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QRS Onset (qr + onset)

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Selected Abstracts

ABSENCE OF CORRELATION BETWEEN QRS DURATION AND ECHOGRAPHIC PARAMETERS OF VENTRICULAR DESYNCHRONIZATION.

ECHOCARDIOGRAPHY, Issue 2 2004
CAN WE STILL TRUST THE ELECTROCARDIOGRAPHIC CRITERIA?
Background: Identification of the responder candidates for multisite pacing is still difficult and severe heart failure, dilated left ventricle with reduced ejection fraction, prolonged QRS with left bundle branch block (LBBB) are still considered the principal indicators of ventricular desynchronization. The aim of the study was to assess if echographic ventricular desynchronization parameters measured in patients with dilated cardiomyopathy and severe heart failure are correlated with the duration of the QRS on surface electrocardiogram. Methods: This study included 51 patients aged 58.8 ± 7.4 years with idiopathic DCM. The following parameters were measured: QRS duration; effective contraction time (ECT) measured as the interval between QRS onset and closure of aortic valve, interventricular delay (IVD) measured as the time between onset of aortic and pulmonary flow, left ventricular mechanical delay (LVD) as the time from maximal interventricular septum contraction and posterior wall contraction, posterior (P), lateral (L), and posterolateral (PL) wall delays, as the time from QRS onset to maximal wall contraction. Regional post-systolic contraction was defined in a given wall as the difference (contraction delay , ECT)> 50 ms. Results: 29 patients presented complete LBBB, 22 patients had QRS duration < 120 ms. 39 patients had a post-systolic contraction of the PL wall (32 patients of the L wall and 26 patients of the P wall). 16 patients with QRS duration <120 had a post-systolic contraction of the PL wall (as for the LBBB the rest of 39 patients). In 40 patients the sequence of regional ventricular contraction was: P-L-PL wall (16 patients with QRS < 120). LVD was > 100 ms in 36 patients (26 patients with LBBB and 10 with QRS < 120). 27 patients with LBBB and 6 with QRS < 120 ms presented IVD > 30 ms. There was no correlation between the QRS duration and the parameters listed above. Conclusions: In a population of patients with severe heart failure and dilated cardiomyopathy there is no correlation between the duration of the QRS and echocardiographic parameters of ventricular desynchronization. These results show that mechanical ventricular desynchronization can be observed in patients with a QRS duration < 120 ms. Further studies are needed to evaluate if this population could beneficiate of multisite pacing therapy. [source]

Synchronous Ventricular Pacing without Crossing the Tricuspid Valve or Entering the Coronary Sinus,Preliminary Results

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2009
BENHUR D. HENZ M.D.
Background: Right ventricular apical (RVA) pacing promotes tricuspid regurgitation (TR), electromechanical dyssynchrony, and ventricular dysfunction. We tested a novel intramyocardial bipolar lead to assess whether stimulation of the atrioventricular septum (AVS) produces synchronous ventricular activation without crossing the tricuspid valve (TV). Methods: A lead with an active external helix and central pin was placed on the AVS and the RVA in three dogs. High-density electroanatomic (EA) mapping was performed of both ventricles endocardially and epicardially. Intracardiac echocardiography was used to access ventricular synchrony. Results: The lead was successfully deployed into the AVS in all cases with consistent capture of the ventricular myocardium without atrial capture or sensing. The QRS duration was less with AVS compared with RVA pacing (89 ± 4 ms vs. 100 ± 11 ms [P < 0.0001, GEE P = 0.03]). There was decreased delay between color Doppler M-mode visualized peak contraction of the septum and the mid left ventricular free wall with AVS compared with RVA pacing (89 ± 91 ms vs. 250 ± 11 ms [P < 0.0001, GEE P = 0.006]). Activation time between the mid septum and mid free wall was shorter with AVS versus RVA pacing (20.4 ± 7.7 vs. 30.8 ± 11.6 [P = 0.01, GEE P = 0.07]). The interval between QRS onset to earliest free wall activation was shorter with AVS vs. RVA pacing (19.2 ± 6.4 ms vs. 31.1 ± 11.7 ms [P = 0.005, GEE P = 0.02]). Conclusion: The AVS was successfully paced in three dogs resulting in synchronous ventricular activation without crossing the TV. [source]

Can Simple Doppler Measurements Estimate Interatrial Conduction Time?

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1p2 2003
DRAGOS COZMA
COZMA, D., et al.: Can Simple Doppler Measurements Estimate Interatrial Conduction Time?Prolongation of the interatrial conduction time (ia-CT) is considered an important factor in the pathophysiology of atrial fibrillation (AF) and as a criterion to perform multisite atrial pacing. Measurement of ia-CT requires an electrophysiologic study. The aim of this study was to compare echocardiographic with electrophysiologic measurements to determine if they are correlated. Methods and Results: The study included 32 consecutive patients who underwent electrophysiologic studies. We measured ia-CT between the high right atrium and the distal coronary sinus. In all patients we measured P wave duration, left atrial diameter and area, and ia-CT by Doppler echocardiography was measured as the difference in time intervals between the QRS onset and the tricuspid A wave, and the QRS onset and the mitral A wave (DT). Ia-CT was statistically correlated with DT(r = 0.79, P < 0.0001), but not with P wave duration or left atrial dimensions. Conclusions: Measurement DT may be reliable to estimate ia-CT without invasive procedure. Accordingly, DT could be used as a simple selection criterion when considering patients for atrial resynchronization therapy. (PACE 2003; 26[Pt. II]:436,439) [source]

Automated QT Measurement and Application to Detection of Moxifloxacin-Induced Changes

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2009
David W. Mortara Ph.D.
Background: Concern for drug-induced QT prolongation has caused significant investment in QT measurement to safety-test new compounds. Manual methods are expensive and time-consuming. Reliable automatic methods would be highly desirable. Methods: Twelve-lead Holter recordings were annotated beat-to-beat by an automatic algorithm for global QRS onset and T offset. T offset was established from the time of peak T downslope plus a rate-dependent offset, analogous to the "tangent method," wherein T offset is determined by extrapolating the T downslope to an intersection with the baseline. Results and Conclusions: Variances of the beat-to-beat QT measurements were in the range 2.5,3.4 ms over three distinct databases, including a large heart failure database. Application to a moxifloxacin/placebo control database of 29 subjects showed excellent results. [source]

Methodology of QT-Interval Measurement in the Modular ECG Analysis System (MEANS)

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2009
Jan A. Kors Ph.D.
Background: QT prolongation as can be induced by drugs, signals the risk of life-threatening arrhythmias. The methodology of QT measurement in the modular ECG analysis system (MEANS) is described. Methods: In the simultaneously recorded leads of the standard 12-lead electrocardiogram (ECG), the QRS complexes are detected by a spatial velocity function. They are typed as dominant or nondominant, and a representative complex per lead is obtained by averaging over the dominant complexes. QRS onset and T end are determined by a template technique, and QT is measured. MEANS performance was evaluated on the 125 ECGs of the common standards for quantitative electrocardiography (CSE) multilead database, of which the waveform boundaries have been released. Results: MEANS detected correctly all 1445 complexes of the CSE library, with one false-positive detection due to a sudden baseline jump. All dominant complexes were correctly typed. The average of the differences between MEANS and reference was less than 2 ms (=1 sample) for both QRS onset and T end, and 2.1 ms for QT duration. The standard deviation of the differences was 3.8, 8.4, and 10.4 ms, respectively. Conclusions: A standard deviation of 10.4 ms for QT measurement seems large when related to the regulatory requirement that a prolongation as small as 5 ms should be detected. However, QT variabilities as encountered in different individuals will be larger than when measured in one individual during pharmacological intervention. Finally, if the U wave is part of the total repolarization, then T and U form a continuum and the end of T becomes questionable. [source]

Beat-to-Beat QT Interval Variability Is Primarily Affected by the Autonomic Nervous System

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 3 2008
Ph.D., Takanao Mine M.D.
Background: Beat-to-beat QT interval variability is associated with life-threatening arrhythmias and sudden death, however, its precious mechanism and the autonomic modulation on it remains unclear. The purpose of this study was to determine the effect of drugs that modulate the autonomic nervous system on beat-to-beat QT interval. Method: RR and QT intervals were determined for 512 consecutive beats during fixed atrial pacing with and without propranolol and automatic blockade (propranolol plus atropine) in 11 patients without structural heart disease. Studied parameters included: RR, QTpeak (QRS onset to the peak of T wave), QTend (QRS onset to the end of T wave) interval, standard deviation (SD) of the RR, QTpeak, and QTend (RR-SD, QTpeak-SD, and QTend-SD), coefficients of variation (RR- CV, QTpeak-CV, and QTend-CV) from time domain analysis, total power (TP; RR-TP, QTpeak-TP, and QTend-TP), and power spectral density of the low-frequency band (LF; RR-LF, QTpeak-LF, and QTend-LF) and the high-frequency band (HF; RR-HF, QTpeak-HF and QTend-HF). Results: Administration of propranolol and infusion of atropine resulted in the reduction of SD, CV, TP, and HF of the QTend interval when compared to controlled atrial pacing (3.7 ± 0.6 and 3.5 ± 0.5 vs 4.8 ± 1.4 ms, 0.9 ± 0.1 and 0.9 ± 0.1 vs 1.2 ± 0.3%, 7.0 ± 2.2 and 7.0 ± 2.2 vs 13.4 ± 8.1 ms2, 4.2 ± 1.4 and 4.2 ± 1.2 vs 8.4 ± 4.9 ms2, respectively). Administration of propranolol and atropine did not affect RR interval or QTpeak interval indices during controlled atrial pacing. Conclusions: Beat-to-beat QT interval variability is affected by drugs that modulate the autonomic nervous system. [source]

Electrocardiographic Quantitation of Heterogeneity of Ventricular Repolarization

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2000
Peter M. Okin M.D.
Background:QT interval dispersion (QTd) measured from the surface ECG has emerged as the most common noninvasive method for assessing heterogeneity of ventricular repolarization. Although QTd correlates with dispersion of monophasic action potential duration at 90% repolarization and with dispersion of recovery time recorded from the epicardium, total T-wave area, representing a summation of vectors during this time interval, has been shown to have the highest correlation with these invasive measures of dispersion of repolarization. However, recent clinical studies suggest that the ratio of the second to first eigenvalues of the spatial T-wave vector using principal component analysis (PCA ratio) may more accurately reflect heterogeneity of ventricular repolarization. Methods:To better characterize the ECG correlates of surface ECG measures of heterogeneity of ventricular repolarization and to establish normal values of these criteria using an automated measurement method, the relations of QRS onset to T-wave offset (QTod) and to T-wave peak (QTpd) dispersion and the PCA ratio to T-wave area and amplitude, heart rate, QRS axis and duration, and the QTo interval were examined in 163 asymptomatic subjects with normal resting ECGs and normal left ventricular mass and function. QTod and QTpd were measured by computer from digitized ECGs as the difference between the maximum and minimum QTo and QTp intervals, respectively. Results:In univariate analyses, a significant correlation was found between the sum of the T-wave area and the PCA ratio (R =,0.46, P < 0.001), but there was no significant correlation of the sum of T-wave area with QTod (R = 0.11, P = NS) or QTpd (R=0.09, P = NS). There were only modest correlations between QTod and QTpd (R = 0.45) and between the PCA ratio and QTod (R = 0.29) and QTpd (R = 0.49) (each P < 0.001). In stepwise multivariate linear regression analyses, the PCA ratio was significantly related to the sum of T-wave area, T-wave amplitude in aVL, and to female gender (overall R = 0.54, P < 0.001), QTod correlated only with the maximum QTo0 interval (R = 0.39, P < 0.001), and QTpd was related to heart rate and QRS axis (overall R = 0.36, P <0.001). In addition, the normal interlead dispersion of repolarization as measured by QTod was significantly greater than dispersion measured by QTod (23.5 ± 11.5 ms vs 18.3 ± 11.2 ms, P < 0.001). Conclusions: These findings provide new information on ECG measures of heterogeneity of repolarization in normal subjects, with a significantly higher intrinsic variability of Q to T-peak than Q to T-offset dispersion and only modest correlation between these wo measures. The independent relation of the PCA ratio to the sum of T-wave area suggests that the PCA ratio may be a more accurate surface ECG reflection of the heterogeneity of ventricular repolarizat on. A.N.E. 2000;5(1):79,87 [source]

PC-Based ECG Waveform Recognition,Validation of Novel Software Against a Reference ECG Database

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2009
Corina-Dana Dota M.D.
Background: PC-based ECG measurements must cope with normal as well as pathological ECGs in a reliable manner. EClysis, a software for ECG measurements was tested against reference values from the Common Standards for Quantitative Electrocardiography (CSE) database. Methods: Digital ECGs (12 leads, 500 Hz) were recorded by the CSE project. Data Set 3 contains reference values for 125 ECGs (33 normal and 92 pathological). Median values of measurements by 11 computer programs and by five cardiologists, respectively, refer to the earliest P and QRS onsets and to the latest P, QRS, and T offsets in any lead of a selected (index) beat. EClysis automatically measured all ECGs, without user interference. Results: The PQRST points were correctly detected but in two ECGs with AV block II,III. The software was not designed to detect atrial activity in atrial fibrillation (n = 9) and flutter (n = 1). In one case of atrial fibrillation, atrial activity interfered with positioning of QRS and T offsets. Regression coefficients between EClysis© and CSE (software-generated and human) were above 0.95 (P < 0.0001). The confidence intervals were 95% for the slope and the intercept of the regression lines. Conclusions: The PC-based detection and analysis of PQRST points showed a high level of agreement with the CSE database reference values. [source]