bluuebunny/crossref_metadata_2025 huggingface dataset:
Programmable VT Detection Enhancements in Implantable Cardioverter Defibrillator Therapy
Authors: NEUZNER JÖRG , PITSCHNER HEINZ F. , SCHLEPPER MARTIN
Published: July 2006

This report describes the distribution of automatically measured values of enhanced arrhythmia detection parameters such as “rate stability” and “rate onset” in various forms of spontaneous arrhythmia episodes in patients treated with a new, third‐generation, tiered therapy implantable cardioverter defibrillator (ICD). The study population consisted of 27 patients who received the Ventak PRxII cardioverter defibrillator, which provides extensive diagnostic options such as electrogram storage capabilities, and the ability to store measured values of additional arrhythmia detection parameters such as rate stability and rate onset during spontaneous arrhythmia episodes. During a follow‐up period of 11.1 ± 5.2 months, this device detected 264 arrhythmia episodes. The analysis of stored electrograms revealed 13 episodes of sinus tachycardia, 52 episodes of atrial tachyarrhythmias, and 201 episodes of monomorphic ventricular tachycardias (VTs). The mean measured values of rate stability and rate onset were: 2.2 ± 0.9 msec, 0% in sinus tachycardias; 41.0 ± 24.1 msec, 8.5%± 9.5% in atrial tachyarrhythmias; and 7.8 ± 6.0 msec, 30.6%± 12.1% in monomorphic VTs. There was a wide zone of overlapping measured values for rate stability and rate onset in ventricular and nonventricular rhythms. No episode of VT showed a measured rate stability criterion > 35 msec. The subanalysis of arrhythmia episodes presenting with a heart rate < 160 beats/mm revealed no episode of VT with a rate stability value > 24 msec. The calculated, rate dependent specificities for these programmed rate stability parameters in detecting VTs were 46.2% and 81.8%, respectively. The analysis of the rate onset algorithm revealed no comparable relationship between sensitivity and specificity in the detection of VTs. Additional arrhythmia detection algorithms such as rate stability and rate onset may contribute to a significant enhancement in the specificity of lCD therapy.
Holter Functions of the Implantable Cardioverter Defibrillator: What is Still Missing?
Authors: COUMEL PHILIPPE , THOMAS OLIVIER , LEENHARDT ANTOINE
Published: July 2006

The technology of the implantable Cardioverter defibrillator (ICD) offers the opportunity to overcome the present limits of the invasive and noninvasive approaches of clinical electrophysiology. The invasive approach enables us to reproduce severe arrhythmias if they are inducible, but does not give information concerning the way they spontaneously arise. The noninvasive approach (Holter) gives this information, but it usually concerns only trivial arrhythmias with different therapeutic targets. One hopes in the future, by means of an important extension to ICD technology, which is not technically possible for the time being, to have access to pertinent information and to a better understanding of the circumstances leading to severe spontaneous arrhythmias, potentially lethal. For the moment, we only have the diagnostic certainty leading to the therapeutic intervention. It is based on an ECG and on the sequence of cardiac cycles preceding the rhythmic controlled accident. These data allow verification of but not explanation of the events. To have a chance to be understood and explained, these “events” must be replaced in the context of the “nonevents.” Ideally, one should have all the gross information concerning the last 24 hours and subsequently analyze them. It is already a big step, thanks to the defibrillators the right to therapeutic error has been gained, a unique and fatal accident has been transformed into a repeatable event, and therefore, access is gained to the evolution of the responsible disease. I PACE 1995; 18[Pt. II].560–568)
Bipolar Transvenous Defibrillation: Efficacy of Two Different Positions of the Anode
Authors: BLOCK MICHAEL , HAMMEL DIETER , BÖCKER DIRK , BORGGREFE MARTIN , BUDDE THOMAS , CASTRUCCI MARCO , FASTENRATH CHRISTIAN , SCHELD HANS H. , BREITHARDT GUNTER
Published: July 2006

For most nonthoracotomy defibrillotion lead systems, the transvenous anode can be positioned independently of the right ventricular (RV) cathode. Usually a vertical position in the superior vena cava (SVC) is chosen. However, it is unknown if this position yields the optimal defibrillation threshold (DFT). There‐fort, in 15 patients undergoing defibrillator implantation the SVC position was compared in a crossover study design with a horizontal position in the left brachiocephalic vein (BCV). Mean DFT was not different for SVC and BCV (19.2 ± 9.6) vs 18.5 ± 9.1 J) but DFT of individual patients differed by up to 12 joules. A positive correlation between impedance and DFT in the BCV position (r = 0.6; P ≤ 0.05) indicated that the improved geometry of the defibrillation field with the BCV position is opposed by a higher impedance found for this position (63 ± 15 Ω vs 52 ± 7 Ω). Thus, defibrillation is not improved in general although individual patients might benefit.
Electrophysiological Effects of MS‐551 in Humans: A Class III Antiarrhythmic Agent
Authors: ISOMOTO SHOJIRO , KONOE ATSUSHI , CENTURION OSMAR A. , HAYANO MOTONOBU , KAIBARA MUNESHIGE , HIRATA TETSUYA , YANO KATSUSUKE
Published: July 2006

To investigate the clinical effects of MS‐551, a Class III antiarrhythmic agent, 11 patients underwent electrophysiological study. MS‐551 was given intravenously as an initial dose of 0.2 or 0.3 mg/kg for 5 minutes followed by the continuous infusion at 0.2 or 0.3 mg/kg for 30 minutes, respectively, in all patients. The rate corrected QT interval increased significantly from 3 minutes after the beginning of MS‐551 infusion. The sinus heart rate decreased significantly by 8% at 10 minutes after the drug administration (P ± 0.025). Mean PR and QRS intervals, and blood pressure were not significantly affected by the drug. Mean PA, AH, and HV intervals during sinus rhythm were also not affected. The effective refractory periods (ERPs) of the atrium and ventricle were significantly prolonged by 13% from 202 ± 24 ms to 231 ± 26 ms (P ± 0.0005), and by 7% from 238 ± 11 ms to 257 ± 13 ms (P ± 0.002), respectively, by MS‐551. The ERP of the atrioventricular node and sinoatrial nodal recovery time were not changed significantly by the drug. This is a report of the effects of MS‐551 in humans. This agent could be useful for treatment of tachyarrhythmias by prolongation of ERPs of the atrium and ventricle without significant variations of blood pressure and intracardiac conduction times. It is noteworthy that MS‐551 slightly but significantly decreased heart rate.
A Shorter R‐R Interval Causes a Larger Endocardial R Wave Amplitude in Cases with Atrial Fibrillation
Authors: YOKOYAMA MASAYOSHI , NITTA SUMIO
Published: July 2006

Endocardial electrograms were recorded with a Medtronic programmer (model 9742A) in 15 patients with implanted pacemakers required for bradycardia and atrial fibrillation. Telemetered unipolar ventricular endocardial electrograms were recorded for 2 minutes, and the R wave amplitudes of the shortest R‐R intervals were compared to that of the longest R‐R intervals. Eleven of the 15 cases showed R wave amplitudes of the shortest R‐R intervals an average of 2.1 mV larger than the R wave amplitudes of the longest R‐R intervals. Three cases showed no difference, and one the opposite condition. In all four, the average recorded R‐R interval exceeded 670 ms. The shortest R‐R interval among the 11 cases with a larger R wave amplitude was 545 ± 100 ms. The endocardial R wave amplitude of the shortest R‐R intervals were larger than the R wave amplitudes of the longests R‐R intervals. Shorter intervals were followed by larger endocardial R wave amplitudes (P < 0.005 with the Wilcoxon's rank sum test).
The Comparative Predictive Accuracy of Spectral Turbulence Analysis and Time‐Domain Analysis for Sustained Monomorphic Ventricular Tachycardia in Postinfarction Patients with Conduction Defects
Authors: FLOWERS NANCY C. , PERRY GERSHON Y. , WYLDS ANITA C. , SRIDHARAN MARANDAPALLI R. , HORAN LEO G.
Published: July 2006

Signal‐averaged electrocardiograms obtained in 86 postinfarction patients with right bundle branch block (RBBB), left bundle branch block (LBBB), or intraventricular conduction defect (IVC‐D), underwent time‐domain analysis (TDA) and spectral turbulence analysis (STA) to determine which approach provided the more effective marker for patients with sustained monomorphic ventricular tachycardia. TDA parameters included the root mean square value of the last 40 ms of the vectormagnitude complex and the duration of the low amplitude signal below 40 μV STA utilized a summation lead (X + Y + Z) and quantitated four parameters: interslice correlation mean, interslice correlation standard deviation, low slice correlation ratio, and spectral entropy. High‐pass filters of 40 Hz and 25 Hz were used to study the total patient population with noise levels ≤1 μV and a subset of 67 patients with noise levels ≤ 0.5 μV, The techniques compared their effectiveness as measured by their positive predictive values (PPV), negative predictive values (NPV), sensitivity (Sn), and specificity (Sp). In RBBB, STA was uniformly a more powerful tool utilizing either filter at both noise levels. In LBBB, STA was consistently more powerful at both noise levels at 40 Hz and, generally, more powerful at 25 Hz with isolated exceptions. In conduction defects in which QRS was > 100 ms but < 120 ms, TDA was equal to or more effective than STA, with the exception of PPV and Sp at 40 Hz at 1‐μV noise level and the Sp at 0.5 μV. The addition of ejection fraction data to STA score resulted in further overall improvement in performance, but above conclusions were unchanged.
Algebraic Decomposition of the TU Wave Morphology Patterns
Authors: PADRINI ROBERTO , BUTROUS GHAZWAN , CAMM A. JOHN , MALIK MAREK
Published: July 2006

In principle, the T wave results from the differences in durations of action potentials (AP) of different ventricular regions. Based on this concept, a mathematical model has been developed that represents the TU wave morphology as a summation of four AP‐like functions: TU= S1 ‐ S2 + L1 ‐ L2. The sigmoidal shape of AP‐like curves is produced by Hill's equation V(t) = a · tn/(bn+ tn). Each of the decomposition functions is characterized by two parameters: the amplitude at the beginning of QRS (Amax), and the duration at 5% of Amax (D95). The set of four decomposition functions leads to eight parameters that provide detailed characteristics of the TU wave morphology. The model was validated using 170 TU wave complexes recorded digitally in leads V2‐V6 from 22 normal subjects and 12 patients with abnormal TU wave morphologies (negative, biphasic, and notched T waves). The electrocardiographic signals were sampled at 100 Hz and a best‐fit procedure was used to obtain the decomposition. In all cases the coefficients of correlation between original TU patterns and their mathematical models were ≥ 0.99. The mean absolute difference between the observed and modeled values of the TU patterns was similar in cases with normal and abnormal TU wave morphologies (4.65±0.41 μV vs 5.19±0.48 μV, respectively) demonstrating that the model is capable of describing and categorizing various TU patterns by a set of eight numerical parameters.
Environmental Electromagnetic Interference from Electronic Article Surveillance Devices: Interactions with an ICD
Authors: McIVOR MICHAEL E.
Published: July 2006

A patient with an implantable cardioverter defibrillator (ICD) experienced an inappropriate firing while in close proximity to an electronic article surveillance (EAS) device. Testing revealed the ICD was able to detect high frequency “noise” when close to the EAS device. ICD patients may need counseling to avoid close contact with such devices.
Endocardial Fragmented Electrogram and Prediction of Ventricular Tachycardia by Body Surface Signal‐Averaged Electrocardiographic Mapping
Authors: SASAKI YASUYUKI , FURIHATA AKIKO , SUYAMA KAZUHIRO
Published: July 2006

Signal‐averaged (SA) electrocardiography and SA electrocardiographic mapping were performed in 50 patients with old myocardial infarction, 19 of whom had left ventricular aneurysm and 11 of whom had clinical sustained ventricular tachycardia.The SA electrocardiogram and SA electrocardiographic mapping data were then compared with those obtained by endocardial catheter mapping in patients with or without fragmented electrograms, sustained ventricular tachycardia, and ventricular aneurysm. Compared to SA electrocardiography, the SA map correlates with sustained VT with improved sensitivity but decreased specificity. However, SA electrocar diographic mapping had the advantage of displaying the extent of the body surface area that was positive for late potentials. In addition, the site of the longest endocardial fragmented electrogram could be predicted by SA electrocardiographic mapping, suggesting that this technique deserves wider clinical application.signal‐averaged electrocardiography, signal‐averaged electrocardiographic mapping, late potential, sustained ventricular tachycardia
Cardioverter Discharges Following Sensing of Electrical Artifact Due to Fluid Penetration in the Connector Port
Authors: HIEF CHRISTINE , PODCZECK ANDREA , FROHNER KLAUS , NURNBERG MICHAEL , KALTENBRUNNER WILHELM , VEIT FRANZ , STEINBACH KONRAD
Published: July 2006

We report a unique case of fluid penetration, 3 months after implantation, in the connector port of an automatic implantable Cardioverter defibrillator (ICD) with transvenous subcutaneous lead system. The patient had coronary artery disease and recurrent episodes of ventricular fibrillation, the fluid caused electrical signals interpreted as ventricular fibrillation by the device, which triggered shock delivery.
Removal of the Protruding Retention Wire Via a Femoral Approach While Leaving the Active‐Fixation Atrial “J” Lead In Situ: A Technique for the Management of Class III Atrial “J” Leads
Authors: GANZ LEONARD I. , MEYEROVITZ MICHAEL F. , KANDARPA KRISHNA , MITCHELL GARY F.
Published: July 2006

The Telectronics Accufix Atrial “J” pacing lead poses a mechanical risk to patients of retention wire fracture and protrusion. Standard lead extraction techniques include percutaneous approaches, which are associated with significant risk of morbidity and mortality, and open procedures, which necessitate thoracotomy. In nine patients referred with Class III retention wire fractures, attempts were made to snare the protruding retention wire from a femoral approach using snare devices and hioptomes. In six cases, the retention wire was successfully removed, leaving the lead body in place. In four patients with lead function that was able to be evaluated, the atrial lead remained functional after the procedure. There were no complications. Snare removal of the protruding retention wire via a femoral approach should be considered as an option in the management of patients with Class III Accufix leads.
Improved Nonthoracotomy Defibrillation Based on Ventricular Fibrillation Waveform Characteristics
Authors: HSIA PENG‐WIE E. , SURESH GURUNATHAN , ALLEN CYNTHIA A. , HARRINGTON GARY , MASKAL STEVE , FAIN ERIC , DAMIANO RALPH J.
Published: July 2006

The heart has been shown to be more susceptible to defibrillation at a higher absolute ventricular fibrillation voltage (AVFV) measured on the surface ECG. This study evaluated in a closed‐chest canine model (n = 7) the clinical applicability of using a real‐time VF waveform analysis system using an electrogram defined between the generator can and an RV endocardial electrode. Under fluoroscopic guidance, superior vena cava and RV spring coil catheter electrodes were inserted through the external jugular vein. A subcutaneous patch was placed on the left chest. A two‐parameter tracking algorithm was used to dynamically identify the high AVFV area, and a biphasic shock was triggered synchronously at the next peak. The performance of this new peak shock method (PSM) was compared to the conventional method of shocking at a fixed time in 175 paired trials. Five shocks per voltage and five voltages per animal were randomized between the two methods to permit the generation of sigmoidal dose response curves for the estimation of 50% (E50), 75% (E75), and 100% (E100) success energies. Induction of VF and discharge voltage were kept constant while energy delivered, impedance (R), and AVFV at the point of shock were measured. Energy (8.63 ± 0.40 vs 8.64 ± 0.40 J), R (48.60 ± 0.30 vs 48.59 ± 0.30 Ω), and current (7.50 ± 0.18 vs 7.51 ± 0.16 A) were not significantly different between trials for either the conventional or the PSM. The time from the onset of VF until the defibrillation shock was 7.98 ± 1.44 seconds. Higher overall successes (46.3% vs 33.1%; P < 0.01) and lower E50, E75, and E100 were observed for the PSM. Finally, the significantly higher AVFV (9.12 ± 0.32 vs 4.73 ± 0.34 mV; P < 0.0001) with the peak method suggests that the high VF voltage could be detected as it occurred in real‐time. The improved defibrillation success supports the use of this method for nonthoracotomy defibrillation.
Dual Sensor VVIR Mode Pacing: Is It Worth It?
Authors: SULKE NEIL , TAN KIM , KAMALVAND KAYVAN , BOSTOCK JULIAN , BUCKNALL CLIFF
Published: July 2006

Dual sensor ventricular demand rate responsive (VVIR mode) pacing was compared with single sensor rate responsive pacing to assess whether this new development should be more widely incorporated in modern pacemaker devices. A within patient randomized, double‐blind crossover study involving ten patients, mean age 67.4 years (70% male), had Medtronic Legend Plus dual sensor VVIR pacemakers implanted for high grade A V block and chronic or persistent paroxysmal atrial fibrillation. Performance values were compared to 20 healthy control subjects of a similar age and gender. Patients were both subjectively and objectively assessed after 2 weeks of out‐of‐hospital activity in VVIR mode (minute ventilation sensing), VVIR mode (activity sensing), VVIR mode (dual sensor), and VVI mode (no rate response). All patients were assessed for subjective preference for, and objective improvement in, any pacing modality as assessed by standardized daily activity protocols and graded exercise treadmill testing. Subjective perception of exercise capacity and functional status was significantly lower in VVI mode (P < 0.05) compared to any of the VVIR modes, which did not differ. After completion of the study 70% of patients chose VVIR as their preferred mode, with 30% expressing no preference. Forty percent preferred activity sensor WIR mode pacing, 30% preferred dual sensor VVIR mode pacing, and 70% found either dual sensor WIR mode, minute ventilation sensor WIR mode, or both modalities least acceptable. No patient found activity sensing WIR mode least acceptable. Graded treadmill testing revealed significantly lower exercise tolerance during WI mode pacing (P < 0.01) compared to the VVIR modalities, which did not differ. Overall, chronotropic response was best with dual sensor pacing during standardized daily activity protocols and during the standard car journey. The data from this study suggest that there is no marked clinical advantage obtained from the use of dual sensor devices over current activity sensing ventricular demand rate responsive pacemakers, but with the probable added disadvantages of increased size, complexity, cost, and decreased longevity.
Aging and Time‐Domain and Spectral Turbulence Parameters of Signal‐Averaged Electrocardiograms
Authors: REARDON MICHAEL , HNATKOVA KATERINA , MALIK MAREK
Published: July 2006

The effect of age on the time‐domain and spectral parameters of the signal‐averaged ECG (SAECG) is not known. In this study we recorded SAECGs from 138 normal healthy subjects (84 females and 54 males) aged between 7 and 102 years. The recordings were processed in time‐domain and by spectral turbulence analysis. Spearman correlation coefficients were used to assess the relationship among each of the parameters obtained and age in the total population and in the subpopulations of males and females. Linear regression models of individual parameters with age were calculated and compared in males and females. Using conventional diagnostic criteria, 13 recordings (9.4%) were abnormal in time‐domain analysis and 13 (9.4%) were abnormal in spectral turbulence analysis. However, no recording was abnormal in both types of analysis, and the incidence of abnormal SAECG was not age dependent. There were significant correlations between age and 4 of the 5 parameters used to evaluate spectral turbulence analysis (low segment correlation ratio [LSCR], intersegment correlation mean, intersegment standard deviation, and spectral entropy [SE]). However, there was no systematic significant correlation between age and time‐domain parameters. The values of tQRS, mean peaks per slice, LSCR, and SE indices were significantly higher in males than in females, irrespective of age. The study concludes that with increasing age, there is a tendency for the parameters of spectral turbulence analysis to become abnormal, possibly reflecting an increase in conduction abnormalities with age.
Signal‐Averaged Electrocardiography in Healthy Children: Influence of Age, Body Size, and Gender
Authors: VAKSMANN GUY , ELKOHEN MARIAM , DUHAMEL ALAIN , GODART FRANÇOIS
Published: July 2006

Our objective was to determine influence of age, body size, and gender on SAECG signals and to establish normal range for standard SAECG parameters in the pediatric population. Five hundred thirty healthy children and adolescents (290 males, 240 females) aged 6.0–17.3 years were studied with high resolution ECG. Patients were divided into five age groups, and each age group was divided in two subgroups according to gender. Parameters studied were filtered QRS duration, root mean square (RMS) voltage of the last 40 ms and of the last 30 ms of the filtered QRS complex, and duration of the terminal waveform of the filtered QRS < 40 μV of amplitude (LAS). After validation of the distribution of the various variables, means, standard deviations, and 95% confidence intervals were determined for each SAECG parameter at 25‐ to 250‐Hz filtering and at 40‐ to 250‐Hz filtering for the ten subgroups. There was a significant age and body surface area (BSA)‐associated increase in filtered QRS duration in boys and girls, and a decrease in RMS voltage of the end of the QRS complex in girls. In addition, girls had a significantly shorter QRS and longer LAS durations than boys. These differences of signal‐averaged signals between genders were not related to age or body size differences since analysis of covariance with age at evaluation or BSA as covariates showed the same trend. Three children (0.6%) had a SAECG out of normal range for age for the four parameters studied either at 25‐ or 40‐Hz high pass filter. Due to the large sample studied, our results provide a basis for interpretation of SAECG in children. Normal ranges for the various variables were determined, and it appeared that adjustments for age, body size, and gender are mandatory when studying SAECG in children.
The Retropectoral Transaxillary Permanent Pacemaker: Description of a Technique for Percutaneous Implantation of an “Invisible” Device
Authors: SHEFER ARIE , LEWIS BASIL S. , GANG ELI S.
Published: July 2006

This report describes a percutaneous, transaxillary approach for implanting permanent pacemakers in the retropectoral space. This approach was used in 17 patients; indications for the procedure included the need to find a new implantation site in patients with infections and multiple previous pacemaker pocket sites (2 patients), emaciation and absence of sufficient adipose tissue (4 patients), and cosmetic considerations (11 patients). No complications were encountered during the implantation and the results were uniformly excellent in all patients. The pacemaker was “invisible” in each case. We conclude that a percutaneous approach for implanting permanent pacemakers in the retropectoral region is safe and feasible. This approach is likely to be applicable to the implantation of transvenous antitachycardia devices.
Transvalvular Impedance (TVI) Recording Under Electrical and Pharmocological Cardiac Stimulation
Authors: DI GREGORIO F. , MORRA A. , FINESSO M. , BONGIORNI M.G.
Published: July 2006

The cardiac electric impedance was recorded between right atrium and ventricle, throughout the cardiac cycle, by means of a tripolar single pass lead for VDD pacing. The transvalvular impedance signal (TVI) is a sharp periodic wave, with high signal‐to‐noise ratio, that is detected exclusively in the presence of cardiac mechanical activity. The minimum TVI value is attained during the atrial systole, the maximum at the end of ventricular systole. Different parameters of TVI waveform are affected by changes in the inotropic state, and could therefore be proposed as potential signals for new rate responsive algorithms based on the correlation between inotropic and chronotropic regulation. The signal might be used, moreover, for pacing and sensing validation in autoregulating pacemakers and for fibrillation recognition in ICDs.
Evaluation of a New Sensor‐Based Algorithm to Protect Against Atrial Arrhythmias
Authors: DELAY MARC , BRÜLS ANNETTE , MOUNIER CHRISTIAN , VERBOVEN YVES , SOMODY ELISABETH , PUEL JACQUES
Published: July 2006

The SmarTracking (ST) algorithm (Marathon 294–09, Intermedics Inc.) uses the sensor‐calculated rate (SCR) to define a “variation band” for the intrinsic sinus rate. If the sinus rate exceeds the upper limit of the band, the ventricular pacing rate is limited by the ST rate (STR) and Wenckebach behavior is observed. The present study was aimed at evaluating the behavior of the ST mechanism in patients with healthy sinus node, during exercise and at rest. Methods: Twenty‐one patients (15 men; mean age 67.8 ± 9.7 years) with normal sinus function were studied. Heart rate was recorded via the rate profile of the implanted pacemaker (Relay 294–03, Intermedics Inc.), and STR and SCR were obtained via a previously calibrated strap‐on pacemaker. A 15‐minute protocol was used during which subjects alternated periods of walking with periods of rest. Results: The relative difference between the average STR and the average sinus rate (DST) was calculated for each phase of the protocol as well as the maximum number of patients showing inappropriate Wenckebach behavior (#W). At nominal settings, DST was always positive and did not fall below 20%. #W was maximum at rest (5) and during heavy exercise (3). By increasing the STR at rest to 95 ppm and the maximum pacing rate to 150 ppm, the #W was reduced to zero for all types of activity except during very fast walk where #W was 1. Conclusion: In general, there was no competition observed between the STR and the intrinsic rhythm. In some cases, the STR at rest and the maximum pacing rate had to be reprogrammed for optimal performance.
Mode Switch Despite Undersensing of Atrial Fibrillation in ODD Pacing
Authors: BONNET JEAN‐LUC , BRUSSEAU ELISABETH , LIMOUSIN MARCEL , CAZEAU SERGE
Published: July 2006

Mode switching algorithms are commonly used to protect the ventricles against high rates induced by atrial tachycardia. In the case of atrial fibrillation (AF), the response of these algorithms depends on the quality of atrial sensing. The Chorum 7234 DDDR pacemaker uses a new mode switching algorithm, based on a statistical analysis of the atrial rhythm. It includes two criteria of diagnosis: “high” if more than 28 of 32 cycles are abnormally accelerated; and “low” if more than 36 of 64 cycles are abnormally accelerated. Methods: From a taped database of electrophysiological studies, episodes of AF lasting more than 2 minutes were selected. A tape recorder replayed the atrial signals into an external Chorum device. Each episode was replayed eight times with a programmed atrial sensitivity increasing from 0.4 –2.0 mV. For each criterion of diagnosis and each programmed sensitivity, the percentage of atrial sensing, the time to switching, and the mean ventricular rate were measured. Ten episodes of AF from 10 patients (9 men and 1 woman; ages 62 ± 16 years) were included: 1.95 ± 0.97 mV and 196 ± 64 ms. The sensitivity of the algorithm to diagnose atrial tachycardia reached 100%, for an atrial sensitivity set between 0.4 and 1.0 mV. The mean percentages of atrial sensed events were 74%± 18% and 46%± 9% for the “high” and “low” criteria, respectively. The mean diagnostic times were 28 ± 26 seconds and 68 ± 27 seconds, respectively. Sensing of < 23% of AF events resulted in failure to diagnose the arrhythmias by both algorithms. In the event of diagnostic failure, the mean ventricular pacing rate was 79 ± 9 ppm. Conclusion: Up to an atrial sensitivity of 1 mV, 100% of AF episodes were diagnosed. The Chorum mode switching algorithms are 100% reliable if > 45% of the AF waves are sensed. In the event of switching failure, the ventricle is protected by an average rate remaining below 80 ppm. (PACE 1996;
Ventricular Protection Against Atrial Arrhythmias in DDD Pacing Based on a Statistical Approach: Clinical Results
Authors: GENCEL LAURENT , GEROUX LAURENCE , CLEMENTY JACQUES , SHAH DIPEN , CAZEAU SERGE , SAOUDI NADIR , PIOGER GUY , LAVERGNE THOMAS
Published: July 2006

Atrial arrhythmias (AA) are commonly encountered in DDD paced patients. Newer dual chamber pacemakers (PM) possess mode switching functions that convert pacing to an asynchronous mode when AAs are detected. The lack of a reliable mode switch leading to rapid, irregular ventricular responses may result from AA undersensing. To avoid this, the DDDR PM Chorum 7234 Eta Medical AA diagnosis is based on a statistical approach: the PM constantly compares arrhythmic and sinus cycles and, based on “strong” and “weak” criteria, provides for rapid or slower mode switch. The aim of the study was to evaluate the efficiency and reliability of these two criteria. Thirty‐one patients with a Chorum 7234 implanted for AV block (11), sinus dysfunction (10), both (5), or hypertrophic obstructive cardiomyopathy (5) were evaluated at 24 hours and 1 month using the internal memory (IM) of the PM, surface 24‐hour Holter recordings, and exercise testing. Interrogation of the IM on the first day of study showed that 8 patients had mode switching episodes, based only on the strong criterion confirmed by the surface Holter recording. At I month, the IM revealed mode switching episodes in 12 patients, 6 of whom had used the weak criterion. No inappropriate mode switching episode was recorded during exercise testing at the 1‐month follow‐up. These results confirm the reliability and efficiency of this algorithm as well as the requirement for a specific algorithm to compensate for transient loss of sensing during AA.
Effect of Varying Atrial Sensitivity, AV Interval, and Detection Algorithm on Automatic Mode Switching
Authors: PALMA EUGEN C. , KEDARNATH VAIDYA , VANKAWALLA VIREN , ANDREWS CAROLYN A. , HANSON SANDRA , FURMAN SEYMOUR , GROSS JAY N.
Published: July 2006

Automatic mode switching (AMS) is absolutely dependent on atrial tachyarrhythmia detection. The effects of programming several features that could influence tachyarrhythmia detection were assessed in 18 patients (six women; mean age 64 years) with pacemakers having AMS capability. The atrial electrogram amplitude in sinus rhythm at implant (SR‐EGM), last measured atrial sensing threshold prior to tachycardia (A‐SENS), and atrial sensing threshold for effective AMS during atrial tachyarrhythmia (AMS‐SENS) were obtained. Additionally, ten patients had AV intervals increased from 60 to 200 ms, while seven patients had detection algorithms made more stringent from 5 beats at 150 beats/min to 11 beats at 200 beats/min to assess their effects on AMS efficacy. Results: Sensitivities: Mean SR‐EGM = 3.55 mV; mean A‐SENS = 2.06 mV; and mean AMS‐SENS = 1.46 mV. Fourteen patients developed atrial fibrillation and four atrial flutter. Thirteen of 14 patients who developed atrial fibrillation sensed adequately at ≥ 1.0 mV in normal sinus rhythm (NSR), but only six patients had effective AMS at these settings in atrial fibrillation. Three of four patients who developed atrial flutter had effective AMS at ≥ 2.0 mV. AV Interval: AMS was effective in eight of ten patients at AV intervals up to 200 ms. One patient lost AMS at an AV interval of 120 ms. Algorithm: In two of seven patients, AMS was not effective if the detection algorithm was more stringent than five beats at 150 beats/min. Conclusions: (1) In atrial fibrillation, effective AMS requires more sensitive atrial settings than in NSR: (2) AV intervals as short as 120 ms can interfere with AMS function; and (3) More stringent detection algorithms may be inappropriate for effective AMS function.
Use of Automatic Mode Change Between DDD and AAI to Facilitate Native Atrioventricular Conduction in Patients with Sick Sinus Syndrome or Transient Atrioventricular Block
Authors: MAYUMI HISANORI , KOHNO HIROYUKI , YASUI HISATAKA , KAWACHI YOSHITO , TOKUNAGA KOUICHI
Published: July 2006

The benefits of the automatic DDD (DDD/AMC) mode in the Chorus II pacemaker (Chorus 6234; Ela Medical Inc.), which automatically switches the modes between DDD and AAI to respect spontaneous AV conduction as much as possible in AAI while preserving safety pacing in DDD during paroxysmal AV block (AVB) only, remain unproven. This study examined the functions of the DDD/AMC mode in 12 patients with sick sinus syndrome (SSS; n = 10) or paroxysmal complete AVB (n = 2). A short‐term (24 hours) comparative study between simple DDD mode and the DDD/AMC mode was performed in 8 of the 12 patients, and a medium‐term (55.2 ± 54.6 days) follow‐up of the DDD/AMC mode was completed in all 12 patients. A comparative pair of 24‐hour surface Holter ECGs was obtained in 6 of the 8 patients in the short‐term study. Telemetry and built‐in Holter histograms were collected in the outpatient clinic in all 12 patients. Although the percentage atrial pacing of the telemetry increased from 59.2 ± 35.4 in DDD to 70.4 ± 31.8 in DDD/AMC (P < 0.009; n = 8), the percentage ventricular pacing decreased from 64.6 ± 37.7 in DDD to 36.2 ± 43.1 in DDD/AMC (P < 0.027) in the short‐term study. In particular, the reduction of percentage ventricular pacing to < 10% was observed in four patients with SSS not associated with ± first‐degree (1°) AVB on preoperative ECGs. Between the two modes a significant difference in arrhythmic events was not observed by the 24‐hour surface Holter ECGS taken from the six patients in the short‐term study. AAI‐DDD switching associated with automatic modulation of AV delay and AV hysteresis occurred in all patients in the medium‐term study. From the medium‐term study, the total AV delay (AV delay plus AV hysteresis) exceeded 300 ms in 6 of the 12 patients in DDD/AMC, and usually became longest during nighttime. From the short‐ or medium‐term study in the 12 patients, two patients preferred the DDD/AMC mode while one preferred the DDD mode. These results suggest that the DDD/AMC mode is useful, at least in SSS patients without ≥ 1° AVB, by reducing the percentage ventricular pacing.
Single Lead VDD Pacing: Multicenter Study
Authors: OVSYSHCHER ILYA E. , KATZ AMOS , ROSENHECK SHIMON , ERDMAN SHIMSHON , BONDY CHAVA
Published: July 2006

Optimal treatment for patients with AV block and normal sinoatrial node (SA) function entails atrial sensing and ventricular pacing (VDD mode). Single‐lead VDD pacing preserves AV synchrony, precludes the need to insert two leads, and makes the implanter's work simpler and quicker. Our objectives were to verify the performance of the Thera(tm) VDD pacing system (Medtronic, Inc., Minneapolis, MN, USA), and evaluate the effectiveness of its atrial sensing and its ventricular sensing and pacing. In 165 patients, 150 adults (mean age 62 ± 18 years) and 15 children (mean age 7 ± 5 years) with 1°–3° AV block and normal SA node function, a Thera VDD system (Models 8948 or 8968) was implanted. Intraoperative ventricular electrical measurements were not significantly different from those of VVI pacemakers. The mean amplitude of the atrial signal during implantation was 4.1 ± 1.9 mV. Optimal atrial signals during implantation were usually obtained in the mid or lower part of the right atrium by using a special technique. Adequate atrial measurements remained stable throughout 24 months. There was no difference between serial measurements of atrial signal amplitudes at predischarge and during follow‐up visits. Reposition of the lead was done in 2 patients (1.4%), and reprogramming to VVI in 7 patients: due to atrial fibrillation in 3 (1.8%) and due to atrial undersensing in 4 patients (2.4%). Thera VDD pacing is reliable and easy to manage with dependable atrial sensing and ventricular pacing. The survival rate of VDD pacing at 2 years was 96%.
Italian Experience with AutoCapture in Conjunction with a Membrane Lead
Authors: SERMASI SERGIO , MARCONI MARCO , LIBERO LUIGI , MORACCHINI PIER VITTORIO , RUSCONI LUIGI , MININNO ANTONIO , SIGLIANO RICCARDO ,   on behalf of THE PACESETTER AUTOMATIC CONTROL OF ENERGY AND MEMBRANE AUTOMATIC THRESHOLD EVALUATION (PACEMATE) STUDY GROUP
Published: July 2006

AutoCapture(tm) is a programmable feature of the Pacesetter Microny(tm) SB+2425T VVIR pacemaker, which provides for the automatic capture verification, increase in output in the presence of noncapture and threshold searching, with adjustment of output settings. The effectiveness of this unit in conjunction with the Membrane(tm) models 1400 T and 1401 T bipolar endocardial leads was studied in 54 patients followed at 19 Italian Centers. The patients were randomized at the time of implantation to receive either the model 1400 T or the 1401 T lead. The electrodes in these leads are covered by a Nafion membrane, which was either impregnated (model 1400T) or not‐impregnated (model 1401 T) with steroid. This paper reports the data collected over the first six weeks postimplantation. The results of the automatic capture function was compared to the capture threshold measured using the Vario(tm) technique at the time of predischarge evaluations, and weeks 1, 2, and 6 of postimplant follow‐up. The reliability and effectiveness of the pulse generator‐lead system allowed for consistent pacing at very low outputs and safety preserved at a programmed output only 0.3 V above the capture threshold.
Failure Rates of Leads, Pulse Generators, and Programmers Have Not Diminished Over the Last 20 Years: Formal Monitoring of Performance is Still Needed
Authors: KAWANISHI DAVID T. , SONG SUSAN , FURMAN SEYMOUR , PARSONNET VICTOR , PIOGER GUY , PETITOT JEAN‐CLAUDE , GODIN JACQUES‐FRANÇOIS ,   for the BILITCH REGISTRY and STIMAREC
Published: July 2006

Formal Monitoring of Performance is Still Needed. In order to detect trends in the number of device or component failures that have occurred among permanent pacemaker systems since the 1970s, we reviewed the data of the five largest pacemaker manufacturers from the Bilitch Registry of permanent pacemaker pulse generators, the Stimarec failure registry, the general accounting office summaries of the United States Veterans Administration (VA) Registry of Pacemaker Leads, and the Implantable Lead Registry, from the Cleveland Clinic Lead registry, and the recalls and safety alerts issued by the United States Food and Drug Administration (FDA) over the last 20 years. The definition of failure followed the criterion, or criteria, developed within each registry and differed significantly between the registries. The 20‐year period between 1976 and 1995 was divided into 5‐year quartiles (QT): QT 1 = 1976–1980; QT2 = 1981–1985; QT 3 = 1986–1990; and QT4 = 1991–1995. For pulse generators, the number of models with failures in each quartile in the Bilitch Registry were: QT 1 = 9; QT 2 = 11; QT 3 = 17; QT 4 = 13. In Stimarec, the number of units reported as having reached a dangerous condition were: QTl = 710; QT2 = 212; QT3 = 114; QT4 = 310. From the FDA reports, the number of units included in recalls or safety alerts were: QT 3 = 6,085; QT4 = 135, 766. For permanent pacemaker leads, the numbers of failed or dangerous leads recorded in Stimarec were: QT 3 = 16; QT 4 = 32. In the VA Registry, the number of models having a below average survival was 2/92 (2.7%). In the Implantable Lead Registry, the number of models having a below average survival was 3/21 (14%). In the Cleveland Clinic series, 6/13 (46%) of lead models were recognized to have some failure involving the conductor, insulation, or connector. In the FDA reports, the number of leads involved in either recall or safety alert were: QT3 = 20,354; QT 4 = 332,105. For programmers, the number of units involved either in a recall or safety alert were: QT 3 = 11,124; QT 4 = 3,528. In all of these series, each of the five largest manufacturers had some models or units involved in each time period. This review of programs has revealed: 1. The incidence of failures, recalls, or safety alerts did not decline over time; and 2. Despite changes in technology, formal monitoring of pacemaker systems is still warranted.
Heart Rate Variability and Major Arrhythmic Events in Patients with Idiopathic Dilated Cardiomyopathy
Authors: HOFFMANN JÜRGEN , GRIMM WOLFRAM , MENZ VOLKER , KNOP URSULA , MAISCH BERNHARD
Published: July 2006

This prospective study of 71 patients with idiopathic dilated cardiomyopathy (IDC) and preserved sinus rhythm was designed to evaluate the relation between heart rate variability (HRV) and subsequent major arrhythmic events. Standard time‐ and frequency‐domain HRV parameters were obtained from analysis of 24‐hour Holter ECG recordings. During a mean follow‐up of 15 ± 5 months, major arrhythmic events including sustained ventricular tachycardia, ventricular fibrillation, and sudden cardiac death occurred in 10 of the 71 study patients (14%). Neither time‐ nor frequency‐domain indices of HRV differed significantly between patients with and patients without subsequent major arrhythmic events. However, there was a trend toward a lower standard deviation of the average normal RR interval for all 5‐minute segments of the 24‐hour recording (68 ± 17 ms vs 80 ± 31 ms; P = 0.06) in patients with major arrhythmic events. In addition, the percentage of adjacent normal RR intervals differing > 50 ms over the recording period tended to be lower in patients with major arrhythmic events (6%± 3% vs 9%± 6%; P = 0.08). Our results indicate a tendency toward attenuated parasympathetic activity in IDC patients with subsequent major arrhythmic events compared to arrhythmia‐free patients. Larger studies with longer follow‐up periods are necessary to clarify the role of HRV measurements for arrhythmia risk prediction in patients with IDC.
Step wise Strategy of Using Short‐ and Long‐Term Heart Rate Variability for Risk Stratification After Myocardial Infarction
Authors: FABER THOMAS S. , STAUNTON ANNE , HNATKOVA KATERINA , CAMM A. JOHN , MALIK MAREK
Published: July 2006

Independent of other established risk factors, depressed heart rate variability (HRV) has been shown to be a powerful predictor of cardiac events after MI. Unfortunately, the need of 24‐hour ECG recording and subsequent laborious editing of Holter data limits the clinical use of long‐term HRV. In order to perform post‐Mi risk stratification more efficiently, we evaluated the value of short‐term HRV estimates for preselection of patients who might benefit from long‐term HRV assessment, Two measures were assessed from 24‐hour ambulatory ECGs recorded in 729 survivors of acute MI prior to hospital discharge. In addition to a complete 24‐hour HRV index, a standard deviation of normal‐to‐normal RR intervals (SDNN) was obtained from the first stationary and ectopic free 5‐minute segment of the Holter recording. Predictive power (relation between positive predictive accuracy and sensitivity) of a complete 24‐hour HRV index in identifying patients who suffered from cardiac mortality or arrhythmic events during a 2‐year follow‐up was compared to the predictive power of assessing the 24‐hour HRV index limited to 50%, 40%, or 20% of patients with the lowest values of 5‐minute SDNN. The HRV index was significantly lower in patients who died (19 ± 11 units) or had an arrhythmic event (AE) (18 ± 11 units) compared to those who survived without an event (28 ± 10 resp. 27 ± 11 units; P < 0.001). Similarly, 5‐minute SDNN was significantly lower in patients who died (25 ± 12 ms) or suffered an AE (26 ± 13 ms) compared to survivors (40 ± 19 ms resp. 39 ± 19 ms; P < 0.001). When limited to patients with depressed 5‐minute SDNN, assessment of the HRV index performed better than 5‐minute SDNN alone in positive prediction of cardiac events. Preselected assessment of the lowest HRV index in 50% to 20% of the total population yielded a 2‐year cardiac event prediction rate as high as analysis of the HRV index in all patients. Long‐term HRV assessment for risk stratification after MI in patients preselected by depressed short‐term SDNN is safe and efficient, and allows a practical identification of patients with the highest likelihood of cardiac events during long‐term follow‐up.
Heart Rate Variability in Myocardial Infarction With and Without Malignant Arrhythmias: Comparison with Heart Transplant Recipients and Normal Subjects
Authors: RODRIGUES THIAGO R. , MIRANDA REYNALDO C. , LICHTER ARTUR P. , LOBO NILCIO C. , FIGUEROA CARLOS S. , MOREIRA MARIA da CONSOLAÇÃO
Published: July 2006

Myocardial autonomic denervation occurs after acute MI. This process is followed by a reduction of heart rate variability (HRV) and an increase of malignant ventricular arrhythmias and sudden death. This study investigated whether there are any significant differences in HRV among the population of MI who did and did not have malignant ventricular arrhythmias (MVAs), normal subjects and heart transplant recipients, the paradigm of the denervated heart. We studied 25 subjects aged 42 ± 17 years, with normal clinical and cardiac noninvasive evaluation (group A); 70 patients aged 57 ± 14 years, who had MI hut no arrhythmic event in 36 months of follow‐up (group B); 13 patients with MI aged 65 ± 9 years, who had had sustained VT, VF, or sudden death (group C); and 16 cardiac transplant recipients aged 35 ± 14 years (group D). The ECG was sampled for 256 seconds. We calculated, in time and frequency domain, the standard deviation of the RR cycle length and the spectral component's very low frequency (< 0.05 Hz), low frequency (0.05–0.15 Hz), and high frequency (0.15–0.35 Hz). The values of HRV in group A were significantly greater than in groups B, C, and D (P < 0.001) and greater in group B than in groups C and D (P < 0.001). Groups C and D did not differ (P = 0.610). These data indicate that HRV of patients who have had an MI and MVAs is very similar to that of heart transplant recipients. This is an indirect evidence that myocardial autonomic denervation may play an important role in the genesis of malignant arrhythmic events.