bluuebunny/crossref_metadata_2025 huggingface dataset:
Permanent Form of Junctional Reciprocating Tachycardia Involving an Atrio‐Hisian Accessory Pathway: Electrophysiologic and Histologic Correlations
Authors: FINZI ANDREA , ROSSI LINO , PAGNONI FRANCO , MATTURRI LUIGI , LOTTO ANTONIO
Published: July 2006

We present clinical, electrophysiologic and morphologic correlations of a patient with a permanent form of junctional reciprocating tachycardia, who died from a lung tumor. At electrophysioiogic study, the tachycardia circuit was suspected to involve an atrio‐Hisian accessory pathway antegradely and the AV node retrogradely; a ventriculo‐atrial accessory pathway was excluded. Pathologic examination revealed a right‐sided atrio‐Hisian accessory pathway and an area of abnormal dispersion in the distal His bundle fibers. This case is consistently different from another previously reported case in which a concealed, serpiginous, septal atrioventricular accessory pathway was demonstrated by anatomic examination. Thus, different substrates seem to be responsible for the permanent form of junctional reciprocating tachycardia.
Atrial Lead Perforation: A Case Report
Authors: IRWIN JAMES M. , GREER G. STEPHEN , LOWE JAMES E. , GERMAN LAWRENCE D. , GILBERT MARCEL R.
Published: July 2006

We report a patient in whom a chronic atrial lead perforated the right atrium and the right lung. This resulted in an hemopneumothorax and pneumomediastinum which was clearly documented by a chest computerized tomographic scan. The finding of pneumomediastinum should suggest atrial lead perforation. The utility of the chest computerized tomographic scan in diagnosing lead perforation is well illustrated by this case.
A New Sock Electrode for Recording Epicardial Activation from the Human Heart: One Size Fits All
Authors: WORLEY SETH J. , IDEKER RAYMOND E. , MASTROTOTARO JOHN , SMITH WILLIAM M. , VIDAILLET HUMBERTO , CHEN PENG‐SHENG , LOWE JAMES E.
Published: July 2006

Simultaneous recording of epicardial activation from multiple sites during open heart surgery is essential for studying unstable ventricular arrhythmias. A previously described sock electrode array for this purpose requires custom‐woven nylon sock material and expensive machined button electrodes. The limited compiiance and elasticity of nylon requires that a new sock be individually fitted for each heart. Despite careful fitting, 17–20% of electrodes do not make satisfactory epicardial contact in dogs. Further, electrodes frequently dislodge from the sock and wires break at the button electrode solder joint. Recognizing these limitations, we formed a new sock from Xspan* tubular dressing material and devised electrodes that attach securely to the sock. In six dogs. 90%± 3% of electrodes made satisfactory contact using the same Xspan* sock. significantly (p < .01) more than with the nylon sock despite far less labor. The same size X span* sock with 60 snap electrodes was used to record from 27 human hearts of widely different dimensions. Satisfactory epicardial contact was obtained in 90%± 14% of electrodes in the 18 patients with Wolff‐Parkinson‐White syndrome (WPW) and 75%± 15% of electrodes in the nine patients with coronary artery disease. In no case did an accessory pathway fail to conduct following sock placement. The hemodynamic effect of the Xspan* sock was evaluated in four dogs and was found to be minimal. Both the Xspan* sock and the snap electrodes are easily made from inexpensive, readily available materials. The same Xspan* sock accommodates o wide range of heart sizes, and the electrodes supported by the Xspan* sock record significantly better and with less dislodgement and wire breakage than previous socks.
Physiological Pacing: Present Status and Future Developments
Authors: WIRTZFELD A. , SCHMIDT G. , HIMMLER F. C. , STANGL K.
Published: July 2006

With the increasing tendency to implant pacemakers not only for life‐threatening bradycardias but also for improving cardiodynamics in patients with bradycardia, it soon became apparenf that classical VVI pacing is not truly able to optimize circulatory performance. Experience has shown fbat with ventricular pacing augmentation of cardiac output takes place only initially but is not maintained on a long‐term basis,1, 2 exercise capacity remains markedly reduced,3, 5 (here is only an unsatisfactory influence on the degree and course of heart failure2, 4, 6–9 and, in an occasional patient, cardiac function may even deteriorate as compared to the situation prior to pacing.10–13 Because the disappointing hemodynamic effect of fixed rate ventricular stimulation was at least partly due to the “unphysiological” mode of pacing provided by those systems which fail to restore AV synchrony and to increase heart rate with changing metabolic requirements, so called physiological pacemakers were developed. These pacing systems either maintain AV‐synchrony and/or reestablish some way to adapt the pacing rate (Table I). This study delineates the hemodynamics of the paced heart with special reference to the role of AV relationship and rate control; it describes the clinical experience with physiological pacing and provides some ideas leading to present and future developments for rate adaptive pacing systems.
Double Sensing by Atrial Automatic Tacbycardia‐Terminating Pulse Generator
Authors: BAROLD S. SERGE , FALKOFF MICHAEL D. , ONG LING S. , HEINLE ROBERT A.
Published: July 2006

This report describes two cases of double sensing of the P and QRS signals by an implanted atrial bipolar automatic burst tachycardia‐terminating puise generator (Inlermedics CyherTach 60) used for the treatment of supraventricular tachycardia. Double sensing occurred during normai sinus rhythm at a rate slower than the tachycardia detection criterion and caused inappropriate delivery of burst stimulation. These observations underscore the importance of the far‐field QRS signal in the detection of supraventricular tachycardia by automatic puise generators sensing the atrial eiectrogram.
Hemodynamic Findings During Sinus Rhythm, Atrial and AV Sequential Pacing Compared to Ventricular Pacing In a Dog Model
Authors: ZHOU JIN‐TAI , YU GONG‐YUAN
Published: July 2006

The hemodynamic responses of atrial lAF], atrioventricu‐lar sequential (AVP) and ventricuJar pacing (VP) were compared to sinus rhythm (SfiJ in seventeen anesthetized dogs with intact AV conduction. The atrium and/or ventricle were paced at fixed rates above the control sinus rate. An AV interval shorter than normal conduction was selected to capture the ventricle. The changes of pulmonary capillary wedge pressure (PCWP, mmHg). mean aortic pressure (MAP, mmHg), cardiac output (CO, L/min), systemic vascular resistance (SVR, dynes/s/cm−5), left ventricular stroke work index (SWI) and mean systolic ejection rate (MSER, ml/s) during sinus rhythm, atrial pacing and atrio‐ventricular sequential pacing (expressed in percentages of the individual values during ventricular pacing) were:

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The importance of atrial systole for cardiac performance was clearly demonstrated in dogs with normally compliant hearts. In both atrial and atrioventricular sequential pacing compared to ventricular pacing there was a reduction of pulmonary capillary wedge pressure (PCWP) (p < 0.01) and systemic vascular resistance (SVR) (p < 0.01) despite an increase in cardiac output (CO). The lesser mean systolic ejection rate (MSER) found during atrioventricular sequential pacing compared to sinus rhythm and atrial pacing may be explained by the abnormal ventricular depolarization in this pacing mode; nevertheless, the mean systolic ejection rate was still greater than that found during ventricular pacing (p < 0.05).
Spinal Cord Stimulation and Motor Disorders
Authors: WALTZ JOSEPH M. , ANDREESEN WAYNE H. , HUNT DAVID P.
Published: July 2006

Spinal cord stimulation has been investigated by us during the past 10 years in the treatment of various disorders of the motor system. The effectiveness was studied in 735 cases, including cerebral palsy (212), dystonia (129), torticollis (66), spinal cord injury (169), and degenerative diseases (159). Our resuits indicate that in properly selected patients, stimulating the spinal neural axis is therapeutically effective in the majority of the cases treated. Our data demonstrate that the level stimulated, the pattern and the polarity of the applied field, and the frequency of the stimulation are critical to achieve a satisfactory therapeutic result and must be individualized in each patient.
Epidural Spinal Electrical Stimulation in Peripheral Vascular Disease
Authors: AUGUSTINSSON LARS‐ERIK
Published: July 2006

Epidural spinal electrical stimulation (ESES) has been valuable in the control of pain arising from peripheral vascular disease. Thirty‐two of 34 patients experience some relief of pain and 12 of 24 patients showed healing of ischemic ulcers. This technique may prove to be useful in preventing or delaying amputation of ischemic limbs. A prospective randomized study has been undertaken to assess whether this form of electrical stimulation can save limbs.
Cerebellar Stimulation for Spastic Cerebral Palsy; Preliminary Report; On‐going Double Blind Study
Authors: SCHULMAN JOSEPH H. , DAVIS ROSS , NANES MARIO
Published: July 2006

To date, June 1, 1986, 33 spastic cerebral palsy (CP) patients have taken part in a double blind study testing the safety and efficacy of chronic cerebellar stimulation (CCS) for reduction of spasticity and improvement in function. Seven U.S. surgical centers involving ten neurosurgeons have implanted the Neurolith 601 cerebellar stimulator supplied by Pacesetter Systems Inc. (Sylmar, CA). A pilot study was run with three patients at Stanford University (Stanford, CA) using taped‐on real (strong) and dummy (weak) magnets to control the ON‐OFF status. Following the pilot study, a magnetically controllable switch was placed in line between the Neurolith stimulator and the cerebellar lead to allow more reliable switching sequences for the study. The test battery included joint angle measurements (passive and active), motor performance testing, reaction time, hand dynamometry, grooved peg board placement, hand/foot tapping, and rotary pursuit testing. Testing only was done at presurgery. Testing and ON‐OFF switching was performed following recovery from surgery and at one, two, and four months. After four months, the switch was left turned ON. Of the 30 patients using the implanted switch, 11 were dropped from the study and seven are still in progress. Of the 11 dropped from the study, four were due to switch problems and three were due to double blind protocol violations, i.e., the participants discovered the stimulus status. The remaining four were removed because of a broken lead, infection, or unrelated medical problems, or refusal to participate after implant. A preliminary analysis indicated that three‐quarters of the patients have a demonstrable quantitative improvement during the time the stimulation was “ON.” Three patients showed no significant change.
Indications for Multi‐ or Single‐Channel Cochlear Implant for Rehabilitation of Total Deafness
Authors: CHOUARD C.H. , FUGAIN C. , MEYER B. , CHABOLLE F.
Published: July 2006

Only totally deaf patients who do not experience improvement when using classical hearing aids are candidates for a cochlear implant. Preoperative assessment of potential benefits of a cochlear implant may improve selection of patients with pre‐ or postlingual total, deafness, so that the most appropriate system can be implanted. The psychological status of potential candidates for implantation is particularly important because the results of postoperative re‐education depends on motivation of the patient. The Round Window electrical stimulation test supplies us with important and measurable data (electrical threshold level, tone decay test). The duration of deafness, the degree of the deafness, and the cochlear tomodensitometry do not affect the decision to implant a cochlear device, (i.e., since the socialization level of the patient is a considerable factor). Preoperative assessrrient of the patient is very useful. As a result of our experience in 115 implanted cases suffering from pre‐ and postlingual deafness, we are now able to predict the good or bad results in our patients. Therefore, in patients who have many adverse factors for recovery, it seems to us more reasonable and cheaper to implarit a single‐channel system instead of a multichannel system, which must be reserved for patients who should do well. In very young children, the most appropriate system seems to be extra cochlear single‐channel implant.
FES for Bladder: Direct or Indirect Means?
Authors: TALALLA ANDREW , BLOOM JOSEPH W. , QUANG NGUYEN
Published: July 2006

Efforts to restore function to the neuroiogically disabled lower urinary trad by direct electrical stimulation of the bladder wall have met with only very limited success. This has been due to pain and cocontraction of bladder outlet mechanisms caused by presumed spread of the large currents required to effectively directly stimulate the detrasor muscle. Stimulation at the four anatomical sites of the sacral neural outflow on the other hand has been more successful. Conus medullaris stimulation has resulted in “good results” in just over half of the 28 patients so treated. Acceptance of this technique has been limited by the poor selectivity of the intramedullary electrodes in stimulating only the target motor neurons and the resultant clinical problems with the consequent stimulus current spread. Sacral anterior root stimulation has been used in at least 88 patients with generally good results. Cocontraction of the detrusor and external urethral sphincter are circumvented by the use of an intermittent pattern of stimulation. The primary disadvantage of this technique is the obligatory placement of the electrodes within the cerebrospinal fluid compartment. Clinical experience with stimulation of the extradural sacral mixed nerves is limited. Experimental studies indicate that success with this technique requires dorsal rhizotomy and pudendal neurotomy. Preliminary clinical experience suggests that these surgical manipulations may not be necessary for a successful outcome. The literature on clinical application of pelvic nerve stimulation is too limited for detailed comment on this technique. A definitive technique for restoration of bladder function by electrical stimulation remains to be developed.
Limitations of the Long‐Term Clinical Application of Rate Hysteresis
Authors: HOLLINS W. JOSEPH , LEMAN ROBERT B. , KRATZ JOHN M. , GILLETTE PAUL C.
Published: July 2006

Rate hysteresis is the ability of a pacemaker to pace at an automatic rate that is different from the escape rate. We reviewed our experience with this programmable feature and its utility. The long‐term clinical application of rate hysteresis was limited due to the development of atrial fibrillation or to slowing of the intrinsic cardiac rhythm in 27.6% of the 29 patients. Since many patients with sick sinus syndrome have preserved AV conduction, one might expect that these patients would have an adequate intrinsic heart rate to allow successful use of rate hysteresis pacing mode. Sick sinus syndrome was the intrinsic rhythm disturbance in 63% of the group requiring discontinuation of rate hysteresis. These patients may represent a subgroup in whom any theoretical advantages provided by the rate hysteresis feature may be outweighed by the propensity for the development of atrial fibrillation or significant slowing of the intrinsic rhythm.
The Effects of Direct Current Countershock on Ventricular Late Potentials
Authors: VOLOSIN KENT J. , GREENSPON ARNOLD J.
Published: July 2006

Signal averaging is a noninvasive method of recording ventricular late potentials. These late potentials are present in many patients with sustained ventricular tachycardia. Analysis of ventricular late potential characteristics may develop as a useful marker of antiarrhythmic drug efficacy. Often antiarrhythmic drugs are tested acutely in the electrophysiology laboratory after direct current countershock (DC shock). The purpose of this study was to investigate the effects of DC shock delivered for cardioversion of sustained ventricular tachycardia or fibrillation on ventricular late potentials. Signal averaged electrocardiograms (SAEKGs) were recorded before and after 13 DC shocks. There was no significant change in QRS duration, duration of the high frequency filtered QRS, or duration of the high frequency signal under 40 microvolts. There was a small increase in the root mean square amplitudes of the terminal 40 milliseconds (41 μV to 49 μV). This degree of change is felt to be clinically insignificant. Except for one trial, no late potential appeared or disappeared after electrical cardioversion. We have shown that ventricular late potentials are only slightly altered by programmed ventricular stimulation, induced sustained ventricular tachycardia or ventricular fibrillation, and DC countershock. To analyze changes in ventricular late potentials after antiarrhythmic drug administration in the electrophysiology laboratory, in those patients requiring DC countershock, comparisons should be made to postshock SAEKGs rather than those obtained prestudy.
Particularities of Dual Chamber Pacemaker Therapy in Patients after Orthotopic Heart Transplantation
Authors: MARKEWITZ ANDREAS , KEMKES BERNHARD M. , REBLE BERNHARD , OSTERHOLZER GEORG , REICHART BRUNO , PURICELII CESARE , FERUGLIO GIORGIO A. , STERNOTTI GIULIO , BEHRENBEGK DIETER W.
Published: July 2006

Since August 1981, 33 orthotopic heart transplantations were performed in our hospital. Three of these patients (9%) had sinus bradycardias with rates as low as 30 beats/min; they were treated by implantation of a dual chamber pacemaker. Those patients had two atria as a result of orthotopic heart transplantation, but only the donor atrium was suitable for positioning the atrial lead. In the postoperative period, some nonsurgical complications were observed in one patient who developed atrial fibrillation which we treated with drugs. A cyclosporin‐evoked tremor produced several asystoles due to false inhibition by myopotential interference in the VVI mode. During an episode of acute rejection combined with renal insufficiency, loss of atrial and ventricular sensing occurred. The other patients showed no pacemaker‐related complications. Our findings in this unique population of pacemaker patients are discussed.
Reentrant Ventricular Arrhythmias in the Late Myocardial Infarction Period: 14. Mechanisms of Resetting, Entrainment, Acceleration, or Termination of Reentrant Tachycardia by Programmed Electrical Stimulation
Authors: EL‐SHERIF NABIL , GOUGH WILLIAM B. , RESTIVO MARK
Published: July 2006

The mechanisms of resetting, entrainment, acceleralion, or termination of reentrant ventricular tachycardia by programmed electrical stimulation were studied in the canine post‐infarction model. In this model, reentrant circuits were localized in the epicardial layer overlying the infarction and were accessible to detailed mapping by multiplexer techniques. The reentrant circuit has a characteristic figure‐eight configuration in the form of two circulating wavefronts around arcs of functional conduction block that coalesce into a slow common reentrant wavefront. Termination of reentrant tachycardia occurred when a stimulated wavefront arrived earlier to a strategically located area in the proximal portion of the zone of slow conduction, before refractoriness expired distally, resulting in conduction block. The three factors that determined if the stimulated wavefrout could reach this zone in time for conduction block were: (1) the cycle length of stimulation; (2) the number of stimulated beats, and (3) the site of stimulation. The most optimal situation for stimulated termination of reentry was a critically coupled single stimulus applied to the ischemic zone close to the proximal side of the zone of slow conduction that captured locally and conducted prematurely to the strategic zone for conduction block. When a single stimulated wavefront failed to terminate reentry, one or more subsequent wavefronts succeeded. However, the stimulated train had to be terminated following the beat that interrupted reentry. Otherwise, a subsequent stimulated beat could reinitiate the same reentrant circuit or induce a different circuit. The new circuit could have a shorter revolution time, resulting in tachycardia acceleration, and occasionally degeneration into ventricular fibrillation. Overdrive termination of reentry required both a critical cycle length of stimulation and a critical number of beats in a stimulated train. Otherwise, the stimulated train could establish a new balance of refractoriness and conduction velocity in the reentrant pathway. This could perpetuate the reentrant process at the shorter cycle length of the stimulated train and spontaneous reentry would resume on termination of the train (entrainment). The study provides better understanding of the mechanisms of action of programmed electrical stimulation on reentrant ventricular tachycardia.
Intermittent Pacemaker Syndrome: Revision of VVI Pacemaker to a New Cardiac Pacing Mode for Tachy‐Brady Syndrome
Authors: McCORMICK DANIEL J. , SHUCK JOHN W. , ANSINELLI RICHARD A.
Published: July 2006

A patient with tachy‐brady syndrome manifested by paroxysmal atrial fibrillation and symptomatic sinus bradyrardia and treated by VVI pacing developed pacemaker syndrome during episodes of ventricular pacing. His cardiac pacemaker revised to a dual chamber system utilizing the new AV sequential DDI pacing mode which eliminated pacemaker‐related tachycardias and totally abolished the pacemaker syndrome symptoms. There have been no further episodes of atrial fibrillation, possibly due to elimination of temporal dispersion of refractory periods during bra‐dycordin. The propensity for atrial fibrillation has also been minimized by excluding competitive atrial stimulation during DVI pacing. The DDI mode provides the clinician increased utility und flexibility in the use of AV sequential pacing therapy.
Cardiac Stimulation Threshold in Familial Amyloidosis with Polyneuropathy
Authors: JANSSON JAN HÅKAN , ERIKSSON PETER , BOMAN KURT , ERIKSSON STURE , OLOFSSON BERT‐OVE , SJÖGREN BARBRO
Published: July 2006

It has been suggested that a higher cardiac stimulation threshold reduces the applicabilty of pacemaker therapy in cardiac amyloidosis. We therefore reviewed threshold data in patients with familial amyloidosis with polyneuropathy (FAP), which is an inherited type of systemic amyloidosis, invariably involving the heart. Fourteen FAP patients treated with a pacemaker were studied. The mean (±SD) voltage stimulation threshold during implantation was 1.0 ± 0.5 V, and noninvasive follow‐up 6 months later revealed a mean Vario threshold of 1.9 ± 0.5 V. Beyond this time, the threshold tended to be stable, and high threshold exit block did not occur in any patient. Several FAP patients did show a moderately elevated threshold, and a multiprogrammable pulse generator with a high output capability is recommended when pacemaker therapy is considered in these patients.
Noninvasive Assessment by Doppler and M‐Mode Echocardiography of Hemodynamic Responses to Temporary Pacing and to Ventriculoatrial Conduction
Authors: FAERESTRAND SVEIN , ØIE BERTIL , OHM OLE‐JØRGEN
Published: July 2006

A new, dual‐chamber temporary pacing lead was introduced via the subclavian vein in 20 patients who needed a temporary pacemaker. Stroke volume (SV) was measured continuously by combining M‐mode and noninvasive Doppier echocardiography during spontaneous rhythm (SR), AV sequential pacing at a positive AV interval (DP), ventricular pacing (VP) and AV sequential pacing at a negative AV interval (VA pacing). The valvular functions were determined by Doppler echocardiography. Left ventricular dimensions and function, and left atrial size were measured by M‐mode echocardiography. In the nine patients with no valvular heart disease and with no ventriculoatrial (VA) conduction (group I) the CO increased 83 ±11% during DP and 42 ± 9% during VP as compared to during SR when the heart rate (HE) was increased from 34 ± 3 to 72 ± 1 beats/min. The CO was 29 ± 3% higher during DP than that during VP. In the seven patients with valvulox heart disease and with no VA conduction (group II), the increment in CO compared to that during Sfi was SZ ± 12% during DP and 31 ±17% during VP: the CO was 17 ± 4% higher during DP than that during VP. In the four patients with spontaneous VA conduction (group III), the CO during DP was 35 ± 10% greater than that during VP, which did not result in an increase in the CO compared to that during SR in spile of an increase in HR from 52 ± 8 to 74 ± 2 beats/min. The study demonstrated that DP is the preferred temporary pacing mode and also that VA conduction during VP resulted in a mean decrease of 20% in CO compared to that during VP without VA conduction. The hemodynamic benefit from DP compared to SR seems to decrease when the left ventricular end‐diastolic dimension increases. Furthermore, patients with large left ventricular end‐systolic dimensions seem to have a lower increase in stroke index during DP as compared to that during VP than patients with smaller end‐systolic dimensions.
Experimental Myocardial Cryoinjury: Local Electromechanical Changes, Arrhythmogenicity, and Methods for Determining Depth of Injury
Authors: MARCHLINSKI FRANCIS E. , FALCONE RITA , IOZZO RENATO V. , REICHEK NATHANIAL , VASSALLO JOSEPH A. , EYSMANN SUSAN B.
Published: July 2006

To characterize the electromechanical effects of acute and 2‐week‐old cryoinjury, programmed stimuiation and epicardial M‐mode echo mapping (7.5 mHz) were performed prior to, at 15 minutes and 35 ± 2 days after cryoinjury in 10 dogs. Epicardial and intramural bipolar and unipoiar electrograms were recorded in five of the dogs. Cryoinjury was produced with a 5 mm in diameter flat cryoprobe at ‐60°C applied to the left ventricular epicardium for 10 minutes at each of six contiguous sites. Cryoinjury, acutely and at 2 weeks, was characterized by a loss of normal intramural systolic thickening and a decrease in echo density. The maximum depth of cryoinjury determined by echo ranged from .55 to .85 cm acutely, and .50 to .80 cm chronically and it correlated acutely and chronically (r = .80; r = .85) with pathologically documented depth of cryoinjury at 2 weeks. Acutely, the presence of either an abnormal intramural unipolar or bipolar electrogram also defined the depth of cryoinjury within .16 cm. In contrast, epicardiai electrograms were not useful for judging depth of cryoinjury. A QS complex on the epicardial unipolar electrogram was recorded over the cryoinjury acutely and at 2 weeks in four of five dogs despite preserved subendocardial systolic wall thickening and normal histology extending 40 to 65% of the wall thickness. Epicardiai bipolar eiectrograms uniformly showed a marked decrease in amplitude and siope of the intrinsic deflection, a small hut insignificant increase in width and no multicomponent activity. Ventricular fibrillation was reproducibly initiated with three ventricular extrastimuli in five of 10 dogs at 2 weeks. No ventricular tachycardia was initiated. Thus, cryoinjury produces characteristic echogram and electrogram changes that are immediate and persistent. The distinct echo signature as well as the presence of abnormal intramural electrograms can be used to judge the depth of cryoinjury. Cryoinjury does not potentiate the inducibility of ventricular tachycardia. The significance of the inducibility of ventricular fibrillation cannot be determined. Our cryoinjury model can be used to characterize electrograms which represent recordings of myocardial depolarization through an interface of cellular necrosis and early fibrosis.
Rate‐Responsive Pacing by Means of Activity Sensing Versus Single Rate Ventricular Pacing: A Double‐Blind Cross‐Over Study
Authors: SMEDGÅRD P. , KRISTENSSON B.‐E. , KRUSE I. , RYDEN L.
Published: July 2006

The clinical appiicabiJity of rate‐responsive pacing (RRP) by means of activity sensing has been tested in 15 patients. The patients (ages 24–85) had sinus node dysfunction (2), atrial fibrillation (7), or sinus rhythm (6) combined with complete atrioventricular block. Exercise capacity was investigated on a bicycle ergometer and on a treadmill in a double‐blind cross‐over study design following one week each of fixed rate ventricu/ar pacing (70 bpm) and rate‐responsive pacing (60/125–150 bpm). The patients answered a questionnaire concerning subjective symptoms. A Holter ECG was recorded during 24 hours of all day activity on rate‐responsive pacing. During exercise in the rate‐responsive mode, heart rate increased more on the treadmill than on the bicycle. A majority of the patients (13 of 15) preferred rate‐responsive pacing mainly due to less dyspnea and tiredness. Exercise capacity improved significantly both on bicycle (+7%; p < 0.01) and on treadmill (+19%; p < 0.01) during rate‐responsive pacing. There were no complications during the follow‐up period. In conclusion, the activitysensing pacemaker is a valuable supplement to existing types o/ pacemakers. It should be used in patients in whom an atrial electrogram cannot be used for rate triggering.
Orthodromic Pacemaker Circus Movement Tachycardia
Authors: DEN HEIJER PETER , CRIJNS HARRY J. G. M. , VAN BINSBERGEN ERIK J. , EBELS TJARK , DE JONGSTE MIKE J. L. , LIE K. I.
Published: July 2006

We report on the case of a 33‐year‐old woman with sick sinus syndrome who had an orthodromic pacemaker circus movement tachycardia (PCMT), with antegrade atrioventricular (AV) conduction and a retrograde pathway by means of a DDD (AV universal) pacemaker. This PCMT was provoked and sustained by premature ventricular contraction‐synchronous atrial stimulation (PVC‐SAS), which is a new feature for the prevention of anti‐dromic PCMTs. The conditions for occurrence of this tachycardia were: (1) PVC‐SAS; (2) atrial undersensing; (3) first degree AV block. Recommendations for prevention of this pacemaker‐mediated tachycardia are given.
Endocardial Catheter Ablation for Refractory Ventricular Tachycardia Associated with Coronary Artery Disease
Authors: HUANG SHOEI K. STEPHEN , BAZGAN ION D. , MARCUS ERANK I. , EWY GORDON A.
Published: July 2006

Percutaneous endocardial electrode catheter ablation using stored direct current (DC) electrical energy was performed in five patients with recurrent ventricular tachycardia (VT) refractory to many antiarrhythmic drugs, including amiodarone. All had prior myocardial infarction and poor left ventricular function with ejection fractions ranging from 20% to 40%. Endocardial catheter and pace mappings were used to localize the earliest site of activation during VT. Under general anesthesia, two to six shocks with 200 to 300 joules DC energy per shock were delivered to the localized sites. Immediate complications included ventricular fibrillation in one patient, transient QRS complex widening in two patients, transient complete AV block with persistent first‐degree AV block in one patient, and transient asystole in two patients. None had inducible VT immediately following ablation, or 4 to 6 days later; none had evidence of intracardiac clot by two‐dimensional (2D) echocardiography on the third to fifth day. Peak creatine kinase ranged from 189 to 1610 IU/L with 9% to 18% MB fraction. During a follow‐up of 6 to 30 months, three patients had no recurrence of VT. Two patients had recurrent VT with a slower rate, which was controlled with antiarrhythmic drugs. None had worsening of congestive heart failure. Two patients died of nonarrhythmic causes. We conclude that nonsurgical endocardial ablation of VT with an electrode catheter is effective for the treatment of refractory VT in selected patients with coronary artery disease.
Method for Antegrade/Retrograde Conduction Discrimination Using A Standard Atrial Bipolar Lead
Authors: HERSCOVICI HARRY , SCHALLHORN RICHARD S.
Published: July 2006

Significant differences between morphology, magnitude, and relative timing of antegrade and retrograde conduction were demonstrated on unipolar electrograms from a standard atrial bipolar J lead positioned in the right atrium in dogs. The morphology of the P wave sensed from the tip was more or less biphasic while the morphology of the P wave sensed from the ring was monophasic only and of lower frequency content. The unipolar‐ring P wave was attenuated in retrograde as compared with the antegrade. During retrograde conduction the unipolar‐ring signal returned to baseline earlier in time relative to the peak of the unipolar‐tip signal, than it did during antegrade conduction. Based on these differences a sensing circuit capable of discriminating between antegrade and retrograde conduction was built. This discriminator circuit, which relies on a standard lead and simple electronics, functioned reliably in trials in dogs and thus may prove to be practical for use in future pacemakers.
Myocardial Demands of Atrial‐Triggered Versus Fixed‐Rate Ventricular Pacing in Patients with Complete Heart Block
Authors: NORDLANDER ROLF , PEHRSSON S. KENNETH , ÅSTRÖM HANS , KARLSSON JAN
Published: July 2006

Hemodynamics, myocardial oxygen consumption, and lactate concentration were determined by cardiac catheterization at rest and during exercise in eight patients treated with AV universal pacemakers (DDD) for high degree AV block. The pulse generator was alternately programmed in ventricular inhibited (VVI) or atrial synchronous (VAT) mode. During VVI pacing, the cardiac output rose between rest and exercise (4.3–7.6 L/min) due to increased stroke volume. VAT pacing gave significantly greater increase (4.5–8.8 L/min) which, as the stroke volume was unchanged, resulted from acceleroted heart rate. The myocardial oxygen consumption and the coronary blood flow did not differ between VVI and VAT mode at rest or during exercise, nor did the modes make a difference in arterial systolic and pulmonary wedge pressures. These observations suggested that VAT pacing offers higher cardiac output than VVI pacing, but with similar demands on myocardial oxygen consumption.
On‐Line Interval Measurement During Invasive Cardiac Electrophysiologic Testing
Authors: ANTOLINI RENZO , KIRCHNER MICHELE , MONGERA ANDREA , DISERTORI MARCELLO , FURLANELL FRANCESCO
Published: July 2006

A microprocessor‐based timer has been developed for routine and research use in cardiac electrophysiologic studies. The cycle length (A‐A) and the conduction times through the right atrium (A(HRA)‐A[HIS]), the AV node (A‐H) and the His‐Purkinje system (H‐V) can be automatically measured beat‐to‐beat in real‐time both during sinus rhythm and during atrial pacing. The design has been refined during three years of use in over 80 clinical studies. A comparison between manual and automatic measurements has been executed for randomly chosen portions of 10 studies. With the manual measurements as reference procedures the sensitivities of the automatic measurements of the A, H and V waves were 0.98, 0.88 and 0.92, respectively, while the specificities were 0.93, 0.92 and 0.93, respectively. For the true positive measurements the correlation coefficients of the intervals were r(A‐A) = 0.9998, r(A‐H) = 0.987 and r(H‐V) = 0.988. The statistical analysis of the differences between manual and automatic readings for the intervals A‐A, A‐H and H‐V yielded mean values of −1 ms, −0.8 ms and 0.6 ms and standard deviations of 3 ms, 4 ms and 4 ms which are smaller than the accuracy of the common manual measurements.
The Effect of 50 Hz External Electrical Interference on Implanted Cardiac Pacemakers
Authors: KAYE GERALD C. , BUTROUS GHAZWAN S. , ALLEN ALI , MELDRUM STUART J. , MALE JOHN G. , CAMM A. JOHN
Published: July 2006

The effects of injected 50 Hz alternating current on the function of cardiac pacemakers has been observed in 18 patients with implanted unipolar VVI units. Current, in the range 0–600 μA was applied via electrodes attached to the patients' upper body and feet and fed from a specially designed current injection unit at the bedside. Most implanted pacemakers reverted to interference mode in the current range 29–250 μA. At current levels just below the reversion current all units developed irregular and inappropriate pacing. This current level was pacemaker dependent and varied in the range 27–246 μA. The total reversion current depended on the location of the injecting electrodes and on the patients' posture. The sensitivity of the units to injected interference was increased by deep inspiration. Temporary pacing catheters fitted to an additional ten patients were used to monitor the interference voltage which would be sensed by an implanted unit. This voltage was similarly dependent on patient posture and on deep respiration. Current injection has proved to be a safe, controllable and reproducible method of testing the sensitivity of implanted pacemakers to 50 Hz external interference.
Empiric Amiodarone versus “Ineffective” Drug Therapy in Patients with Refractory Ventricular Tachyarrhythmias
Authors: FOGOROS RICHARD N. , FIEDLER SUSAN B. , ELSON JAMES J.
Published: July 2006

Because of its presumed unique efficacy, amiodarone (AM) is often used to treat patients whose sustained ventricular tachyarrhythmias (VT/VF) appear to be drug‐refractory. To examine the efficacy of AM in such patients, we performed a retrospective analysis of 77 patients with drug‐refractory VT/VF treated with either empiric AM or with drugs predicted during electrophysiological (EP) testing to be ineffective (ID). To qualify for the study, patients had to have spontaneous, symptomatic VT/VF, and persistently inducible VT during serial EP testing with drugs. All 77 patients were offered therapy with AM. Those who refused were treated with ID, whenever possible, an ID was selected which “improved” the EP study compared to baseline. Originally, 68 patients elected AM and nine elected ID. Because of drug intolerance or inefficacy, 10 patients crossed over during the course of the study; a total of 71 patients were followed on AM for 15.7 ± 11.0 months, and 16 on ID for 17.8 + 10.8 months (mean ± SD). During follow‐up, the cumulative recurrence of VT/VF at 6, 12, and 24 months for AM versus ID was 16 ± 5% versus 44 + 12% (P < 0.002), 32 ± 6% versus 44 ± 12% (NS), and 41 ± 7% versus 44 ± 12% (NS) (± SE). The recurrence of VT was significantly lower in the AM group only for the first 6 months of therapy. Of the 10 cross‐over patients, five had recurrent VT/VF; all five had recurrences on both AM and ID, but the duration of therapy at the time of recurrence was significantly longer on AM than on ID (8.0 ± 2.0 versus 2.0 ± 2.3 months, p < 0.05). In summary, although it appeared that AM delayed the onset of VT/VF, there was no reduction in the ultimate incidence of VT/VF with AM compared to ID, when AM was used without the guidance of programmed extrastimulation or Holter monitoring. If these results are confirmed in prospective studies, there would be little reason to rely on AM as the mainstay of therapy in patients with drug‐refractory arrhythmias.
Atrioventricular Nodal Supraventricular Tachycardia with 2:1 Block above the Bundle of His
Authors: SCHMITT CLAUS , MILLER JOHN M. , JOSEPHSON MARK E.
Published: July 2006

A patient with narrow complex supraventricular tachycardia underwent electrophysiological study at which time a tachycardia was initiated which had 2:1 AV conduction, with block occurring above the His bundle. The modes of tachycardia initiation, as well as the responses to atrial and ventricular premature depolarizations during tachycardia, made a diagnosis of atrioventricular nodal reentry as the tachycardia mechanism. The unusual finding of 2:1 supra‐His block suggests the presence of tissue situated between the tachycardia circuit and His bundle, and effectively excludes the possibility of a His‐atrial bypass tract as the retrograde limb of the tachycardia circuit.
Epicardial Reflection as a Cause of Incessant Ventricular Bigeminy
Authors: VAN HEMEL NORBERT M. , SWENNE CEES A. , DE BAKKER JACQUES M.T. , DEFAUW JO J.A.M. , CUIRAUDON GERARD M.
Published: July 2006

Incessant monomorphic ventricular bigeminy was studied in a young patient with no organic heart disease. The arrhythmia could not be controlled by drug therapy. Spontaneous and artificial variation of the heart rate showed that reentry was the most likely arrhythmogenic mechanism. Peroperative epicardial and transmural mapping revealed an epicardial focal origin which was cryoablated. Reflected reentry occurring in a small area of working myocardial cells appeared to be the most likely explanation for this arrhythmia.
Body Surface Isopotential Mapping of Permanent Cardiac Pacemaker Spike Amplitudes: A Noninvasive Method for Detecting and Localizing Insulation Failure
Authors: ROSENGARTEN M. , FUNNELL W.R.J.
Published: July 2006

Cardiac pacing systems produce cardiac contractions by delivering electrical charges to the myocardium. Reliable cardiac pacing, and the longevity of pacemakers depends on the absence of electrical leaks. Electrical leaks ofen do not cause symptoms and if suspected, there are few methods which are able to identify their location and none suited to small or intermittent leaks. We surface mapped the pacemaker spike amplitudes over the pockets of 29 patients with unipolar pacemakers, several of which had suspected pacemaker leaks. For each patient, pacer voltage spikes were recorded with an optical ECG recorder from sixty‐three positions on the skin over the pacemaker. The spike voltages were interpolated with a 2‐D Fourier transform, contoured, and plotted by a computer. Electrical leaks were readily detected and their positions indicated by the resulting maps. The operative findings confirmed the map guided prediction in all six patients sent for pacemaker revision. Pacemaker spike amplitude surface mapping detects and locates pacing system insulation failures.
Evaluation of Global and Regional Left Ventricular Function Using Two‐Dimensional and M‐Mode Echocardiography in Patients With an Automatic Implantable Cardioverter Defibrillator
Authors: TRAPPE HANS‐JOACHIM , DANIEL WERNER G. , KLEIN HELMUT , FRANK GUENTER , LICHTLEN PAUL
Published: July 2006

The effects of glued epicardial patch electrodes of the automatic implantable cardioverter defibrillator on the left ventricular function was studied by two‐dimensional and M‐mode echocardiography in 15 patients. Pre‐ and postoperative end‐diastolic and end‐systolic left ventricular cross‐sectional areas were evaluated using planimetry. Regional left ventricular wall motion at the level of the left ventricular patch electrode was analyzed by two end‐diastolic and end‐systolic perpendicular axes. Left ventricular end‐diastolic and end‐systolic diameters as well as E‐point‐septal‐separation and fractional shortening were analyzed using M‐mode echocardiography. The mean time interval between preoperative echocardiograms and implantation of the automatic defibrillator was 0.3×1.3 (< 1–2) months. Postoperative echocardiograms were recorded 6.6 ± 6.9 (0.5–24) months after implantation of the device. There were no significant differences between pre‐ and postoperative mean values of end‐diastolic and end‐systolic areas and axes as well as M‐mode echocardiographic parameters. Our data show that left ventricular patch electrodes do not significantly alter global or regional left ventricular function in patients after implantation of the automatic defibrillator.
Cardiac Pacemaker Regulated by Respiratory Rate and Blood Temperature
Authors: SUGIURA TOSHIFUMI , KIMURA MOTOHIKO , MIZUSHINA SHIZUO , YOSHIMURA KEIZO , HARADA YUKIO
Published: July 2006

A new method using respiratory rate and temperature as the guides for optimal pacing is proposed. A pacemaker was fabricated which senses these two parameters simultaneously. The pacemaker functions by calculating the cardiac rate, which would he derived from the respiratory rate and the blood temperature. The higher of the two rates is adopted as the cardiac pacing rate, i.e., at which stimuli will be delivered. The operation was tested in a mongrel dog with complete atrioventricular block. After the induction of anesthesia, a thermistor temperature probe was inserted into right atrium and a respiratory rate sensor was attached around the chest. After administration of a pyrogenic drug, both respiratory rate and blood temperature increased. The pacing rate was increased from 178 beats/minute(bpm) at 36.4°C. blood temperature, and 26.5 acts/minute(apm), respiratory rate, to 233 bpm at 40.1°C and 40.0 apm. Cardiac output was increased from 2.25 liters/minute(1/pm) at the beginning to 2.50 l/pm at maximum. The transition of the guide from respiratory rate to temperature was observed at about 38°C.
Paired Comparisons of Steroid‐Eluting and Nonsteroid Endocardial Pacemaker Leads in Dogs: Electrical Performance and Morphologic Alterations
Authors: RADOVSKY A.S. , VAN VLEET J.F. , STOKES K.B. , TACKER W.A.
Published: July 2006

The effects of steroid elution from endocardial pacemaker electrodes on electrical performance and the thickness and cellularity of the reactive fibrous connective (issue formed around the stimulating electrode (peri‐electrode tissue) were determined. Comparison was made with a nonsteroid electrode implanted in the same cardiac chamber (right ventricle) in each of six dogs for 6 weeks. Paired Students t‐tests showed that steroid‐eluting leads had significantly (P < .05): (1) lower voltage stimulation thresholds (as determined in sequential measurements made on the conscious animals during the experiment and on the anesthetized dogs at termination of the study); (2) less fibrous connective tissue formation around the electrode surfaces; and (3) fewer cells per unit area of peri‐electrode fibrous connective tissue. There were also fewer (P < .10) mast cells in the reactive connective tissue surrounding steroid‐eluting leads. The thinner reactive connective tissue surrounding the steroid‐eluting electrodes was correlated with lower voltage stimulation thresholds(r = 0.7. P < .01). This is consistent with the hypothesis that the effect of the peri‐electrode connective tissue is to increase the virtual surface area of the electrode, decreasing current density in adjacent stimulatable tissue. The relatively fewer total cells and mast cells in the peri‐electrode connective tissue of the steroideluting electrodes suggest that the observed differences in fibrous connective tissue thickness, and therefore voltage stimulation threshold, may be related to a relatively decreased population of inflammatory ceils due to the anti‐inflammatory properties of the steroid.