bluuebunny/crossref_metadata_2025 huggingface dataset:
Relationship Between QT Interval Duration and Electrical Induction of Ventricular Tachycardia
Authors: DABROWSKI A. , KOLODZIEJ P. , KRUPIENICZ A.
Published: July 2006

The relation of inducible ventricular tachycardia (VT) to QT interval duration of ventricular paced rhythm has not been evaluated. To clarify this relation we measured corrected QT interval duration (QTC) during sinus rhythm and QT interval duration during ventricular paced rhythm (QT‐V) in patients with coronary artery disease without (non‐VT group = group B) and with inducible VT (VT group = group A). Duration of QT‐V was greater in the VT group (n = 20) compared with non‐VT group (n = 20) during ventricular pacing at cycle lengths of 600 ms (424 ± 26 vs 396 ± 19 ms, P < 0.01), of 500 ms (407 ± 20 vs 383 ± 21 ms, P < 0.01), and of 400 ms (390 ± 21 vs 362 ± 17 ms, P < 0.001). During sinus rhythm the mean values of QTC were similar in both groups (408 ± 25 vs 413 ± 20 ms, NSJ. During ventricular stimulation the percentage of patients with values of QT‐V exceeding 380 ms was 35% in non‐VT group and 95% in VT group (P <0.01) at cycle length of 500 ms and 5% versus 60%, respectively, (P < 0.01), at cycle length of 400 ms. Thus, a trend toward longer QT values of ventricular paced rhythm exists in patients with inducible VT.
Ventricular Tachycardia/Fibrillation: Therapeutic Alternatives
Authors: FISHER JOHN D. , KIM SOO G. , ROTH JAMES A. , FERRICK KEVIN J. , BRODMAN RICHARD F. , GROSS JAY N. , FURMAN SEYMOUR
Published: July 2006

It is now clear that no single therapy is appropriate for a consecutive series of patients with ventricular tachycardia or ventricular fibrillation (VT/VF). Drug responders by electrophysiological studies, patients who are not inducible following surgery, and patients treated with an implantable cardioverter defibrillator (ICD) all can have similarly low sudden death rates and virtually identical long‐term mortality. However, many patients fail to respond to drugs, and surgical risks are excessive in others, and always higher than for an ICD implant. Nevertheless, overall survival in each of these groups (and probably for patients treated with antitachycardia pacers and ablation) is about 60% at 60 months. Major challenges now are: (1) choosing therapy to maximize risk‐benefit ratio; and (2) treatment of the pump failure and progressive disease that now accounts for most cardiac mortality.
Implantable Pharmacological Defibrillator (AIPhD): Preliminary Investigations in Animals
Authors: CAMMILLI LEONARDO , MUGELLI ALESSANDRO , GRASSI GINO , ALCIDI LUCIANO , MELISSANO GERMANO , MENEGAZZO GIAMPAOLO , SILVESTRI VITO
Published: July 2006

The treatment of ventricular fibrillation (VF) by means of automatic implantable cardioverter defibrillators (AICD) poses many severe problems and limitations at the present time. In order to overcome these problems, we propose a totally new way to terminate VF or ventricular sustained tachycardia (VST). Our proposal consists of replacing the electric shock, which is dangerous, delayed, and sometimes ineffective, with a “chemical” shock: i.e., a chemical bolus retroperfused in the coronary sinus (CS) immediately after VF arises. The possible device is hypothesized and preliminary investigations in animals, performed to verify the theoretical assumption, are presented. In rabbits, and in larger animals (sheep and swine). Drugs were perfused in the coronary bed: lidocaine was used in 86% and bretylium tosylate in 14% of the animals. The results were: lidocaine immediately terminated VF in 100% and sinus rhythm was restored in rabbits; lidocaine terminated VF in VST in sheep; and in swine, bretylium immediately produced sinus rhythm in one case; in another one, only delayed sinus rhythm was achieved but lasted a short time; in the last case ventricular tachycardia at 128 beats/min appeared. Because new drugs, which are really “defibrillating” drugs, are available (bretylium tosylate, bethanidine, clofilium, tricyclic antidepressants, phenotiazine derivatives), we plan to investigate these defibrillating drugs in isolated hearts, found in suitable animals like dogs (sheep and swine are difficult to defibrillate) and in humans during routine electropharmacological studies.
The Etiology of Syncope in Pacemaker Patients
Authors: PAVLOVIC SINISA U. , KOCOVIC DUSAN , DJORDJEVIC MILAN , BELKIC KAREN , KOSTIC DUSAN , VELIMIROVIC DUSAN
Published: July 2006

A total of 46 patients with syncopal episodes after VVI pacemaker implantation were studied. Of these, 92% had one to three syncopal episodes and 8% more than three. All underwent a thorough clinical examination, which included chest X ray, echocardiogram, neurological exam, and the following protocol: 24‐hour Holler monitoring, EEG, blood pressure (BP) measurement in three positions, Doppler exam of the carotid vessels, fasting blood glucose, and head‐up tilt table test (60 minutes, 60°). Holter monitoring showed exit block in two patients (4.3%) and failed sensing in one (2.1%). In two patients there was unilateral slowing on EEG. Orthostatic hypotension was found in four patients (8.6%), and hypoglycemia in three insulin‐dependent diabetics. An ocdusive atherosclerotic plaque in the carotid artery was found in three patients (6,5%). Syncope was induced in 17 patients (36,9%) by the tilt table test, after a mean standing time of 47 ± 11 minutes. The mean resting systolic BP of these patients was 140 ± 24 mmHg, and fell to a mean level of 56 ± 8 mmHg (mean systolic BP drop was 79 ± 8 mmHg). Sixteen of these 17 patients with positive tilt table were being paced at the time of syncope and one had a spontaneous heart rate of 73 beats/min. In 14 cases (30.4%) the cause of syncopai episodes after this extensive workup remained unexplained. These results indicate that pacemaker dysfunction is a not major cause of syncopal episodes in pacemaker patients and that these are most often due to vasovagal syncope. Long‐term follow‐up is warranted to determine the prognostic significance of various types of syncope in pacemaker patients.
The Effect of Exercise on the Atrial Electrogram Voltage in Young Patients
Authors: ROSS BERTRAND A. , ZEIGLER VICKIE , ZINNER ALEXANDER , WOODALL PEGGY , GILLETTE PAUL C.
Published: July 2006

Atrial electrogram sensing is an important function in active individuals with permanently implanted bipolar dual chamber pacing systems. We undertook to determine the effect of vigorous exercise on the atrial electrogram size in 11 children and young adults (average age 12 years). Using a telemetry signal through a handheld programming wand, nine tracings were completely and clearly recorded for analysis. Six patients had tined/passive fixation atrial leads and three patients had screw‐in/active fixation lead systems. All leads were bipolar. The atrial electrogram size for each patient was measured at rest and at each minute of exercise. The atrial electrogram size decreased with exercise from a mean of 5.08 mV to 3.44 mV (range 0.9–4.25 mV) (P = 0.002). The 1.64 mV mean decrease represented a 33.8% reduction (range 19%–56%) (P < 0.001). There was no difference in the change in atrial electrogram size between the two lead types. Treadmill exercise testing with telemetric data of atrial electrograms showed a decrease in atrial electrogram size produced by exercise and may be helpful in determining appropriate atrial sensitivity settings in selected individuals. Because of the documented decrease in atrial electrogram size produced by exercise, we recommend obtaining maximal atrial electrograms at the time of implant and use of pacing systems that allow maximal flexibility in atrial sensing especially in athletically active individuals.
Benefits of Smaller Electrode Surface Area (4 mm2) on Steroid‐Eluting Leads
Authors: SCHUCHERT ANDREAS , KUCK KARL‐HEINZ
Published: July 2006

The purpose was to test whether a reduction of pacemaker electrode surface area below 8 mm2 improves leads that elute steroid from the electrode tip to the surrounding myocardium. A standard‐sized 8 mm2 lead with 1 mg dexamethasone was implanted in 12 patients and a lead with 4 mm2 electrode surface area and 0.5 mg dexamethasone in ten patients. Pacing threshold, impedance, and sensing threshold were measured at implantation and after 1, 4, and 12 weeks. Pacing thresholds were similar for both groups and were always ± 0.8 V at 0,5 msec pulse duration in all patients. Impedance was significantly higher (P < 0.05) for the 4 mm2 lead (implantation: 726 ± 119 ohms; 1 week: 596 ± 71 ohms; 4 weeks: 624 ± 68 ohms; 12 weeks: 643 ± 56 ohms) than for the 8 mm2 lead (implantation: 422 ± 43 ohms; 1 week: 402 ± 48 ohms; 4 weeks: 439 ± 57 ohms; 12 weeks: 449 ± 61 ohms). R wave amplitudes did not differ between both groups; no sensing failure occurred at 5 mV sensitivity. Compared to the 8 mm2 lead the reduction of surface area to 4 mm2 did not influence pacing threshold, but resulted in a higher pacing impedance. The amount of pacing energy was lower in the smaller‐sized electrode. For clinical impact, low pacing threshold and high impedance leads are the condition to implant pulse generators with smaller battery capacity.
Direct Current Shock Ablation: Quantitative Assessment of Proarrhythmic Effects
Authors: FISHER JOHN D. , SCAVIN GALE M. , ROTH JAMES A. , FERRICK KEVIN J. , KIM SOO G. , JOHNSTON DEBRA R. , WILLIAMS HENRY R. , FRAME ROSEMARY
Published: July 2006

Catheter ablation using direct current (DC) shock has proved invaluable in the management of a variety of tachycardias. However, sporadic reports of fatal arrhythmias following ablation have raised the question of the proarrhythmic potential of DC shock ablation. The present study was undertaken in 45 patients to assess prospectively any proarrhythmia related to DC shock ablation, using matched pre‐ and postablation Holter monitors and programmed electrical stimulation (PES). Nineteen of these patients had Holter monitors for three successive postablation days to observe trends. There was unmatched data in 11 additional patients. All 56 patients provided prospective follow‐up for clinical events. There was no immediate sustained VT/VF at the time of the ablation. Four patients had sustained VT in the first 72 hours after ablation; three episodes were similar to the preablation clinical arrhythmias; one patient had torsades de pointes interrupting bradycardia. Twelve patients met Holter, PES, or clinical criteria for proarrhythmia; none were treated on the basis of these findings. On Holter monitoring, there were significant increases in VPCs/hour and couplets/hour in patients undergoing atrial or atrioventricular juncfional ablations; and an increase in couplets after accessory pathway ablations. Increases in these categories were not significant for VT patients; nor were increases in episodes of VT/hour or atrial arrhythmias significant in any group. Patients were followed for 44 ± 33 months, with an actuarial survival of 95% at 1 year, 88% at 3 years, and 85% at 4 years. There were six deaths during follow‐up. Two patients had sudden death; one at 2 months had early evidence of proarrhythmia; the other at 32 months may have represented later myocardia deterioration. One patient died of heart failure at 77 months; and there were three noncardiac deaths. DC shock ablation in humans is much less proarrhythmic than in dogs. The low incidence of clinical proarrhythmic events during prolonged follow‐up after discharge resulted in low sensitivity, specificity, and positive predictive values for Holter and PES, although the negative predictive values of these tests were > 90%. Only one of 12 patients who met criteria for proarrhythmia in the days immediately following ablation had subsequent clinical events consistent with proarrhythmia. These results may be useful as standards for comparison with results of radiofrequency or other ablation modalities.
Cardiac Electrophysiological Experiments in Numero, Part III: Simulation of Arrhythmias and Pacing
Authors: MALIK MAREK , CAMM A. JOHN
Published: July 2006

This paper is the third and final part of a series of articles reviewing mathematical and computer models of the electrophysiological processes. This section reviews the arrhythmia simulation and discusses models of arrhythmogenic processes, fibrillation and defibrillafion, and of heart‐pacemaker interaction. The models of arrhythmogenesis are classified into three main sections: models of reentry and vortex reentry, models of myocardial electrotonic interactions, and models of macroreentrant supraventricular tachycardias. This final part of the review discusses the future potential of mathematical and computer models of different cardiac processes.
Serum Creatine Kinase Activity And Sensing Characteristics After Intraoperative Arrhythmia Induction Using Implantable Defibrillator Rate Sensing Leads
Authors: GRUBB BLAIR P. , DURZINSKY DENNIS , MANCINI MARY C. , TEMESY‐ARMOS PETER
Published: July 2006

In 29 patients (24 men, 5 woman, mean age 57 ± 14 years) we evaluated the effect of intraoperative arrhythmia induction during impIantable defibrillator (ICD) placement using alternating current (AC) applied through the epicardial rate sensing leads on acute and chronic pacing thresholds, electrogram amplitudes, slew rates and serum creatine kinase levels. In 15 patients undergoing new ICD implantation, pacing thresholds, electrogram amplitudes, slew rates, and resistances were measured before and following at least three inductions of ventricular fibrillation (VF) using AC applied through the epicardial rate sensing leads. Fourteen patients who underwent VF induction using AC through the epicardial leads during initial implant (mean time of 31 months previously) underwent ICD pulse generator replacement only with parameters measured as above before and after at least two inductions, and these compared to the values at initial implant. In all 29 patients serum creatine kinase levels were obtained before, immediately following, and at 8, 16, and 24 hours after surgery. No significant change in acute pacing threshold, electrogram amplitude, slew rate or resistance occurred. Chronically there was an expected 154% increase in pacing threshold but no significant change in electrogram amplitude or resistance. Serial serum creatine kinase and MB isoenzyme determinations demonstrated no evidence of myocardial necrosis. We conclude that intraoperative arrhythmia induction during ICD implantation using AC applied through the rate sensing leads is a safe and effective technique.
Prolonged Asystole During Head‐Up Tilt Table Testing After Beta Blockade
Authors: DANGOVIAN MICHAEL I. , JARANDILLA REGINA , FRUMIN HOWARD
Published: July 2006

Neurally mediated vasodepressor syncope is a common clinical problem. The diagnosis is generally associated with a benign prognosis, however, a less common “malignant” form has been identified. Head‐up tilt table testing is helpful in the confirmation of the diagnosis of neurally mediated vasodepressor syncope and may be useful in the selection of therapy. One form of therapy commonly used is beta blockade. In this case report we describe a patient with neurally mediated vasodepressor syncope who developed asystole during head‐up tilt table testing after treatment with a beta blacker.
Double Ventricular Responses to a Single Atrial Depolarization in a Patient with Dual AV Nodal Pathways
Authors: SAKURADA HARUMIZU , SAKAMOTO MASAHIKO , HIYOSHI YASUNAGA , TEJIMA TAMOTSU , MOTOMIYA TAKESHI , SUGIURA MASAYA , HIRAOKA MASAYASU
Published: July 2006

Electrophysiological study was performed in a patient with atrioventricular nodal reentrant tachycardia (AVNRT). Double ventricular responses through dual AV nodal pathways were observed by atrial extrastimulus technique followed by initiation of AVNRT. The drfference in conduction time between the slow and fast AV nodal pathways was longer than 320 msec. A ventricular extrastimulus delivered during sinus rhythm, which was not followed by ventriculoatrial conduction, also induced AVNRT. These findings indicated the presence of an antegrade critical delay and retrograde block in the slow AV nodal pathway, criteria necessary for the occurrence of a double ventricular response.
The Effect of Magnetic Resonance Imagers on Implanted Neurostimulators
Authors: GLEASON CURTIS A. , KAULA NORBERT F. , HRICAK HEDVIG , SCHMIDT RICHARD A. , TANAGHO EMIL A.
Published: July 2006

This in‐vitro study was designed to investigate the safety of various implanted neurostimulators in magnetic resonance (MR) imagers. The effects of the static and changing magnetic fields and the radio frequency (RF) electromagnetic field generated by 0.35 and 2.5 T MR imagers on the voltage output of four models of implantable passive neurostimulafors and two models of implantable self‐powered neurostimulators was studied. The neurostimulators were mounted on a support and placed in the imagers. An oscilloscope monitored the voltages at the outputs of the neurostimulators. For an A very single‐channel stimulator, located at the isocenter, the amplitude of the output pulses induced by the 0.35 T imager was 6V; from a 1.5 T imager, it was 12 V. These amplitudes can cause discomfort and possible harm to a patient if the typical therapeutic value is 1–5 V. The amplitude of the stimulator receiver's output decreased to relatively safe values beyond 40 cm from the isocenter. By contrast, there was no significant voltage output from the Medtronic SE‐4 receiver. For two models of self‐powered neurostimulators, the Medtronic Itrel and the Cordis MK If, the programmed stimulus parameters were not affected by the pulsed magnetic fields of the MR imagers. However, the RF fields at the isocenter heated the metal case of the stimulators. The rotational and linear forces produced by the fixed magnet on the Cordis MK II were judged to be too strong for a patient with this implant to be scanned. The study showed that patients with certain types of implanted neurostimulators can be scanned safely under certain conditions.
Long‐Term Results of Nervous Tissue Alterations Caused by Epineurial Electrode Application: An Experimental Study in Rat Sciatic Nerve
Authors: KOLLER RUPERT , GIRSCH WERNER , LIEGL CHRISTIAN , CRUDER HELMUT , HOLLE JÜRGEN , LOSERT UDO , MAYR WINFRIED , THOMA HERWIG
Published: July 2006

In order to evaluate the long‐term effects of epineurial electrode application for functional electrical stimulation (FES) the left sciatic nerve of seven rats was exposed. Four ring‐shaped stainless steel wire electrodes were sutured to the epineurium of each nerve in the same manner as performed clinically for carrousel stimulation in man. The nerves were reexposed 1 year after implantation and the stimulation threshold to obtain a tetanic contraction in the lower limb was determined for each electrode. Afterwards the animals were sacrificed. The electrodes were excised and cross sections of the sciatic nerve directly at the site of the electrodes, 2‐mm proximal and 2‐mm distal to them were harvested for hisfologic and planimetric assessment of nerve lesions. The area of damaged neural tissue was expressed as a percentage of the total cross‐sectional area within the perineural sheath. The sciatic nerves of the right side served as controls. The values for the stimulation thresholds ranged between 0.1 and 1.0 mA (mean 0.43 mA). By morphometric examination five of seven nerves were seen altered, the altered areas captured between 1% and 4.8% of the total cross‐sectional area of the nerves within the perineural sheath. Besides two specimens, all altered nerve segments exhibited distinct signs of nerve fiber regeneration. The clinical implications of the results for long‐term electrical stimulation, such as phrenic pacing, are discussed.
Atrial Latency in a Dual Chambered Pacing System Causing Inappropriate Sequence of Cardiac Chamber Activation
Authors: GRANT S.C.D. , BENNETT D.H.
Published: July 2006

A transvenous atrioventricular pacemaker was implanted in a patient in whom functional bradycardia and recurrent ventricular tachycardia had occurred after coronary artery bypass surgery. The period between delivery of the atrial stimulus and resultant atrial excitation was prolonged by up to 0.22 seconds and exceeded the programmed delay between atrial and ventricular stimulation. Consequently, ventricular stimulation preceded atrial excitation. Cardiac failure resulted: it was resolved by reprogramming the pacemaker to the atrial inhibited mode.
A Soviet Nuclear Pacemaker
Authors: FREEDBERG NAHUM A. , ANTONELLI DANTE , BLOCK LEV , ROSENFELD TIBERIO
Published: July 2006

A Soviet nuclear pacemaker is described. It is a large VOO bipolar pacemaker, probably nonprogrammable. It has unique electrode connectors. No isotope leak or excessive radiation hazard was detected. Because we had no knowledge of its end‐of‐life markers and because of the impossibility of assuming long‐term safety, the device was removed.
Apparent P Wave Underselling in a DDD Pacemaker Post Exercise
Authors: van GELDER BERRY M. , van MECHELEN ROB , den DULK KAREL , El GAMAL MAMDOUH I.H.
Published: July 2006

Wencke‐bach behavior of DDD pacemakers occurring when the P‐P interval varies between the programmed upper rate interval and the total atrial refractory period is symmetrical in a sense that the pacemaker response during atrial rate acceleration is similar to the pacemaker response during atrial rate deceleration. This phenomenon can be observed in all patients with persistent AV block in whom a DDD pacemaker is implanted, during exercise testing when the spontaneous atrial rate exceeds the selected upper rate, i.e., the programmed upper rate interval. However, this phenomenon will not be observed in all patients with intermittent intact AV conduction during exercise. In this case report we describe a patient who showed an asymmetrical response during a bicycle exercise test. There was 1:1 atrial sensing ventricular pacing until the atrial rate exceeded the upper rate of 140 ppm, while atrial sensing was restored during recovery when the conducted sinus rhythm had decreased to 105 beats/min.
Electrocardiographically Documented Unnecessary, Spontaneous Shocks in 241 Patients With Implantable Cardioverter Defibrillators
Authors: GRIMM WOLFRAM , FLORES BELINDA F. , MARCHLINSKI FRANCIS E.
Published: July 2006

The incidence and cause of electrocardiographically documented spontaneous implantuble Cardioverter defibrillator (ICD) discharges for a rhythm other than ventricular tachycardia (VT) or fibrillation (VF) (unnecessary shocks) were determined in 241 patients who underwent ICD implantation between March 1983 and November 1991. During follow‐up of 24 ± 20 months, 54 of 241 patients (22%) received a total of 132 unnecessary ICD shocks confirmed by Holler or telemetry monitoring or stored electrograms (Egs) from the ICD. The rhythm preceding these unnecessary ICD shocks was atrial fibrillation in 30 patients, sinus or supraventricular tachycardia (SVT) in 11 patients, antitachycardia pacing triggered by atrial fibrillation or SVT resulting in VT in 5 patients, nonsustained VT in 3 patients, and normal sinus or pacemaker rhythm in 10 patients. Unnecessary ICD discharges occurred most frequently during the first week after implantation or generator replacement (18 of 54 patients [33%]). Unnecessary ICD discharges could be documented more often by stored Egs in patients with devices with Eg storage capability (Ventritex Cadence(tm), 19 of 54 patients [35%]) than by Holter or telemetry monitoring in patients with devices without Eg storage capabilities (34 of 193 patients [18%], P < 0.01), despite a shorter mean follow‐up duration of 14 ± 9 months versus 26 ± 21 months, respectively. Only six of 54 patients (11%) in whom unnecessary ICD discharges occurred had recurrent unnecessary shocks during 22 ± 20 months of follow‐up after treatment directed at the cause of the first episode or device reprogramming to preclude non‐VT rhythm detection. In conclusion, unnecessary ICD shocks are a frequent complication of ICD therapy occurring in at least 22% of patients. The cause of these shocks is most frequently atrial fibrillation with a rapid ventricular response. The availability of Eg storage capabilities facilitates the diagnosis of the electrical event precipitating inappropriate ICD shocks. Diagnosis of the cause of unnecessary shocks allows for the institution of therapy that may reduce the risk for subsequent events.
In Anterior Myocardial Infarction, Frequency Domain is Better than Time Domain Analysis of the Signal‐Averaged ECG for Identifying Patients at Risk for Sustained Ventricular Tachycardia
Authors: BUCKINGHAM THOMAS A. , GREENWALT TERRY , LINGLE ANGELA , VOLGMAN ANNABELLE S. , KOBER PHILLIP , JANOSIK DENISE , ZBILUT JOSEPH P.
Published: July 2006

Low amplitude signals at the end of the QRS in patients with prior myocardial infarction (MI) are related to fragmentation of the electrical impulse in ventricular myocardium and are known to correlate with an increased risk of sustained ventricular tachycardia (VT). We hypothesized that in patients with anterior MI (AMI), earlier activation of the damaged anterior wall would cause an earlier fragmentation of the signal‐averaged EGG (SAECG) signal, making conventional time domain analysis of late potentials difficult. We performed SAECG in 213 patients (62 with AMI and 58 with inferior MI [IMI]). Fifty‐seven had prior sustained VT; 23 with AMI and 24 with IMI. We examined the standard time domain SAECG parameters including the duration of the filtered QRS (40–250 Hz), the duration of the late QRS < 40 μV, and the root mean square amplitude of the last 40 msec of the QRS. We also examined the power law scaling (PLS) in the frequency domain. Receiver operating characteristic curve analysis of a discriminant function demonstrated significant differences for PLS as compared to time domain indices. An important finding was the significance of MI locus in the time domain indices. PLS did not exhibit this dependence. These data suggest that the usual indices are insufficient for identifying AMI patients at risk of VT. PLS, on the other hand, is valuable regardless of MI location.
Usefulness and Adequacy of Sensor Data Storage and Retrieval for Rate Response Simulation
Authors: MAHAUX VERONIQUE , WALEFFE ANDRE , KULBERTUS HENRI
Published: July 2006

The usefulness of sensor data storage for rate response simulation was evaluated using a new dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay 294–03 [lntermedics Inc.]). The pacemaker can store the sensor output during routine exercise and those values can be used to simulate rate profiles for other rate response settings. The predictive value of this feature was evaluated in three studies (mechanical, external pacemaker, and implanted pacemaker). In the first study, the pacemaker was submitted to three runs of eight different mechanical calibrated to‐and‐fro movements. In the second study, nine external pacemakers were strapped on healthy volunteers who performed three jogging tests. Finally, the predictive value of the simulation was studied in five implanted patients during three successive walking tests. In each study, the pacemaker was submitted three times to the same activity. The responsiveness was successively set to 5, 1, and 10, and the pacemaker outputs were continuously recorded on a Holter monitor. At the end of the first run, rate profile simulations for slopes 1 and 10 were performed; slope 5 rate response was simulated after the second run. A regression analysis was used to establish the correlation between predicted and achieved pacing rates for each study. The coefficients of correlation between predicted and measured pacing rates for the mechanical, external, and clinical studies were 0.999, 0.985, and 0.823, respectively. The corresponding slopes of regression lines were 1.005, 0.971, and 0.935. Calculated rate profile has a high predictive value and could be used to optimize rate responsive settings without serial exercise testings.
Dissociation of Atrioventricular Conduction and Refractoriness Following Application of Radiofrequency Energy to the Canine Atrioventricular Node: Acute and Chronic Observations
Authors: MARCUS FRANK I. , BLOUIN LEONARD T. , BHARATI SAROJA , LEV MAURICE , HAHN ELIZABETH
Published: July 2006

The electrophysiology of AV nodal modification induced by radiofrequency energy (n = 5) or a sham procedure (n = 5) was studied in ten dogs. The five dogs that received radiofrequency energy had an AH prolongation > 100% from baseline values and this prolongation persisted throughout the 2‐month study. The AV nodal functional refractory period was prolonged only acutely. These data indicate a dissociation between the effects on AV nodal conduction and refractoriness that was induced by this procedure. The five sham treated controls showed no acute or chronic electrophysiological changes. In the dogs that received radiofrequency energy, there was fibrosis of the approaches to the AV node and the region of the A V node itself. It is concluded that chronic modification of AV nodal conduction without concomitant changes in refractoriness can be induced by radiofrequency energy delivered in the proximal portion of the AV node. It would be anticipated that this procedure would not decrease the ventricular response to atrial fibrillation or flutter, but may be effective in preventing AV nodal reentrant tachycardia by interfering with conduction either in the AV node or perinodal region. Since the AV node itself suffers at least moderate pathological damage, there may be an appreciable incidence of the late development of complete heart block after this procedure.
Effects of Defibrillation Shocks Delivered Directly Over a Major Coronary Artery
Authors: LUCY S. DEBORAH , JONES DOUGLAS L. , KLEIN GEORGE J.
Published: July 2006

This study investigated the influence of defibrillator shocks delivered directly over a coronary artery, independent of ventricular fibrillation, on cardiac hemodynamics. Thirty‐six open chest, halothane anesthetized pigs were randomized to receive six shocks at one of 5,0, 7.5, or 10.0 joules (J). Shocks were delivered between two mesh electrodes (Medtronic TX‐7) sutured onto the epicardium, one over the left anterior descending coronary artery and the second directly opposite on the posterobasal ventricular surface. Shock delivery was synchronized to the R wave of the cardiac cycle, to reduce the risk of inducing fibrillation, with a 5‐minute stabilization period between successive shocks. Pressure from the left ventricle, the left anterior descending coronary artery, distal to the mesh electrode and the left circumflex (control) artery and contractility in the regions perfused by both arteries were measured. The shocks invariably produced an immediate (2‐second postshock), but transient, depression in systolic pressure of the same magnitude for the left anterior descending coronary artery, circumflex artery and the left ventricle that recovered by 5‐minute postshock. There was no dose dependent relationship to energy. Also there was no clear difference in myocardial wall motion between the area perfused by the left anterior descending coronary artery and that perfused by the circumflex artery. These results suggest that shocks up to 10 J delivered over an epicardial artery do not cause arterial spasm and do not compromise coronary artery blood flow.
Familial Congenital Sinus Rhythm Anomalies: Clinical and Pathological Correlations
Authors: BHARATI SAROJA , SURAWICZ BORYS , VIDAILLET HUMBERTO J. , LEV MAURICE
Published: July 2006

We describe pathological abnormalities in a 72‐year‐old male member of a family with a congenital absence of sinus rhythm and a tendency to develop atrial fibrillation at an early age, and in a 54‐year‐old female member of a family with cardiomyopathy and progressive conduction system disease manifested by first‐degree atrioventricular (AV) block, left bundle branch block, and atrial arrhythmias. Both patients died suddenly. The absence of sinus rhythm in case 1 could be explained by marked atrophy, degeneration, and isolation of the sinoatrial (SA) node. The SA node was also diseased in the member of the other family with atrial arrhythmias. Additional common features in both cases included: fatty metamorphosis and degenerative changes of the approaches to the SA node, the atrial preferential fibers, and the approaches to the AV node, a small AV node, degenerative changes of the bundle branches, and floppy AV valves. These findings show that the pathological substrate of familial supraventricular arrhythmias consists of a diffuse involvement of the entire conduction system, bearing resemblance to pathological findings in elderly subjects with acquired sick sinus syndrome.
Factors Predicting Success in DC Catheter Ablation of Accessory Pathways
Authors: ADRAGAO P. , EVANS S. , IWA T. , TONET J. , FRANK R. , FONTAINE G.
Published: July 2006

In a series of 33 patients with accessory pathways, 26 had successful catheter ablation (fulguration [23 patients] or modification [3 patients]) of their accessory pathway conduction, and could be considered as a clinical success. One hundred thirteen single discharge or double discharge shocks were delivered, and each shock was studied to reveal which parameters were important to predict the success or failure of catheter ablation. Double discharge shocks resulted in successful accessory pathway modification or ablation twice as often as single discharge shocks (32% vs 16%). This effect was more pronounced in left lateral accessory pathways (48% vs 4%). Shocks in the electro physiologically defined ventricular zone were more likely to be successful (33%) than shocks delivered in the atrial zone (14%), irrespective of accessory pathway location. The presence of a probable Kent potential was the parameter most strongly associated with success. The parameter most strongly associated with failure, with a 100% negative predictive value, was the absence of earliest activation recorded on the ablating catheter prior to shock delivery. An AV interval of < 60 msec significantly divided the successful from the unsuccessful shocks (P = 0.01). The VA interval during orthodromic reciprocating tachycardia or right ventricular stimulation did not allow for significant division into successful and unsuccessful attempts in this relatively short series. VA intervals, when longer, were predictive of failure but, when shorter, had low positive predictive value. Mean follow‐up in 25 successful patients was 15 ± 6 months. All patients did well in the followup period. Neither those patients with ablation nor modification of the accessory pathway had recurrent episodes of tachycardia or required pharmacological treatment for control of arrhythmias.
Late Potentials in a Porcine Model of Anterior Wall Myocardial Infarction and Their Relation to Inducible Ventricular Tachycardia
Authors: TOBÉ TOM J.M. , de LANGEN GEES D.J. , MOOK PIET H. , TIO RENÉ A. , BEL KLAAS J. , de GRAEFF PIETER A. , van GILST WIEK H. , WESSELING HARRY
Published: July 2006

In this study, normal values for signal averaged electrocardiographic parameters were assessed in healthy pigs (n = 100) and the development of late potentials after myocardial infarction (n ‐ 41) in relation to inducible ventricular tachycardia was investigated. Normal values are: filtered QHS duration (QRS) ± 78 msec; root mean square voltage of the averaged QRS complex (Vtot) ± 51 μV, and duration of terminal activity below 30 μV (D30) ± 37 msec. The distribution of the root mean square voitage in the last 30 msec (V30) was biphasic. Two weeks after myocardial infarction, QRS was prolonged from 55 ± 10 to 66 ± 19 msec (P < 0.002), D30 was prolonged from 19 ± 6 msec to 28 ± 13 (P < 0.002). V30 was decreased from 107 ± 135 μV to 45 ± 77 (P < 0.02). The total voltage (Vtot) was decreased from 195 ± 78 to 123 ± 61 μV (P < 0.002). In four pigs (19%) late potentials developed. Sustained ventricular tachycardia was inducible in 11 pigs (52%), ventricular fibrillation in two pigs (10%) and eight pigs (38%) were noninducible. Three of 11 inducible pigs and one of the noninducible pigs had a late potential. The incidence of late potentials and their relation to inducibie sustained ventricular tachycardia is comparable to the situation in man. Therefore, this pig model is an attractive alternative to the commonly used dog models.
Intracardiac Impedance to Determine Sympathetic Activity in Rate Responsive Pacing
Authors: SCHALDACH M. , HUTTEN H.
Published: July 2006

Modern pacemaker technology renders possible the adaptation of pacing rate to hemodynamic requirements. The most ambitious approach aims at restoration of the physiological closed‐loop system lay utilizing the information supplied by the autonomic nervous system (ANS) and extracted from myocardial contractile performance. Measurement is accomplished by the impedance method using the stimulation electrode as the measuring electrode. The ventricular inotropic parameter (VIP) has been identified as an ANS dependent parameter. A special detection algorithm, regional effective slope quantity (RQ), with high ANS sensitivity has been developed. Rate adaptation has been achieved by using an individually adjustable inotropic index (II). The concept has been evaluated in a multicenter study using a standardized exercise protocol. The results in patients with AV block demonstrate excellent agreement between spontaneous sinus rhythm and the ANS‐controlled stimulation rate during different forms of exercise. Measurement of mean arterial blood pressure (MABP) supports the physiological approach of adapting the pacing rate to various types of hemodynamic challenges.
Identifying Patients for Rate Responsive Atrial Pacing: A New Method for Patient Selection and Pacemaker Programming
Authors: de COCK CAREL C. , KAMP O. , MEIJER A.
Published: July 2006

In patients with sinus node disease (SND) and chronotropic incompetence, atrial rate adaptive stimulation (AAI, R pacing) is regarded as the most appropriate pacing mode. Since coronary artery disease is the most common etiology in these patients, we evaluated a new technique combining two‐dimensional transesophageal echocardiography and atrial transesophageal pacing to detect pacing induced wall motion abnormalities and assess safe upper rate limits. Thirty‐five patients were studied; 26 with and 9 without angiographic coronary artery disease. Stable atrial capture was achieved in all patients using 12 ± 3 msec pulse width and 12 ± 4 mA current strength. Sensitivity and specificity for the detection of coronary artery disease was highest for transesophageal echocardiography during pacing (sensitivity 81%, specificity 100%). Simultaneous 12‐lead ECG during pacing had lower values (sensitivity 57%, specificity 75%). Pacing induced wall motion abnormalities preceded ST segment changes in all patients. Exercise stress testing showed similar values (sensitivity 62%, specificity 89%), It is concluded that simultaneous transesophageal echocardiography and transesophageal pacing is a safe and useful technique in selecting patients for AAI, R pacing and for the detection of safe upper rate limits, particularly when coronary artery disease is suspected.
A New Acceleration Driven Pacemaker: Rate Modulation Versus Normal Sinus Rhythm—Comparison During Treadmill Exercise
Authors: SOUSSOU ADEL ISSA , HELMY MOHAMED GAMAL , GUINDY RAMEZ RAOUF , GRECO ENRICO MARIA
Published: July 2006

The pocing rate response of a new acceleration driven pulse generator (SWING 100, SORIN BIOMEDICA) was compared with simultaneous normal sinus rhythm (NSR) during two different treadmill exercises. This pacemaker has a gravitational acceleration sensor able to discriminate between physical activities and vibrations. Six healthy volunteers (three male, three female; aged 21.7 ± 4,3 years), with the pacemaker strapped to their right infraclavicular area, performed each test three times with different rise response curve (RRC) each time: fast, normal, and slow. The fall response curve used was the same as the rising one during each test. Pacing rates were recorded using the VEGA analyzer (SORIN BIOMEDICA) and compared with simultaneous NSR recorded by a 7‐channel ECG recorder (MINGOGRAF 7, SIEMENS), During all tests immediate (within seconds) rapid increase in pacemaker rate was seen up to about 60 seconds, then a slower increase followed thereafter. The mean correlation between pacing rates and NSR during the Bruce tests were 0.7941 ± 0.10, 0.8562 ± 0.14, and 0.8292 ± 0.07; during the discontinous tests 0.7292 ± 0.16, 0.7233 ± 0.10, and 0.7480 ± 0.11 for fast, normal, and slow RRC, respectively. Each 30 seconds, nonsignificant differences were present between pacing rate and NSR during all the discontinuous tests; similar responses were observed only during the first two stages of Bruce tests after which NSR was significantly higher than pacemaker rates. The speed of rise to upper rate was the main difference between the different programs (fast, normal, and slow). The discontinuous tests showed that the pacemaker responds more to speed than to grade. In conclusion, the Swing pacemaker is easy to use and program, fast, reliable, and is able to mimic the normal sinus behavior especially during discontinuous activities.
A New Motion Responsive Pacemaker: First Clinical Experience with an Acceleration Sensor Pacemaker
Authors: BORST U. , SIEKMEYER G. , MAISCH B. , KAYE S.
Published: July 2006

A new accelerometer‐based adaptive rate pacemaker (OEXCELVRTM) was evaluated to investigate its behavior at nominal settings during treadmill exercise testing and postural changes. Eight patients with sinus rhythm were selected to compare intrinsic heart rate to sensor mediated rate. Throughout exercise treadmill testing, changes in the sensor mediated rate closely paralleled actual physiological changes. The Pearson product moment correlation of pacing rate with sinus frequency, calculated for all patients, was r = 0.82 (P = 0.001). Change in the patient's physical position resulted in immediate change in sensor rate, which corresponded appropriately to the type of position change and activity level. Average (± SD) pacing rate was 62.4 ± 2.7 beats/min supine; 67 ± 3.8 beats/min sitting; 69.8 ± 6.4 beats/min standing; 81.6 ± 8.7 beats/min slow walking; and 96.8 ± 1.3 beats/min fast walking. After 4 minutes of recovery, the average pacing rate dropped to 65 ± 3 beats/min. The interaction between the accelerameter and the pulse generator at nominal settings was accurate and infrequently required the use of its many programming options. The accelerometer sensor and pulse generator algorithm in this device during postural change and exercise resulted in physiological‐like changes in sensor mediated heart rate.
Clinical Observations with a Dual Sensor Rate Adaptive Single Chamber Pacemaker
Authors: PROVENIER FRANK , van ACKER ROLAND , BACKERS JOS , van WASSENHOVE ETIENNE , de MEYER VEERLE , JORDAENS LUC
Published: July 2006

The Topaz model 515 (Vitatron B.V.) is a dual sensor rate responsive pacemaker for single chamber stimulation. It can be driven by activity counts (ACT) and QT interval measurements. Inappropriate rate modulation due to one sensor can be corrected by “sensor cross‐checking.” It was implanted in ten patients (20‐86 years) of whom seven had complete heart block and atrial arrhythmias. After implantation T‐wave amplitude ranged from 0.9mV‐3.5 mV. T‐wave sensing ranged from 88%–99% in 9/10 patients at the follow‐up of 3 weeks. Eight patients remained in default setting of the activity threshold, after evaluation with a short walking test. An exercise test was performed on all patients. In one test, QT sensing was marginal because of lead implantation in the right ventricular outflow tract. Therefore, this pacing rate was only modulated by ACT sensing. All others were tested with equal contribution of information from both sensors (ACT = QT). In 7/9, rate response was satisfactory. When the treadmill was repeated with ACT in five of these seven patients, rate generally accelerated too fast. In one patient the setting was adjusted to “QT > ACT,” because of inappropriate acceleration due to activity sensing, in another it was adjusted to “QT < ACT” because of delayed response to activity. The pacing rate and the ACT during treadmill tests in “QT = ACT” mode were more closely correlated in the first 3 minutes, compared with the last 3 minutes. We feel that rate modulation with this new pacemaker is adequate. Sensor blending and sensor cross‐checking are of clinical importance.
Follow‐Up of a Minute Ventilation Rate Adaptive Pacemaker
Authors: LI HUI , NEUBAUER SHARON A. , HAYES DAVID L.
Published: July 2006

Although rate adaptive pacemakers are now frequently prescribed, there is limited information regarding long‐term follow‐up of patients with a pacemaker capable of rate adaptation. We have examined our patients in whom a pacemaker capable of rate adaptation via a sensor that determines minute ventilation has been implanted. After following a group of 42 patients for a mean of 13.2 months we have found this to be a reliable rate adaptive pacing system. The sensor was reliable long term, the system is easy to program, and sensor settings were changed infrequently.
Clinical Experience with a New Multiprogrammable Dual Chamber Pacemaker
Authors: KUTALEK STEVEN P. , SCHUSTER MELINDA M. , HESSEN SCOTT E. , SHEPPARD ROBERT , MAQUILAN MARCH , NYDEGGER CHARLES
Published: July 2006

We evaluated the clinical performance of a new dual chamber pacemaker, ELA Chorus(tm), in 35 patients. This device incorporates linear rate adaptive AV delay (AVDR), rate smoothing, fallback, impedance telemetry, pacemaker mediated tachycardia (PMT) recognition and reprogramming software, intracardiac electrogram displays, aufothreshold testing, diagnostic data, battery depletion curves, and laptop computer programming. Mean patient age was 68 years; 18 patients had AV block, six had sinus node dysfunction (one with AV block), nine had carotid sinus hypersensitivity (three with AV block), and two had vagally mediated syncope. At hospital discharge, programming was DDD with a mean low rate of 60 (50–70) beats/min, mean high rate of 126 (120–154) beats/mm; AVDR was ON in 21 patients, rate smoothing ON in six patients, fallback ON in six patients, and PMT reprogramming algorithm ON in 27 patients, Pacemaker follow‐up involved 500 clinic visits over 14.3 months (1–36). Three patients developed atrial fibrillation, reprogrammed to DDI mode (two patients) or fallback (one patient). Fallback was used 617 times. PMT occurred 427 times in six patients; the PMT algorithm reprogrammed AV delay and postventricular atrial refractory period (PVARPJ automatically, a function unique to the Chorus(tm). Intracardiac electrograms and autothreshold testing improved follow‐up efficiency. This new dual chamber pacemaker enhances programming flexibility and improves diagnostic accuracy at follow‐up.
Facilitation of DDD Follow‐Up Using the DDT Mode
Authors: KAMKE W. , NITSCHKE M. , GUTSCHKER A. , WORZEWSKI W.
Published: July 2006

To facilitate follow‐up, modern dual chamber pacemakers provide a variety of diagnostic features like ECG interpretation channels and intracardiac electrograms, For evaluation of the sensing performance at rest and during exercise, for assessment of the presence of crosstalk, and for measurement of the retrograde conduction time, dual chamber triggered pacing, particularly the DDT mode, can be used alternatively or additionally in pacemakers equipped with this option. In contrast to ECG interpretation channels, ECG documentation is riot required for evaluation of the sensing performance, because the triggered pulses serving as markers for sense events can also be seen on the monitor. Selection of the DDT mode not only as temporary but also as permanent program serves to facilitate pacemaker EGG interpretation for exercise tests and Holter recordings as well.