Clinical Implications of Brief Device-Detected Atrial Tachyarrhythmias in a Cardiac Rhythm Management Device Population: Results from the Registry of Atrial Tachycardia and Atrial Fibrillation Episodes.

Background: The RATE Registry (Registry of Atrial Tachycardia and Atrial Fibrillation Episodes) is a prospective, outcomes-oriented registry designed to document the prevalence of atrial tachycardia and/or fibrillation (AT/AF) of any duration in patients with pacemakers and implantable cardioverter defibrillators (ICDs) and evaluate associations between rigorously adjudicated AT/AF and predefined clinical events, including stroke. The appropriate clinical response to brief episodes of AT/AF remains unclear.

Methods: Rigorously adjudicated electrogram (EGM) data were correlated with adjudicated clinical events with logistic regression and Cox models.

Atrial electrograms improve the accuracy of tachycardia interpretation from ICD and pacemaker recordings: The RATE Registry.

Background: Tachycardia diagnoses from implantable device recordings ultimately depend on the analysis of captured electrograms (EGMs). The degree to which atrial EGMs improve tachycardia discrimination, dependent on the level of expertise of the medical professional involved, remains uncertain.

Objective: The purpose of this article was to determine whether atrial EGM recordings improve tachycardia discrimination and whether this improvement, if any, varies for professionals with different levels of training.

Improved pacemaker pulse detection: clinical evaluation of a new high-bandwidth electrocardiographic system.

Background: This study compares the pacemaker pulse detection performance of the new high-bandwidth (hi-fi) electrocardiographic (ECG) acquisition system to a conventional system in a prospective clinical evaluation.

Methods: Electrocardiograms from 88 subjects with implanted pacemakers were recorded using different pacemaker programmed outputs and with different noise levels. Each ECG was recorded simultaneously from both systems.

Observations of pacemaker pulses in high-bandwidth electrocardiograms and Dower-estimated vectorcardiograms.

Background: Electronic pacemaker pulses are poorly reproduced in computerized electrocardiogram (ECG) tracings, impairing both automated and human interpretation. In this study, a high-bandwidth system is used to examine ECG and vectorcardiogram characteristics of pacemaker pulses.

Methods: In 69 subjects with artificial pacemakers, electrocardiograms were recorded at 75,000 samples per second with a high-bandwidth ECG system (GE Healthcare, Milwaukee, WI).

Manifestation of left atrial events and interatrial frequency gradients in the surface electrocardiogram during atrial fibrillation: contributions from posterior leads.

Background: In most patients, atrial fibrillation (AF) is initiated and maintained by pulmonary vein foci, but the relationship between left atrial (LA) events and the surface electrocardiogram (ECG) is largely unknown. We investigated whether LA events are reflected in the surface ECG and whether additional information can be obtained from recording posterior leads in patients with AF.

Methods And Results: In 10 patients undergoing radiofrequency ablation of AF, we identified 103 5-second segments with a significant frequency gradient between right (RA) and left (LA) intraatrial electrograms, or with frequency changes from segment to segment in the same patient.

The relationship between programmed pacemaker pulse amplitude and the surface electrocardiogram recorded amplitude: application of a new high-bandwidth electrocardiogram system.

Background: Recording and displaying outputs from electronic pacemakers with electrocardiogram (ECG) recorders typically used in clinical practice have presented a number of technical limitations. We have recently reported on a new high-bandwidth ECG system and have shown that it is capable of reproducing accurate pulse amplitudes and durations from the body surface. In the present work, we have used our data to calculate a transform function between the programmed pacemaker output voltage and the amplitude on the body surface.

Comparison of self-gated cine MRI retrospective cardiac synchronization algorithms.

Purpose: To determine whether improved self-gating (SG) algorithms can provide superior synchronization accuracy for retrospectively gated cine MRI.

Materials And Methods: First difference, template matching, and polynomial fitting algorithms were implemented to improve the synchronization of MRI data using cardiac SG signals. Cine datasets were acquired during short-axis, two-, three-, and four-chamber cardiac MRI scans.

Extraction of the magnetohydrodynamic blood flow potential from the surface electrocardiogram in magnetic resonance imaging.

The magnetohydrodynamic effect generates voltages related to blood flow, which are superimposed on the electrocardiogram (ECG) used for gating during cardiac magnetic resonance imaging (MRI). A method is presented for extracting the magnetohydrodynamic signal from the ECG. The extracted magnetohydrodynamic blood flow potential may be physiologically meaningful due to its relationship to blood flow.

Derivation of orthogonal leads from the 12-lead electrocardiogram. Performance of an atrial-based transform for the derivation of P loops.

The objective of this study was the evaluation of the accuracy of Dower inverse transform for the derivation of the P wave in orthogonal leads. We tested the accuracy of Dower transform on the P wave and compared it with a P-wave-optimized transform in a database of 123 simultaneous recordings of electrocardiograms and vectorcardiograms. This new transform achieved a lower error when we compared derived vs true measured P waves (mean +/- SD, 12.

Abrupt changes in fibrillatory wave characteristics at the termination of paroxysmal atrial fibrillation in humans.

Aims: We investigated the process of spontaneous termination of atrial fibrillation (AF) to determine its time course from the surface ECG.

Methods And Results: We studied fibrillatory waves in Holter recordings of paroxysmal and sustained AF. Following QRS-T cancellation dominant frequencies (DFs) were computed and the relationship of DF to termination was scrutinized.

Short-term dynamics in fibrillatory wave characteristics at the onset of paroxysmal atrial fibrillation in humans.

Introduction: The purpose of this study was to investigate the magnitude and time course of fibrillatory wave dynamics during spontaneous onset of paroxysmal atrial fibrillation (AF).

Methods: We studied fibrillatory waves in Holter recordings of paroxysmal AF with regard to the fibrillation-free interval (FFI) preceding each episode.

Results: For 38 episodes of paroxysmal AF in 20 patients, dominant frequency (DF) ranged from 4.

AHA scientific statement: practice standards for electrocardiographic monitoring in hospital settings: an American Heart Association Scientific Statement from the Councils on Cardiovascular Nursing, Clinical Cardiology, and Cardiovascular Disease in the Young: endorsed by the International Society of Computerized electrocardiology and the American Association of Critical-Care Nurses.

The goals of electrocardiographic (ECG) monitoring in hospital settings have expanded from simple heart rate and basic rhythm determination to the diagnosis of complex arrhythmias, myocardial ischemia, and prolonged QT interval. Whereas Computerized arrhythmia analysis is automatic in cardiac monitoring systems, computerized ST-segment ischemia analysis is available only in newer-generation monitors, and computerized QT-interval monitoring is currently unavailable. Even in hospitals with ST-monitoring capability, ischemia monitoring is vastly underutilized by healthcare professionals.

Relationship between pattern of occurrence of atrial fibrillation and surface electrocardiographic fibrillatory wave characteristics.

Objectives: The purpose of this study was to assess whether surface ECG fibrillatory (f)-wave characteristics reflect clinical variables, especially pattern of occurrence.

Background: In clinically stable patients, f waves have fairly constant quantitative characteristics. Both electrophysiologic and structural remodeling might modify f waves.

Surface ECG vector characteristics of organized and disorganized atrial activity during atrial fibrillation.

Background: The aim of this study was to examine atrial organization from vectorcardiograms (VCGs) derived from the surface ECG of atrial fibrillatory waves.

Methods: We retrieved ECGs recorded during ventricular asystole from 22 patients with AF undergoing ablation of the AV junction. The synthesized VCG of each f-wave cycle of each ECG and its plane of best fit, described by azimuth and elevation angles relative to the frontal plane, were computed.

Practice standards for electrocardiographic monitoring in hospital settings: an American Heart Association scientific statement from the Councils on Cardiovascular Nursing, Clinical Cardiology, and Cardiovascular Disease in the Young: endorsed by the International Society of Computerized Electrocardiology and the American Association of Critical-Care Nurses.

The goals of electrocardiographic (ECG) monitoring in hospital settings have expanded from simple heart rate and basic rhythm determination to the diagnosis of complex arrhythmias, myocardial ischemia, and prolonged QT interval. Whereas computerized arrhythmia analysis is automatic in cardiac monitoring systems, computerized ST-segment ischemia analysis is available only in newer-generation monitors, and computerized QT-interval monitoring is currently unavailable. Even in hospitals with ST-monitoring capability, ischemia monitoring is vastly underutilized by healthcare professionals.

Atrial fibrillatory wave characteristics on surface electrogram: ECG to ECG repeatability over twenty-four hours in clinically stable patients.

Introduction: Fibrillatory waves on the surface ECG have been scrutinized to allow inferences about underlying mechanisms and pathophysiology, based on the premise that fibrillatory waves do not vary "randomly" but provide a consistent reflection of the underlying state of the atria in an individual patient. This premise is untested.

Methods And Results: Ten standard ECGs were recorded over a 24-hour period in each of 20 clinically stable inpatients with atrial fibrillation.

Atrial flutter vector loops derived from the surface ECG: does the plane of the loop correspond anatomically to the macroreentrant circuit?

We hypothesized that if the right atrial circuit during isthmus dependent atrial flutter provides the dominant contribution to the surface electrocardiogram (ECG), the three-dimensional vector loop of the flutter waves would primarily be in a plane approximately parallel to the tricuspid ring. Twenty vectorcardiograms of isthmus dependent atrial flutter derived from 12-lead ECGs of 19 patients recorded prior to radiofrequency ablation were analyzed. The plane of each loop, described by azimuth and elevation angles relative to the frontal plane, was estimated with two methods: 1) plane of maximum loop area and 2) plane of best fit.

Accelerometer-based body-position sensing for ambulatory electrocardiographic monitoring.

Our objective is to validate the ability of 3 appropriately placed accelerometers to determine body position during ambulatory electrocardiographic (ECG) monitoring and to demonstrate the clinical applicability of this method. During ambulatory (Holter) monitoring, the ability to know a patient's position (lying down, sitting, standing, or changing from one position to another) is important in the evaluation of common symptoms such as dizziness, palpitations, and syncope. Changes in body position are also known to alter the electrical axis of the heart, resulting in artifactual changes in QRS amplitude and ST-segment morphology.

The effect of QRS cancellation on atrial fibrillatory wave signal characteristics in the surface electrocardiogram.

QRS cancellation methods have been used to analyze atrial activity in the electrocardiogram for such rhythms as atrioventricular dissociated ventricular tachycardia and atrial fibrillation. However, how well the cancellation methods work has never been evaluated by some gold standard. In this study of patients undergoing radiofrequency ablation of the atrioventricular junction, the contribution of imperfect cancellation was evaluated by comparing the "pure" atrial fibrillation (the gold standard) during a brief ventricular asystole to data obtained by a cancellation method during pacing just before and after the asystole.