bluuebunny/crossref_metadata_2025 huggingface dataset:
The Porous Titanium Steroid Eluting Electrode: A Double Blind Study Assessing the Stimulation Threshold Effects of Steroid
Authors: MOND HARRY , STOKES KENNETH , HELLAND JOHN , GRIGG LEEANNE , KERTES PAUL , PATE BARRY , HUNT DAVID
Published: July 2006

A transvenous pacing lead with a porous electrode which slowly elutes the steroid, dexamethasone sodium phosphate, has been developed. Previous investigations show low and constant stimulation thresholds persisting over at least the first two years post‐implantation. As it is not known whether this low threshold results from the steroid or electrode configuration, a double blind study was designed to compare the same electrode configuration with and without steroid over a 2‐year follow‐up period. There were ten patients in each group with similar age, sex, indications for pacing and implantation data. Regular measurements of postoperative pulse duration thresholds were performed using a customized VVIM pulse generator programmed to 1.5 V output. For the first two days post‐implantation, there were no statistical differences in the pulse duration thresholds between the two pacing leads. From 2 weeks to 2 years the pulse duration thresholds for the steroid leads remained almost constant, whereas the leads without steroid showed a typical rise. The difference in pulse duration thresholds between the two groups of leads from two weeks onwards confirmed that it was the steroid rather than the electrode configuration which prevented the rise in chronic stimulation threshold.
Cardiac Output Versus Pacing Rate at Rest and with Exercise in Dogs with AV Block
Authors: WESSALE JERRY L. , GEDDES LESLIE A. , FEARNOT NEAL E. , JANAS WOLFGANG , ANN GROTE LEE
Published: July 2006

To achieve maximum benefit from exercise (rate)‐responsive pacing in subjects with sinus node dysfunction and AV block, it is necessary to determine the pacing rate (HR) which produces maximum cardiac output (CO) under specified exercise conditions. However, the CO‐HR relationship for exercise has not been systematically investigated. To permit determination of the optimum HR, CO was measured at rest and with exercise for different pacing rates. Seven dogs with complete AV block and permanently implanted ventricular pacemakers were exercised on a treadmill for 5 min at each of our pacing rates (55, 76. 101, 116/min) and at two constant exercise levels (225 and 560 kg‐m/min). CO was determined by impedance cardiography during the resting state preceding exercise and during a brie/period (10–20 s) immediately after exercise, and was expressed as a percent of the CO determined at rest with HR ‐ 55/min. A three‐phase pattern of CO versus HH appears of exist for exercise as for rest. For exercise, starting from a low HR, CO increases markedly; a “plateau” is reached during which moderate increase in CO is achieved by increasing HR. At very rapid pacing rates, CO may actually decrease with further increase in HR. The results of this study suggest that a subject‐specific optimum HR exists for each constant exercise level. Moreover, the methodology employed in the study is applicable to the identification of optimum HR for any exercise (rate)‐responsive pacemaker.
Evaluation of Patients with Bundle Branch Block and “Unexplained” Syncope: A Study Based on Comprehensive Electrophysiologic Testing and Ajmaline Stress
Authors: KAUL UPENDRA , DEV VISHWA , NARULA JAGAT , MALHOTRA ARUN K. , TALWAR KEWAL K. , BHATIA MADAN L.
Published: July 2006

Thirty‐five patients with bundle branch block (BBB) and unexplained syncope underwent electrophysiologic study (EPS) including programmed ventricular stimulation and ajmaline administration (1 mg/kg, IV) to induce inra‐His block. A prolonged HV interval (>55 ms) was present in 16 of the 35 patients. Ajmaline‐induced HV block occurred in 12 patients (complete HV block in 10, and 2:1 HV block in two). Monomorphic ventricular tachycardia (VTJ was inducible in nine (25.7%) and polymorphic VT in two patients (5.7%). Left ventricular ejection fraction (LVEFJ was less than 40% in five patients (45.5%) with inducible VT. Two patients had an unexpected co‐existence o/inducible HV block and VT. The remaining 14 patients (40%) had no detectable abnormality. The incidence of inducible VT was higher (45% vs 13.3%), and the presence of negative studies was lower (30% vs 53.3%) in patients with structural heart disease (n = 20), when compared to those with no significant heart disease (n = 15) (differences not significant [NS]). During a mean follow‐up period of 16.5 ± 9.2 months, all the patients with inducible HV block have been asymptomatic after having received permanent pacemakers. Patients with inducible monomorphic VT (except one with poor left ventricular function who died suddenly) have also been asymptomatic on antiarrhythmic drugs. Of the remaining patients, seven with normal EPS, two with prolonged HV intervals but no inducible HV block (despite being given permanent pacemakers) and one patient with polymorphic VT on antiarrhythmic drugs continue to have recurrent syncope. Approximately 60% of patients with BBB and unexplained syncope have clinically significant electrophysiologic abnormalities. VT accounts for symptoms in a significant number of patients. Ajmaline stress is a useful adjunct to unmask infra‐His block, and some patients have more than one abnormality. Long‐term management guided by detailed EPS is generally successful in preventing recurrent syncope in patients with inducible arrhythmias such as HV block and monomorphic VT.
Pacemaker Longevity Modelling
Authors: GERRARD DOUGLAS J.
Published: July 2006

A generalized mathematical technique is presented for computing the elapsed time necessary for a lithium iodine powered pacemaker to reach any specified battery voltage or degree of battery discharge within its life span. In particular, (he method yields a direct mathematical expression for the longevity of pacemakers the circuits of which possess linear load lines. Because the current‐voltage relationship, which defines the had line, is affected by programmed output settings, electrode/tissue interface impedance and degree of inhibition, the method enables the direct determination of the effect of these parameters on pacemaker longevity.
Sequential Shocks are Comparable to Single Shocks Employing Two Current Pathways for Internal Defibrillation in Dogs
Authors: WETHERBEE JULE N. , CHAPMAN PETER D. , BACH STANLEY M. , TROUP PAUL J.
Published: July 2006

Sequential pulse defibrillation using two current pathways was compared with single shocks simultaneously utilizing both pathways in 16 dogs to assess the effects of temporal summation. A cardioverter‐defibrillator catheter was positioned via the external jugular vein with the distal 4 cm2 shocking electrode located in the right ventricular apex and the proximal 8 cm2 electrode located in the superior vena cava. Three electrode configurations were tested(1) single pulse, distal electrode (cathode) to proximal electrode and chest wall patch (common anode), (2) sequential 5 ms pulses with 1 ms interpulse delay, distal electrode (cathode] to proximal electrode (anode) followed by distal electrode (cathode) to chest wall patch (anode), and (3] sequential 10 ms pulses with I ms interpulse delay using same current pathways described for configuration 2. The lowest energies resulting in termination of AC induced ventricular fibrillation on four trials were 27.9. 26.6, and 42.3 joules respectively for configurations 1, 2, and 3. The mean energy levels were not significantly different for configurations 1 and 2, both of which were significantly lower than that for configuration 3. The lowest peak voltages terminating ventricular fibrillation on four trials were 595 ± 176, 521 ± 134 and 579 ± 171 volts for configuration 1, 2, and 3. The mean voltage level for configuration 2 was significantly lower than that for configurations 1 and 3, which were not significantly different. The mean calculated impedance for the pathway utilizing the catheter was 74.6 ±13.7 ohms, for the pathway utilizing the distal catheter electrode to the chest wall electrode was 102.9 ± 19.7 ohms, and for simultaneous discharge employing both current pathways was 65.0 ±11.3 ohms. In conclusion, for the lead system tested, sequential pulses were not associated with lower energies than single pulses delivered through the same pathways and therefore, temporal summation is comparable to a single shock for internal defibrillation.
The Use and Interaction of Permanent Pacemakers and the Automatic Implantable Cardioverter Defibrillator
Authors: COHEN ANDREW I. , WISH MARC H. , FLETCHER ROSS D. , MILLER FREDERICK C. , MCCORMICK DANIEL , SHUCK JOHN , SHAPIRA NADIV , DELNECRO ALBERT A.
Published: July 2006

The adverse interactions of permanent pacemakers and automatic implantable cardioverter defibrillators (AICD) were studied in nine patients in whom both devices were implanted. Both unipolar and bipolar pacemakers were evaluated. The permanent pacemakers were also used to do noninvasive electrophysiological studies and to induce ventricular fibrillation. Undersensing of ventricular fibrillation by the permanent pacemakers caused inappropriate pacemaker stimuli, which caused undersensing of ventricular fibrillation by the AICD in three of four patients with unipolar pacemakers. After an AICD discharge, pacemaker noncapture was seen in eight of 22 episodes for an average 4.9 seconds and inability to sense was seen in 11 of 20 episodes for an average 9.0 seconds. Counting of pacemaker stimuli and QRS by the AICD caused inappropriate discharges. Noninvasive electrophysiological testing by the pacemakers correlated with invasive testing. Furthermore, induction of ventricular fibrillation was successful in four of five patients attempted, though requiring long bursts at high outputs at the shortest cycle lengths obtainable by these pacemakers. Operation of the AICD and permanent pacemakers must be clearly understood to avoid adverse interactions of these devices.
Surgical Therapy for Sinoatrial Reentrant Tachycardia
Authors: KERR CHARLES R. , KLEIN GEORGE G. , GUIRAUDON GERARD M. , WEBB JOHN G.
Published: July 2006

Sinoatrial reentry is an uncommon cause of paroxysmal supraventricular tachycardia. This paper presents a case of supra ventricular tachycardia, refractory to medical therapy, in which the sinus node formed part or all of the reentrant circuit. The mechanism of the arrhythmia was confirmed by catheter mapping during electrophysiological study and by intraoperative epicardial mapping. Cryosurgical ablation of the right atrium in the region of the sinus node has led to cure of her arrhythmia and emergence of a stable ectopic atrial pacemaker rhythm.
DDD Pacing: An Effective Treatment Modality for Recurrent Atrial Arrhythmias
Authors: ATTUEL P. , PELLERIN D. , MUGICA J. , COUMEL PH.
Published: July 2006

We performed atrial EP studies (atrial substrate evaluation) on 10 patients. These patients had evidence of paroxysmal, sustained, recurrent atrial arrhythmias (7 men and 3 women with a mean age of 64 ± 15 years). All patients combined a brady‐tachy syndrome; 7 patients had a sick sinus syndrome (SSS) and 3 patients a typical vagally induced atrial arrhythmia. No anti‐arrhythmic drug was allowed in 3 patients with SSS, 1 drug failed in 4 patients and the combination of 2 drugs failed in 3 patients during the first to eighth years prior to pacemaker implantation. Atrial substrate evaluation was feasible in all these patients off anti‐arrhythmic therapy and showed important abnormalities of atrial loco‐regional conduction parameters and long refractory periods (RP). The remarkable point was, in 7 patients, a paradoxical improvement in intra‐atrial conduction delay at rapid pacing rate. The DDD pacing mode was chosen in all patients. No technical problem occurred during implantation. Atrial pacing rate was programmed to be slightly higher than the mean diurnal heart rate calculated on Holter monitoring. After implantation, the mean follow‐up period was 18 ± 25 months with an average of one Holter every 4 months during the first 2 years. The 7 patients who improved intra‐atrial conduction at rapid pacing rate were controlled without drugs, 2 patients were controlled with 1 drug, and 1 patient with 2 drugs. Atrial pacing in the DDD mode in a selected group of patients prevents paroxysmal and drug‐resistant atrial arrhythmias. Atrial substrate evaluation is a sensitive tool for assuring the long‐term benefit of atrial pacing. In this subset of patients, maintenance of AV synchrony by DDD pacing is preferable to catheter ablation of the His bundle.
Atrial Fibrillation and Embolic Complications in Paced Patients
Authors: LANGENFELD HEINER , GRIMM WOLFRAM , MAISCH BERNHARD , KOCHSIEK KURT
Published: July 2006

Atrial fibrillation (AF) and thromboembolism are discussed to he complications of the WI mode. We reinvestigated the spontaneous ECG and the anamnesis of 246 pacemaker patients with the indications second and third degree atrioventricular block (AV block, n = III), sick sinus syndrome (SSS, n ‐ 101) and other indications (n = 34), all had shown sinus rhythm at implantation. The mean implantation time was 63 ± 45 months (203 VVI and 43 dual chamber pacemkers). The results: (1) Atrial fibrillation was found in 63 patients (26%). Only one of them had a DDD pacemaker inserted, the implantation time of dual chamber devices being shorter, however, (2) The incidence of AF in patients with SSS (37%) was significantly higher (P < 0.01) than in patients with AV block (19%). (3) Three patients suffered from strokes or transitory ischemic attacks in the follow‐up, only one of them had AF at control. Conclusions: Our results confirm that VVI stimulation favors AF long‐term which is most likely due to irritation of the atrial rhythm by retrograde conduction. In our patients the incidence of thromboembolic complications was not higher in the group of patients with AF. However, from this study in surviving patients, we cannot exclude that we Jost some patients due to severe stroke.
Atrial Electrogram Analysis: Antegrade Versus Retrograde
Authors: MCALISTER HUGH F. , KLEMENTOWICZ PETER T. , CALDERON EVELIO M. , BENEDEK Z. MICHAEL , FURMAN SEYMOUR
Published: July 2006

Automatic discrimination between antegrade and retrograde atrial electrograms would prevent endless loop tachycardia and contribute to tachycardia detection algorithms. We tested its feasibility by comparing antegrade and retrograde atrial electrograms in 129 patients at the time of atrial lead implantation. Only unipolar, passive‐fixation, endocardial, right atrial appendage leads were included. The mean antegrade amplitude was 4.2 ± 2.2 mV, and retrograde 2.4 ± 1.5 mV (P < 0.001); the mean antegrade slew rate was 2.6 ± 2.1 mV/ms, and retrograde 1.3 ± 1.1 mV/ms (P < 0.001). Morphology was similar in 84 patients (65%). The antegrade amplitude exceeded the retrograde by 1.0 mV in 67%, and by 0.5 mV in 81% of patients. Morphology and slew rate contributed little to the discriminating power of amplitude alone. Thus, amplitude criteria reliably distinguish antegrade from retrograde atrial activity.
Analysis Accuracy and Susceptibility to Faults of Holter Functions in Diagnostic Pacemakers
Authors: STANGL K. , WIRTZEELD A. , SICHART U. , BLÖMER H.
Published: July 2006

The analysis accuracy and susceptibility to faults of the additional diagnostic functions were tested in 16 patients (eight men, eight woman, average age 61.5 ± 10.8 years, 14 VVI, 2 AAI) with diagnostic pacemakers (Quintech DPG 921). The average observation period was 19.7 months. With 109 follow‐up intervals of an average duration of 87 ± 39 days, this meant an observation period of 25.9 patient years. A stage‐by‐stage test structure over several intervals of time was applied in order to validate the data acquired through pacemaker Holier functions by means of control ECGs and mathematical test methods. The only fault to occur in the diagnostic functions was a loss of stored data. This was observed in 10% of the follow‐up intervals and was on the average 28% (16%‐38%) of the total events. Forty‐four percent (7/16) of the pacemakers were affected by this malfunction. Our results show that the diagnostic data are certainly correctly acquired. The clinical value of the diagnostic functions is clearly reduced by this potential loss of data.
Clinical Experience with the Rate Responsive Pacemaker Sensolog® 703
Authors: KUBISCH KATHRIN , PETERS WERNER , CHILADAKIS IONANIS , GREVE HANS , HEUER HUBERTUS
Published: July 2006

Pacemaker therapy with rate responsive systems becomes increasingly more important. Numerous clinical and experimental trials have been conducted thus far to investigate different sensors of metabolic demands of the body, functioning independently of an atrial electrogram. To transform mechanical energy into electrical energy, activity‐triggered systems utilize a piezo‐quartz as their sensor. Thirty jive patients suffering from pathological bradyarrhythmias and therefore from an inadequate increase of the heart rate during exercise were supplied with a Sensolog® 703. Clinical follow‐up was first performed with the help of treadmill ergometry, later on by walking on flat ground and climbing steps. The settings due to the first test caused inadequately high stimulation rates. A 24‐h‐Hoher‐ECG was necessary to control the programming and the rate profile in the patient's daily life. Using only the histogram and the rateread function, all rate adaptive parameters of the Sensolog® 703 could be set by walking on flat ground and climbing steps. We defined a frequency of 75–85 min−1 to be appropriate during walking, respectively “low work.” Individual programming ranged from 2–5/8–15/high‐low/very fast‐medium/fast‐medium (slope, threshold, gain, reaction and recovery time). Reprogramming based on 24‐h‐Holter ECG was only necessary if the pacemaker was formerly adjusted with the help of treadmill ergometry. Besides, we observed an increase of the stimulation rate due to vibrations not related to exercise, e.g., by driving in a car.
Respiratory‐Dependent Atrial Pacing, Management of Sinus Node Disease
Authors: ROGNONI G. , BOLOGNESE L. , AINA F. , OCGHETTA E. , MAGNANI A. , ROSSI P.
Published: July 2006

The effectiveness of respiratory‐dependent atrial pacing (AAI‐RD) was assessed in 23 patients (11 male, 12 female; 68 ± 10 years) with symptomatic isolated sinus node disease (SND). Follow‐up was performed at 3 month intervals and included history taking, physical examination, ECG recording and 24‐hour Holter monitoring. An incremental treadmill exercise test was performed in 21/23 patients before pacemaker implantation, in 23/23 patients after implantation (at least two tests with different programmed settings of respiratory rate/paced rate ratio); 21/23 patients underwent treadmill tests during both fixed rate 70 bpm and AAI‐RD pacing. Physiological sensitivity of AAI‐RD pacing was found excellent in 34 tests (85%) and fair in six (15%). Spontaneous heart rate was significantly higher after pacemaker implantation fbpm 115 ± 20 vs 98 ± 24, P < 0.001). In 10/21 patients paced rate was significantly higher during AAI‐RD vs AAI pacing (131 ±9 vs 106 ± 16, P < 0.001) with better total work time (min 9.9 ± 4 AAI‐RD vs 6.8 ± 2.6 AAI, P < 0.002), higher oxygen consumption at anaerobic threshold (ml/min 1137 ± 406 AAI‐RD vs 882 ± 268 AAI‐RD vs 5.5 ± 2.6 AAI, P ‐ 0.001). No significant difference was found in 7/21 patients (overlap between spontaneous and paced rate during both AAI‐RD and AAI programming); 4/21 patients did not reach anaerobic threshold owing to osteomuscular limitations. AV block was detected in 1/23 patients, Biorate circuital failure in 1/23, sporadic undersensing in 5/23, short and symptom‐free myopotential inhibitions in 10/23. We concluded that AAI‐RD pacing is a reliable, safe and useful modality in pacemaker management of isolated SNA, especially in patients with abnormal rate response to exercise.
Is DDD Superior to VVI Pacing in Mixed Carotid Sinus Syndrome? An Acute and Medium‐Term Study
Authors: BRIGNOLE MICHELE , SARTORE BRUNO , BARRA MAURO , MENOZZI CARLO , LOLLI GINO
Published: July 2006

The aim of this study was to evaluate fhe importance of atrial synchronism for pacing therapy of patients with mixed carotid sinus syndrome. In 23 patients (21 m, two f: mean age 69 ± 8 years) affected by symptomatic mixed carotid sinus syndrome we performed: (1) Research of ventriculo‐atrial conduction, orthostatic hypotension and pacemaker effect; and [2] Carotid sinus massage in the standing position during VVI and DVI temporary pacing.

Next, ail patients received a permanent DDD pacemaker and entered a 2 month two period single‐blind, randomized, cross‐over study on DVI/DDD versus VVI mode. During the DVI/DDD period, no syncope occurred in any patients, minor symptoms persisted in 11 (48%) of them; during VVI period syncopes recurred in three patients, symptoms requiring the withdrawal of VVI pacing and premature DVI/DDD reprogramming in eight patients, minor symptoms in 17 (74%). A comparison between 14 patients, who preferred DVI/DDD period (Group A), and the remaining nine patients who noted no preference between DVI/DDD and VVI period (Group B) was performed on the basis of the preimplant evaluation. Group A patients had a greater pacemaker effect (‐34 ± 16 mmHg vs ‐16 ± 14 mmHg) and a higher prevalence of symptomatic pacemaker effect (50% vs 0%), of ventriculo‐atrial conduction (78% vs 44%) and of orthostatic hypotension (50% vs 11%), while the entity of the systolic pressure fall caused by carotid sinus massage was similar in the two groups either during VVI mode (Group A‐51 ± 16 mmHg vs Group B‐56 ± 27 mmHg) or DVI mode (Group A‐38 ± 17 mmHg vs Group 3–45 ± 17 mmHg).

Thus, we conclude that vasodepressor reflex of carotid sinus syndrome is not prevented by DVI/DDD pacing even if the loss of atrial synchronism resulting from WI pacing, by adding an important pacemaker effect, causes a more severe hemodynamic consequence.

DVI/DDD pacing is more effective than VVI in 61% of patients. When pacemaker effect, ventriculoatrial conduction and orthostatic hypotension are present, VVI failure is possible, therefore DVI/DDD stimulation is indicated; on the contrary the evaluation of the vasodepressor reflex during WJ or DVI temporary pacing is of little value in the choice of the mode of pacing.
DDD Pacemakers Maximize Hemodynamic Benefits and Minimize Complications for Most Patients
Authors: BYRD CHARLES L. , SCHWARTZ SUSAN J. , GONZALES MICHELE , BYRD CHARLES B. , CIRALDO ROBERT J. , SIVINA MANUEL , YAHR WILLIAM Z. , GREENBERG JACK J.
Published: July 2006

A 44‐month retrospective analysis was performed on 666 pacemakers implanted at Mt. Sinai Medical Center. Mapping techniques and endocardial waveform analyses were used during lead positioning to ensure the best electrical environment. The optimal pacing lead type was selected based on the clinical situation. Follow‐up evaluations were rigorous. Patient population ranged in age from 28 to 103 with a mean of 78 years at time of implant. Seventy percent of the patients received DDD pacemakers with an 81% survival incidence at 44 months, of the WI population (30% of the implants), there was a 62% survival incidence. Most problems associated with the pacing systems were related to the atrial channel. Loss of atrial sensing occurred in 7.5% of the population and was corrected noninvasively in 5.8%. Due to chronic loss of atrial sensing, 1.7% of the population remained programmed to DVI/VVI. A total of 7.7% were chronically reprogrammed from DDD to WI, 5.6% secondary to atrial fibrillation. Reoperations were necessary in 1.2% of the malfunctioning systems that could not be corrected by reprogramming. The following conclusions were reached: (1) maximizing hemodynamic benefits and minimizing pacemaker complications permitted a survival rate equal to or better than that of the general population, and (2) chronic problems related to the atrial lead and malfunctions of the pacing system were minimized by careful patient selection, appropriate pacemaker and lead selection, endocardial waveform analysis, and thorough follow‐up.
AICD Indications (Patient Selection): Past, Present and Future
Authors: MOWER MORTON M. , NISAM SEAH
Published: July 2006

During the course of a seven year implant experience with the Automatic Implantable Cardioverter‐Defibrillalor (AfCD) now extending to well over 3,700 implantees, several functional advances have been made in the pulse generators, and criteria for implantation were successively broadened. Survival statistics have been excellent with 1‐year arrhythmic survival over 98%, and total survival from all causes of death in excess of 60% at 5 years. Still, only relatively few of the patients who could possibly be helped by this device actually receive one. Reasons for this are probably complex but include, among other things, the relative newness of electrophysiology as a subspecialty, and a lack of appreciation by the general medical public in regard to this particular treatment modality. Small increases in referral patterns thus can have the potential to produce marked increases in the utilization of AICDs. Additionally, other high risk populations appear to be ready for inclusion into AICD therapeutic trials, and techniques also appear at hand to examine presumably healthy populations so as to predict those subject to suffer eventual sudden cardiac arrest. Under such circumstances, the ultimate impact of AICD therapy can hardly be imagined.
Pacing in a Patient with Ebstein's Anomaly
Authors: ANDERSEN CLAUS , OXHØJ HENRIK , JUSTESEN PER
Published: July 2006

ANDERSEN, C, et al.: Pacing in a Patient with Ebstein's Anomaly We report a case of Ebstein's anomaly in which ventricular pacing was achieved by positioning a pacing lead in the enlarged right atrium. By placing the electrode in the atrialization of the right ventricle, an aggravation of tricuspid regurgitation that may result from catheter displacement of the valve leaflets is avoided.
Changes in Morphology of the Paced QRS Complex Related to Pacemaker Output
Authors: VAN GELDER L.M. , EL GAMAL M.I.H. , TIELEN G.H.J.
Published: July 2006

VAN GELDER, L.M., et al.: Changes in Morphology of the Paced QRS Complex Related to Pacemaker Output The influence of pacemaker output on the morphology of the paced QRS complex was studied from standard lead electrocardiograms in 69 patients with bipolar pacemakers. In 40 of the 69 patients (58%), there was a significant (P < 0.001) change in electrical axis, from –75° at the low output setting (2.7 V, 0.15 msec) to –67° at the high output setting (8.1 V, 2.29 msec). In 30 patients, these changes were also associated with changes in the QRS morphology and in the T‐wave. This phenomenon may be explained by additional stimulation from the proximal electrode at high output, thus altering the pattern of depolarization.
The Tall R Wave in Lead V1 in Posterior Myocardial Infarction: A Reciprocal Sign or a His‐Purkinje Conduction Disturbance?
Authors: BREMBILLA‐PERROT BEATRICE , DE LA CHAISE ARNAUD TERRIER , ISAAZ KARL , PERNOT CLAUDE
Published: July 2006

BREMBILLA‐PERROT. B., et al.: The Tall R Wave in Lead V1 in Posterior Myocardial Infarction: A Reciprocal Sign or His‐Purkinje Conduction Disturbance? The significance of the tall R wave in lead V1 with an R/S ratio 1 in posterior myocardial infarction (PMI) was investigated in 28 patients during programmed electrical stimulation. The patients had been admitted with acute PMI documented by electrocardiogram and proven by enzymatic increase. Electrophysiological study was performed 3 weeks after acute PMI. In 17 of the 28 patients (group 1), the tall R wave in V1 disappeared during stimulation: In 13 of them a premature atrial extrastimulus was responsible for an abrupt normalization of QRS complex in V1 related to an increase in AH or HV interval. In the 4 remaining patients the disappearance of the tall R wave in V1 was related to a sinus pause. In 14 patients of group 1, a different prematurity in atrial stimulation induced a right11 or left3 bundle branch block (BBB). In 11 of the 28 patients (group 2) the tall R wave in V1 was unchanged but a premature atrial extrastimulus induced a right BBB in 5 patients and a left BBB in 6. In conclusion, the normalization of QRS complex in lead V1 during atrial stimulation or alterations in cycle length suggests that the tall R wave in V1 in PMI is not a simple reciprocal sign of leads V8 V9. Its association with different varieties of BBB and changes in AU or HV intervals could suggest a relationship with a His‐Purkinje conduction disturbance in some patients.
Evaluation of the Temperature Response to Exercise Testing in Patients with Single Chamher, Rate Adaptive Pacemakers: A Multicenter Study
Authors: FEARNOT NEAL E. , SMITH HEIDI J. , SELLERS DUNCAN , BOAL BERNARD
Published: July 2006

FEARNOT, N.E., et al.: Evaluation of the Temperature Response to Exercise Testing in Patients with Single Chamber, Rate Adaptive Pacemakers: A Multicenter Study Temperature responsive pacemakers were implanted in 45 patients (ages 44 to 90); 31 patients were evaluated by randomized, paired treadmill exercise tests 1 month postimplant. Of 28 males and 17 females, 19 had coronary artery disease; 8 had congestive heart failure. Pacing indications included sinus node disease (26), atrial fibrillation (15), AV block (10), and brady/tachy syndrome (10); some had multiple indications. Blood temperature (every 10 seconds, resolution = 0.004°C) and pacing rate (every minute) were telemetered from the pacemaker. Average heart rate, exercise duration (5.7 min VVI; 6.7 min VVIR), WIR response time (22 sec), initial temperature drop (0.23°C) and maximum rate of drop (0.65°C/min), temperature rise (0.31°C VVI; 0.38°C VVIR) and rate of rise (0.27°C/min) were studied in a subset of patients. In pacer‐dependent patients, average paired increases in exercise duration and heart rate were 56% and 34%, respectively. Including all (31) patients, some with intermittent sinus rhythm, increases were 28% and 9%, respectively. Because exercise duration increased, temperature rise was higher with rate adaptation. Rate adaptation was obtainable in all patients and patients averaged 99 ± 48 increases above basic pacing rate per day at nominal temperature sensitivity. Conclusion: Beneficial rate adaptation is achievable using blood temperature to modify rate in a sensor based system.
Survival Rates after Pacemaker Implantation: A Study of Patients Paced for Sick Sinus Syndrome and Atrioventricuiar Block
Authors: ZANINI ROBERTO , FACCHINETTI ADELE , GALLO GIOVANNI , BENEDINI GIUSEPPE , METRA MARCO , ASSANELLI DEODATO , GICOGNA RAOUL
Published: July 2006

It is still a matter of controversy as to whether the patients paced for atrioventricular block (AVB) have different prognosis and survival rates than those paced for Sick Sinus Syndrome (SSS). We have compared the survival rates of 962 AVB patients (group A) with that of 283 SSS patients (group B) who underwent pacemaker implantation during the period January 1968 to December 1986. The survival rate graphs of the examined groups were calculated using the actuarial method and the differences in the survival rates between the groups were evaluated using the Logrank test. Our results show that SSS patients have a higher survival rate than AV block with a difference on the rate of survival between the two groups reaching the borderline of statistical significance. Multivariate discriminant analysis was then used to assess that of the parameters (i.e., age at the time of implantation, sex, electrophysiological indication to pacing, etiology or pacing mode) could have had the main influence upon mortality and the different pattern of the survival rate graph within the two groups of patients. Our data show that survival is mostly related to age, pacing mode and, although more slightly, to underlying heart disease; the electrophysiological indication to pacing, instead, does not significantly influence it.
Histopathologic Changes in the Heart Including the Conduction System after Catheter Ablation
Authors: BHARATI SAROJA , LEV MAURICE
Published: July 2006

The pathology of the heart, including that of the conduction system, after various catheter techniques used to ablate the various parts of the conduction system and the myocardium, were examined histologically by serial sections. The experiments were conducted on canines. The conduction system studies included the approaches to the AV node, the AV node, the AV bundle and bundle branches, as well as, the central fibrous body, the tricuspid, mitral and aortic valves. The methods of ablation were DC shock, laser and radio frequency energy. Production of the complete AV block clinically was associated with fibrosis with or without cartilage formation of the approaches to the AV node, the AV node, the bundle and the beginning of the bundle branches in most cases. On the other hand, creation of first degree AV block was associated with fibrotic changes in the approaches to the AV node and the AV node, and second degree block with more changes to the AV node. Coronary sinus ablation resulted in necrosis and fibrosis of the coronary sinus wall with occasional thrombosis of the coronary sinus. The adjacent atrial and/ or the ventricular myocardium also showed fibrosis. Likewise, ventricular septal ablation was associated with focal areas of fibrosis of the myocardium. The conduction system was intact in both of the above experiments. In one human where complete AV block was created to manage intractable atrial fibrillation, the AV node, the bundle, and the bundle branches were fibrosed. In addition, there was a fibrosed atrio‐Hisian connection and the patient died suddenly six weeks after the ablative procedure. The surrounding structures close to the vicinity of the conduction system, such as the aortic, tricuspid, mitral valve, the central fibrous body, and the summit ventricular septum are involved to a varing degree. In summary, (1) Whatever the method of ablation may be, the end result was fibrosis with or without cartilage formation of the ablative area. (2) Congenital anomalies of the conduction system such as an atrio‐Hisian connection may remain elusive for ablative methods, and arrhythmias may presist and may cause sudden death in some cases.
A Clinical Study of the Application of Endocardial Fulguration in the Treatment of Recurrent Atrial Flutter
Authors: CHAUVIN M. , BRECHENMACHER C.
Published: July 2006

Endocardial catheter fulguration has been recently proposed for treatment of arrhythmias originating within the right atrium. In this study the authors attempted to use this technique in eight patients with paroxysmal common atrial gutter. Numerous antiarrhythmic agents failed to prevent recurrences of the episodes, which occurred frequently over periods of at least 4 months. In every procedure, we used a 7F quadripolar catheter electrode introduced via the subclavian vein into the lower part of the right atrium. The two distal electrodes allowed the recording of bipolar double potentials where the critical slow pathway of the reentrant circuit was localized. A unipolar electrogram recording by the tip electrode gave us the location of the area to be ablated when this electrogram was in complete concordance with a small step in the descending part of the F waves in II, III and aVF. This step corresponded to the very depolarization of the reentry area. A DC shock of 100 to 120 J was delivered between the tip electrode and a paddle applied to the left chest wall. Sinus rhythm resumed instantaneously. No mechanical or electrical complications were noted. Three patients are free of relapses without antiarrhythmic drugs (follow‐up: 14 to 17 months); three others are also free of relapses, but antiarrhythmic agents were required for treatment of other supraventricular dysrhythmias (follow‐up: 3 to 17 months); atrial flutter recurred within several days and persisted in spite of two more procedures in two patients. We conclude that endocardial catheter fulguration of paroxysmal and recurrent atrial flutter seems to be effective therapy. Nevertheless, more experience is required in order to confirm these results.
Effects of Time to Defibrillation and Subthreshold Preshocks on Defibrillation Success in Pigs
Authors: FUJIMURA OSAMU , JONES DOUGLAS L. , KLEIN GEORGE J.
Published: July 2006

The purpose of this study was to examine the effects of: (1) time to defibrillation and (2) subthreshold preshocks on defibrillation success. We conducted two separate experiments in 19 anaesthetized, open‐chested pigs. Defibrillation was attempted using the sequential pulse technique approximately 10 s after electrically induced ventricular fibrillation. Each sequential pulse shock consisted of two trapezoidal puises (approximately 3 ms duration), separated by 0.2 ms. Current was delivered to three mesh electrodes (TX‐7, Medtronic) sutured over the anterior right ventricle, posterior right ventricle, and lateral left ventricle. For each animal, defibrillation threshold (DFT) defined as the lowest delivered energy that defibrillated the heart, was measured twice and the average was designated as mean DFT. The energy at 1.4 times the specific mean DFT for each pig was designated as the test shock and 100 volts less than the mean DFT was designated as the preshock.

In the first experiment, test shocks were delivered at five different fibrillation intervals (10, 20, 40. 60, and 90 s). Time to test shock delivery was randomized for 10 to 60s, but, 90 s was always tested at the end of the study. Percentages of success at 10, 20, 40, 60, and 90 s were 94, 78, 94, 83, and 100%, respectively (p = NS). The 12 pigs in which all initial test shocks were successful were selected for the evaluation of post defibrillation arrhythmias. The cumulative incidence of complete heart block lasting at least 5 s were 8, 33, 83, 83, and 83%, respectively. The incidence of complete heart block increased significantly at 40 s (p < 0.001). Ventricular arrhythmias were observed on six occasions at 40 s or later.

Following experiment 1, the pigs were allocated to three groups (n = 6 for each group). Group 1 received one preshock, Group 2, two preshocks and Group 3, three preshocks. Each pig had 16 test shocks, eight with no preshock and eight with one of single, double or triple preshocks within 15 s after ventricular fibrillation onset. The test shock was delivered at 20 s. There were no intra‐ or intergroup differences in percentage of success regardless of number of subthreshold preshocks.

We conclude that delay of defibrillation therapy up to 90 s and delivery of preshocks have no significant effect on the ability to defibrillate the heart in this model. However, delay to 40 s and longer is associated with a higher incidence of complete heart block and ventricular arrhythmias.
The Superfast Atrial Recharge Pulse: A Cause of Pectoral Muscle Stimulation in Patients Equipped with a Unipolar DDD Pacemaker
Authors: STROOBANDT ROLAND , WILLEMS ROGER , DEPUYDT PAUL , HOLVOET GERMAIN , SINNAEVE ALFONS
Published: July 2006

Pectoral muscle stimulation may cause serious discomfort to patients equipped with a pulse generator. Insulation defects of the lead, connector problems and defective coating of the pacemaker can are common causes of local muscle contractions. This report describes pectoral muscle stimulation caused by the atrial superfast recharge pulse incorporated into the atrial channel of a commercially available unipolar DDD pacemaker. As pectoral muscle stimulation could not be eliminated by reprogramming the pacemaker to a lower atrial output in some patients a redesign of the pacemaker is highly required.
Hereditary Long QT Syndrome Associated with Cardiac Conduction System Disease
Authors: GREENSPON ARNOLD J. , KIDWELL GREGORY A. , BARRASSE LINDA D. , HESSEN SCOTT E. , GIUDICI MICHAEL
Published: July 2006

This report describes the cardiac conduction abnormalities, detected by invasive electrophysiological study, in two identical siblings with symptomatic congenital long QT syndrome. Both patients had evidence of intra‐Hisian conduction delay in response to programmed atrial stimulation and pacing induced infranodal block was seen in one of the two patients. The response of the observed conduction delay to autonomic interventions is described. The observed electrophysiologic abnormalities are consistent with previously reported pathological findings and document the association of functional conduction system disease with congenital QT prolongation.
A Case of Cross Stimulation
Authors: DOI YOSHITAKA , TAKADA KAZUYUKI , NAKAGAKI OSAMU , YOSHIMURA KOUSEI , OGAWA SHIGERU , HIROKI TADAYUKI , ARAKAWA KIKUO
Published: July 2006

Cross stimulation in a dual chamber pacing system, in which the atrial stimulus intermittently captured the right ventricle, occurred immediately after pacemaker implantation in a 71‐year‐old man. It was prevented temporarily by reducing the pacing rate so that P wave synchronous ventricular (VDD) pacing resulted and by reducing the output of the atrial circuit from 5 to 4 volts. Cross stimulation disappeared spontaneously 14 days after surgery.
Spinal Cord Electrical Stimulation in Severe Angina Pectoris: Surgical Technique, Intraoperative Physiology, Complications, and Side Effects
Authors: AUGUSTINSSON L.E.
Published: July 2006

Twenty patients with angina pectoris were treated with spinal cord stimulation (SCS) at the T1, T2 level of the spinal cord since June 1985. These patients were not candidates for angioplasty or coronary bypass or those procedures had failed. There were no injections. One lead broke and one lead migrated. Both were corrected migrally and regained some relief. The relief of pain with SCS may be an alternative treatment to coronary bypass or angioplasty in some patients.
Sensor‐Driven Rate Smoothing in a DDDR Pacemaker
Authors: HIGANO STUART T. , HAYES DAVID L. , EISINGER GEORGE
Published: July 2006

DDD pacemakers may have large cycle‐to‐cycle variations in rate at the upper rate limit because of 2:1 block or Wenckebach‐type block. Rate smoothing was introduced as an option to eliminate these large variations. Now, DDDR pacemakers can produce similar electrocardiographic displays through a different mechanism that uses an activity sensor. This is termed “sensor‐driven rate smoothing” because it occurs only when the activity sensor is driving the pacemaker. In the case described, as the atrial rate exceeded the maximum tracking rate and reverted to Wenckebach‐type block, fhe RR interval varied onJy from 600 msec to 680 msec (13.3% rate‐smoothing value) because of sensor‐driven pacing. Maximal sensor‐driven rate smoothing requires optimal programming of the rate response indicators. This sensor‐driven rate‐smoothing effect is an electrocardiographic manifestation that will undoubtedly be seen more frequently as DDDR devices come into widespread clinical use.
Diagnostic Value of Comparison of Ventriculoatrial Interval During Junctional Tachycardia and Right Ventricular Apical Pacing
Authors: CROZIER IAN , WAFA SAMIR , WARD DAVID , CAMM JOHN
Published: July 2006

We postulated that comparison of ventriculoatrial intervals during junctional tachycardia and during right ventricular apical pacing may provide similar diagnostic information to that obtained from the insertion of ventricular extrasystoles during tachycardia. We studied 39 patients with either atrioventricular reentrant tachycardia (AVRT) (23 patients) using a single atrioventricular accessory pathway or atrioventricular nodal reentrant tachycardia (AVNRT) (16 patients). Ventriculoatrial [VA] intervals were measured during tachycardia, during right ventricular apical pacing at the same rate as that of the tachycardia and following a ventricular extrasystole delivered at the minimum reset interval (minimum prematurity of a ventricular extrasystole required to advance the subsequent atrial complex by more than 10 msec). The difference between the minimum VA interval during tachycardia and during ventricular pacing was closely related to both the minimum reset interval (r = 0.92, P < 0.001) and the difference between the minimum VA interval during tachycardia and following a ventricular extrasystole delivered at the minimum reset interval (r = 0.97, P < 0.001) in the 23 patients in whom the minimum reset interval could be determined. The ratio between the minimum Ventriculoatrial interval during tachycardia and ventricular pacing could be determined in all cases and was between 1.53 and 1.68 in AVRT with right free wall (two patients), 0.94 and 1.29 with anteroseptal (three patients), 0.91 and 1.08 with posteroseptal (five patients) and 0.48 and 0.71 with left free wall (13 patients) pathways, while it was between 0.32 and 0.27 in AVNRT (16 patients). The ratio was more discriminative when corrected for ventricular latency and was also useful when calculated from the high right atrial electrogram. We concluded that comparison of Ventriculoatrial intervals during junctional tachycardia and during right ventricular apical pacing can discriminate between the mechanisms of tachycardia and the site of pathway. It provides similar information to that obtained from ventricular extrasystoles during tachycardia with the advantage that it can be determined in all cases.
Tissue Heating During Radiofrequency Catheter Ablation: A Thermodynamic Model and Observations in Isolated Perfused and Superfused Canine Right Ventricular Free Wall
Authors: HAINES DAVID E. , WATSON DENNY D.
Published: July 2006

Thecharacteristics of radiofrequency catheter ablation induced injury in the heart are not well characterized. Since the mechanism of injury by radiofrequency energy is thermal, this study was performed to determine the temperature gradient in myocardial tissue during radiofrequency (RF) catheter ablation, and to validate a thermodynamic model derived to describe these observations. Lesions were created by RF heating in an experimental model of isolated perfused and superfused canine right ventricular (RV) free wall. RF power output was adjusted to maintain electrode tip temperature at 80°C for 120 seconds in 153 serial lesions and radial temperature gradients were measured. With increasing distance from the electrode, the temperature of the myocardium decreased in a hyperbolic form that was closely predicted by a derived thermodynamic model (P = 0.0001, r = 0.98). This gradient and resultant lesion sizes were unafected by the rate of coronary perfusion. The utility of tip temperature monitoring as a predictor of lesion size was tested in 104 serial lesions with tip temperatures that were varied between 50 and 85°C. The tip temperature correlated closely with lesion depth (P = 0.0001, r = 0.92) and width (P = 0.0001, r = 0.88), and was a better predictor of lesion size than measurements of power, current or energy. The temperature at the margin between viable and nonviable tissue was estimated to be 47.9°C. These data demonstrate that during radiofrequency catheter ablation, the radial temperature gradient is predictably hyperbolic and appears to be independent of intramyocardial perfusion if constant electrode temperature is maintained. The use of tip temperature monitoring can accurately predict the ultimate size of radiofrequency‐induced lesions.