bluuebunny/crossref_metadata_2025 huggingface dataset:
Filter Characteristics of the Atrial Sensing Circuit of a Rate Responsive Pacemaker. To See or Not to See
Authors: AUBERT ANDRÉ E. , GOLDREYER BRUCE N. , WYMAN MILFORD E. , JACQUEMLYN ERIK , ECTOR HUGO , DE GEEST HILAIRE
Published: July 2006

The intra‐atrial electrograms (P waves) from floating orthogonal atrial electrodes of acutely implanted pacemaker leads (SRT lead) were recorded and the frequency characteristics were determined. The atrial sensing properties of the rate responsive pacemaker (RS4) used in conjunction with these leads, were studied in relation to the frequency spectra of atrial electrograms. Whereas the P waves showed a bandwidth to 65 Hz, the filter had an upper cutoff frequency of 35 Hz. We conclude that unreliable atrial sensing with the RS4‐SRT pacing system is primarily due to an inappropriate filter match and therefore no satisfactory rate responsiveness is achieved.
Fusion with the Prolonged First Postpacing Interval in Pacing of Ventricular Tachycardia
Authors: AIZAWA Y. , SATOH M. , SHIBATA A. , JOSEPHSON M.E.
Published: July 2006

In cases of recurrent sustained ventricular tachycardia (VT), constant fusion and progressive fusion in fhe surface electrogram were observed during overdrive pacing of VT. However, following cessation of pacing, the return cycle of VT (stimulus to the first nonpaced QRS) was longer than the VT cycle length. This phenomenon can be explained by orthodromic capture of the exit site of the VT current with a conduction time (stimulus to QRS) exceeding the VT cyde length. This site can therefore be activated during entrainment of VT during the mid‐to‐terminal portion of the paced QRS complex, resulting in constant fusion.
Spinal Cord Stimulation (SCS) in Deafferentation Pain
Authors: MEGLIO M. , CIONI B. , PREZIOSO A. , TALAMONTI G.
Published: July 2006

Spinal cord stimulation is considered to be ineffective in relieving deafferentation pain. We have retrospectively analyzed the results obtained in a series of 41 patients. Sixteen suffered from pain associated with an incomplete traumatic spinaJ lesion, 15 from a posttherapeutic neuralgia, and 10 from pain due to root and/or nerve damage. At the end of the test period, 43.7% of the patients with paraplegic pain, (40% of those with peripheral deafferentation pain and 66.6% of the ones with postherapeutic neuralgia), reported satisfactory pain relief and were connected to a chronic stimulation system. At mean follow‐up (15 months), only 20% of the patients of the first two groups reported sufficient pain relief In the postherapeutic group the figure of responders was unchanged. The mean analgesia achieved was 70%. From this analysis we conclude that the results achieved in the postherapeutic pain patients, although positive in only 66% of them, are remarkably stable with time. Therefore, we recommend a percutaneous test trial of SCS in every case of postherapeutic pain resistant to medical treatment.
Effects of Dorsal Column Spinal Cord Stimulation (DCS) on Reversibility of Neuronal Function—Experience of Treatment for Vegetative States
Authors: KANNO TETSUO , KAMEL YOSHIFUMI , YOKOYAMA TETSUYA , SHODA MOTOI , TANJI HIDEAKI , NOMURA MASAHIKO
Published: July 2006

We have reported that DCS (dorsal column stimulation) improves the clinical symptoms of cases in persistent vegetative states. Since then, we have accumulated 23 cases who have been treated by DCS. We describe the clinical EEG, rCBF, and biochemical changes in cerebrospinal fluid (CSF) caused by DCS in patients in persistent vegetative states; (1) eight of these cases showed good clinical improvement; (2) most patients were young and the CTscan did not show large, diffuse, definite or bilateral low density areas in cortex, brainstem of thalmus; (3) neurostimulation increased rCBF (cerebral blood flow) in many parts of the brain in cases with vegetative states; blood flow increased in the cerebrum, cerebellum and brainstem; (4) neurostimuiation enhanced the metabolism of catecholamines in CSF, NE, DA, DOPAC, HVA, and 5H1AA increased, but 3MT and 5HT decreased in CSF. DCS increased rCBF, enhanced the metabolism of catecholamines in CSF, and improved the EEG in patients in persistent vegetative states.
MINIMAC: A Totally Numeric 15 Channel Implanted Stimulator
Authors: CHOUARD C.H. , WEBER J.L.
Published: July 2006

After CHORIMAC‐8 and CHORIMAC‐12 a new multichannel cochlear implant is presented, characterized by its totally numeric sound signal processing. Owing to FFT the whole speech information is cut into 15 channels, then sequentially transmitted to an implanted receptor and electrode bearer. This digital processing provides the new system with several advantages: 1. miniaturization of outside emitter end implanted receiver; 2. compatibility of this new emitter with the 12 channel receivers implanted in the last 10 years; 3. increasing the number of stimulating electrodes from 12 to 15; 4. simple emitter programming with an IBM‐PC; 5. option to postoperatively program the number (1 to 15) and (he value (80 to 3,800 Hz) of the peak filters, and the amplification (6, 10, 18 dB) of each electrode. The next implanted device will have: a. constant current; b. programming of a particular current value for each electrode; and c. stimulation of the cochlear nerve through an extra cochlear electrode bearer, allowing deep implantation without deafness.
Pyramid Electrode Location in a Cardiac Micropotential Study
Authors: KEPSKI ROMAN , WALCZAK FRANK
Published: July 2006

There are several electrode systems dealing with low noise, body surface, and ECG recordings that have been suggested by various investigators. In the last few years, the most developed system for late potential detection has been related to the uncorrected Frank XYZ leads. However, for His bundle defection many different electrode networks have been used. A pyramid‐type electrode system has been used previously for His‐Purkinje signal measurement and, with some modifications, for late ventricular activity recordings. This pyramidtype system was used to evaluate 300 adult patients with coronary heart disease (CHD) or cardiomyopathy. In the proposed system, electrodes are located near the myocardium with their configuration consisting of three electrode pairs forming a pyramidal shape. Each electrode can also play the role of the top of the pyramid, with all measurement directions converging to a point. By changing the pyramidal top, signals can be defected in various chosen measurement directions. The pyramid system provides spatial averaging facility, allowing the whole measuring sysfem (consisting of low noise multi‐input amplifiers) to defect signals in fhe range of lμVp‐p on a beat‐to‐beat basis. In the majority of cases in hospital environments, however, a number of digital averaging cycles is still necessary. Using this system, late potentials (LP) were found in 29% of the patients without myocardial infarction (MI) and in 86% of cases with remote MI and sustained ventricular tachycardia (VT) and/or ventricular fibrillation (VF). Waveforms suspected to be of His‐Purkinje System (HPS) origin were detected in 71% of subjects with normal or prolonged P‐R segment.
The Reliability of Rate‐Pressure Product as an Index of Myocardial Oxygen Consumption in Atrial Synchronized Versus Fixed Rate Ventricular Pacing
Authors: NORDLANDER ROLF , PEHRSSON S. KENNETH , ASTROM HANS
Published: July 2006

Consumption in Atrial Synchronized Versus Fixed Rate Ventricular Pacing. The product of heart rate and blood pressure was tested as an index of myocardia] oxygen consumption (MVO2J and compared with directly determinisd MVO2 during ventricular demand fWI] fixed rate pacing and atrial synchronized (VAT] pacing at rest and during exercise. Systolic brachial artery pressure, pulmonary wedge pressure and MVO2 were similar in the two pacing modes and showed similar response to exercise. The correlation between rate‐pressure product and MVO2 was closer with VAT than with WI pacing (r = 0.74 and r = 0.64, respectively], and the latter value was not improved by using the product of atrial rate and systolic pressure (r = 0.61). The rate‐pressure product was significantly higher during VAT pacing compared to WI during exercise, although MVO2 was similar. The similarity of MVO2 during exercise indicated some other contributory factor than heart rate in WI pacing, probably increase of contractility and/or volume. Because such factors are not included in currently used indices of MVO2 assessments must be interpreted cautiously, particularly in cases of complete heart block with WI pacing.
Atrial Inhibited Pacing in the Sick Sinus Node Syndrome: Clinical Value and the Demand for Rate Responsiveness
Authors: KALLRYD ANDERS , KRUSE IB , RYDÉN LARS
Published: July 2006

A consecutive series of 66 patients(males = 32; mean age ± SD = 71 ± 9 years) given atrial inhibited pacemakers for sick sinus nodes were followed to study the incidence of lead failures, chronic atriai tachyarrhythmias, and atrioventricular conduction disturbances. The need for rate responsive pacing was also assessed. Pre and postoperative investigation could include carotid sinus massage, Holter monitoring, exercise testing, and invasive electrophysiology. The mean follow‐up time ± SD was 32± 29 months (median = 26 months). Three patients (5%) had their pacemakers replaced due to lead failures (loss of sensing = 2; exit block = 1). Two pacemakers (3%) were replaced after 5 and 22 months due to atrial fibrillation. Four patients (6%) received new pacemakers because of development of seconddegree or complete atrioventricular block after 1,6, 12, and 31 months, respectively. During exercise, most patients (76%) responded with an increase in sinus rate at least as marked as that achievable with the currentiy available rate responsive pacemakers. Assuming careful patient seiection, atrial inhibited pacing is well suited for many patients with sinus node dysfunction and preserved atrioventricuiar conduction. There is a limited need for rate responsive pacemakers in these patients.
Right Ventricular Tachycardia with Left Bundle Branch Block and Inferior Axis Morphology: Clinical and Arrhythmological Characteristics in 15 Patients
Authors: PROCLEMER ALESSANDRO , CIANI ROSANNA , FERUGLIO GIORGIO A.
Published: July 2006

Fifteen patients (mean age 30) presenting with right ventricular tachycardia (VT) of the outflow tract type (left bundle branch block with inferior axis morphology), in the absence of obvious organic heart disease, were studied. Seven patients had palpitations, one presyncope and seven were asymptomatic. The echo and/or angiographic findings were normal in 11 patients (73%), suggesting arrhythmogenic right ventricular dysplasia (ARVD) in three (20%) and dubious in one (7%). The VT was sustained in three patients (20%), nonsustained (11 ± 6 beats) in twelve (80%), inducible during exercise in two out of 15 patients (13%) and with ventricular stimulation in one out of eight (12.5%). Four patients were treated with sotalol, three with Class IC drugs and one with amiodarone. At follow‐up of 36± 30 months, only three patients had VT recurrences due to drug withdrawal. In conclusion: (l) abnormal echo and/or angiographic findings suggested that ARVD was observed in a minority of the patients (22%); (2) the low inducibiiity of VT and the good response to sotalol suggested a possible mechanism of abnormal automaticity; and (3) at a 3‐year follow‐up the prognosis appeared to be good in both patients with or without echo‐angiographic signs suggestive of right ventricular dysplasia.
Intermittent Oversensing due to Internal Insulation Damage of Temperature Sensing Rate Responsive Pacemaker Lead in Subclavian Venipuncture Method
Authors: ARAKAWA MICHIO , KAMBARA KENJIRO , ITO HIROYASU , HIRAKAWA SENRI , UMEDA SHOUGO , HIROSE HAJIME
Published: July 2006

A 49‐year‐old male patient developed sensing failure (oversensing) 6 months after the implantation of a temperature sensing rate responsive pacemaker by the subclavian venipuncture method. Intermittent oversensing appeared in the sitting position, but did not appear in the supine position. Temperature telemetry showed an excessive fluctuation of the temperature data points while sitting and while doing a treadmill exercise test. Internal insulation damage was found approximately 33 cm from the distal tip of the expianted lead. The electrical resistance between one thermistor coil and the pacing coil changed from 9 kiloohms to 40 ohms when moderate pressure was applied to the outside lead in the fault area. This electrical shunt resulted from internal insulation damage that resulted from compression of the pacemaker lead between the first rib and the clavicle.
Focal Right Atrial Dysplasia and Atrial Flutter in a Patient with Myotonic Dystrophy
Authors: PICKERING J.G. , GUIRAUDON C. , KLEIN G.J.
Published: July 2006

Focal dysplasia of the right atrium was identified postmortem in a 22‐year‐old man with myotonic dystrophy and sudden death. Antemortem cardiac abnormalities included a single syncopal episode associated with atrial flutter with exercise‐induced 1:1 atrioventricular conduction, sinus node dysfunction, and mild mitral valve prolapse. Pathologically there was only mild conduction system disease and the ventricular myocardium was normal. Right atrial dysplasia, previously unreported in myotonic dystrophy, appears to have been an arrhythmogenic lesion in this patient, serving as a morphological substrate for reentry.
Clinical Experience with a New Activity Sensing Rate Modulated Pacemaker using Autoprogrammability
Authors: MAHAUX V. , WALEFFE A. , KULBERTUS H.E.
Published: July 2006

Sensolog 703 is a new single chamber activity sensing rate modulated pacemaker that offers an automatic adjustment of settings called Autoset. Units were implanted in 11 patients (mean age: 67 years) for atrioventricular block (two patients), sinoatrial block (three patients), sick sinus syndrome (four patients), chronotropic incompetence (one patient), and atrial fibrillation with slow ventricular response (one patient). The devices were programmed in VVIR mode using Autoset. The accuracy of the settings was verified by the built‐in histogram function. In 6/11 patients, these settings were not satisfactory. Autoset was repeated at 6 months (nine patients) and 10 months (five patients) after implantation. External telemetric recordings daring daily life activities, Holter monitoring, bicycle or treadmill stress tests helped in the evaluation of the rate response obtained with the automatic programming. The following problems were encountered: maximum pacing rate for a low level of exercise (four patients), insufficient rate increase (four patients), higher pacing rate daring low than daring heavy exercises (four patients). A time‐consuming (15 to 48 minutes) manual programming was necessary in eight out of nine patients (6 months) and five out of five patients (10 months). In our study, Sensolog 703 algorithm tended to behave as an on/off system; automatic programming was time consuming and only indicative.
Properties of Ultrasonically Marked Leads
Authors: BREYER BRANKO , FEREK‐PETRIC BOZIDAR , CIKES IVO
Published: July 2006

We have developed an ultrasonic marking system for pacing leads and the electrophysiological study of catheters. The aim of this study was to evaluate the accuracy of our system, its usability in the measurement of performance if implanted leads, and to investigate the potential of electrical shock and ultrasonic hazard. The measurements have shown that different applications require specific electronic design, involving some compromise between accuracy and sensitivity. A higher sensitivity at the beginning 0/ the uitrasonicaJiy guided cardiac lead impiantation yields poorer accuracy. Quantitative measurements show that accuracy can be subsequently improved by reduction of sensitivity of the marking system. The transponder marking circuit is better suited for general use and the passive electronic circuit is better suited for multiple electrode electrophysiologicai studies. Experiments concerning electrical safety show that in the worst failure case, the energy of the marking system released within the heart is <10‐9J per pulse within the pacing frequency spectrum and the current was below 50 microamperes. Ultrasound intensities were within the safety limits set by international and national organizations. The experiments using the marking system for detection of the pacing lead failure showed that the system can yield an early warning of the lead malfunction. The system con significantly reduce the exposure of the medical staff and the patients to x rays as well as improve patient follow‐up accuracy.
Pharmacological Characterization of Conduction Over a Mahaim Fiber: Evidence for Adenosine Sensitive Conduction
Authors: ELLENBOGEN KENNETH A. , ROGERS REGINA , OLD WAYNE
Published: July 2006

The presence of a nodoventricular pathway (Mahaim fiber) has been invoked to explain certain distinctive electrocardiographic and electrophysiological observations. The presence of an atrioventricular or atriofascicular fiber with decremental conduction properties has been documented in many of these patients. We report the case of a patient with a Mahaim fiber and the response to conduction over this pathway after adenosine, procainamide, encainide, verapamil, edrophonium, phenylephrine and isoproterenol. Conduction over the Mahaim fiber was blocked by adenosine, but not verapamil. The time course of adenosine induced block over the Mahaim fiber differed from adenosine induced AV nodal block. Mahaim fibers are decrementally conducting pathways that are adenosine sensitive. These findings support the concept that conduction in accessory pathways manifesting decremental properties is not mediated by the calcium channel.
Efficacy and Safety of Rate Responsive Pacing in Patients with Coronary Artery Disease and Angina Pectoris
Authors: DE COCK CAREL C. , PANIS JAN H.C. , VAN EENIGE MACHIEL J. , ROOS JAN P.
Published: July 2006

The present study included 17 patients with angina pectoris and coronary artery disease in whom a rate responsive ventricular pacemaker (Medtronic Activitrax) had been implanted. All patients had an exclusively paced rhythm. Single blinded, random, cross‐over treadmill tests in the rate responsive pacing mode (VVIR) and in the fixed‐rate demand mode (VVI) were performed, with an interval of 4–6 weeks. Mean exercise duration increased by 25% during VVIR pacing. Maximal heart rate increased significantly during VVIR compared to VVI pacing (VVI = 74 ± 2 bpm, VVIR = 116 ± 8 bpm, P < 0.001) as did the rate‐pressure product (VVI = 10.850 ± 1,124, VVIR = 16.628 ± 2,110, P < 0.001). Despite improved performance, the number of anginal attacks per week and the nitroglycerin consumption did not show a significant difference between the two pacing modes. It is concluded that rate responsive pacing is beneficial and safe in patients with angina pectoris and coronary artery disease.
Temporary Pacing in Complete Heart Block due to Lyme Disease: A Case Report
Authors: LÕRINCZ ISTVÁN , LAKOS ANDRÁS , KOVÁCS PÉTER , VÁRVÖLGYI CSABA , POLGÁR PÉTER , WÓRUM FERENC
Published: July 2006

The authors present the case of a 44‐year‐old man who was admitted with complete heart block and signs of severe bradycardio, After steroid administration and temporary pacemaker treatment the complete heart block resolved. During this therapy transient ST segment and T wave abnormalities occurred. The positive Borrelia burgdorferi antibody titer arrived only after therapy had been completed. This is regarded as the first case of Lyme carditis with complete heart block diagnosed in eastern Europe. Carditis resolved without antibiotic treatment and has not recurred.
Effects of Encainide on the Function of Implanted Pacemakers
Authors: SALEL ANTONE F. , SEAGREN SHIRLEY C. , POOL PETER E.
Published: July 2006

The effect of encainide on chronic pacing thresholds was evaluated in 10 pafients, age 64–89, who were exposed to weekly increased encainide dosing (25 mg TID, 50 mg TID, 75 mg TID). Median pacing threshold (mujoules) increased modestly at each period compared to placebo and returned rapidly to baseline after discontinuation.

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No patient experienced a pacing‐related ciinicai event. One patient had a large threshold increase (566%), but no failure to capture on 24‐hour ECG, and one patient whose threshold increased minimally had clinically insignificant capture failure, the longest event being 3 beats. No other failure to capture was noted. Thus, encainide, like a number of other antiarrhythmic drugs, appears to affect pacing thresholds. At the highest dose of 225 mg/day (75 mg TID, which exceeds the generally recommended dose of 50 mg TID), but not at lower doses, some patients may experience loss of capture that does not appear related to the change in threshold energy required. Increases in the duration of the paced QRS induced by encainide did not predict increases in threshold. Therefore, when higher doses of encainide are required in patients with pacemakers, clinical observation and ambulatory electrocardiographic monitoring should be carried out.
The Effect of Electrode Configuration on the Unipolar His‐Bundle Electrogram
Authors: KADISH ALAN H. , MORADY FRED , ROSENHECK SHIMON , SUMMITT JONI , SCHMALTZ STEVE
Published: July 2006

Although “unipolar electrograms” recorded from the His‐bundle position have been used to help position catheters for His‐bundle ablation, the techniques used to record such electrograms have not been standardized. The effects of five anode locations (right chest wall, anterior chest wall, left chest wall, posterior chest wall, and inferior venu cava) on unipolar atrial, His bundle and ventricular electrograms recorded from the His‐bundle position were examined in ten patients undergoing clinical electrophysiology studies. Electrograms were recorded at filter settings of 50–500 as well as 0.05–1000 Hz. The location of the anode had no consistent effect on the amplitude, duration or morphology of any of the electrograms at either filter setting, but signals recorded with the inferior vena cava anode had the highest signal‐to‐noise ratio. A filter setting of 50–500 Hz decreased the amplitude of atrial (0.72 to 0.33 mV‐P < 0.01), His bundle (0.38 vs 0.32 mV‐P < 0.01) and ventricular electrograms (3.71 vs 2.01 mV‐P < 0.001) compared to a filter setting of 0.05‐1,000 Hz. The filter setting did not affect electrogram duration. We concluded that the use of an electrode catheter in the inferior vena cava as the anode when recording “unipolar electrograms” from the His‐bundle position yields a better signal‐to‐noise ratio than a skin patch on the chest and appears to be the optimal method for recording unipolar electrograms.
Effects of Extracorporeal Shock Wave Lithotripsy on Single Chamber Rate Response and Dual Chamber Pacemakers
Authors: FETTER JOSEPH , PATTERSON DAVID , ARAM GEORGE , HAYES DAVID L.
Published: July 2006

This study evaluated effects of extracorporeal shock wave lithotripsy on four models of Medtronic implantable cardiac pacemakers. In vitro testing consisted of: (1) unsynchronized pacemaker strapped on the patient with extracorporeal shock synchronized to the patient's native heart rate; and (2) pacemakers suspended alone in water 6 inches from the focal point, synchronizing the extracorporeal shock to pacemaker output. Unsynchronized shocks affected each model of pacemaker diferently, i.e., single chamber constant rate pacemakers experienced extended periods of inhibition for more than three pacing cycles while activity‐triggered rate response pacemakers exhibited rate increases to the upper rate setting. Dual chamber synchronous pacemakers exhibited intermittently a 59% decrease and a 20% increase in ventricular rate due to inhibition and triggering, respectively, from shock over‐sensing. Synchronized shocks did not alter the rate of single chamber constant rate pacemakers, but did cause the rate to increase to the upper rate setting for activity‐triggered rate response pacemakers. The shock was synchronized to the initial atrial output from the dual chamber pacemaker and caused frequent inhibition of the ventricular stimulus when the ventricular‐safety‐pace (VSP) feature was programmed off. Programming VSP on reduced the incidence of ventricular inhibition resulting in near normal pacemaker operation. There was neither observable damage to pacemaker components nor spurious reprogramming of pacemaker parameters during the tests. Our studies with one manufacturer's pacemakers suggests that lithotripsy shock effects on implantable pacemakers can be tolerated provided: (1) the single chamber pacemaker is programmed to the demand constant rate modality; (2) the dual chamber pacemaker is programmed to VSP on or to the VVI mode; and (3) the pacemaker distance to the focal point is > 6 inches. ECG monitoring is standard practice during the procedure and should be adhered to as an optional measure to verify normal intrinsic rhythms or pacemaker operation.
DL and D Sotalol Decrease Defibrillation Energy Requirements
Authors: WANG MICHELE , DORIAN PAUL
Published: July 2006

We examined the acute effects of intravenous DL and D sotalol on the energy requirements for internaJ defibrillation (DF) in 44 dogs anesthetized with pentobarbital (n = 18), enflurane (n = B), and fentanyl (n = 18). Multiple shocks of varying energies were applied through left and right ventricular epicardial patch electrodes to relate delivered energy to percent success in DF. The energies required for 50% success in DF (E) were estimated by logistic regression. DL or D sotalol was administered in a loading (4 mg/kg over 10 min) and maintenance (1.5 mg/kg/hr) infusion and the energy—success curve was again measured 30 minutes after drug administralion. The effect of DL and D sotalol on E50 was compared to controls given saline. Both DL and D sotalol significantly lowered E50 by 16%± 14% (P < 0.05) and 24.5%± 8.2% (P < 0.05), respectively, in fentanyl anesthetized animals; this was accompanied by a 22%± 8% (P < 0.05) and 16%± 5% (P < 0.01) increase in ventricular elective refractory period (VERP), respectively. In pentobarbital anesthetized dogs, DL and D sotalol decreased E50 by 16%± 27% (P = ns) and 11%± 16% (P < 0.05), respectively, and were associated with a 23%± 5% (P < 0.01) and 12 ± 4% (P < 0.05) prolongation of VERP. DL and D sotalol decrease defibrillation energy requirements, possibly as a result of their Class III antiarrhythmic drug action.
Incessant Ventricular Tachycardia with a Right Bundle‐Branch Block Pattern and Left Axis Deviation Abolished by Catheter Manipulation
Authors: BLOMSTRÖM‐LUNDQVIST CARINA , BLOMSTRÖM PER , BECKMAN‐SUURKÜLA MARIE
Published: July 2006

A 22‐year‐old man underwent electrophysiological evaluation for incessant wide QRS complex tachycardia with a pattern of right bundle‐branch block and left axis deviation. The right and left ventricles were enlarged and hypokinetic consistent with dilated cardiomyopathy. Ventricular tachycardia was diagnosed by demonstrating capture and fusion beats, atrioventricular dissociation, and His potential activation that began after the onset of each QRS complex. Atrial extrastimuli and rapid atrial pacing failed to terminate the tachycardia and, although ventricular stimulation was successful, the tachycardia spontaneously restarted after one or two sinus beats. The tachycardia was unexpectedly abolished during catheter manipulation in the left ventricle and has not recurred during three‐years of follow‐up. The picture of a cardiomyopathy resolved. The ease with which the tachycardia was abolished by catheter manipulation implicate a therapeutic potential for catheter ablation of this type of tachycardia.
The Effect of Radiofrequency Catheter Ablation on Permanent Pacemakers: An Experimental Study
Authors: CHIN MICHAEL C. , ROSENQVIST MARTEN , LEE MICHAEL A. , GRIFFIN JERRY C. , LANGBERG JONATHAN J.
Published: July 2006

Radiofrequency current is being investigated as an alternative to direct current shock for transcatheter abJation of cardiac arrhythmias. Permanent pacemakers are known to be susceptible to high frequency electromagnetic interference. This study was performed to examine the effects of Imnscatheter radiofrequency ablation on permanent pacemakers in a worst‐case scenario. Nineteen pulse generators representing 16 models from seven manufacturers were acutely implanted in 12 dogs to assess (heir function during and after ablation. Pulse generators were implanted subcutaneously in the neck and connected to a transvenous permanent pacing lead positioned in the right ventricular apex. A 6F quadri‐polar electrode catheter was positioned approximately 1 cm from the tip of the permanent pacing lead. Radiofrequency current from an electrosurgical unit was applied between the distal electrode of the catheter and a large diameter skin electrode placed below the left scapula. Three additional ablation sessions were performed with the catheter situated 4‐5 cm from the permanent pacing lead. Each ablation consisted of 35 W of radiofrequency power, delivered for up to 30 seconds. Twelve pulse generators were falsely inhibited during radiofrequency ablation while programmed to (he WI or DDD mode, nine of which continued to be inhibited while programmed to the VOO or DOO mode. Five pulse generators paced at abnormal rates, including three examples of one pulse generator model that displayed pacemaker runaway. Runaway was observed during eight ablations, resulting in two episodes of ventricular fibrillation. Eleven pulse generators reverted to noise mode behavior during ablation. Only three pulse generators were unaffected during ablation. No reprogramming or pacing system malfunctions were observed after cessation of radiofrequency current application or during ablations > 4 cm from the permanent lead. No changes in lead impedance, sensing, or capture threshold were observed. In conclusion, transcatheter radiofrequency ablation within close proximity of a permanent pacing lead may falsely inhibit implanted pulse generators, induce pacemaker runaway, or cause pulse generators to revert to noise mode behavior. Radiofrequency ablation performed in patients with permanent pacemakers requires careful monitoring as well as backup external pacing. A complete pacing system analysis should be performed following each ablation.
Summation of Excitation with a Single Conditioning Stimulus in the Canine Heart
Authors: SAIHARA SHINICHIRO , INDUE HIROSHI , TODA IKU , USUI MASAHIRO , SUGIMOTO TSUNEAKI
Published: July 2006

A subthreshold stimuJus was reported to become effective in producing a propagated ventricular response when preceded by another subthreshold stimuJus or stimuli, a phenomenon that is known as summation of excitation but has not been studied systematically. Effect on summation of current intensity and coupling interval of a conditioning stimuJus (Sc, protocol #1) and that of stimulation site o/Sc fprotocol #2] were determined in anesthetized, open‐chest dogs. Effective refractory period (ERPJ was determined with an extrastimulus (S2) at a ventricular pacing cycle length (S1S2 of 500 msec. Pulse width of S1, S2 and Sc was 2 msec. For pacing protocol #1 (12 dogs), current intensity of S1 and S2 was equal (twice diastolic threshold, 2, 5, or 15 mA), and that of Sc was equal to or lower than that of S1 S2 interval was fixed 1 msec shorter than ERP, and Sc was delivered 5 msec prior to S2 The S1Sc interval was shortened in 2 msec steps. Summation was present if Sc plus S2 evoked a propagated response. Prevalence of summation increased along with an increase in current intensity of Sc (P < 0.001. For pacing protocol #2 (7 dogs), current intensity of S1 S2, and Sc was equal (twice diastolic threshold, 5 or 10 mA). As the distance between site of Sc and that of S2 increased, prevalence of summation decreased (P < 0.001. Summation did not occur when Sc was delivered at a site only 5 mm away from the site of S2. In conclusion, summation of excitation with a single conditioning stimulus was both time and strength dependent, and limited in development spatially.
Effect of Bipole Configuration on Atrial Electrograms During Atrial Fibrillation
Authors: BAERMAN JEFFREY M. , ROPELLA KRISTINA M. , SAHAKIAN ALAN V. , KIRSH JOEL A. , SWIRYN STEVEN
Published: July 2006

Despite an increasing body of work on the nature of fibrillatory rhythms, and the application of different bipole configurations in antifibrillatory devices, little published work has assessed the effect of bipole configuration on the endocardial recordings of fibrillatory rhythms. To address this issue, a specially designed 6 Fr decapolar catheter was used to record intra‐atrial electrograms during sustained atrial fibrillation in 15 patients. Simultaneous filtered (30–500 Hz) and unfilfered (0,05–5,000 Hz) recordings of atrial fibrillation were performed of four different bipole configurations: (a) 1‐mm interelectrode spacing adjacent to the atrial wall; (b) 10‐mm interelectrode spacing adjacent to the atrial wall; (c) 10‐mm inter‐electrode spacing 24 mm from the distal catheter tip; (d) 1‐mm interelectrode spacing 24 mm from the distal catheter tip. One minute of such data was recorded, and each 4.27‐second segment (X 14 segments) was analyzed for atrial rate, electrogram amplitude, amplitude probability density function (apdf), median frequency in the 2–9 Hz band, and elecfrogram morphology. Changes in bipole configuration resulted in profound changes in calculated afrial rate, amplitude, and apdf (P < 0.001 by two‐way ANOVA in each instance). Specifically, closer interbipole spacing and closer proximity to the atrial wall resulted in lower calculated atrial rates, higher electrogram amplitudes, and higher apdf values. In contrast, median frequency proved to be a more robust measure despite multiple configurations (P> 0.10 by two‐way ANOVA). These changes significantly affected the predictive value of previously published detection criteria for rate (P < 0.01) and apdf (P < 0.000001). Bipole location also affected morphology, with locations adjacent to the atrial wall and with closer interbipole spacing having more discrete electrograms and greater apparent organization (P < 0.0001). Further, when data segments from all patients and bipole configurations were grouped, rate and apdf were found fo be strongly inversely correlated (r = ‐0.808). In conclusion: (1) Bipole configuration has important effects on calculated atrial rate, electrogram amplitude, and apdf during atrial fibrillation; (2) Median frequency and frequency domain analysis may be a more robust way of characterizing atrial fibrillation despite the use of different bipole configurations; (3) Changes in bipole configuration affect the efficacy of detection criteria, and considerations about the level of organization of a cardiac rhythm; (4) Rate and apdf may be largely redundant measures of fibrillatory rhythms; and (5) Traditional estimates of atrial rates up to 700/min during atrial fibrillation, based on the unipolar or widely spaced bipolar leads of the surface electrocardiogram, reflect the effects of their recording methods. and are an overesfimation of the true atrial rate.
Adult Acute Rheumatic Fever: A Rare Case Presenting with Left Bundle Branch Block
Authors: YAHALOM MALKA , JERUSHALMI JACQUELINE , ROGUIN NATHAN
Published: July 2006

In contrast to the more common electrocardiographic patterns seen in acute rheumatic fever, such as first‐degree heart block, the appearance of left bundle branch block is rare. An adult patient with acute rheumatic fever presented with left bundle branch block on admission, subsequently had sudden cardiac arrest. She was resuscitated successfully and required temporary pacing. An echocardiogram and radionuclide ventriculography were compatible with interventricular septal involvement in the rheumatic carditis. After 20 days of steroid therapy, the left bundle branch block pattern of the electrocardiogram disappeared. A possible mechanism for the development of complete heart block in acute rheumatic fever is discussed, It is suggested that patients with acute rheumatic carditis who have electrocardiographic manifestations of prolonged P‐R interval and left bundle branch block should be managed with prophylactic pacing.
Activation Times for “Emergency Back‐Up” Programs
Authors: SWEESY MARK W. , BATEY ROBERT L. , FORNEY RICHARD C.
Published: July 2006

A bench study was performed on 34 different pulse generators to evaluate the time necessary to actuate an “emergency back‐up” (EBU) program. Pacemakers were programmed to Joss of capture before the EBU was activated. Two pauses were measured that included the total pause from captured beat to captured beat and the time from the first pacing artifact showing Joss of capture to the first captured beat resulting from EBU activation. Special features for threshold testing such as temporary pacing, auto threshold, Vario, and an alternating pulse ventricular threshold test were also evaluated. Activation times of the EBU ranged from 1.8 to 11.1 seconds with total pauses of 2.7 to 33.2 seconds, respectively. There were considerable variations in EBU times even within a single manufacturers' pulse generators. The special features for threshold testing resulted in pauses measuring 0.6 to 3.0 seconds with total pauses of 2.2 to 4.0 seconds, respectively, and in all cases were faster than using the EBU. Utilization of the EBU to regain capture during threshold testing in pacemaker dependent patients may result in prolonged pauses and syncope or near syncopal episodes.
Intracardiac Coiling of Permanent Atrial Leads
Authors: LÓPEZ‐GIL MARÍA , GOICOLEA ANTONIO , BARBERO JOSÉ MARÍA , CHICOTE RAMIRO , COSIO FRANCISCO G.
Published: July 2006

We have observed intracardiac movement of permanently implanted atrial pacing leads in two patients with AAI pacemakers. This resulted in looping of the lead body into (he right atrium and ventricle, without displacement of the tip or changes in the pacing or sensing thresholds. At surgery only a single fixation ligature was found and allowed sliding of the lead through the suture sheath, in both cases. The position was corrected by gently pulling the lead. Multiple ligature fixation may avoid this complication.
The Value of Exercise Test, Hotter Monitoring, and Programmed Electrical Stimulation in Detection of Ventricular Arrhythmias in Patients with Hypertrophic Cardiomyopathy
Authors: JANSSON K. , DAHLSTRÖM U. , KARLSSON E. , NYLANDER E. , WALFRIDSSON H. , SONNHAG C.
Published: July 2006

To determine the best way to detect serious ventricular arrhythmia in patients with hypertrophic Cardiomyopathy (HCMJ, 15 patients with HCM performed an exercise test, had Holter monitoring during 24 hours, and programmed electrical stimulation (PES) in a randomized order, and the presence and type of ventricular arrhythmia was noted. During exercise testing, only one patient demonstrated ventricular tachycardia (VT) just prior to the test. By Holter monitoring, four patients had short episodes of asymptomatic VT. PES, using up to three extrastimuli induced VT or ventricular fibrillation (VF) in ten patients including those with VT during exercise testing and Holter monitoring. There were no differences between patients with and without ventricular arrhythmia during PES regarding age, left ventricular outflow obstruction, thickness of interventricular septum, interventricular septum/posterior wall thickness ratio, corrected QT interval, or the amplitude of the R wave in lead aVR in electrocardiography. Our results indicate that inducible VT/VF during PES is a common finding in patients with HCM. Twenty‐four hour Holter monitoring was superior to exercise testing in revealing serious ventricular arrhythmia in those patients.
Importance of Heart Rate Modulation on the Cardiac Hemodynamics During Postexercise Recovery
Authors: LAU CHU‐PAK , WONG CHEUK‐KIT , CHENG CHUN‐HO , LEUNG WING‐HUNG
Published: July 2006

The influence of heart rate changes on the recovery of cardiac hemodynamics and lactate clearance after exercise was studied in nine patients with complete atrioventricular (AV) block treated with programmable pacemakers. A preliminary treadmill exercise test in which the pacing rate was externally increased stepwise from 70 to 230 bpm was performed fo determine the maximum exercise duration. Two exercise tests involving an equal amount of exercise load were performed, the pacing rate was either programmed to the basic rate (abrupt decay) or gradually (modulated decay) immediately after exercise termination. Compared with abrupt decay, modulated decay resulted in a higher mean arterial pressure (100 ± 4 mmHg vs 91 ± 5 mmHg, P ± 0.05) and diastolic pressure (76 ± 4 mmHg vs 59 ± 4 mmHg, P < 0.001) immediately on exercise termination. Immediately after exercise and during modulated decay, cardiac output (represented by Doppler derived minute distance] declined gradually and was determined mainly by a higher pacing rate without significant changes in stroke volume. On the other hand, minute distance fell abruptly during abrupt decay (996 ± 107 m at peak exercise and 561 ± 88 m immediately after a rate change at exercise termination, P < 0.01) with a corresponding abrupt increase in systemic vascular resistance. This was later compensated by a gradual increase in stroke volume during the recovery period. The cumulative cardiac output between the two rate changes equalized at the 4th minute of recovery. Abrupt decay was associated with a higher recovery atrial rate (109 ± 5 bpm versus 102 ± 5 bpm at the fifth minute of recovery, P < 0.01) and a higher peak velocity of ascending aortic flow, both suggestive of an enhanced sympathetic level during this mode of recovery. There is a trend toward a higher peak arterial lactate level during abrupt decay, although the overall lactate clearance rates between the two decay modes were similar. Most patients preferred the modulated decay. In conclusion, rate modulation at exercise termination produced more gradual hemodynamic changes compared with abrupt decay. Cardiac hemodynamics was maintained by a compensatory increase in stroke volume and an increase in sympathetic activities after a latent period. Independent of the form of rate modulation, a fixed amount of cardiac output appears necessary to facilitate postexercise recovery after a given workload.
The Cardiac Electrophysiology of Postresuscitation Hypokalemia in Dogs
Authors: SALERNO DAVID M. , MURAKAMI MARYANN M. , WINSTON MARK , ELSPERGER K. JOSEPH
Published: July 2006

Hypokalemia has been observed in man after out‐of‐hospital ventricular fibrillation and after cardiover‐sion from ventricular tachycardia in the electrophysiology laboratory, and also in dogs following ventricular fibrillation (maximal effect 45–60 minutes after resuscitation). Since the electrophysiological effects of postresuscitation hypokalemia are unknown, we evaluated the effects of this hypokalemia on ventricular fibrillation thresholds (group 1) and on right ventricular effective refractory periods (group 2). In both groups, anesthetized dogs with normal hearts were divided into experimental animals that had 2 minutes of ventricular fibrillation followed by cardioversion without medications and control animals without ventricular fibrillation. In group 1, we measured serum potassium before ventricular fibrillation (or time 0 in control dogs) and then measured potassium and ventricular fibrillation threshold at 45, 60, 75, and 90 minutes after baseline. In group 2 animals we measured right ventricular effective refractory periods and serum potassium at baseline and sequentially from 7 to 180 minutes after resuscitation. In group 1, the maximum change in potassium from baseline was ‐0.8 ± 0.3 mEq/L at 60 minutes after resuscitation as compared to ‐0.1 ± 0.3 mEq/L in control animals at 60 minutes (P < 0.01). At 60 minutes, ventricular fibrillation threshold was 8 ± 3 mA in ventricuJar fibrillation animals and 7 ± 3 mA in control animals (P = NS). In group 2 animals, the maximum change in serum potassium also occurred 60 minutes after resuscitation and was ‐0.8 ± 0.3 mEq/L as compared to ‐0.2 ± 0.2 mEq/L in control animals (P < 0.001). Right ventricular effective refractory periods after an 8‐beat drive at 200 msec were 121 ± 35 msec in the resuscitated animals versus 123 ± 19 msec in control animals 60 minutes after baseline (P = NS). In conclusion, postresuscitation hypokalemia had no effect on the ventricular fibrillation threshold or right ventricular effective refractory period in anesthetized dogs with structurally normal hearts prior to arrest.
The Use of Electrically Stimulated Skeletal Muscle to Pump Blood
Authors: GEDDES L.A. , BADYLAK S.F. , WESSALE J.L , JANAS W. , BOURLAND J.D. , TACKER W.A. , STEVENS L.
Published: July 2006

Electrically stimulated skeletal muscle can be used in many ways to pump blood. The important physiological characteristics of skeletal muscle for use in a cardiac assist role are presented. The force developed by a twitch and tetanic contraction are quantilated and the considerations in the choice of the stimulus applied to the innervating motor nerve are discussed. The importance of stimulus frequency and duration of the stimulus train are presented in terms of the stroke volume produced by skeletal muscle contracting around a pouch. The effect that preload has on pouch stroke volume and muscle blood flow are demonstrated. Finally an example is given in which cardiac output is augmented by an untrained, electrically stimulated, canine rectusabdominis muscle wrapped around a pouch connected between the apex of the left ventricle and the aorta. In this study, the augmentation in cardiac output was measured when the skeletal muscle was contracted after each second, third, and fourth ventricular contraction. The augmentation was 46%± 4, 31%± 7, and 25%± 4, respectively, for the three contraction regimens. Although electrically stimulated skeletal muscle can be used as a power source to assist the failing heart, the optimum application is yet to be discovered. Important considerations in selecting the optimal application are preload, stimulus train duration, train rate, and muscle blood flow.
Emotion Profiles and Quality‐of‐Life of Paced Patients
Authors: ČATIPOVIČ‐VESELICA KATIJA , ŠKRINJARIĆ SANDA , MRDENOVIĆ SLOBODAN , MUJIĆ NIHADA , ČÃIPOVIĆ BRANIMIR , ANDRIĆ MIRTA , VIZNER‐LOVRIĆ IRENA , LAUC ANTE
Published: July 2006

More than any other organ of human anatomy, the heart is symbolically charged with emotions. Introducing a foreign body into the heart, even a pacemaker, would be expected to alter, if not damage the most intimate of personal attributes, an individual's personality. Nevertheless, standard measures of emotions, administered before and after pacemaker implantation, revealed an improvement in psychological well‐being in an unselected sample of 80 patients, aged 36 to 80 years. Furthermore, these results occurred whether or not patients returned to work.