bluuebunny/crossref_metadata_2025 huggingface dataset:
Catheter Ablation for Control of Ventricular Tachycardia: A Report of the Percutaneous Cardiac Mapping and Ablation Registry
Authors: EVANS G. THOMAS , SCHEINMAN MELVIN M. , SCHEINMAN MELVIN M. , ZIPES DOUGLAS P. , BENDITT DAVID , CAMM A. JOHN , EL‐SHERIF NABIL , FISHER JOHN , FONTAINE GUY , GERMAN LARRY , HARTZLER GEOFFREY , JOSEPHSON MARK , MORADY FRED , RUSKIN JEREMY
Published: July 2006

Catheter ablation of ventricular tachycardia is a procedure of last resort in critically ill patients. The Percutaneous Cardiac Mapping and Ablation Registry was able to collect data on 88 patients undergoing ablation of ventricular tachycardia foci. The mean following interval for the group was 10 ± 8 months. Results were divided into three categories: Group I patients remained asymptomatic and were on no antiarrhythmic medications (33%); Group II remained asymptomatic and took antiarrhythmic agents (38%): Group III patients were considered unsuccessful and consisted of 29 percent of the total. More than one‐third of patients received two shocks; the remainder received from one to five shocks. Overall mortality included four procedure‐related deaths and total follow‐up mortality was 25 percent. Catheter ablation for ventricular tachycardia should he undertaken only in highly specialized centers with an expert and experienced electrophysiologist with immediate surgical back‐up available.
An Experimental Device for Low‐Energy, Precise Ablation of AV Conduction
Authors: TARIAN PETER , BOVEJA BIRINDER , COHEN DONALD , JOUBERT THOMAS , ZALEWSKI EILEEN
Published: July 2006

A combination suction catheter‐bipolar lead system permits precise ablation of AV conduction with low energy. The electrode is positioned to maximize the bipolar His potential, then to maximize the HP between the lip and a surface electrode. With the tip held in place by 100–200 mmHg of suction, this site is paced. If the St‐V interval is short and the ventricular morphology is similar to a sinus beat, a shock of 10 or 20 J is delivered. If complete heart block does not result, additional shocks are delivered. The device was used in eight dogs. When the St‐V was close to the unpaced H‐V interval, a shock of 20 J always produced permanent CHB. In contrast, an initial shock of 10 J always failed, and more shocks of up to 30 J were required to produce CHB which, even then, did not always persist. At 60 days the hearts were healed with a round, white, dense scar of about 2 mm in diameter just above the leaflet of the tricuspid valve. This device can produce permanent dissociation of the atria and ventricles with a shock of 20 J. It also enables precise positioning of the electrode.
Cryosurgery in Tachycardia Treatment
Authors: BREDIKIS J.J. , BUKAUSKAS F.F. , LEKAS R.I. , SAKALAUSKAS J.J. , BREDIKIS A.J. , LAURUSHONIS K.A. , PUTELIS R.A. , TURKEVICHIUS G.S.
Published: July 2006

Cryosurgical techniques have become established and acceptable therapy in the treatment of resistant arrhythmias. In this report, both experimental and clinical data are presented describing the results of various cryosurgical techniques used at the Cardiac Rhythm Disturbance Center in Lithuania, USSR.
Hysteresis in the Human RR‐QT Relationship During Exercise and Recovery
Authors: SARMA JONNALAGEDDA S.M. , VENKATARAMAN K. , SAMANT DINESH R. , GADGIL UDAY
Published: July 2006

The present study was undertaken to test the hypothesis that the human RR‐QT relationship during dynamic exercise diners markedly from that during the recovery phase. Fourteen subjects from the age of 16 to 71 years exercised on a treadmill according to the Bruce protocol. Electrocardiograms were recorded continuously on a magnetic tape, from 1 minute before exercise to 10 minutes into recovery. An exponential formula, proposed by us earlier, closely represented the exercise RR‐QT data. However, it was not appropriate for the often S‐shaped recovery curves which invariably deviated from the exercise curves, exhibiting hysteresis. Initially, all recovery QT intervals were shorter than the exercise values, but later in the recovery, some crossed the exercise curves from below, resulting in longer QT intervals. The recovery data were fitted by a third degree polynomial, and the hysteresis was calculated as the area between the exercise and recovery curves within a 150 ms range of the RR interval starting from its minimum value. The mechanisms for the occurrence of hysteresis are likely to involve the sympatho‐adrenal activity in the early post‐exercise period and the time course of QT interval adaptation to rapid changes in the RR interval.
Effect of Propranolol on Ventricular Rate During Atrial Fibrillation in the Wolff‐Parkinson‐White Syndrome
Authors: MORADY FRED , DICARLO LORENZO A. , BAERMAN JEFFREY M. , DE BUITLEIR MICHAEL
Published: July 2006

Atrial fibrillation was induced during an electrophysiology study in 10 patients with the Wolff‐Parkinson‐White (WPW) syndrome, after determination of baseline properties of the accessory atrioventricular (AV) connection; intravenous propranolol (0.2 mg/kg) was then administered. Atrial fibrillation terminated during the drug infusion in three patients, allowing determination of propranolol's effects on conduction and refractoriness during sinus rhythm, before atrial fibrillation was reinduced. In these three patients propranolol had no effect on refractoriness or conduction properties of the accessory AV connection during sinus rhythm. The mean ventricular rate during atrial fibrillation was slowed by 15–56 beats/min in six patients, had no effect on the mean rate in three patients, and markedly increased the ventricular rate (203 to 267 beats/min) in one patient. In this patient, 54% of QRS complexes during atrial fibrillation were narrow, compared to 0–25% in the other patients. Propranolol reduced the percentage of QRS complexes that were narrow from 13 ± 16% to 1 ± 2% (mean ± standard deviation, p < 0.05). We conclude that propranolol may slow the ventricular rate during atrial fibrillation in some patients with the WPW syndrome, probably by blockcing the effects of adrenergic activation. However, propranolol should not be used in patients with the WPW syndrome who have atrial fibrillation, if most QRS complexes during atrial fibrillation are preexcited. When a large percentage of QHS complexes are narrow, propranolol may increase the ventricular rate, probably by eliminating concealed retrograde conduction in the accessory AV connection.
Cardiac Activation During External Cardiac Pacing
Authors: FALK RODNEY H. , NGAI STEPHEN T.A. , KUMAKI DAVID J. , RUBINSTEIN JEFFREY A.
Published: July 2006

To determine which cardiac chambers are stimulated during external cardiac pacing we performed external pacing in eight normal volunteers while recording the esophageol electrogram. All subjects demonstrated evidence of pacing, which was ventricular in each case. The atrium was frequently activated retrogradely during pacing. We conclude that external cardiac pacing selectively stimulates the ventricle and is thus not of value for noninvasive atrial pacing studies.
A Time‐Related Study by Doppler and M‐Mode Echocardiography of Hemodynamics, Heart Size, and AV Valvular Function During Activity‐Sensing Rate‐Responsive Ventricular Pacing
Authors: FAERESTRAND SVEIN , OHM OLE‐JØRGEN
Published: July 2006

Noninvasive Doppler and M‐mode echocardiography were used to: measure stroke volume (SV), left atrial (LA) size, left ventricular end‐diastolic (EDD), end‐systolic dimensions (ESD), left ventricular fractional shortening (FS), and for determination of mitral and tricuspid insufficiency (MI and TI) before starting and after 1, 3, and 6 months of rate‐responsive ventricular pacing (RRP). The study group consisted of 13 patients (mean age, 75 years) who could be expected to benefit from an increase in cardiac output mediated by an increment of heart rate during exercise. In VVI + activity mode (RRP), the pacemaker was programmed to a basic heart rate of 60 and a maximum heart rate of 125 bpm. The SV at rest was 71 ± 5 before RRP, and fell to 57 ± 4 after 3 months (p < 0.05) and to 53 ± 4 ml/beat after 6 months of RRP (p < .01). The LA size and ESD were unchanged during follow‐up. The EDD decreased from 6.2 ± 0.3 to 5.4 ± 0.2 (p < 0.002) during the first 6 months of RRP. The FS was reduced from 33 ± 4 to 27 ± 3% (p < 0.02) during the first 6 months of RRP. Four of 6 patients treated previously with a VVI pacemaker (mean duration, 9 years) had MI + TI, and 3 of the 7 patients not paced previously had MI hefore RRP. In the last group, 1 new patient developed MI, 1 new patient deveioped MI + TI, and 2 patients who had MI also developed TI within 6 months of pacing. Thus, of 13 patients, 9 (69%) had either MI or MI + TI.
Radiation Damage to Pacemakers from Radiotherapy
Authors: VENSELAAR J.L.M. , VAN KERKOERLE H.L.J.M. , VET A.J.T.M.
Published: July 2006

The literature shows that radiation treatment with a high dose of ionizing radiation is becoming an increasing risk for patients with a pacemaker. In our investigation, 23 pacemakers were subjected to a destructive radiation test. of these 23, five proved unable to withstand a dose of 70 Gy. One pacemaker failed at a dose of only 13 Gy. Our results are compared with those reported in other recent publications. Analysis of the data shows that the CMOS electronic device, which is currently used in practically all pacemakers, is responsible for the high sensitivity to ionizing radiation. We conclude that direct irradiation of the pacemaker is contraindicated in all cases.
Permanent Pacemaker Implantation in a Pregnant Woman with the Guidance of ECG and Two‐Dimensional Echocardiography
Authors: GÜLDAL MUHARREM , KERVANCIOĞLU CELAL , ORAL DERVIŞ , GÜREL TÜRKAN , EROL ÇETIN , SONEL AHMET
Published: July 2006

A 30‐year‐old pregnant woman was admitted to the Cardiology Research Center with syncope, dizziness, and fatigue on exertion. On ECG complete atrioventricular block was diagnosed. Permanent pacemaker implantation was performed with the guidance of ECG and two‐dimensional echocardiography and without the use of fluoroscopy.
An Algorithm for the Electrocardiographic Localization of Accessory Pathways in the Wolff‐Parkinson‐White Syndrome
Authors: MILSTEIN SIMON , SHARMA ARJUN D. , GUIRAUDON GERARD M. , KLEIN GEORGE J.
Published: July 2006

Accessory pathway location in the Wolff‐Parkinson‐White syndrome influences the success and morbidity of nonpharmacological therapies, so that an estimate of accessory pathway location is relevant to the practicing physician. We derived an algorithm for accessory pathway localization based on the surface electrocardiogram; we tested it in a population of 141 patients with the Wolff‐Parkinson‐White syndrome in whom accessory pathway localization was made by electrophysiological and/or intraoperative mapping. The goal of the algorithm was to localize the accessory pathway to one of four anatomic regions, namely, left free wall, posteroseptal, anteroseptal or right free wall by using a simple, easy‐to‐appiy scheme. Each of two observers, blinded to the results of mapping, correctly identified the anatomic location of 91% and 90% of pathways, respectively. We conclude that a simple algorithm utilizing the 12‐lead electrocardiogram can provide a valuable first approximation of accessory pathway location in the Wolff‐Parkinson‐White syndrome.
Complications of Permanent Transvenous Cardiac Pacing: A 14‐Year Review of all Transvenous Pacemakers Inserted at One Community Hospital
Authors: HILL PHILIP E.
Published: July 2006

Five hundred and eighty‐nine consecutive transvenous pacemakers implanted between January 1, 1971 and January 1, 1985 were reviewed. A complication incidence of 17% early in the study period (1971–1977) was caused by electrode displacement and perforation. As of 1975, smaller‐sized electrodes with endocardial fixation were used and were associated with a significant decrease in this complication incidence to 2% by 1985. All other complications occurring during the entire study period (1971–1985) occurred at a frequency of 3% (20/589). Infection occurred in 3 of 589 cases; there were no extrusions or erosions. No mortality was attributed to pacemaker insertion. The “twiddler” syndrome seems to be increasing in frequency. Transvenous permanent pacing can be accomplished today with a low complication rate of 5% or less. The majority of these complications are minor and can be corrected easily. Our studies suggest that the reduced complication incidence is mainly related to improved technology.
Permanent Cardiac Pacemaker Implant in the Fetal Lamb
Authors: SCAGLIOTTI DANIEL , SHIMOKOCHI DENISE D. , PRINGLE KEVIN C.
Published: July 2006

To investigate the feasibility of permanent cardiac pacing in the fetal lamb, we attempted five implants in lambs between 100 and 115 days of gestation. The lambs were approached by a left thoracotomy done through a transverse hysterotomy in the ewe. An epicardial lead was fixed to the left ventricle. Pacing parameters were measured and the lead was connected to an Enertrax TM implantable pulse generator. A pouch was created for the generator deep to the latissimus dorsi. Documentation of pacing was obtained electrocardiographically; pacing faster than the fetal intrinsic rate. The muscle and the fetal skin were closed. The pacemaker was programmed to a rate of 70 In the ventricular inhibited (VVI) mode and the uterine and abdominal wall incisions were then closed. One lamb was successfully delivered by Cesarean section at term. Pacing parameters were measured at birth and one month later. There were small changes in the pacing lead function parameters as the implant progressed into the chronic phase. They were within the capacity of the generator to pace with a margin of safety. Four lambs died in utero and were delivered 5 to 26 days post‐implant. We conclude that permanent cardiac pacemaker implantation is feasible in the fetal lamb and with further development, it may eventually be used in humans in the treatment of fetal congestive heart failure due to bradyarrhythmias.
Noninvasive Transcutaneous Cardiac Pacing in Children
Authors: BÉLAND MARIE J. , HESSLEIN PETER S. , FINLAY CAMERON D. , FAERRON‐ANGEL JORGE E. , WILLIAMS WILLIAM G. , ROWE RICHARD D.
Published: July 2006

Noninvasive transcutaneous cardiac pacing is an emergency pacing modality with proven benefits for adult patients. During induction of anesthesia for heart surgery, we externally paced 22 children (aged 0.9–17.9 years and weighing 6.96 to 51 kg) using a commercially available device to pace approximately 10 beats per minute faster than the spontaneous heart rate. Three pacing electrode sizes were used (the standard adult size and two specially manufactured smaller sizes). A total of 56 pacing trials were conducted, 53 of which were successful in obtaining capture. A mean output of 63 ± 14 mA (range. 42–98) at threshold using the large electrodes was comparable to published adult requirements. Lower current outputs were needed with the medium (53 ± 12 mA; range, 36–92) and small electrodes (51 ± 31 mA; range, 29–82). In any given patient, the large electrodes required more current (p < 0.01) to obtain capture, but delivered less current density (p < 0.01) and exhibited less impedance (p < 0.01) than the smaller electrodes. The mean threshold energy requirement was 0.12 ± 0.01 joules/beat regardless of pad size. Output, current density, impedance and energy requirements did not vary with age, weight or chest size. No complications of external pacing were noted. We conclude that noninvasive transcutaneous pacing can be used safely and effectively in children, and that chest size might necessitate the use of smaller electrodes in children weighing less than 15 kilograms.
Intermittent Ventricular Standstill During Chronic Atrial Fibrillation in Patients with Dizziness or Syncope
Authors: REBELLO ROSARIO , BROWNLEE WILLIAM C.
Published: July 2006

Thirty‐two patients with atrial fibrillation and normal ventricular rates who complained of dizziness or loss of consciousness underwent 24‐hour ambulatory electrocardiographic monitoring. A control group of 25 patients in atrial fibrillation but without symptoms of dizziness or loss of consciousness was likewise investigated. All patients remained in atrial fibrillation; periods of ventricular standstill (mean, 2.9; range, 1.8–8.0) were present in 31 symptomatic patients but in only three of the control patients (mean, 1.9 s; range, 1.7–2.4). Twenty‐three symptomatic patients with pauses ± 2.0 s received a demand pacemaker. Following pacing, nineteen became completely asymptomatic; four patients continued to have dizziness but three of these, who also experienced syncope, no longer did so (mean follow‐up, 13 months; range, 6–30). It is suggested that ventricular standstill may commonly occur in patients with controlled atrial fibrillation who complain of dizziness or syncope and that the majority will benefit from permanent cardiac pacing.
Assessment of the Work Capacity and Relationship Between Rate Response and Exercise Tolerance Associated With Activity‐Sensing Rate‐Responsive Ventricular Pacing
Authors: ÆRESTRAND SVEIN F , BREIVIK KJELL , OHM OLE‐JØRGEN
Published: July 2006

The relationship between rate response and exercise tolerance was studied by measuring the symptom‐limited maximum treadmill time (MTT) both during fixed rate VVI pacing and during VVI + activity mode pacing (RRP) in 15 patients (mean age, 73 years) who had received rate‐responsive ventricular pacemakers. Their indications were atrioventricular block, sino‐atrial block, and atrial fibrillation with slow ventricular response. Basic rate was programmed to 60 ppm in both pacing modes; rate response and activity threshold were programmed to 5 and medium, respectively. The order in which the two pacing modes were tested was randomly determined. The MTT was, on average, 29% longer in RRP than in WI mode with a mean of 12 minutes in VVI and 14.8 minutes in RRP(p < 0.001). For the subgroup of eight patients with paced‐only rhythm the average increase in MTT was 38% with a mean of 9.5 minutes in VVI and 12.8 minutes in RRP (p < 0.01). Seven patients who showed episodes of spontaneous rhythm, increased their average MTT by 17% (mean in VVI, 14.9 minutes; in RRP, 17.1 minutes; p < 0.02). During RRP, a significant positive correlation existed between MTT and the increase in heart rate (N = 15; r = 0.83; p < 0.001). In 12 patients with paced‐only rhythm, the pacing rate remained at the programmed basic rate when the patients were lying, sitting, and standing and increased to 86 ± 4 ppm during casual walking, and to 101 ± 4 ppm during jumping up and down with the pacemaker programmed to the above‐mentioned parameters. The maximum pacing rate during jumping corresponded with the maximum pacing rates measured from Holter recordings during normal daily activities.
Ventricular Fibrillation Survivors in whom Tachyarrhythmia Cannot Be Induced: Outcome Related to Selected Therapy
Authors: KRON JACK , KUDENCHUK PETER J. , MURPHY EDWARD S. , MORRIS CYNTHIA D. , GRIFFITH KAREN , WALANCE CHARLES G. , McANULTY JOHN H.
Published: July 2006

Eight‐five patients were studied to determine the prognosis of the ventricular tachyarrhythmias at the time of electrophysiologic study. Twenty‐five patients (29%) were not inducible when we used a stimulation protocol consisting of up to four extrastimuli delivered at two right ventricular sites. Patients with no inducible arrhythmias were younger (53 vs 59 yrs; p = .06) and had higher ejection fractions (.49 vs .34; p < .04) than the inducible ventricular fibrillation survivors. Sex, cardiac diagnosis, time from event to electrophysiologic study, and antiarrhythmic therapy at the time of event did not discriminate between those with and those without inducible ventricular tachyarrhythmias. Survival free of recurrent sudden death or ventricular tachycardia was .86 ± .05 and .95 ± .05 for patients with and without inducible tachyarrhythmias, respectively (p = .22). Nine of 25 (36%) patients with no inducible arrhythmias developed inducible ventricular tachyarrhythmias when testing was repeated with an antiarrhythmic drug. Ventricular fibrillation survivors not inducible at the time of programmed ventricular stimulation (using a stimulation protocol consisting of four extrastimuli delivered at two right ventricular sites) seem to have a good prognosis. Many “noninducible” patients develop inducible tachyarrhythmias when placed on antiarrhythmic therapy. Because it is possible that these drugs are proarrhythmic, empiric antiarrhythmic therapy should be avoided in these patients.
A Microcomputer System for On‐Line Study of Atrioventricular Node Accommodation
Authors: JENKINS JOHN R. , CLEMO HENRY F. , BELARDINELLI LUIZ
Published: July 2006

An automated on‐line programmable stimulator and interval measurement system was developed to study atrioventricular node (AVN) accommodation. This dedicated microcomputer system measures and stores the stimulus‐to‐His bundle (S‐H] interval from His bundle electrogram (HBE) recordings. Interval measurements for each beat are accurate to within 500 μs. This user‐controlled system has been used to stimulate at any rate up to 6.5 Hz and to measure intervals up to 125 ms in isolated perfused guinea pig hearts. A built‐in timer‐reset mechanism prevents failure of the system in the absence of a His potential (i.e., 2:1 AV block). It may be modified for use in clinical studies or other experimental systems and has the ability to measure other physiological intervals. The system provides the precision in pacing and accuracy in the measurement of AVN conduction time that is necessary for meaningful analysis of AVN accommodation and has the simplicity of design and use that is not available in previously described systems. Furthermore, this computer system can be used not only in studies involving AV conduction, but also in any setting where programmed stimulation and interval measurement and recording need to be performed simultaneously.
Triggered Activity Induced By Pacing During Digitalis Intoxication: Observations During Programmed Electrical Stimulation in the Conscious Dog With Chronic Complete Atrioventricular Block
Authors: GORGELS ANTON P.M. , DE WIT BRAM , BEEKMAN HENRIETTE D.M. , DASSEN WILLEM R.M. , WELLENS HEIN J.J.
Published: July 2006

In isolated Purkinje fibers, digitalis intoxication induces triggered activity, which is based upon delayed afterdepolarizations. The characteristics of delayed afterdepolarizations have been studied systematically by programmed electrical stimulation. The present investigations were done to study the role of triggered activity during digitalis intoxication in the intact heart. For this purpose, a pacing protocol, similar to that used in experiments of isolated Purkinje fibers, was used. The experiments were done on conscious dogs with chronic complete atrioventricular block. Ventricular tachycardia was induced with digoxin IV 0.1 mg/kg/1‐1½ hr. The effect of programmed electrical stimulation on the first post‐pacing interval was determined during sustained ventricular tachycardia and, following its spontaneous termination during an episode when ectopic activity could only be induced by pacing. During sustained ventricular tachycardia there was a direct linear relation between the interstimulus interval of regular pacing and the first post‐pacing interval. During the episode when ectopic activity could only be induced by pacing, shortening of the post‐pacing interval resulted in biphasic behavior of the first post‐pacing interval. Pacing with interstimulus intervals of more than 400 ms induced a first post‐pacing interval equal to the interstimulus interval, whereas shorter interstimulus intervals induced a first post‐pacing interval twice the interstimulus interval. When during regular pacing only the last pacing interval was changed, a similar biphasic response resulted. When toxicity had almost subsided, ectopic activity could only be induced following short pacing intervals (200– 320 ms). Again, a direct linear relation was found between the pacing interval and the first post‐pacing interval. Our findings strongly suggest that at different levels of digitalis intoxication triggered activity is the underlying mechanism for the first post‐pacing QRS complex.
Chronic Idiopathic Idioventricular Tachycardia Caused by Slow Response Automaticity
Authors: CHIALE PABLO A. , SICOURI SERGE J. , ELIZARI MARCELO V. , ROSENBAUM MAURICIO B.
Published: July 2006

A 22‐year‐old female, asymptomatic and without any evidence of cardiac disease, was found to have a persistent idioventricular tachycardia (IVT). Sinus rhythm and IVT rates were similar and showed parallel changes in successive resting electrocardiograms. Both IVT and sinus rhythm were transiently slowed or suppressed by vagal stimulation and accelerated by sympathetic stimulation. Long periods of atrial overdrive pacing, at a rate 62% faster than the spontaneous rate of IVT, depressed both ectopic and sinus activity. Fast channel blocking agents (lidocaine, disopyramide), and digoxin and amiodarone failed to modify IVT significantly. Verapamil, a calcium channel blocking drug, allowed total control of the arrhythmia. These electrophysiologic and pharmacologic responses suggest that the IVT may relate to the automatic activity of a ventricular focus of the “slow response” type, functionally resembling an “additional” sinus node with preserved innervation. During an 88‐month follow‐up, the patient continued to be asymptomatic, warning arrhythmias were never found and the features of IVT remained unmodified.
Characteristics of Ventriculoatrial Conduction in Patients with Enhanced Atrioventricular Nodal Conduction
Authors: DOUGHERTY ANNE HAMILTON , NACCARELLI GERALD V.
Published: July 2006

To study the characteristics of the ventriculoatrial conduction system in palienfs capable of rapid antegrade atrioventricuiar conduction, eiectrophysiologic studies were performed in 23 subjects capable of 1:1 atrioventricular conduction at atrial cycle lengths < 300 ms (Group I). and in 23 subjects with normal 1:1 atrioventricular conduction (Group II). During venfricular pacing, ventriculoatrial block at all cycle lengths was seen in 5/23 (22%) in Group I and in 7/23 (30%) in Group II patients (p = NS). In the remainder, the minimum ventricuar pacing cycle length maintaining 1:1 ventriculoatrial conduction was 359 ± 85 ms in Group I, compared to 444 ± 118 ms in Group II (p < .02). Both flat and exponential VA conduction interval curves, drawn as a function of pacing cycle length, were observed in both groups. Discontinuous ventricuioatrial conduction curves were seen in 5/18 (28%) Group I and 1/16 (6%) Group II patients (p = NS). In conclusion, retrograde ventriculoatrial conduction, when present in patients capable of rapid 1:1 atrioventricular conduction, is maintained at shorter cycle lengths than in patients with normal atrioventricular conduction. Quantitative, rather than qualitative, differences distinguish the two groups.
Cough Syncope Presenting as Mobitz Type II Atrioventricular Block—An Electrophysiologic Correlation
Authors: BARON SCOTT B. , HUANG SHOEI K.
Published: July 2006

A 34‐year‐old man with a history of cough syncope exhibited Mobitz type II atrioventricular block with a narrow QRS complex on Holter monitoring. The baseline electrophysiologic study was normal. No significant atrioventricular block could be induced with carotid sinus massage, neck suction, or intravenous propranolol. However, coughing reproduced Mobitz type II atrioventricular block, which was found to be above the His bundle on the His bundle electrogram. A review of the mechanism of cough syncope is also presented.
Defibrillation Threshold: A Simple and Quantitative Estimate of the Ability to Defibrillate
Authors: RATTES MAX F. , JONES DOUGLAS L. , SHARMA ARJUN D. , KLEIN GEORGE J.
Published: July 2006

It has recently been shown that the probability of successful defibrillation as a function of energy has a sigmoidal dose‐response relationship. Determination of a defibrillation “dose‐response curve” is time consuming and requires multiple defibrillation attempts. On the other hand, determination of a defibrillation threshold is achieved rapidly and would be better suited to study the effect of interventions on the ability to defibrillate patients. We assessed the relationship of defibrillation threshold to the defibrillation “dose‐response curve” in twelve open chest, halotbane anesthetized pigs. Ventricular fibrillation was induced electrically, and defibrillation was attempted by passing sequentiai puise shocks through an indwelling catheter and plaque electrodes. Defibrillation threshold was determined by decreasing the stored voltage of the initial shock until it failed to defibrillate the heart. Five different stored voltage levels distributed around defibrillation threshold were then randomly administered, six times for each level. A “dose‐response curve” was obtained for each animal. Defibrillation threshold superimposed on the “dose‐response curve” at 76 ± 7.2 percent (mean ± SEM) defibrillation success. Energy delivered at 1.5 times average defibrillation threshold was predicted to achieve 100 percent defibrillation success for a single shock in all animals. We conclude that defibrillation threshold provides a simple and quantitative estimate of the ability to defibrillate with a predictable relationship to the “dose‐response curve.”
Chronotropic Response of an Activity Detecting Pacemaker Compared with the Normal Sinus Node
Authors: MOURA PAULO J. , GESSMAN LAWRENCE J. , LAI TSU , GALLAGHER JOHN D. , WHITE MELVIN , MORSE DRYDEN P.
Published: July 2006

We compared the rate responsiveness of an activity‐detecting muitiprogrammable, single chamber pacemaker (Medtronic Acfivitrax) to rate responsiveness of the normal sinus node. This pacemaker changes its basic pacing rate in response to physical activity. The rate responsiveness is programmable by selecting one of three activity thresholds, and one of 10 rate response settings. The study included a group of six normal volunteers and 12 patients implanted with Activitrax to examine the similarity of the pacemaker rate to normal sinus rhythm during acceleration and deceleration. The pacemaker was set to Activity mode, at a basic rate of 60 bpm. In voiunteers, the device was externally secured on the chest wall and tested at two programmed settings. When programmed at a high threshold of activity and high rate response in voiunteers, there was no significant difference in maximum normal sinus rates and pacemaker rates during arm waving, jumping in place, and walking during stress testing. At a medium activity threshold, the only significant difference occurred during submaximal stess testing, when the maximum sinus rate achieved was 141 ± 19 bpm and the maximum pacing rate was 105 ± 8 bpm (p < .02). The pacemaker behaved in a similar manner in patients, successfully simulating the typical fast acceleration and slow deceleration of a normal sinus node in exercise testing. There was no difference in pacer response when implanted in abdominal or in/raclavicular locations. The implanted units have functioned normally over a follow‐up period of nine to 22 months. Activitrax can be programmed to achieve physiologic pacing rates in response to normal daiiy activities with appropriate programming.
Platinum Pacemaker Electrodes: Origins and Effects of the Electrode‐Tissue Interface Impedance
Authors: WALTON CHRISTOPHER , GERGELY STEPHEN , ECONOMIDES APOLLO P.
Published: July 2006

Investigation of the unipolar properties of the paced‐evoked response requires special measures to eliminate the post‐stimulus potential, and this in turn requires a knowledge of the properties of the electrode‐tissue interface which is not supplied by any single source in the literature. We have therefore drawn together published informatlon and some ofour own experimental results. The behavior of a particular type of pacemaker electrode was investigated in vitro under a range of conditions. The application of DC potentials revealed an extremely nonlinear voltage‐current characteristic with conduction thresholds at about +1 V and −1 V. Small signal AC response to applied voltages well within these values (20 mV pk‐pk) was found to be lineor when a nonpolarizable counterelectrode was used. Nonlinearities were introduced hy the use of a stainless steel counterelectrode. The response of an in vitro model of a paced patient to voltage pulses (amplitude 5 V, duration 0.5 ms) was also investigated. We have made extensive use of previously published work to demonstrate the mechanisms underlying these results and also their relationship to each other. We have concluded with some theoretical comments upon the design requirements for a device to eliminate the post‐stimulus afterpotential in order to detect the paced‐evoked response.
Changes in Morphology of the Paced QRS Complex Related to Atrial Contraction
Authors: ORETO GIUSEPPE , SATULLO GAETANO , LUZZA FRANGESCO , ARRIGO FRANGESGO
Published: July 2006

A patient with 2:1 AV block underwent temporary ventricuJar pacing. AU the paced stimuli resuited in ventricular capture, but a marked variability in morphology of the paced QRS complexes occurred. Two different types of paced QRS complex (labeled A and B) were recognized. Type B complexes were manifest only when the pacing stimulus was preceded hy a sinus P wave within a time interval ranging from 0.15 to 0.52 sec. The P wave‐induced changes in morphology of the paced QRS complexes were interpreted as due to displacement of the pacing ventricular lead caused by atrial systole.
Supraventricular Tachycardia Induced by Swallowing: A Case Report and Review of the Literature
Authors: MORADY FRED , KROL RYSZARD B. , NOSTRANT TIMOTHY T. , DE BUITLEIR MICHAEL , CLINE WARREN
Published: July 2006

A 64‐year‐old man who complained of palpitations brought on by swallowing was found to have short runs of paroxysmal supraventricular tachycardia (SVT) induced by swallowing. Electrophysiology studies suggested that the SVT was an automatic atrial tachycardia. An esophageal manometric study demonstrated that the tachycardia was coincident with relaxation of the upper esophageal spincter and preceded peristaltic activity in the esophageal body. Atropine and bethanechol did not affect the swallow‐induced tachycardia. The patient's symptoms were controlled by verapamil and quinidine. After five months, these medications were discontinued, with no recurrence of symptoms. Based on analysis of ten prior cases and the present case, it appears that swallow‐induced SVT generally occurs in men between the ages of 45–75 years who have no evidence of structural heart disease or an esophageal disorder. The SVT is usually either a nonsustained automatic atrial tachycardia or atrial fibrillation. The mechanism is conjectural, but the most likely possibility is a vagally‐mediated neural reflex, probably involving a neu‐rotransmitter other than acetylcholine.
Ventricular Standstill Complicating Cardiac Catheterization
Authors: TWIDALE NICHOLAS , TONKIN ANDREW
Published: July 2006

A patient is described in this paper who developed repeated episodes of venfricular stcindstill during left heart catheterization. The patient had a resting pattern of right bundle branch block with left anterior fascicular block; subsequent electrophysiology study was normal. Ventricular standstill during catheterization was apparentiy due to catheter‐related trauma of His bundle connections.
Neurostimulation for Patients in Vegetative Status
Authors: KANNO TETSUO , KAMEI YOSHIFUMI , YOKOYAMA TETSUYA , JAIN V. K.
Published: July 2006

Dorsal column stimulation has been used in four patients who were in a persistent vegetative state. There was improvement of the EEG in four patients and clinical improvement in three patients. Stimulation was for 12 hours per day at 100 Hz, 5 to 8 volts, and with a pulse width of 0.12 msec. The mechanism of improvement may involve changes in cerebral blood flow.
Dorsal Periaqueductal Gray‐Matter Stimulation in Humans
Authors: HOSOBUCHI YOSHIO
Published: July 2006

Seven patients suffering intractable pain from head and neck cancer (age 48–73, mean 57.5 years) underwent acute stimulation of dorsal periaqueductal gray matter (PAG) with immediate cessation of pain. Two patients received chronic PAG stimulation with relief of pain during stimulation. The effect was not reversed by naloxone and there were no changes in CSF peptides.
Evoked Metabolic Responses in the LimbicStriate System Produced by Stimulation of Anterior Thalamic Nucleus in Man
Authors: UPTON A.R.M. , AMIN I. , GARNETT S. , SPRINGMAN M. , NAHMIAS C. , COOPER I.S.
Published: July 2006

Six human subjects (5 male, 1 female, age 23.7 + 5.7 years) with incapacitating partial seizure disorders intractable to medical therapy have been treated by ongoing pulsed electrical stimulation of anterior nucleus of the thalamus. Four of the six patients have demonstrated statistically significant clinical control of the seizure disorder. One patient (D.L.) has been seizure ‐free for the last two years. In two of these six patients, it was possible to study not only electrophysiological activity of the brain, but also regional cerebral glucose metabolism by the (18F) 2‐fluoro‐2‐deoxy‐D‐glucose method, blood cortisol levels, and blood levels ofvaiproic acid, diphenylhydantoin, and carbamazepine. Significant changes were seen during periods of stimulation compared with control periods without stimulation. These results imply that stimulation of the principal thalamic relay nucleus of the limbic system causes clinical, behavioral, cerebral metabolic, electroencephalographic, endocrinologic, and pharmacokinetic responses.
Cochlear or Nerve Stimulation
Authors: WHITE ROBERT L.
Published: July 2006

To simulate through electrical stimulation the auditory nerve excitation patterns produced by a normal ear, it is necessary to control both the spatial and the timing aspects of the neural firing pattern. While the spatiaJ localization, the “place” aspect of stimulation can probably be achieved adequately with either scala tympani or direct eighth nerve electrodes, only the eighth nerve electrodes have the potential to reproduce the detailed timing patterns of the normal nerve. While such complete control of the stimulation pattern is probably necessary to produce “natural” auditory percepts, it may well not be necessary for the conveying of the information in speech because of the plasticity and pattern recognition capabilities of the brain. Present encouraging results as open speech comprehension with scala tympani electrode arrays suggest that, in many cases at least, the cruder stimulation pattern control will suffice.
The Swedish Experience in Phrenic Nerve Stimulation
Authors: FODSTAD HARALD
Published: July 2006

Phrenic nerve stihiiilators (diaphragm pacers) were implanted in 20 patients with partial or total respiratory insufficiency of central nervous origin and chronic singultus. A 2–84 months follow‐up (M = 41),10 patients are entirely independent of a conventional respirator, two patients are partially dependent on respirator, three patients are dead, and five patients including two with hiccups had limited or no help from diaphragm pacing.
Direct Diaphragm Stimulation
Authors: MUGICA J. , DEJEAN D. , SMITS K. , BOURGEOIS I. , BISSON A.
Published: July 2006

Direct diaphragmatic stimulation is effective without discomfort to the patient and without muscular fatigue. However, some quadriplegic patients may require synchronous expiratory stimulation in order to obtain complete and permanent respiratory autonomy. Now it will be necessary to undertake further studies of the indications for direct diaphragm stimulation.
Chronic Stimulation of the Gasserian Ganglion for Treatment of Atypical Facial Neuralgia
Authors: LAZORTHES Y. , ARMENGAUD J.P. , DA MOTTA M.
Published: July 2006

After a trial of percutaneous stimulation of the Gasserian ganglion in 21 patients with atypical facial pain, five patients were selected for chronic implantation. After a follow‐up of two years (18 to 32 months), there is stable and excellent analgesia in three patients. There are various complications and problems associated with the method of implantation, either percutaneous or open. The best indication for this procedure is the presence of trigeminal pain and some sensory loss in the painful area. This new application of neurostimulation for pain was described by Myerson in 1980, and this therapy should be considered for any patient who has atypical facial pain that has been resistant to other forms of treatment.
Simultaneous Multichannel Cardiac Mapping Systems
Authors: IDEKER RAYMOND E. , SMITH WILLIAM M. , WOLF PATRICK , DANIELEY NED D. , BARTRAM FREDERICK R.
Published: July 2006

Simultaneous multichannel cardiac mapping systems. There is much current interest in simultaneous multichannel cardiac mapping. In this paper we give recommendations for the construction of a cardiac mapping system. Because the field of cardiac mapping is relatively young, optimum mapping techniques and all possible applications have not yet been developed. Therefore, the mapping system should be flexible and it should have many capabilities. The system should be digital; if variable gains are used, the amplifiers should be programmable and controlled by a microprocessor. It should be possible to analyze previous recordings and acquire additional recordings simultaneously. The mapping system should be able to record continuously for at least tens of minutes and preferably for hours. The recorded data stream should be a self‐contained unit, holding all important electrophysiologic information as well as the recorded electrode signals. The programs should be written in c under a UNIX operating system. A minimum of 64 channels should be used for epicardial or endocardial mapping and a minimum of 128 channels for three‐dimensional intramural mapping. The leakage current requirements for multichannel mapping systems are too stringent and should be re‐evaluated. The major limitation to progress in cardiac mapping is neither the hardware nor the software; it is the electrode: its construction, its placement, its fixation, and the interpretation of its recordings.
Pulsed Doppler Verification of Atrial Contribution to Ventricular Filling in Sequential Pacing
Authors: PAULETTI MARINA , RAUGI MAURIZIO , BINI GIANCARLO , BELLI PIETROPAOLO , DEL BENE PASQUALE
Published: July 2006

We have used pulsed Doppler to ascertain effective atrial contribution to ventricular filling in sequential pacemaker rhythm. The technique is particularly valuable when electrocardiographic evidence of atrial capture is uncertain.
Pseudohysteresis in a Universal AV Sequential Pacemaker
Authors: QUINTAL ROBERTO E. , DHURANDHAR RAJA W. , JAIN RAJENDRA K.
Published: July 2006

We describe pacemaker pauses and pseudohysteresis resulting from sensing of retrograde P waves in a patient with an implanted AV sequential universal pacemaker. Although retrograde P waves are usually followed by a ventricular spike and therefore create the possibility for “endless loop tachycardia,” in our patient some retrograde P waves which followed premature ventricuiar contractions or junctional beats produced pacemaker pauses. The reason for the occurrence of this phenomenon is that the sum of the VA conduction time and the AV delay is shorter than the pacemaker's hardware rate limit. Therefore, the ventricular spike that should follow the retrograde P wave is inhibited. In the pacemaker used by us, the atrial refractory period is only initiated by an atrial event, allowing the pacemaker to sense retrograde P waves occurring after premature junctional or ventricular depolarizations. Although no therapy is needed for the phenomenon described, it is important to understand its true significance and to avoid unnecessary surgical procedures.
BOOK REVIEW
Authors: Furman Seymour
Published: July 2006

Book reviewed in this article:

Batteries for Implantable Biomedical Devices. Edited by Boone B. Owens
The NASPE*/BPEG** Generic Pacemaker Code for Antibradyarrhythmia and Adaptive‐Rate Pacing and Antitachyarrhythmia Devices
Authors: BERNSTEIN ALAN D. , CAMM A. JOHN , FLETCHER ROSS D. , GOLD ROBERT D. , RICKARDS ANTHONY F. , SMYTH NICHOLAS P.D. , SPIELMAN SCOTT R. , SUTTON RICHARD
Published: July 2006

A new generic pacemaker code, derived from and compatible with the Revised ICHD Code, was proposed jointly by the North American Society of Pacing and Electrophysiology (NASPE) Mode Code Committee and the British Pacing and Electrophysiology Croup (BPEC), and has been adopted by the NASPE Board of Trustees. It is abbreviated as the NBC (for “NASPE/BPEC Generic”) Code, and was developed to permit extension of the generic‐code concept to pacemakers whose escape rate is continuously controlled by monitoring some physiologic variable, rather than determined by fixed escape intervals measured from stimuli or sensed depolarizations, and to antitachyarrhythmia devices including cardioverters and defibrillators. The NASPE/BPEC Code incorporates an “R” in the fourth position to signify rate modulation (adaptive‐rate pacing), and one of four letters in the fifth position to indicate the presence of antitachyarrhythmia‐pacing capability or of cardioversion or defibrillation functions.
Cardioversion and Defibrillation Using a Catheter Electrode: Myocardial Damage Assessed at Autopsy
Authors: PERKINS D. GARTH , KLEIN GEORGE J. , SILVER MALCOLM D. , YEE RAYMOND , JONES DOUGLAS L.
Published: July 2006

A technique has been described for countershock in an intensive care setting using a catheter electrode in patients with recurrent ventricular tachyarrhythmias. During defibrillation or cardioversion an electrode in the superior vena cava acts as an anode and an eieclrode in the right ventricular apex is the cathode. This report describes the resultant changes in the hearts of four men who died with recent, large myocardiai infarcts and who had received eight to 55 countershocks of 2.5–50 joules through the catheter. Mural thrombus and/or focal endothelial hemorrhage wasfound in three hearts at the anode site. Thrombus was seen at the cathode site in two hearts. Myocardial necrosis, secondary to the catheter, was present in only one heart which had a 2 mm rim of granulation tissue around the distal electrode. It is unlikely that this focal area of right ventricular damage would be dinicalIy important. We conclude, therefore, that repeated counlershocks delivered through the catheter system produce little myocardia] damage.
Electrophysiologic and Histologic Observations of Chronic Atrioventricular Block Induced by Closed‐Chest Catheter Desiccation with Radiofrequency Energy
Authors: HUANG SHOEI K. , BHARATI SAROJA , LEV MAURICE , MARCUS FRANK I.
Published: July 2006

Direct‐current or laser energy has been used to induce atrioventricular (AV) block, but certain complications associated with this type of energy have been reported. We have previously documented that radiofrequency (RF) energy can effectively and safely induce acute AV block in ciosed‐chest dogs during the 4–7 days of follow‐up. This study was undertaken Io determine if the ablation was permanent and to define the chronic pafhoiogy and site of AV block. Gomplete AV block was successfully achieved in four dogs immediately after ablation with a bipolar “standard” RF output (750 kHz) delivered between the tip electrode of a standard 7F USCI catheter and an external patch electrode on the left iateral chest wall. During 2 months of follow‐up, three dogs had persistent complete AV block with a stable escape rhythm; the other had persistent 2:1 AV block. Repeat His bundle recordings were performed at 2 months prior to sacrifice of the dogs. Supra‐His AV block was noted in two dogs; His bundle potential could not be recorded in another two. Histologically, the damaged area was well delineated. In all animals, the AV node and, in some dogs, part of the His bundle were completely replaced by granulation tissue and/or cartilage. There was fatty infiltration and also chronic inflammatory cells around the lesions. Neither perforation, hemorrhage nor vacuolation was seen in the adjacent area. Thrombus was not present. It is concluded that RF energy can effectively achieve chronic AV block and produce well‐circumscribod pathological lesions.