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Leads II (lead + ii)

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Medical Sciences	100%

Selected Abstracts

Comparing Methods of Measurement for Detecting Drug-Induced Changes in the QT Interval: Implications for Thoroughly Conducted ECG Studies

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2004
Nkechi E. Azie M.D.
Background:,The aim of this study was to compare the reproducibility and sensitivity of four commonly used methods for QT interval assessment when applied to ECG data obtained after infusion of ibutilide. Methods:,Four methods were compared: (1) 12-lead simultaneous ECG (12-SIM), (2) lead II ECG (LEAD II), both measured on a digitizing board, (3) 3-LEAD ECG using a manual tangential method, and (4) a computer-based, proprietary algorithm, 12SLÔ ECG Analysis software (AUT). QT intervals were measured in 10 healthy volunteers at multiple time points during 24 hours at baseline and after single intravenous doses of ibutilide 0.25 and 0.5 mg. Changes in QT interval from baseline were calculated and compared across ECG methods, using Bland,Altman plots. Variability was studied using a mixed linear model. Results:,Baseline QT values differed between methods (range 376,395 ms), mainly based on the number of leads incorporated into the measurement, with LEAD II and 3-LEAD providing the shortest intervals. The 3-LEAD generated the largest QT change from baseline, whereas LEAD II and 12-SIM generated essentially identical result within narrow limits of agreement (0.4 ms mean difference, 95% confidence interval ± 20.5 ms). Variability with AUT (standard deviation 15.8 ms for within-subject values) was clearly larger than with 3-LEAD, LEAD II, and 12-SIM (9.6, 10.0, and 11.3 ms). Conclusion:,This study demonstrated significant differences among four commonly used methods for QT interval measurement after pharmacological prolongation of cardiac repolarization. Observed large differences in variability of measurements will have a substantial impact on the sample size required to detect QT prolongation in the range that is currently advised in regulatory guidance. [source]

R-wave Amplitude in Lead II of an Electrocardiograph Correlates with Central Hypovolemia in Human Beings

ACADEMIC EMERGENCY MEDICINE, Issue 10 2006
John G. McManus MD
Abstract Objectives Previous animal and human experiments have suggested that reduction in central blood volume either increases or decreases the amplitude of R waves in various electrocardiograph (ECG) leads depending on underlying pathophysiology. In this investigation, we used graded central hypovolemia in adult volunteer subjects to test the hypothesis that moderate reductions in central blood volume increases R-wave amplitude in lead II of an ECG. Methods A four-lead ECG tracing, heart rate (HR), estimated stroke volume (SV), systolic blood pressure, diastolic blood pressure, and mean arterial pressure were measured during baseline supine rest and during progressive reductions of central blood volume to an estimated volume loss of >1,000 mL with application of lower-body negative pressure (LBNP) in 13 healthy human volunteer subjects. Results Lower-body negative pressure resulted in a significant progressive reduction in central blood volume, as indicated by a maximal decrease of 65% in SV and maximal elevation of 56% in HR from baseline to ,60 mm Hg LBNP. R-wave amplitude increased (p < 0.0001) linearly with progressive LBNP. The amalgamated correlation (R2) between average stroke volume and average R-wave amplitude at each LBNP stage was ,0.989. Conclusions These results support our hypothesis that reduction of central blood volume in human beings is associated with increased R-wave amplitude in lead II of an ECG. [source]

The Morphology Changes in Limb Leads after Ablation of Verapamil-Sensitive Idiopathic Left Ventricular Tachycardia and Their Correlation with Recurrence

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2008
SHU-YUAN YAO Ph.D
Objectives: This study was designed to explore the morphology changes in limb leads of ECGs after successful ablation of verapamil sensitive idiopathic left ventricular tachycardia (ILVT) and their correlation with tachycardia recurrence. Methods: Between January 2001 and December 2006, 116 patients who underwent successful ablation of ILVT were included in the study. Twelve-lead surface ECG recordings during sinus rhythm were obtained in all patients before and after ablation to compare morphology changes in limb leads. Results: The ECG morphology changes after ablation were divided into two categories: one with new or deepening Q wave in inferior leads and/or disappearance of Q wave in leads I and aVL, and the other without change. The changes in any Lead II, III, or aVF after ablation occurred significantly more in patients without recurrence of ventricular tachycardia (VT) (P < 0.0001, 0.002, and 0.0001, respectively). The patients with recurrence of VT tended to have no ECG changes, compared with those without recurrence of VT (P = 0.009). The sensitivity of leads II, III, and aVF changes in predicting nonrecurrence VT were 66.7%, 78.7%, and 79.6%, specificity were 100%, 75%, and 87.5%, and nonrecurrence predictive value of 100%, 97.7%, and 98.9%, respectively. When inferior leads changes were combined, they could predict all nonrecurrence patients with 100% specificity. Conclusions: Successful radiofrequency ablation of ILVT could result in morphology changes in limb leads of ECG, especially in inferior leads. The combined changes in inferior leads can be used as an effective endpoint in ablation of this ILVT. [source]

R-wave Amplitude in Lead II of an Electrocardiograph Correlates with Central Hypovolemia in Human Beings

Influence of Drive Cycle Length on Initiation of Ventricular Fibrillation During Implantable Cardioverter Defibrillator Threshold Testing

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2006
NEIL K. SANGHVI
Background: Programmed electrical stimulation of the heart as a method to induce tachyarrhythmias has been described since the 1960s. To date, no study has examined optimal drive cycle length in the induction of ventricular fibrillation (VF) during defibrillation threshold testing after implantable cardioverter-defibrillator placement. We hypothesized that longer drive cycle length, by means of the longer action potential duration, would promote intramyocardial phase 2 reentry and facilitate induction of VF. Methods: Fifty consecutive implants were randomized in a prospective crossover format for this study. The group consisted of 40 men and 10 women, with each patient receiving either a 400 or 600 ms initial drive train prior to 1.2 J internal shock on the T wave with a goal to induce ventricular fibrillation. The timing of the T wave shock was determined by measuring the interval from the beginning of the QRS to the apex of the T wave in lead II. Successful inductions were defibrillated via the cardioverter defibrillator. Patients were then crossed over and the protocol repeated. Results: Twenty of 23 (87%) patients were successfully induced into VF in the initial 400 ms drive train arm whereas 22 of 27 (81%) were successfully induced in the 600 ms arm. Thus, a total of 44 (88%) patients were successfully induced at 400 ms, 41 (82%) patients were successfully induced at 600 ms, and 2 (4%) patients were not inducible at either cycle length, but were inducible with 50 Hz ventricular stimulation. However, no significant difference was noted between the two groups. Conclusion: No investigation to date has questioned whether a relationship exists between drive cycle length and initiation of ventricular fibrillation. Our study addresses this question, though negative for difference between 400 and 600 ms drive trains. Further research into optimal strategies for inducing ventricular fibrillation will minimize patient sedation time and discomfort while undergoing defibrillator threshold testing. [source]

Behavior of the Electrocardiographic T Peak to End Interval in Childhood

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2010
Abraham Benatar M.B., Ch.B., F.A.C.C., F.C.P.(S.A.), Ph.D.
Background: The T-wave peak to T-wave end (TpTe) interval reflects spatial and transmural dispersion in repolarization and serves as an arrhythmogenic index. Normal TpTe interval data in children are lacking. We evaluated the effects of age, gender, heart rate, leads (II and V5) on TpTe and T-wave voltage. Methods: Four hundred healthy children (age 4 days to 16.7 years) were enrolled. From a resting 12-lead digital ECG, TpTe, RR, QT, JT intervals, and T amplitude were measured (leads II and V5). Bazett and Fridericia formulas were applied to TpTe for heart rate correction and TpTe/QT and TpTe/JT were calculated. Descriptive and analytical statistics were applied, significance level set at P , 0.05. Results: TpTe in leads II and V5 correlate well. Contrary to adults, no gender differences in TpTe were observed in childhood. TpTe lengthens with increasing age, and is inversely related to heart rate. TpTe 98th percentile is 85 msec in first 5 years, increasing to 92 msec in adolescence. TpTe Fridericia is a good correction formula in childhood; TpTe Bazett overcorrects in the younger age. TpTe/QT and TpTe/JT are longer in younger subjects due to greater QT shortening than the TpTe interval at higher heart rates. Conclusions: In children, TpTe in lead II and V5 correlate well. The TpTe interval lengthens with advancing age as heart rate diminishes. TpTe Fridericia is a good correction formula in children. Younger subjects have higher TpTe/QT and TpTe/JT indices compared to older children. T-wave voltage increases with age, tallest in the 5,10-year-age group particularly in V5. Ann Noninvasive Electrocardiol 2010;15(1):11,16 [source]

The Morphology Changes in Limb Leads after Ablation of Verapamil-Sensitive Idiopathic Left Ventricular Tachycardia and Their Correlation with Recurrence

P Wave Duration and Morphology Predict Atrial Fibrillation Recurrence in Patients with Sinus Node Dysfunction and Atrial-Based Pacemaker

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 11 2002
ANTONIO DE SISTI
DE SISTI, A., et al.: P Wave Duration and Morphology Predict Atrial Fibrillation Recurrence in Patients with Sinus Node Dysfunction and Atrial-Based Pacemaker. P wave duration and morphology have never been systematically evaluated as markers of AF in patients with a conventional indication to pacing. This study correlated sinus P wave duration and morphology and the incidence of AF in patients with sinus node dysfunction (SND), previous history of AF before implant, and atrial-based pacemaker. Included were 140 patients (86 men, 54 women; mean age 71.8 ± 10.4 years) with recurrent paroxysmal AF and who received a DDD (128 patients) or AAI (12 patients) pacemaker for SND. Forty-nine patients had structural heart disease. Sinus P wave duration and morphology was evaluated in leads II, III. Twenty-two patients had an abnormal P wave morphology, diphasic (+/-) in 5 and notched (+/+) in 17. The basic pacemaker rate was programmed between 60 and 70 beats/min. Rate responsive function was activated in 65 patients. During a follow-up of 27.6 ± 17.8 months, AF was documented in 87 patients. Forty-four patients developed permanent AF, following at least one episode of paroxysmal AF in 26 cases. Statistical analysis used Cox model regression. Univariate predictors of AF (P < 0.10) were drugs (mean: 2 ± 1.4) and DC shock before pacing (16/140 patients), P wave duration (mean 112.5 ± 24.6 ms), basic pacemaker rate (mean 68 ± 5 beats/min), and drugs in the follow-up (mean 1.2 ± 0.94). Multivariate analysis showed that P wave duration (b = 0.013, s.e. = 0.004; P = 0.003), and drugs before pacing (b = 0.2; s.e.= 0.08; P < 0.01) resulted in a significant independent predictor of AF. Actuarial incidence of patients free of AF at 30 months was 35%: 56% in patients with a P wave < 120 ms, and 13% in those with P wave , 120 ms (P < 0.01 by Score test). Univariate predictors of permanent AF were drugs and DC shock before pacing, left atrial size (mean 39 ± 6 mm), P wave duration, abnormal P wave morphology (22/140 patients), and drugs in the follow-up. Multivariate analysis showed that P wave morphology was the most important predictor of permanent AF (b = - 0.56, s.e.= 0.2; P = 0.008). Incidence of patients free of permanent AF at 30 months was 69%: 74% in patients with normal P wave, compared to 28% in the case of abnormal P wave morphology (P < 0.01). P wave duration and morphology are good markers of postpacing AF recurrence in patients with SND and an atrial-based pacemaker. This observation suggests that intra- and interatrial conduction disturbances be extensively evaluated before implantation, and the indication for atrial resynchronization procedures be reevaluated. [source]

Electrocardiographic Differentiation between Acute Pulmonary Embolism and Non-ST Elevation Acute Coronary Syndromes at the Bedside

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2010
Krzysztof Jankowski M.D., Ph.D.
Background: Clinical picture of acute pulmonary embolism (APE), with wide range of electrocardiographic (ECG) abnormalities can mimic acute coronary syndromes. Objectives: Assessment of standard 12-lead ECG usefulness in differentiation at the bedside between APE and non-ST elevation acute coronary syndrome (NSTE-ACS). Methods: Retrospective analysis of 143 patients: 98 consecutive patients (mean age 63.4 ± 19.4 year, 45 M) with APE and 45 consecutive patients (mean age 72.8 ± 10.8 year, 44 M) with NSTE-ACS. Standard ECGs recorded on admission were compared in separated groups. Results: Right bundle branch block (RBBB) and S1S2S3 or S1Q3T3 pattern were found in similar frequency in both groups (10 [11%] APE patients vs 6 [14%] NSTE-ACS patients, 27 [28%] patients vs 7 [16%] patients, respectively, NS). Negative T waves in leads V1-3 together with negative T waves in inferior wall leads II, III, aVF (OR 1.3 [1.14,1.68]) significantly indicated APE with a positive predictive value of 85% and specificity of 87%. However, counterclockwise axis rotation (OR 4.57 [2.74,7.61]), ventricular premature beats (OR 2.60 [1.60,4.19]), ST depression in leads V1-3 (OR 2.25 [1.43,3.56]), and negative T waves in leads V5-6 (OR 2.08 [1.31,3.29]) significantly predicted NSTE-ACS. Conclusions: RBBB, S1S2S3, or S1Q3T3 pattern described as characteristic for APE were not helpful in the differentiation between APE and NSTE-ACS in studied group. Coexistence of negative T waves in precordial leads V1-3 and inferior wall leads may suggest APE diagnosis. Ann Noninvasive Electrocardiol 2010;15(2):145,150 [source]

Behavior of the Electrocardiographic T Peak to End Interval in Childhood

The Measurement of the QT and QTc on the Neonatal and Infant Electrocardiogram: A Comprehensive Reliability Assessment

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2009
B.S., Robert M. Gow M.B.
Background: An electrocardiogram has been proposed to screen for prolonged QT interval that may predispose infants to sudden death in the first year of life. Understanding the reliability of QT interval measurement will inform the design of a screening program. Methods: Three pediatric cardiologists measured the QT/RR intervals on 60 infant electrocardiograms (median age 46 days), from leads II, V5 and V6 on three separate occasions, 7 days apart, according to a standard protocol. The QTc was corrected by Bazett's (QTcB), Fridericia's (QTCFrid), and Hodges' (QTcH) formulae. Intraobserver and interobserver reliability were assessed by intraclass correlation coefficients (ICC), limits of agreement and repeatability coefficients for single, average of two and average of three measures. Agreement for QTc prolongation (> 440 msec) was assessed by kappa coefficients. Results: QT interval intraobserver ICC was 0.86 and repeatability coefficient was 25.9 msec; interobserver ICC increased from 0.88 for single observations to 0.94 for the average of 3 measurements and repeatability coefficients decreased from 22.5 to 16.7 msec. For QTcB, intraobserver ICC was 0.67, and repeatability was 39.6 msec. Best interobserver reliability for QTcB was for the average of three measurements (ICC 0.83, reproducibility coefficient 25.8 msec), with further improvement for QTcH (ICC 0.92, reproducibility coefficient 16.69 msec). Maximum interobserver kappa for prolonged QTc was 0.77. Misclassification around specific cut points occurs because of the repeatability coefficients. Conclusions: Uncorrected QT measures are more reliable than QTcB and QTCFrid. An average of three independent measures provides the most reliable QT and QTc measurements, with QTcH better than QTcB. [source]