bluuebunny/crossref_metadata_2025 huggingface dataset:
Inappropriate Discharge By an Implantable Cardioverter Defibrillator: Recognition of Myopotential Sensing Using Telemetered Intracardiac Electrograms
Authors: SANDLER MATTHEW J. , KUTALEK STEVEN P.
Published: July 2006

Inappropriate therapy from implantabie antitachyarrbythmia devices is a common problem with a variety of etiologies. The verification of arrhythmias or other sensed events that precipitate defibrillating shocks is difficult with first‐and second‐generation devices due to the absence of sufficient data storage and the inability to examine stored and real‐time intracardiac electrograms. In addition, the absence of premonitory symptoms is an unreliable marker for the appropriateness of defibrillator shocks. The incorporation of improved data storage and the ability to inspect intracardiac electrograms in newer devices have greatly increased the ability to diagnose abnormal device behavior as shown in the following case report. Inappropriate implantable cardioverter defibrillator discharge due to myopotential sensing is described. The diagnosis was facilitated by telemetered intracardiac electrograms.
Permanent Ventricular Pacing Via the Great Cardiac Vein
Authors: BAI YUPING , STRATHMORE NEIL , MOND HARRY , GRIGG LEEANNE , HUNT DAVID
Published: July 2006

Two cases of left ventricular pacing via the great cardiac vein are presented. A 64‐year‐old female with a mechanical prosthetic tricuspid valve and slow atrial fibrillation had a failed attempt at pacing from the middle cardiac vein. In a 58‐year‐old male with hypertrophic obstructive cardiomyopathy and brodycardia tachycardia svndrome. transvenous permanent pacing could not be achieved via the right ventricle or middle cardiac vein. In both cases, successful pacing via the great cardiac vein was achieved but with an elevated stimulation threshold. These cases illustrate an alternate transvenous route when difficulties occur using standard ventricular pacing sites.
Long‐Term Clinical Performance of a Central Venous Oxygen Saturation Sensor for Rate Adaptive Cardiac Pacing
Authors: FAERESTRAND SVEIN , OHM OLE‐JORGEN , STANGELAND LODVE , HEYNEN HENRI , MOORE ALAN
Published: July 2006

Rate adaptive ventricular pacemakers using central venous oxygen saturation (O2Sat) to control the pacing rate have been implanted in 14 patients (mean age 71 years), with a mean follow‐up period of 44 months (range 2–63 months). In eight patients the pacemakers were replaced due to signs of battery depletion after an implant duration of 39–58 months. During bicycle exercise testing the O2Sat decreased on average from 61%± 4% at rest to 36%± 4% (P < 0,0001) at peak exercise, and the maximum pacing rate was 122 ± 5 beats/min. The time delay until the O2Sat bad dropped 10%, 65%, and 90% of the total reduction during exercise was 4.8 ± 0.9 seconds, 39.8 ± 3.8 seconds, and 71.3 ± 7.5 seconds, respectively. The O2Sat decreased 9.4%± 2% (P <0.005) from resting supine to resting sitting. Oxygen breathing increased the telemetered O2Sat from the pacemaker by 8.4 %± 1 % (P < 0.001). During follow‐up the O2Sats were relatively stable in 50% of the patients, but demonstrated significant fluctuations in the others. At 1‐year invasive follow‐up O2Sat measured by the pacemaker decreased 22%± 2%, and in blood samples from the right ventricle 22%± 2% from rest to 3 minutes exercise at 25 watts. There was a significant correlation between O2Sat measured by the pacemaker and in blood samples from right ventricle (n = 105; r = 0.73; P < 0.001). In two patients the O2Sat dropped significantly during pneumonia. In another patient episodes of angina pectoris was associated with low O2Sat and a concomitant fast pacing rate.
Digital Signal Processing Chip Implementation for Detection and Analysis of Intracardiac Electrograms
Authors: CHIANG CHIH‐MING JAMES , JENKINS JANICE M. , DiCARLO LORENZO A.
Published: July 2006

The adoption of digital signal processing (DSP) microchips for detection and analysis of electrocardiographic signals offers a means for increased computational speed and the opportunity for design of customized architecture to address real‐time requirements. A system using the Motorola 56001 DSP chip has been designed to realize cycle‐by‐cycle detection (triggering) and waveform analysis using a time‐domain template matching technique, correlation waveform analysis (CWA). The system digitally samples an electrocardiographic signal at 1000 Hz, incorporates an adaptive trigger for detection of cardiac events, and classifies each waveform as normal or abnormal. Ten paired sets of single‐chamber bipolar intracardiac electrograms (1–500 Hz) were processed with each pair containing a sinus rhythm (SR) passage and a corresponding arrhythmia segment from the same patient. Four of ten paired sets contained intraatrial electrograms that exhibited retrograde atrial conduction during ventricular pacing; the remaining six paired sets of intraventricular electrograms consisted of either ventricular tachycardia (4) or paced ventricular rhythm (2). Of 2,978 depolarizations in the test set, the adaptive trigger failed to detect 6 (99.8% detection sensitivity) and had 11 false triggers (99.6% specificity). Using patient dependent thresholds for CWA to classify waveforms, the program correctly identified 1,175 of 1,197 (98.2% specificity) sinus rhythm depolarizations and 1,771 of 1.781 (99.4% sensitivity) abnormal depolarizations. From the results, the algorithm appears to hold potential for applications such as realtime monitoring of electrophysiology studies or detection and classification of tachycardias in implantable antitachycardia devices.
Bretylium Decreases and Verapamil Increases Defibrillation Threshold in Pigs
Authors: JONES DOUGLAS L. , KIM YOU HO , NATALE ANDREA , KLEIN GEORGE J. , VARIN FRANCE
Published: July 2006

Background: Patients with ischemic heart disease may require antianginal and/or antiarrhythmic regimes. These patients may also be candidates for implantable defibrillators. The effects of antiarrhythmics, such as bretylium, or calcium antagonists, such as verapamil, nifedipine, or diltiazem on internal defibrillation efficacy have been inconsistent or are unknown. Methods and Results: The effects of bretylium and verapamil on the energy requirements for ventricular defibrillation threshold (DFT) were determined in 92 open‐chest anesthetized pigs. Triplicate DFTs were determined before and after intravenous administration of saline or one of four doses of verapamil or saline or one of three doses of bretylium, in a balanced random order. Bretylium elicited a dose dependant reduction of DFT (F = 2.72 at 3° and 36° of freedom). DFT was significantly reduced with the highest dose of bretylium, (from 5.9 ± 0.6 f to 4.7 ± 0.6 J, mean ± S.E.M.; P < 0.01). However, cardiac massage was sometimes needed at this dose due to low blood pressure immediately after defibrillation. In contrast, there was a positive correlation between DFT and serum verapamil concentration (r = 0.54, P < 0.001). The highest dose of verapamil significantly increased DFT (from 6.3 ± 0.6 J to 8.2 ± 1.1 J; P < 0.05), at a serum verapamil concentration of 86.6 ± 6.8 ng/ mL. Conclusions: These data indicate that bretylium decreases while verapamil increases the minimum energy requirement for internal defibrillation. Caution is warranted in patients who may be hemodynamically comprised and may be candidates for bretylium therapy or in patients who have marginal DFT value who might be candidates for verapamil therapy.
Upper Rate Pacing After Radiofrequency Catheter Ablation in a Minute Ventilation Rate Adaptive DDD Pacemaker
Authors: van GELDER BERRY M. , BRACKE FRANK A.L.E. , EL GAMAL MAMDOUH I.H.
Published: July 2006

A 58‐year‐old man with an implanted minute ventilation rate adaptive DDD pacemaker underwent RF ablation of the AV junction because of symptomatic supraventricular tachyarrhythmias. Immediately after ablation, while the pacemaker was programmed in the DDDR mode, AV sequential pacing at upper rate was observed. After programming the pacing system to the DDD mode and repeated ablation, no abnormalities were observed. It was concluded that AV sequential upper rate pacing was caused by false interpretation of the RF current by the sensor measuring transthoracic impedance as an indicator for minute ventilation.
Radiofrequency Catheter Ablation as a Primary Therapy for Treatment of Ventricular Tachycardia in a Patient After Repair of Tetralogy of Fallot
Authors: GOLDNER BRUCE G. , GOOPER RUBIN , BLAU WILLIAM , COHEN TODD J.
Published: July 2006

A 20‐year‐old man with previous surgical repair of tetralogy of Falht was admitted with hemodynamically significant ventricular tachycardia that was terminated witb cardioversion. He was found at electropbysiological study to bave easily inducible ventricular tacbycardia that was mapped to the rigbt ventricular outflow tract. Radiofrequency catheter ablation of tbe ventricular tacbycardia focus rendered tbe patient's arrbytbmia noninducible. Tbis case represents a successful radiofrequency catbeter ablation of a ventricular tacbycardia focus associated witb tetralogy of Fallot repair.
Report of the NASPE Policy Conference on Antibradycardia Pacemaker Follow‐Up: Effectiveness, Needs, and Resources
Authors: BERNSTEIN ALAN D. , IRWIN MARLEEN E. , PARSONNET VICTOR , WILKOFF BRUCE L. , BLACK WILLIAM R. , BUCKINGHAM THOMAS A. , MALONEY JAMES D. , REYNOLDS DWIGHT D. , SAKSENA SANJEEV , SINGER IGOR , NICKELSON DANIEL E. , SCHURIG LOIS
Published: July 2006

On May 4–5, 1993, a policy conference was held in San Diego, California, under the sponsorship of the North American Society of Pacing and Electrophysiology (NASPE) to identify the fundamental goals of antibradycardia pacemaker follow‐up, evaluate the effectiveness with which it achieves those goals, and formulate specific recommendations as to how it can be made more effective. The conference addressed clinical, administrative, and educational objectives, focusing on existing and potential resources for follow‐up testing and the appropriate frequency of their application. The training of physicians and associated professionals engaged in follow‐up also was addressed, as were regulatory and reimbursement issues. This report summarizes the conclusions and recommendations arrived at during the conference and subsequently approved by the NASPE Board of Trustees.
Reasons for Reprogramming Dual Chamber Pacemakers to VVI Mode: A Retrospective Review Using a Computer Database
Authors: CHAMBERLAIN‐WEBBER R. , PETERSEN M.E.V. , INGRAM A. , BRIERS L. , SUTTON RICHARD
Published: July 2006

Seven hundred seventy‐one dual chamber pacemakers implanted over a 13‐year period were identified using a computer database. The mean followup period was 40.4 ± 30.9 months (mean ± SD). Thirty‐three (4.3%) patients were reprogrammed to the VVI mode after a mean period of 26.4 ± 29 months. Indications for pacing in those reprogrammed were: complete heart block 45.7%, impaired AV conduction 5.7%, sick sinus syndrome 34.2%, carotid sinus syndrome 11.4%, and vasovagal syndrome 2.8%. The most common reason for reprogramming was development of sustained atrial arrhythmias (atrial fibrillation or flutter), which occurred in 25 patients (3.3% of entire group). The remaining 8(1% of entire group) were reprogrammed because of atrial lead related problems.
Behavior of Different Activity‐Based Pacemakers During Treadmill Exercise Testing with Variable Slopes: A Comparison of Three Activity‐Based Pacing Systems
Authors: ALT ECKHARD , MATULA MARKUS , HöLZER KLAUS
Published: July 2006

A new generation of activity‐based pacemakers incorporates an accelerometer sensitive to low frequency acceleration signals in the anteroposterior direction for sensing of bodily stress. The purpose of our investigation was to test a representative model of these new activity‐based pacemakers (Relay) and compare it with current vibrationand housing pressure‐sensing systems. We tested ten pacemaker patients with implanted Activitrax, Sensolog, and Relay systems during treadmill exercise testing with variable slopes. Devices from the three systems were also strapped externally to the chest of each patient and to ten normal test subjects in the control group. Exercise tests were conducted with changes of treadmill speed and/or treadmill slope. For comparable workloads during constant speed/variable slope and constant slope/variable speed, Relay had similar rate responses (difference not significant). Significant differences (P < 0.05) in rate adaptation attributable to the kind of treadmill exercise (change in treadmill speed or slopes) were observed in the housing pressure‐ and vibration‐based pacemakers. Activity‐based pacemakers with an acceleration sensor adapt pacing rates during treadmill exercises independent of treadmill speed or slope better than those controlled by a conventional housing pressure or vibration sensor.
Early Changes in Defibrillation Threshold Following Implantation of a Nonthoracotomy System in Dogs
Authors: HALPERIN BLAIR D. , HAUPT DAN W. , LEMMER JOHN H. , HOLCOMB SCOTT R. , OLIVER RONALD P. , SILKA MICHAEL J.
Published: July 2006

Background: Nonthoracotomy systems are rapidly becoming the preferred surgical method for implantation of cardioverter defibrillators. Testing is performed at the time of implantation to insure an adequate margin of safety for defibrillation. However, this safety margin may change with lead maturation. This study evaluated changes in defibrillation threshold following implantation of a nonthoracotomy system. Methods and Results: Ten dogs underwent implantation of a nonthoracotomy system consisting of a single catheter with a distal coil electrode in the right ventricular apex and a proximal coil electrode in the superior vena cava forming a common anode with a subcutaneous patch over tbe left tborax. Defibrillation threshold testing, using a biphasic waveform, was performed on each animal under general anesthesia at implantation (day 1) and subsequently on postoperative days 3, 7, 10, 17, 24, 31, 38, and 45. E50, the energy associated with a 50% likelihood of successful defibrillation, was determined at each setting. The mean E50 was 12.2 ± 1.1 J at the time of implantation, increasing 36% to 16.8 ± 2.0 J by day 38 (P < 0.01). Individual increases in E50 of 10–12 J were observed in four animals. Conclusions: Energy requirements for defibrillation with a nonthoracotomy system increase during the early postoperative period, with the highest defibrillation threshold observed at 38 days. This increase may be applicable to humans and should be considered when selecting an adequate energy safety margin for defibrillation at time of implantation.
A Minimal Model of the Single Capacitor Biphasic Defibrillation Waveform
Authors: KROLL MARK W.
Published: July 2006

A quantita tive model of the single capacitor biphasic defibrillation wave form is proposed. The primary hypothesis of this model is that the first phase leaves a residual charge on the membranes of the unsynchronized cells, which can then reinitiate fibrillation. The second phase diminishes this charge, reducing the potential for refibrillation. To suppress this potential refibrillation, a monophasic shock must be strong enoagh to synchronize a critical mass of nearly 100% of the myocytes. Since the biphasic waveform performs this protection function by removing the residual charge (with its second phase), its first phase may be of a lower strength than a monophasic shock of equivalent performance. A quantitative model was developed to calculate the residual membrane voltage, Vm, assuming a capacitive membrane being alternately charged and discharged by the first and second phases, respectively. It was further assumed that the amplitude of the first phase would be predicted by a minimum value plus a term proportional to Vm2. The model was evaluated on the pooled data of three relevant published studies comparing biphasic waveforms. The model explained 79% of the variance in the first phase amplitude and predicted optimal durations for various defibrillator capacitances and electrode resistances. Assuming a first phase of opti mal duration, the optimal second phase duration appears to be about 2.5 msec for all capacitances and resistances now seen clinically. Conclusion: The effectiveness of the single capacitor biphasic waveform may be explained by the second phase “burping” of the deleterious residual charge of the first phase that, in turn, reduces the synchronization requirement and the amplitude requirements of the first phase.
Submammary Pacemaker Implantation: A Unique Tunneling Technique
Authors: ROELKE MARC , JACKSON GUY , HARTHORNE J. WARREN
Published: July 2006

Submaminary pacemaker implantation offers women a cosmetically acceptable alternative to the standard pectoral implant. We present a novel method of submammary implantation performed on ten women aged 13–54 years. The lead electrodes are tunneled from the infraclavicular to the inframammary incision using a long needle, guidewire, and introducers/dilators in a manner analogous to the retained guidewire technique used for standard lead insertion. The procedure can generally be performed under local anesthesia. All patients tolerated the procedure well without acute complications. Over 2‐ to 23‐month follow‐up, there were no lead dislodgments. No patients developed mastitis or incisional complications, and all have been extremely satisfied with the cosmetic results. With proper technique, submammary pacemaker implantation can be performed under local anesthesia with minimal patient discomfort and optimal cosmesis.
Adenosine Induced Torsades de Pointes in a Child with Congenital Long QT Syndrome
Authors: ÇELIKER ALPAY , TOKEL KÜRÇAD , ÇIL ERGUN , ÖZKUTLU SÜHEYLA , ÖZME ÇENCAN
Published: July 2006

Torsades de pointes is a rare arrhythmia characterized by its bradycardia dependence and increased adrenergic discharge, whether it occurs as a congenital anomaly or as an acquired problem resuiting from drug intoxication or other conditions. There are no reliable tests to assess the propensity toward torsades de pointes or evaluate the efficacy of treatment in these patients. Adenosine can result in marked slowing of sinus and ventricular rate and leads to increased sympathic discharge when given intravenously. We induced torsades de pointes in a child with congenital long QT syndrome (Jervell‐Lange‐Nielsen syndrome) using 200 μg/kg IV adenosine bolus. Higher dosage of adenosine (600 μg/kg) did not lead to torsades de pointes after β blockade. Adenosine may induce torsades de pointes in patients with the long QT syndrome and may be used as a test to reproduce the clinical arrhythmia. Whether adenosine proves to be useful for assessing the efficacy of treatment will require extensive investigation in larger series of patients.
Quality‐of‐Life During DDD and Dual Sensor VVIR Pacing
Authors: LUKL J. , DOUPAL V. , HEINC P.
Published: July 2006

Twenty‐one patients (mean age 68 ± 8 years) with dual‐sensor (QT + activity) DDDR pacemaker were randomly assigned to a crossover, double‐blind study in order to evaluate their quality‐of‐life scores. All pacemakers were implanted for sick sinus syndrome (8 patients) or complete heart block (13 patients). The pacemakers were randomly programmed to VVIR or DDD pacing modes for 2‐week periods and then the pacing mode was switched for another 2‐week period. At the end of each period, the quality‐of‐life was evaluated by a questionnaire with regard to cardiovascular symptoms, physical activity, psychosocial and emotional functioning, and self‐perceived health. Nineteen questions were scored 0–5 points each. Significant improvement in the mean total quality‐of‐life score (20.5 ± 14.9 vs 34.8 ± 17.4) as well as in dyspnea on effort, dizzy spells, palpitation, sweating, fatigue, lethargy, emotional functioning, and self‐perceived health was observed during DDD compared to VVIR pacing. No question was scored in favor of VVIR pacing mode. Significant improvements during DDD pacing was demonstrated in all subgroups of patients (sick sinus syndrome, chronotropically competent and incompetent patients, and patients with high degree AV block). Eighteen patients preferred DDD pacing mode, while only one preferred WIR pacing mode. Two remaining patients expressed no preference. The results suggest that DDD pacing offers better quality‐of‐life than dual sensor VVIR pacing in all subgroups of patients commonly indicated for pacemaker implantation.
Long‐Term Stability of P Wave Sensing in Single Lead VDDR Pacing: Clinical Versus Subclinical Atrial Undersensing
Authors: LAU CHU‐PAK , TAI YAU‐TING , LEUNG SUM‐KIN , LEUNG WING‐HUNG , CHUNG FELSA LAI‐WAH , LEE IRIS SIU‐FONG
Published: July 2006

Optimal function of a single lead P wave synchronous rate adaptive ventricular pacing system (VDDR) requires reliable P wave sensing over time and during daily activities. The stability of P wave sensing and the incidence of sensitivity reprogramming in a single pass lead with a diagonally arranged bipole was assessed in 30 patients with complete atrioventricular block over a follow‐up period of 12 ± 1 months (range 6 months to 3 years). Atrial sensing was assessed during clinic visits, by physical maneuvers (postural changes, breathing, Valsalva maneuver, walking and isometric exercise), maximum treadmill exercise and Holter recordings. P wave amplitude at implantation was 1.21 ± 0.09 (0.5–3.6) mV, and the atrial sensing threshold remained stable over the entire period of follow‐up. Using an atrial sensitivity based on twice the sensing threshold at 1 month, P wave undersensing was found in 2, 4, 3, and 7 patients during clinic visit, physical maneuvers, exercise, and Holter recordings, respectively. Atrial sensitivity reprogramming was performed in three patients based on the correction of undersensing during physical maneuvers. Although eight patients had atrial undersensing on Holter recordings, the number of undersensed P waves was small (total 101 beats or 0.013%± 0.001% of total ventricular beats) and no patient was symptomatic. One patient had intermittent atrial undersensing at the highest sensitivity, but the VDDR mode was still functional most of the time. No patient had myopotential interference at ihe programmed sensitivity. One patient developed chronic atrial fibrillation and was programmed to the VVIR mode. Thus, single lead VDDR pacing is a stable pacing mode in 97% of patients. Because of the large variability of P wave amplitude, the use of a sensitivity margin at least three times the atrial sensitivity threshold will maximize atrial sensing and minimize the need for atrial sensitivity reprogramming (1/30 patients). Physical maneuvers and exercise tests are effective means for rapid assess ment of the adequacy of P wave sensing.
Clinical Evaluation of a New Single Pass Lead VDD Pacing System
Authors: OVSYSHCHER ILYA E. , KATZ AMOS , BONDY CHAVA
Published: July 2006

Twenty‐five patients with second‐ to third‐degree AV block and normal sinus function (16 males, mean age 60 ± 18; range 15–78 years) underwent implantation of WD pacemakers (THERA VDD, Medtronic, Inc.) with a single pass (SP) lead. Results: During implantation the mean amplitude of the atrial (A) signal was 3.9 ±1.4 mV (range 2.0–7.8 mV). Stable, acceptable A‐signals during implantation were usually observed in the mid‐ or lower part of the right atrium. The lead tip electrical parameters were not compro mised in any patient in order to obtain an acceptable A‐signal. To verify VDD device function, patients underwent pacing system analysis on the second day and again 1, 3, and 6 months after implantation. Acute and chronic electrical measurements in the ventricle were similar to those with regular steroid leads. During follow‐up tests, stable atrial sensing (A ≥ 0.7mV) was found in all but one patient (in whom A was 0.25–0.5 mV and an intermittent loss of atriai sensing occurred). There was no difference between serial measurements of A‐signal amplitudes on the second day or 1, 3, and 6 months after implantation: 1.9 ± 1.3 mV, 1.5 ± 0.6 mV, 1.3 ± 0.8 mV, and 1.5 ± 1.1 mV, respectively. The mean implantation time was 54.0 ± 17 minutes and the mean fluoroscopy time was 3.2 ±1.3 minutes. Conclusions: SP lead VDD pacing is reliable and easy to manage with dependable atriai sensing and ventricular pacing. The significant reduction in atriai postimplantation amplitude is related to the different techniques used for measuring acute and chronic atriai signals.
Long‐Term Reliability of Single Lead Atrial Synchronous Pacing Systems Using Closely Spaced Atrial Dipoles: Five‐Year Experience
Authors: ANSANI LUCIA , PERCOCO GIAN FRANCO , GUARDIGLI GABRIELE , TOSELLI TIZIANO , ANTONIOLI GIAN ENRICO
Published: July 2006

To assess the long‐term capability of single atrioven ticular (AV) lead VDD pacing systems using close atrial dipoles to assure reliable atrial guided pacing, the safety and efficacy of 86 VDD units implanted in 73 patients at a single center since November 1988 was reviewed. All patients suffered from advanced AV block with normal sinoatrial function. Sixty five patients received a LEM/CCS Twinal 30/30S system, four patients received a Vitatron‐Saphir system, and four patients received a Medtronic Thera VDR 8348 system. All patients underwent provocative tests in search of myopotential interference, and Holter recordings; in a group of patients who underwent pacemaker replacement a comparison was made between implant and replacement measurements. The mean follow‐up duration was 27.3 months. A high percentage of successfully VDD paced patients and a low incidence of pacemaker malfunction, regularly solved by pacemaker reprogramming, was reported. Atrial signal amplitudes comparable to those measured at implant were found at replacement in all patients. These data support the long‐term reliability of single AV lead VDD pacing systems with closely spaced atrial dipoles, as well as stable atrial sensing by floating bipolar atrial electrodes and effective atrial synchronous ventricular pacing over time.
Comparative Evaluation of Bipolar Atrial Electrogram Amplitude During Everyday Activities: Atrial Active Fixation Versus Two Types of Single Pass VDD/R Leads
Authors: CHAN CHI‐CHING , LAU CHU‐PAK , LEUNG SUM‐KIN , TAI YAU‐TING , LEUNG WING‐HUNG , LEE IRIS , TANG MAN‐OI
Published: July 2006

Endocardial P wave amplitude (PWA) is an important determinant of the atrial sensing capabilities of an atrial‐based pacing system. Although changes in PWA during physical activities are known to occur in DDD/R pacing, there is little information on the P wave stability in single pass lead VDD/R pacemakers using floating P wave sensing. We investigated the variation of PWA during daily life activities using telemetry recorded atrial electrograms in 21 patients with DDDR pacemakers (Relay or Elite) and 29 patients with single lead VDD/ R pacemakers (Unity or Thera). Physical activities resulted in marked individual variability of PWA but, as a group, there was no significant difference between PWA during sitting, standing, lying down, and coughing in both DDDR and VDD/R pacing. In the Elite II pacemaker, walking at 2 miles per hour resulted in significant reduction of PWA (11.6% compared with sitting, P < 0.05). The most consistent reduction in PWA occurred in the relaxation phase of the Valsalva maneuver (VM), with all pacemakers showing a reduction in PWA (mean reduction in PWA compared with sitting in DDDR and VDD/R were 16.6% and 12.8%, respectively). Two patients with DDDR pacemakers (Relay) and three patients with VDD/R pacemakers (1 Unity and 2 Thera) had atrial sensing failure during VM or walking. In conclusion, large variation in PWA occurs during daily life activities. The extent of variation is dependent on the patients, types of atrial lead, and the maneuvers performed. A twice sensing threshold may be insufficient to ensure adequate atrial sensing during these activities. The VM, which effects a consistent change in intracardiac volume, is the most reliable method for bedside evaluation of the lower end of sensitivity margin.
Avoiding Atrial Undersensing by Assessment of P Wave Amplitude Histogram Data
Authors: BOUTE W. , ALBERS B.A. , GIELE V.
Published: July 2006

Reliable sensing of the P wave is an essential requirement for the appropriate functioning of any device that uses atrial tracking to provide AV synchrony. However, a single measurement of the P wave amplitude, either at implantation or during follow‐up, may not be a reliable reflection of the P wave amplitudes that occur during daily life. The P wave amplitude histogram is a new feature that automatically measures the P wave amplitude at regular intervals and provides the distribution of these measurements. This enables the assessment of the smallest P wave amplitudes that occur. Two populations were studied: 104 patients with a fixed atrial lead and a DDDR pacemaker and 100 patients with a single pass VDD lead and a VDD pacemaker. Both pacemakers incorporate the P wave amplitude histogram feature. Data in the P wave amplitude histogram were compared with a single measurement of the P wave amplitude at each follow‐up. Programming of a 100% safety margin based on a single measurement of the P wave amplitude provided reliable atrial sensing in only 72% and 43% of the patients of both populations, respectively. Data continued in the P wave amplitude histogram may be a useful adjunct for the optimal programming of atrial sensitivity.
P Wave Recognition and Atrial Stimulation with Fractally Iridium Coated VDD Single Pass Leads
Authors: RES J.C.J. , REIJSOO F.J. , van WOERSEM R.J. , MIDDELHOFF C.J.F.M. , van KALMTHOUT P.M. , ZWART P. , WESTENDORP P.
Published: July 2006

The bottleneck of VDD systems is the reliable detection of the small atrial signals by a floating atrial electrode. Fractally iridium coated electrodes offer excellent sensing and pacing performance. In this study, the performance of such a floating atrial lead in P wave sensing and synchronous ventricular stimulation was examined. Atrial pacing was also used as a test of atrial wall contact. Patients and Methods: A fractally iridium coated VDDlead was implanted in 18 patients. In 15 patients it was interfaced with a VDD pacemaker and in 3 patients with a DDD system depending on the P wave amplitude measured acutely (≥ 2 mV). Simultaneous recordings of the surface ECG and pacemaker telemetry were used to analyze P wave amplitudes and AV synchrony in different body positions, and during normal and deep breathing. Additionally, exercise tests based on daily life activities and 24‐hour ECG monitoring were performed to test the pacemaker function. Results: During implantation P wave amplitudes were 1.86 mV ± 1.08 mV (range 0.5–4.9 mV) and during follow‐up (6.6 ± 5.6 weeks) 0.18–3.8 mV. Holter recordings revealed reliable P wave sensing at a sensitivity setting of 0.5 mV (95.5%). P wave sensing was further improved by a higher atrial sensitivity. AV synchronous pacing ± 99.9% was achieved in all patients. In 7 patients the atrial electrode could be positioned close to the atrial wall enabling atrial stimulation thresholds at an average of 4.3 volts. Conclusion: This fractally iridium coated VVD lead allowed consistent and reliable P wave sensing at an atrial sensitivity as low as 0.5 mV in selected patients.
Initial Experience with Mode Switching in a Dual Sensor, Dual Chamher Pacemaker in Patients with Paroxysmal Atrial Tachyarrhythmias
Authors: den DULK KAREL , DIJKMAN BARBARA , PIETERSE MATTIE , WELLENS HEIN
Published: July 2006

Mode switching algorithms have been developed to avoid tracking of atrial fibrillation (AF) or flutter (AFL) during DDD(R) pacing. Upon recognition of AF or AFL, the mode is switched to a nontracking, sensor driven mode. The Vitatron Diamond model 800 pacemaker does this on a beat‐to‐beat basis. Atrial events occurring within a “physiological range” (± 15 beats/min) calculated from a running average of the atrial rate are tracked. When atrial events are not tracked the escape interval is either determined by the sensor(s) or by a fallback algorithm thereby preventing large increases in V‐V interval during mode switching. Loss of atrioventricular (AV) synchrony by atrial premature beats and after an episode of AF or AFL is prevented by atrial synchronization pulses (ASP), which are delivered after a safe interval (timed out from the sensed premature atrial event) has expired and before delivery of the next ventricular stimulus. We implanted 26 such devices in 18 men and 8 women with symptomatic second‐ or third‐degree AV block and paroxysmal AF or AFL. Their ages ranged from 18–84 years (mean 60), and the follow‐up ranged from 2–13 months (mean 8). During pacemaker check‐up, exercise testing or 24‐hour Holter monitoring one or more episodes of mode switching was documented in 8 patients. In these 8 patients a smooth transition (ventricular rate) from sinus rhythm to AF or AFL was documented on one or more occasions, without inappropriate increase in ventricular rate in the DDDR mode. None of the patients complained of palpitations. Appropriate rate response was seen in all patients during Holter monitoring and exercise. Restoration of AV synchrony with ASP was documented many times. In 2 patients the DDIR mode was programmed due to intermittent synchronization of ventricular stimuli to near incessant supraventricular tachycardia, which sometimes gave rise to asymptomatic slightly irregular ventricular paced rhythms below WO beats/min. Recognition of AF or AFL was reliable. No inappropriate increases in ventricular pacing rate were seen at the onset of or during AF or AFL. ASP is an effective method of maintaining AV synchrony and avoiding competitive atrial pacing.
Initial Experience with a New Algorithm for Automatic Mode Switching from DDDR to DDIR Mode
Authors: OVSYSHCHER ILYA E. , KATZ AMOS , BONDY CHAVA
Published: July 2006

Implantation of dual chamber devices in patients with paroxysmal atrial tachyarrhythmias who require permanent pacemakers may lead to significant complications due to an inappropriately triggered ventricular response. VVI/VVIR units cause loss of AV synchrony in the presence of sinus activity. A new DDDR device (THERA DR, model 7940), with an automatic mode switching (AMS) algorithm, was evaluated. When the mean atrial rate is > 182 beats/min, atrial tachyarrhythmia is detected, and AMS is activated. Twenty‐three patients (12 males, mean age 71 ± 7 years) underwent implantation of a THERA DDDR device with the AMS algorithm. Seventeen patients had AV block and/ or sick sinus syndrome (SSS) and atrial arrhythmias, and 6 patients (2 with hypertrophic obstructive cardiomyopathy) had SSS and paroxysmal atrial fibrillation (PAF). The follow‐up period was from 1–9 months. During follow‐up, Holter monitoring and treadmill tests were performed. Results: Eighty‐seven episodes of AMS were recorded. Telemetered AMS recordings demonstrated episodes in which the DDDR mode switched to the DDIR mode in the presence of PAF, and reverted to DDDR when sinus rhythm returned. Paroxysmal supraventricuiar arrhythmias with a heart rate < 182 beats/min did not activate tbe mode switch. Conclusions: This early, short‐term clinical experience with a DDDR device capable of AMS from DDDR to DDIR demonstrated appropriate clinical function and response to PAF. These preliminary results suggest that DDDR pacemakers with AMS to DDIR may significantly extend the current indications for dual chamber pacing.
The “Automatic Mode Switch” Function in Successive Generations of Minute Ventilation Sensing Dual Chamber Rate Responsive Pacemakers
Authors: PROVENIER FRANK , JORDAENS LUC , VERSTRAETEN THEA , CLEMENT DENIS L.
Published: July 2006

Automatic mode switch (AMS) from DDDR to VVIR pacing is a new algorithm, in response to paroxysmal atrial tachyarrhythmias. With the 5603 Programmer, the AMS in the Meta DDDR 1250 and 1250H (Telectronics Pacings Systems, Inc.) operates when VA is shorter than the adaptable PVARP. With the 9600 Programmer, an atrial protection interval can be defined after the PVARP. The latest generation, Meta DDDR 1254, initiates AMS when 5 or 11 heart cycles are > 150, 175, or 200 beats/min. From 1990 to 1993, 61 patients, mean age 61 years, received a Meta DDDR: in 24 a 1250, in 12 a 1250H and in the remaining 25 a 1254 model. Indication for pacing was heart block in 39, sick sinus syndrome in 15, the combination in 6, and hypertrophic obstructive cardiomyopathy in 1. Paroxysmal atrial tachyarrhythmias were present in 43. All patients had routine pacemaker surveillance, including 52 Holter recordings. In 32 patients, periods of atrial tachyarrhythmias were observed, with proper AMS to VVIR, except during short periods of 2:1 block for atrial flutter in 4. In two others, undersensing of the atrial arrhythmia disturbed correct AMS. With the 1250 and 1250H model, AMS was observed on several occasions during sinus rate accelerations in ten patients. This was never seen with the 1254 devices. Final programmation was VVIR in 2 (chronic atrial fibrillation), AAI in 1 (fracture of the ventricular lead), VDDR in 1 (atrial pacing during atrial fibrillation), DDD in 5, and DDDR in 53, 48 of whom had AMS programmed on. The AMS detection algorithm in the successive models of the Meta DDDR appears to have become more specfic.
Adjusting Heart Rate During Sleep Using Activity Variance
Authors: BORNZIN GENE A. , ARAMBULA ELIA R. , FLORIO JOSEPH , LEVINE PAUL A. , HAUCK GREG
Published: July 2006

In order to mimic the natural decrease in heart rate that occurs during sleep, an algorithm was devised to decrease the base rate to a programmable sleep rate. The algorithm was developed using activity and sinus rate data obtained from 18 normal subjects ranging in age from 22–80 years. The data were recorded in the event record of a “taped‐on” pacemaker. The surface ECG signal was used to inhibit a pacer programmed to VVI at 45 ppm. The ECG documented the sinus rate while the accelerometer‐based activity signals were recorded in an event record. An algorithm was used to estimate the smoothed acceleration variance every 26 seconds. The activity variance was stored in a histogram. Results: The lower 7/24ths of the histogram entries were primarily attributable to sleep. If the activity variance was entered into the lower 7/24ths of the histogram and the accelerometer reading was below rate responsive threshold, the base rate was switched to sleep rate. Using least mean squares to estimate optimal slope, base rate, and sleep rate, the root mean square error between activity derived heart rate and sinus rate was 12 beats/min. Conclusion: This study supports using an estimate of activity variance to automatically decrease pacing rate below programmed base rate. This decrease may be actuated during an afternoon nap or nighttime sleep.
Clinical Study of a New Activity Sensor for Rate Adaptive Pacing Controlled by Electrical Signals Generated by the Kinetic Energy of a Moving Magnetic Ball
Authors: FAERESTRAND SVEIN , OHM OLE‐JØRGEN
Published: July 2006

A new rate adaptive pacemaker (Sensorithm) controlled by an activity sensor providing electrical signals induced by a magnetic ball moving freely in an elliptical cavity surrounded by two copper coils, was implanted in ten patients; mean age of 75 years (range 64–89). Six patients had atrioventricular block and four had sinus node disease. In auto‐set testing procedure during a 1‐minute walk in the corridor, a slope resulting in a maximum rate of 95 beats/min was selected in every patient, and a medium reaction time was programmed. During graded treadmill exercise tests the heart rate increased 63 ± 7 beats/min to 135 ± 6 beats/min in rate adaptive pacing mode (VVIR), and 15 ± 6 beats/min (P < 0.0001) in ventricular pacing mode (VVI). The symptom‐limited exercise time was 9.1 ± 1.1 minutes and 8.2 ±1.2 minutes (P = NS), and the exercise distance was 501 ± 95 meters and 428 ± 92 meters (P < 0.05) in VVIR and VVI pacing mode, respectively. The maximum oxygen uptake was 20.6 ± 2.6 mL/kg per minute in VVIR pacing and 18.1 ± 2.1 mL/kg per minute (P < 0.05) in VVI pacing. The delay time until the pacing rate increased 10% of the total rate increase at onset of treadmill exercise was 4.4 ± 0.7 seconds. Assuming a linear relation between metabolic workload and heart rate response from rest to the age predicted maximum heart rate, a deviation of heart rate ranging from 13.5 ± 11.2% to –1.6 ± 5.2% from the expected heart rate at mid‐point and endpoint of each quartile of workload was observed during treadmill testing. Conclusions: By using a 1 ‐minute walk test for selecting an appropriate slope setting, Sensorithm provided a significant and proportional heart rate increase during exercise resulting in an improvement of exercise capacity during VVIR pacing compared to VVI pacing.
New Algorithms to Increase the Initial Rate Response in a Minute Volume Rate Adaptive Pacemaker
Authors: SLADE ALISTAIR K.B. , PEE SEOW , JONES SUE , GRANLE LAURA , FEI LÜ , CAMM A. JOHN
Published: July 2006

Background: Minute volume is a truly physiological sensor for rate adaptive pacing that correlates with metabolic expenditure throughout the range of physical activity. Criticism has centered on the slow initial response compared to less physiological sensors. A new algorithm, consisting of rate augmentation factor and programmable speed of response, has been incorporated in the 1206 META III pacemaker generator and was designed to improve the rate response at lower levels of exertions. Rate augmentation factor increases the programmed rate response factor by 3, 6, or 10 when set to low, medium, or high, respectively; this augmentation lasting to 50% of the maximum programmed rate. Response time can be programmed to medium or fast. Methods: Nine patients were studied during the first 3 minutes of an exercise test (Bruce protocol) in a single blind manner. The pacemaker generator was randomly programmed with rate augmentation factor at off, low, or high and speed of response to medium or fast, giving six possible combinations. Heart rates were recorded continuously for the duration of the test and until resting heart rate was achieved during recovery. The test was repeated until all six combinations had been tested. Results: During exercise significant differences appeared in response time from 30 seconds onward. Fast response and rate augmentation factor contributed to an improved rate response with greatest speed of response seen with fast response time and high rate augmentation factor. During recovery decreases in recovery time were seen with fast response time but rate augmentation factor prolonged recovery. Conclusions: Rate augmentation factor improves initial rate response in the early stages of exercise. Fast response gives an improved time to initial rate increase and shortens the duration of inappropriate postexercise tachycardia. These features improve the pattern of response of the minute ventilation sensor.
Septal Short Atrioventricular Delay Pacing: Additional Hemodynamic Improvements in Heart Failure
Authors: COWELL RICHARD , MORRIS‐THURGOOD JAYNE , ILSLEY CHARLES , PAUL VINCENT
Published: July 2006

Controversy exists as to whether short AV delay pacing is beneficial in left ventricular dysfunction with the studies performed coming to disparate conclusions. The right ventricular apical pacing previously studied results in asynchronous contraction and relaxation sequences and may limit the potential benefits of short AV delay pacing. In this study the hemodynamic effects of septal (resulting in a more physiological activation sequence) and apical right ventricular activation were compared in 15 patients with heart failure. VDD pacing with AV delays of 50,100, and 150 msec was evaluated. Apical VDD pacing did not increase the cardiac output significantly, 4.1 ± 0.75 to 4.45 ± 0.74 L/min, whereas septal VDD pacing increased the cardiac output to 4.86 ± 0.79 L/min (P = 0.037). Apical pacing increased the cardiac output in 10 patients and septal pacing in 11 patients. We conclude that selected patients with ventricular dysfunction benefit from short AV delay pacing. Septal ventricular activation confers significant hemodynamic improvements over apical activation.
Critical PQ Interval for the Appearance of Diastolic Mitral Regurgitation and Optimal PQ Interval in Patients Implanted with DDD Pacemakers
Authors: ISHIKAWA TOSHIYUKI , SUMITA SINICHI , KIMURA KAZUO , KUJI NAOMITSU , NAKAYAMA RIICHIRO , NAGURA TOSHIRO , MIYAZAKI NAOMICHI , TOCHIKUBO OSAMU , USUI TAKASHI , KASHIWAGI MASANOBU , ISHII MASAO
Published: July 2006

Diastolic mitral regurgitation (MR) may be induced by prolonging atrioventricular (AV) delay, and a significant negative correhtion has been described between tbe critical PQ interval for the appearance of diastolic MR and pulmonary capillary wedge pressure (PCWP) in patients with DDD pacemakers. We report the relationship between the critical PQ interval for the appearance of diastolic MR and the optimal PQ interval in 11 patients (69.1 ± 12.6 years). Cardiac output (CO) and PCWP were measured by Swan‐Ganz catheter and transmitral blood flow was recorded by pulsed‐Doppler echocardiography. AV delay was prolonged stepwise by 0.025 seconds starting from 0.065 seconds. The pacing rate was fixed at 70 beats/min. CO was highest when the PQ interval was 0.18 ± 0.04 seconds. There was a significant positive correlation between the critical PQ interval for the appearance of diastolic MR and the PQ interval at which CO was the highest (r = 0.91, P < 0.01). The PQ interval at which CO was the highest was 0.02 ± 0.02 seconds shorter than the critical PQ interval for the appearance of diastolic MR (P < 0.05). When the PQ interval was increased by 0.025 seconds from the critical PQ interval for the appearance of diastolic MR, CO decreased from 4.3 ± 0.6 L/min to 4.1 ± 0.6 L/min and PCWP increased from 7.5 ± 6.4 mmHg to 8.5 ± 7.3 mmHg (P < 0.05). In conclusion, the critical PQ interval for the appearance of diastolic MR may represent the upper limit of the optimal PQ interval and the AV delay should be set to not exceed the critical PQ interval for the appearance of diastolic MR.
The Effects of Electronic Article Surveillance Systems on Permanent Cardiac Pacemakers: An In Vitro Study
Authors: LUCAS ERIC H. , JOHNSON DELOS , McELROY BRYANT P.
Published: July 2006

Five Siemens Pacesetter cardiac pacemakers (PM) were subjected to in vitro testing with six different electronic article surveillance (EAS) devices. The PMs consisted of polarity programmable, dedicated bipolar, and dedicated unipolar types. EAS equipment included UHF, RF, Magnetic, and Magnetoacoustic (MA) devices from two manufacturers. Prior to testing, each PM was interrogated and normal operation confirmed. Each PM was attached to a heart simulator via an eight foot cable and then subjected to testing within the EAS field. The PMs were passed through the field in two axes, positioned stationary within the field, and, worst case (WC), placed directly against the transmitter. During testing the ECG was observed and PM behavior recorded. In one PM (Synchrony IIIR), Event Records, and Event Histograms were utilized. At the conclusion of testing with each EAS device the PM was evaluated for normal operation. Results: No PM was reprogrammed by the EAS devices. UHF produced no effect on the PMs. RF produced noise response in one unipolar PM while in the WC position. High frequency and multifrequency magnetic units produced positive results only in the WC position. Unipolar PMs were affected more often than bipolar. MA and older magnetic EAS units produced more positive responses than newer lower power devices. One incident of close coupled (400 msec) ventricular pacing was seen with the MA EAS unit. Conclusions: UHF, RF, high frequency, and dual frequency magnetic FAS produced few effects during in vitro testing. Except with the MA and low frequency magnetic devices, positive results occurred only in WC conditions. Additional in vitro and in vivo testing is required to evaluate the interaction between PM patients and EAS devices. Careful evaluation of MA EAS systems with a wide variety of PMs is indicated to rule out RF induction through the lead system of the PM.