Showing papers on "QRS complex published in 2005"

Cardiac dyssynchrony analysis using circumferential versus longitudinal strain: implications for assessing cardiac resynchronization.

Abstract: Background— QRS duration is commonly used to select heart failure patients for cardiac resynchronization therapy (CRT). However, not all patients respond to CRT, and recent data suggest that direct assessments of mechanical dyssynchrony may better predict chronic response. Echo-Doppler methods are being used increasingly, but these principally rely on longitudinal motion (ell). It is unknown whether this analysis yields qualitative and/or quantitative results similar to those based on motion in the predominant muscle-fiber orientation (circumferential; ecc). Methods and Results— Both ell and ecc strains were calculated throughout the left ventricle from 3D MR-tagged images for the full cardiac cycle in dogs with cardiac failure and a left bundle conduction delay. Dyssynchrony was assessed from both temporal and regional strain variance analysis. CRT implemented by either biventricular (BiV) or left ventricular–only (LV) pacing enhanced systolic function similarly and correlated with improved dyssynchrony ...

Clinical and electrocardiographic predictors of a positive response to cardiac resynchronization therapy in advanced heart failure.

Abstract: Aims Cardiac resynchronization therapy (CRT) is an effective treatment for refractory congestive heart failure (CHF). However, up to 30% of patients do not respond to CRT. The aim of this study was to identify clinical and electrocardiographic (ECG) predictors of a positive response to CRT. Methods and results This retrospective study included 139 consecutive patients successfully implanted with a CRT device (mean age, 68±9 years, 113 men). At baseline, 69% of patients were in New York Heart Association (NYHA) functional class III, and 31% in class IV, mean left ventricular ejection fraction was 21±6%, and mean QRS duration was 188±28 ms. In each patient, left and right ventricular leads were placed to attain the shortest QRS duration during biventricular stimulation. Patients were classified at 6 months as responders to CRT ( n =100) if they were alive, they had not been re-hospitalized for management of CHF, and the NYHA class had decreased by 1 point, and/or peak VO2 or 6 min hall-walk increased by >10%. All others were classified as non-responders ( n =38; one patient was lost to follow-up). Uni- and multivariate logistic regression analyses were performed to detect a pre- or intra-operative predictor of a positive response to CRT. Among multiple demographic, clinical, and ECG variables, the amount of QRS shortening (ΔQRS) associated with biventricular stimulation was the only independent predictor of a positive (37±23 ms) vs. negative (11±23 ms) response to CRT ( P <0.001). Conclusion A positive response to CRT was observed in 73% of patients at 6 months and predicted only by ΔQRS.

Tricyclic antidepressant poisoning : cardiovascular toxicity.

Abstract: Tricyclic antidepressants remain a common cause of fatal drug poisoning as a result of their cardiovascular toxicity manifested by ECG abnormalities, arrhythmias and hypotension. Dosulepin and amitriptyline appear to be particularly toxic in overdose. The principal mechanism of toxicity is cardiac sodium channel blockade, which increases the duration of the cardiac action potential and refractory period and delays atrioventricular conduction. Electrocardiographic changes include prolongation of the PR, QRS and QT intervals, nonspecific ST segment and T wave changes, atrioventricular block, right axis deviation of the terminal 40ms vector of the QRS complex in the frontal plane (T 40ms axis) and the Brugada pattern (downsloping ST segment elevation in leads V1–V3 in association with right bundle branch block). Maximal changes in the QRS duration and the T 40ms axis are usually present within 12 hours of ingestion but may take up to a week to resolve. Sinus tachycardia is the most common arrhythmia due to anticholinergic activity and inhibition of norepinephrine uptake by tricyclic antidepressants but bradyarrhythmias (due to atrioventricular block) and tachyarrhythmias (supraventricular and ventricular) may occur. Torsade de pointes occurs uncommonly. Hypotension results from a combination of reduced myocardial contractility and reduced systemic vascular resistance due to α-adrenergic blockade. Life-threatening arrhythmias and death due to tricyclic antidepressant poisoning usually occurs within 24 hours of ingestion. Rapid deterioration is common. Level of consciousness at presentation is the most sensitive clinical predictor of serious complications. Although a QRS duration >100ms and a rightward T 40ms axis appear to be better predictors of cardiovascular toxicity than the plasma tricyclic drug concentration, they have at best moderate sensitivity and specificity for predicting complications.

Characteristic wave detection in ECG signal using morphological transform

Abstract: Background Detection of characteristic waves, such as QRS complex, P wave and T wave, is one of the essential tasks in the cardiovascular arrhythmia recognition from Electrocardiogram (ECG).

Heart rate variability measurements and the prediction of ventricular arrhythmias.

Abstract: Heart rate variability (HRV) is the temporal variation between sequences of consecutive heartbeats. On a standard electrocardiogram (ECG), the maximum upwards deflection of a normal QRS complex is at the peak of the R wave (Figure 1), and the duration between two adjacent R wave peaks is termed the R-R interval. The ECG signal requires editing before HRV analysis can be performed, a process requiring the removal of all non-sinus-node-originating beats. The resulting period between adjacent QRS complexes resulting from sinus node depolarizations is termed the N-N (normal-normal) interval.1 HRV is the measurement of the variability of the N-N intervals. Figure 1. The normal electrocardiogram with component waves labelled. Although counter-intuitive, it is possible that HRV confers a survival advantage. Any system exhibiting intrinsic variability is primed to respond rapidly and appropriately to demands placed upon it. HRV is a measure of the balance between sympathetic mediators of heart rate (HR) (i.e. the effect of epinephrine and norepinephrine, released from sympathetic nerve fibres, acting on the sino-atrial and atrio-ventricular nodes), which increase the rate of cardiac contraction and facilitate conduction at the atrio-ventricular node, and parasympathetic mediators of HR (i.e. the influence of acetylcholine, released by the parasympathetic nerve fibres, acting on the sino-atrial and atrio-ventricular nodes), leading to a decrease in the HR and a slowing of conduction at the atrio-ventricular node. Sympathetic mediators appear to exert their influence over longer time periods and are reflected in the low frequency power (LFP) of the HRV spectrum (between 0.04 Hz and 0.15 Hz.2,,3 Vagal mediators exert their influence more quickly on the heart, and principally affect the high frequency power (HFP) of the HRV spectrum (between 0.15 Hz and 0.4 Hz).4 Thus, at any point in time, the LFP:HFP ratio is a proxy for the sympatho-vagal balance. Physiological and pathological process … Address correspondence to Dr M.J. Reed, Emergency Department, Royal Infirmary of Edinburgh, 51 Little France Crescent, Edinburgh EH16 4SA. e-mail: mattreed1{at}hotmail.com

Utility of Echocardiographic Radial Strain Imaging to Quantify Left Ventricular Dyssynchrony and Predict Acute Response to Cardiac Resynchronization Therapy

Abstract: Echocardiographic strain imaging was used to quantify radial mechanical dyssynchrony in 38 patients who underwent cardiac resynchronization therapy. Dyssynchrony, defined as the time difference of peak radial strain in the septum versus the posterior wall, was significantly greater in patients with acute hemodynamic responses, and changes in radial dyssynchrony correlated with changes in stroke volume. A ≥130-ms difference in septal versus posterior wall peak strain when combined with a favorable left ventricular lead position was strongly predictive of immediate improvement in stroke volume with resynchronization therapy (95% sensitivity, 88% specificity), regardless of electrocardiographic QRS duration.

Obesity and the electrocardiogram.

Abstract: Obesity is associated with a wide variety of electrocardiographic (ECG) abnormalities. Most of these reflect alterations in cardiac morphology. Some serve as markers of risk for sudden death. Key ECG abnormalities or alterations occurring with disproportionately high frequency in obese subjects include: leftward shifts of the P wave QRS and T wave axes, various changes in P wave morphology, low QRS voltage, various markers of left ventricular hypertrophy (particularly the Cornell voltage and product), T wave flattening in the inferior and lateral leads, lengthening of the corrected QT interval and prolonged QT interval duration. Alterations in the signal-averaged ECG and in heart rate variability may be arrhythmogenic. Cardiac arrhythmias have been described in obese subjects, but are often accompanied by left ventricular hypertrophy or the sleep apnea syndrome. Many of these ECG abnormalities are reversible with substantial weight loss. Thus, obesity is associated with a wide variety of ECG abnormalities, many of which are corrected by weight loss.

A Feasible Approach for Direct His‐Bundle Pacing Using a New Steerable Catheter to Facilitate Precise Lead Placement

Abstract: Introduction: Much clinical evidence has shown that right ventricular (RV) apical pacing is detrimental to left ventricular function Preservation of the use of the His-Purkinje (H-P) system may be ideal in heart block that is restricted to the AV node, but may be of no benefit when H-P disease exists Aim: To investigate the feasibility of direct His-bundle pacing (DHBP) using a new system consisting of a steerable catheter and a new 41 F screw-in lead Method: Between May and December 2004, 26 patients (19 male, mean age: 77 ± 5 years) with a standard pacemaker (PM) indication and preserved His-bundle conduction were enrolled and DHBP was attempted Results: DHBP was achieved in 24 patients (92%); two patients were paced in the His area, but the paced QRS morphology and duration were different from the native QRS The mean time for lead positioning was 19 ± 17 minutes, the mean fluoroscopy time was 11 ± 8 minutes, and the total procedure time (skin-to-skin including positioning of a quadripolar diagnostic catheter for His recording) was 75 ± 18 minutes In DHBP pacing, the acute pacing threshold was 23 ± 10 V at a pulse duration of 05 msec, and the sensed potentials were 29 ± 20 mV At a 3-month follow-up examination, the same QRS duration and morphology recorded on implantation were observed in all patients The pacing threshold was 28 ± 14 V, and sensed potentials were 25 ± 18 mV; the sensing configuration was changed from bipolar to unipolar in 6 patients to resolve undersensing issues No major complications were observed Conclusions: This feasibility study shows that DHBP can be accomplished with a new system consisting of a steerable catheter and an active fixation lead in 92% of the patients in whom it was attempted

Surgical epicardial left ventricular lead versus coronary sinus lead placement in biventricular pacing

Abstract: Objective: Biventricular pacing has demonstrated improvement in cardiac function in treating congestive heart failure (CHF). Two different operative strategies (coronary sinus vs. epicardial stimulation) for left ventricular (LV) pacing were compared. Methods: Since April 1999, a total of 86 patients (pts, age: 63G10 years) with depressed systolic LV function (mean ejection fraction 24G9%), left bundle-branch-block (mean QRS 182G22 ms) and congestive heart failure NYHA III or higher were e nrolled. For biventricular stimulation coronary sinus (CS) leads were placed in 79 pts. Nine of these devices were converted to surgical epicardial LV-leads, because of CS-lead failure. In 7 patients epicardial LV-leads were initially implanted surgically, accounting for a total of 16 pts with surgical placed epicardial steroid-eluting LV-leads. For these ,a limited left-lateral thoracotomy (7G4 cm) was used. Thirty-three (38%) pts had an indication for a defibrillator. The mean follow-up time was 16.4G15.4 months (0.1‐45 months), representing 107.1 patient-years. Results: In the biventricular pacing mode, QRS duration decreased to 143G16 ms (P!0.001). Threshold capture of the CS-leads increased significantly compared to surgically placed epicardial leads (18 month control: 2.2G1.4 V/0.5 ms vs. 0.7G0.3 V/0.5 ms), which had no increase in threshold (P!0.001). At the 18 month follow-up 7 CS-leads had a threshold of O4 V/0.5 ms vs. epicardial leads which were under 1.1 V/0.5 ms, except for one (1.8 V/0.5 ms). After CS-lead implantation 25 LVlead related complications occurred, (failed implantation, CS-dissection, loss of pacing capture, diaphragm stimulation or lead dislodgment), vs. one dislodgement after surgical epicardial lead placement (P!0.05). Correct lead positioning (obtuse marginal branch area) was achieved in all surgical epicardial placements but only in 70% with CS-leads (P!0.03). In the follow up period, 9 pts died (4 cardiac related). Heart transplantation was necessary in 4 pts due to deterioration of the cardiomyopathy. Conclusions: Surgical epicardial lead placement revealed excellent long-term results and a lower LV-related complication rate compared to CS-leads. Although, the approach via limited thoracotomy for biventricular pacing is associated with ‘more surgery’, it is a safe and reliable technique and should be considered as an equal alternative. q 2004 Elsevier B.V. All rights reserved.

Frequency of left ventricular dyssynchrony in patients with heart failure and a narrow QRS complex.

Abstract: Cardiac resynchronization therapy (CRT) is considered a major advance in the treatment of patients with heart failure. The presence of left ventricular (LV) dyssynchrony seems mandatory for a positive response to CRT. Currently, only patients with wide QRS complexes are considered for CRT, although patients with narrow QRS complexes may also have LV dyssynchrony. In the present study, the incidence of LV dyssynchrony was prospectively evaluated in 64 patients with heart failure and narrow QRS complexes using tissue Doppler imaging.

Electrocardiographic characteristics of repetitive monomorphic right ventricular tachycardia originating near the His-bundle.

Abstract: Introduction: Most idiopathic nonreentrant ventricular tachycardia (VT) and ventricular premature contractions (VPCs) arise from the right or left ventricular outflow tract (OT). However, some right ventricular (RV) VT/VPCs originate near the His-bundle region. The aim of this study was to investigate ECG characteristics of VT/VPCs originating near the His-bundle in comparison with right ventricular outflow tract (RVOT)-VT/VPCs. Methods and Results: Ninety RV-VT/VPC patients underwent catheter mapping and radiofrequency ablation. ECG variables were compared between VT/VPCs originating from the RVOT and near the His-bundle. Ten patients had foci near the His-bundle (HIS group), with the His-bundle local ventricular electrogram preceding the QRS onset by 15–35 msec (mean: 22 msec) and His-bundle pacing produced a nearly identical ECG to clinical VT/VPCs. The HIS group R wave amplitude in the inferior leads (lead III: 1.0 ± 0.6 mV) was significantly lower than that of the RVOT group (1.7 ± 0.4 mV, P < 0.05). An R wave in aVL was present in 6 of 10 HIS group patients, while almost all RVOT group patients had a QS pattern in aVL. Lead I in HIS group exhibited significantly taller R wave amplitudes than RVOT group. HIS group QRS duration in the inferior leads was shorter than that of the RVOT group. Eight of 10 HIS group patients exhibited a QS pattern in lead V1 compared to 14 of 81 RVOT group patients. HIS group had larger R wave amplitudes in leads V5 and V6 than RVOT group. Conclusion: VT/VPCs originating near the His-bundle have distinctive ECG characteristics. Knowledge of the characteristic QRS morphology may facilitate catheter mapping and successful ablation.

ECG Repolarization Waves: Their Genesis and Clinical Implications

Abstract: The electrocardiographic (ECG) manifestation of ventricular repolarization includes J (Osborn), T, and U waves. On the basis of biophysical principles of ECG recording, any wave on the body surface ECG represents a coincident voltage gradient generated by cellular electrical activity within the heart. The J wave is a deflection with a dome that appears on the ECG after the QRS complex. A transmural voltage gradient during initial ventricular repolarization, which results from the presence of a prominent action potential notch mediated by the transient outward potassium current (I(to)) in epicardium but not endocardium, is responsible for the registration of the J wave on the ECG. Clinical entities that are associated with J waves (the J-wave syndrome) include the early repolarization syndrome, the Brugada syndrome and idiopathic ventricular fibrillation related to a prominent J wave in the inferior leads. The T wave marks the final phase of ventricular repolarization and is a symbol of transmural dispersion of repolarization (TDR) in the ventricles. An excessively prolonged QT interval with enhanced TDR predisposes people to develop torsade de pointes. The malignant "R-on-T" phenomenon, i.e., an extrasystole that originates on the preceding T wave, is due to transmural propagation of phase 2 reentry or phase 2 early afterdepolarization. A pathological "U" wave as seen with hypokalemia is the consequence of electrical interaction among ventricular myocardial layers at action potential phase 3 of which repolarization slows. A physiological U wave is thought to be due to delayed repolarization of the Purkinje system.

Reduction of QRS duration after pulmonary valve replacement in adult fallot patients is related to reduction of right ventricular volume

Abstract: Aims Late after total correction, Fallot patients with a long QRS duration are prone to serious arrhythmias and sudden cardiac death. Pulmonary regurgitation is a common cause of right ventricular (RV) failure and QRS lengthening. We studied the effects of pulmonary valve replacement (PVR) on QRS duration and RV volume. Methods and results Twenty-six consecutive Fallot patients were evaluated both pre-operatively and 6–12 months post-operatively by cardiac magnetic resonance (CMR). In this study, we present the computer-assisted analysis of the standard 12-lead electrocardiograms closest in time to the CMR studies. For the whole group, QRS duration shortened by 6±8 ms, from 151±30 to 144±29 ms ( P =0.002). QRS duration decreased in 18 of 26 patients by 10±6 ms, from 152±32 to 142±31 ms. QRS duration remained constant or increased slightly in eight of 26 patients by 3±3 ms, from 148±27 to 151±25 ms. CMR showed a decrease in RV end-diastolic volume from 305±87 to 210±62 mL ( P =0.000004). QRS duration changes correlated with RV end-diastolic volume changes ( r =0.54, P =0.01). Conclusion Our study shows that PVR reduces QRS duration. The amount of QRS reduction is related to the success of the operation, as expressed by the reduction in RV end-diastolic volume.

Idiopathic Left Ventricular Tachycardia Originating from the Mitral Annulus

Abstract: Background: Radiofrequency catheter ablation (RFCA) can eliminate most idiopathic repetitive monomorphic ventricular tachycardias (RMVTs) originating from the right and left ventricular outflow tracts (RVOT, LVOT). Here, we describe the electrophysiological (EP) findings of a new variant of RMVT originating from the mitral annulus (MAVT). Methods and Results: MAVT was identified in 35 patients out of 72 consecutive left ventricular RMVTs from May 2000 to June 2004. All patients underwent an EP study and RFCA. The sites of origin of the MAVT were grouped into four groups according to the successful ablation sites around the mitral annulus. Group I included the anterior sites (n = 11), group II the anterolateral sites (n = 9), group III the lateral sites (n = 6), and group IV the posterior sites (n = 9). The MAVTs were a wide QRS tachycardia with a delta wave-like beginning of the QRS complex. The transitional zone of the R wave occurred between V1-V2 in all cases. The 12-lead electrocardiogram (ECG) pattern might reflect the site of the origin of MAVTs around the mitral annulus. We proposed an algorithm for predicting the site of the focus and the tactics needed for successful RFCA of the MAVT. Conclusions: We described the EP findings of the new variant of RMVT, MAVT. Most MAVTs could be eliminated by RF applications to the endocardial mitral annulus using our proposed tactics.

T-Vector Direction Differentiates Postpacing From Ischemic T-Wave Inversion in Precordial Leads

Abstract: Background— Postpacing precordial T-wave inversion (TWI), known as cardiac memory (CM), mimics ischemic precordial TWI, and there are no established ECG criteria that adequately distinguish between the two. On the basis of CM properties (postpacing sinus rhythm T vector approaching the direction of the paced QRS vector), we hypothesized that CM induced by right ventricular pacing would manifest a TWI pattern different from that of precordial ischemic TWI, thereby discriminating between the two. Methods and Results— T-wave axis, polarity, and amplitude on a 12-lead ECG during sinus rhythm were compared between CM and ischemic patients. The CM group incorporated 13 patients who were paced in DDD mode with short atrioventricular delay for 1 week after elective pacemaker implantation. The ischemic group consisted of 47 patients with precordial TWI identified among 228 consecutive patients undergoing percutaneous coronary intervention for an acute coronary syndrome. The combination of (1) positive TaVL, (2) po...

Using correlation coefficient in ecg waveform for arrhythmia detection

Abstract: Arrhythmia is one kind of diseases that gives rise to the death and possibly forms the immedicable danger. The most common cardiac arrhythmia is the ventricular premature beat. The main purpose of this study is to develop an efficient arrhythmia detection algorithm based on the morphology characteristics of arrhythmias using correlation coefficient in ECG signal. Subjects for experiments included normal subjects, patients with atrial premature contraction (APC), and patients with ventricular premature contraction (PVC). So and Chan's algorithm was used to find the locations of QRS complexes. When the QRS complexes were detected, the correlation coefficient and RR-interval were utilized to calculate the similarity of arrhythmias. The algorithm was tested using MIT-BIH arrhythmia database and every QRS complex was classified in the database. The total number of test data was 538, 9 and 24 for normal beats, APCs and PVCs, respectively. The results are presented in terms of, performance, positive predication and sensitivity. High overall performance (99.3%) for the classification of the different categories of arrhythmic beats was achieved. The positive prediction results of the system reach 99.44%, 100% and 95.35% for normal beats, APCs and PVCs, respectively. The sensitivity results of the system are 99.81%, 81.82% and 95.83% for normal beats, APCs and PVCs, respectively. Results revealed that the system is accurate and efficient to classify arrhythmias resulted from APC or PVC. The proposed arrhythmia detection algorithm is therefore helpful to the clinical diagnosis.