bluuebunny/crossref_metadata_2025 huggingface dataset:
A Gastroesophageal Electrode for Atrial and Ventricular Pacing
Authors: MCENEANEY DAVID J. , COCHRANE DAVID J. , ANDERSON J.A. , ADGEY A.A. JENNIFER
Published: July 2006

Temporary transvenous cardiac pacing requires technical expertise and access to fluoroscopy. We have developed a gastroesophageal electrode capable of atrial and ventricular pacing. The flexible polythene gastroesophageal electrode is passed into the stomach under light sedation. Five ring electrodes, now positioned in the lower esophagus, are used for atrial pacing. A point source (cathode) on the distal tip of the electrode, now positioned in the gastric fundus. is used for ventricular pacing. Two configurations of atrial and ventricular pacing were compared: unipolar and bipolar. During unipolar ventricular pacing the indifferent electrode (anode) was a high impedance chest pad. For bipolar ventricular pacing the indifferent electrode was a ring electrode placed 2 cm proximal to the tip. Unipolar atrial pacing was performed with 1 of 5 proximal ring electrodes acting as cathode (“cathodic”) or as anode (“anodic”) in conjunction with a chest pad. Bipolar atrial pacing was performed using combinations of 2 of 5 ring electrodes. Atrial capture was obtained in all 55 subjects attempted. When all electrode combinations were compared, atrial capture was significantly more frequent using the bipolar approach (153/210 bipolar, 65/210 unipolar; t = 7.37, P < 0.001). For unipolar atrial pacing, cathodic stimulation (from esophagus) was more successful than anodic stimulation (cathodic 62/105, anodic 20/105; t = 5.81, P < 0.001). In 43 subjects attempted unipolar ventricular pacing resulted in a higher frequency of capture than the bipolar approach (unipolar 41/43 (95.3%), bipolar 19/43 (44.2%); P < 0.001). In conclusion, atrial pacing was optimal using pairs of ring electrodes (“bipolar”) while ventricular pacing was optimal using the distal electrode tip (cathode) in conjunction with a chest pad electrode (“unipolar”). This gastroesophageal electrode may be useful in the emergency management of acute bradyarrhythmias and for elective electrophysiological studies.
Magnetic Resonance Imaging and Signal‐Averaged Electrocardiography in Patients with Repetitive Monomorphic Ventricular Tachycardia and Otherwise Normal Electrocardiogram
Authors: GRIMM WOLFRAM , WIG ELISABETH LIST‐HELL , HOFFMANN JÜRGEN , MENZ VOLKER , HAHN‐RINN ROLAND , KLOSE KLAUS J. , MAISCH BERNHARD
Published: July 2006

Early or localized forms of arrhythmogenic right ventricular dysplasia (ARVD) have been proposed as the arrhythmogenic substrate of repetitive monomorphic ventricular tachycardia (RMVT) originating in the right ventricular outflow tract in patients without any underlying cardiac abnormality on clinical examination and echocardiography. To further examine this hypothesis, magnetic resonance imaging (MRI) and signal‐averaged electrocardiography (SAECG) were performed on 23 patients with RMVT and normal 12‐lead standard ECG of conducted sinus beats. MRI was performed using ECG‐gated turbo spin‐echo images of the heart in order to detect signs of early or localized forms of ARVD, such as localized wall thickness reductions, signal intensity increase indicating adipose tissue infiltrates, and regional bulgings or aneurysms. MRI was normal in 22 (96%) of 23 study patients. In the remaining patient (4%), MRI demonstrated signal intensity increase in the intraventricular septum but not in the right ventricular outflow tract. Time‐domain analysis of the SAECG was normal in 21 (91 %) of 23 patients and revealed ventricular late potentials in 2 study patients (9%). Frequency‐domain analysis of the SAECG was normal in 22 (96%) of 23 patients and revealed ventricular late potentials in one study patient (4 %). We conclude that normal MRI findings of the heart and absence of ventricular late potentials in the SAECC in most patients with RMVT and otherwise normal ECG do not support the hypothesis that early or localized forms of ARVD create the arrhythmogenic substrate in the majority of these patients.
Acute Radiation Dermatitis Following Radiofrequency Catheter Ablation of Atrioventricular Nodal Reentrant Tachycardia
Authors: ROSENTHAL LAWRENCE S. , BECK. THOMAS J. , WILLIAMS JERRY , MAHESH MAHADEVAPPA , HERMAN MICHAEL G. , DINERMAN JAY L. , CALKINS HUCH , LAWRENCE JOHN H.
Published: July 2006

Radiation exposure during fluoroscopic imaging poses potential risks to patients and physicians, especially during protracted cardiovascular or radiological interventional procedures. We describe a woman with refractory paroxysmal supraventricular tachycardia who underwent radiofrequency catheter ablation of the slow pathway involved in atrioventricular nodal reentrant tachycardia. The patient subsequently returned 4 weeks later with acute radiation dermatitis that was retrospectively attributed to a malfunction in the fluoroscopy unit that lacked a maximum current output cut‐off switch. Using dose reconstruction studies and her estimated biological response, we determined that she received between 15 and 20 Gy (1 Gy = 100 rods) to the skin on her back during the procedure. The exposure will result in an increase in her lifelong risk of skin and lung cancer. This article underscores the potential for radiation‐induced injury during lengthy therapeutic procedures using x‐ray equipment.
Can Catheter Ablation in Cardiac Arrest Survivors Prevent Ventricular Fibrillation Recurrence?
Authors: REEK SVEN , KLEIN HELMUT U. , IDEKER RAYMOND E.
Published: July 2006

Ventricular tachyarrhythmias are the most common cause for sudden cardiac death. The success of catheter ablation for supraventricular tachycardias led to the supposition that ablation could also be used in the treatment of ventricular tachycardias. Despite the promising results in bundle branch reentry and some forms of idiopathic ventricular tachycardia, the success rate in patients with coronary artery disease is still low. There is hope that new approaches to reliably localize the critical region of the tachycardia and new ablation techniques to create larger areas of injury may lead to a wider application of ablation therapy in the treatment of ventricular tachycardia. Survivors of cardiac arrest typically have more rapid and unstable arrhythmias than patients with sustained ventricular tachycardia, and these rapid arrhythmias frequently degenerate into ventricular fibrillation. The instability of the arrhythmia makes it impossible to localize the arrhythmia origin with current mapping techniques. Experimental and clinical data, however, suggest that these arrhythmias also frequently start from a localized area of electrical activation. With developments in mapping techniques and energy delivery, catheter ablation may soon become a feasible therapeutic approach in some patients with unstable arrhythmias. The article discusses the prerequisites for this approach and suggests the patients who may be appropriate candidates for this technique.
Right Atrial Separation Procedure for Eliminating Chronic Atrial Fibrillation Associated with Atrial Septal Defect
Authors: SUEDA TAIJIRO , NAGATA HIDEYUKI , OKADA KENJI , HIRAI SHINJI , MORITA SATORU , ORIHASHI KAZUMASA , MATSUURA YUICHIRO
Published: July 2006

Chronic atrial fibrillation (AF) had been documented in a patient with atrial septal defect for 7 years. A right atrial separation procedure was performed for ablation of chronic AF, concomitant with repair of the atrial septal defect, and followed by atrial electrophysiological mapping. A horizontal transectional incision extending to the borders of the atrial septum and the tricuspid annulus was made. Cryolesions of the atrial isthmus between the margin of the upper incision and the tricuspid valve annulus were created at ‐60†C for 2 minutes at a time. After the operation, the patient had restored normal sinus rhythm during a subsequent follow‐up period of 48 months.
Chronic Left Main Coronary Artery Occlusion: A Complication of Radiofrequency Ablation of Idiopathic Left Ventricular Tachycardia
Authors: PONS MAXIME , BECK LIONEL , LECLERCQ FLORENCE , FERRIERE MARC , ALBAT BERNARD , DAVY JEAN‐MARC
Published: July 2006

We describe in this report the development of chronic left main coronary artery (LMCA) occlusion in a young patient 2 years after an uncomplicated, successful ablation of idiophic left ventricular tachycardia. This complication appears to be a late consequence of trauma to the LMCA during the procedure rather than an acute or subacute embolic event.
Right Atrial Appendage to Right Ventricle Accessory Atrioventricular Connection: A Case Report
Authors: MILSTEIN SIMÓN , DUNNIGAN ANN , TANG CHUEN , PINEDA EDGAR
Published: July 2006

Atrial and ventricular attachments of accessory atrioventricular connections have classically been localized to adjacent atrial and ventricular tissues, and this principle is responsible for the widespread success of radiofrequency catheter ablation. We present anatomical evidence of an unusually located accessory atrioventricular connection, which bridged the atrioventricular ring epicardially, directly from the base of the right atrial appendage to the right ventricle. This observation might offer a new insight into unusual accessory atrioventricular connection locations and may explain why some endocardial radiofrequency catheter ablation procedures might fail.
Risk Factors for Venous Obstruction in Children with Transvenous Pacing Leads
Authors: FIGA FELICIA H. , MCCRINDLE BRIAN W. , BIGRAS JEAN‐LUC , HAMILTON ROBERT M. , GOW ROBERT M.
Published: July 2006

To determine tbe incidence and risk factors for venous obstruction in children with transvenous pacing leads, 63 children were evaluated clinically and echocardiographically. Patients with abnormal clinical and/or echocardiographic findings were further investigated by venography. Thirteen patients (21%) had evidence of venous obstruction. Venography in 11 (2 refused) showed that severity of obstruction (as defined by percentage of luminal narrowing) was complete (100%) in 3, severe (> 90%) in 4. and moderate (60%‐90%) in 5 (1 patient having 2 sites of obstruction). Risk factors for obstruction in 55 patients with single implantation procedures (10 with ohstruction: 18%) were sought. Total cross‐sectional area of lead(s) was indexed to body surface area at implantation (INDEX). Patients with obstruction had a higher mean INDEX (7.6 ± 1.6 mm2/m2) than patients without obstruction (4.9 ± 2.0 mm2/m2); P < 0.0002). Receiver‐operator characteristic curves showed an INDEX > 6.6 mm2/m2 to best predict obstruction, with a sensitivity of 90% and specificity of 84%. Since pacingis lifelong, sizing of transvenous leads to the child is important to prevent obstruction and preserve venous access.
Right Side Implant of the Unipolar Single Lead Defihrillation System
Authors: NATALE ANDREA , SRA JASBIR , GEIGER MARY JANE , NEWBY KEITH , AKHTAR MASOOD , PACIFICO ANTONIO
Published: July 2006

The active can defibrillator has been designed for implantation in the left prepectoral region. Whether this system can be successfully implanted on the right side is unknown. We describe six cases in which placement of the unipolar single lead defibrillation system was successfully attempted in the right prepectoral region due to impediments on the left side. The mean age of the patients was 62 ± 12 years. Five patients had is–chemic heart disease and one idiopathic dilated cardiomyopathy. The endocardial defibrillation electrode was placed in the right ventricle through the right subclavian vein and positioned at the apex in two patients and in the septal position in four patients. Defibrillation threshold testing was performed using a step‐up/step‐down protocol beginning at 12 J with 3‐J increments or decrements. Defibrillation threshold was defined as the lowest energy of the first shock able to terminate ventricular fibrillation. The generator models used were the Medtronic 7218C in 1 patient, the Medtronic 7219C in 3 patients, and the Ventritex Cadet 115 AC in 2 patients. The mean defibrillation threshold was 15 ± 3 J. The defibrillation thresholds were retested at 1,3, and 6 months, and showed no significant change in five patients but decreased from 15 J to 12 J in one patient. The presence of impediments on the left side should not preclude attempts to place the unipolar active can system in the right prepectoral region.
Correlation of the Heart Rate‐Minute Ventilation Relationship with Clinical Data: Relevance to Rate‐Adaptive Pacing
Authors: SOUCIE LUC P. , CAREY CLARE , WOODEND A. KIRSTEN , TANG ANTHONY S.L.
Published: July 2006

The heart rate (HR)‐minute ventilation (VE) relationship has been shown to be nonlinear and can be expressed as two distinct straight lines. This study is to assess the correlation of the initial HR‐VE slope to clinical parameters. Maximum treadmill exercise tests were performed in 100 healthy volunteers (age 19–77 years) using a ramp protocol in which work‐rate increases linearly with exercise. Breath‐by‐breath VO2, VCO2, and VE were measured, and HR and RP were monitored throughout the exercise. The HR‐VE curve demonstrated nonlinearity with a breakpoint determined by a change point analysis. This breakpoint was significantly higher than that of the anaerobic threshold. The VEat the HB‐VE breakpoint was 56.4 ± 19.4 and VE at the VE‐VO2 and VCO2‐VO2 breakpoints were 48.0 ± 18.3 (P < 0.0001) arid 40.1 ± 16.5 (P < 0.0001). respectively. TheHR at this HR‐VE breakpoint was 77.7 ± 12.9% of the HR range. The first slope. Si (1.76 ± 0.64) was steeper than the second slope, S2 (0.66 ± 0.39). Although there was a gender difference for S1, the best clinical predictor on a stepwise multiple regression analysis was body surface area (BSA) which explained 47% of the variance. It was concluded that nonlinearity of the HR‐VE curve can be expressed as two straight lines. The breakpoint is beyond the anaerobic threshold and can be estimated to be approximately 75% of the maximal predicted HR. RSA is the only clinical parameter that significantly predicts the initial slope of the HR‐VE curve. This can be of great importance in the programming of rate‐adaptive pacemakers using a VE.
Safety of High Energy Internal Cardioversion for Atrial Fibrillation
Authors: MANSOURATI JACQUES , LARLET JEAN‐MARIE , SALAUN GILLES , MAHEU BENOIT , BLANC JEAN‐JACQUES
Published: July 2006

High energy internal cardioversion has been proposed as an alternative method to cardiovert drug refractory or external cardioversion refractory atrial fibrillation. However, the safety of this technique has not been clearly evaluated. We reviewed findings in 53 patients who underwent 55 sessions of high energy internal cardioversion (2 patients underwent 2 sessions] for termination of longstanding atrial fibrillation. Shocks energy varied from 70–270 J. Three patients had 3 shocks during the same session, 5 had 2, and 47 only 1. Success rate was 89% (success was defined as immediate conversion to normal sinus rhythm).

Low cardiac output occurred in two patients, and resulted in the death of one of these individuals, a patient with significant hypertrophic cardiomyopathy and heart failure. The other patient recovered completely. In 11% of the cases, shock induced transient atrioventricular block, necessitating ventricular pacing until sinus rhythm was restored. In three patients, a moderate but asymptomatic and uncomplicated pericardial effusion was diagnosed on echocardiogram. Finally, four patients had side effects related to venous puncture, which resolved spontaneously. These results suggest that high energy internal cardioversion is effective for conversion of atrial fibrillation. However, the technique may not be optimal in patients with advanced hypertrophic cardiomyopathy and in such cases the technique should be used carefully and only in the case of failure of external cardioversion; no more than two shocks should be delivered during the same procedure. Temporary ventricular pacing should be provided in all patients and an echocardiogram should be performed before patients are being discharged.
Derivation of a Defibrillator Implant Criterion Based on Probability of Successful Defibrillation
Authors: DEGROOT PAUL J. , CHURCH TIMOTHY R. , MEHRA RAHUL , MARTINSON MELISSA S. , SCHABER DANIEL E.
Published: July 2006

Common criteria for implant of a cordioverter defibrillator include verification of a 2:1 energy safety margin or a fixed safety margin of 10 joules. These criteria have been established empirically. We present a statistical model based on defibrillation efficacy curves which may be used to establish a criterion which would meet a predetermined target. As an example, an implant criterion is derived based on a goal of 1–year sudden cardiac death survival of at least 99% by selecting an expected first–shock efficacy to meet that target. Logistic regression was performed on data from over 1,500 defibrillator implants including successful epicardial and transvenous electrode system implants as well as data from unsuccessful implants. A random sample from these curves was used to generate a representative sample of 1,000 potential implant candidates, By assuming successful defibrillation using a series of shocks at specified energies, i.e., choosing an implant criterion, the probability of successful defibrillation of the patient by a single shock at a predetermined maximum output can be established. Independent data are used to validate the model's accuracy in predicting defibrillation efficacy within the derived example.
Characterization of the Factors that Determine the Effect of Sympathetic Stimulation on Heart Rate Variability
Authors: KIM YOU‐HO , AHMED MIRZA W. , KADISH ALAN H. , GOLDBERGER JEFFREY J.
Published: July 2006

Heart rate variability analysis has been used to derive indices of sympathetic tone. As different sympathetic stimuli may give rise to divergent changes in heart rate variability, this study was designed to characterize the factors responsible for these divergent responses. Twelve healthy subjects (7 males, age 24.8 ±3.1 years) were evaluated. Five‐minute electrocardiographic recordings were obtained at baseline, following upright tilt, and during isoproterenol infusion (25 ng/kg per min) under control conditions and following parasympathetic blockade. Data were acquired during spontaneous respiration and when breathing was timed with a metronome (15 breaths/min). Under control conditions, both upright tilt and isoproterenol infusion resulted in significant decreases in the SD and MSSD from baseline values of 69 ± 3 ms and 64 ± 5 ms to 48 ± 4 ms and 21 ± 5 ms during tilt and 44 ± 4 ms and 20 ± 5 ms during isoproterenol infusion, respectively. LF power also significantly increased from 0.47 ±0.17 In (beats/min)2 at baseline to 1.90 ± 0.20. In (beats/min)2 and 1.34 ± 0.18. In (beats/min)2 during tilt and isoproterenoi infusion, respectively. No change in HF power was noted. Following parasympathetic blockade, all heart rate variability parameters were significantly decreased. No significant change from baseline in the SD, MSSD, or HF power was noted with either tilt or isoproterenol infusion. The LF power increased only with tilt from a baseline value of ‐3.17 ± 0.17 in (beats/min)2 to ‐0.41 ± 0.19 in (beats/min)2. Similar changes were noted during spontaneous respiration and metronome breathing. These findings demonstrate that the response of the sinus node to β–adrenergic stimulation depends on the mode of stimulation. In addition, the associated level of parasympathetic tone affects the observed changes in heart rate variability that are associated with sympathetic stimulation.
Probability Density Function Revisited: Improved Discrimination of VF Using a Cycle Length Corrected PDF
Authors: POLIKAITIS AUDRIUS , ARZBAECHER ROBERT , BUMP THOMAS , WILBER DAVID
Published: July 2006

The probability density function (PDF) describes the fraction of time an electrogram signal spends at the baseline, In normal rhythm the signal is at baseline during the period between electrogram complexes, while in fibrillation the signal exhibits continuous activity and spends little time at baseline. However, time spent at the baseline is dependent on the rate of the rhythm, which limits the ability of the PDF algorithm to discriminate ventricular fibrillation from fast nonfibrillatory rhythms. A cycle length corrected version of the PDF algorithm has been formulated, which only examines the electrical activity between detected beats. The algorithm was developed utilizing a training set of 77 endocardial recordings and tested utilizing a test set of 90 endocardial and 56 epicardial recordings. Ventricular fibrillation was detected with 100% sensitivity and 98% specificity.
Local Repolarization Abnormalities Induced by Transcatheter Radiofrequency Ablation in Pigs
Authors: CINCA JUAN , TAPIAS ALFONS , CARREÑO ANA , WARREN MARK , MONT LLUÍS , ANADOMINGO PERE BLANCH , SOLER‐SOLER J.
Published: July 2006

Radiofrequency (RF) ablation alters action potential repolarization of myocardial cells and, theoretically, tbis should induce ST‐T segment changes in the ECG. Since these ECG abnormalities have been rarely reported in patients submitted to RF ablation we assess the ability of the procedure to caase ST‐T segment changes in local electrograms. Epicardial ECG mapping was performed in 17 anesthetized open chest pigs submitted to endocardial (n = 9) or to epicardial (n = 8) unipolar radiofrequency ablation (500 kHz, 20 W for 5‐10 s). To characterize the cellular electrophysiological alterations induced by RE ablation transmembrane action potentials were recorded at various distances from the ablation lesion; these were compared with seven control pigs. Endocardial RE ablation induced a transient (< 5 min) change of 6.1 ± 2.4 m V in T wave amplitude (baseline: 12.8 ± 5.6 mV, P < O.OOl) in 141 out of 269 epicardial electrodes. T wave changes were associated with shortening in local activation time (20.1 ± 2.3 ms at baseline vs 18.5 ± 2.5 ms at 60 s after ablation, P = 0.03). RE current caused persistent ST segment elevation at the center of the ablation lesion with no transmural expansion. Intracellular potentials along a 2‐6‐mm wide myocardial band bordering the RE lesion showed lower amplitude (101 ± 7.0 mV vs 71 ± 23 mV, P < 0.01) and shorter duration (254 ± 44 ms vs 156 ± 29 ms, P < 0.01) than control hearts. The center of the ablation lesion was electrically anexcitable. We concluded that RF ablation alters cellular electrophysiology in small areas surrounding the ablation lesion and this causes short‐lasting transmural changes in T wave amplitude and nontransmural ST segment elevation.
Use of Single Lead VDD Pacing in Children
Authors: SEIDEN HOWARD S. , CAMUÑAS JORGE L. , FISHBURGER STEVEN B. , GOLINKO RICHARD J. , STEINBERG L. GARY , SHAGONG UNSOON , ROSSI ANTHONY F.
Published: July 2006

The development of transvenous ventricular pacing leads with proximal electrodes capable of atrial sensing and the recent availability of smaller generators has created the opportunity to treat children with complete AV block and normal sinus node function with a transvenous single lead VDD pacing system. Studies in adults have demonstrated this system to be efficacious with low complication rates. Transvenous single lead VDD pacemakers were implanted in ten children, aged 5–15 years, between December 1993 and April 1996, in our institution. The indications were complete AV block with severe bradycardia in 5 patients, second‐degree or complete A V block following congenital heart surgery in 3, complete A V block with long QT syndrome in 1, and second‐degree AV block and syncope in 1. There were no complications related to the procedure in any case. P and R wave amplitudes were measured and thresholds were determined intraoperatively on all patients. Amplitudes and thresholds were remeasured on seven patients with a mean follow‐up of 17 months; Holter monitors were performed on seven patients with a mean follow‐up of 16 months. P and H wave amplitudes were generally diminished at follow‐up compared to initial values but remained within an acceptable range for all patients. Four patients required reprogramming after pacemaker insertion, 1 received an atrial lead for dual chamber pacing, 1 required repositioning for lead dislodgment. and 1 patient required a new lead for an inadequate ventricular pacing threshold. No patient had evidence of failure to sense or capture as evaluated by Halter monitoring at last follow‐up. Single lead VDD pacing systems can be successfully used in properly selected children with high degree or complete AV block with normal sinus node function.
Single Pass VDD Pacing in Children and Adolescents
Authors: ROSENTHAL ERIC , BOSTOCK JULIAN , QURESHI SHAKEEL A. , BAKER EDWARD J. , TYNAN MICHAEL
Published: July 2006

Use of a single pass lead for VDD pacing in complete heart block is well described in adults, but there are only brief reports of its use in children. We have used standard adult size single pass leads in 13 children and adolescents aged 3.7–17.2 years (mean 10.1 years) and weighing 13.5–76 kg (mean 34.8 kg). Congenital complete heart block was present in 7 patients, surgical complete heart block in 5 patients and 2:1 AV block of unknown cause in 1 patient. In four patients, the VDD system was their first pacing system. In nine of the patients, 1–6 previous systems had been used and simultaneous extraction of ventricular leads and/or atrial leads was performed. Leads of four different types were used: Brilliant IMPl5Q, Brilliant + IMR15Q, CapSure 5032, and Unipass 425–13 with 4 different generators: Saphir 600, SaphirII620, Thera VDD 8948, and Unity 292–07. At implantation, via a subclavian vein puncture, excess lead was advanced into the right atrium to allow both atrial sensing and slack for further growth. Ventricular thresholds ranged from 0.2–0.7 V. The minimal atrial amplitude was 0.7–4 mV and the maximum amplitude was 2.5–8 mV. There were no complications. Ail patients have maintained adequate atrial signals for reliable pacing with follow up of 3–36 months (mean 17.6 months) during which time some have undergone considerable growth. Beliable atrial synchronous ventricular pacing is possible in growing children with complete heart block using a standard adult single pass lead.
Comparative Left Ventricular Function Following Atrial, Septal, and Apical Single Chamber Heart Pacing in the Young
Authors: KARPAWICH PETER P. , MITAL SEEMA
Published: July 2006

Ventricular pacing, typically initiated from a RV apical electrode, inherently causes abnormal biventricular activation, decreases LV function, and causes histopathological changes. Since pacing initiated in childhood can he expected to have a more protracted course compared with the adult, the consequences of this alteration in LV hemodynamics gain added significance among the young pacemaker recipient. The purpose of this study was to evaluate the potential of improving paced LV function by a septal electrode implant site. Acute alterations in cardiac index, LV pressure, and contraction indices, including dP/dt, Vmax. and Vpm, were compared among 22 patients (median age 10 years) with normal cardiac anatomy during intracardiac electrophysiological studies. LV hemodynamics were measured during intrinsic rhythms and following 15 minutes of atrial, HV apical, and septal pacing at an appropriate exercise rate for age of 150 ppm. Results showed a significant decrease in LV dP/dt, Vmax, and Vpm, and increase in LV end‐diastolic pressure only with apical pacing. Septal pacing, in spite of loss of any atrial contribution to ventricular filling, maintained comparable indices with intrinsic and atrial paced rhythms. This study demonstrates that normalized LV function is maintained by septal and deteriorates with apical pacing acutely among young, nonischemic hearts. Continued evaluation of appropriate pacing electrode designs to permit septal implant is needed to ensure optimal chronically paced LV function.
Atrial Fibrillation: Maintaining Stability of Sinus Rbythm or Ventricular Rate Control? The Need for Prospective Data: The PIAF Trial
Authors: HOHNLOSER STEFAN H. , KUCK KARL‐HEINZ
Published: July 2006

Atrial fibrillation is one of the most commonly encountered clinical arrhythmias. Different treatment options for this rhythm disorder exist with the electrical and/or pharmacological cardioversion to sinus rhythm with subsequent antiarrhythmic drug therapy to prevent recurrences being one of the primary therapeutic goals. Another alternative, however, is represented by the control of the ventricular rate in patients with persistent atrial fibrillation. The question of which of these two strategies should be preferred in the majority of patients with atrial fibrillation has not been studied in a prospective way. Given the background of conflicting data with respect to the prognostic impact of atrial fibrillation and of the increasing evidence concerning the risks of antiarrhythmic drug treatment in atrial fibrillation, a prospective multicenter trial has been initiated to compare these two therapeutic alternatives prospectively. Patients will be randomly assigned to cardioversion with subsequent antiarrhythmic drug therapy to prevent recurrent atrial fibrillation or to a therapy aiming exclusively at control of the ventricular rate during persistent atrial fibrillation. All patients will receive anticoagulation by means of warfarin (target INR 2.5‐3.5) to prevent thromboembolic complications. The rationale and the design of the PIAF trial (Pharmacological Intervention in Atrial Fibrillation) are discussed below. The pilot phase of this study has begun patient enrollment in the spring of 1995.
The Paradox in Using Electrically Stimulated Skeletal Muscle to Pump Blood
Authors: GEDDES L.A.
Published: July 2006

For over four decades, various methods have been described for the use of electrically stimulated skeletal muscle to pump blood. To date, there has been no way of predicting the efficacy or long‐term pumping capabilities of these methods. This article reviews the basic physiological properties of skeletal muscle and relates them to the blood pumping task and illustrates the paradox, namely a high preload is needed for a forceful contraction, but a high prolonged preload produces muscle ischemia and early fatigue. However, the high preload is only required just before muscle contraction. Two methods are described to attain the high preload and high muscle capillary blood flow.
Responses of Normal Subjects During 80° Head Upright Tilt Table Testing Witb and Witbout Low Dose Isoproterenol Infusion
Authors: GRIJBB BLAIR P. , KOSINSKI DANIEL , TEMESY‐ARMOS PETER , BREWSTER PAM
Published: July 2006

Head upright tilt table testing has emerged as a standard technique for the evaluation of patients with recurrent unexplained syncope. To determine the specificity of head upright tilt table testing with and without a low dose isoproterenol infusion, the following study wns undertaken. A total of 34 normal volunteers (21 men, 13 women, mean age 32.9 ± 1.7 years) with no history of syncope, presyncope, or vertigo underwent head upright tilt table testing for 45 minutes. A positive test was defined as the production of syncope or presyncope associated with hypotension and bradycardia. If the test wns negative the patient was lowered to the supine position and a low dose isoproterenol infusion started (sufficient to raise the heart rate 20–25% above baseline) and the patient retilted for 20 minutes. Three subjects (8.8%; 95% CI 2, 26; P = 0.23) developed syncope during the test, two during the baseline tilt, and one during isoproterenol infusion. Interestingly, one of these subjects later bad a clinical syncopal episode. We conclude that head up tilt table testing at 80° with or without low level isoproterenol infusion provides an adequate specificity.
Quinine May Trigger Torsades de Pointes During Astemizole Therapy
Authors: MARTIN EMORY S. , ROGALSKI KATHY , BLACK JAMES N.
Published: July 2006

Because of serious cardiovascular events, warnings against concomitant use of certain medications with the use of antihistamine (HismanalR have been published and added to product labeling. Quinine, the optical isomer to quinidine, is included in these warnings. We present the case of a patient with only mild electrolyte disturbances who experienced an episode of torsades de pointes after a single dose of quinine while taking astemizole.
Malfunction of an Active Fixation J‐Shaped Screw‐In Atrial Electrode Lead: A Case Report
Authors: LEE WEN LIENG , KONG CHI WOON , LIN. MIN REN , WANG JIANN JONG , GHAN WAN LEONG , WANG SHIH PU , GHANG MAU SONG
Published: July 2006

Active fixation leads, using active grasping devices, ensure good postoperative lead fixation, long‐term performance, and make possible later lead removal on demand. However, these delicate designs have not been without practical difficulties. We present two cases of fixation stylet fracture during helix extension and retraction maneuver respectively with resultant lead inoperability and abandonment. The fixed leads could be removed by torquing the entire lead counterclockwise.
Pathophysiological Mechanisms Underlying Vasovagal Syncope in Young Subjects
Authors: WIELING WOUTER , SMIT ADRIANUS A.J. , C.E CATHERINE , VAN STEENWIJK DE JONG‐DE VOS , J JOHANNNES , LIESHOUT VAN , KAREMAKER JOHN M.
Published: July 2006

The occurrence of vasovagal fainting is common in young subjects, but the origin of the precipitating hemodynamic mechanisms involved remain a subject of considerable speculation. Vasovagal fainting is not a sudden onset phenomenon, early failure of vascular resistance responses occurs in faint‐prone young subjects. The variability of hemodynamic responses during the actual faint is large, but the main mechanism operative during, is withdrawal of sympathetic outflow to blood vessels in skeletal muscle with impairment of ability to maintain vasomotor tone.
Unexplained Syncope: Clinical Management
Authors: WOLFF GRACE S.
Published: July 2006

The management of unexplained syncope begins with the patient's history and physical examination, which are oriented to help separate benign from serious causes. Malignant etiologies are more likely to occur with exertional syncope. Cardiac causes should be considered, particularly cardiomyopathy, postoperative congenital heart disease, right ventricular dysplasia, anomalous coronary artery, pulmonary artery hypertension, myocarditis, long QT syndrome, and Wolff‐Parkinson‐White syndrome. Neurological and metabolic disorders may underlie a syncope episode. After malignant causes of syncope have been excluded and the diagnosis of neurocardiac syncope has been established, treatment strategies include behavior modification, salt and increased fluids, and pharmacological agents. Efficacious agents include β‐blockers, dysopyramide, fludrocortisones, and alpha agents. Yet, behavior modification alone may be as effective as salt or pharmacological therapy. Because the natural history of neurocardiac syncope in children is spontaneous resolution, it is appropriate to try the simple measures before introducing drug therapy.
Radiofrequency Catheter Ablation of Idiopathic Ventricular Tachycardias in Children
Authors: SMEETS JOEP L.R.M. , RODRIGUEZ LUZ‐MARIA , TIMMERMANS CARL , WELLENS HEIN J.J.
Published: July 2006

We performed radiofrequency catheter ablation of idiopathic ventricular tachycardia in six children. In four, the ventricular tachycardia originated in the left ventricle, in two it originated in the right ventricular outflow tract. In 5/6 (83%) the RF procedure was successful; there were no complications.
Anatomy of the Atrioventricular Junctions with Regard to Ventricular Preexcitation
Authors: ANDERSON ROBERT H. , HO SIEW YEN
Published: July 2006

In the normal heart, the atrioventricular junctions surround the orifices of the mitral and tricus‐pid valves. The septal area of the junctions is much smaller than generally thought, being made up of the fibrous membranous septum and the muscular atrioventricular septum. The left atrioventricular junction gives the potential for muscular atrioventricular contiguities only in relation to the mural leaflet of the mitral valve. The right junction extends from the area posterior to the muscular atrioventricular septum to the supraventricular crest of the right ventricle. Anomalous pathways for conduction, which produce preexcitation, can be found anywhere within these atrioventricular junctions. The pathways usually are the muscular accessory connections responsible for the Wolff‐Parkinson‐White syndrome, which can exist in the left, septa!, or right junctions. Specific muscular connections are found in the presence of Purkinje cell tumors, diverticulums of the coronary sinus, or when taking origin from nodes of Kent at the acute margin of the ventricular mass. The latter connections are responsible for most examples of so‐called Mahaim conduction, and are also described as atriofascicular tracts. The true Muhaim fibers are best described as nodoventricular or fasciculo‐ventricular connections, while the pathway previously labelled as atriofascicular by the European Study Group is now best distinguished as an atrio‐Hisian tract. The slow and fast pathways into the atrioventricular node are composed of ordinary atriai myocardium, the orientation af the fibers probably producing preferential conduction.
Development of the Conduction System of the Heart
Authors: MOORMAN ANTOON F.M. , DE JONG FRITS , LAMERS WOUTER H.
Published: July 2006

The muscle cells forming the myocardium and the muscle cells forming the intestinal smooth muscle layers, are both derived from the visceral mesoderm. All cardiomyocytes display autorhythmicity, intercellular conduction via gap junctions, and contraction, irrespective whether they are derived from atrium, ventricle, node, or bundies. It is the anatomical arrangement of the distinct components that is responsible for the coordinate contraction wave over the heart. These very basic principles have been insufficiently appreciated in most studies on the development of the conduction sytem, by which it got unnoticed that the proper anatomical arrangement is, in essence, layed down very early in development in the cardiac tube. In this review we will summarize recent immunohistochemical studies that have permitted this appreciation.*
Immunological Aspects of Congenital Atrioventricular Block
Authors: SMEENK RUUD J.T.
Published: July 2006

Isolated congenital heart block (CHB) in children is strongly associated with the occurrence of autoantibodies to Ro/SS‐A and La/SS‐B in the circulation of the mother. Although these antibodies are generally found in patients with generalized autoimmune diseases, they may also occur in symptomless mothers of CHB patients. It is thought that anti‐Ro/SS‐A and anti‐La/SS‐B may reach the fetal circulation via transplacental transport, starting around the 20th week of gestation. Although several hypotheses have been put forward, the exact mechanism through which these autoantihodies bind the fetal conduction system and elicit a local inflammatory response is still unclear. Also, the induction of the autoantibody response in the mother remains largely obscure, although a putative role of viral infection has been suggested. In tbis overview, the structure of the involved antigens will be discussed, followed by the nature of the antibodies. Recent data regarding the etiology of the anti‐Ro/SS‐A and anti‐La/SS‐B response and the role of these autoantihodies in the pathogenesis of CHB will he presented.
VDD Pacing in Children with Congenital Complete Heart Block: Advantages of a Single Pass Lead
Authors: ROSENTHAL ERIC , BOSTOCK JULIAN
Published: July 2006

A single pass lead for VDD pacing in complete heart hlock is well descrihed in adults hut there are only brief reports of its use in children. We used standard adult size single pass leads in ten children and adolescents aged 3.7–17.2 years (mean 9.9 years) and weighing 13.5–76 kg (mean 35.4 kg) with congenital complete heart block. One patient had coexisting congenital heart disease and had undergone surgery. A 2:1 atrioventricular hlock in one patient was presumed to he congenital in origin. In four patients, the VDD system was their first pacing system. In six of the patients, 1–4 previous systems had been used and simultaneous extraction of ventricular leads (6) and/or atrial leads (2) was performed. Four different types of lead were used: Brilliant IMP15Q (Vitatron); Brilliant + IMR15Q (Vitatron): Cap‐Sure 5032 (Medtronic); and Unipass 425–13 (Intermedics) witb four different generators: Saphir 600 (Vitatron): Saphir II 620 (Vitatron): Thera VDD 8948 (Medtronic): and Unity 292–07 (Intermedics). All leads were introduced via a suhclavian vein puncture and the atrial dipole was placed low in the right atrium to provide slack for further growth while maintaining atrial sensing. Ventricular thresholds ranged from 0.2–0.8 V. The minimal atrial amplitude was 0.7–4 mV and the maximum amplitude was 2.5–8 mV. There was one early microdisplacement and the lead was repositioned. Over a follow‐up period ranging from 1–39 months (mean 20.4 months), all patients have maintained low ventricular pacing thresholds and adequate atrial signals for reliable pacing at rest and with exercise. During this time some bave undergone considerahle growth. The patient with coexisting congenital heart disease died suddenly at 3 years, hut the pacing system had no fault at autopsy. The standard adult size single pass lead provides a simple means to enable reliahle atrial synchronous ventricular pacing in growing children with complete heart hlock.
Can Intraatrial Reentry Be Prevented by Changes in Surgical Technique?
Authors: EBELS TJARK
Published: July 2006

Intraatrial reentry tachycardias can be prevented by surgical technique. Crucial in prevention is not to create areas of slow conduction. Also, the integrity of the terminal crest appears to be essential for normal impulse propagation; at surgery the crest should preferably be left intact. The number of incisions in the atrium should be kept to an absolute minimum. One single incision is the best. Therefore, it is also better to cannulate the caval veins directly instead of using the right atrial auricle.
Sotalol for Atrial Tachycardias After Surgery for Congenital Heart Disease
Authors: BEAUFORT‐KROL GERTIE CM. , BINK‐BOELKENS MARGREET TH.E
Published: July 2006

Atrial tachycardias, in particular atrial flutter after surgery for congenital heart disease, is associated with a high mortality. Treatment with various antiarrhythmic drugs and/or antitachycardia pacemakers is not very successful. Sotalol, a Class III drug, has shown to be a promising drug in adults with atrial tachycardias. However, the experience with sotalol in children after surgery for congenital heart disease is limited. Therefore, we describe our results here. Between December 1990 and February 1997, 26 children with atrial tachycardias, most of them with atrial flutter or fibrillation (n = 20), after surgery for congenital heart disease were treated with sotalol orally. The age of the children at the start of treatment was 7.5 ± 5.8 years (mean ± SD). The time interval between surgery and the start of atrial tachycardia ranged from 1 day to 14.3 years (3.8 ± 3.8 years). Conversion to sinus rhythm was achieved in 16 out of 22 hemodynamically stable children with a dosage of 4.0 ±1.6 mg/kg per day. The six children without sinus rhythm on sotalol and four hemodynamically unstable patients were treated prophylactically with sotalol after DC cardioversion for their tachycardias. Two children complained of mild transient fatigue. Heart rate decreased during therapy (95 ± 33 vs 81 ± 21 beats/min; P = 0.01). QTc‐intervals did not change. Proarrhythmias such as torsades de pointes were not encountered. Two children with a preexis‐tent sick sinus syndrome showed aggravation of bradycardia and needed pacemaker implantation. The percentage of children with a recurrence‐free interval of 1 and 2 years was 96% and 81 %, respectively, for all atrial tachycardias, and 92% and 66% for atrial flutter. The recurrences of atrial tachycardias during the follow‐up period, which ranged from 0.1‐6.1 years (2.5 ± 1.8 years) could be treated with only an increase of the dosage of sotalol in all but one patient. We conclude that sotalol is an effective drug for the treatment and prevention of atrial tachycardia in children afler surgery for congenital heart disease.
Amiodarone as Treatment for Atriai Tachycardias After Surgery
Authors: VILLAIN ELIZABETH
Published: July 2006

Atriai flutter, including all types of postoperative atrial tachycardias, is the one with the highest risk of late sudden death. Thus, late postoperative atrial tachycardias must be suppressed and all patients should be permanently treated after a first episode of atrial flutter. Daily oral doses of 200‐250 mg/m2 amiodarone were found to be highly effective and well tolerated in young patients. However, in older patients and after long‐term therapy, its use is restricted by adverse side‐effects. In these cases, association of lower doses of antiarrhyth‐mic agents, including amiodarone, may be effective and well tolerated. The use of other therapeutic options such as radiofrequency ablation should also be considered in older patients having drug‐refractory postoperative atrial flutter.
Undersensing of Ventricular Fibrillation in a Noncommitted Nonthoracotomy Cardioverter Defibrillator System
Authors: PERALTA ADELQUI O. , JOHN ROY M. , VENDITTI FERDINAND J. , MARTIN DAVID T.
Published: July 2006

Objective: Evaluation of the impact of undersensing on VF detection time and the relationship of undersensing to the programmed shock energy. Background: Failure to reconfirm an ongoing arrhythmia due to undersensing by a noncommitted ICD might prolong the time to therapy. Methods: We measured initial detection times and redetection times at predischarge and at 2 and 6 months in 29 patients (22 men, mean age 60 years) with a noncommitted nonthoracotomy ICD. Telemetry data and output markers were used to analyze each induction. Results: Undersensing hading to failure to reconfirm was present in 44 (11.1%) of 398 episodes of sustained VF and prolonged significantly the median initial detection time from 2.3 seconds (25th and 75th percentiles: 2 and 2.6 s, respectively) to 5.45 seconds (4.3 and 7.35 s. P < 0.0001). One episode required external defibrillation after reconfirmation failure occurred during charging; the total detection time prior to shock was 46 seconds. In a subset of 87 episodes with failed first shocks, the initial detection time was 2.3 seconds (2.1 and 2.8 s) and the redetection time 3 seconds (2.5 and 4.77 s. P < 0.0001). The presence of undersensing prolonged the redetection from 2.6 seconds (2.35 and 3.1 s) to 5.4 seconds (4.53 and 7.35 s, P < 0.0001). Undersensing was more prevalent during the redetection period (P = 0.004) and in episodes of sustained VF in which the first shock energy was higher than 15 f (19.7% vs 5.8%, P < 0.0001). Conclusions: In this automatic defibriliator system, undersensing occurs in 11% of the sustained VF inductions and prolongs detection time significantly. Redetection is longer than initial detection mostly due to the presence of undersensing, the frequency of which is proportional to the programmed energy. The clinical significance of this finding is unknown.