bluuebunny/crossref_metadata_2025 huggingface dataset:
Antiarrhythmic Effects of VVI Pacing at Physiologic Rates: A Crossover Controlled Evaluation
Authors: FISHER JOHN D. , TEICHMAN SAM L. , EERRICK AILEEN , KIM SOO G. , WASPE LAWRENCE E. , MARTINEZ MARTA R.
Published: July 2006

Ventricular pacing can prevent bradycardia‐dependent ventricular ectopic activity (VEA) and is helpful in some cases of drug‐refractory venfricuiar tachycardia (VT). This study is a prospective evaluation of VVI pacing for the control of VEA not related to underlying bradycardia, drug side‐effects, or prolonged QT interval syndromes. Twenty‐nine patients undergoing serial electrophysioiogic‐pharmacoiogic testing for VT control were studied. Eighteen of these patients (12 men; meon age = 60.1) both completed ihe protocol and had sufficient VEA for analysis. Coronary disease was present in 13 patients, cardiomyopathy in two patients, and one patient each had myocarditis, mitral valve prolapse, and no structural heart disease. Ambulatory (Holter) monitor recordings during VVI pacing were compared with control recordings made in the absence of pacing, VVI pacing rates were 10–15 bpm above the mean daily heart rate (mean = 92 bpm; range = 63–110). Hours from paced recordings were paired with hours from control (prior to analysis) according to time of day to reduce the effects of spontaneous variability in VEA frequency. Overall, VVI pacing reduced ventricular premature complexes (VPGs) 26% from 331 to 245/hour (p < 0.001). During pacing, couplets (pairs, successive VPGs) were reduced from 6.95 to 1.03/hour (p < 0.000001) and VT (≥3 successive VPCs) from 0.89 to 0.045 episodes/hour (p < 0.003). Of 13 patients with couplets, 11 had ≥50% reduction and five had ≥90% reduction. Baseline VT was eliminated in four out of nine patients during pacing. Pacing did not increase VEA significantly in any patient. In this group of patients, reduction of VEA by VVI pacing was significant and was comparable to pharmacologic interventions. Higher forms of VEA fcouplets and VT) appeared to respond better than single VPCs. Further studies may define patients with VEA who can benefit from pacing
Computer Modeling of DDD Pacemakers for Use in Prophylaxis of Junctional Reentry Tachycardia
Authors: MALIK MAREK , DAVIES D. WYN , CAMM A. JOHN
Published: July 2006

A computer simulation model of cardiac rhythm and heart‐pacemaker interactions has been used to examine the response of short AV delay DDD pacing to an atrial premature depolarization in patients with a potential junctional reentry circuit. Special attention was given to the possibility of using the pacemaker to prevent atrioventricular reentry tachycardia mediated by a bidirectional accessory pathway. The computational experiments examined: (a) the differences between pacing modes with constant and quasi‐Wenckebach prolongation of AV delay; (b) the effects of imposing therestrictions of a pacemaker atrial refractory period and upper rate limit; and (c) the effects of varying the ventricular refractory period so that it was either the same or longer than that of the atria. The computational results prove that some possible modes of initiation of functional reentry tachycardia are beyond theprophylactic capabilities of current DDD pacemakers. Future possibilities involving theuse of computer modeling to develop more sopbisticated pacemaker modes are briefly discussed.
Extension of Life‐Table Methodology to Allow for Left‐Censoring in Survival Studies of Pacing Devices Followed by Commercial Monitoring Services
Authors: BROSTE STEVEN K. , KIM JOHN S.
Published: July 2006

The actuarial life‐table is commonly used to describe lifetime data of living subjects and manufactured products. The life‐table method allows subjects to come under observation at different times and, thus, to have differing lengths of follow‐up, by assuming all subjects begin their lifetimes relative to the outcome of interest at some common point in time. As time progresses, subjects are withdrawn from the life‐table when their period of observation has elapsed. This pattern of follow‐up is often termed “right‐censoring.” An important feature of the classical life table approach is that the time at which the subject is placed at risk is known, and the status relative to the outcome of interest is known for the entire time at risk. Sometimes, however, subjects cannot be observed for some period after the beginning of their lifetimes. The example to be considered involves follow‐up data collected by a commercial pacemaker monitoring service, to which patients subscribe, generally at some point following the actual implant of the pacemaker. Since the outcome of interest is device failure after implant, some means of dealing with the lack of information between implant and initiation of follow‐up is needed. The extension of the actuarial life‐table to accommodate this “left‐censoring” will be described in this paper.
Right Ventricular Volumetry by Catheter Measurement of Conductance
Authors: WOODARD JOHN C. , BERTRAM CHRISTOPHER D. , GOW BARRY S.
Published: July 2006

The electrical conductivity of blood is sufficiently higher than that of myocardium to make feasible the detection of cardiac volume changes hy measurement of intraventricuiar fluid conductance. An eight‐electrode catheter was used to inject an aiternating current (100 μA or less, at 1500 Hz) via the two electrodes nearest the ventricular base and apex, then the resulting five voltage differences between adjacent pairs of the six intervening electrodes were measured. When current amplitude was held constant, the cross‐sectional area of the ventricuiar cavity slice defined hy planes perpendicular to the catheter through the relevant pair of electrodes was inversely proportional (to the first order) to the voltage difference. Measurement of multiple segments compensated for isovolumic cavity shape changes. The technique had previously been shown to measure left ventricular volume successfully, but the geometry of the right ventricle made this measurement more problematical. Using open‐chested, anesthetized greyhounds, we compared the catheter‐measured right ventricuiar volume change with stroke volume as measured by a pulmonary arterial electromagnetic blood flowmeter. With optimal catheter placement, good correlation between stroke volume and catheter‐measured volume changes was achieved when stroke volume was perturbed on a heat‐to‐heat hasis. In six data records from three dogs, involving two different means of varying stroke volume (rapid injection of blood and sinus node irritation), the correlations yielded r2 values between 0.82 and 0.98. The method detected ineffective (nonejecting) beats associated with normal‐appearing QRS complexes and was thus a more reliable indicator of cardiac mechanical function than an eiectrocardiogram.
The Effect of Fascicular Block on Ventriculoatrial Conduction During AV Reentrant Tachycardia
Authors: KREMERS MARK S. , WHEELAN KEVIN R.
Published: July 2006

Two patients with Wolff‐Parkinson‐White syndrome and surgically mapped anterior left free wall atrioventricular bypass tracts had orthodromic atrioventricular reentry tachycardia conducted with complete left bundle branch block (CLBBB), complete right bundle branch block (CRBBB), left anterior fascicular block (LAFB), and a narrow QRS. Ventriculoatrial conduction increased by 35 and 85 ms with CLBBB compatible with the left free wall location of the bypass tracts. In one patient, resolution of CLBBB occurred in two stages. Initially, left posterior fascicular block (LPFB) resolved, decreasing VA conduction by 20 ms. With resolution of the remaining LAFB, there was a further 15 ms decrease in VA conduction. In the other patient, the isolated occurrence of LAFB increased ventriculoatrial conduction by 30 ms. These changes confirmed the location of the bypass tracts in the anterior portion of the left ventricular free wall. Changes in VA conduction with fascicular block can help localize the ventricular insertion of atrioventricuiar bypass tracts.
The Postcardiotomy Syndrome Following Transvenous Pacemaker Insertion
Authors: SNOW MATTHEW E. , AGATSTON ARTHUR S. , KRAMER H. COLEMAN , SAMET PHILIP
Published: July 2006

We describe a syndrome of fever, pericarditis, and symptomatic pericardial effusion beginning 2 months after transvenous insertion of a permanent pacemaker in a 75‐year‐old woman. The syndrome improved dramalicaily following pericardiocentesis and resolved after subsequent administration of indomethacin. Although right ventricuiar perforation during pacemaker insertion was not recognized, inadvertent perforation leading to the postcardiotomy syndrome is postulated.
Remote Occurrence of High Degree Heart Block Following Failure of Transcatheter AV Junctional Ablation: Incidence and Clinical Significance
Authors: BRU PAUL , LÉVY SAMUEL , METGE MARC , COINTE ROLAND , LACOMBE PIERRE , GÉRARD RAYMOND
Published: July 2006

We report on two patients out of a series of 22 who underwent transcatheter ablation of the atrioventricular (AV) junction. The procedure failed to induce permanent complete heart block in 15 patients, 12 of whom were in sinus rhythm with 1:1 AV conduction before hospital discharge. Of the 12 patients, two (16.6%) were found to be in high degree heart block, one month later. We discuss the mechanism of late occurrence of high degree heart block and we emphasize the need for systematic implantation of permanent ventricular or dual chamber pacemakers, despite failure of transcatheter ablation of the AV junction
Ease of Insertion of Exposed Helical Coil Tip and Tined Silicone Leads Through Single Cephalic Vein
Authors: GOREN CAROLYN C.
Published: July 2006

Since polyurethane was introduced as an insulation material for pacing leads, it has been purported that passing two polyurethane leads through one vein would be significantly easier than passing two bipolar silicone leads. However, this case, in which two bipolar silicone leads were easily positioned via a single cephalic vein, raises the question of whether there is any clinically significant in vivo lubricity difference between the two materials.
Inadvertent Transarterial Pacemaker Insertion: An Unusual Complication
Authors: LEPORE VINCENZO , PIZZARELLI GIAMPAOLO , DERNEVIK LEIF
Published: July 2006

We describe an unusual complication of pacemaker treatment in a patient who died after a replacement operation. In a difficult situation in which a functioning pacemaker was highly desirable and in which most of the available veins had already been used, the pacemaker electrode was inserted, by mistake, through a small artery. This was not detected by fluoroscopy during surgery. The postoperative X‐ray examination seemed to indicate that the electrode tip was located in the coronary sinus, but the subsequent autopsy revealed it to be located in the left ventricle.
Phenytoin in the Treatment of Inducible Ventricular Tachycardia: Results of Electrophysiologic Testing and Long‐Term FoUow‐Up
Authors: EPSTEIN ANDREW E. , PLUMB VANCE J. , HENTHORN RICHARD W. , WALDO ALBERT L.
Published: July 2006

Phenytoin treatment of inducible ventricular tachyarrhythmias was assessed by serial electrophysiologic studies (EPS) in 64 patients with spontaneous ventricular tachycardia, cardiac arrest, or symptoms compatible with a ventricular tachyarrhythmia. Coronary artery disease was the primary cardiac disease in 75% of the patients. All subjects had either inducible ventricular tachycardia (≥10 repetitive beats) or ventricular fibrillation at electrophysiologic study. Phenytoin was administered Intravenously in 38 studies and orally in 31 studies. The mean serum phenytoin level was 19.5 ± 4.7 mcg/ml. Only seven patients (11%) had a negative electrophysiologic study (≥10 repetitive beats) after the administration of phenytoin and were classified as phenytoin responders (group I). The remaining 54 patients (89%) were classified as nonresponders (group II). For the nonresponders. phenytoin increased the cycle length of identical monomurphic ventricular tachycardias from a mean of 301 ms to a mean of 327 ms(p < 0.001). For the four patients tested receiving both intravenous and oral phenytoin, the intravenous response always predicted the oral response. For the seven patients in whom electrophysiologic study indicated phenytoin efficacy, two are alive and arrhythmia‐event free, two had sudden death when the regimen was changed (one case, quinidine added; one case, subtherapeutic serum level), and three died from nonarrhythmic causes. For the 10 patients treated empirically with phenytoin, either alone (seven patients) or in combination with another antiarrhythmic agent (three patients), four died secondary to an arrhythmic event. These data indicate that: (1) phenytoin is infrequently an effective antiarrhythmic agent for the treatment of ventricular tachyarrhythmias as judged by response to electrophysiologic testing; (2) for phenytoin responders, when phenytoin is maintained at effective serum levels established during electrophysiologic testing, the incidence of subsequent arrhythmic events may be reduced; and (3) empiric use of phenytoin therapy for treatment of ventricular tachyarrhythmias is infrequently efficacious.
Neonatal Lupus with Congenital Atrioventricular Block and Myocarditis
Authors: BHARATI SAROJA , SWERDLOW MARTIN A. , VITULLO DOLORES , CHIEMMONGKOLTIP PIPIT , LEV MAURICE
Published: July 2006

This is a case of a child with neonatal lupus and congenital atrioventricuiar (AV) block, born to a mother with asymptomatic, systemic lupus erythematosus (SLE). The child, despite pacemaker insertion, died of septicemia and myocarditis at the age of three months. Although the association of neonatal lupus with congenital AV block is well‐recognized, there are only few pathologic studies of the conduction system reported in the literature. This is such a study in which we emphasize that, due to an altered immune system in the child, septicemia may be the cause of death in some cases.
Transesophageal Versus Intracardiac Atrial Stimulation in Assessing Electrophysiologic Parameters of the Sinus and AV Nodes and of the Atrial Myocardium
Authors: BLOMSTRÖM‐LUNDQVIST CARINA , EDVARDSSON NILS
Published: July 2006

Electrophysiological porameters of the sinus and AV nodes and of the atrial myocardium were assessed with both transesophageal atrial stimulation (TAS) and intracardiac atrial stimulation (ICS) in the same patient during the same study. The study group was comprised of nine men and seven women, aged 45 to 79 years, referred for the evaluation of syncope of possible arrhythmogenic origin. Twelve patients were included for analysis. Autonomic inhibition (AI) was obtained in five patients. The most striking result was the significantly longer AERP with TAS (mean 286 ± 9 ms) than with ICS (mean 244 ± 12 ms; p < 0.02). After AI, the AERP was even more prolonged with TAS (mean 332 ± 20 ms) than with ICS (mean 237 ± 8 ms; p < 0.01). Intraatrial and AV nodal conduction times assessed at multiple paced cycle lengths were significantly shorter with TAS than with ICS. There was no difference between TAS and ICS with regard to AVERP, Wenckebach periodicity and H‐V intervals. Although a tendency towards shorter sinus node recovery time (SNRT) and sinoatrial conduction time (SACT) was observed with TAS, the difference was not statistically significant. Possible mechanisms of the differences are discussed. It seemed clear that the site of origin of an atrial impulse can have definite effects upon excitability and conduction properties of atrial and AV nodal fibers. Enhanced sympathetic activity during TAS was also suggested. The electrophysiological properties inherent in the TAS technique warrant further elucidation.
The Feasibility of Beat‐to‐Beat Detection of His‐Purkinje Activity by Finite Element Method
Authors: ISHIJIMA MASA , KIMATA SHIN‐ICHI , KASANUKI HIROSHI , SAKURAI YASUHISA
Published: July 2006

A noninvasive method has been applied on human and canine subjects to observe beat‐to‐beat activity of the His‐Purkinje system without using signal averaging. Recordings were performed with multiple Ag/AgCI electrodes, very low noise, high gain amplifiers and by analog filtering. The subjects were in a supine position during the recording. In order to reduce random noise inherent in the high‐gain body surface recording, a finite element method (FEM) was applied to calculate His‐Purkinje activity. The dimensional relationship between electrode sites, necessary for the calculation, was pre‐estimated by x‐ray computed tomographs of the subject. A prominent waveform was observed between the atrial and ventricular complexes and corresponded to His bundle activity which was simultaneously recorded by an intracardiac electrode (on every beat). It was, however, difficult to recognize the His‐Purkinje activity during inhalation due to the thoracic electromyogram on some human subjects. This interference could theoretically be reduced by increasing the number of body surface electrodes used for this technique.
Intra‐Hisian Block Associated with Unusual Etiologies
Authors: SUN RUI‐LONG , WANG FANG‐ZHENG , HU SHENG‐JUN
Published: July 2006

One hundred and sixty‐nine patients underwent electrophysiologic study for atrioventricular block. Forty‐five (27%) had intra‐Hisian block. Four of these 45 patients had unusual etiologies: rheumatoid arthritis, cysticercosis cellulosae, Behcet's disease, and Takayasu aorto‐arteritis. Their clinical and electrophysiologic features are described in detail
Termination Of Sustained Tachycardia By External Noninvasive Pacing
Authors: LUCK JERRY C. , DAVIS DWIGHT
Published: July 2006

Invasive cardiac pacing has proved useful in the induction and termination of reentrant sustained tachycardias. In one of our two cases, programmed ventricular extrastimulation was used to induce sustained ventricular tachycardia from the endocardial surface of the right ventricle. Induced ventricular tachycardia was terminoted by burst ventricular pacing with an external cardiac pacemaker. In our second patient, external pacing was effective at inducing and terminating sustained supraventricular tachycardia. These patients illustrate that the principles of terminating sustained reentrant tachycardia with invasive pacing may also apply to noninvasive external pacing. The usefulness of this approach in treating reentrant tachycardias needs further evaluation.
A Prospective Evaluation of Single and Dual Current Pathways for Transvenous Cardioversion in Rapid Ventricular Tachycardia
Authors: SAKSENA SANJEEV , CALVO RICARDO A. , PANTOPOULOS DEMETRIS , GADHOKE ARUN , ROTHBART STEPHEN T.
Published: July 2006

By using a prospective randomized study design, we compared the clinical efficacy and safety of single unidirectional and bidirectional transvenous cardioversion shocks for termination of rapid ventricular tachycardia (VT) having cycle lengths < 300 ms. A Medtronic 6880 catheter was placed in the right ventricular apex and an R2 skin patch electrode was placed over the left scapula. Patients were randomized into two groups. Group A patients received unidirectional transvenous shocks using the two catheter electrodes (right ventricular apical cathode and superior vena caval anode) which resulted in a single current pathway. Group B patients received bidirectional transvenous shocks using a common cathode (right ventricular apex) and two separate anodes (superior vena caval and R2 patch) resulting in two current pathways. Identical shocks with total energies of 2.7, 5.0 and 10.0 J and waveform tilt of 27% were delivered to Groups A and B. In selected Group B patients, delivered shock currents through the right ventricular apex/superior vena caval and right ventricular apex/R2 patch electrode pairs were measured. We analyzed the initial episode of VT with a cycle length < 300 ms in 33 patients with organic heart disease (mean age, 64 ± 9 years; mean VT cycle length, 248 ± 37 ms) who underwent programmed electrical stimulation. Transvenous cardioversion shocks terminated 31% of 16 VT episodes in Group A and 41% of 17 VT episodes in Group B (p > .2). The mean successful shock energy was 6.1 ± 3.7 J in Group A and 3.0 ± 0.9 J in Group B (p < .05). Forty percent of all successfully cardioverted episodes in Group A and 86% of all successfully cardioverted VT episodes in Group B were terminated at an energy of 2.7 J (p = .09). Analysis of shock waveforms in Group B revealed 47 to 74% of the total current was transmitted through the right ventricular apex/superior vena caval electrodes and 26 to 53% through the right ventricular apex/R2 electrodes. We conclude that single bidirectional transvenous shocks are elective for rapid VT termination in selected patients. Dual current pathways decrease energies needed for successful transvenous cardioversion in this patient population.
The Effects of Extracorporeal Shock Wave Lithotripsy on Pacemaker Function
Authors: LANGBERG JONATHAN , ABBER JASON , THUROFF JOACHIM W. , GRIFFIN JERRY C.
Published: July 2006

Twenty‐two pacemaker pulse generators were exposed to shock waves of an extracorporeal shock wave lithotripter to assess the effects of the extremely high pressure transients on pacemaker function. The pulse generator and distal aspect of the lead were positioned 5 cm from the focal point of the lithotripter and 10 cm from each other. Pulse generator function was analyzed during shock wave delivery synchronized with pulse generator output, during shock waves at a rate faster than the escape rate, and after exposure to lithotripsy. During shock waves delivered synchronously with pulse generator output, only one of 22 pulse generators malfunctioned by intermittently reverting to the magnet rate. When subjected to shock waves at a rate greater than the escape rate, 50% of the pulse generators were inhibited by electromechanical interference from the lithotripter. Both bipolar and unipolar devices were affected. However, analysis after exposure to shock waves showed that none of the pacemakers was damaged or spuriously reprogrammed. In conclusion, cardiac pacemakers do not appear to be damaged or reprogrammed by exposure to extracorporeal shock wave lithotripsy. The likelihood of false inhibition appears to be very low if shock waves are delivered synchronously with the QRS.
Termination of Spontaneous Atrial Flutter by Transesophageal Pacing
Authors: CHUNG DAVID C. , KERR CHARLES R. , COOPER JOCELYN
Published: July 2006

Transesophageal atrial pacing using the constant‐rate technique was performed in 26 patients presenting with spontaneous atrial flutter (atrial cycle length between 180 and 270 ms). All but one patient had been treated with one or more antiarrhythmic agents (digoxin, quinidine, procainamide, propranolol, verapamil, diltiazem, and propafenone) within the previous 12 hours. Transesophageal atrial pacing at cycle lengths between 80 and 180 ms was successful in terminating atrial flutter in 22 patients: immediate reversion to sinus rhythm in 16, following transient sinus pause in one, following a brief period of atrial fibrillation in three, and following longer periods of atrial fibrillation in another two. No post‐conversion ventricular arrhythmia and no other complications were observed. All patients experienced only a mild burning discomfort during the procedure. It is concluded that atrial pacing via the esophagus is a safe and noninvasive technique of terminating spontaneous atrial flutter. The effectiveness of this technique is comparable to endocardial or epicardial atrial pacing.
Intermittent Fascicular Extrasystoles Producing Pseudo AV Block: Electrophysiologic Effects of Beta Agonists and Antagonists
Authors: NALOS PETER C. , MANDEL WILLIAM J. , GANG ELI S. , CAIN RICHARD P. , MASSUMI RASHID A. , PETER THOMAS
Published: July 2006

This report describes a pntient with pseudo‐type II second‐degree AV block due to an intermittent parasystolic focus located in the left bundle branch. A paradoxical increase in the fascicular rate was seen following intravenous propranolol, and fascicular extrasystoles were suppressed after intravenous isoproterenol treatment. All propagated fascicular extrasystoles were conducted to the ventricle with incomplete or complete right bundle branch block and a decrease in the H'‐V interval compared to the H‐V interval during sinus rhythm. Treatment with oral quinidine abolished fascicular extrasystoles without worsening of AV conduction.
A Special Outpatient Clinic for Following Patients with Implanted Tachyarrhythmia Devices
Authors: GALASSO DONNA , GALLAGHER RALPH , PARSONNET VICTOR , ROTHBART STEPHEN , CALVO RICARDO , SAKSENA SANJEEV
Published: July 2006

Implantable anti‐tachycardia devices have become an additional therapeutic option for those patients afflicted with life‐threatening tachyarrhythmias. Follow‐up of these complex devices are time‐consuming and, if mismanaged, may be dangerous to the patient. For these reasons, a special anti‐tachycardia device clinic was started at Newark Beth Israel Medical Center in July 1984. From the inception of the clinic to September 1985, 24 patients were followed. Seventy‐five percent had antitachycardia devices (ATDs) implanted for treatment of ventricular tachyarrhythmias (VT/VF) with the remaining 25% for supraventricular tachycardias. All patients were seen every 3 months or more often if clinically required. Of 112 ciinic examinations, 102 (91%) were scheduled appointments (group I) while the remaining 10 visits (group II) were unscheduled and preceded by symptomatic episodes. The problems detected in clinic (groups I and II) ranged from sudden failure of an AICD to apprehension. Appropriate nonoperative treatment was given during clinic evaluation for 60% of the problems detected in group II, while the remaining 40% required eventual surgical intervention. Compliance throughout the 15‐month follow‐up period was 100%. Major benefits of the clinic cited by patients and their families were continuity of care, the time allotted to meet the individual needs, and management of most problems on an out‐patient basis.
Posture‐Dependent Chronotropic Effect of Carotid Sinus Massage
Authors: MØLLER MOGENS , OXHØJ HENRIK , MICKLEY HANS , HANSEN KNUD NØRREGAARD
Published: July 2006

The hypertensive carptid sinus can be divided into cardioinhibitory (chronotropic) and vasodepressor components; the former can be evaluated by carotid sinus massage performed in the supine position. We present the case of a patient in whom the abnormal cardioinhibitory response could only be demonstrated while in the sitting position.
Automatic Implantable Cardioverter Defibrillator/Permanent Pacemaker Interaction: Loss of Pacemaker Capture Following AICD Discharge
Authors: SLEPIAN MARVIN , LEVINE JOSEPH H. , WATKINS LEVI , BRINKER JEFFREY , GUARNIERI THOMAS
Published: July 2006

A 78‐year‐old man treated with amiodaronce for recurrent ventricular tachycardia, had soquential placement of a bipolar VVI pacemaker and an automatic implantable cardioverter defibrillator (AICD). During defibrillation threshold testing, there was failure to capture of the pacer in the post‐shock period. The time of failure to capture appeared energy‐related: the greater the energy delivered, the longer the failure to capture. Careful attention will be necessary in constructing combined AICD/pacemaker units.
Effect of Antiarrhythmic Drugs on Defibrillation Threshold: Case Report of an Adverse Effect of Mexiletine and Review of the Literature
Authors: MARINCHAK ROGER A. , ERIEHLING TED D. , KLINE RUTH ANN , STOHLER JANE , KOWEY PETER R.
Published: July 2006

Antiarrhythmic agents can influence defibrillation threshold (DFT). Basic research suggests that some class I drugs may have deleterious ejects by raising defibrillation energy requirements. Evaluation of this problem in man has been limited to reports of patients who were more difficult to cardiovert or defibrillate after treatment with amiodarone and class IC agents. In the present report, mexiletine appeared to be the probable cause of an important elevation of DFT in a patient undergoing replacement of a malfunctioning automatic implantable cardioverter/defibrillator [AICD]. This report and the accompanying literature review suggest that more information at both the basic and clinical levels is required. Retesting of device efficacy in terminating induced arrhythmia in the laboratory appears prudent in patients who require antiarrhythmic drug therapy subsequent to AICD implantation.
The Value of Two‐Dimensional Echocardiography and Pulsed Doppler Technique in Facilitating Percutaneous Catheterization of the Suhclavian Vein
Authors: SWITZER DONALD F. , NANDA NAVIN C. , HARRIS PETER , BREEN WILLIAM
Published: July 2006

We have found combined two‐dimensional echocardiographic imaging and range‐galed pulsed Doppler flow mapping to he very useful and accurate in identifying the location and course of the subclavian vein. It can he efficiency utilized to minimize the incidence of iatrogenic complications during percutaneous central venous catheterization. This is particularly relevant in patients who are predisposed to a high risk of complications from the procedure.
Sino‐Atrial Dissociation: Evidence by Intracardiac Recordings in Man and by Microelectrode Studies on Isolated Rabbit Atrium
Authors: PISAPIA ANDRÉ , LEHEUZEY JEAN YVES , FAURE JACQUES , SIMONETTI BERNARD , SZATMARY LASZLO , CARTA MIREILLE , ROSARIO ROGER , BARNAY CLAUDE , DUPORT GUY
Published: July 2006

The electrophysiologic mechanisms of sinus dysfunction have recently been determined by direct recording of the sinus node electrogram. The association of various degrees of abnormalities in the formation of the impulse within the sinus node and of sinoatrial conduction block, represents the pathophysiological substrate of the mechanism of sinus node dysfunction. The purpose of this work is to present clinical and experimental data supporting the concept of sinus node isolation. In our clinical case, the sinus node was probably intact despite aspects of sinus node dysfunction on the surface ECG. Sinus node electrograms were recorded with a sinoatrial conduction time of 100 ms (normal values in our laboratory: 83 ms ± 38 ms). Atrial mapping demonstrated that (he area depolarized by the sinus node involved a 2 cm2 zone surrounding it. This perisinusal activity could not be recorded on the surface ECG. Both exit and entry blocks in the sinus node were demonstrated. Our experimental data showed a total desynchronization between the electrical activity of the sinus node and that of the atrium under hypoxic conditions. Both types of cases demonstrated that an atrial dysrhythmia was coexisting with regular sinus activity. From these data we concluded that a sinus node free from any pathological involvement could be associated with severe symptoms of sinus node dysfunction on the surface ECG.
Atrial Sensing Performance of AV Universal Pacemakers During Exercise
Authors: FRÖHLIG GERD , BLANK WALTER , SCHWERDT HOLGER , SEN SEMI , BETTE LUDWIG
Published: July 2006

To investigate the atrial sensing function of dual chamber pacemakers during exercise, we studied 57 patients aged 12 to 81 years (m = 65). They were paced for sinoatrial disorders (n = 15), second or third degree AV block (n = 37), or binodal disease (n = 11). The examination was performed 3‐24 months (m = 11) after pacemaker implantation. Individual sensing thresholds were determined at rest in the supine position, and proper detection of atrial signals at the programmed sensitivity level was verified during a period of 5‐9 minutes [m = 5.8]. Without a change in the program of the unit, symptom‐limited bicycle ergometry was performed at a maximum load of 25‐200 Watts [m = 95] and 6‐channeI chest wall electrocardiograms were continuously recorded throughout the test, including recovery. During exercise, 25/57 patients (44%) exhibited poor atrial sensing of the pulse generator; after termination of exercise in 16 of the 25 patients, proper atrial sensing resumed within 1 to 7 minutes of recovery. In the remaining nine cases, ergometry was continued after lowering the sensitivity threshold to half the initial setting or, depending on the pacemaker model, by a value of 0.4 mV. This resulted in normal function of the pulse generator in all patients but one, who needed a sensitivity adjustment of another 0.4 mV. In a subgroup of 25 patients, telemetric atrial electrogram recordings were monitored during ergometry, 19 of which could be evaluated quantitatively. Besides random atrial signal variations, presumably due to ectopic beats or runs, a systematic decrease of the peak‐to‐peak amplitude by 0.1 to 1.6 mV (3–30%) was observed in 16/19 patients during exercise. Mean signal reduction amounted to 11.8% and was statistically significant at the 0,1% level. It is concluded from these findings that, besides testing of atrial sensing at rest, the follow‐up of dual chamber pacemakers should include an exercise test.
Modulation of Atrioventricular Junctional Parasystole During Atrial Pacing
Authors: SCHWEITZER PAUL , STERN ERIC H.
Published: July 2006

In this report we describe a case of a 68‐year‐old man with atrioventricular junctional parasystole in whom atrial pacing caused marked changes in (he arrhythmic pattern. During afrial pacing at a cycle length of 960 ms, the duration of the ectopic cycle length was influenced by the inferval between the parasystolic and nonparasystoUc beat. A shorter interval from nonparasystolic to ectopic beat prolonged the ectopic cycle length and a longer one shortened it. Pacing at a cycle length of 900 ms completely suppressed the parasystole. Both of these changes are most likely due to modulation and entrainment of the parasystolic rhythm. During spontaneous variation of the sinus cycle length over 24 hours of ambulatory ECG recording, modulation could not be confirmed; however, there was parallel variation of the ectopic and sinus cycle lengths which suggests that both pacemakers were under the influence of the autonomic nervous system.
Programmed Stimulation after Anterior Myocardial Infarction Complicated by Bundle Branch Block—Late Ventricular Tachyarrhythmias and Outcome
Authors: TWIDALE NICHOLAS , TONKIN ANNE L. , TONKIN ANDREW M.
Published: July 2006

One hundred and thirty consecutive patients with anterior myocardial infarction complicated by bundle branch block were retrospectively analyzed. Sixty died within 1 week of infarction. Of the remaining 70 patients, 36 had electrophysiology study with programmed stimulation 8–90 (mean 20) days after infarction. Of these, nine patients (35%) who clinically had not manifested either ventricular tachycardia or ventricular fibrillation more than 72 hours after infarction, had inducible ventricular tachycardia which was sustained more than 30 seconds in eight patients. By contrast, assessment of atrioventricular conduction added little to clinical management, long‐term follow‐up, extending up to 127 months, was available both in those patients whose therapy was directed by electrophysiology study, and was assessed among the other 34 patients who survived at least 7 days after myocardial infarction, but who did not undergo electrophysiology study. While the overall mortality was 55%, the majority of deaths (22/35) occurred within 4 months of infarction and many long‐term survivors enjoy a gratifying quality of life. Although programmed stimulation in survivors of anterior myocardial infarction complicated by bundle branch block may identify a high risk subgroup, a prospective randomized trial is required to define the utility of more aggressive stimulation protocols following NASPE recommendations, to identify subgroups of patients in whom newer therapeutic interventions, including antiarrhythmic agents, electrical devices and surgery may be indicated.
Possible Proarrhythmic Effects of Tocainide in Dilated Cardiomyopathy
Authors: BROWNSTEIN SHELDON L. , CONSTANTIN LUIS , KIENZLE MICHAEL G. , MARTINS JAMES B.
Published: July 2006

A patient with a dilated cardiomyopaphy experienced a cardiac arrest when taking tocainide for asymptomatic nonsustained ventricular tachycardia. After successful resuscitation from ventricular fibrillation and exclusion of a myocardial infarction, an electrophysiological evaluation was performed. Drug‐free study #1 revealed no induction of ventricular tachycardia. A tocainide study revealed induction of sustained monomorphic ventricular tachycardia. Drug‐free study #2 revealed induction of nonsustained ventricular tachycardia. This report illustrates a possible proarrhythmic effect of tocainide.
Strength‐Duration Curves of Fixed Pulse Width Variable Tilt Truncated Exponential Waveforms for Nonthoracomy Internal Defibrillation in Dogs
Authors: CHAPMAN PETER D. , WETHERBEE JULE N. , VETTER JAMES W. , TROUP PAUL , SOUZA JOSEPH
Published: July 2006

Six anesthetized dogs (wgt 19.6 + 1.1 kg) underwent defibrillation trials using truncated monophasic pulses of 2.5—20 msec in duration. The current pathway consisted of a 4 cm2 RV catheter electrode (cathode) and a 13.9 cm2 subcutaneous chest wall patch (anode). Fibrillation was induced by alternating current and defibrillation attemped 10 seconds later. Only one test shock was assessed for each fibrillation episode. The various durations were tested randomly, and the minimum peak voltage and energy resulting in defibrillation was determined for each. Shorter pulse durations were associated with lower energies with pulses of 2.5—15 msec having significantly lower energy thresholds than shocks of 20 msec (P < 0.05). The relationship between duration and voltage threshold is hyperbolic with minimum voltage between 7.5 and 12.5 msec while the shortest and longest pulses were associated with the highest voltage thresholds. Shocks of 5 to 15 msec were associated with significantly lower voltage threshold than 2.5 msec pulses (P < 0.05). The threshold average current (Iav) reached a nadir at 10 msec. Shocks in the midrange of those tested resulted in the best combination of low average current and energy requirements for defibrillation using this nonthoracotomy lead system.
The Importance of Different Atrioventricular Intervals for Exercise Capacity
Authors: RYDÉN L. , KARLSSON Ö. , KRISTENSSON B.‐E.
Published: July 2006

In order to determine whether different atrioventricular intervals influence the maximal exercise capacity, 15 patients with second degree or complete atrioventricular block and no signs of left ventricular failure were studied, They all had atrioventricular synchronous pacemakers. Maximal exercise tests (sitting bicycle ergometry) were performed at four different atrioventricular intervals (50, 100, 150, and 200 ms) and during rate‐matched asynchronous ventricular pacing. The patients thereby served as their own controls. Ventricular rate, maximal oxygen uptake and minute ventilation were measured and perceived exertion estimated every minute. Different atrioventricular intervals did not affect the maximal exercise capacity, the maximal oxygen uptake, the perceived exertion or minute ventilation. Since the results were similar during atrioventricular synchronous pacing at various atrioventricular intervals and on rate‐matched asynchronous ventricular pacing, this study supports previous findings that the important factor for maximal physical performance is not a preserved atrioventricular synchronization but the ability to increase the ventricular rate.
Rate Dependent Depression of Subsidiary Ventricular Impulse Formation—Cause of Stokes‐Adams Attacks in a Patient with Rate Modulated Pacing
Authors: SCHMIDINGER HERWIG , PROBST PETER , WEBER HEINZ , KALIMAN JOSEF
Published: July 2006

Following His bundle ablation and implantation of a rate adaptive pacemaker (Vitatron TX 911) a 52‐year‐old gentleman experienced several presyncopal attacks while driving a car. On examination pectoralis muscle contraction caused temporary pacemaker inhibition. Incremental overdrive stimulation demonstrated progressive depression idioventricular automaticity and was associated with similar symptoms following overdrive at high pacing rates. Following appropriate pacemaker programming the patient remained symptom free.
Documented Symptomatic Bradycardia and Symptom Relief in Patients Receiving Permanent Pacemakers: An Evaluation of the Joint ACC/AHA Pacing Guidelines
Authors: LAMAS GERVASIO A. , DAWLEY DOUGLAS , SPLAINE KEVIN , FOLLAND EDWARD D. , FRIEDMAN PETER L. , ANTMAN ELLIOTT M.
Published: July 2006

Recently, emphasis has been placed on documenting symptomatic bradycardia (DSB) before pacemaker placement can be justified in some patients. This study was designed to judge whether DSB improved the likelihood of symptom relief after pacing in 93 patients who had symptoms prior to pacing. Patients with complete heart block (Group A) had excellent symptomatic relief with or without pre‐pacemaker DSB (100% vs 94%, P = NS). Patients with other diagnoses (Group B) also had a high incidence of symptomatic relief after pacing, regardless of whether or not DSB was present pre‐implant (28/30 (93%) vs 23/28 (82%) P = NS). When evaluated as a test to predict the response to pacing for Group B patients, spontaneously occurring symptomatic bradycardia was neither highly sensitive (55%) nor highly specific (71%). Moreover, while the ability of a positive test to predict resolution of symptoms after pacing was high (93%), the ability of a negative test to predict a poor outcome after pacing was low (18%). The absence of DSB should not rule out permanent pacing for symptomatic patients in any diagnostic group. Future pacing guidelines should be revised to offer additional detail regarding the influence of symptoms, extent of asymptomatic bradycardia, and results of provocative tests in determining which implants should be classified as definitely indicated.
A New Low Threshold Platinized Epicardial Pacing Electrode: Comparative Evaluation in Immature Canines
Authors: KARPAWICH PETER P. , STOKES KENNETH B. , HELLAND JOHN R. , JUSTICE CHERYL D. , ROSKAMP JACQELINE O.
Published: July 2006

A prospective comparison of pacing and sensing capabilities between the conventional Medtronic Model 4951 platinum‐iridium epicardial pacing electrode and a new modified “platinized” version of the same electrode was performed in immature canines to determine if the new electrode design improves pacing in the immature myocardium. The conventional electrode was modified by electroplating platinum black particles onto the surface to increase the effective or true microscopic surface area, yet essentially maintain the same overall geometric electrode size. Both epicardial electrodes were inserted into the right ventricular myocardium with the lead pad sutured to the epicardium, and externalized to the scruff in five puppies (age 3 months). An additional left ventricular lead was implanted to permit chronic pacing following epicardially‐induced atrioventricular block. Acute and chronic sensing and pacing capabilities of each externalized electrode were performed at implant and weekly up to 4 months. Histologic examination of each electrode implant site was performed at the end of the study period. At implant, both electrodes exhibited comparable values for sensed R waves, lead impedances, and pacing thresholds. During the study, the platinized electrode exhibited lower pacing thresholds. Analysis of all postimplant data demonstrated this threshold difference to be significantly lower (P < .01) for the platinized version. Lead impedance and sensing capabilities remained comparable between the two designs. Histologic study demonstrated less fibrotic infiltration at the platinized electrode site. This preliminary evaluation indicates that for the duration of the postimplant study period, the platinized epicardial electrode design was associated with significantly lower thresholds and less fibrosis as a function of time compared to the conventional smooth electrode surface design. The new platinized electrode limits exit block in the developing immature myocardium and permits safe pacing at lower pulse widths and voltages to increase battery life.
Long‐Term Follow‐up of Atrioventricular Junctional Transcatheter Electrical Ablation
Authors: LÉVY SAMUEL , BRU PAUL , ALIOT ETIENNE , ATTUEL PATRICK , BARNAY CLAUDE , CLEMENTY JACQUES , EBAGOSTI ANDRI , FAUCHIER JEAN‐PAUL , FONTAINE GUY , LECLERCQ JEAN‐FRANCQIS
Published: July 2006

Complete data concerning long‐term results of transcatheter electrical ablation of the atrioventricular junction is not available. At the request of the French Cardiac Arrhythmia Working group we undertook an inquiry in October 1983. All centers potentially able to perform such procedures were asked to report their experience. Eight centers have performed one case or more, over a period of 3 years, for a total of 91 patients. The mean follow‐up completed in all patients in April 1986 was 12 ± 10 months. The procedure was indicated for a supraventicular arrhythmia resistant to a mean of 3.9 ± 1.3 classes of antiarrhythmic agents. Atrial flutter or fibrillation in 54 (59%) and atrioventricular nodal reentry in 17 (18%J were the most common arrhythmias. A mean of 2.6 ± 2.3 electrical shocks (range 1–14 shocks) with a stored energy of 130–400 joules was delivered during 1–5 sessions. Complete heart block was obtained in 83 patients and persisted at the time of discharge from the hospital in 46 patients (50.5%). The immediate complication (within 24 hours after the procedure) included ventricular fibrillation successfully converted (one patient) and nonsustained ventricular tachycardia (three patients). Late complications included one death 3 days after the procedure, in a patient in whom sustained ventricular tachycardia was documented, nonsustained ventricular tachycardia in two patients, sepsis in three patients and pericardial effusion in one patient. At the time of the follow‐up, there were three additional deaths related to sepsis due to pacemaker pocket infection in one patient and to preexisting congestive heart failure in two patients. Chronic complete heart block was present in 36 patients (41%) high degree heart block (2 nd degree or advanced) in seven patients (8%) first degree in 16 patients (18%). The remaining patients had either normal PR interval or were in atrial fibrillation. Seventy‐five patients (82%) were asymptomatic including 39 patients with resumption of AV conduction with (28 patients, 30%) or without (11 patients, 12%) antiarrhythmic therapy. The procedure failed in 12 patients (13%). This experience suggests that AV junctional transcatheter ablation is a highly effective procedure. However, the potential of early and late complications including arrhythmic death leads us to reserve this technique to patients with drug‐refractory supraventricular tachyarrhythmias and in whom other forms of therapy are not applicable.
A Noninvasive Pre‐Atrial Activity Recording by Signal Averaging Using Esophageal Electrode
Authors: KAO TSAIR , YU BEVERLY C. , KONG CHI‐WOON , CHEN CHUNG‐YIN , CHIANG BENJAMIN N.
Published: July 2006

A noninvasive method employing the technique of signal averaging has been developed for recording sinoatrial (S‐A) activity (pre‐ P wave). Recordings were obtained in man at the time of right heart catheterization. A bipolar esophageal electrode was utilized to record the prominent P waves that were used for triggering in the averaging process. After summing 150 beats, which had coefficients of correlation 0.97 or larger, deflections of small amplitude (< 40 μV) were obtained preceding the atrial activity. Direct catheter recordings were also taken for comparison. With the new noninvasive method, the sinoatrial conduction time (SACT) estimated for patients with sick sinus syndrome (SSS) was 106 ± 24 ms (101 ± 20 ms for the same group measured directly). The SACT for healthy subjects used as the control group was 55 ± 18 ms. There was good correlation between the pre‐atrial activity recorded noninvasively by the esophageal electrode method and invasively from the direct catheter method. The linear correlation coefficient between these two techniques was 0.89 (P < 0.001) in 17 patients.