Showing papers on "QRS complex published in 1996"

Cellular Basis for the Electrocardiographic J Wave

Abstract: Background The J wave is a deflection that appears in the ECG as a late delta wave following the QRS or as a small secondary R wave (R′). Also referred to as an Osborn wave, the J wave has been observed in the ECG of animals and humans for more than four decades, yet the mechanism underlying its manifestation is poorly understood. The present study investigates the cellular basis for the J wave using an isolated arterially perfused preparation consisting of a wedge of canine right or left ventricle. Methods and Results A 12-lead ECG was initially recorded in vivo. After isolation and arterial perfusion of the right or left ventricular wedge, transmembrane action potentials were simultaneously recorded from epicardial, M region, and endocardial transmural sites with three floating microelectrodes. A transmural ECG was recorded concurrently. A J wave was observed at the R-ST junction of the ECG in 17 of 20 adult dogs, usually in leads II, III, aVR, and aVF and the mid to lateral precordial leads. The J wave...

Cellular Basis for the Electrocardiographic J Wave

Abstract: Background The J wave is a deflection that appears in the ECG as a late delta wave following the QRS or as a small secondary R wave (R′). Also referred to as an Osborn wave, the J wave has been observed in the ECG of animals and humans for more than four decades, yet the mechanism underlying its manifestation is poorly understood. The present study investigates the cellular basis for the J wave using an isolated arterially perfused preparation consisting of a wedge of canine right or left ventricle. Methods and Results A 12-lead ECG was initially recorded in vivo. After isolation and arterial perfusion of the right or left ventricular wedge, transmembrane action potentials were simultaneously recorded from epicardial, M region, and endocardial transmural sites with three floating microelectrodes. A transmural ECG was recorded concurrently. A J wave was observed at the R-ST junction of the ECG in 17 of 20 adult dogs, usually in leads II, III, aVR, and aVF and the mid to lateral precordial leads. The J wave...

Classification of cardiac arrhythmias using fuzzy ARTMAP

Abstract: The authors have investigated the QRS complex, extracted from electrocardiogram (EGG) data, using fuzzy adaptive resonance theory mapping (ARTMAP) to classify cardiac arrhythmias. Two different conditions have been analyzed: normal and abnormal premature ventricular contraction (PVC). Based on MIT/BIH database annotations, cardiac beats for normal and abnormal QRS complexes were extracted from this database, scaled, and Hamming windowed, after bandpass filtering, to yield a sequence of 100 samples for each QRS segment. From each of these sequences, two linear predictive coding (LPC) coefficients were generated using Burg's maximum entropy method. The two LPC coefficients, along with the mean-square value of the QRS complex segment, were utilized as features for each condition to train and test a fuzzy ARTMAP neural network for classification of normal and abnormal PVC conditions. The test results show that the fuzzy ARTMAP neural network can classify cardiac arrhythmias with greater than 99% specificity and 97% sensitivity.

Anatomic Substrate for Idiopathic Left Ventricular Tachycardia

Abstract: Background Idiopathic left ventricular tachycardia (ILVT) characterized by QRS complexes with right bundle-branch block (RBBB) morphology and left axis deviation is a distinct clinical syndrome that also demonstrates a characteristic response to verapamil and inducibility from the atrium in patients without structural heart disease. A false tendon has been described in the left ventricle in a patient with ILVT in whom surgical resection of the false tendon resulted in cure. We hypothesized that the false tendon is responsible for the genesis of similar ventricular tachycardia (VT) in others. Methods and Results We performed transthoracic (TTE) and/or transesophageal (TEE) two-dimensional echocardiograms in 15 patients undergoing catheter ablation for ILVT. There were 12 men and 3 women (mean age, 31±12 years, with average symptom duration of 11±9 years). The mean VT cycle length was 360±70 ms, and all had RBBB morphology with left axis deviation. Cardiac chamber sizes, left ventricular wall thickness, and...

Adaptive estimation of QRS complex wave features of ECG signal by the Hermite model.

Abstract: The most characteristic wave set in ECG signals is the QRS complex. Automatic procedures to classify the QRS are very useful in the diagnosis of cardiac dysfunctions. Early detection and classification of QRS changes are important in real-time monitoring. ECG data compression is also important for storage and data transmission. An Adaptive Hermite Model Estimation System (AHMES) is presented for on-line beat-to-beat estimation of the features that describe the QRS complex with the Hermite model. The AHMES is based on the multiple-input adaptive linear combiner, using as inputs the succession of the QRS complexes and the Hermite functions, where a procedure has been incorporated to adaptively estimate a width related parameter b. The system allows an efficient real-time parameter extraction for classification and data compression. The performance of the AHMES is compared with that of direct feature estimation, studying the improvement in signal-to-noise ratio. In addition, the effect of misalignment at the QRS mark is shown to become a neglecting low-pass effect. The results allow the conditions in which the AHMES improves the direct estimate to be established. The application is shown, for subsequent classification, of the AHMES in extracting the QRS features of an ECG signal with the bigeminy phenomena. Another application is highlighted that helps wide ectopic beats detection using the width parameter b.

Progressive ECG changes in arrhythmogenic right ventricular disease. Evidence for an evolving disease.

Abstract: Electrocardiography results were used to assess diagnosis and evolution of arrhythmogenic right ventricular disease. The initial ECG presentation and long-term changes were analysed in 74 consecutive patients with symptomatic ventricular tachycardia and arrhythmogenic right ventricular disease. On first available tracings, a left axis deviation of the QRS was found in 18 patients. The QRS length in V1 was > or = 110 ms in 39 patients, an epsilon wave was present in 17, and a complete right bundle branch block in four patients. The T wave was negative in V1-V3 in 37 patients (50%). In 36 patients, long-term electrocardiographic follow-up of 9.5 +/- 3.2 years was available. During this period, ECG changes were observed in 20 patients (56%): negative T waves in 11 patients, a new left axis deviation in three, QRS enlargement in 13 (including eight right bundle branch block), right atrial hypertrophy in three, and paroxysmal or established atrial fibrillation in three. On studying all 110 ECG tracings (74 initial recordings +36 follow-up ECGs), we found a strong correlation between QRS or T wave changes and the length of follow-up after the first symptom; mean time interval between first ventricular tachycardia and ECG recording was significantly longer in patients with negative T waves in the right precordial leads, QRS enlargement, or left axis deviation, than in patients without such abnormalities. ECG abnormalities were more frequent at 10 year and 5 year follow-up than on initial tracings. A normal ECG was found in 40% of patients during the first year of follow-up, 8% at 5 years, and never later than the 6th year. In conclusion, electrocardiographic diagnosis of arrhythmogenic right ventricular disease may be difficult in the initial stage of the disease, since a normal ECG is found in up to 40% of patients. During the follow-up, progressive and characteristic ECG changes will occur. Arrhythmogenic right ventricular disease can be excluded if the ECG is found to be normal 6 years or later after a first ventricular tachycardia attack.

Distortion of the Terminal Portion of the QRS on the Admission Electrocardiogram in Acute Myocardial Infarction and Correlation With Infarct Size and Long-Term Prognosis (Thrombolysis In Myocardial Infarction 4 Trial) *

Abstract: Previous studies have shown an association between distortion of the terminal portion of the QRS (QRS[+] pattern: emergence of the J point ≥50% of the R wave in leads with qR configuration, or disappearance of the S wave in leads with an Rs configuration) on admission and in-hospital mortality in acute myocardial infarction (AMI). However, the mechanism for this association is not known. We assessed the relation between QRS(+) pattern and coronary angiographic findings, infarct size, and long-term prognosis in the Thrombolysis In Myocardial Infarction 4 trial. Patients were allocated into 2 groups based on the presence (QRS[+], n = 85) or absence (QRS[−], n = 293) of QRS distortion. The QRS(+) patients were older (mean ± SD: 61.1 ± 10.6 vs 57.5 ± 10.6 years, p = 0.004), had more anterior AMI (49% vs 37%, p = 0.04), and less previous angina (42% vs 54%, p = 0.05). QRS(+) patients had larger infarct size as assessed by creatine kinase release over 24 hours (209 ± 147 vs 155 ± 129, p = 0.003), and predischarge sestamibi (MIBI) defect (17.9 ± 15.9% vs 11.2 ± 13.4%, p

A simple real-time QRS detection algorithm

Abstract: A simple algorithm using topological mapping has been developed for a real-time detection of the QRS complexes of ECG signals. As a measure of QRS complex energy, the authors used topological mapping from one dimensional sampled ECG signals to two dimensional vectors. To describe a change of curvature, the authors derive modified spatial velocity (MSV), from MSV the authors can locate QRS complexes more easily. The proposed algorithm consists of very small C-language procedures which reliably recognize the QRS complexes. For evaluation the authors used the MIT/BIH arrhythmia database. The proposed algorithm provides a good performance, a 99.58% detection rate of QRS complexes, a 99.57% sensitivity and 99.87% positive predictivity, respectively.

Effect of coupling interval and pacing cycle length on morphology of paced ventricular complexes. Implications for pace mapping.

Abstract: Background Ventricular pace mapping is performed by comparing the QRS morphology of ventricular paced complexes to that of a template arrhythmia, either a premature ventricular depolarization or a QRS complex during ventricular tachycardia. The objective of this study was to evaluate the effect of coupling interval and pacing cycle length on QRS morphology. Methods and Results The study population consisted of 20 patients (mean age, 38±16 years) undergoing a clinically indicated electrophysiology procedure. In the first 10 patients, the effect of coupling interval on the morphology of single paced ventricular complexes was evaluated visually and by signal processing techniques. Visually apparent differences in QRS morphology occurred in a mean of 4/12 electrocardiographic leads with a change in coupling interval of ≥100 ms. In the next 10 patients, the QRS complex morphology during ventricular overdrive pacing at cycle lengths of 600 and 300 ms was found to differ significantly in a mean of 4/12 leads. The QRS morphology during overdrive pacing differed significantly from that of a single paced complex whenever the pacing cycle length differed from the coupling interval of the single paced complex by >80 ms. Conclusions The morphology of single paced QRS complexes may vary, depending on coupling interval, and the QRS morphology during overdrive pacing is affected by the pacing cycle length. During ventricular pace mapping, the coupling interval or cycle length of the template arrhythmia should be matched during pacing. If not, rate-dependent changes in QRS morphology that are independent of the pacing site may confound the results of pace mapping.

Time-voltage area of the QRS for the identification of left ventricular hypertrophy.

Abstract: Standard electrocardiographic criteria have exhibited poor sensitivity for left ventricular hypertrophy at acceptable levels of specificity and perform less well in women than men, even when sex-specific criteria are used. The time-voltage integral of the horizontal plane vector QRS complex can improve identification of hypertrophy in men, but performance of this approach in women and the effect of sex-specific criteria on accuracy have not been examined. To evaluate the accuracy of the time-voltage integral of the QRS complex for the identification of left ventricular hypertrophy in women and to examine the effect of sex- and non–sex-specific criteria on test performance, we obtained standard 12-lead and orthogonal-lead signal-averaged electrocardiograms and echocardiograms in 175 control subjects without hypertrophy (43 women and 132 men) and 75 patients with hypertrophy (26 women and 49 men) defined by echocardiographic criteria (indexed left ventricular mass >110 g/m 2 in women and >125 g/m 2 in men). Voltage of the QRS complex was integrated over the total QRS duration in leads X and Z for calculation of the time-voltage integral of the horizontal plane vector complex. With the use of a partition of 99.2 μV·s with a specificity of 98% in the entire normal group, sensitivity of the horizontal plane vector integral was significantly lower in women than men (31% versus 71%, P P

Radiofrequency catheter ablation of idiopathic ventricular tachycardia originating in the anterior fascicle of the left bundle branch.

Abstract: Ablation of an Anterior Fascicular Idiopathic VT. Introduction: Idiopathic ventricular tachycardia (VT) originating in or close to the anterior fascicle of the left bundle is rare. A patient with no structural heart disease and VT with a right bundle branch block configuration and right-axis deviation underwent an electrophysiologic examination. Methods and Results: Both endocardial activation mapping during VT and pacemapping were performed via a transseptal approach to localize the site of origin of the VT. Endocardial recordings of the His bundle and the posterior and anterior fascicles of the left bundle branch revealed an origin of the VT in or close to the anterior fascicle. The Purkinje potential at that site preceded the QRS complex by 20 msec, with pacemapping showing an optimal match between the paced rhythm and the clinical VT. RF energy delivered at this site terminated the VT. A left anterior nemiblock appeared after RF ablation. Ten months later, the patient is free from recurrences of VT. Conclusions: Idiopathic VT originating in or close to the anterior fascicle was cured by RF ablation. A Purkinje potential preceding the QRS during tachycardia and an optimal pacemap were used to guide RF ablation.

The Electrocardiogram of the Pekin Duck

Abstract: SUMMARY. In this study, standard limb lead electrocardiograms (ECG) were recorded in 50 Pekin ducks. The ECG exhibited P, R, S, and T waves. A Q wave was observed in 30% of leads aVR aVL. All waves in lead I were of very low amplitude or almost isoelectric. The P wave was 20% negative, 80% positive in lead aVR and always positive in other leads. The duration and amplitude of P wave were 0.025 sec and 0.17 mV, respectively, and the P-R interval was 0.06 sec in lead II. A Q wave was observed in 30% of leads aVR and aVL but was invisible in other leads. The duration of QRS complex was 0.036 sec and its amplitude was 0.069 mV. The S wave (rS) was greater than the R wave in leads III and aVE The R and S waves were equal in lead III (66%). The mean duration and amplitude of T wave were 0.05 sec and 0.22 mV, respectively. The T wave was negative in leads aVR and aVL and positive in other leads. The Q-T interval was 0.10 sec. The mean heart rate was 281.3 (220-375) beats/min. The average value of the mean electrical axis was + 147? (+95? to -160?).

Diagnostic clues from the surface ecg to identify idiopathic (fascicular) ventricular tachycardia : correlation with electrophysiologic findings

Abstract: ECG in Idiopathic Fascicular VT. Introduction: An RS interval > 100 msec in precordial leads has been recently described for the diagnosis of ventricular tachycardia (VT). The aim of this study was to assess the value of this criterion when applied to patients with right bundle branch block pattern, left-axis deviation (fascicular) VT sensitive to verapamil. Methods and Results: Eleven patients (mean age 31 ± 11 years; range 16 to 51) had a mean heart rate of 164 ± 37 beats/min (range 107 to 230) during VT, The QRS complex axis was -92°± -15° (range -80 to -115). The mean QRS duration was 121 ± 9 msec (range 105 to 140). The mean RS interval was 67 ± 9 msec (range 60 to 80). Fusion beats were present in 2 patients (18%), and AV dissociation confirmed by electrophysiologic study was found on ECG in 8 (73%) of 11. During tachycardia, the QRS-H'interval was 19 ± 10 msec (range 10 to 30) in 6 of 11 patients. In seven patients, a fast, unique (or double) presystolic potential lasting 32 msec (range 12 to 40) occurring before the onset of the QRS complex was found at the site of origin of VT, localized in the inferior apical left ventricular septum. In all cases, VT was successfully treated by catheter ablation. Conclusion: A wide QRS complex tachycardia with right bundle branch block and left-axis deviation sensitive to verapamil observed in a young patient without structural heart disease should not be confused with supraventricular tachycardia with aberrancy but rather suggests the presence of fascicular VT. As opposed to VT associated with structural heart disease, the RS interval is < 80 msec in all precordial leads in all cases. Independent of this parameter, AV dissociation detectable on surface ECG has a sensitivity of 73%, which increases to 82% in the presence of fusion beats.

Spectrum off electrophysiologic and electropharmacologic characteristics of verapamil-sensitive ventricular tachycardia in patients without structural heart disease

Abstract: Verapamil-sensitive ventricular tachycardia (VT) is a well-recognized clinical entity that some authorities believe may result from triggered activity. Despite its uniform response to verapamil, however, there is evidence that this uncommon form of VT may not be as homogeneous as first believed. Standard intracardiac electrophysiologic techniques were used to study verapamil-sensitive VT in 32 patients (aged 38 years +/- 20 years) without evidence of structural heart disease. More than half of these patients (69%) exhibited VT with a right bundle branch block-type QRS pattern, with the remainder (31%) displaying VT with a left bundle branch block pattern. In 31% of the patients the VT could be induced by fixed-cycle length atrial pacing, whereas in 59% of patients fixed-cycle length ventricular pacing was necessary. A critical range of cycle lengths for VT induction was required in 66% of the patients. Ventricular tachycardia was initiated with single atrial premature extrastimuli in 16% of patients, single ventricular extrastimuli in 50% of patients, and double ventricular premature extrastimuli in 9% of patients. Ventricular tachycardia displaying cycle-length alternans was observed in 28% of patients. In only 19% of patients was it possible to entrain VT during pacing from the right ventricular apex. Isoproterenol infusion was required for tachycardia induction in 50% of patients, 44% of whom had VT with a left bundle branch block QRS pattern, with the remaining 56% exhibiting VT with a right bundle branch block pattern. Beta-adrenergic blockers suppressed 53% of verapamil-sensitive VT in patients tested, whereas adenosine terminated VT in 50% of patients, with 81% of these patients exhibiting either a left bundle branch block QRS pattern or isoproterenol dependence. Ventricular tachycardia exhibiting a left bundle branch block pattern was more likely to be isoproterenol dependent (p 0.5). Verapamil-sensitive VT exhibits properties expected of both a reentrant and triggered arrhythmia, and it is inconsistently dependent on both exogenous catecholamines for induction and intravenous adenosine for termination. Verapamil-sensitive VT encompasses a heterogeneous group of tachycardias that may result from multiple cellular electrophysiologic mechanisms.

Ventricular arrhythmias and athlete's heart. Role of signal-averaged electrocardiography.

Abstract: The aim of this study was to assess the prevalence and the prognostic value of ventricular late potentials in apparently healthy top-level athletes with ventricular arrhythmias, and the effect of physiological myocardial hypertrophy (athlete's heart) on the electrogenesis of the signal-averaged electrocardiogram (ECG). Two groups of asymptomatic athletes without underlying heart disease were studied: group A consisted of 35 athletes without arrhythmias and group B of 25 athletes with frequent and complex ventricu lar arrhythmias (ventricular ectopic beats >5000. 24 h−1 and ventricular couplets >15 . 24 h−1). Late potentials were present if athletes had significantly prolonged filtered QRS and low amplitude signal duration and low root mean square voltages at both 25–250 Hz and 40–250 Hz filters. While late potentials were absent in all normal athletes of group A, they were present in seven of 25 (28%) athletes with arrhythmias of group B ( P <0·003 Ten of 25 athletes (five with and five without late potentials) of group B underwent programmed ventricular stimulation using a protocol comprising up to three extrastimuli. No episode of sustained ventricular tachycardia was induced. In four of five athletes with late potentials and in one of five without them, unsustained ventricular responses were induced. Echocardiographically determined left ventricular mass found in both groups of athletes did not influence the pathological result of the signal-averaged ECG parameters. This study shows the applicability of the signal-averaged ECG in identifying ventricular late potentials in a selected population of top-level athletes with frequent and complex ventricular arrhythmias and without overt heart disease; it also shows that the presence of late potentials is not influenced by left ventricular mass, even if extreme (>350 g), and it is correlated to a non-sustained ventricular response during an electrophysiological study.

The QRS score: a promising new exercise score for detecting coronary artery disease based on exercise-induced changes of Q-, R- and S-waves: a relationship with myocardial ischaemia.

Abstract: Background Recently, a new exercise test criterion diagnosing coronary artery disease was proposed, based on a composite of changes in Q-, R- and S-waves: the QRS score. We compared this new criterion with conventional ST-segment depression and other compositions of Q-, R and S-wave changes in patients and normals and related the QRS score to reversible thallium-201 scintigraphic defects and ST-segment depression as markers for ischaemia. The influence of beta-blockade on the QRS score was also studied. Methods The study population consisted of 155 persons with 53 normals (group I) and 102 patients with documented coronary artery disease (group II). Another 20 patients (group III) with proven coronary artery disease and a positive exercise test by ST-segment criteria were studied for the influence of beta-blockade on the QRS score. A symptom-limited exercise protocol according to the modified Bruce protocol was used. For the QRS score, Q-, R- and S-wave amplitudes which could be recovered immediately were subtracted from pretest values: δQ, δR, δS respectively. The score was calculated by the formula: (δR − δQ −δS)AVF+(δR −δQ−δS)V5. Results Using a cut-off point of >5 as normal, the QRS score resulted in a sensitivity of 88·2%, a specificity of 84·8% and a predictive accuracy of 87·1%. For ST-segment depression these values were 54·9% 83% and 64·5% respectively (P<0·00l compared to the QRS score.) Predictive accuracies of changes in Q-, R- and S-waves in leads AVF and VS separately, combinations of changes and combining the two leads, resulted—with the exception of solitary S-wave changes—in predictive accuracies higher than those of ST-segment depression, but all were lower than the QRS score. We found a significant correlation between the QRS score, the summed ST-segment depres sion (P<0004) and the extent of reversible thallium-201 defects (P<0·004 Applying Bayes' theorem, the combination of an abnormal QRS score and ST-segment depression resulted in the highest post-test risk for coronary artery disease and a normal QRS score without ST-segment depression in the lowest post-test risk. The QRS score and the maximal ST-segment depression changed significantly under the influence of beta-blockade (P<0·02 and P<0·001 respectively). Conclusion Our data suggest that an abnormal QRS score reflects myocardial ischaemia. Furthermore, for the interpretation of the exercise test, the combined analysis of ST-segments and the QRS score is of value for the prediction of the presence or absence of coronary artery disease and its follow-up.