bluuebunny/crossref_metadata_2025 huggingface dataset:
Automatic Recognition of Ventricular Arrhythmias Using Temporal Electrogram Analysis
Authors: PAUL V.E. , FARRELL T. , GILL J. , DAVIES D.W. , WARD D.E. , CAMM A.J.
Published: July 2006

Future antitachycardia devices must be able to deliver a variety of therapies according to the requirements of the underlying arrhythmia. To ensure that appropriate treatment is prescribed the device must use a detection algorithm that is able to discriminate between multiple arrhythmias. Current criteria such as rate, change of rate, duration at high rate, and high rate stability are inadequate for this purpose. Many algorithms that evaluate the morphology of the endocardial electrogram are of too great a complexity to be incorporated in implantable devices that require real‐time analysis without undue power consumption. In this study the sensitivity of a simple morphological technique (temporal electrogram analysis) is examined. The method sets threshold ‘rails’ above and below the isoelectric line and classifies ECG complexes according to the sequence and duration of rail excursions. A total of 27 ventricular tachyarrhythmias were induced in 25 patients (17 with a history of recurrent arrhythmias and eight undergoing risk stratification postmyocardial infarction). Temporal electrogram analysis (TEA), initially detected the onset of the ventricular arrhythmia in all patients whose surface ECG showed polymorphic or right bundle branch block pattern tachycardia, in 5/8 of cases with left bundle branch block pattern and in 4/5 of patients with concordant complexes across the precordial leads. After minor modifications the overall sensitivity of the method was improved to 95% (26/27 arrhythmias detected). TEA is a technique of low computational demands, which in this study, reliably discriminated between resting sinus rhythm and ventricular arrhythmias.
Persistent Atrial Standstill—Clinical, Electrophysiological, and Morphological Study
Authors: TALWAR K.K. , DEV V. , CHOPRA P. , DAVE T.H. , RADHAKRISHNAN S.
Published: July 2006

Persistent atrial standstill (PAS) is a rare disorder characterized by absence of atrial activity on the surface and intracavity electrograms, absence of atrial mechanical activity, and inability to electrically stimulate the atria. Four patients (ages 18–60 years) with PAS were evaluated. One of these (no. 3) only had right atrial (RA) standstill, whereas left atrium (LA) showed spontaneous activity and could be stimulated electrically. As RA biopsy is not possible, right ventricular (RV) endomyocardial biopsy (EMB) was obtained to identify possible atrial pathology that revealed inflammatory myocarditis, 2; amyloidosis, 1; and myocardial hypertrophy with fibrosis, 1. Three patients were given permanent pacemakers. One of these with amyloidosis died suddenly. One is lost to follow‐up. The others cases are persisting with PAS.
Paced Beats Following Single Nonsensed Complexes in a “Codependent” Cardioverter Defibrillator and Bradycardia Pacing System: Potential for Ventricular Tachycardia Induction
Authors: CALLANS DAVID J. , HOOK BRUCE G. , MARCHLINSKI FRANCIS E.
Published: July 2006

Patients with implantable defibrillotors often require bradycardia pacemakers. Adverse interactions between separate defibrillator and bradycardia pacing units hove occurred. Including failure in detect ventricular fibrillation due to persistent bradycardia pacing during the arrhythmia. A device with combined bradycardia pacing and antitachycardia therapy capability may obviate adverse device interactions. We describe a previously unrecognized phenomenon that may occur in a combined device when the algorithms for sensing bradycardia and tachycardia are “codependent”; that is, the circuitry for brady and tachyarrhythmia detection relies on the same automatic gain sense amplifier. Three of 37 patients in whom the device was implanted had ventricular tachycardia initiated when bradycardia pacing stimuli were delivered by the device after probable nonsensed sinus beats. In each case, nonsensed beats appeared to have a markedly diminished amplitude, occurred after ventricular premature depolarizations that produced large amplitude electrograms, and had an electrogram morphology that matched that of sinus rhythm. In each case, the bradycardia pacing interval was at least 1,200 msec (range 1.200 to 1,714 msec). In two of the three patients, large amplitude ventricular premature depolarizations or nonsustained ventricular tachycardia caused an adjustment of the gain control that potentiated the failure to sense the subsequent lower amplitude signal. In all three patients, the induced arrhythmia was rapidly terminated by pacing or cardioversion. Decreasing the bradycardia pacing interval by 110–514 msec has prevented recurrence during short‐term follow‐up. Our findings suggest that codependent bradycardia and antitachycardia devices may have their own unique potential difficulties in adapting to rapid changes in rate and signal amplitude.
Implantable Cardioverter Defibrillator Proarrhythmia: Case Report and Review of the Literature
Authors: COHEN TODD J. , CHIEN WALTER W. , LURIE KEITH G. , LEE MICHAEL A. , LESH MICHAEL D. , SCHEINMAN MELVIN M. , GRIFFIN JERRY C.
Published: July 2006

A 31‐year‐old man who received an automatic Cardioverter defibrillator subsequently underwent exercise testing. During exercise, a sinus tachycardia resulted above his device detect rate prompting two shocks, the second of which produced an unstable polymorphous ventricular tachycardia. In this article, we review the literature on automatic cardioverter defibrillator‐induced ventricular tachyarrhythmias as well as the management of exercise testing in patients with these devices.
Hemodynamic Effect of Physiological Dual Chamber Pacing in a Patient with End‐Stage Dilated Cardiomyopathy: A Case Report
Authors: KATAOKA HAJIME
Published: July 2006

I report a case of end‐stage dilated cardiomyopathy with first‐degree atrioventricular (AV) block, which had been resistant to intensive medical therapy and was eventually treated by DDD pacemaker. The optimal AV interval setting was decided using invasive right‐heart catheterization and Doppler echocardiography. At a pacing rate of 92/minute, an AV interval setting of between 200 and 100 msec increased left ventricular filling and enhanced myocardial contractility. An AV interval setting of 50 msec increased the left ventricular filling further. However, this resulted in deteriorated left ventricular function. Based on these findings, the pacemaker was programmed at an optimal AV delay of 100 msec, a rate of 82‐150 beats/min and a DDD mode, resulting in a good clinical course for 4 months after the therapy. Thus, it is suggested that in patients with end‐stage dilated cardiomyopathy and first‐degree AV block, an optimal AV delay setting using a DDD pacemaker can improve deteriorated myocardial function probably by increasing the left ventricular filling, and thus promote utility of the Frank‐Starling mechanism.
Impedance Measurements in the Human Right Ventricle Using a New Pacing System
Authors: WORTEL HETTY J. J. , RUITER JAAP H. , DE BOER HANS G. A. , HEEMELS JAN PIETER , VAN MECHELEN ROB
Published: July 2006

A promising new pacemaker that provides on‐line measurements of right ventricular (RV) impedance was evaluated in ten patients with symptomatic second‐ or third‐degree atrioventricular (AV) block. We tested the assumption that if changes in RV impedance represented changes in RV stroke volume (SV), conditions known significantly to affect RV SV should be accompanied by significant changes in RV impedance. One week after pacemaker implantation, RV impedance was measured noninvasively during normal respiration in the supine (baseline), left lateral, right lateral, sitting, and standing positions. In addition, all patients performed a Valsalva maneuver test. The amplitude of the impedance signal was different during in‐ and expiration in every body position studied. At baseline, the amplitude of the signal was 18.80 ± 2.24 mm; in the right lateral position 16.75 ± 3.24 mm (P = 0.04) and 17.80 ± 2.35 mm in the left lateral position (P = 0.04). The amplitude of the signal in the sitting position was 16.65 ± 2.89 mm (P = 0.07) and in the standing position 16.95 ± 3.44 mm (P = 0.11). The most impressive change in amplitude was noted during performance of the Valsalva maneuver. During this test the amplitude decreased to 13 ± 2.81 mm and rose to 20 ± 2.66 mm (P = 0.002) afterwards. These results strongly support the assumption that changes of RV impedance as measured by this catheter represent changes in RV SV. This new pacing system is the first pacemaker that reports on the hemodynamic response of every heartbeat by measuring RV impedance.
Variability in the Measurement of Human Ventricular Refractoriness
Authors: KADISH ALAN H. , SCHMALTZ STEPHEN , MORADY FRED
Published: July 2006

The degree of variability in ventricular refractoriness and factors potentially affecting this variability were evaluated in 80 patients undergoing an electrophysiological study. Each of seven variables fstimulation current, coupling interval of the basic drive train to spontaneous rhythm, pause between determinations, bipolar pacing configuration, bipolar vs unipolar pacing, atrioventricular synchrony, and autonomic tone) was evaluated in a group of ten patients to determine its effects on the reproducibility of refractoriness. Measurements were repeated ten times in every patient under each of two conditions. Five variables had significant effects on the reproducibility of measurements. Pacing at 10 mA was associated with less variability in the determination of ventricular refractoriness than pacing at twice threshold (within‐subject variance component 4.5 vs 10.1 msec; P < 0.001). The mean difference between the longest and shortest determinations of refractory periods (range) was 6.2 msec at 10 mA and 8.6 msec at twice threshold. The use of a conditioning period of pacing and continuous trains (eight beats with a 3‐sec pause) rather than a variable pause between serial trials reduced the mean within‐subject variance component from 16.5 to 3.3 (P < 0.001) and the mean range of refractory period determinations from 10.8 to 4.8. The use of the distal rather than the proximal pole as the cathode decreased the mean within‐subject variance component from 9.4 to 3.3 (P < 0.001) and the range of determinations from 6.4 to 5.8 msec. Unipolar pacing was associated with less variability than bipolar pacing (mean within‐subject variance component 4.6 vs 6.4; P < 0.05, mean range 5.0 vs 7.6 msec). In patients with ventriculoatrial dissociation, atrioventricular simultaneous pacing during the basic drive train decreased the within‐subject variance component from 21.2 to 5.7 (P < 0.001) and the mean range of refractory periods from 12.2 to 6.8 msec (P < 0.05). In an eighth group of patients, the significant variables were set to create either the greatest or least variability in refractoriness in order to determine the effects of controlling these factors. Bipolar pacing was used in this group of patients. The within‐subject variance component decreased from 31.7 to 3.5 (P < 0.01) and the mean range of refractory period determinations decreased from 15.8 to 4.4 msec (P < 0.01) when the variables found to affect the reproducibility of refractoriness were set in a fashion to decrease variability. In conclusion: (1) Conventional measurement of ventricular refractoriness often is associated with variability in the range of 10–15 msec (2) Pacing at 10 mA, unipolar rather than bipolar pacing, atrioventricular synchrony during basic drive trains, a large number of trains before refractoriness is reached, and bipolar distal cathodal pacing decrease this variability and provide greater reproducibility in the measurement of ventricular refractoriness.
Epidural Lead Fracture Caused by Material Processing Fault
Authors: VELIMIROVIC DUSAN , RADMILOVIC VELIMIR , DJORDJEVIC MILAN , KOCOVIC DUSAN , KOSTIC DUSAN , PAVLOVIC SINISA
Published: July 2006

Fracture of the epidural lead (Pisces Quad 3487) is documented in four out of eight patients with an implanted Itrel pacing system for treatment of peripheral vascular disease. In two patients, lead fracture was established during x‐ray fluoroscopy. In the remaining two patients, x‐ray examination did not reveal any fracture, due to proximity of the fragments. Microscopic examination of the extracted lead, however, confirmed lead fracture, as well as the presence of tissue fluid and thrombus between the two ends of the spiral shaped lead, but no insulation defect was observed. A cross‐sectional area on the fracture line of the broken lead was examined using scanning electron microscopy. It was found, by tracing the radial marks to their point of convergence, that the initial microcrack started from a large inclusion of the calciumsilicon type at the lead surface. The initial microcrack was propagated by the fatigue mechanism. The presence of a large inclusion at the surface suggests that the main cause of the failure of the investigated epidural leads could be improper fabrication of the material. The high incidence of epidural lead fracture in our group suggests that this complication should be considered as a possible cause of epidural spinal electrical stimulation pacing system dysfunction.
Control of Refractory Ventricular Tachycardia with Biventricular Assist Devices
Authors: GEANNOPOULOS CHRIS J. , WILDER DAVID J. , OLSHANSKY BRIAN
Published: July 2006

A 65‐year‐old man developed incessant ventricular tachycardia following coronary artery bypass grafting while being weaned from cardiopulmonary bypass. The arrhythmia was refractory to procainamide, lidocaine, bretylium, and magnesium. Ventricular tachycardia subsided following reinitiation of cardiopulmonary bypass. Ultimately, the patient required ventricular assist devices to control his arrhythmia. This case is unique as the ventricular assist devices were used not for hemodynamic support, but for arrhythmia control. The mechanism of arrhythmia suppression may be related to contraction‐excitation coupling.
The Right Ventricular Outflow Tract as an Alternative Permanent Pacing Site: Long‐Term Follow‐Up
Authors: BARIN EDWARD S. , JONES SUSAN M. , WARD DAVID E. , CAMM A. JOHN , NATHAN ANTHONY W.
Published: July 2006

The long‐term characteristics of the right ventricular outflow tract have been assessed as an alternative permanent pacing site to the right ventricular apex. Thirty‐three consecutive patients requiring ventricular pacing were randomized to be paced from one of the two sites. Pacing was performed using a screw‐in lead, and a programmable pacemaker was used to facilitate threshold testing. There was no significant difference in the lead positioning time or any acute implant measurement (e.g., threshold at 0.5 msec 0.4 ± 0.2 V for both sites, P = 0.99). Chronic measurements were also comparable during follow‐up (mean 73 months) with a mean threshold at most recent follow‐up of 0.15 ± 0.2 msec (apex) and 0.13 ± 0.21 msec (outflow tract) at 5 V, P = 0,81, There was only one pacing related complication, a lead dislodgment (outflow tract) in a pacemaker twiddler. Overall, both sites were highly satisfactory.
Safety of External Cardioversion/Defibrillation in Patients with Internal Defibrillation Patches and No Device
Authors: PINSKI SERGIO L. , ARNOLD ANITA Z. , MICK MATTHEW , MALONEY JAMES D. , TROHMAN RICHARD G.
Published: July 2006

Placement of prophylactic epicardial defibrillation patches at time of open‐heart surgery in patients at risk for postoperative arrhythmias has been strongly questioned. Concern has centered on the ability to safely perform subsequent external defibrillation if needed. From 61 patients who were treated with a two‐stage strategy we identified 17 who, while wearing epicardial patches and no generator, received external cardioversion/defibrillation for 20 episodes of hemodynamically unstable ventricular arrhythmias. All the patients had one small and one large patch. Eighteen of the episodes were induced during electrophysiological testing (with transthoracic shocks delivered via pad electrodes oriented in an apex‐posterior configuration) and two were spontaneous. The episodes occurred at 21 ± 27 days from patch implant. Thirteen episodes (65%) were converted with one shock at an energy level of 185 ± 65 J. Seven (35%) required a second shock at 351 ± 22 J. The accumulated energy requirement was 286 ± 205 J. No adverse outcomes were noted. The number of episodes requiring more than one shock and the energy requirements were not different from those in a control group of 20 similar arrhythmias treated with the same equipment. Under these conditions, external cardioversion/ defibrillation in patients with one large and one small epicardial defibrillation patch was uniformly successful. Further data is needed in the out‐of‐hospital setting and on the results of external defibrillation in patients with two large patches.
A Simultaneous, Noninvasive Comparison with Sinus Rhythm, of two Activity Sensing, Rate Adaptive Pacemakers, in an Elderly Population
Authors: JOHNSTON SEBASTIAN L. , BRADDING PETER , WATKINS JOHN
Published: July 2006

We compared the rate response to low level work, arm exercise, step testing, and treadmill exercise between the Siemens Sensolog 703 S (Sg) and the Medtronic Activitrax (Ax) pacemakers, and simultaneous sinus rhythm (SR) in an elderly population. In ten subjects mean age 70.6 years, range 49‐81 years, the pacemaker responses were noninvasively compared by strapping the units to the chest wall under constant and equal pressure applied lay an adjustable belt. Pacemaker rates and SR were recorded simultaneously on a three‐channel ECG recorder. The units were programmed in situ to give an increase in rate from 70 beats/min silting, to 100 beats/min after walking at a normal pace for 30 seconds. Programming took three times longer for Sg (P < 0.02). The response to standing and bending was poor for both units (Ax mean 75.5 beats/min, Sg mean 77.6 beats/min), when compared to SR (mean 90.3 beats/min). A 20‐step test resulted in a greater rate response from Ax (mean 105.3 beats/min) than from Sg (mean 96.3 beats/min [P = 0.09]), though both were still less than SR (116.3). There were significant differences between the two pacemakers on treadmill testing, at peak rate achieved (Ax mean 116.5 beats/min; Sg mean 102.7 beats/min [P < 0.005], SR mean 122.5 beats/min) and at end exercise (Ax mean 112.5 beats/min; Sg mean 92.9 beats/min [P < 0.002], SR mean 121.3 beats/min). Arm exercise, however, resulted in a significantly greater response from Sg than Ax (105.1 and 88.5 beats/min, respectively; P < 0.01, SR 98.7 beats/min). For each pacemaker the entire battery of 19 observations (7 exercise parameters and 12 treadmill time points) were analyzed to assess the correlation with SR; Ax was found to correlate very closely with SR (r = 0.94, P < 0.0001), while Sg had a poor correlation with SR (r = 0.40, P < 0.09). In conclusion, Ax was quicker to program and had a much better correlation to SR than did Sg, when programmed as described in the elderly population. Both pacemakers responded poorly to changes in posture, and gave a lower rate response than SR for almost all exercises.
Autonomic Stimulation
Authors: UPTON ADRIAN R.M. , WHITE ANNE M.
Published: July 2006

Therapeutic stimulation of the autonomic nervous system has been limited by Jack of qualitative or quantitative evaluation of autonomic mechanisms. This article provides an historical review of knowledge about autonomic pathways and critical evaluation of available tests of autonomic function. Recent developments in evaluation of autonomic dysfunction and improvement in techniques of neurostimulation have facilitated the development of a number of clinically useful treatments for bladder control, sexual problems, peripheral vascular disease, angina pectoris, and seizure disorders. Future therapeutic measures may allow specific control of hypertension, pain, cardiac arrhythmias, trophic disorders and balance.
Balance and Cognitive Impairment in Two Epileptic Patients Before and After Vagal Nerve Stimulation
Authors: CLARKE B.M. , UPTON A. , GRIFFIN H. , HUDOBA P.
Published: July 2006

Balance and cognition were assessed in two patients with uncontrolled complex partial seizures. The patients were on anticonvulsant medications and were treated with left vagal stimulation. Balance and cognition were assessed be/ore and after vagal stimulation, and the results were compared with age matched controls and older patients with Parkinson's disease. Severe impairments of function were found in the epileptic patients, and such negative effects of medication make vagal stimulation a potentially practical alternative treatment for uncontrolled epilepsy.
The Implantable Neurocybernetic Prosthesis System
Authors: TERRY REESE S. , TARVER W. BRENT , ZABARA JACOB
Published: July 2006

The neurocybernetic prosthesis system (NCP) is an implantable, multiprogrammable pulse generator that delivers constant current electrical signals to the vagus nerve for the purpose of reducing the frequency and severity of epileptic seizures. The signals are delivered on a predetermined schedule, or may be initiated by the patient with an external magnet. The device is implanted in a subcutaneous pocket in the chest just below the clavicle, similar to pacemaker placement. The stimulation signal is transmitted from the prosthesis to the vagus nerve through a lead connected to an electrode which is a multi‐turn silicone helix, with a platinum band on the inner turn of one helix. The prosthesis can be programmed with any IBM‐ compatible personal computer using NCP software and a programming wand.
Vagal Stimulation Reduces the Severity of Maximal Electroshock Seizures in Intact Rats: Use of a Cuff Electrode for Stimulating and Recording
Authors: WOODBURY J. WALTER , WOODBURY DIXON M.
Published: July 2006

J. Zabaru showed thai repetitive vagal stimulation (VS) prevents or ameliorates convulsive seizures in dogs. We have studied the effects of VS on maximal electroshock seizures (MES) in intact rats: (1) A 5 wire cuff electrode was developed for stimulating and recording from the vagus. Compound action potentials (AP) were recorded and strength‐duration curves obtained for A and C fibers. There is a monotonic relationship with a negative slope between heart rate (HR) and AP amplitude. C fibers remain excitable for 25 days after cuff implant. (2) The anticonvulsant efficacy of VS is directly related to the fraction of vagal C fibers stimulated and the frequency of stimulation. (3) The anticonvulsant efficacy of VS has been established using two rat models of human epilepsy. VS abolishes the extensor component of the tonic phase of a MES and shortens or prevents tonic seizures induced by pentylenetetrazol (PTZ). (4) VS appears to act via release of large quantities of the inhibitory mediators GABA and glycine throughout large volumes of the brain. (5) It is rational to test VS in man as a treatment for intractable seizures.
Vagal Stimulation for Control of Complex Partial Seizures in Medically Refractory Epileptic Patients
Authors: WILDER B.J. , UTHMAN BASIM M. , HAMMOND EDWARD J.
Published: July 2006

Chronic intermittent stimulation of the vagus nerve is a new method currently being tested for the treatment of medically intractable complex partial seizures (CPS). We have studied the effects of vagal stimulation in nine patients with CPS for 4–16 months to determine its safety and efficacy. With the patients maintained on constant dosages of antiepileptic drugs, we recorded the electroencephalogram and electrocardiogram, and performed clinical laboratory tests and gastric analysis over a 6‐week baseline period. The neurocybernetic prosthesis (NCP) was then implanted and connected to two spiral electrodes wound around the left vagus nerve. After a 4‐week placebo period, vagal stimulation was started. Stimulation parameters were increased stepwise at monthly intervals until patients were being stimulated for 30‐second periods at 20‐50 Hz with 1‐2 mA of current at 250‐500‐μsec pulses. A second 4‐week placebo period was added 3 months after the implantation. Thereafter, vagal stimulation was resumed and self‐stimulation with magnetic activation was allowed for a 1‐minute period at the onset of an aura. Six patients had a significant reduction in the frequency, intensity, or duration of seizures. All patients tolerated the implantation and stimulation well and none reported pain, discomfort, or important changes in their daily activities, sleep habits, eating, swallowing, or breathing. There were no remarkable changes in blood pressure or heart rate.
Characterization and Modification of Brain Activity with Deep Brain Stimulation in Patients in a Persistent Vegetative State: Pain‐Related Late Positive Component of Cerebral Evoked Potential
Authors: KATAYAMA YOICHI , TSUBOKAWA TAKASHI , YAMAMOTO TAKAMITSU , HIRAYAMA TERUYASU , MIYAZAKI SHUHEI , KOYAMA SEIGOU
Published: July 2006

A series of eight patients in a persistent vegetative state (PVS) were subjected to chronic deep brain stimulation (DBS) for the purpose of promoting recovery from the PVS. The characteristics of the brain activity in these patients were evaluated from the late positive component of the cerebral evoked potential in response to painful stimuli (pain‐related P250). While any neurological scoring system for the comatose state includes evaluations of motor reactions to painful stimuli, the pain‐related P250 is unique in terms of its ability to assess the cortical responsiveness to painful stimuli directly and quantitatively without involving functions of the motor system. It was found that the pain‐related P250 was more or less depressed in patients in a PVS. It was repeatedly demonstrated in four patients, however, that the pain‐related P250 could be transiently increased by preceding stimulation of the mesencephalic reticular formation. Furthermore, a persistent increase in the pain‐related P250 was produced in these four patients following chronic DBS of the mesencephalic reticular formation or nonspecific thalamic nuclei for more than 6 months, and this was correlated with the clinical improvements. These results imply that responsiveness at the cortical level to pain is depressed in the PVS. It also appears that some fraction of the depression may, however, be functionally produced and potentially reversible.
Treatment of Cerebral Ischemia with Electrical Stimulation of the Cervical Spinal Cord
Authors: HOSOBUCHI YOSHIO
Published: July 2006

We observed an increase in cerebral blood flow (CBF) for control of pain but were otherwise normal. Based on (hat observation, we implanted stimulators for cervical spinal cord stimulation (cSCS) in three patients who had symptomatic cerebral ischemia. Two had severe basivertebral occlusive disease and one had bilateral carotid occlusive disease. In all three cases, cSCS alleviated the symptoms of ischemia. Xenon‐CBF studies or single‐photon emission computer tomography (SPECT) showed increased CBF in response to cSCS. Although no mechanism clearly responsible for this remarkable therapeutic efficacy can be proposed yet, further clinical trials of cSCS for inoperable cerebral ischemia may be justified.
Cerebral Hemodynamics During Spinal Cord Stimulation
Authors: MEGLIO MARIO , CIONI BEATRICE , VISOCCHI MASSIMILIANO
Published: July 2006

An increase of cerebral blood flow (CBF) during spinal cord stimulation (SCS) has been shown in man using the 133Xenon inhalation technique. We report the effects of SCS on cerebral hemodynamics studied with transcranial Doppler sonography (TCD). Twenty‐six patients with epidural electrodes implanted at the cervical level (11 patients) and at the thoracic level (15 patients) were investigated with recordings of CBF velocity in the middle cerebral arteries before and during SCS, Sixty‐three and two‐thirds percent of patients with cervical stimulation and 29.4% of patients with thoracic stimulation showed a decrease afcerebral vas‐cularresistance simultaneously with an increase of the velocity of CBF.
Successful Percutaneous Extraction of a Chronic Left Ventricular Pacing Lead
Authors: TROHMAN RICHARD G. , WILKOFF BRUCE L. , BYRNE TIMOTHY , COOK SEBASTIAN
Published: July 2006

This report describes a patient with a chronic endocardial left ventricular pacing lead. To avoid the risk of future embolization, it was felt that the lead should be removed and right ventricular pacing established. The lead was carefully evaluated by transesophageal echocardiography to exclude adherent thrombus. Successful percutaneous lead extraction was accomplished without sequelae, thus avoiding the morbidity of a thoracotomy.
A Case of a Pseudomalfunction of a DDD Pacemaker
Authors: AJIKI KOHSUKE , SAGARA KOUICHI , NAMIKI TAKAO , ISHIBASHI HIROSHI , IINUMA HIROYUKI , FU LON TAI , KATO KAZUZO
Published: July 2006

DDD pacemaker pseudomalfunction occurred in a 65‐year‐old man. This was due to premature ventricular contraction (PVC) response option and cross‐talk detection window, which are designed to protect against pacemaker related tachycardia or cross‐talk. Pseudomalfunction disappeared by eliminating PVC response option.
Repetitive Nonsustained Monomorphic Ventricular Tachycardia Aborted by Methoxamine and Sleep “Heart Rate Dependent Ventricular Tachycardia”
Authors: OHE TOHRU , TAKAGAKI KENJI , SHIMOMURA KATSURO
Published: July 2006

Methoxamine, an alpha adrenorecep‐tor agonist, and sleep abolished repetitive nonsustained monomorphic ventricular tachycardia in a 41‐year‐old man without detectabJe underlying heart disease. Detailed pacing studies revealed that the occurrence of ventricular tachycardia was totally dependent on the basic heart rate. Sleep and the alpha adrenoreceptor agonist abolished the ventricular tachycardia by slowing the basic heart rate. Verapmil, propranolol, and disopyramide were able to decrease the upper limit of the tachycardia‐initiating heart rate, but none of them were able to increase the lower limit (75/min). Failure to increase the Jower limit of the tachycardia‐initiating heart rate was a major reason why these conventional antiarrhythmic drugs were unable to suppress his daytime episodes of repetitive ventricuJar tachycardia.
Effects of Body Constitution and Age on Maximum Pacing Rate of Activity‐Modulated Rate Responsive Pacemakers
Authors: SCHUCHERT ANDREAS , KUCK KARL‐HEINZ , BLEIFELD WALTER
Published: July 2006

The pacing rate of activity‐modulated pacemakers is triggered by vibrations running through the body. Whether the body constitution predicts maximum pacing rate and may facilitate rate response programming was studied in 16 patients with Activifrax pacemakers. Rate response parameters were programmed to a fixed setting in VVIR/VOOR mode (lower pacing rate 60 ppm, upper pacing rate 125–130 ppm, activity threshold medium/7). Body vibrations were induced by a treadmill exercise test with increasing speed. Maximum pacing rates were measured al the stage of symptom‐limited tolerance. Exercise tests with a duration of 7.3 ± 2.9 minutes resulted in a maximum pacing rate of 98 ± 22 ppm ranging from 60–122 ppm. Maximum pacing rates did not differ between male (n = 10; 102 ± 21 ppm) and female (n = 6; 92 ± 24 ppm). Correlations between maximum pacing rates and body constitutional factors were not significant with r = ‐0.15 (weight), r = 0.39 (height), r = 0.07 (body surface area), and r = ‐0.27 (skin‐fold thickness). The correlations with body mass index (r = ‐0.53) and age (r = ‐0.53) were initially significant, but not after Bonferroni‐Simes‐Hommel correction. The age‐dependent relationship may be caused by the shorter exercise duration of older patients indicated by the correlation between exercise duration and maximum pacing rate (r = O.77), as well as with age (r = ‐0.73). Conclusions: body constitution did not modify body vibrations and did not allow prediction of maximum pacing rates; therefore, it is no aid for the programming of rate response parameters.
Prehospital Transcutaneous Cardiac Pacing for Symptomatic Bradycardia
Authors: HEDGES JERRIS R. , FEERO STAN , SHULTZ BETTE , EASTER RICH , SYVERUD SCOTT A. , DALSEY WILLIAM C.
Published: July 2006

We studied patients with symptomatic bradycardia to determine the importance of presenting hemodynamic status and prehospital transcutaneous cardiac pacing (TCP) upon patient survival. Of 51 patients with witnessed cardiovascular decompensation and initial bradycardia, 27 (53%) received TCP. There were no significant differences between the paced patients and those without TCP for mean times from collapse until cardiopulmonary resuscitation, paramedic arrival and a paceable rhythm, or from paramedic arrival until a paceable rhythm. Overall, emergency department arrival with a palpable pulse (26% in paced vs 13% in nonpaced group; P = 0.20) and survival to hospital discharge (15% in paced vs 0% nonpaced group; P = 0.07) tended to be better for the paced group. No patient without a palpable pulse on paramedic arrival survived to leave the hospital. Of patients with a palpable pulse upon paramedic arrival, survival to hospital discharge was greater for the paced group (80% in paced vs 0% in nonpaced group; P = 0.024). TCP appears to be most beneficial in those patients with bradycardia who have a palpable pulse when first seen.
Association of Humps on Monophasic Action Potentials and ST‐T Alternans in a Patient with Romano‐Ward Syndrome
Authors: SAKURADA HARUMIZU , TEJIMA TAMOTSU , HIYOSHI YASUNAGA , MOTOMIYA TAKESHI , HIRAOKA MASAYASU
Published: July 2006

A case of Romano‐Ward syndrome had episodes of torsade de pointes preceded by ST‐T alternans. ST‐T alternans was induced by isoproterenol and abolished by verapamil, lidocaine, mexiletine and MgSO4. A monophasic action potential (MAP) showed humps in MAPs at the right ventricular outflow tract but not at the right ventricular apex in alternate beats. Differences in the MAP duration were noted between the two areas and were associated with ST‐T alternans. Atrial pacing abolished both humps and ST‐T alternans. These results suggest that humps are a possible re/lection of early afterdepolarizations and their appearance is limited to localized regions of the ventricles, which produces regional disparity of repolarization and ST‐T alternans.
Hypothesis Testing as an Approach to the Analysis of Complex Tachycardias—an Illustrative Case of a Preexcitation Variant
Authors: TEO WEE SIONG , YEE RAYMOND , KLEIN GEORGE J. , GUIRAUDON GERARD M. , LEITCH JAMES W.
Published: July 2006

The correct elucidation of the electrophysiologirul substrule and mechanism (s) responsible for a complex arrhythmia requires a systematic approach to the analysis of the electrophysiological data. One approach calls for the formulation of a set of hypotheses that could explain the data obtained during the study. The hypotheses are then tested for compatibility with phenomena observed and the one that agrees with the majority of the findings would represent the most tenable explanation. We present the case of a young girl with a wide QRS complex tachycardia and a history of ventricular preexcitation that illustrates this approach. The complexities were resolved only after intraoperative analysis and surgical ablation of a right‐sided accessory pathiway with decremental properties, and provides further insight into our understanding of the nodoventricular Mahaim fiber.
In Vivo and In Vitro Studies of a Chronic Oxygen Saturation Sensor
Authors: SEIFERT GEORGE PHILIP , MOORE ALAN A. , GRAVES KEN L. , LAHTINEN STUART P.
Published: July 2006

An oxygen saturation sensor, for the purpose of chronically controlling the heart rhythm produced by a pacemaker, should be specific to oxygen saturation and should be minimally affected by the harsh blood environment. For the sensor type we tested we found: (1) one sensor failure in 205.5 canine‐months of chronic implantation (n = 11, range 4 to 50 months); (2) hematocrit‐induced error of < 5 percentage points of Svo2 over the range of 50% to 80% Svo2 and 15% to 45% hematocrit; (3) carboxyhemoglobin (HbCO)‐induced error of < 4 percentage points of Svo2 with HbCO up to 20%; (4) a fibrotic sheath‐induced error of < 3 percentage points of Svo2 in the range of 50% to 80% Svo2 due to fibrotic sheath thicknesses up to 0.22 mm; (5) no significant error induced by velocity variations local to the sensor; (6) no significant error due to temperature in the range of 30° to 42°C; and (7) that the sensor could be as close as 0.3mm to the ventricular wall and still only produce an error of 5% Svo2.
Retrograde (Ventriculoatrial) Conduction in Congenital Complete Heart Block
Authors: ZILO PHILIP , GROSS JAY N. , ANDREWS CAROLYN A. , FURMAN SEYMOUR
Published: July 2006

Retrograde ventriculoatrial (VA) conduction is documented at the time of dual chamber pacemaker Implantation in a 36‐year‐old patient with congenital complete atrioventricular (AV) block. Programmed ventricular stimulation with stimuli of increasing prematurity demonstrated a lack of decremental conduction via a unidirectional retrograde pathway. Because retrograde VA conduction has been associated with pacemaker mediated endless loop tachycardia, the status of retrograde conduction should be assessed in all patients undergoing dual chamber pacemaker implantation, including those with congenital complete AV block who have previously been considered to have no conductive tissue between atria and ventricles.
Congenital Myocardial Sympathetic Dysinnervation (CMSD)—A Structural Defect of Idiopathic Long QT Syndrome
Authors: GÖHL KONRAD , FEISTEL HERBERT , WEIKL ANDREAS , BACHMANN KURT , WOLF FRIEDRICH
Published: July 2006

Concerning the path genetic mechanism of idiopathic long QT syndrome (LQTS), the hypothesis of a specific sympathetic imbalance has gained general acceptance, but its validity has never been proven. To test this hypothesis I‐123‐MIBG, an analogue of norepinephrine and guanethi‐dine, was used to provide scinfigraphic display of the efferent cardiac sympathetic innervation. Twelve members of four LQTS families fmean age 38.2 ± 17.2 years, eight males) and eight healthy volunteers (mean age 48.2 ± 13.3 years, five males) were studied by means of M23‐MTBG single photon emission computed tomography (SPECT). A quantitative analysis of all scans was performed. All scans of the healthy volunteers show a uniform tracer uptake with sometimes slightly decreased activity in the apex. (1) All patients with QTc > 440 msec (n = 5); (2) all, who had suffered from at least one episode of torsade de pointes, ventricular fibrillation (VF) or syncope (n = 5); and (3) all symptomatic patients with QTc prolongation (n = 4) have reduced or abolished (P < 0.02) MIBG uptakes in the inferior and inferior septal parts of the left ventricle (congenital myocardial sympathetic disintegration [CMSD]). Additionally, one female without symptoms or QTC prolongation (LQT) shows an abnormal MIBG SPECT similar to the one of her daughter, who has LQT and symptoms. One male without LQT, who had suffered from VF shows CMSD similar to his father, who has LQT, but no symptoms. All members of the families with normal MIBG SPECTs have neither LQT nor symptoms. In all families CMSD fulfills the criteria of autonomic‐dominant inheritance. Normal QTc‐interval predicted only in 57% normal cardiac sympathetic enervation in the present LQTS families. Therefore, quantitative I‐123‐MIBG SPECT enables to identify myocardial sympathetic disintegration as structural defect in LQTS. CMSD is associated with and without LQT and presents a pattern of autosomal‐dominant inheritance. LQT at rest or during exercise was specific (100%). but less sensitive (63%) in the assessment of CMSD than I‐123‐MIBG SPECT.
Persistent Left Superior Vena Cava: A Problem in the Transvenous Pacing of the Heart
Authors: DOSIOS T. , GORGOGIANNIS D. , SAKORAFAS G. , KARAMPATSAS K.
Published: July 2006

Transvenous pacemaker implantation was impossible from the right side in a patient with persistent left superior vena cava (PLSVC) as the two cavae communicated via the coronary sinus and entry into (he right heart could not be achieved. Epicardial pacing was instituted.
Intraoperative Myocardial Infarction during Open‐Heart Ablation of an Atrioventricular Accessory Pathway
Authors: GIUDICI MICHAEL C. , FLAKER GREGORY C. , CURTIS JACK J.
Published: July 2006

We report a patient who suffered an intraoperative AMI from injury to the distal portion of a dominant left circumflex coronary artery in the atrioventricular groove. Depending upon coronary anatomy and location of accessory pathways, compromise of coronary circulation by nonintrinsic pathology can be a major cause of morbidity.
Effect of Atrial Pacing on the Frequency of Tachycardia in Patients with Recurrent Junctional Tachycardia
Authors: MURPHY PHILIP , O'KEEFFE D. BARRY
Published: July 2006

In order to assess whether atrial pacing reduced the frequency of tachycardia in patients with recurrent functional tachycardias, ten patients with recurrent junctional tachycardias with atrial Intertach antitachycardia pacemakers in situ were paced in a random order in atrial demand mode at 50 ppm (AAI 50), 80 ppm (AAI 80), and 100 ppm (AAI 100) for a period of up to I month. The numbers of tachycardias detected by the pacemaker over this period were recorded and compared with the number seen when unpaced (DDD). Correct arrhythmia detection by the pacemaker was confirmed by Holler monitoring. The number of tachycardias in 000 was 44.7 ± 19.8 (mean ± SEMJ. No significant reduction in tachycardia frequency was seen in any pacing mode. Back‐up atrial pacing at 50 ppm tended to reduce the frequency of tachycardias (32.3 ± 12.8 tachycardias; P = 0.06). The higher pacing rates increased the number of tachycardias (AAI 80; 57.1 ± 24.6 tachycardias, P = 0.20: AAI 100; 81.8 ± 30.2 tachycardias; P = 0.31). Symptoms increased with each pacing mode and palpitations were statistically more severe in AAI 100 mode. Four patients had disabling symptoms at this rate and had to drop out. Atrial back‐up pacing may be of use in some patients with functional tachycardia, but overdrive pacing is not helpful.
The Role of Combination Therapy with Mexiletine and Procainamide in Patients with Inducible Sustained Ventricular Tachycardia Refractory to Intravenous Procainamide
Authors: WIDERHORN JOSEF , SAGER PHILIP T. , RAHIMTOOLA SHAHBUDIN H. , BHANDARI ANIL K.
Published: July 2006

This study evaluated the role of serial electropharmacological testing on combination therapy with mexiletine and procainamide in 20 patients with inducible sustained ventricular tachycardia (VT) refractory to intravenous procainamide. The clinical arrhythmias were cardiac arrest in five patients, sustained VT in 11 patients, and recurrent syncope of presumably arrhythmic origin in four patients. The mean left ventricular election fraction (LVEF) was 0.40 ± 0.12 (mean ± SD). All patients had inducible sustained VT at baseline and after administration of intravenous procainamide. All 20 patients underwent elec‐tropharmacological testing on combination therapy with mexiletine and procainamide. The mean cycle length of inducible sustained VT was 251 ± 48 ms at baseline, 324 ± 81 ms on intravenous procainamide (P < 0.014 vs baseline), and 365 ± 82 ms on combination therapy (P < 0.0001 vs baseline, P = NS vs intravenous procainamide). Combination therapy did not suppress VT inducibility, nor did it make VT more difficult to induce in 19 of 20 patients. The remaining one patient had a partial response (runs of nonsustained VT, longest 10 seconds). Furthermore, combination therapy did not significantly prolong the VT cycle length over and above that observed during testing with intravenous procainamide. Therefore, in patients with inducible sustained VT refractory to procainamide during initial electropharma‐cological testing, mexiletine in combination with procainamide appears to be of little or no value and serial electropharmacological testing on these drugs is of limited usefulness. Early initiation of alternative therapy may be the preferred clinical option.
Identification of Ventricular Tachycardia Using Intracardiac Electrograms: A Comparison of Unipolar Versus Bipolar Waveform Analysis
Authors: GREENHUT SAUL E. , DICARLO LORENZO A. , JENKINS JANICE M. , THRONE ROBERT D. , WINSTON STUART A.
Published: July 2006

Implantable antitachycardia devices suffer a high false‐positive rate of delivery of therapy because current detection schemes based upon ventricular rate and rate variations are excessively sensitive at the cost of specificity. Several methods have been proposed for providing complementary information derived from morphologic analysis of intraventric‐ular electrograms in order to increase specificity. The majority of these techniques have utilized bipolar electrogram analysis to detect changes in ventricular activation indicative of ventricular tachycardia. Whether bipolar or unipolar intracardiac electrogram analysis might be preferred for discriminating ventricular tachycardia from sinus rhythm has not been determined. In this study, a previously demonstrated method for identification of ventricular tachycardia using intracardiac electrograms, correlation waveform analysis, was used to analyze both unipolar and bipolar signals during sinus rhythm and ventricular tachycardia recorded during electrophysiology studies of 15 patients with inducible sustained monomorphic ventricular tachycardia. Correlation waveform analysis consistently discriminated between all depolarizations during ventricular tachycardia in 14/15 patients (93%) using either electrogram configuration; 13 of the 14 patients were common to both groups. Of these patients, 8/15 (53%) had greater separation between sinus rhythm and ventricular waveforms with bipolar electrogram analysis while 7/15 (47%) had greater separation with unipolar electrogram analysis. We conclude that morphologic analysis of unipolar and bipolar electrograms may be equally effective in distinguishing ventricular tachycardia from sinus rhythm. For individual patients, either a unipolar or bipolar ventricular configuration may be preferable, and should be chosen on a patient‐specific basis during electrophysiology study prior to antitachycardia device implantation.
A Multicenter Evaluation of a Single‐Pass Lead VDD Pacing System
Authors: CURZIO GIUSEPPE
Published: July 2006

Since June 1985 until April 1989, 237 patients (130 males, 107 females, aged 22 to 95 years, mean 71) with symptomatic AV conduction disturbances and competent sinus node, were implanted with a single‐pass lead VDD pacing system in 30 centers and followed‐up for at least 6 months. The ventricular pacing lead incorporated two atrial ring 3‐cm apart electrodes, positioned within the right atrial cavity without contact with the heart wall, in order to detect the atrial activity, which is differentially processed fay the pacemaker. At implant, mean atrial electrogram amplitude, derived from a custom pacemaker system analyzer (PSA) with the same input filter of the pacemaker was 1.7 ± 0.8 mV (n = 93). In all cases, atrial sensitivity at implant was the default value ±0.15 mV, The atrial tracking capability of the pacing systems was assessed within the month and every 6 months after implantation by means of clinical evaluation, resting ECG, 24‐hour Holter monitoring and the following tests: exercise stress testing, mental stress, isometric exercise, and nitedipine test. These tests evoke an increase of atrial rate in consequence of metabolic needs or as a reflex response. The criterion used to evaluate the correct operation of the system was the percentage of atrial synchronization. This was defined as the ratio between atrial triggered ventricular paced complexes and all ventricular paced complexes. All monitorings showed a ratio higher than or equal to 98% in a percentage of patients not lower than 95%. Mean follow‐up was 385 days (range 183–1,370 days). During follow‐up, atrial sensitivity was never reprogrammed and inappropriate triggered pacing due to mvopotential activity was never noted in any tests.