continuous pacing and without the need for extracorporeal cir culation.
Dual Chamber Pacemakers: Upper Rate Behavior
Authors: FURMAN SEYMOUR
Published: July 2006

Upper rate management of a dual chamber pacemaker requires sensing of the atrium and Jimitufion of ventricular response to desired levels. Lim iiation of ventricular rate response is accompJished by setting atriai channel refractoriness which consists of two separate and continuous intervals, the atrioventricular interval (AV interval) and the atrial re fractory interval, after the ventricular pace or sense event (AR interval). A P‐wave that falls within the total atrial refractory interval (TARI) remains unsensed and one that falls beyond the TARI is sensed. If the upper rate limit interval (URI) is programmed to equal the TARI, the upper rate limit will occur by development of sudden AV block. If the URI is of greater duration (lower allowed rate) than the TARI, the difference in interval between the two is the Wenckebach interval (WI) and is the duration of a response plaleau, when the atrial coupling interval is less than the upper rate interval. All dual chamber timing cycles can be interpreted in terms of atrial refractoriness and upper rate limitation with consid eration of the lower rate interval, and the ventricular refractory and blanking intervals.
Unusual Presentation of DDD Pacemaker System Malfunction
Authors: STARK STEPHEN , FARSHIDI ARDESHIR , HAGER W. DAVID , DONALDSON MAGRUDER C.
Published: July 2006

A DDD pacemaker utilizing an atrial J electrode was implanted in a patient whose right atrial appendage had been removed 7 years prior during aortic valve replacement. Alternating QRS morphologies produced by pacemaker stimulus artifacts occurred as a consequence of atrial lead dislodgement. The screw‐in atrial electrode has superior stability in patients with right atrial appendage removal; stability of the atrial J electrode cannot be obtained in such cases.
Unexpected Coexistence of Supraventricular and Ventricular Tachycardia in Patients with Syncope
Authors: EZRI MARILYN D. , JACOBS LORETTA G. , DENES PABLO
Published: July 2006

The incidence of multiple, inducible sustained arrhythmias during electrophysiologic studies is unknown. We have identified five patients who had several sustained tachycardias, some of which were not previously recognized clinically. Three patients had documented sustained supraventricular tachycardia (one of these also had nonsustained ventricular tachycardia) and two had documented sustained ventricular tachycardia. The clinically documented tachycardia was successfully reproduced in all cases; however, the three cases of supraventricular tachycardia also had sustained ventricular tachycardia initiated, and the two cases of ventricular tachycardia also had sustained supraventricular tachycardia, which had not previously been seen. The underlying common denominators for all five patients were poor left ventricular function due to ischemic heart disease and a history of syncope. In one case of clinical supraventricular tachycardia, the second sustained tachycardia appeared following drug therapy (procainamide), which seemed to convert nonsustained to sustained ventricular tachycardia. In another patient with clinical ventricular tachycardia, the supraventricular tachycardia was also initiated following drug therapy (indecainide). We conclude that: (1) patients with syncope may have multiple arrhythmic etiologies and (2) complete electrophysiologic evaluation, during control studies as well as serial drug studies, are important in the management of these patienls.
Electrophysiologic Study of Tachycardia‐Dependent Paroxysmal His Bundle Block in Man
Authors: LITTMANN LÁSZLÓ , TENCZER JÓZSEF , FENYVESI TAMÁS
Published: July 2006

Electrophysiologic sludy was performed in a potienl with tachycardia‐dependent paroxysmal atrioventricular block. The site of block was within the His bundle. The effective refractory period of the His bundle was markedly prolonged and it was comparable to the critical atrial cycle length producing type II His bundle block. The most likely mechanism of paroxysmal atrioventricular block was repetitive concealed penetration of the blocking zone by nonconducted impulses that reached the proximal His bundle. Enhancing the blocking ratio at the atrioventricular nodal level resulted in improvement of overall atrioventricular conduction.
Mixed Carotid Sinus Hypersensitivity: Successful Therapy with Pacing, Ephedrine, and Propranolol
Authors: KEATING EDWARD C. , BURKS JOHN M. , CALDER JOSEPH R.
Published: July 2006

Three forms of carotid sinus hypersensitivity are recognized clinically (cardio‐inhibitory, vasodepressor, and mixed). The cardio‐inhibitory form has been managed successfully with pacemaker therapy. The vasodepressor element has been difficult to manage clinically whether in its pure form or in combination with the cardio‐inhibitory type. We review the various pharmacologic methods previously reported and present our experience with a new pharmacologic alternative, which is the combined use of ephedrine and propranolol to induce unopposed alpha stimulation.
Rate‐Responsive Ventricular Pacing: Clinical Experience With the RS4‐SRT Pacing System
Authors: RAMSDALE DAVID R. , CHARLES RICHARD G.
Published: July 2006

Eighteen patients (11 men and 7 women) with symptomatic second or third degree atrioventricular block underwent implantation of the rate‐responsive RS4‐SRT pacing system. Exercise tolerance in RS4 mode was compared to that in VVI mode by randomized double‐blind treadmill stress testing. Following hospital discharge, HS4 function was assessed by repeat exercise testing and 24‐hour Holter monitoring. Difficulty in obtaining satisfactory P‐wave amplitudes at implonfation (mean 3.1 ±1.5 mV) resulted in prolonged implantation times (mean 79.4 ± 26.4 minutes). Following implantation, 10 patients (58%) showed a significant ventricular rate response to exercise, seven did not, and one remained in sinus rhythm. For responders, peak ventricular paced rate and double product were significantly greater in RS4 than in VVI mode, being 101.8 ± 5.8 vs. 74.3 ± 0.4 beats per minute and 20.1 ± 2.9 vs. 15.5 ± 3.7 beats per minute ± mmHg ± 10−3, respectively (p < 0.001). However, treadmill times (10.5 ± 2.6 vs. 9.7 ± 3.3 minutes) and work done (5.51 ± 2.01 vs. 4.97 ± 2.33 joules ± 10−5) were not significantly different (p = 0.22). Following hospital discharge, repeat exercise testing and 24‐hour Holter monitoring demonstrated RS4 junction in 11 of 16 and 15 of 18 patients, respectively. We conclude that, due to unreliable atrial sensing, the RS4‐SRT pacing system does not provide the reliable rate‐responsiveness required to improve exercise tolerance.
Reappearance of Persistent Normal Sinus Rhythm in a Patient with the Sick Sinus Syndrome Following Cardiac Pacing for 10.5 Years
Authors: CHEN HAOZHU , JIANG SHENYANG , PU SHOUYUE , SHIH MEIXIN
Published: July 2006

A patient with symptomatic sick sinus syndrome which manifested as a brady‐tachy syndrome, was admitted to our institute in 1969. Following cardiac pacing for 10.5 years, the brady‐tachy syndrome disappeared and normal sinus rhythm was restored. Her stable normal sinus rate has persisted up to the present, 2.5 years after termination of pacing.
Radionuclide Evaluation of Dual Chamber Pacing: Comparison Between Variable AV Intervals and Ventricular Pacing
Authors: LEMAN ROBERT B. , KRATZ JOHN M.
Published: July 2006

We prospectively evaluated changes in left ventricular ejection fraction, end diastolic volume, and stroke volume via radionuclide multigated acquisition study, Comparison was made between ventricular pacing and dual chamber pacing with varying AV intervals. The volumes and changes in ejection fraction were determined at rest, at set increased pacing rates, and during physiological stress. AV sequential pacing shows overall improvement in cardiac function in the majority of patients regardless of left ventricular function. The shorter AV interval would be appropriate for the majority of patients who have an atrial tracking mechanism (adequate intrinsic sensed atrial activity followed by ventricular pacing) and who undergo significant physiological stress.
Artificial Circus Movement Tachycardias: Incidence, Mechanisms, and Prevention
Authors: BERTHOLET MICHEL , MATERNE PIERRE , DUBOIS CHRISTOPHE , MARCELLE PHILIPPE , BECKERS JACQUES , DEMOULIN JEAN‐CLAUDE , FOURNY JACQUES , KULBERTUS HENRI E.
Published: July 2006

In a group of 45 patients treated with Medtronic 7000 and 7100 pulse generators for sick sinus syndrome or second or third degree atrioventricular block, an atrial synchronous mode of pacing was programmed in 34 cases and spontaneously occurring artificial circus movement tachycardios (ACMTs) were observed in nine. An analysis of conditions of occurrence, triggering mechanisms and patterns of ACMT, is presented. Various modalilies of prevention are discussed. They resulted in suppression of ACMT in five patients and decrease of incidence in a sixth; the three remaining subjects were managed by definitive reprogramming in the DVI mode. Our conclusion is that correct prevention of ACMT requires the use of dual chamber pulse generators with programmable atrial refractory periods. For patients in whom a unit has already been implanted, careful observation of the triggering mechanism and pattern of ACMT may help in determining the most suitable way to prevent and suppress the arrhythmia.
Pacemaker‐Mediated Tachycardia Initiated by Coincident P‐Wave Undersensing and Ventricular Blanking Period
Authors: LAMAS GERVASIO A. , ANTMAN ELLIOTT M.
Published: July 2006

Pacemaker‐mediated tachycardias (PMT) have received much recent attention. We describe the course und treatmenf of a 60‐year‐old man with au AV universal (DDD) pacemaker who developed a pacemaker‐mediated tachycardia. The tachycardio was initiated by the coincidence of an unsensed P‐wave, a QRS that was also not sensed due to the ventricular blanking period, and a short right venfricular myocardiaJ effective refractory period. Treatment consisted of reprogramming the atrial sensitivity of the device. Physicians should be aware of the potential for the ventricular blanking period to participate in the initiation of pacemaker mediated tachycardias.
The Patent System and Cardiac Pacing: Is the System Serving Its Users?
Authors: PRESTON ALBERT W. , PRESTON THOMAS A.
Published: July 2006

Patents have been utilized to protect technical innovations in pacemakers virtually since their inception and are becoming increasingly important to the industry. In the U.S. alone, about 100 patents are granted each year covering pacer‐related technology and reflecting the main areas of technical development. The increase in the number of outstanding patents has been accompanied by a significant increase in patent litigation among pacer companies. The rate and cost of pacer‐related patent litigation raises a question of whether the system is being used to its best advantage. A recommendation is made for an industry‐sponsored board to aid in voluntary settlement of patent disputes.
Sine2/Triangle/Square Wave Generator for Pacemaker Testing
Authors: BIČÍK VLADIMÍR , KŘIš?AN LUDĚK
Published: July 2006

We describe a device which generates the most widely used test signals for sensitivity measurements of noncompetitive pacemakers—sine2, triangle and square waves. The test generator can operate in free‐running mode or it can be triggered by impulses from the pacemaker tested, thus enabling measurement of the sensitivity response of the pacemaker sensing circuits within the whole automatic interval, including determination of the pacemaker refractory period.
Late Infections of Pacemaker Units Due to Silicone Rubber Insulation Boots
Authors: BUCH JAN , MORTENSEN SVEND AAGE
Published: July 2006

Early in 1980, there was an increase at our hospital of late infections of pulse generator pockets not due to perforation. No source of contamination could be found; then, late in 1981, the infection rate decreased. The only change in procedure during this period was the introduction of silicone rubber boots around the pacemaker unit to prevent muscle pacing. The risk of late infection was 13.8%, when using a rubber boot, while otherwise it was only 2.6% (p < 0.001). The infections were usually caused by ordinary skin bacteria. The authors believe that the infections were due to bacteria introduced inside the rubber boot, where they were practically out of reach of the ordinary defense mechanisms. The decrease in infection rate occurred after the introduction of silicone‐coated pacemakers.
Transvenous Atrial Pacing following Amputation of the Atrial Appendage at Open Heart Surgery
Authors: KERR CHARLES R. , MASON MARCIA A. , TYERS G. ERANK O. , BURR LAWRENCE H. , JAMIESON W.R. ERIC
Published: July 2006

The right atrial appendage is frequently amputated at the time of open heart surgery. In this study we report implantation and chronic follow‐up pacing data on 17 patients in whom either actively fixated screw‐in leads or passively fixated tined “J” leads were implanted into the trabeculae at the base of the atrial appendage. Chronic follow‐up demonstrated excellent chronic pacing thresholds and atrial sensitivity thresholds in those patients in whom these measurements could be made. It is therefore concluded that satisfactory atrial pacing can be achieved in patients who have previously undergone amputation of the atrial appendage during open heart surgery.
Termination of Ventricular Tachycardia by an Implantable Atrial Pacemaker and External Pacemaker Activator
Authors: TANABE AKIHIRO , IKEDA HIDEO , FUJIYAMA MASUAKI , FURUTA YOH‐ICHIRO , MATSUMURA JUN , OHBAYASHI JUN , UTSU FUMIHIKO , TOSHIMA HIRONORI
Published: July 2006

An atrial pacemaker was implanted in a patient who had dilated cardiomyopathy, sinus node dysfunction, and drug‐resistant ventricular tachycardia (VT). VT episodes were terminated by atrial overdrive pacing using an implanted pacmaker and a newly developed handheld external programmer/transmitter. Although successful cases of termination of intractable VT by ventricular pacing have recently been reported, the ventricular method might increase the risk of accelerating VT. Atrial overdrive pacing is a safer method since it minimizes the possibility of tachycardia acceleration and, combined with antiarrhythmic drugs, it appeared to be a unique and useful approach for the treatment of drug‐resistant VT.
Predicted Early Failure of Cardiac Pacemakers
Authors: COLLINS D.W.K. , BLACK J. L. , SINCLAIR I. N.
Published: July 2006

This paper describes a study on pacemaker longevity carried out on 65 subjects using mostly the Telectronics model 171 and model 173 pacemakers and based on an analysis of pacing rate reduction as a function of time since implant. Three different modes of rundown were observed. The shortest predicted lifetime was 23 months for a model 171 unit. This study was undertaken after the manufacturer and battery companies clearly delineated the existence of the problem and steps to be taken in the follow‐up of patients. Careful analysis of medical records of the patients did not yield any correlation between sex, age, indications for implantation, initial pacing threshold, or amount of use of the pacemaker, and the early rundown of these pacemakers. Our study indicated that, in general, the model 173 had a shorter expected lifetime than the model 171. Using a reduction in pacing rate of 5.5 bpm from the rate at implant as the end‐of‐life indicator, the study showed that 16% of the model 173 pacemakers would need to be replaced within 3 years of implant and 78% within 6 years of implant. In the case of the model 171 units, 10% would need to be replaced within 3 years of implant and 48% within 6 years. Follow‐up of patients with these units should be scheduled to monitor closely the rate of rundown in order to predict replacement dates.
Wide QRS Supraventricular Tachycardia Due to Coexisting Mahaim and Kent Pathways
Authors: SETHI KAMAL K. , JAISHANKAR S. , GUPTA M. P.
Published: July 2006

In two patients with Wolff‐Parkinson‐White syndrome, we observed the unusual coexistence of functional Mahaim and accessory atrioventricular pathways. In the first patient, three types of reciprocating tachycardia were demonstrable: (1) anterograde conduction over the atrioventricular (AV) node with right bundle branch block (RBBB) and retrograde conduction via a right‐sided atrioventricular accessory pathway; (2) anterograde conduction through the AV node with RBBB and retrograde conduction via two (right‐sided and septal) anomalous pathways; and (3) anterograde conduction through nodoventricular fibers and retrograde conduction over a right‐sided accessory pathway. In the second patient the reentry circuit was comprised of AV node fasciculoventricular fiber in an anterograde direction and a right‐sided accessory pathway in a retrograde direction. We believe this to be the first report of triple accessory pathways, consisting of two atrioventricular and one nodoventricular connection, demonstrated by intracardiac electrophysiologic study.
Torsades de Pointes: A Rare Complication of Temporary Pacing for Permanent Ventricular Pacemaker Failure
Authors: JANOSIK DENISE , STRATMANN HENRY G. , WALTER KENNETH E. , KENNEDY HAROLD L.
Published: July 2006

Torsades de pointes, a dislinctive type of polymorphous ventricular lachycardia, may be induced by critically timed ventricular stimulation during electrophysiologic studies or, rarely, in patients with temporary or permanent ventricular pacemakers. The following case illustrates how, when temporary ventricular pacing is instituted to maintain heart rate in a patient with a defective permanent ventricular pacemaker, this potentially fatal arrhythmia may occur as a complication of interaction between the two pacemakers.
Examination of Explanted Polyurethane Pacemaker Leads Using the Scanning Electron Microscope
Authors: BEYERSDORF FRIEDHELM , KREUZER JOACHIM , SCHMIDTS LUDWIG , SATTER PETER
Published: July 2006

Since 1978, 2,365 polyurethane (PV) insulated cardiac pacing leads were implanted transvenously at our institution. To date, there have been no insulation failures in those leads. Thirtyseven PU leads were explanted, mainly for exit block, and 28 of these were investigated using the scanning electron microscope. We found a homogeneous distribution of surface changes in all lead segments in 56% of the 28 examined. These changes were more pronounced at the ligature site; severe surface cracking was noticed in 21%, with the deepest crack being 40 μm (average range of 10–15 μm). There appeared to be no time‐dependency of the surface changes as indicated by regression analysis (r = 0.32. p > 0.05). The ultimate severity and outcome of this degradation process in the leads reported in this study will only be known in the future after longer use. We conclude that excess stress must be avoided during the implantation procedure and that careful surveillance is necessary.
Computer Simulation of Dual Chamber Pacemaker Algorithms Using a Realistic Heart Model
Authors: MALIK MAREK , NATHAN ANTHONY , CAMM A. JOHN
Published: July 2006

Single and dual chamber pacing algorithms have been incorporated into a realistic computer model of cardiac electrical activation. The model enables different pacemaker algorithms to be tested, it allows prediction of their behavior, and it produces a simulated ECG record for each case. The computer model has been used to test eight different modifications of a simple DDD mode to prevent or terminate pacemaker‐mediated “endless loop” tachycardia: (1) constant prolongation of the atrial channel refractory period; (2) prolongation of the atrial refractory period after a ventricular premature heal (VPB); (3) atrial pacing synchronously with a VPB: (4) simple rate control; (5) rate control in which the VA counter is not reset: (6) no ventricular pacing after an atrial premature beat; (7) rate limitation of atrial sensing; and (8) a combination of DDD and high frequency atrial stimulation modes. These modifications were tested with VPBs, atrial premature beats, atrial stimulation without capture, and accelerating sinus tachycardia. Only the pacemaker designed not to pace the ventricles following an atrial premature beat behaves satisfactorily in all four circumstances. Further possibilities for the development and use of a pacemaker‐oriented computer heart model are discussed.
Cross‐Stimulation: The Unexpected Stimulation of the Unpaced Chamber
Authors: LEVINE PAUL A. , RIHANEK BRETTON D. , SANDERS RICHARD , SHOLDER JASON
Published: July 2006

The ability to stimulate one chamber through a lead or output circuit to the opposite cardiac chamber is termed cross‐stimulation. Three examples of this phenomenon are presented. The first involves the close proximity of the atrial lead to the ventricular myocardium with ventricular capture occurring at sufficiently high outputs; the second is due to the basic design of dual unipolar pacing systems which have output circuits that share a common anode; the third is a self‐limited eccentricity of one device that occurs only during the first phase of magnet‐induced asynchronous pacing. The mechanism and clinical significance of these observations are discussed.
Removal of Monofilamental and Multifilamental Temporary Pacing Leads Following Open‐Heart Surgery: Occurrence of Arrhythmias
Authors: HARJULA ARI , JÄRVINEN ANTERO , MATTILA SEVERI , HÄRTEL GOTTFRIED
Published: July 2006

This study compared multifilamental and monofilamental temporary pacing leads in a clinical series of 83 patients who underwent valve replacement or coronary artery bypass grafting. The leads were used in the bipolar mode and were implanted into the outer layers of the right ventricular myocardium. The force required for wire removal (newtons), and the arrhythmias which occurred during removal were monitored. During electrode removal, 48% of the patients had transient arrhythmias (46% with monofilamental and 51% with multifilamental leads). The most common was a single ventricular premature contraction. In one case, wire removal caused non‐sustained ventricular tachycardia. All the arrhythmias subsided spontaneously. There was no statistical difference between results of the two leads. The force needed for removal was monitored directly by applying force via a graduated spring; they were equal in both groups (2.6 newtons). Both electrode types behaved similarly during wire removal, and the spiral tail of the monofilamental lead did not provoke arrhythmias.
Examination of an Exponential Model of Conduction Through the Human Atrioventricular Node *
Authors: DORVEAUX LILIANE , HEDDLE WILLIAM , JONES MICHAEL , TONKIN ANDREW
Published: July 2006

The atrioventricular node (AVN) has been modeled by relating output (A2H2 or H1H2) to input (A1A2) where A and H are atrial and His bundle electrograms during fixed rate atrial pacing (A1A1) or with an extrastimulus (A2).

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This study examined this model in 61 nonselected patients, specifically for AVN (in)stability and the possibility of multiple pathways. After programmed atrial stimulation at two basic cycle lengths of 600 ms and 462 ms, A1H1, A2H2 and H1H2 were digitized and plotted as a function of A1A2, Seven of 104 trials were rejected as SD. A1H1 was >15 ms, suggesting AVN instability. Another 26 and 34 plots, respectively, of A2H2 and H1H2 were rejected because of inadequate data. In the remainder, goodness of fit of the single exponentials was tested statistically in three ways: R2, the runs test, and the Kendall rank coefficient test. Results were compared with an electrophysiologist who examined plots for one or more pathways (either discontinuous curves or slope change in a continuous curve). Single exponentials were successfully fitted (by runs test) in 44/71 and 34/63 of A2H2 and H1H2 plots, respectively, usually in accordance with the cardiologist. Discordance between computations and the cardiologist could be attributed to data scatter and lack of a sufficiently rigid stimulation protocol. The identification of bifurcation points in the presence of multiple pathways, particularly when manifest as a change in slope (approximately 6% of trials) rather than discontinuity of plots (approximately 20% of trials) remains an outstanding problem.
Antibiotic Prophylaxis in Pacemaker Surgery; A Prospective Trial With Local or Systemic Administration of Antibiotics at Generator Replacements
Authors: BLUHM GÖSTA , JACOBSON BENGT , RANSJÖ ULRIKA
Published: July 2006

To evaluate the effect of short‐term antibiotic prophylaxis at pacemaker surgery, consecutive patients scheduled for routine generator replacements were randomly assigned to a double blind study. One group received systemic prophylactic (SP) antibiotics and one group was given local prophylactic (LP) antibiotics. One‐hundred and eight patients entered the study, but three were subsequently excluded. The SP group received flucloxacillin 2 gm intravenously 1 hour before surgery, then 1 gm orally every 8 hours for the following 5 days. In the LP group, 10 ml of a dextran emulsion with 5% cloxacillin was instilled in the generator pocket at the end of the operation. Infection developed in 0/53 in the SP group and 2/52 in the LP group. Tissue fluid was drawn 24 hours postoperatively from the generator pocket for determination of pocket concentration of antibiotics and culture tests. The concentration of flucloxacillin in tissue fluid from the pacemaker pocket 1 day postoperatively could be measured in 29 patients in the SP group with a median of 7.2 μg/ml. Median level of pocket fluid concentration of cloxacillin was 58.5 μg/ml in 31 patients in the LP group. Bacteriological cultures were positive in 1/32 patients in the SP group and in 1/33 in the LP group, but none of these patients developed infection. In conclusion, there was a low infection rate, both with systemic prophylaxis with flucloxacillin for a short period of time and with local prophylaxis with cloxacillin perioperatively.
Nonclinical Ventricular Tachycardia in the WolflF‐Parkinson‐White Syndrome
Authors: MILSTEIN SIMON , SHARMA ARJUN D. , KLEIN GEORGE J.
Published: July 2006

Between September 1980 and June 1984 we assessed the specificity of induction of ventricular tachycardia (VT) with one or two ventricular extrastimuli in a consecutive series of 148 patients undergoing electrophysioiogical assessment for the Wolff‐Parkinson‐White (WPW) syndrome by standard electrophysiological techniques. Fifteen patients (10%) had six or more beats of VT induced by one ventricular extrastimulus after a ventricular drive (9 patients), two ventricular extrastimuli during reciprocating tachycardia (6 patients), and during a single atrial extrastimulus (1 patient). None of the six men and nine women, aged 16–61 years, had apparent heart disease. VT lasted for 20 ± 14 (mean ± standard deviation) cycles with a cycle length of 235 ms ± 27 and was generally polymorphic. One patient had ventricular fibrillation. These patients were compared to 15 age‐ and sex‐matched patients studied in the same time period. There was no difference in anterograde elective refractory period of the accessory pathway (316 ± 92 vs 319 ± 68 ms), ventricular effective refractory period (2I8 ± 12 vs 227 ± 23), shortest pacing cycle length maintaining 1:1 anterograde conduction over the accessory pathway (306 ± 132 vs 320 ± 67) or minimum R‐R interval between preexcited beats during atrial flbrillation (280 ± 68 vs 294 ± 105). All patients are alive and well over a follow‐up interval of 20 ± 11 months on no antiarrhythmic therapy (13 patients) or on propranolol (2 patients). We conclude that a high percentage (10.1%) of WPW patients undergoing standard electrophysiological assessment have induction of nonclinical ventricular tachycardia with conservative ventricular extrastimulation techniques. The latter is a nonspecific finding in this patient group.
Pacemaker Electrocardiography of Rate Smoothing During DDD Pacing
Authors: VAN MECHELEN ROB , RUITER JAAP , DE BOER HANS , HAGEMEIJER FRANS
Published: July 2006

A rate smoothing opinion is available in a new bipolar AV universal (DDD) pacemaker. In three patients, two with intact retrograde conduction and one with retrograde block, rate smoothing values of 3% and 6% were programmed. Irregular pacemaker‐mediated tachycardia occurred in one patient and AV synchrony was temporarily lost in the other two patients. In this report, we describe the pacemaker electrocardiography of rate smoothing during DDD pacing.
Noise Mode Response at Peak Exercise in a DDD Pacemaker
Authors: SUDDUTH BONNIE K. , MORRIS D. LYNN , GERTZ EDWARD W.
Published: July 2006

The noise sampling period has been recognized as a cause of apparent sensing malfunction in demand pacemakers. Physiologic signals as well as external electromagnetic interference can cause certain demand pacemakers to remain refractory and escape asynchronously at a specified rate. In this case, noise mode reversion pacing at the programmed lower rate limit of a Cordis 415A DDD pacemaker was observed during exercise when P‐waves fell within the noise sampling period.
Male Breast Cancer From Pacemaker Pocket
Authors: RASMUSSEN KNUT , GRIMSGAARD GHRISTIAN , VIK‐MO HARALD , STALSBERG HELGE
Published: July 2006

One yeor following implantation of a mercury zinc pulse generator under the right breast, a 75‐year‐old man developed an ulcerative tumor of the nipple. Initially, the process was misinterpreted as a pacemaker pocket infection, until a diagnosis of papillary adenocarcinoma was made. The patient died from generalized metastases. To our knowledge, the association of a pacemaker implant and male breast cancer has not been previously reported; the probability of this occurring by chance seems rather low.
Evaluation of Pacemaker Performance Using Computer Simulation
Authors: DASSEN WILLEM R.M. , DEN DULK KAREL , GORGELS ANTON P.M. , BRUGADA PEDRO , WELLENS HEIN J.J.
Published: July 2006

A description is given of a mathematical model of impulse conduction through the heart. The model can be used to evaluate the best pacing mode for the individual patient and to develop new pacemakers. This allows study of the influence of different parameters related to the behavior of the heart or pacemaker. Two examples using a model of a DDD pacemaker and two examples describing simulation of an antitachycardia pacing system are given to illustrate how the performance of pacemakers under different conditions can be simulated.
Changes in Q‐T and Q‐aT Intervals at Rest and During Exercise With Different Modes of Cardiac Pacing
Authors: HEDMAN ANDERS , NORDLANDER ROLF , PEHRSSON S. KENNETH
Published: July 2006

The influence of heart rate variation on the Q‐T and Q‐aT intervals (measured from the onset of the QRS to the end or the apex, respectively, of the T‐wave) was studied both at rest and during exercise using different modes of pacing. The studies were made on 21 patients with high‐degree atrioventricular block. In seven patients with programmable ventricular inhibited (VVI) pacemakers, an increase in pacing rate during rest produced significant shortening of both Q‐T and Q‐aT. During observations made at rest and during exercise in 14 patients with fixed rate VVI, atrial rate matched asynchronous (VVIm) or atrial triggered (VAT) pacing. Significant shortening of Q‐T and Q‐aT intervals occurred during exercise in all pacing modes, but was greatest with VVIm and VAT. The Q‐T and Q‐aT changes were almost parallel in all situations. For measurements made by two independent observers the coefficient of variation was lower for Q‐aT than for Q‐T (2.2 versus 2.5) and the correlation coefficient was higher (0.96 versus 0.93), indicating easier identification of Q‐aT than of Q‐T. This study indicated that changes in Q‐T and in Q‐aT are influenced by intrinsic factors in addition to the ventricular rate. Atrioventricular synchronization did not seem to influence these changes.
Survival and Follow‐up After Pacemaker Implantation: A Comparison of Patients With Sick Sinus Syndrome, Complete Heart Block, and Atrial Fibrillation
Authors: ALT ECKHARD , VÖLKER REINHARD , WIRTZFELD ALEXANDER , ULM KURT
Published: July 2006

.The number of patients receiving cardiac pacemakers for sick sinus syndrome (SSS) has increased considerably in recent years. The literature has suggested that patients with sick sinus syndrome have a shorter life expectancy with pacemaker therapy than patients with total heart block or atrial fibrillation. We studied the survival rate of 1,049 patients with complete heart block, 592 with sick sinus syndrome and 447 with atrial fibrillation. After 10 years we found a survival rate of 54.5% for patients paced for SSS, 34.4% for those with complete heart block, and 24.7% for those with atrial fibrillation (statistical significance: SSS—heart block: p < 0.05: SSS—atrial fibrillation: p < 0.01; heart block—atrial fibrillation: NS). Considering the calculated survival rates of a comparable normal population (i.e., 56.5%; 41.2%; 47.8%), ihe differences in survival expectancy are even more pronounced (SSS‐normal: NS; heart block‐normal p < 0.05; atrial fibrillation‐normal: p < 0.05). For patients with sick sinus syndrome, the life expectancy parallels that of the general population, while that of patients with complete heart block or atrial fibrillation have a life expectancy that is considerably lower.
Choice of the Optimum Pulse Duration for Precordial Cardiac Pacing: A Theoretical Study
Authors: GEDDES L.A. , BABBS C.F. , VOORHEES W.D. , FOSTER K.S. , ARONSON A.L.
Published: July 2006

In precordial pacing with skin‐surface electrodes, the goal is to excite the ventricles with minimal stiniuiation of overlying tissues. A theoretical analysis is presented to identify the relevant factors; the two most important are electrode location and pulse duration. Using the basic law of stimulalion, we developed a model which indicates that the optimum pulse duration for the closed‐chest pacing pulse is one that is long with respect to the membrane time constant of cardiac muscle. Current‐versus‐duration curves are presented for pacing and pain, based on experimentally obtained data. For pacing with minimum pain, the optimum stimulus duration was found to be about 10 ms.
Intracardiac Electrograms and Sensing Test Signals: Electrophysiological, Physical, and Technical Considerations
Authors: IRNICH WERNER
Published: July 2006

Until now. the characterization of intracardiac electrograms was carried out mainly in the frequency domain by which filtering and sensitivity testing was decidingly influenced. The typical structure of the intracardiac electrogram derived with unipolar electrodes that is normally responsible for synchronization can be explained theoretically by assuming two dipoles perpendicular to each other moving along with nn excitation wave. An abstraction of this typical structure yields, as a sensitivity test signal, an asymmetric triangle with a 4‐ms decay time and a 16‐ms rise time. A correlation of different test signals and real heart signals applied to 16 different pacemakers demonstrates that the proposed test signal is superior to all others known so far.
Pacing Failure Due to Flecainide Acetate
Authors: WALKER PAUL R. , PAPOUCHADO MARK , JAMES MICHAEL A. , CLARKE LEONARD M.
Published: July 2006

Flecainide acetate is a recently introduced, class 1 antiarrhythmic agent that is highly effective in the treatment of ventricular and atrioventricular/ nodal reentrant tuchycardias.1,2 Although both intravenous and orally administered flecainide are known to cause an increase in the pacing threshold,3 an abrupt and potentially lethal rise in threshold causing failure of a properly functioning, newly implanted pacing system has not to our knowledge been described. We report such a case to stress the need for caution when using this drug in elderly pacemaker patients.
Late Purulent Pacemaker Pocket Infection Caused by Staphylococcus Epidermidis: Serious Complications of In Situ Management
Authors: RUITER JACOB H. , DEGENER JOHN E. , VAN MECHELEN ROB , BOS ROB
Published: July 2006

The pathophysiology of late pacemaker pocket infection is poorly understood. We report three cases of late infection caused by Staphylococcus epidermidis. Despite initial local conservative management ultimate removal of the entire pacing system was required. In late pacemaker pocket infection we recommend initial removal of the entire pacing system and replacement on the contralateral side. When retrieval of the lead system requires open‐heart surgery epicardial wires should be placed.
Sensing Characteristics of Unipolar and Bipolar Orthogonal Floating Atrial Electrodes: Morphology and Spectral Analysis
Authors: AUBERT ANDRÉ E. , ECTOR HUGO , DENYS BART G. , DE GEEST HILAIRE
Published: July 2006

We investigated wave morphology and spectral energy distributions of signals picked up by floating atrial unipolar and bipolar orthogonal sensing electrodes. Our data show that atrial P and QRS waves from unipolar floating electrodes are comparable. On the other hand, atrial P and QRS waves from bipolar orthogonal floating electrodes are significantly different. Even at high and mid right atrial locations, QRS waves are either absent or much smaller in amplitude and lower in frequency content than P waves. We conclude that the bipolar orthogonal floating atrial electrode is superior to the unipolar one for sensing due to its P to QRS wave discriminating power, which makes complex input filters or algorithms unnecessary. Our data support the idea that physiologic pacing with a VDD or VAT pacemaker is possible using a single pass lead.
The Effects of Magnetic Resonance Imaging on Implantable Pulse Generators
Authors: HOLMES DAVID R. , HAYES DAVID L. , GRAY JOEL E. , MERIDETH JOHN
Published: July 2006

The efects of magnetic resonance imaging were assessed on four dual chamber and two single chamber pulse generators. The tests were performed with a resistive, water‐cooled magnet operating at 0.15 T. The 6.4‐MHz radiofrequency (RF) field was operated at a maximum power of 1,000 watts with a period adjusted from 130 to 500 ms. Reed switch closure occurred in all six pulse generators tested when placed near the entrance of the magnetic resonance imaging scanner, and the generators reverted to asynchronous operation unless programmed to the “magnet of” mode. None of the pulse generators exhibited any alterations in programmed parameters or in the ability to be reprogrammed after RF pulsing. When the HF field was turned on, there was no change in the asynchronous paced cycle length in four pulse generators; however, during RF scanning there was rapid cardiac stimulation at the RF pulse period in one single chamber and one dual chamber pulse generator.
Transtelephonic Monitoring of 25,919 Implanted Pacemakers
Authors: DREIFUS LEONARD S. , ZINBERG ALLAN , HURZELER PHILIP , PUZIAK ALEXANDER D. , PENNOCK RONALD , FELDMAN MICHAEL , MORSE DRYDEN P.
Published: July 2006

In order to evaluate the behavior of lithium‐powered cardiac pacemakers, a database 25,919 lithium‐powered pacing systems including 23,517 single and 2,402 dual chambered pacemaker generators were followed in 21,750 patients. Of this group, 11,319 were currently active in addition to 7,560 who died, as well as 2,871 patients who terminated their follow‐up service prior to the end‐of‐life of the pacemaker system. A total of 23,517 single chambered pacemakers were followed for 719,173 months of pacing. The mean time to explant for generator malfunctions was 42 months and for all pacing system malfunctions it was 38 months compared to 31.9 months and 28.6 months, respectively, for the 2,402 dual chambered units that were observed for 38,718 months. In the single chambered units, the most frequent reason for explant was battery exhaustion (37% of explants) followed by lead problems (26%) compared to 49% and 12%, respectively, for the dual chambered units. The incidence rates, defined as a transtelephonic test result, required physician decision for action or clarification of the pacing mode or program parameters and showed a high incidence rate immediately post‐implant; thereafter, there was a relatively trauble‐free period until the 36th month when capture, sensing, and battery problems began to occur at a steady rate reaching 4% at the end of 48 months. Similarly, for dual chambered units, an 8% incidence rate was seen within the first 3 months, followed by a quiescent period until the 28th month when the incidence rate jumped to 16%. An analysis of 28 series of pacemakers, manufactured by 10 different pacemaker companies in which projected longevity data was available, indicated that an average of only 63% of the projected longevity of the units was realized for single chambered pacemakers. It is concluded that the actual longevity of single chambered units is less than the projected one originally stated and the present data derived from cumulative survival of dual chambered pacemakers does not suggest a brighter outlook, but rather portends an even higher frequency of pacemaker incidence and failure rate.
Spontaneous Endless Loop Tachycardia
Authors: OSERAN DANIEL , AUSUBEL KALMAN , KLEMENTOWICZ PETER T. , FURMAN SEYMOUR
Published: July 2006

Pacemaker‐mediated endless loop tachicardia is usually caused by a P wave displaced from the physiologic position preceding a QRS complex to a time of atrial channel sensitivity after the QRS. Five cases are described of endless loop tachycardia starting after a normally‐timed P wave, either spontaneous and preceding a ventricular stimulus or a P wave produced by an atrial channel stimulus followed by a ventricular stimulus and QRS complex. In each instance, the atrial refractory interval (ARI) was shorter than the retrograde conduction time. In four of the cases, prolongation of the atrial refractory interval after the ventricular event ended the tachycardias. In the fifth, in which the pulse generator could not be so programmed, the ventricular inhibited mode was required.
Pacemaker Follow‐Up: Its Role in the Detection and Correction of Pacemaker System Malfunction
Authors: GRIFFIN JERRY C. , SCHUENEMEYER TERRY D. , HESS KENNETH R. , GLAESER DON , ANDERSON BARBARA J. , ROMANS ELLEN , JENKINS MARY A. , NIELSEN ANTON P.
Published: July 2006

The goal of pacemaker follow‐up is not only to detect battery depletion but also to detect all malfunctions of the pacing system and, when possible, to correct such problems using programming. During one year, we discovered 61 such infunctions in a clinic of 1065 patients (5.7%). These were more frequent in the first year (7.7%) than in the third to fifth years of follow‐up (range 3.1–4.8%). The incidence rose again in the sixth and subsequent years (7–7.7%). Despite a significant occurrence of malfunctions (5.2%)among multiprogrammable pacemakers, the necessity for operative intervention for their correction was low (1.2%). Sensing problems were the most common (57%) and the most likely to be corrected hy reprogromming (85%); problems involving loss of capture were less likely to be corrected by programming (38.5%). Battery depletion accounted for only 18% of malfunctions, occurring earliest in the forty‐third month of follow‐up. Pulse generator longevity of those devices reaching end of battery life during the study period was 68.6 ± 16.7 months (mean + SD). We conclude that specialized pacemaker follow‐up continues to be necessary despite improved pulse generator reliability and longevity. Indeed, with reprogramming, it presently plays an even more important role than in the past. Follow‐up should he oriented not only to the detection of battery depletion but also toward o comprehensive surveillance of pacemaker system function.
Computer‐Assisted Measurements in Pacemaker Follow‐Up
Authors: BERNSTEIN ALAN D. , PARSONNET VICTOR
Published: July 2006

The application of increasingly sophisticated engineering techniques to cardiac pacemaker design has resulted in substantially greater complexity of follow‐up which requires that more complicated measurements be made and interpreted. A feasibility study was conducted in which microcomputer software was designed to permit direct electronic communication between the computer and a commercial follow‐up measurement device. This technique eliminates human error in reading or copying measurement data, and facilitates the application of computerized error‐trapping, predictive interpretation of measurements, and databasemanagement methods to pacemaker follow‐up.