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QRS Complexes (qr + complex)

Distribution by Scientific Domains

Medical Sciences	97%

Kinds of QRS Complexes

wide QR complex

Terms modified by QRS Complexes

QR complex tachycardia

Selected Abstracts

Relationship between the Duration of the Basal QRS Complex and Electrical Therapies for Ventricular Tachycardias among ICD Patients

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2010
JAVIER JIMÉNEZ-CANDIL M.D., Ph.D.
Background:,In implantable cardioverter-defibrillators (ICD) patients, the duration of the basal QRS complex (QRSd) is not associated with a greater risk of developing ventricular tachyarrhythmias. QRSd could be inversely related to the effectiveness of antitachycardia pacing (ATP) because it may be associated with longer conduction times of the paced-impulses and hence, with a greater propensity to require shocks to terminate ventricular tachycardias (VTs). Methods:,We followed 216 ICD patients (pacing site: right ventricular apex; QRSd , 100: 34%) for 21 ± 12 months. ICD programming was standardized. QRSd was determined on the electrocardiogram (50 mm/s) at device implantation. Results:,Five hundred and fifty-one VTs (cycle length: 329 ± 35 ms) occurred in 67 patients (36% had a QRSd , 100 ms). ATP terminated 86% of VTs and 11% needed shocks. Mean ATP efficiency per patient was 83%. QRSd was significantly correlated with the probability of successful ATP (C-coefficient: 0.66), the best cut-off point being 100 (sensitivity and specificity of 91% and 49%). Patients with QRSd , 100 had a higher ATP effectiveness (98% vs 75%; P = 0.003) and fewer VTs terminated by shocks (1% vs 23%; P = 0.003). By logistic regression, QRSd > 100 remained as an independent predictor of receiving shocks to terminate VTs (P = 0.01). According to Kaplan-Meier analysis, the occurrence of VTs was similar regardless of the QRSd (30% vs 38%; P = 0.2), but the incidence of shock due to VTs was higher in patients with a QRSd > 100 (19% vs 7%; P = 0.01). Conclusion:,Since QRSd is a negative and independent predictor of effective ATP, ICD patients with QRSd > 100 ms require shocks more frequently to terminate VTs. (PACE 2010; 596,604) [source]

Extremely Wide QRS Complex with VVI Pacing

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7 2002
JÁNOS TOMCSÁNYI
No abstract is available for this article. [source]

Fragmented QRS Complexes on 12-Lead ECG: A Marker of Cardiac Sarcoidosis as Detected by Gadolinium Cardiac Magnetic Resonance Imaging

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2009
Mohamed Homsi M.D.
Background: Fragmented QRS complexes (fQRS) on a 12-lead ECG are a marker of myocardial scar in patients with coronary artery disease. Cardiac sarcoidosis is also associated with myocardial granuloma formation and scarring. We evaluated the significance of fQRS on a 12-lead ECG compared to Gadolinium-delayed enhancement images (GDE) in cardiac magnetic resonance imaging (CMR). Method and results: The ECGs of patients (n = 17, mean age: 52 ± 11 years, male: 53%) with established diagnosis of sarcoidosis who underwent a CMR for evaluation of cardiac involvement were studied. ECG abnormalities included bundle branch block, Q wave, and fQRS. fQRS, Q wave, and bundle branch block were present in 9 (53%), 1 (6%), and 4 (24%) patients, respectively. The sensitivity and specificity of fQRS for detecting abnormal GDE were 100% and 80%, respectively. Sensitivity and specificity of Q waves were 11% and 100%, respectively. Conclusions: fQRS on a 12-lead ECG in patients with suspected cardiac sarcoidosis are associated with cardiac involvement as detected by GDE on CMR. [source]

Electrophysiologic Characteristics of Wide QRS Complexes during Pharmacologic Termination of Sustained Supraventricular Tachycardias with Verapamil and Adenosine: Observations from Electrophysiologic Study

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2009
Cengizhan Türko, lu M.D.
Background: In this study we evaluate wide QRS complexes observed during pharmacologic termination of supraventricular tachycardias. Methods: Patients with supraventricular tachycardia, undergoing electrophysiologic study were enrolled. 12 mg of adenosine or 10 mg of verapamil were administered during tachycardia, under continuous monitoring of intaracardiac and surface electrocardiograms. Electrocardiographic features of ventricular ectopy were noted. Results: Seventy-four patients were enrolled. 48 patients were randomized to adenosine and 26 to verapamil. Five different appearance patterns of ventricular ectopy were observed during termination of tachycardias. All wide QRS complexes were of ventricular origin and all of them were observed during the termination of tachycardia. Adenosine more frequently resulted in appearance of ventricular beats (15.4% vs 41.7%, P = 0.003), and this was more frequently observed in patients with atrioventricular nodal reentrant tachycardia. Patients with ventricular beats were younger than those without, in both, verapamil (47.5 ± 15.6 vs 65.0 ± 8.8 years, P = 0.04) and adenosine (40.9 ± 13.8 vs 49.7 ± 16.8, P = 0.03) groups. Left bundle branch block (LBBB)/superior axis morphology was most frequent morphology in adenosine group (55%). Two of 4 patients in verapamil group displayed LBBB/inferior axis QRS morphology and another 2 patients displayed LBBB/superior axis morphology. Conclusions: Noncatheter induced, five different appearance patterns and four distinct morphologies of ventricular origin were observed. Most of them do not directly terminate tachycardia, but are associated with its termination and are not observed in ongoing tachycardia. [source]

Acceleration-Dependent Left Bundle Branch Block with Severe Left Ventricular Dyssynchrony Results in Acute Heart Failure: Are There More Patients Who Benefit from Cardiac Resynchronization Therapy?

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 1 2006
KATJA ZEPPENFELD M.D.
Cardiac resynchronization therapy (CRT) has been proposed to improve hemodynamics in patients with heart failure and left bundle branch block (LBBB) by resynchronization of left ventricular (LV) dyssynchrony. The current report concerns a patient with narrow QRS complex without LV dyssynchrony who experienced an acute exacerbation of heart failure following exercise. Careful analysis revealed that an increase of heart rate induced acceleration-dependent LBBB with severe LV dyssynchrony and mitral regurgitation followed by acute heart failure and hemodynamic collapse. CRT prevented these adverse reactions. Accordingly, optimal evaluation for CRT may include testing for LV dyssynchrony during exercise. [source]

Idiopathic Left Ventricular Tachycardia Originating from the Mitral Annulus

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2005
KOJI KUMAGAI M.D.
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. [source]

Unusual Mode of Tachycardia Termination Uncovers the Underlying Arrhythmia Mechanism

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2004
MÁXIMO RIVERO-AYERZA M.D.
We discuss the differential diagnosis of a tachycardia with a broad QRS complex and how the mode of termination helped elucidate the underlying tachycardia mechanism. [source]

Reentrant Ventricular Tachycardia Originating from the Aortic Sinus Cusp:

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2004
A Case Report
We report a case of idiopathic reentrant ventricular tachycardia (VT) originating from the left aortic sinus cusp. A prepotential preceding the QRS complex by 58 ms was recorded from the posterior right ventricular (RV) outflow tract. During VT entrainment observed by pacing from the midseptal RV, it initially was orthodromically captured with a long conduction time but then antidromically captured as the pacing cycle rate was increased. Pacing at that site failed to show concealed entrainment despite a postpacing interval similar to the VT cycle length. Radiofrequency catheter ablation abolished the VT in the left aortic sinus cusp where a prepotential preceding the QRS complex by 78 ms with a postpacing interval similar to the VT cycle length was recorded in addition to concealed entrainment. The findings suggest that, in this VT, a critical slow conduction zone is partially present extending from the left aortic sinus cusp to the posterior right ventricular outflow tract. The patient has remained free from VT recurrence after 5-month follow-up. [source]

Arrhythmogenesis of T Wave Alternans Associated with Surface QRS Complex Alternans and the Role of Ventricular Prematurity: Observations from a Canine Model of LQT3 Syndrome

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2002
MASAOMI CHINUSHI M.D.
Intramural TWA and Its Arrhythmogenesis.Introduction: T wave alternans (TWA) is characterized by cycle-to-cycle changes in the QT interval and/or T wave morphology. It is believed to amplify the underlying dispersion of ventricular repolarization. The aim of this study was to examine the mechanisms and arrhythmogenesis of TWA accompanied by QRS complex and/or blood pressure (BP) waveform alternans, using transmural ventricular electrogram recordings in an anthopleurin-A model of long QT syndrome. Methods and Results: The cardiac cycle length was gradually shortened by interruption of vagal stimulation, and TWA was induced in six canine hearts. Transmural unipolar electrograms were recorded with plunge needle electrodes from endocardial (Endo), mid-myocardial (Mid), and epicardial (Epi) sites, along with the surface ECG and BP. The activation-recovery interval (ARI) was measured to estimate local refractoriness. During TWA, ARI alternans was greater at the Mid than the Epi/Endo sites, and it was associated with the development of marked spatial dispersion of ventricular repolarization. As TWA increased, ventricular activation of the cycles associated with shorter QT intervals displayed delayed conduction at the Mid sites as a result of a critically longer ARI of the preceding cycle and longer QT interval, while normal conduction was preserved at the Epi site. Delayed conduction at the Mid sites manifested as surface ECG QRS and BP waveform alternans, and spontaneous ventricular tachyarrhythmias developed in absence of ventricular prematurity. In other instances, in absence of delayed conduction during TWA, ventricular premature complexes infringed on a prominent spatial dispersion of ventricular repolarization of cycles with long QT intervals and initiated ventricular tachyarrhythmia. Conclusion: TWA accompanied by QRS alternans may signal a greater ventricular electrical instability, since it is associated with intramural delayed conduction, which can initiate ventricular tachyarrhythmia without ventricular premature complexes. [source]

Relationship between the Duration of the Basal QRS Complex and Electrical Therapies for Ventricular Tachycardias among ICD Patients

Analysis of the Electrocardiographic Waveforms Produced by Right Ventricular Pacing: Relation to the Nonpaced Patterns

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2008
HOWARD S. FRIEDMAN M.D.
Background: Ventricular aberrant conduction has a confounding effect on the known relationships between the electrocardiogram (ECG) and left ventricular (LV) mass. By relating the ECG of right ventricular pacing to LV mass and to nonpaced recordings, clarification of these effects might emerge. Methods and Results: In 30 patients (age, 81 ± 7 years; 13 women) who had right ventricular paced ECGs and echocardiograms, 24 of who also had nonpaced ECGs, comparative analyses were performed. Although the nonpaced ECGs had strong correlations with various echocardiographic measurements, for paced ECGs, only QRS complex voltage and interventricular septal thickness (IVS) were significantly related. However, paced QRS complex voltage relationships correlated with those of nonpaced QRS complexes, ranging from an r = 0.54, P < 0.006, for the sum of the R in aVL and the S in V-3 to r = 0.78, P < 0.001, for the sum of the R in I and the S in III. Paced ECGs had a QRS complex with a greater spatial amplitude, a longer duration, and a more superior position, and had more deeply inverted T waves than nonpaced ECGs. The differences between the voltages of paced and nonpaced QRS complexes, moreover, diminished as LV mass and/or IVS increased. When compared with nonpaced ECGs, paced ECGs showed the most similarity to nonpaced ECGs having a left bundle branch block (LBBB) pattern. Except for the presence of more superiorly directed QRS complexes, paced impulses were not significantly different (P < 0.008) from nonpaced impulses having a LBBB pattern. Also, the nonpaced ECG pattern had no discernable effect on ECG produced by right ventricular (RV) pacing. Conclusions: Despite having weak relations with echocardiographic measurements, the QRS complex voltage of the paced ECG correlated with those of nonpaced ECGs, and the voltage differences between them were smaller as LV mass increased. [source]

The Resting Electrocardiogram in the Management of Patients with Congestive Heart Failure: Established Applications and New Insights

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2007
JOHN E. MADIAS M.D.
The resting electrocardiogram (ECG) furnishes essential information for the diagnosis, management, and prognostic evaluation of patients with congestive heart failure (CHF). Almost any ECG diagnostic entity may turn out to be useful in the care of patients with CHF, revealing the non-specificity of the ECG in CHF. Nevertheless a number of CHF/ECG correlates have been proposed and found to be indispensable in clinical practice; they include, among others, the ECG diagnoses of myocardial ischemia and infarction, atrial fibrillation, left ventricular hypertrophy/dilatation, left bundle branch block and intraventricular conduction delays, left atrial abnormality, and QT-interval prolongation. In addition to the above well-known applications of the ECG for patients with CHF, a recently described association of peripheral edema (PERED), sometimes even imperceptible by physical examination, with attenuated ECG potentials, could extend further the diagnostic range of the clinician. These ECG voltage attenuations are of extracardiac mechanism, and impact the amplitude of QRS complexes, P-waves, and T-waves, occasionally resulting also in shortening of the QRS complex and QT interval duration. PERED alleviation, in response to therapy of CHF, reverses all above alterations. These fresh diagnostic insights have potential application in the follow-up of patients with CHF, and in their selection for implantation of cardioverter/defibrillator and/or cardiac resynchronization systems. If sought, PERED-induced ECG changes are abundantly present in the hospital and clinic environments; if their detection and monitoring are incorporated in the clinician's "routine," considerable improvements in the care of patients with CHF may be realized. [source]

Pseudotermination of Atrioventricular Nodal Reentrant Tachycardia Related to Isorhythmic Atrioventricular Dissociation

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 12 2003
MITSUNORI MARUYAMA
Unusual manifestations of the mode of termination were observed in a patient with atrioventricular nodal reentrant tachycardia (AVNRT). After administration of verapamil during AVNRT, isorhythmic atrioventricular dissociation occurred without termination of the tachycardia. The sinus rate was slightly faster than that of the AVNRT, leading to the P wave preceding the QRS complex with a normal PR interval (e.g., pseudotermination). This phenomenon emphasizes the importance of continuous monitoring during an attempt to terminate AVNRT. (PACE 2003; 26:2338,2339) [source]

Is the Fascicle of Left Bundle Branch Involved in the Reentrant Circuit of Verapamil-Sensitive Idiopathic Left Ventricular Tachycardia?

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 10 2003
JEN-YUAN KUO
The exact reentrant circuit of the verapamil-sensitive idiopathic left VT with a RBBB configuration remains unclear. Furthermore, if the fascicle of left bundle branch is involved in the reentrant circuit has not been well studied. Forty-nine patients with verapamil-sensitive idiopathic left VT underwent electrophysiological study and RF catheter ablation. Group I included 11 patients (10 men, 1 woman; mean age 25 ± 8 years) with left anterior fascicular block (4 patients), or left posterior fascicular block (7 patients) during sinus rhythm. Group II included 38 patients (29 men, 9 women; mean age 35 ± 16 years) without fascicular block during sinus rhythm. Duration of QRS complex during sinus rhythm before RF catheter ablation in group I patients was significant longer than that of group II patients (104 ± 12 vs 95 ± 11 ms, respectively, P = 0.02). Duration of QRS complex during VT was similar between group I and group II patients (141 ± 13 vs 140 ± 14 ms, respectively, P = 0.78). Transitional zones of QRS complexes in the precordial leads during VT were similar between group I and group II patients. After ablation, the QRS duration did not prolong in group I or group II patients (104 ± 11 vs 95 ± 10 ms, P = 0.02); fascicular block did not occur in group II patients. Duration and transitional zone of QRS complex during VT were similar between the two groups, and new fascicular block did not occur after ablation. These findings suggest the fascicle of left bundle branch may be not involved in the antegrade limb of reentry circuit in idiopathic left VT. (PACE 2003; 26:1986,1992) [source]

Magnetocardiographic Intra-QRS Fragmentation Analysis in the Identification of Patients with Sustained Ventricular Tachycardia after Myocardial Infarction

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2001
PETRI KORHONEN
KORHONEN, P., et al.: Magnetocardiographic Intra-QRS Fragmentation Analysis in the Identification of Patients with Sustained Ventricular Tachycardia after Myocardial Infarction. The aim of this study was to investigate if magnetocardiographic (MCG) analysis of cardiac micropotentials within the QRS complex can identity patients prone to ventricular arrhythmias, and to compare it to MCG time-domain, late-field analysis. The study population consisted of 136 patients with remote MI, 53 with and 83 without a history of VT. After averaging and high pass filtering of multichannel MCG signals, time-domain parameters describing the end-QRS activity and fragmentation index M and score S describing the whole QRS complex were computed. Fragmentation and time-domain parameters differed between the VT and control groups: fragmentation index M was 12 ± 3 versus 9 ± 2 (P < 0.001), fragmentation score S was 83 ± 42 versus 56 ± 21 (P < 0.001), and filtered QRS duration was 144 ± 32 versus 114 ± 19 ms (P < 0.001) in VT and control groups, respectively. A combination of fragmentation parameters yielded 87% sensitivity and 61% specificity in VT identification. Corresponding figures for a time-domain parameter combination were 81% and 72%. Sensitivity of time-domain analysis was 88% and specificity was 75% in a subgroup with anterior MI. In multivariate analysis, fragmentation and time-domain analyses discriminated VT patients from controls independently of the extent of coronary artery disease or left ventricular dysfunction. MCG in postinfarction patients reveals pathology associated with propensity to ventricular arrhythmias inside and not only at the end of the QRS complex. MCG seems most accurate in the anterior infarct location. [source]

Atrial Fibrillation Induction and Determination of Atrial Vulnerable Period Using Very Low Energy Synchronized Biatrial Shock in Normal Subjects and in Patients with Atrial Fibrillation

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 4 2000
HUNG-FAT TSE
The atrial vulnerable periods (A VP)for shock induction of atrial fibrillation (AF) in humans have not been clearly defined. Furthermore, the safety and efficacy of using low energy biatrial shock delivered transvenously for AF induction are unknown. We tested the safety and efficacy of using very low energy biatrial shocks, delivered between the right atrium and the coronary sinus for AF induction and used this technique to characterize the A VP in nine controls and nine patients with AF. Thirty-volt and 60-V 3/3-ms biphasic shocks were delivered, starting from 50 ms before the atrial effective refractory period with 20-ms increments until the end of the QRS interval to determine the AVP front, AVP end, and the AVP duration. Successful AF induction could be achieved in eight (89%) of the nine controls and in nine (100%) of the nine patients with AF without any complication. In patients with AF, the AVP front started significantly earlier within the QRS complex, and the AVP duration and the AVP duration/QRS percent ratios were also significantly greater as compared to controls. Furthermore, a higher induction shock energy in patients with AF was associated with an increase in AF inducibility and significantly increased the AVP duration and A VP duration/QRS percent ratio as compared to the controls. This study demonstrated the safe and efficacy of delivering a very low energy biatrial shock during the AVP within the R wave for AF induction. The characteristics of A VP in patients with AF were significantly different from normal subjects. [source]

QRS Amplitude and Shape Variability in Magnetocardiograms

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2000
MARKUS HUCK
In magnetocardiography, averaging of QRS complexes is often used to improve the signal-to-noise ratio. However, averaging of QRS complexes ignores the variation in amplitude and shape of the signals caused, for example, by respiration. This may lead to suppression of signal portions within the QRS complexes. Furthermore, for inverse source, reconstructions of dipoles and of current density distributions errors in the special arrangement may occur. To overcome these problems we developed a method for separating and selective averaging QRS complexes with different shapes and amplitudes. The method is based on a spline interpolation of the QRS complex averaged by a standard procedure. This spline function then is fitted to each QRS complex in the raw data by means of nonlinear regression (Levenberg-Marquardt method). Five regression parameters are applied: a linear amplitude scaling, two parameters describing the baseline drift, a time scaling parameter, and a time shift parameter. We found that both amplitude and shape of the QRS complex are influenced by respiration. The baseline shows a weaker influence of the respiration. The regression parameters of two neighboring measurement channels correlate linearly. Thus, selective averaging of a larger number of sensors can be performed simultaneously. [source]

Diagnostic Significance of a Small Q Wave in Precordial Leads V2 or V3

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 2 2010
Tetsuya Katsuno M.D.
Background: An abnormal Q wave is usually defined as an initial depression of the QRS complex having a duration of ,40 ms and amplitude exceeding 25% of the following R wave in any contiguous leads on the 12-lead electrocardiogram (ECG). However, much smaller Q waves are sometimes recorded on the ECG. This study investigated the diagnostic value of the small Q wave recorded in precordial leads V2 or V3 on the ECG. Methods: We investigated 807 consecutive patients who underwent coronary angiography. A small Q wave was defined as any negative deflection preceding the R wave in V2 or V3 with <40-ms duration and <0.5-mV amplitude, with or without a small (<0.1-mV) slurred, spiky fragmented initial QRS deflection before the Q wave (early fragmentation). ECG and coronary angiographic findings were analyzed. Results: The small Q wave was present in 87 patients. Multiple logistic regression analysis revealed that presence of a small Q wave was a strong independent predictor of any coronary artery stenosis or left anterior descending artery (LAD) stenosis (odds ratio = 2.706, 2.902; P < 0.001, < 0.001, respectively). Conclusion: A small Q wave (<40-ms duration and <0.5-mV amplitude) in V2 or V3 with or without early fragmentation significantly predicted the presence of CAD and, especially, significant stenosis in the LAD. Ann Noninvasive Electrocardiol 2010;15(2):116,123 [source]

Detailed ECG Analysis of Atrial Repolarization in Humans

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 1 2009
Fredrik Holmqvist M.D., Ph.D.
Introduction: Data on human atrial repolarization are scarce since the QRS complex normally obscures its ECG trace. In the present study, consecutive patients with third-degree AV block were studied to better describe the human Ta wave. Methods and Results: Forty patients (mean age 75 years, 17 men) were included. All anti-arrhythmic drugs were discontinued before ECG recording. Standard 12-lead ECGs were recorded, transformed to orthogonal leads and studied using signal-averaged P wave analysis. The average P wave duration was 124 ± 16 ms. The PTa duration was 449 ± 55 ms (corrected PTa 512 ± 60 ms) and the Ta duration (P wave end to Ta wave end) was 323 ± 56 ms. The polarity of the Ta wave was opposite to that of the P wave in all leads. The Ta peaks were located at 196 ± 55 ms in Lead Y, 216 ± 50 ms in Lead X, and 335 ± 92 in Lead Z. No correlation was found between P wave duration and Ta duration, or between Ta peak amplitude and Ta duration. The morphology of the Ta wave was similar regardless of the interatrial conduction. Conclusions: The Ta wave has the opposite polarity, and the duration is generally two to three times that, of the P wave. Although the Ta peak may occasionally be located in the PQ interval during normal AV conduction, it is unlikely that enough information can be obtained from analysis of this segment to differentiate normal from abnormal atrial repolarization. Hence, an algorithm for QRST cancellation during sinus rhythm is needed to further improve analysis. [source]

Standard Template of Adult Magnetocardiogram

ANNALS OF NONINVASIVE ELECTROCARDIOLOGY, Issue 4 2008
Akihiko Kandori Ph.D.
Background: We need to know the magnetocardiogram (MCG) features regarding waveform and two-dimensional current distribution in normal subjects in order to classify the abnormal waveform in patients with heart disease. However, a standard MCG waveform has not been produced yet, therefore, we have first made the standard template MCG waveform. Methods and Results: We used data from 464 normal control subjects' 64-channel MCGs (268 males, 196 females) to produce a template MCG waveform. The measured data were averaged after shortening or lengthening and normalization. The time interval and amplitude of the averaged data were adjusted to mean values obtained from a database. Furthermore, the current distributions (current arrow maps [CAMs]) were calculated from the produced templates to determine the current distribution pattern. The produced template of the QRS complex had a typical shape in six regions that we defined (M1, M2, M3, M4, M5, and M6). In the P wave, the main current arrow in CAMs pointing in a lower-left direction appeared in M1. In the QRS complex, the typical wave appeared in each region, and there were two main current arrows in M2 and M5. There were negative T waves in M1, M4, and M5, and positive T waves in M3 and M6, and the main current arrow pointing in a lower-left direction appeared in M2. Conclusion: Template MCG waveforms were produced. These morphologic features were classified into six regions, and the current distribution was characterized in each region. Consequently, the templates and classifications enable understanding MCG features and writing clinical reports. [source]

John B. Barlow: Master clinician and compleat cardiologist

CLINICAL CARDIOLOGY, Issue 1 2000
Tsung O. Cheng M.D.
Abstract This paper reports the case of a 76-year-old man in whom atrial flutter with varying atrioventricular block and intermittent right bundle-branch block was found. This is the first report on tachycardia-dependent right bundle-branch block associated with supernormal conduction in a case of atrial flutter. When an impulse is conducted to the ventricles beyond 0.72 s after a QRS complex of right bundle-branch block configuration, the impulse falls after the abnormally long effective refractory period of the right bundle branch and passes through the right bundle branch. When the conducted impulse occurs within 0.72 s after a QRS complex of right bundle-branch block configuration, the impulse usually falls in the refractory period and is blocked in the right bundle branch; however, only when the impulse occurs 0.48 or 0.49 s after that does it fall in the supernormal period and passes through the right bundle branch. The findings in the present report strengthen our previous suggestion that the presence of supernormal conduction plays an important role in the initiation of reentrant ventricular tachycardia. [source]

T-Wave Amplitude Attenuation/Augmentation in Patients With Changing Edematous States: Implications for Patients With Congestive Heart Failure

CONGESTIVE HEART FAILURE, Issue 5 2007
John E. Madias MD
Since peripheral edema impacts the entire electrocardiographic curve, it was hypothesized that it would also affect T waves. The amplitude of T waves were measured in all electrocardiographic leads and a sum (,T) was calculated in 28 patients with and 28 patients without peripheral edema (controls). For patients with peripheral edema, ,T on admission was 21.9±10.6 mm and ,T at peak weight was 8.3±6.3 mm (P=.0005). For patients with peripheral edema who subsequently lost weight, ,T at peak weight was 7.2±6.1 mm and ,T at the lowest weight was 14.1±12.2 (P=.006). For controls, ,T from admission and ,T from discharge were 24.4±16.9 mm and 24.7±15.7 mm (P=.82), respectively. Percent change (,%,T) from admission to peak weight correlated with ,% in weight (r=0.58; P=.001) and ,% in the sum of QRS complexes (,QRS) (r=0.71; P=.00005). ,%,T from peak weight to the lowest weight correlated with the corresponding ,%,QRS (r=0.65; P=.02). Changes in T waves with development and alleviation of peripheral edema mirror the changes shown by the QRS complexes and may be useful in the treatment of patients with congestive heart failure or other edematous states. [source]

Detection and delineation of P and T waves in 12-lead electrocardiograms

EXPERT SYSTEMS, Issue 1 2009
Sarabjeet Mehta
Abstract: This paper presents an efficient method for the detection and delineation of P and T waves in 12-lead electrocardiograms (ECGs) using a support vector machine (SVM). Digital filtering techniques are used to remove power line interference and baseline wander. An SVM is used as a classifier for the detection and delineation of P and T waves. The performance of the algorithm is validated using original simultaneously recorded 12-lead ECG recordings from the standard CSE (Common Standards for Quantitative Electrocardiography) ECG multi-lead measurement library. A significant detection rate of 95.43% is achieved for P wave detection and 96.89% for T wave detection. Delineation performance of the algorithm is validated by calculating the mean and standard deviation of the differences between automatic and manual annotations by the referee cardiologists. The proposed method not only detects all kinds of morphologies of QRS complexes, P and T waves but also delineates them accurately. The onsets and offsets of the detected P and T waves are found to be within the tolerance limits given in the CSE library. [source]

Successful Radiofrequency Catheter Ablation of Epicardial Left Ventricular Outflow Tract Tachycardia from the Anterior Interventricular Coronary Vein

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2005
YASUHIRO HIRASAWA M.D.
We report a case of idiopathic left ventricular outflow tract (LVOT) tachycardia that was eliminated by a radiofrequency application from the anterior interventricular coronary vein (AIV). The ECG exhibited QRS complexes with an inferior axis and atypical left bundle branch block pattern with an early transition of the precordial R waves at V3. Several radiofrequency applications from the coronary cusps and endocardial LVOT were not effective. Radiofrequency applications in the AIV, where the activation preceded the onset of the QRS by 30 msec, successfully eliminated the tachycardia. The AIV may be an optional site for radiofrequency ablation of idiopathic epicardial LVOT tachycardia. [source]

Phytanic Acid Accumulation Is Associated with Conduction Delay and Sudden Cardiac Death in Sterol Carrier Protein-2/Sterol Carrier Protein-x Deficient Mice

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2004
GEROLD MÖNNIG M.D.
Introduction: The sterol carrier protein-2 gene encodes two functionally distinct proteins: sterol carrier protein-2 (SCP2, a peroxisomal lipid carrier) and sterol carrier protein-x (SCPx, a peroxisomal thiolase known as peroxisomal thiolase-2), which is involved in peroxisomal metabolism of bile acids and branched-chain fatty acids. We show in this study that mice deficient in SCP2 and SCPx (SCP2null) develop a cardiac phenotype leading to a high sudden cardiac death rate if mice are maintained on diets enriched for phytol (a metabolic precursor of branched-chain fatty acids). Methods and Results: In 210 surface and 305 telemetric ECGs recorded in wild-type (C57BL/6; wt; n = 40) and SCP2 null mice (n = 40), no difference was observed at baseline. However, on diet, cycle lengths were prolonged in SCP2 null mice (262.9 ± 190 vs 146.3 ± 43 msec), AV conduction was prolonged (58.3 ± 17 vs 42.6 ± 4 ms), and QRS complexes were wider (19.1 ± 5 vs 14.0 ± 4 ms). In 11 gene-targeted Langendorff-perfused hearts isolated from SCP2 null mice after dietary challenge, complete AV blocks (n = 5/11) or impaired AV conduction (Wenckebach point 132 ± 27 vs 92 ± 10 msec; P < 0.05) could be confirmed. Monophasic action potentials were not different between the two genotypes. Left ventricular function studied by echocardiography was similar in both strains. Phytanic acid but not pristanic acid accumulated in the phospholipid fraction of myocardial membranes isolated from SCP2 null mice. Conclusion: Accumulation of phytanic acid in myocardial phospholipid membranes is associated with bradycardia and impaired AV nodal and intraventricular impulse conduction, which could provide an explanation for sudden cardiac death in this model. [source]

Independent Autonomic Modulation of Sinus Node and Ventricular Myocardium in Healthy Young Men During Sleep

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 10 2000
PETER KOWALLIK M.D.
Autonomic Modulation of Sinus Node and Ventricle. Introduction. The aim of this study was to investigate whether autonomic modulation of ventricular repolarization may spontaneousiy differ from that of the sinoatrial node. Methods and Results. Onset of P waves. QRS complexes, and the apex and end of T waves were detected heat to heat in high-resolution ECGs from nine healthy young men during the night. There were time-dependent fluctuations in the QT/RR slopes of consecutive 5-minute segments that could not he explained by the mean RR cycle length of the respective segment. Because the variahility found in QT intervals could not be explained hy either possible effects of rate dependence or hysteresis, autonomic effects were obvious. Power speetral analysis was performed for consecutive 5-minute segments of PP and QT techograms. In a given subject. trends in the time course of low-frequency (LF) and high-frequency (HF) power in PP and QT often were similar, but they were quite different at other times. The mean LF/HF ratio for QTend (0.75 ± 0.1) was different from that of PP (1.8 ± 0.2; P = 0.002), indicating differences in sympathovagal balance at the different anatomic sites. Furthermore, at a given mean heart rate, averaged QT intervals were different on a time scale of several minutes to hours. The QT/RR slope of 5-minute segments correlated significantly with the HF power of QT variability but not with that of PP variability, indicating effects of the autonomic nervous system on ventricular action potential restitution. Conclusion. These differences demonstrate that changes in sinus node automaticity are not necessarily indicative of the autonomic control of ventricular myocardium. (J Cardiavasc Electrophysiol, Vol. II, pp. 1063-1070. October 2000) [source]

Validation of 2 Techniques for Electrocardiographic Recording in Dogs and Cats

JOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 4 2006
Luca Ferasin
Background: Standard electrocardiographic (ECG) recording in the dog and cat is commonly performed in right lateral recumbency, by connecting the ECG leads to the skin of the patient via metallic alligator clips. The jaws of the alligator clips are usually filed or flattened to reduce their uncomfortable pressure on the patient's skin. However, filed and flattened alligator clips can occasionally lose their grip to the skin, causing lead detachment during standard ECG recording. Hypothesis: The aim of the study was to validate two novel ECG recording techniques ("gel" and "pads"). Animals: Six-lead standard ECG recording was obtained from 42 dogs and 40 cats using the standard technique, as well as the two novel methods. Methods: Measurements were taken of the amplitude and duration of P waves and QRS complexes, duration of PQ and QT intervals, and mean electrical axis (MEA). In each recording, five representative complexes were measured, and the results were averaged for each parameter. Results: A good quality ECG recording was obtained with all the three different techniques, although a degree of wandering trace was observed in one third of cats with the "pads" technique. Bland-Altman analysis showed good agreement between the ECG values recorded with the two novel techniques and those recorded with the standard traditional technique. Furthermore, the observed differences were not clinically relevant, except for the R wave amplitude recorded with the "pads" method in cats (-0.35 to 0.37 mV). Conclusions and Clinical Importance: In conclusion, this study supports the reliability and clinical validity of the "gel" and "pads" techniques for ECG recording both in the dog and the cat, with some limitations for the "pads" technique in cats. [source]

A Rare type of Ventricular Oversensing in ICD Therapy,Inappropriate ICD Shock Delivery Due to Triple Counting

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2010
MICHAEL GUENTHER M.D.
Irregular sensing by triple counting of wide QRS complexes resulted in inappropriate shocks in a patient with a biventricular implantable cardioverter defibrillator (ICD): A 66-year-old male patient with ischemic cardiomyopathy, left bundle branch block, and impaired left ventricular function received a biventricular ICD for optimal therapy of heart failure (CHF). Two years after implantation, the patient experienced recurrent unexpected ICD shocks without clinical symptoms of malignant tachyarrhythmia, or worsened CHF. The patient's condition rapidly worsened, with progressive cardiogenic shock and electrical,mechanical dissociation. After unsuccessful resuscitation of the patient the interrogation of the ICD showed an initial triple counting of extremely wide and fragmented QRS complexes with inappropriate shocks. (PACE 2010; 33:e17,e19) [source]

ECG Leads I and II to Evaluate Diuresis of Patients with Congestive Heart Failure Admitted to the Hospital via the Emergency Department

PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1 2009
SUTHAPORN LUMLERTGUL M.D.
Background: Attenuation of electrocardiogram (ECG) QRS complexes is observed in patients with a variety of illnesses and peripheral edema (PERED), and augmentation with alleviation of PERED. Serial ECGs in stable individuals display variation in the amplitude of QRS complexes in leads V1,V6, stemming from careless placement of recording electrodes on the chestwall. Electrocardiographs record only leads I and II, and mathematically derive the other four limb leads in real time. This study evaluated the sum of the amplitudes of ECG leads I and II, along with other sets of ECG leads in the monitoring of diuresis in patients with congestive heart failure (CHF). Methods: Twenty patients with CHF had ECGs and weights recorded on admission and at discharge. The amplitude of the QRS complexes in all ECG leads were measured and sums of I and II, all limb leads, V1,V6, and all 12 leads were calculated. Results: There was a good correlation between the weight loss and the increase in the sums of the amplitudes of the QRS complexes from leads I and II (r = 0.55, P = 0.012), and the six limb leads (r = 0.68, P = 0.001), but a poor correlation with the V1,V6 leads (r = 0.04, P = 0.85) and all 12 leads (r = 0.1, P = 0.40). Conclusions: Sums of the amplitudes of the ECG QRS complexes from leads I and II constitute a reliable, easily obtainable, ubiquitously available, bedside clinical index, which can be employed in the diagnosis, monitoring of management, and follow-up of patients with CHF. [source]