bluuebunny/crossref_metadata_2025 huggingface dataset:
Is Automatic Mode Switching Effective for Atrial Arrhythmias Occurring at Different Rates? A Study of the Efficacy of Automatic Mode and Rate Switching to Simulated Atrial Arrhythmias by Chest Wall Stimulation
Authors: LEUNG SUM‐KIN , LAU CHU‐PAK , LAM CATHY TSE‐FUN , TSE HUNG‐FAT , LEE KATHY , CHAN WAI‐KWONG , LEUNG ZOE
Published: June 2006

Automatic mode switching (AMS) is a useful means to avoid rapid ventricular response during atrial fibrillation (AF), but AMS cannot occur if the detected atrial rate during AF is below the mode switching criteria. This may be the result of antiarrhythmic medications, or when the atrial events fall within the atrial blanking period, or if the atrial amplitudes during AF are too small to be sensed. We hypothesize that the addition of an automatic rate switching (ARS) algorithm may complement AMS response during AF with different detected atrial rates. We studied the Marathon DDDR pacemaker (Model 294–09, Intermedics Inc.) with the AMS and ARS algorithms that are independently programmable but can also operate in combination. AF sensed above the AMS rate (160 beats/mm) will lead to VDIR pacing, whereas AF below AMS rate will be tracked at an interim rate as dictate by the ARS, at a ventricular response that is 20 beats/min above the sensor indicated rate. Atrial tachyarrhythmias were simulated by chest wall stimulation (CWS). CWS was applied to 33 patients (16 men, 17 women, mean age 69 ± 11 years) with a Marathon DDDR pacemaker using an external pacer to simulate AF occurring at two rate levels: above the AMS rate (programmed at 160 beats/min) at 180 beats/min and below the AMS rate at 120 beats/min. The maximum, minimum, and mean ventricular rates during CWS in DDDR mode with AMS alone, ARS alone, and their combination were compared. During CWS at 120 beats/min, the AMS plus ARS setting showed a mean ventricular rate of 79 ± 3 beats/min and 124 ± 14 beats/mm in the AMS setting alone (P < 0.01). With CWS at 180 beats/min, the mean ventricular rate in the AMS plus ARS setting compared to the AMS setting alone was not significantly different. However, the variation in ventricular pacing rate was 7 ± 14 beats/min in the AMS plus ARS setting and 40 ± 42 beats/min in the AMS setting (P < 0.05). In conclusion, AMS is effective for simulated atrial tachyarrhythmias sensed above the AMS rate. Combined AMS with ARS is useful to handle simulated atrial tachyarrhythmia at a slower rate and to avoid rate fluctuation during AMS. There is also a possibility that this can be applied to the naturally occurring atrial tachyarrhythmias.
Factors Affecting the Frequency of Subcutaneous Lead Usage in Implantable Defibrillators
Authors: TRUSTY JANE M. , HAYES DAVID L. , STANTON MARSHALL S. , FRIEDMAN PAUL A.
Published: June 2006

Subcutaneous leads (SQ) add complexity to the defibrillation system and the implant procedure. New low output devices might increase the requirement for SQ arrays, although this might be offset by the effects of active can and biphasic technology. This study sought to assess the impact of these technologies on SQ lead usage, and to determine if clinical variables could predict the need for an SQ lead. Patients receiving nonthoracotomy systems (n = 554) at our institution underwent step‐down‐to‐failure DFT testing with implant criteria of a 10‐J safety margin. SQ leads were used only after several endovascular configurations failed, Use of biphasic waveforms significantly lowered the frequency of use of SQ leads from 48% to 3.7% (P < 0.000001), SQ leads were required in 4.4% of patients with cold can devices and 2.6% of patients with active can devices (P = NS). There was no increase in SQ lead usage with low energy (< 30‐f delivered energy) devices. Clinical variables (including EF, heart disease, arrhythmia, and prior bypass) did not predict the need for an SQ lead. The implant DFT using SQ arrays (14.5 ± 6.5 J) was not significantly lower than that for SQ patches (16.6 + 6.0 J). We conclude that biphasic waveforms significantly reduce the need for SQ leads. Despite this reduction, 3.7% of implants still use an SQ lead to achieve adequate safety margins. The introduction of lower output devices has not increased the need for SQ leads, and when an SQ lead is required, there is not a significant difference in the implant DFT of patches versus arrays. Clinical variables cannot predict which patients require SQ leads.
Age Effect on Phase Relations Between Respiratory Oscillations of the RR Interval and Systolic Pressure
Authors: PITZALIS MARIA VITTORIA , MASSARI FRANCESCO , MASTROPASQUA FILIPPO , FIORETTI AGNESE , GUIDA PIETRO , COLOMBO ROBERTO , BALDUCCI CATALOG , RIZZON PAOLO
Published: June 2006

Spectral analysis may allow the evaluation of (baroreflex) gain and phase between the RR interval and systolic pressure oscillations synchronous with respiration hut, unlike baroreflex gain, the determinants of phase are not completely understood. We evaluated the correlates of spectral phase in 92 healthy subjects (44 men) aged 10–80 years. To do so, the cardiorespiratory signals during paced breathing at 16 breaths/min were continuously recorded and analyzed. In addition, respiratory sinus arrhythmia and baroreflex gain (two indices of cardiac vagal activity) and phase were calculated by using an autoregressive spectral technique. At univariate analysis, the phase correlated with age (r = 0.48, P < 0.001), the RR interval (r = 0,32, P < 0.01). respiratory sinus arrhythmia (r =−0.3. P < 0.01). baroreflex gain (r =−0.29, P < 0.01), and body mass index (r = 0.25, P < 0.05). At multivariate analysis, age was the most important physiological correlate of phase, accounting for 23% of interindividual phase variation. Cardiac vagal activity measures (which were higher in women than men) and the HR interval were also significant independent correlates of phase. We conclude that in addition to the RR interval and cardiac vagal activity, age has a significant impact on the phase relationship between respiratory related oscillations of the RR interval and systolic blood pressure. This spectral measure may contain additional information concerning the mechanisms that influence cardiovascular rhythms.
Successful Treatment of Idiopathic Left Ventricular Outflow Tract Tachycardia by Catheter Ablation or Minimally Invasive Surgical Cryoablation
Authors: FREY BERNHARD , KREINER GERHARD , FRITSCH STEFAN , VEIT FRANZ , GÖSSINGER HEINZ D.
Published: June 2006

Idiopathic right ventricular outflow tract tachycardia is readily amenable to radio frequency catheter ablation. However, treatment modalities for left ventricular outflow tract tachycardia are not well defined. Out of 37 patients with idiopathic outflow tract tachycardia referred for catheter ablation, in 3 patients tachycardia originated from the left ventricular outflow tract. On the surface ECG, all left ventricular tachycardias exhibited an inferior axis with a predominant negative QRS complex in lead I. Heart rate during tachycardia ranged from 115 to 170 beats/mill. During electrophysiological testing, 1 patient had inducible tachycardia on orciprenaline challenge, 1 patient had inducible tachycardia at baseline, and 1 patient had incessant tachycardia. In two patients, earliest ventricular activation was recorded from the endocardial left ventricular outflow tract at an anterolateral and an anterior site, respectively. A distinct high frequency spike preceeded the QRS onset by 66/78 ms. Application of radiofrequency energy successfully eliminated tachycardia at these sites. In one patient, tachycardia originated from the epicardial left ventricular outflow tract. Mapping of the anterior interventricular vein revealed a fractionated low amplitude signal occurring 46 ms before QRS onset. After failure of catheter ablation from the corresponding endocardial site, successful minimally invasive surgical focal Cryoablation of the epicardial target region was performed. During a follow‐up period ranging from 7 to 12 months, all patients remained free of tachycardia. In conclusion, ventricular tachycardia arising from the left ventricular outflow tract may require endo‐ and epicardial mapping. Successful treatment is achieved by radiofrequency catheter ablation or minimally invasive surgical Cryoablation.
Use of a Single Coil Transvenous Electrode with an Abdominally Placed Implantable Cardioverter Defibrillator in Children
Authors: FISCHBACH PETER S. , LAW IAN H. , II MACDONALD DICK , LEROY SARAH , MOSCA RALPH S. , SERWER GERALD A.
Published: June 2006

While transvenous defibrillator electrode placement avoiding a thoracotomy is preferable, electrode size, a large intercoil spacing, and the need for subclavicular device placement preclude this approach in most children. We investigated a single RV coil to an abdominally placed active can ICD device. Five children ages 8–16 years (weight 21–50 kg, mean 35 kg) underwent ICD placement. Placement of a single coil Medtronic model 6932 or 6943 electrode was performed via the left subclavian vein approach and the electrode positioned in the RV apex with the coil lying along the RV diaphragmatic surface. The ICD (Medtronic Micro Jewel II model 7223Cx) was implanted in a left abdominal pocket with the lead tunneled from the infraclavicular region to the pocket. Implant DFTs were ± 15 J using a biphasic waveform. DFTs rechecked within 3‐month postimplant were unchanged. Lead impedance at implant ranged from 38 to 56 Ω, mean 51 Ω. Follow‐up was 3–21 months (total 82 months) with no electrode dislodgment. lead fractures, or inappropriate discharges. Two of the five patients have had successful appropriate ICD discharges. Transvenous ICD electrode placement can be performed in children as small as 20 kg with the device implanted in a cosmetically acceptable abdominal pocket that is well tolerated. Excellent DFTs can be achieved. This approach avoids a thoracotomy in all but the smallest child, does not require subclavicular placement of the device, and avoids use of a second intravascular coil.
Transthoracic Pacing in a Very Low Birth Weight Infant with Congenital Complete Atrioventricular Block
Authors: NÜRNBERG JAN‐HENDRIK , WENG YUGUO , OEFF MICHAEL , LANGE PETER ERNST , VERSMOLD HANS T.
Published: June 2006

We report our experience of pacemaker treatment in a premature infant of 830 g with congenital complete atrioventricular block due to maternal Sjogren's Syndrome. The infant was delivered by cesarean section at an estimated gestational age of 26 weeks because of fetal bradycardia, decreasing fetal movements, and hydrops. Immediate postnatal transesophageal ventricular pacing was not successful, whereas transthoracic pacing with self‐adhesive patch electrodes adapted to body size resulted in an effective increase of the infant's heart rate until operative application of temporary epimyocardial pacing wires allowed external stimulation of the heart.
Pathological Findings of the Isthmus Between the Inferior Vena Cava and Tricuspid Annulus Ablated by Radiofrequency Application
Authors: KOHNO ISAO , ISHIHARA TSUKASA , UMETANI KEN , SAWANOBORI TAKAO , IJIRI HIROSHI , KOMORI SADAYOSHI , TAMURA KOHJI
Published: June 2006

Anatomically guided radiofrequency ablation for the treatment of atrial flutter was performed in a 41‐year‐old man with interstitial pneumonia. He died of respiratory failure 2 months after ablation, and an autopsy was performed. The whole layer of the ablation site showed a transluminal fibrosis.
Wenckebach Upper Rate Response in Single Chamber Pacemaker
Authors: BAROLD S. SERGE
Published: June 2006

The Medtronic Minix pacemaker during normal function in the VVT mode was found to exhibit a Wenckenbach upper rate response similar to that of dual chamber devices. This behavior occurred only when the upper rate interval was longer than the pacemaker refractory period. In a single chamber device this response may simulate pacemaker malfunction.
Effects of Electrical Stimulation Postcardiomyoplasty in a Model of Chronic Heart Failure: Hemodynamic Results After Daily 12‐Hour Cessation Versus a Nonstop Regimen
Authors: CHEKANOV VALERIE S. , TCHEKANOV G.V. , RIEDER M.A. , HARE J. , MORTADA MOHAMMAD
Published: June 2006

The hemodvnamic effects of cardiomyoplasty (CMP) have been investigated in many centers, but the question of whether it is necessary to stimulate the latissimus dorsi muscle (LDM) 24 hours a day has not been answered. The main goal of our investigation was to determine whether hemodynamic results after CMP were impaired when continuous electrical stimulation (ES) was off for 12 hours a day, A model of chronic heart failure was created in 12 sheep by performing an arteriovenous anastomosis and administering doxoruhicin. Two weeks after the anastomosis. CMP was performed in eight sheep (experimental series); ES training was begun at 2 weeks after CMP. After completion of the initial ES conditioning (8 weeks after CMP), one group of sheep continued to receive ES 24 hours daily. Another group of sheep had only 12 hours of ES daily. Hemodynamic parameters were investigated 2 weeks later with the stimulator turned on and then off. With doxorubicin administration, arteriovenous anastomosis created a stable model of biventricular heart failure (right atrial pressure 20 ± 3 mm Hg vs 6 ± 2 mm Hg at baseline; pulmonary capillary wedge pressure 18 ± 3 mmHg vs 9 ± 2 mmHg; left ventricular end‐diastolic area 15.2 ± 1.2 cm2 vs 6.4 ± 0.7 cm2; left ventricular ejection fraction 0.38 ± 0.6 vs 0.65 ± 0.7). Cardiomyopiasty improved hemodynamic status in all eight experimental sheep. However, when the investigation was performed with the stimulator off, this improvement was statistically insignificant. With stimulation on, there was decreased right atrial pressure, pulmonary capillary wedge pressure, left ventricular end‐diastolic volume, and increased left ventricular ejection fraction. With the stimulator turned off for 12 hours daily, hemodynamic measurements did not differ from data with continuous ES for 24 hours daily. Because hemodynamic results do not seem to be impaired, we recommend daily, periodic cessation of stimulation to prevent damage to the LDM after CMP.
P Wave Dispersion on 12‐Lead Electrocardiography in Patients with Paroxysmal Atrial Fibrillation
Authors: AYTEMIR KUDRET , ÖZER NECLA , ATALAR ENVER , SADE ELIF , AKSÖYEK SERDAR , ÖVÜNÇ KENAN , OTO ALI , ÖZMEN FERHAN , KES SIRRI
Published: June 2006

The prolongation of intraatrial and interatrial conduction time and the inhomogeneous propagation of sinus impulses have been shown in patients with atrial fibrillation. Recently P wave dispersion (PWD), which is believed to reflect inhomogeneous atrial conduction, has been proposed as being useful for the prediction of paroxysmal atrial fibrillation (PAF). Ninety consecutive patients (46 men, 44 women; aged 55 ± 13 years) with a history of idiopathic PAF and 70 healthy subjects (42 men, 28 women; mean age, 53 ± 14 years) were studied. The P wave duration was calculated in all 12 leads of the surface ECC. The difference between the maximum and minimum P wave duration was calculated and this difference was defined as P wave dispersion (PWD = Pmax ‐ Pmin). All patients and controls were also evaluated by echocardiography to measure the left atrial diameter and left ventricular ejection fraction (LVEF). There was no difference between patients and controls in gender (P = 0.26), age (P = 0.12), LVEF (66 ± 4% vs 67 ± 5%, P = 0.8) and left atrial diameter (36 ± 4 mm vs 34 ± 6 mm, P = 0.13). P maximum duration was found to be significantly higher in patients with a history of PAF (116 ± 17 ms) than controls (101 ±11 ms. P < 0.001). P wave dispersion was also significantly higher in patients than in controls (44 ± 15 ms vs 27 ± 10 ms, P < 0.001). There was a weak correlation between age and P wave dispersion (r = 0.27, P < 0.001). A P maximum value of 106 ms separated patients with PAF from control subjects with a sensitivity of 83%, a specificity of 72%, and a positive predictive accuracy of 79%. A P wave dispersion value of 36 ms separated patients from control subjects with a sensitivity of 77%, a specificity of 82%, and a positive predictive accuracy of 85%. In conclusion, P maximum duration and P wave dispersion calculated on a standard surface ECG are simple ECG markers that could be used to identify the patients with idiopathic paroxysmal atrial fibrillation.
The Acute Effects of Biatrial Pacing on Atrial Depolarization and Repolarization
Authors: GILLIGAN DAVID M. , FULLER ITHIEL A. , CLEMO HENRY F. , SHEPARD RICHARD K. , DAN DAN , WOOD MARK A. , ELLENBOGEN KENNETH A.
Published: June 2006

Permanent biatrial and/or multisite atrial pacing may prevent atrial fibrillation (AF), but the effects on atrial electrophysiology remain incompletely understood. Acute biatrial pacing was studied in 20 patients with and 28 without (controls) a history of atrial fibrillation and/or flutter. Twelve‐lead electrocardiograms were recorded during pacing from the high right atrium (RA), from the distal coronary sinus (LA), and biatrial pacing. P wave duration was measured in each lead and the difference between maximum and minimum P duration was termed P wave dispersion. Effective refractory periods (ERPs) were measured during each pacing mode. The dispersion of P wave duration was 35 ± 14 ms in controls and 40 ± 29 ms in AF patients (P = 0.17). Compared to RA pacing, LA pacing shortened P duration in controls (127 ± 18 to 107 ± 16 ms, P < 0.05) and biatrial pacing markedly shortened P duration in controls (127 ± 18 to 93 ± 14 ms, P < 0.05) and AF patients (114 ±43 to 97 ± 21 ms, P < 0.05). P wave dispersion was unaffected. In controls, the LA ERP was longer than the RA ERP. This phenomenon was not present in AF patients, whose LA ERP was shorter than that of controls. Biatrial pacing had no effect on atrial ERPs or the dispersion of atrial refractoriness. In conclusion, acute biatrial pacing does not affect atrial repolarization but it does cause a marked shortening of global biatrial depolarization. Distal coronary sinus pacing produces a shorter P wave than RA pacing. There is substantial dispersion in the surface P wave of the electrocardiogram, the significance of which awaits further study.
Effects of Aging and Gender on QT Dispersion in an Overtly Healthy Population
Authors: KASSOTIS JOHN , COSTEAS CONSTANTINOS , BEDI ASHWANI K. , TOLAT ANEESH , REIFFEL JAMES
Published: June 2006

The objective of this study was to measure the normal variation of QT dispersion (QTd) with respect to age and gender. The QT interval is a measure of the duration of ventricular depolarization and repolarization, while the QTd is a measure of the variability of the ventricular recovery time. The QTd has been suggested as a means of identifying those patients at risk for sustained ventricular tachyarrythmias and sudden cardiac death (SCD). A total of 250 patients (120 women, 130 men; age range 20–86 years) were recruited for this study. The QT intervals were measured in each of the 12 standard leads of the electrocardiogram. Data are presented as mean (μ) ± SD. The QTd did not vary significantly within the same gender, A significant difference (P < 0.001) was noted in QTd between men (age [μ] = 53.3 ± 15.6 years, QTd= 0.044 ± 0.019 s) and women (age [μ] = 52.1 ± 15.1 years, QTd= 0.034 ± 0.015 s). Overall, men had a greater QTd, while women had a longer QT. In conclusion, we found that men had a longer QTd which may explain the increased risk of SCD. However, women have a longer QT interval with a smaller QTd A longer QTmin, as opposed to a longer QTmax, is responsible for the shorter QTd in women. This longer QTmin in women may predispose to an increased risk of drug induced torsades de pointes.
Chronic Amiodarone Effects on Epicardial Conduction and Repolarization in the Isolated Porcine Heart
Authors: LACROIX DOMINIQUE , SAUTIÈRE KARINE , ADAMANTIDIS MONIQUE , DUMOTIER BÉRENGÈRE , GRANDMOUGIN DANIEL , EXTRAMIANA FABRICE , KACET SALEM , DUPUIS BERNARD
Published: June 2006

Amiodarone is a potent antiarrhythmic agent with complex chronic effects, notably on repolarization and conduction, that are not fully understood. Its low arrhythmogenic potential has been related to a lack of increase in repolarizution dispersion. Since its effects are not documented in pigs we conducted a mapping study of activation and repolarization in isolated perfused porcine hearts. Amio20 female pigs (n = 7) received amiodarone 20 mg/kg per day over 4 weeks while Amio 5O female pigs (n = 7) received 50 mg/kg per day over 4 weeks. Concentrations of the drug encompassed values found in clinical studies. Then, activation patterns and activation‐to‐recovery intervals (ARI) were mapped epicardially from 128 unipolar electrograms in isolated perfused hearts in corroboration of epicardial action potential recordings. Mean ARI was longer in Amio20 experiments compared to the seven control hearts (325 ±11 ms vs 288 ± 5 m.s at 1,000 ms), whereas ARI dispersion was not different, being comprised between 7 and 11 ms and generating smooth gradients. In Amio5O experiments, mean ARI was further prolonged (390 ±10 ms at 1,500 ms) with an exaggerated reverse rate dependence concomitant with a depressant effect on the plateau of the action potential. Again, ARI dispersion did not differ from controls. Finally, the drug depressed the maximal rate of depolarization (Vmax) and slowed conduction in a rate dependent and concentration dependent fashion. In conclusion, chronic amiodarone induces Class I and Class HI antiarrhythmic effects in ventricular porcine epicardium that are concentration dependent but does not affect dispersion of repolarization. This may partly explain its low arrhythmogenic potential.
Dual Demand Pacing Using Retriggerable Refractory Periods for Ventricular Rate Control During Paroxysmal Supraventricular Tachyarrhythmias in Patients with Dual Chamber Pacemakers
Authors: JAYAPRAKASH SHENTHAR , SPARKS PAUL B. , KALMAN JONATHAN M. , MOND HARRY G.
Published: June 2006

The use of dual chamber pacing in patients with atrioventricular block and paroxysmal Supraventricular tachyarrhythmias may present a clinical dilemma because of the rapid and erratic triggering of ventricular pacing. To avoid this, a variety of pacing methods have now been described, including the use of retriggerable atrial refractory periods or dual demand pacing. This review details the use, advantages, and limitations of this poorly understood algorithm referred to as “pseudo‐mode switching.”
Radiofrequency Catheter Ablation from the Left Sinus of Valsalva in a Patient with Idiopathic Ventricular Tachycardia
Authors: TAKAHASHI NAOHIKO , SAIKAWA TETSUNORI , ORIBE AYAKO , OOIE TATSUHIKO , IWAO TETSU , ARIKAWA MASAYA , NAKAGAWA MIKIKO , HARA MASAHIDE , TAKAKURA TAKESHI , SHIMOIKE EIMEI , KAJI YOSHIKAZU , ITO MORIO , SAKATA TOSHIIE
Published: June 2006

We report the case of a 54‐year‐old woman with idiopathic VT originating in the left ventricular outflow tract. She initially presented with palpitations and light‐head‐edness. The morphology of the PVCs exhibited an inferior axis and tall R waves were noted in all the precordial leads. Spontaneous PVCs were transiently terminated by an intravenous injection of adenosine triphosphate. Radiofrequency catheter ablation from the left sinus of Valsalva successfully abolished the PVCs and the VT.
Coexistent Atrioventricular and Nodoventricular Pathways in a Patient with Hypertrophic Cardiomyopathy
Authors: FITCHET ALAN , LINKER NICHOLAS J. , FITZPATRICK ADAM P.
Published: June 2006

A 17‐year‐old girl with concentric hypertrophic cardiomyopathy presented with a wide complex tachycardia and underwent electrophysiological study. She was found to have an antidromic tachycardia utilizing a decremental atrioventricular fiber as the anterograde limb with retrograde conduction occurring through the septum. Ablation of a right free‐wall pathway rendered tachycardia noninducible, yet ventricular preexcitation remained. After ablation there was evidence of a second nodoventricular connection. We believe this to be the first report of coexistent “Mahaim” fibers; one a decremental atrioventricular connection and the second nodoventricular.
Electrophysiological Control of Ventricular Rate During Atrial Fibrillation
Authors: WANINGER MATTHEW S. , BOURLAND JOE D. , GEDDES LESLIE A. , SCHOENLEIN WILLIAM E. , GRABER GEORGE , WEIRICH WALTER E. , WODIGKA GEORGE R.
Published: June 2006

Thirteen anesthetized canine subjects (17–29 kg) were used to demonstrate that mild cervical left vagal stimulation could control ventricular rate effectively during atrial fibrillation (AF). Two studies are presented. The first study used six subjects to demonstrate the inverse relationship between (manually applied) left vagal stimulation and ventricular excitation (R wave) rate during AF. As left vagal stimulation frequency was increased, ventricular excitation rate decreased. In these studies, a left vagal stimulus frequency of 0–10 per second reduced the ventricular excitation rate from > 200/min to < 50/min. The decreasing ventricular excitation rate with increasing left vagal stimulation frequency was universal, occurring in all 26 trials with the six subjects. This fundamental principle was used to construct an automatic controller for use in the second study, in which seven subjects were used to demonstrate that ventricular rate can be brought to and maintained within a targeted range with the use of an automatic (closed‐loop) controller. A 45‐minute record of automatic ventricular rate control is presented. Similar records were obtained in all seven subjects.
Comparison of Mid‐term Clinical Experience with Steroid‐Eluting Active and Passive Fixation Ventricular Electrodes in Children
Authors: CEVIZ NACI , ÇELIKER ALPAY , KÜÇÜKOSMANOĞLU OSMAN , ALEHAN DURSUN , KILIÇ AYHAN , ÜNER ABDURRAHMAN , ÖZME SENCAN
Published: June 2006

Although active fixation ventricular leads seem to have advantages over passive fixation leads, this study compares the follow‐up results of active and passive fixation leads in children. We evaluated the implantation and follow‐up data of 41 children with active (Ac‐cufix II DEC, group 1) (n = 20) or passive (Membrane E, group 2) (n = 21) fixation, steroid‐eluting ventricular leads. All but one of the patients in group 1 completed the 12‐month follow‐up. The mean follow‐up period in group 2 was 10.4 ± 2.9 months (range 3–12 months, median 12 months). In both groups the mean pacing threshold was measured as 0.51 ± 0.09 V versus 0.48 ± 0.15 V (P > 0.05) at 0.5‐ms pulse width, mean R wave amplitude as 9.9 ± 2.5 m V versus 9.4 ± 3.2 mV (P > 0.05), and mean impedance as 557 ± 92 Ω versus 664 ± 160 Ω (P < 0.05), respectively, at implantation. After the first week of pacing, mean threshold values in group 1 were significantly lower than those of group 2 (P < 0.01 and P < 0.05, respectively). During the follow‐up period, lead impedance measurements did not show a significant difference between the two groups. In one patient from group 1, the lead (by unscrewing) was removed easily because of pacemaker pocket infection. No lead dislodgement or helix deformation occurred in group 1. Nevertheless, in one patient from group 2, the lead was extracted at 4‐month postimplantation because of lead displacement. We conclude that the steroid‐eluting active fixation lead (Accufix II DEC) have advantages of easier implantation and lower acute and chronic stimulation thresholds compared to the passive fixation lead (Membrane E). Therefore, Accufix II DEC is superior to Membrane E, and it is a better first choice in children with an implanted single chamber ventricular pacemaker.
Hemodynamically Optimized Temporary Cardiac Pacing After Surgery for Congenital Heart Defects
Authors: JANOUŠEK JAN , VOJTOVIČ PAVEL , CHALOUPECKÝ VÁCLAV , HUČÍN BOHUMIL , TLÁSKAL TOMÁŠ , KOSTELKA MARTIN , REICH OLEG
Published: June 2006

Disturbance of normal AV synchrony and dyssynchronous ventricular contraction may be deleterious in patients with otherwise compromised hemodynamics. This study evaluated the effect of hemodynamically optimized temporary dual chamber pacing in patients after surgery for congenital heart disease. Pacing was performed in 23 children aged 5 days to 7.7 years (median 7.3 months) with various postoperative dysrhythmias, low cardiac output, and/or high inotropic support and optimized to achieve the highest systolic and mean arterial pressures. The following four pacing modes were used: (1) AV synchronous or AV sequential pacing with individually optimized AV delay in 11 patients with first‐to third‐degree AV block; (2) AV sequential pacing using transesophageal atrial pacing in combination with a temporary DDD pacemaker for atrial tracking and ventricular pacing in three patients with third‐degree A V block and junctional ectopic tachycardia, respectively, who had poor signal and exit block on atrial epicardial pacing wires; (3) R wave synchronized atrial pacing in eight patients with junctional ectopic tachycardia and impaired antegrade AV conduction precluding the use of atrial overdrive pacing; (4) Atrio‐biventricular sequential pacing in two patients. Pressures measured during optimized pacing were compared to baseline values at underlying rhythm (13 patients with first‐degree AV block or junctional ectopic tachycardia) or during pacing modes commonly used in the given clinical situation: AAI pacing (1 patient with slow junctional rhythm and first‐degree AV block during atrial pacing), WI pacing (2 patients with third‐degree A V block and exit block and poor sensing on epicardial atrial pacing wires) and dual‐chamber pacing with AV delays set to 100 ms (atrial tracking) or 150 rns (AV sequential pacing) in 7 patients with second‐ to third‐degree A V block and functional atrial pacing wires. Optimized pacing led to a significant increase in arterial systolic (mean) pressure from 71.5 ± 12.5 (52.3 ± 9.0) to 80.5 ± 12.2 (59.7 ± 9.1) mmHg (P < 0.001 for both) and a decrease in central venous (left atrial) pressure from 12.3 ± 3.4 (10.5 ± 3.2) to 11.0 ± 3.0 (9.2 ± 2.7) mmHg (P < 0.001 and < 0.005, respectively). In conclusion, several techniques of individually optimized temporary dual chamber pacing leading to optimal AV synchrony and/or synchronous ventricular contraction were successfully used to improve hemodynamics in patients with heart failure and selected dysrhythmias after congenital heart surgery.
Efficacy of Single Lead VDD Pacing in Patients with Impaired and Normal Left Ventricular Function
Authors: SCHUCHERT ANDREAS , JAKOB MICHAEL , TREESE NOBERT , SCHÖPFEL ANDREAS , SCHMIDT WILHELM , JUNG WERNER , KREUZER JOCHEN , STAEDT ULRICH , STERTMANN WILHELM ALFRED , MEINERTZ THOMAS
Published: June 2006

Atrial synchronous ventricular pacing seems to be the best pacing mode for patients with advanced AV block and impaired LV function. The long‐term follow‐up of single lead VDD pacing was studied in 33 patients with impaired LV function and compared to 42 patients with normal LV function. All patients received the same VDD lead and VDDR pacemaker. The lead model with 13‐cm AV spacing between the atrial and ventricular electrode was implanted in 89% of the patients. Follow‐ups were 1, 3, 6, and 12 months after implantation. The percentage of atrial sensing and the P wave amplitude were determined at each follow‐up. Minimal P wave amplitude at implantation was 2.0 ± 1.4 mV in patients with impaired and 1.7 ± 0.9 mV with normal LV function (not significant). At the 12‐month follow‐up, 33 patients with normal and 23 patients with depressed LV function remained paced in the VDD mode. The remaining patients died in five (impaired LV function) and seven cases (normal LV function) or their pacemakers were programmed to the VVI/VVIR pacing mode in four (impaired LV function) and three cases (normal LV function). P wave amplitude did not differ in the two groups (e.g., at month 12: impaired: 1.17 ± 0.42 mV; normal: 1.09 ± 0.49 mV). The atrial sensitivity was programmed in most patients to sensitive settings with no differences between the two groups (e.g., at month 12: impaired: 0.13 ± 0.06 mV; normal: 0.13 ± 0.05 m V). The diagnostic counters indicated nearly permanent atrial sensing (e.g., at month 12: impaired: 99.3 ± 2.2%; normal: 99.0 ± 1.0 mV). In conclusions, single lead VDD pacing restored AV synchronous ventricular pacing in patients with normal and with impaired LV function indicating that it could be an alternative to DDD pacemakers, but not to dual‐chamber pacing.
A Prospective Randomized‐Controlled Trial of Ventricular Fibrillation Detection Time in a DDDR Ventricular Defibrillator
Authors: ELLENBOGEN KENNETH A. , EDEL THOMAS , MOORE STEPHEN , HIGGINS STEVEN , PACIFICO ANTONIO , WILBER DAVID , WOOD MARK A. , ROGERS REGINA , DAHN ANGELIE , ZHU ALAN ,   THE VENTAK AV II DR STUDY INVESTIGATORS
Published: June 2006

Implantable cardioverter defibrillators (ICDs) with dual chamber and dual chamber rate responsive pacing may offer hemodynamic advantages for some ICD patients. Separate ICDs and DDDR pacemakers can result in device to device interactions, inappropriate shocks, and underdetection of ventricular fibrillation (VF). The objectives of this study were to compare the VF detection times between the Ventak AV II DR and the Ventak AV during high rate DDDR and DDD pacing and to test the safety of dynamic ventricular refractory period shortening. Patients receiving an ICD were randomized in a paired comparison to pacing at 150 beats/min (DDD pacing) or 175 beats/min (DDDR pacing) during ICD threshold testing to create a “worst case scenario” for VF detection. The VF detection rate was set to 180 beats/min, and VF was induced during high rate pacing with alternating current. The device was then allowed to detect and treat VF. The induction was repeated for each patient at each programmed setting so that all patients were tested at both programmed settings. Paired analysis was performed. Patient characteristics were a mean age of 69 ± 11 years, 78% were men, coronary artery disease was present in 85%, and a mean left ventricular ejection fraction of 0.34 ± 0.11. Fifty‐two episodes of VF were induced in 26 patients. Despite the high pacing rate, all VF episodes were appropriately detected. The mean VF detection time was 2.4 ± 1.0 seconds during DDD pacing and 2.9 ± 1.9 seconds during DDDR pacing (P = NS). DDD and DDDR programming resulted in appropriate detection of all episodes of VF with similar detection times despite the “worst case scenario” tested. Delays in detection may be seen with long programmed ventricular refractory periods which shorten the VF sensing window and may be avoided with dynamic ventricular refractory period shortening.
The Strength‐Duration Curve and Its Importance in Pacing Efficiency: A Study of 325 Pacing Leads in 229 Patients
Authors: COATES STEPHEN , THWAITES BARNABY
Published: June 2006

Pacemaker battery life is dependant on programmable parameters, principally pulse, amplitude and pulse duration. High factory default settings cause excessive current drain. The strength‐duration curve relates pacing threshold to pulse duration. The most energy efficient pacing occurs at chronaxie, a value of pulse duration derived from the curve. Strength‐duration curves were calculated for 325 acutely implanted pacing leads. Chronaxie and rheobase were compared for atrial and ventricular leads. Chronaxie was compared with actual programmed pulse duration. There were 101 atrial and 224 ventricular leads, all passive fixation. The curve fit was good, (mean error ± SD) 0.024 ± 0.06 V for atrial curves and 0.008 ± 0.034 V for ventricular curves. Mean (± SD) atrial and ventricular chronaxies were 0.24 ± 0.07 ms and 0.25 ± 0.07 ms, respectively. A “Z” value of 1.4 indicated that chronaxies might have been from the same population. Mean (± SD) atrial and ventricular rheobases were 0.51 ± 0.2 V and 0.35 ±0.13 V, respectively. A “Z” value of 7.1 (P < 0.001) suggested atrial and ventricular rheobases were from differing populations. AH patients had factory default pulse durations of 0.45 ms or 0.5 ms, exceeding acute chronaxie by a factor of two, thus, demonstrating suboptimal pacing. We conclude that understanding the strength‐duration curve is critical. Sensible programming of other pacing functions optimizes longevity. Battery drain is reduced by programming pulse duration to chronaxie with a doubling of voltage threshold at this point to achieve a safety margin. Further study of chronaxie drift with time is required.
Reduction in Defibrillation Threshold Using an Auxiliary Shock Delivered in the Middle Cardiac Vein
Authors: ROBERTS PAUL RICHARD , URBAN JON FREDRIC , BETTS TIM , ALLEN STUART , DIETZ ANDREW , EULER DAVID EMMERSON , WHITMAN THERESA , KALLOK MICHAEL JOHN , MORGAN JOHN MARK
Published: June 2006

Defibrillation in the middle cardiac vein (MCV) has been shown to reduce ventricular defibrillation thresholds (DFTs). Low amplitude auxiliary shock (AS) from an electrode sutured to the left ventricle at thoracotomy have also been shown to reduce DFT if delivered immediately prior to a biphasic shock (between the ventricular RV and superior vena caval (SVC) electrodes). This study investigates the impact on DFT of an AS shock from a transvenously placed MCV lead system. A standard de‐fibrillation electrode was positioned in the RV in eight anesthetized pigs (35–43 kg). A 50 × 1.8‐mm electrode was inserted in the MCV through an 8 Fr angioplasty guide catheter. A 150‐V (leading edge) monophasic AS was delivered (95 μF capacitor) from the MCV → Can with three different pulse widths (3, 5, 7 ms). A primary biphasic shock (PS) (95 μF capacitor, phasel: 44% tilt, 1.6‐ms extension and phase 2: 2.5‐ms fixed duration) was delivered from the RV → Can ± AS. The four configurations were randomized and DFTs (PS + AS) assessed using a modified binary search. Ventricular fibrillation (VF) was induced with 60 Hz AC followed 10 seconds later by the test shock. The DFTs were compared using repeated measures analysis of variance (ANOVA). All configurations incorporating AS produced significant (P < 0.05) reduction in the DFT compared to no AS (13.8 ± 7.4 J). There was no difference in the efficacy of differing pulse widths (P > 0.05); 3 ms (11.0 ± 5.4 J), 5 ms (11.5 ± 6.0), and 7 ms (10.6 ± 5.3 J). In conclusion, delivering an AS from a transvenous lead system deployed in the MCV reduces the DFT by 23% compared to a conventional RV → Can shock alone.
Eccentricities of Dual Chamber Implantable Pacemakers
Authors: BAROLD S. SERGE
Published: June 2006

The consequences of a short 160 ms postventricular atrial refractory period (PVARP) were studied in 27 patients with Medtronic Elite series of pacemakers (programmed to the unipolar mode) by using chest wall stimulation and myopotential interference. Because the ventricular refractory period is nonprogrammable at 230 ms, appropriately timed signals produced As‐Vr combinations where As is an atrial sensed event and Vr is a ventricular event detected in the ventricular refractory period. The As‐Vr combination inhibited the release of the atrial stimulus at the completion of the atrial escape interval in the DDI, DDIR, DDD, and DDDR modes. A paced ventricular beat (Vp) was documented to initiate automatic PVARP extension in circumstances where Vp was preceded by a Vr event and the pacemaker interpreted the Vr‐Vp sequence as 2 ventricular events without an intervening atrial event and Vp as a ventricular premature beat. Knowledge of these eccentricities should facilitate the interpretation of complex pacemakers responses to interference.
Prenatal Diagnosis of QT Prolongation by Magnetocardiography
Authors: MENÉNDEZ THERESA , ACHENBACH STEPHAN , BEINDER ERNST , HOFBECK MICHAEL , SCHMID OLIVER , SINGER HELMUT , MOSHAGE WERNER , DANIEL WERNER G.
Published: June 2006

Magnetocardiogrciphy constitutes a new tool for monitoring fetal cardiac activity. The fetal magnetocardiogram (FMCG) recorded noninvasively over the maternal abdomen is detectable with high temporal resolution and permits analysis of all parts of the PQRST waveform. In this way measurements of cardiac time intervals, including the QT interval, become possible. The following article constitutes the first report of antenatal detection of QT prolongation in two fetuses by FMCG.
Reversible Cardiomyopathy After Radiofrequency Ablation of Lateral Free‐Wall Pathway‐Mediated Incessant Supraventricular Tachycardia
Authors: WU EUGENE B. , GHIA HENDRICK M.Y. , GILL JASWINDER S.
Published: June 2006

Incessant supraventricular tachycardia leading to reversible Cardiomyopathy has been reported. Cardiomyopathy usually only develops after prolonged episodes of tachycardia at a significant heart rate. Left ventricular free‐wall pathways rarely cause fast and incessant tachycardia. Therefore Cardiomyopathy has not been reported with left ventricular free‐wall pathway‐mediated supraventricular tachycardia. We report on two cases of left ventricular free‐wall‐mediated supraventricular tachycardia leading to reversible Cardiomyopathy after radiofrequency ablation. These cases illustrate the difficulty in diagnosing tachycardia‐mediated Cardiomyopathy, as the tachycardia may be clinically silent. In addition, they emphasize the importance of making this diagnosis, as the Cardiomyopathy is reversible.
Placement of a Defibrillation Lead in the Left Subclavian Vein from the Right Cephalic Vein
Authors: SHALABY ALAA A. , DEMERS PAUI A. , SAGER PHILIP T. , BERSOHN MALCOLM M.
Published: June 2006

This case report highlights the feasibility and stability of transvenous placement of a second defibrillation lead in the left subclavian vein from a right cephalic vein approach. This was undertaken in a right‐sided implant of an active can cardioverter defibrillator to lower defibrillation thresholds that would have otherwise precluded implant.
The Importance of Ventricular Septal Morphology in the Effectiveness of Dual Chamber Pacing in Hypertrophic Obstructive Cardiomyopathy
Authors: DIMITROW PAWŁ PETKOW , GRODECKI JANUSZ , BACIOR BOGUMIŁA , DUDEK DARIUSZ , LEGUTKO JACEK , JASZCZ KALINA KAWECKA , DUBIEL JACEK S.
Published: June 2006

It has been reported that older patients with hypertrophic obstructive Cardiomyopathy (HOCM) benefited the most from dual chamber (DDD) pacing. Since in older patients the distribution of septal hypertrophy and left ventricular (LV) cavity shape differs from that in younger patients, we decided to study the efficacy of DDD pacing on the reduction of LV outflow tract (LVOT) gradient in different patterns of septal hypertrophy. We compared HOCM patients with nonreversed septal curvature, thus preserving the elliptical LV cavity contour (common in the elderly), (group I) versus patients with reversed septal curvature, deforming the LV cavity to a crescent shape (common in the young), (group II). Eighteen HOCM patients were studied (11 patients in group I and 7 patients in group II). After implantation of a DDD pacemaker, the LVOT gradient was measured using Doppler echocardiography at various programmed AV delay intervals to determine the maximal percentage decrease of LVOT gradient from baseline. The measurement was repeated after at least a 6‐month follow‐up (chronic DDD pacing). The baseline LVOT gradient was comparable between groups (79 ± 28 vs 81 ± 25 mmHg, P = 0.92). The LVOT gradient reduction at acute DDD pacing was significantly greater in group I than group II (61 ± 18% vs 23 ± 10%, P = 0.0001). This difference in favor of the patients from group I was maintained at midterm follow‐up (69 ± 17% vs 40 ± 17% P = 0.0076). In conclusion, patients with normal septal curvature and preserved elliptical LV cavity shape had a greater reduction of LVOT gradient after DDD pacing than patients with reversed septal curvature deforming LV cavity. The proposed criterion assessing the septal curvature may be useful to predict the efficacy of DDD pacing in the reduction of LVOT gradient.
Signal Averaging in Wolff‐Parkinson‐White Syndrome: Evidence That Fractionated Activation Is Not Necessary for Body Surface High Frequency Potentials
Authors: SMITH WILLIAM M. , VIDAILLET HUMBERTO J. , WORLEY SETH J. , POLLARD JEFFREY K. , GERMAN LAWRENCE D. , MORTARA DAVID W. , IDEKER RAYMOND E.
Published: June 2006

It is commonly assumed that the presence of high frequency components in body surface potentials implies that fractionated activation fronts, caused by heterogeneously viable tissue, are present in the heart. However, it is possible that non‐fractionated activation fronts can also give rise to high frequency surface potentials and that the relative amount of high frequency power is related to the complexity of the activation sequence. In a test of this idea, averaged body surface potentials were recorded during the entire QRS complex of nine Wolff‐Parkinson‐White (WPW) patients in situations in which fractionated activation fronts should not have been present, but which represent increasing degrees of complexity of ventricular activation: (1) postoperative entopic pacing from subepicardial wires placed during surgery, when a single coherent activation front was present throughout most of the QRS; (2) Preoperative preexisted rhythm, when a single coherent activation front was present for one portion of the QRS (the delta wave); and (3) postoperative normal rhythm, when two or more activation fronts were present in the ventricles throughout most of the QRS. For comparison, averaged body surface potentials were also analyzed during the last 40 ms of the QRS complex and the ST segment of 14 postinfarction patients with chronic ventricular tachycardia. In the patients with WPW syndrome, relatively high frequency content increased (attenuation ‐36.7 vs ‐27.2 vs 18.3 dB) and QRS width decreased (160.7 vs 125.9 vs 94.1 ms) significantly from paced to preoperative to postoperative beats. Significant high frequency content was present in all cases, showing that coherent activation fronts can give rise to high frequencies. Interestingly, the postoperative QRS of WPW patients contained a larger proportion of high frequency power than did the late potentials of the patients with ventricular tachycardia. Thus, while the presence of late fractionated body surface potentials may be a marker for ventricular tachycardia, these potentials by themselves do not necessarily signify that the underlying cardiac activation giving rise to these signals is fractionated.
Morphology Discriminator Feature for Enhanced Ventricular Tachycardia Discrimination in Implantable Cardioverter Defibrillators
Authors: DURU FIRAT , BAUERSFELD URS , RAHN‐SCHÖNBECK MARIETTE , CANDINAS RETO
Published: June 2006

The Morphology Discriminator (MD) feature is an elec‐trogram template matching algorithm that intends to improve tachycardia discrimination in implantable Cardioverter defibrillators (ICDs). The aim of this study was to evaluate the performance of this feature during spontaneously occurring ventricular and supraventricular tachyarrhythmias and exercise induced sinus tachycardia. Twenty‐three patients (20 men, 3 women; mean age 54.3 ± 13.8 years) with pectorally implanted Ventritex Contour MD, Angstrom MD, and Profile MD ICDs were studied. The stability of the acquired morphology template and performance of the algorithm during spontaneous tachyarrhythmias were evaluated at follow‐up. A treadmill exercise test was performed in 16 patients along with continuous telemetric monitoring of matching scores. A satisfactory template could be acquired at baseline in 22 (96%) patients. Variations in electrogram morphology necessitated new template acquisition in seven (30%) patients at first follow‐up (6–8 weeks postimplant). During a mean follow‐up of 9.1 ± 3.7 months, 56 ventricular tachycardia (VT) and 15 supraventricular tachycardia episodes (sinus tachycardia in two‐thirds) in 11 patients were all appropriately discriminated by the MD feature. Exercise testing showed appropriate, discrimination of sinus tachycardia in 15 (94%) of 16 patients. A common observation was post‐shock changes in electrogram morphology that resulted in transient mismatch with the template. In conclusion, the recently introduced MD feature in ICDs has a high sensitivity for detection of VT and high specificity for rejection of sinus tachycardia. Postshock changes in electrogram morphology have been observed that may cause inappropriate redetection. Marked variations of electrogram morphology over time may be a concern in some patients, especially during lead maturation.