Publications by authors named "Lerman B"

The ventricular response in atrial fibrillation is often described as "chaotic," but this has not been demonstrated in the strict mathematical sense. A defining feature of chaotic systems is sensitive dependence on initial conditions: similar sequences evolve similarly in the short term but then diverge exponentially. We developed a nonlinear predictive forecasting algorithm to search for predictability and sensitive dependence on initial conditions in the ventricular response during atrial fibrillation.

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Introduction: The effects of adenosine on atrial tachycardia (AT) remain controversial, and the mechanistic implications of adenosine termination have not been fully established. The purpose of this study was to elucidate the differential effects of adenosine on focal and macroreentrant AT and describe the characteristics of adenosine-sensitive AT.

Methods And Results: Thirty patients received adenosine during AT.

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Many biomedical experiments require a precisely timed real-time (RT) computer interface. Because commonly used desktop operating systems are inherently non-real-time, real-time laboratory computer systems are often based on outdated DOS software or expensive proprietary real-time operating systems. Here we discuss a real-time computing system, based on the free RT-LINUX operating system, which we have developed for adaptive pacing control in a clinical cardiac electrophysiology laboratory.

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Background: Tilt testing is used to establish the diagnosis of neurally mediated syncope. However, applicability of the tilt test is limited by test sensitivity and length of time required to perform the test. We hypothesized that adenosine could facilitate the induction of neurally mediated syncope through its sympathomimetic effects and therefore could be used as an alternative to routine tilt testing.

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Introduction: Adenosine has no direct electrophysiologic function in ventricular tissue, but in the presence of cyclic adenosine monophosphate (cAMP), stimulation exerts a potent antiadrenergic effect. This effect has been exploited in the recognition and treatment of ventricular tachycardia (VT) due to cAMP-mediated triggered activity and automaticity, which are respectively terminated and suppressed by adenosine. However, the effects of adenosine on catecholamine-facilitated reentrant VT are unknown.

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Objectives: Although enhanced sympathetic tone is thought to be proarrhythmic and beta-blockade reduces the risk of sudden cardiac death in survivors of myocardial infarction, the role of the autonomic nervous system in triggering spontaneous ventricular ectopy and ventricular tachycardia (VT) has not been fully elucidated. The purpose of this study was to compare and contrast autonomic tone preceding spontaneous ventricular arrhythmias in patients with reentrant, triggered, and automatic forms of VT.

Background: The prevailing model of reentrant VT is based on a triggering beat interacting with a fixed substrate.

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Idiopathic ventricular tachycardia is a generic term that describes the various forms of ventricular arrhythmias that occur in patients without structural heart disease and in the absence of the long QT syndrome. Many of these tachycardias are focal in origin, localize to the right ventricular outflow tract (RVOT), terminate in response to beta blockers, verapamil, vagal maneuvers, and adenosine, and are thought to result from cAMP-mediated triggered activity. DNA was prepared from biopsy samples obtained from myocardial tissue from a patient with adenosine-insensitive idiopathic ventricular tachycardia arising from the RVOT.

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We compared the performance of precordial QT dispersion, late potentials on the signal-averaged electrocardiogram (ECG), and reduced left ventricular ejection fraction for identification of inducible ventricular tachycardia (VT) in 162 patients undergoing electrophysiologic study (EPS). QT(apex) dispersion in 56 patients with inducible VT (72 +/- 55 msec) was greater than that in 106 patients without inducible VT (55 +/- 36 msec, p < 0.01); dispersion was greater in both groups than in 144 normal subjects (33 +/- 19 msec).

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Background: Adenosine-sensitive ventricular tachycardia (VT) is thought to be due to cAMP-mediated triggered activity. It typically originates from the RVOT and occurs in patients with apparently normal hearts. Using magnetic resonance imaging (MRI), we tested the hypothesis that adenosine-sensitive VT occurs in patients without structural heart disease.

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Idiopathic left ventricular tachycardia (ILVT) differs from idiopathic right ventricular outflow tract (RVOT) tachycardia with respect to mechanism and pharmacologic sensitivity. ILVT can be categorized into three subgroups. The most prevalent form, verapamil-sensitive intrafascicular tachycardia, originates in the region of left posterior fascicle of the left bundle.

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Beta-blockers are a first line therapy for neurocardiac syncope, but are not always effective. The purpose of this study was to determine whether differential autonomic responses to orthostasis predict the response of patients with neurocardiac syncope to beta-adrenergic blockade. We computed the RMS successive difference of the RR intervals (RMSSD: a measure of cardiac parasympathetic tone) during supine and upright phases of the initial tilt test in 28 patients with syncope and positive tilt tests who were treated with atenolol.

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Introduction: Vasodepressor syncope is a common cause of syncope, but the initiating event that triggers the vasodepressor response remains incompletely understood. Although ischemia due to acute right coronary occlusion may precipitate hypotension and bradycardia through the Bezold-Jarisch reflex, an ischemic precipitant for the common vasodepressor faint has not been previously identified. In the present study, we present evidence for a causal relationship between myocardial ischemia and vasodepressor syncope.

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Right ventricular outflow tract (RVOT) tachycardia is the most common form of idiopathic ventricular tachycardia (VT). Phenotypically, RVOT tachycardia segregates into two predominant forms, one characterized by repetitive monomorphic nonsustained VT and the other by paroxysmal exercise induced sustained VT. There is an increasing body of evidence to support the concept that both forms of tachycardia reflect disparate clinical manifestations of an identical cellular mechanism (i.

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Background: Modification of atrioventricular (AV) conduction during atrial fibrillation (AF) may be achieved by radiofrequency ablation in the posteroseptal region of the tricuspid annulus. We tested the hypothesis that elimination of the posterior atrionodal input rather than direct damage to the compact AV node accounts for the decrease in ventricular rate after AV nodal modification.

Methods And Results: Twenty-four patients with the typical form of AV nodal reentrant tachycardia (AVNRT) underwent selective radiofrequency ablation of the slow AV nodal pathway in the posteroseptal tricuspid annulus.

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A prospective observational study in an inner-city teaching hospital was conducted to evaluate the safety and efficacy of intravenous methohexital (MTX) in the emergency department (ED). Pulse oximetry, vital signs and Glasgow Coma Scale (GCS) scores were recorded serially for 30 minutes after the administration of MTX to 76 adult patients. Likert scales of 1 to 5 were used to record the physician's assessment of the adequacy of sedation and the patient's assessments of recall and pain of the procedure.

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Idiopathic ventricular tachycardia (VT) is a term that refers to tachycardia that arises from ventricles devoid of apparent structural abnormalities. This form of VT is now recognized to be related to several distinct entities and includes a reentrant form typically located in the region of the left posterior fascicle, an automatic form that may originate from either ventricle, and a form that originates from the right ventricular outflow tract. This last type can account for up to 80% of cases of idiopathic VT and with few exceptions can be further subdivided into repetitive monomorphic VT and paroxysmal stress-induced VT.

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Objectives: This study sought to present evidence that fast atrioventricular (AV) node pathways with posterior exit sites may participate in typical AV node reentry.

Background: Catheter ablation of the slow AV node pathway in the posteroseptal right atrium is the preferred therapeutic approach in patients with AV node reentrant tachycardia. Despite the success achieved with this approach, electrophysiologic changes consistent with fast pathway ablation are occasionally observed.

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A high common mode voltage (Vcm) relative to earth ground is produced on the myocardium during the delivery of a defibrillator pulse and can generate a differential error signal when potential gradients are recorded with bipolar electrodes and isolation amplifiers. The error signal is proportional to Vcm, and therefore, a reduction in Vcm improves the accuracy of the potential gradient data. Experiments were conducted on 5 dogs to determine whether Vcm can be controlled using a bridge circuit.

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Background: The most common form of idiopathic ventricular tachycardia (VT) is repetitive monomorphic VT (RMVT), which is characterized by frequent ventricular ectopy and salvos of nonsustained VT with intervening sinus rhythm. Unlike most other forms of idiopathic VT, this tachycardia typically occurs at rest and is nonsustained. The mechanism of RMVT is undefined.

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Analysis of the duration and terminal components of the filtered QRS complex on the signal-averaged electrocardiogram (ECG) has been widely used for the detection of late potentials. Although filtered QRS duration is strongly related to 12-lead QRS duration, the relation of performance of the signal-averaged ECG to baseline QRS duration has not been critically examined. To examine the relation of test performance of the signal-averaged ECG to 12-lead QRS duration and to test the hypothesis that the difference between filtered and baseline 12-lead QRS duration would reflect more accurately the presence of late potentials than would analysis of the filtered QRS alone, we evaluated signal-averaged and 12-lead ECGs in 144 normal subjects and in 132 patients who were examined by electrophysiologic study and of whom 45 had inducible sustained monomorphic ventricular tachycardia.

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Finite element modeling has played an increasingly important role in the study of defibrillation. In order to model well the complex anatomical details, a large number of elements are required in the finite element grid, leading to a large set of equations that often cannot be solved effectively with the computational power of conventional computers. In this paper, we describe the use of a data parallel computer to provide the memory and reduction in solution time for solving these large finite element problems.

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Introduction: Bundle branch reentry (BBR) typically occurs in patients with dilated cardiomyopathy and infra-Hisian conduction system disease. The macroreentrant circuit of BBR is confined to the His-Purkinje system (HPS) and ventricular myocardium. As such, the atrioventricular (AV) node plays no role in the tachycardia circuit.

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