bluuebunny/crossref_metadata_2025_split huggingface dataset:
Clinical Value of the Postpacing Interval for Mapping of Ventricular Tachycardia in Patients with Prior Myocardial Infarction
Authors: BOGUN FRANK , KNIGHT BRADLEY , GOYAL RAJIVA , STRICKBERGER S. ADAM , HOHNLOSER STEFAN J. , MORADY FRED 
Published: April 2007

Postpacing Interval. Introduction: The postpacing interval (PPI) has been used to discriminate bystander sites from critical sites within a ventricular tachycardia (VT) reentry circuit, with a PPI that is similar to the VT cycle length (CL) being indicative of a site within the reentry circuit. The purpose of this study was to assess the clinical value of the PPI for identifying effective target sites for ablation of VT at sites of concealed entrainment in patients with prior myocardial infarction. Methods and Results: In 24 patients with coronary artery disease and a past history of myocardial infarction, 36 VTs with a mean CL of 483 ± 80 msec (± SD) were mapped and targeted for radiofrequency (RF) ablation. The only criterion used to select target sites for ablation was concealed entrainment. In a post hoc analysis, the PPI was measured at 47ineffective and 26 effective ablation sites. The mean PPI‐VTCL difference at the 26 effective sites(114 ± 137 msec) did not differ significantly from the mean at the 47 ineffective sites (177 ± 161msec; P = 0.1). The sensitivity of a PPI‐VTCL difference ≤ 30 msec for identifying an effective ablation site was 46%, the specificity 64%, the positive predictive value 41%, and the negative predictive value 68%. Conclusion: The PPI‐VTCL difference is not useful for discriminating between sites of concealed entrainment that are within or outside of a VT reentry circuit in patients with prior infarction. Therefore, in patients with prior infarction, the PPI is not clinically useful for identifying sites of concealed entrainment at which RF ablation should or should not beat tempted.
Junctional Tachycardia During Radiofrequency A blation of the Slow Pathway in Patients with AV Nodal Reentrant Tachycardia: Effects of autonomic Blockade
Authors: CHEN MIEN‐CHENG , GUO G. BIH‐FANG 
Published: April 2007

Junctional Tachycardia of AV Nodal Reentrant Tachycardia. Introduction: Theautonomic nervous system richly innervates the peri‐AV nodal region and may be activated during radiofrequency (RF) ablation for AV nodal reentrant tachycardia, resulting in the generation of junctional tachycardia. The purpose of this prospective study was to determine the role of the autonomic nervous system in the genesis of junctional tachycardia. Methods and Results: We compared the characteristics of junctional tachycardia in patients with (n = 10) and without (n = 10) autonomic blockade undergoing RF ablation for AV nodal reentrant tachycardia. Intravenous administration of atropine (0.04 mg/kg) and propranolol (0.2 mg/kg) were used to block the autonomic nervous system. There were no differences in clinical variables and baseline electrophysiologic characteristics between the two groups except for slightly longer effective refractory periods of the fast pathway and of the atrium in the autonomic blockade group. The autonomic blockade shortened the baseline sinus cycle length and effective refractory period of the ventricle only but not other electrophysioiogic characteristics of the AV node. The junctional tachycardia was observed during ablation in each patient, but its occurrence and cycle length, as well as numbers of consecutive junctional beats, were not altered by the autonomic blockade. Conclusion: Our results indicate that the muscarinic and beta‐adrenergic components of the autonomic nervous system play no role in the genesis of junctional tachycardia.
Microwave Ablation of Myocardial Tissue
Authors: THOMAS STUART P. , CLOUT RAY , DEERY CATHERINE , MOHAN ANANDA S. , ROSS DAVID L. 
Published: April 2007

Microwave Ablation of Myocardial Tissue. Introduction: The biophysical properties of microwave electromagnetic radiation suggest that it may be an alternative to radiofrequency (RF) energy for ablation of arrhythmias resistant to treatment using RF ablation. Methods and Results: The aim of this study was to characterize lesions produced using simple element designs in a blood super fused ovine tissue model to simulate endocardial ablation. The effect of tissue bath flow, duration of microwave exposure, and changes in forward power on lesion size were examined using a modified monopole element. Lesion size increased with increasing duration of exposure and increasing forward power (P ≤ 0.05). Lesion depth was 0.7 ± (1.7 mm after 30 seconds and n.5 ± L9 mm after 360 seconds. Lesion depths at 61. 71, and 80 W were 6.4 ± 3.7, 8.9 ±±2.0, and 11.9 ± 1.2 mm, respectively. Altering flow within the bath from 3 to 5 L/min did not significantly change lesion size. Conclusion: Simple element designs can be used to produce a range of lesions from very small sizes to lesions that are transmural in the ventricle. The temperature half‐time for microwave ablation is far greater than that of RF ablation. Like RF lesions, the lesions produced by microwave ablation have greater width than depth. Deep penetration of lesions into the ventricular myocardium can (only be achieved with these elements by producing lesions of perhaps unnecessarily large volume.
Two‐to‐One AV Block Associated with the Congenital Long QT Syndrome
Authors: PRUVOT ETIENNE , De TORRENTE ANTOINE , De FERRARI GAETANO M. , SCHWARTZ PETER J. , GOY JEAN‐JACQUES 
Published: April 2007

2:1 AV Block in LQTS. Introduction Conduction abnormalities associated with long QT syndrome (LQTS) have been reported as “pseudo 2:1 AV block” due to sinus intervals shorter than ventricular refractoriness. Method and Results: We report the electrophysiologic characteristics of a patient suffering from congenital LQTS with episodes of true 2:1 AV block. Induction of 2:1 infra‐Hisian blocks and return to 1:1 conduction were observed using single atrial and ventricular extrastimuli. The block was located in the Purkinje network but not in the myocardium. Conclusion: The His‐Purkinje system of our LQTS patient displayed dynamic properties with a strong increase in refractoriness for short‐long sequences and a decrease for long‐short sequences that triggered intermittent 2:1 AV blocks.
Sodium Pentobarbital Reduces Transmural Dispersion of Repolarization and Prevents Torsades de Pointes in Models of Acquired and Congenital Long QT Syndrome
Authors: SHIMIZU WATARU , McMAHON BRANDON , ANTZELEVITCH CHARLES 
Published: April 2007

Electrophysiologic Effects of Pentobarbital. Introduction: Sodium pentobarbital is widely used for anesthesia in experimental studies as well as in clinics, and it is known to prevent the development of torsades dc pointes (TdP) in in vivo models of the long QT syndrome (LQTS). Methods and Results: This study examines the effects of pentobarbital on transmural dispersion of repolarization (TDR) and induction of TdP in arterially perfused canine left ventricular wedge preparations in which transmembrane action potentials were simultaneously recorded from epicardial, M, and endocardial regions using floating glass microelectrodes together with a transmural ECG. d‐Sotalol and ATX‐II were used to mimic the LQr2 and LQT3 forms of congenital LQTS. Both d‐sotalol (100 μmol/L, n = 6) and ATX‐II (20 nmol/L., n = 6) preferentially prolonged the action potential duration (APD90) of the M cell, thus increasing in the QT interval and TDR, and leading to the development of spontaneous and stimulation‐induced TdP. In the absence and presence of d‐sotalol, pentobarbital (10, 20, and 50 μg/mL) prolonged the APD90 of epicardial and endocardial cells, and, to a lesser extent, that of the M cell, thus prolonging the QT interval but reducing TDR. In the ATX‐II model, the effects of pentobarbital on the QT interval and APD90 were biphasic: 10 μg/mL pentobarbital further prolonged APD90 of epicardial and endocardial cells more than that of the M cell; 20 to 50 μg/mL pentobarbital abbreviated the APD90 of epicardial and endocardial cells less than that of the M cell, thus abbreviating the QT internal and markedly reducing TDR. Twenty to 50 μg/mL pentobarbital totally suppressed spontaneous as well as stimulation‐induced TdP in both models. Conclusion: Our data indicate that pentobarbital reduces TDR in control and under conditions of congenital and acquired LQTS, and suggest that this mechanism may contribute to the ability of the anesthetic to prevent the development of spontaneous as well as stimulation‐induced TdP under conditions mimicking LQT2, LQT3, and acquired (drug‐induced) forms of the LQTS. The data also serve to illustrate that there are circumstances under which QT prolongation may not be arrhythmogenic.
ECG of the “Newborn” Mouse (Mus Domesticus) with Specific Reference to Comparative AV Transmission
Authors: van der TWEEL L. HENK , STRACKEE JAN , STOKHOF ARNOLD A. , WASSENAAR CLAES , MEIJLER FRITS L. 
Published: April 2007

Comparative AV Transmission. Introduction: The objective of this study was to record the ECG of the smallest living mammal to extend the domain of data for comparative A V nodal electrophysiologic purposes. These data are needed to establish the relationship between the PR interval and heart size in mammalian species of all sizes. Methods and Results: In recently horn mice (age 1.5 to 8 weeks) weighing between 2.5 and 10 g and with estimated heart weights between 15 and 60 mg, ECGs, using bipolar limb leads, were recorded during general anesthesia. The PR interval, representing AV transmission time was about 40 msec, which is quite long for hearts of this size. On the basis of detailed analysis of the data, we postulate the presence of a fixed delay or discontinuous propagation in the AV node not only in newborn mice, hut in mammals of all sizes. Conclusion: A V transmission times obtained in mammals (including humans) cannot be explained on the basis of generally accepted, classic AV conduction theories. The acceptance of the presence of a fixed delay in the A V node may ultimately be of value to better understand A V node function during sinus rhythm and supraventricular arrhythmias.
Dynamic Changes in Electrogram Morphology at Functional Lines of Block in Reentrant Circuits During Ventricular Tachycardia in the Infarcted Canine Heart
Authors: CIACCIO EDWARD J. , SCHEINMAN MELVIN M. , FRIDMAN VITALIY , SCHMITT HEIKO , COROMILAS JAMES , WIT ANDREW L. 
Published: April 2007

Localization of Reentrant Circuits Using ATM. Introduction: Fractionated, low‐amplitude or long‐duration electrograms have limited specificity for locating reentrant circuits causing ventricular tachycardia (VT). In this study a new method is described, adaptive template matching (ATM), based on the quantification of beat‐to‐beat changes in electrograms, for locating functional reentrant circuits that are relatively stable and cause monomorphic VT. Methods and Results: Monomorphic VTs were induced in 4‐day‐old infarcted canine hearts by programmed stimulation and reentrant circuits mapped in the epicardial border zone with a 196 or 312 bipolar electrode array. For ATM analysis, a template electrogram from each electrode, during an early cycle, was matched with all subsequent (input) electrograms at the same site by weighting the inputs of amplitude, duration, average baseline, and phase lag. The mean square error (MSE) between template and input was the criterion used to adapt the weights, and was also a measure of changes in electrogram shape that occur from cycle to cycle. The variance of each of the weighting parameters at all electrode sites were plotted on a representation of the electrode array, and the location of the functional lines of block bounding the central common pathway of reentrant circuits with figure‐of‐eight characteristics, overlaid on the ATM map. Peaks of high variance were found to be coincident with functional lines of block during all tachycardia episodes. Conclusion: Specific beat‐to‐beat changes in electrograms occur at functional lines of block in reentrant circuits that can be quantified by ATM analysis, suggesting that these regions might be located without activation mapping. The method might be useful to guide ablation catheter position.
Long‐Term (Subacute) Potassium Treatment in Congenital HERG‐Related Long QT Syndrome (LQTS2)
Authors: TAN HANNO L. , ALINGS MARCO , VAN OLDEN RUDOLF W. , WILDE ARTHUR A.M. 
Published: April 2007

Potassium Treatment in LQTS2. Introduction: Congenital long QT syndrome (LQTS) is subdivided according to the underlying gene defect. In LQTS2, an aberrant HERG gene that encodes the potassium channel IKr leads to insufficient IKr activity and delayed repolarization, causing ECG abnormalities and torsades de pointes (TdP). Increasing serum potassium levels by potassium infusion normalizes the ECG in LQTS2 because IKr activity varies with serum potassium levels. Methods and Results: In an LQTS2 patient who presented with TdP, we attempted to achieve a long‐term (subacute) elevation of serum potassium by increased potassium intake and potassium‐sparing drugs. However, due to renal potassium homeostasis, it was impossible to achieve a long‐lasting rise of serum potassium above 4.0 mmol/L. Conclusion: Although raising serum potassium reverses the ECG abnormalities in LQTS2, a long‐lasting rise of serum potassium is only partially achievable because in the presence of normal renal function, potassium homeostasis limits the amount of serum potassium increase.
Capture Window in Human Atrial Fibrillation
Authors: CAPUCCI ALESSANDRO , RAVELLI FLAVIA , NOLLO GIANDOMENICO , MONTENERO ANNIBALE S. , BIEFL MAURO , VILLANI GIOVANNI Q. 
Published: April 2007

Capture Window in Human AF. Introduction: Local capture of atrial fibrillation (AF) was shown in animal experiments for a wide range of pacing rates, thus demonstrating the existence of an excitable gap. The aim of this study was to assess the existence of an excitable gap in human AF by studying the mechanism of local control and acceleration of AF over a wide range of pacing rates and by evaluating the time window of capture. Methods and Results: Recording and stimulation of electrical activity in the right atrium during AF was performed by a monophasic action potential (MAP) contact electrode catheter in 17 patients with lone AF during electrophysiologic study. Stimulation was started at pacing intervals close to the mean AF interval, and the time window of capture was estimated by lengthening or shortening the pacing interval until capture was lost. Pacing intervals shorter than the minimum cycle length for capture were also tested. Beat‐to‐beat measurements of AF intervals during pacing were performed. Atrial MAP signal showed rapid irregular activity with an average AF interval of 151.3 ± 16.1 msec and SD of 21.3 ± 5.2 msec. Rapid pacing with a cycle length slightly shorter or longer than the mean AF interval resulted in local capture of AF. The width of time window of capture ranged from 22 to 36 msec, with a mean value of 28.8 ± 4.9 msec. The average minimum pacing interval of stable capture was 129.2 ± 19.5 msec, while the maximum was 158.1 ± 18.7 msec, corresponding to 85% and 104% of mean AF cycle length, respectively. Pacing too rapidly resulted in a transient acceleration of AF, with an average shortening of fibrillation interval from 149.8 ± 16.6 to 123.2 ± 15.1 msec (P < 0.01). Conclusion: Local capture is feasible during AF in humans over a wide range of pacing rates, indicating the possibility of regional control of the fibrillatory process. This result demonstrates the presence of an excitable gap during AF in human atria.
Discrete Systolic Potentials During Ventricular Tachycardia in Patients with Prior Myocardial Infarction
Authors: BOGUN FRANK , KNIGHT BRADLEY , GOYAL RAJIVA , MICHAUD GREGORY F. , STRICKBERGER S. ADAM , HOHNLOSER STEFAN H. , MORADY FRED 
Published: April 2007

Systolic Potentials, introduction: Isolated diastolic potentials have been found to be helpful in identifying critical sites for ablation of ventricular tachycardia (VT) in patients with coronary artery disease. However, discrete potentials that occur during systole have not been previously described. The purpose of this study was to determine the significance of discrete systolic potentials during VT in patients with coronary artery disease. Methods and Results: Twenty‐seven patients with a mean age of 66 ± 12 years (± standard deviation) who bad coronary artery disease underwent radiofrequency catheter ablation of 42 VTs that had a mean cycle length of 486 ± 78 msec. The only criterion used to select target sites for ablation was concealed entrainment, which was present at 92 sites. Thirty‐five of the 42 VTs (83%) were successfully ablated. A discrete systolic potential was recorded during 7 of the 42 VTs (17%). In all cases, the interval between the discrete systolic potential and the next QRS complex was equal to the stimulus‐QRS interval during concealed entrainment. At all seven sites where a discrete systolic potential was recorded, delivery of radiofrequency energy resulted in successful ablation of the VT. Conclusion: Discrete systolic potentials may be present in patients with coronary artery disease in approximately 17% of VTs in which there is concealed entrainment. If the interval between the discrete systolic potential and the next QRS complex matches the stimulus‐QRS interval during concealed entrainment, delivery of radiofrequency energy is likely to result in successful ablation of the VT.
Atrial Sensing and AV Synchrony in Single Lead VDD Pacemakers: A Prospective Comparison to DDD Devices with Bipolar Atrial Leads
Authors: WIEGAND UWE K.H. , BODE FRANK , SCHNEIDER REGINA , TAUBERT GUNNAR , BRANDES AXEL , PETERS WERNER , KATUS HUGO A. , POTRATZ JURGEN 
Published: April 2007

Atrial Sensing and AV Synchrony in VDD and DDD Devices, Introduction: Single lead VDD pacing has offered an alternative to DDD systems in patients with isolated AV block. Up to now, however, the relative performance of these pacemaker systems was not systematically compared. Methods and Results: Three hundred sixty patients who received either a VDD pacemaker (n = 180) or a DDD device (n = 180) with a bipolar atrial lead were investigated prospectively for a mean period of 30 ± 13 months. Pacemaker function was analyzed by telemetry. Holter monitoring, and exercise ECG. Time of implantation and fluoroscopy was significantly lower with VDD devices (44.3 ± 5.1 min vs 74.4 ± 13.5 min and 4.6 ± 2.5 min vs 10.3 ± 5.6 min in DDD pacemakers, respectively). Intermittent atrial undersensing occurred in 23.3% of patients with a VDD pacemaker and in 9.4% with DDD devices (NS). The incidence of atrial tachyarrhythmias did not differ between the VDD (6.7%) and the DDD group (6.1%). Sinns node dysfunction developed in 1.9% of patients, but the vast majority (85.7%) of patients were asymptomatic. There was a tendency for a higher rate of operative revisions in the DDD group (6.1% vs 3.3% in VDD pacemakers, P = 0.15). Cumulative maintenance of AV‐synchronized pacing mode was 94.9% in patients with VDD pacemakers and 92.1% with DDD devices (NS). Conclusion: With the benefit of a simpler implant procedure, long‐term outcome of single lead VDD pacing is equivalent to DDD pacing in patients with AV block and preoperative normal sinus node function.
Wavelength and Conduction Inhomogeneity in Each Atrium in Patients with Isolated Mitral Valve Disease and Atrial Fibrillation
Authors: NITTA TAKASHI , IMURA HAJIME , BESSHO RYUZOU , HOSAKA HIROKI , YAMAUCHl SHIGEO , TANAKA SHIGEO 
Published: April 2007

AF in Mitral Valve Disease. Introduction: Patients with mitral valve disease frequently have atrial fibrillation (AF), and the left atrium is presumed to be the primary atrium that develops AF. However, it is still not clear whether the electrophysiologic abnormalities responsible for AF are confined to the left atrium in this subset of patients. Methods and Results: To examine the AF vulnerability of each atrium, we measured the wavelength and in homogeneity of the conduction at the lateral right atrium, lateral left atrium, and Bachmann's bundle after defibrillation of AF in seven patients undergoing the maze procedure and mitral valve surgery for AF and isolated mitral valve disease, respectively (AF group). The data were compared with five coronary surgery patients in sinus rhythm (SR group). The wavelength in the AF group was significantly shorter (P < 0.05) than in the SR group not only at the lateral left atrium (225 ± 62 vs 285 ± 36 mm) but also at the lateral right atrium (214 ± 54 vs 254 ± 34 mm). The variation coefficient of the local maximum activation phase difference in the AF group (1.9 ± 0.8 at the right atrium, 2.1 ± 0.8 at the lateral left atrium, and 2.0 ± 0.6 at Bachmann's bundle) was significantly greater (P < 0.05) than in the SR group at all atrial regions. Conclusion: AF vulnerability was not confined to the left atrium immediately after defibrillation in AF patients with isolated mitral valve disease. Electrical remodeling resulting from perpetuation of AF, pathological changes extending to the right atrium, geometric changes caused by the atrial interactions occurring across the interatrial septum, or a combination of these may explain the results.
A Role for the Renin‐Angiotensin System in the Evolution of Cardiac Memory
Authors: RICARD PHILIPPE , JR PETER DANTLO , COHEN IRA S. , BURKHOFE DANIEL , ROSEN MICHAEL R. 
Published: April 2007

Angiotensin II and Cardiac Memory. Introduction: We studied the role of the cardiac renin‐angiotensin II system in the genesis of cardiac memory, in which T wave changes induced by ventricular pacing (VP) accumulate and persist during subsequent sinus rhythm. Methods and Results: Anesthetized dogs were instrumented via a thoracotomy and three 20‐minute runs of VP were interspersed with periods of normal sinus rhythm sufficient to permit T wave recovery to 90% of control. Memory was quantified as the change (δ) in T wave vector angle showing accumulation over the three monitoring periods. In five control dogs T wave vector = ‐ 27 ± 49°, and this shifted by 104° (P < 0.05) over the three postpacing recovery periods. In seven dogs infused with the receptor blocker saralasin, five infused with the angiotensin‐converting enzyme inhibitor captopril, and four infused with the tissue protease inhibitor chymostatin, there were significant reductions in the incidence and the accumulation of memory. In four other experiments, we used isolated, blood‐perfused canine hearts to demonstrate that VP used to induce memory alters the contractile pattern of the left ventricle. Conclusions: We propose that the alteration in myocardial stretch induced by pacing activates angiotensin II synthesis by cardiac cells. We propose, further that the endogenous cardiac renin‐angiotensin II system (blocked by saralasin, captopril and by chymostatin) is an important contributor to the induction of memory.