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Ambulatory ECG (ambulatory + ecg)

Distribution by Scientific Domains

Medical Sciences	100%

Terms modified by Ambulatory ECG

ambulatory ecg recording

Selected Abstracts

Effect of Noise on T-Wave Alternans Measurement in Ambulatory ECGs Using Modified Moving Average versus Spectral Method

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2009
RAJA J. SELVARAJ M.D.
Background: The modified moving average (MMA) and spectral method (SM) are commonly used to measure T-wave alternans (TWA), but their accuracy has not been compared in ambulatory electrocardiograms (ECGs) where TWA signal-to-noise ratio is low. Our objective was to compare the effect of noise and signal nonstationarity on the accuracy of TWA measurement using MMA versus SM when applied to synthetic and ambulatory ECGs. Methods: Periodic and nonperiodic noise were added to noiseless synthetic ECGs. Simulated TWA (0,20 ,V) was added to synthetic ECGs and ambulatory ECG recordings. TWA was measured using SM and MMA, and the measurement error relative to added TWA was compared. An MMA ratio was used to discriminate TWA signal from noise. Signal nonstationarity was simulated by changing heart rate, TWA magnitude, and TWA phase. Results: With no added TWA, MMA falsely measured TWA in synthetic and ambulatory ECGs, while false measurement was not seen with SM. An MMA ratio > 1.2 eliminated false TWA detection. In the presence of low TWA magnitude (<10 ,V), TWA was overestimated by MMA and underestimated by SM in proportion to the noise level. In synthetic ECGs with periodic noise and 10-,V added TWA, MMA was less accurate than SM. The effects of simulated signal nonstationarity on the TWA magnitude measured with MMA versus SM were similar using a 64-beat analysis window. Conclusions: In the presence of noise, MMA falsely detects or overestimates simulated TWA in ambulatory ECG recordings. In this setting, the proposed MMA ratio improves the specificity of MMA. [source]

SCN5A Mutation Associated with Cardiac Conduction Defect and Atrial Arrhythmias

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2006
PÄIVI J. LAITINEN-FORSBLOM Ph.D.
Introduction: We aimed at identifying the molecular defect underlying the clinical phenotype of a Finnish family with a cardiac conduction defect and atrial arrhythmias. Methods and Results: A large Finnish family was clinically evaluated (ECG, 24-hour ambulatory ECG, echocardiography). We performed linkage analysis with markers flanking the SCN5A gene and subsequently sequenced the SCN5A gene. Five family members had atrial arrhythmias and intracardiac conduction defects, and due to bradycardia needed a pacemaker when adolescents. No heart failure or sudden cardiac death was observed. Left ventricle dilatation was seen in one individual and three individuals had a slightly enlarged right ventricle. Premature death due to stroke occurred in one subject during the study, and two other members had suffered from stroke at young age. Linkage analysis favored the role of the SCN5A gene in disease pathogenesis, and direct sequencing disclosed D1275N mutation. This alteration was present not only in all six affected individuals, but also in two young individuals lacking clinical symptoms. Conclusions: Cardiac conduction defect and atrial arrhythmias in a large Finnish family appear to result from the SCN5A D1275N mutation. Although no sudden cardiac death was recorded in the family, at least three affected members had encountered brain infarction at the age of 30 or younger. [source]

Abnormal Nocturnal Heart Rate Variability and QT Dynamics in Patients with Brugada Syndrome

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2007
BERTRAND PIERRE M.D.
Background: In Brugada syndrome (BSY), most of the ventricular arrhythmic events are nocturnal, suggesting an influence of the autonomic nervous system. Methods: In 46 patients (mean age = 41 ± 14 years, 43 men) with electrocardiograms (ECG) consistent with BSY and structurally normal hearts, we measured heart rate variability (HRV) and QT dynamics (QT/RR slopes) on 24-hour ambulatory ECG. Type 1 BSY-ECG was spontaneous in 23 (50%) and induced in 23 patients. Results: History of syncope was present in 23 patients (50%). Programmed ventricular stimulation induced ventricular tachyarrhythmias (VTA) in 13 patients (28%). A single patient developed ventricular tachycardia during a mean follow-up of 34 months. Compared to a control group matched for age and sex, HRV was decreased over 24 hours and during nighttime in patients with BSY (SDNN 122 ± 44 vs 93 ± 36 ms, P = 0.0008 and SDANN 88 ± 39 vs 54 ± 24 ms, P < 0.0001). QTend /RR slopes were decreased over 24 hours in patients with BSY (0.159 ± 0.05 vs 0.127 ± 0.05, P = 0.003) and particularly at night (0.123 ± 0.04 vs 0.089 ± 0.04, P = 0.0001). QTend /RR slopes were significantly decreased during nighttime in patients with spontaneous versus provoked BSY-ECG patterns. By contrast, HRV and QT/RR slopes were similar in symptomatic and asymptomatic patients, whether VTA were induced or not. Conclusions: Patients with a BSY-ECG pattern had lower HRV and QT/RR slopes than control subjects during nighttime. High-risk patients with spontaneous BSY-ECG patterns had the lowest nocturnal QTend/RR slopes. These unique repolarization dynamics might be related to the frequent nocturnal occurrence of VTA in BSY. [source]

Steady-State versus Non-Steady-State QT-RR Relationships in 24-hour Holter Recordings

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 3 2000
GILLES LANDE
The aim of the present study was to investigate the QT-RR interval relationship in ambulatory ECG recordings with special emphasis on the physiological circumstances under which the QT-RR intervals follow a linear relation. Continuous ECG recordings make it possible to automatically measure QT duration in individual subjects under various physiological circumstances. However, identification of QT prolongation in Holter recordings is hampered by the rate dependence of QT duration. Comparison of QT duration and QT interval rate dependence between different individuals implies that the nature of the QT-RR relationship is defined in ambulatory ECG. Holter recordings were performed in healthy volunteers at baseline and after administration of dofetilide, a Class III antiarrhythmic drug. After dofetilide, beat-to-beat automated QT measurements on Holter tapes were compared with manually measured QT intervals on standard ECGs matched by time. The QT-RR relationship was analyzed at baseline in individual and group data during three different periods: 24-hour, daytime, and nighttime. Data were collected under steady-state or non-steady-state conditions of cycle length and fitted with various correction formulae. Our study demonstrated an excellent agreement between manually and automated measurements. The classic Bazett correction formula did not fit the QT-RR data points in individual or group data. When heart beats were selected for a steady rhythm during the preceding minute, QT-RR intervals fit a linear relationship during the day and night periods, but not during the 24-hour period in both individual and group data. In contrast, in the absence of beat selection, data fit a more complex curvilinear relationship irrespective of the period. Our study provides the basis for comparison of QT interval durations and QT-RR relationships between individuals and between groups of subjects. [source]