Showing papers on "QRS complex published in 2007"

Cardiac-Resynchronization Therapy in Heart Failure with Narrow QRS Complexes

Abstract: Background Indications for cardiac-resynchronization therapy (CRT) in patients with heart failure include a prolonged QRS interval (≥120 msec), in addition to other functional criteria. Some patients with narrow QRS complexes have echocardiographic evidence of left ventricular mechanical dyssynchrony and may also benefit from CRT. Methods We enrolled 172 patients who had a standard indication for an implantable cardioverter–defibrillator. Patients received the CRT device and were randomly assigned to the CRT group or to a control group (no CRT) for 6 months. The primary end point was the proportion of patients with an increase in peak oxygen consumption of at least 1.0 ml per kilogram of body weight per minute during cardiopulmonary exercise testing at 6 months. Results At 6 months, the CRT group and the control group did not differ significantly in the proportion of patients with the primary end point (46% and 41%, respectively). In a prespecified subgroup with a QRS interval of 120 msec or more, the pea...

Minimizing Ventricular Pacing to Reduce Atrial Fibrillation in Sinus-Node Disease

Abstract: Methods We randomly assigned 1065 patients with sinus-node disease, intact atrioventricular conduction, and a normal QRS interval to receive conventional dual-chamber pacing (535 patients) or dual-chamber minimal ventricular pacing with the use of new pacemaker features designed to promote atrioventricular conduction, preserve ventricular conduction, and prevent ventricular desynchronization (530 patients). The primary end point was time to persistent atrial fibrillation. Results The mean (±SD) follow-up period was 1.7±1.0 years when the trial was stopped because it had met the primary end point. The median percentage of ventricular beats that were paced was lower in dual-chamber minimal ventricular pacing than in conventional dual-chamber pacing (9.1% vs. 99.0%, P<0.001), whereas the percentage of atrial beats that were paced was similar in the two groups (71.4% vs. 70.4%, P = 0.96). Persistent atrial fibrillation developed in 110 patients, 68 (12.7%) in the group assigned to conventional dual-chamber pacing and 42 (7.9%) in the group assigned to dual-chamber minimal ventricular pacing. The hazard ratio for development of persistent atrial fibrillation in patients with dual-chamber minimal ventricular pacing as compared with those with conventional dual-chamber pacing was 0.60 (95% confidence interval, 0.41 to 0.88; P = 0.009), indicating a 40% reduction in relative risk. The absolute reduction in risk was 4.8%. The mortality rate was similar in the two groups (4.9% in the group receiving dual-chamber minimal ventricular pacing vs. 5.4% in the group receiving conventional dual-chamber pacing, P = 0.54). Conclusions Dual-chamber minimal ventricular pacing, as compared with conventional dualchamber pacing, prevents ventricular desynchronization and moderately reduces the risk of persistent atrial fibrillation in patients with sinus-node disease. (ClinicalTrials. gov number, NCT00284830.)

Catheter Ablation for Ventricular Tachycardia

Abstract: Sustained ventricular tachycardia (VT) is an important cause of morbidity and sudden death in patients with heart disease.1 Implantable cardioverter-defibrillators (ICDs) terminate VT episodes, reducing the risk of sudden death. Recurrent VT develops in 40% to 60% of patients who receive an ICD after an episode of spontaneous sustained VT. A first episode of VT occurs in ≈20% of patients within 3 to 5 years after ICD implantation for primary prevention of sudden death in high-risk groups.2–4 ICD shocks reduce quality of life and are associated with an increased risk of death.2–4 Antiarrhythmic drug therapy with amiodarone or sotalol reduces VT episodes but with disappointing incidence of side effects and efficacy.2 Catheter ablation is useful for reducing VT episodes and can be life-saving when VT is incessant.1,5,6 Idiopathic VTs occur in patients without structural heart disease and rarely cause sudden death. Electrophysiological study with catheter ablation is often warranted to confirm the diagnosis, to provide further evidence for the absence of ventricular scar or other disease, and often to cure the arrhythmia. Ablation is also an option for symptomatic nonsustained VT and frequent ventricular ectopy in these patients.1 The appearance of the VT on ECG often suggests its likely cause and associated heart disease (Figure 1). Monomorphic VT has the same QRS complex from beat to beat, indicating repetitive ventricular activation from a structural substrate or focus that can be targeted for ablation. Most are due to reentry through regions of ventricular scar.7 Figure 1. ECG types of VT and most common causes are shown with characteristic ECG features of selected VTs. LBBB indicates left bundle-branch block; LVOT, LV outflow tract; RBBB, right bundle-branch block; L, left; and R, right. Polymorphic VTs have a changing ventricular activation sequence that can be due to …

Reduced Ventricular Volumes and Improved Systolic Function With Cardiac Resynchronization Therapy A Randomized Trial Comparing Simultaneous Biventricular Pacing, Sequential Biventricular Pacing, and Left Ventricular Pacing

Abstract: Background— Cardiac resynchronization therapy has emerged as an important therapy for advanced systolic heart failure. Among available cardiac resynchronization therapy pacing modes that restore ventricular synchrony, it is uncertain whether simultaneous biventricular (BiV), sequential BiV, or left ventricular (LV) pacing is superior. The Device Evaluation of CONTAK RENEWAL 2 and EASYTRAK 2: Assessment of Safety and Effectiveness in Heart Failure (DECREASE-HF) trial is the first randomized trial comparing these 3 cardiac resynchronization therapy modalities. Methods and Results— The DECREASE-HF Trial is a multicenter trial in which 306 patients with New York Heart Association class III or IV heart failure, an LV ejection fraction ≤35%, and a QRS duration ≥150 ms were randomized to simultaneous BiV, sequential BiV, or LV pacing. LV volumes and systolic and diastolic function were assessed with echocardiography at baseline, 3 months, and 6 months. All groups had a significant reduction in LV end-systolic an...

Left Ventricular Resynchronization Is Mandatory for Response to Cardiac Resynchronization Therapy Analysis in Patients With Echocardiographic Evidence of Left Ventricular Dyssynchrony at Baseline

Abstract: Background— Recent studies have demonstrated that a positive response to cardiac resynchronization therapy (CRT) is related to the presence of preimplantation left ventricular (LV) dyssynchrony. The time course and the extent of LV resynchronization after CRT implantation and their relationship to response are currently unknown. Methods and Results— One hundred consecutive patients scheduled for implantation of a CRT device were prospectively included if they met the following criteria: New York Heart Association class III to IV, LV ejection fraction ≤35%, QRS duration >120 ms, and LV dyssynchrony (≥65 ms) on color-coded tissue Doppler imaging. Immediately after CRT implantation, LV dyssynchrony was reduced from 114±36 to 40±33 ms (P 10% reduction in LV end-systolic volume). Immediatel...

Left bundle branch block as a risk factor for progression to heart failure

Abstract: The prevalence of conduction disturbances, particularly left bundle branch block (LBBB), is strongly correlated with age and with the presence of cardiovascular disease. LBBB has been reported to affect approximately 25% of the heart failure (HF) population and it is likely that the deleterious role of such conduction disorders in the progression to HF has been underestimated. The purpose of this article is to review the data from the literature indicating that LBBB may have a causative role, mediated through the resulting intra-ventricular asynchrony, in the deterioration of cardiac function and the development of cardiac remodelling and HF. It also aims to address the potential for future clinical therapies for this conduction disorder.

Comparison of the prognostic significance of the electrocardiographic QRS/T angles in predicting incident coronary heart disease and total mortality (from the atherosclerosis risk in communities study).

Abstract: Spatial QRS/T angle and spatial T-wave axis were shown to be strong independent predictors of incident coronary heart disease (CHD) and total mortality, but they are not routinely available. We evaluated whether frontal plane QRS/T angle, easily obtained as the difference between frontal plane axes of QRS and T, provides a suitable substitute for spatial QRS/T angle as a risk predictor. Our study consisted of 13,973 participants from the ARIC Study. Outcome variables were incident CHD and total mortality during a median follow-up of 14 years. Electrocardiographic variables were categorized as abnormal (≥95th percentile), borderline (≥75th and 50% increased risk. Spatial QRS/T angle was a stronger predictor of incident CHD in women, with a 114% increased risk, but it was not significantly associated with risk of incident CHD in men. Similarly, frontal plane QRS/T angle was statistically significant for only women with a 74% increased risk of incident CHD. In conclusion, frontal plane QRS/T angle as an easily derived risk measure is a suitable clinical substitute for spatial QRS/T angle for risk prediction.

Prognostic significance of fragmented QRS complex for predicting the risk of recurrent cardiac events in patients with Q-wave myocardial infarction.

Abstract: There are limited data regarding the prognostic value of QRS complex fragmentation, defined as changes in QRS morphology ( 1 R' wave. The purpose of our analysis was to assess the prognostic value of presence of Q waves and QRS fragmentation for predicting recurrent cardiac events, defined as cardiac death, nonfatal myocardial infarction (MI), or unstable angina, whichever occurs first, in 350 patients with first Q-wave MI. In follow-up (2 months on average) electrocardiograms (ECGs), 277 patients (79%) had persistent Q waves and 73 (21%) had resolution of Q waves. Independently of Q waves, presence of QRS complex fragmentation was found in 187 patients (53%). Resolved Q waves on 2-month ECGs was associated with worsened prognosis (adjusted hazard ratio [HR] 2.33, p = 0.007), whereas presence of any fragmented QRS did not increase risk of recurrent cardiac events (adjusted HR 0.93, p = 0.79). Among patients for whom Q waves disappeared on 2-month ECGs, patients with QRS fragmentation (n = 37) had over twofold higher risk of recurrent events (adjusted HR 2.68, p = 0.004) compared with those without fragmented QRS and persistent Q waves. In conclusion, presence of fragmented QRS independently of Q waves was not associated with increased risk of recurrent events in the general population of patients after MI. However, among patients with resolved Q waves, fragmented QRS was associated with increased risk of cardiac events. Fragmented QRS complex should not be neglected in patients with transient Q waves after myocardial infarction.

Upgrading from single chamber right ventricular to biventricular pacing in permanently paced patients with worsening heart failure: The RD-CHF Study.

Abstract: Background: Biventricular (BiV) stimulation lowers morbidity and mortality in patients with drug-refractory congestive heart failure (CHF), depressed left ventricular (LV) function, and ventricular dyssynchrony in absence of indication for permanent cardiac pacing. This pilot, single-blind, randomized, cross-over study examined the safety and efficacy of upgrading conventional pacing systems to BiV stimulation in patients with advanced CHF. Methods: We included 56 patients in New York Heart Association (NYHA) functional classes III or IV despite optimal drug treatment and ventricular dyssynchrony (interventriclar delay >40 ms or LV preejection delay >140 ms) in need of pacemaker replacement. We compared the patients' functional status, arrhythmias, and standard echocardiographic measurements during 3 months of conventional, single right ventricular (RV) versus 3 months of BiV stimulation. Results: There were 44 patients in the cross-over phase. QRS duration was shortened by 23% and LV preejection delay by 16% with BiV stimulation. NYHA functional class, 6-minute hall walk and quality of life score were significantly improved with BiV stimulation compared with single RV pacing by 18%, 29%, and 19%, respectively. No significant difference was observed in the ventricular arrhythmia burden or LV reverse remodeling between the 2 periods. Conclusions: This pilot study showed that upgrading from RV pacing to BiV pacing significantly improves symptoms and exercise tolerance in chronically paced patients with advanced CHF and mechanical dyssynchrony.

Right Ventricular Mechanics and QRS Duration in Patients With Repaired Tetralogy of Fallot. Implications of Infundibular Disease

Abstract: Background— Patients after repair of tetralogy of Fallot (ToF) frequently have right ventricular (RV) dysfunction and prolonged QRS duration (QRSd) and thus could be candidates for cardiac resynchronization therapy. We aimed to assess the relationship between QRSd and the timing of RV wall motion, including the RV outflow tract (RVOT), in these patients. Methods and Results— Sixty-seven repaired ToF patients (median age, 34 years; interquartile range, 24 to 43 years) and 35 age-matched control subjects were studied by echocardiography and cardiovascular magnetic resonance (n=55 of 67 ToF patients). Time intervals of the RV cardiac cycle were measured from Doppler recordings. Long-axis M-mode recordings were acquired from the right ventricular (RV) free wall and RV outflow tract (RVOT), and the delay in onset of long-axis shortening was measured. ToF patients showed minor abnormalities of the RV cardiac cycle unrelated to QRSd. RV ejection time was prolonged and correspondingly filling time was reduced com...

Beat-to-beat variability of QT intervals is increased in patients with drug-induced long-QT syndrome: a case control pilot study

Abstract: AIMS: Torsades de pointes arrhythmias (TdP) occur by definition in the setting of prolonged QT intervals. Animal models of drug induced Long-QT syndrome (dLQTS) have shown higher predictive value for proarrhythmia with beat-to-beat variability of repolarization duration (BVR) when compared with QT intervals. Here, we evaluate variability of QT intervals in patients with a history of drug-induced long QT syndrome (dLQTS) and TdP in absence of a mutation in any of the major LQTS genes. METHODS AND RESULTS: Twenty patients with documented TdP under drugs with QT-prolonging potential were compared with 20 matched control individuals. An observer blinded to diagnosis manually measured lead-II, RR, and QT intervals from 30 consecutive beats. BVR was determined from Poincare plots of QT intervals as short-term variability (STV(QT) = Sigma|QT(n)(+1) - QT(n)|/[30 x radical2]). QRS interval and cycle length was comparable between study groups and controls. No difference was found in QTc between dLQTS and controls (428 +/- 25 vs. 421 +/- 34 ms, P = 0.26), whereas STV(QT) was significantly higher in dLQTS when compared with controls (8.1 +/- 3.7 vs. 3.6 +/- 1.3 ms, P = 0.001). Proarrhythmic predictive power of STV(QT) was superior to that of the QTc interval (AUC: 0.89 vs. 0.57, 95% CI: 0.79-0.99 vs. 0.39-0.75). CONCLUSION: In the absence of QTc prolongation, baseline STV(QT) characterized patients with documented drug-induced proarrhythmia. STV(QT) could prove to be a useful non-invasive, easily obtainable parameter aiding the identification of the patient at risk for potentially life threatening arrhythmia in the context of drugs with QT prolonging potential.

Usefulness of QRS duration to predict response to cardiac resynchronization therapy in patients with end-stage heart failure.

Abstract: Despite current selection criteria, 20% to 30% of patients treated with cardiac resynchronization therapy (CRT) do not benefit. It has been suggested that QRS duration may not be the optimal criterion to select patients for CRT. The objective of this study was to systematically evaluate the predictive value of QRS duration for response to CRT in a large group of consecutive patients. A total of 242 patients with heart failure scheduled for implantation of a CRT device were studied. Selection criteria for CRT included moderate to severe heart failure (New York Heart Association classes III to IV), left ventricular ejection fraction (LVEF) ≤35%, and QRS duration >120 ms. Before CRT implantation, QRS duration and clinical status were assessed, and 2-dimensional echocardiography (LV volumes and LVEF) was performed. Clinical status and changes in LVEF and LV volumes were reassessed at 6-month follow-up. After 6 months of CRT, 68% of patients were classified as clinical responders (improvement of ≥1 grade in New York Heart Association class) and 60% as echocardiographic responders (decrease >10% in LV end-systolic volume). At baseline, no significant differences were observed in QRS duration between clinical responders and nonresponders and between echocardiographic responders and nonresponders. No significant relation was demonstrated between baseline QRS duration and improvement in clinical and echocardiographic variables at 6-month follow-up. In conclusion, baseline QRS duration is not predictive for clinical and echocardiographic responses to CRT at 6-month follow-up. Better predictors for CRT response are needed.

Cancellation of Ventricular Activity in the ECG: Evaluation of Novel and Existing Methods

Abstract: Due to the much higher amplitude of the electrical activity of the ventricles in the surface electrocardiogram (ECG), its cancellation is crucial for the analysis and characterization of atrial fibrillation. In this paper, two different methods are proposed for this cancellation. The first one is an average beat subtraction type of method. Two sets of templates are created: one set for the ventricular depolarization waves and one for the ventricular repolarization waves. Next, spatial optimization (rotation and amplitude scaling) is applied to the QRS templates. The second method is a single beat method that cancels the ventricular involvement in each cardiac cycle in an independent manner. The estimation and cancellation of the ventricular repolarization is based on the concept of dominant T and U waves. Subsequently, the atrial activities during the ventricular depolarization intervals are estimated by a weighted sum of sinusoids observed in the cleaned up segments. ECG signals generated by a biophysical model as well as clinical ECG signals are used to evaluate the performance of the proposed methods in comparison to two standard ABS-based methods

An Automated Methodology for Fetal Heart Rate Extraction From the Abdominal Electrocardiogram

Abstract: This paper introduces an automated methodology for the extraction of fetal heart rate from cutaneous potential abdominal electrocardiogram (abdECG) recordings. A three-stage methodology is proposed. Having the initial recording, which consists of a small number of abdECG leads in the first stage, the maternal R-peaks and fiducial points (QRS onset and offset) are detected using time-frequency (t-f) analysis and medical knowledge. Then, the maternal QRS complexes are eliminated. In the second stage, the positions of the candidate fetal R-peaks are located using complex wavelets and matching theory techniques. In the third stage, the fetal R-peaks, which overlap with the maternal QRS complexes (eliminated in the first stage) are found using two approaches: a heuristic algorithm technique and a histogram-based technique. The fetal R-peaks detected are used to calculate the fetal heart rate. The methodology is validated using a dataset of eight short and ten long-duration recordings, obtained between the 20th and the 41st week of gestation, and the obtained accuracy is 97.47%. The proposed methodology is advantageous, since it is based on the analysis of few abdominal leads in contrast to other proposed methods, which need a large number of leads.

Right ventricular mechanical dyssynchrony in children with hypoplastic left heart syndrome.

Abstract: Background Mechanical dyssynchrony predicts response to cardiac resynchronization therapy in adults with heart failure. Children with hypoplastic left heart syndrome (HLHS) are susceptible to right ventricular (RV) failure; however, mechanical dyssynchrony has not been studied in this population with newly available methodologies. We investigated RV mechanical dyssynchrony in children with HLHS using vector velocity imaging. Methods We used vector velocity imaging to quantify the SD of time to peak velocity, strain, and strain rate among 6 RV segments to define intraventricular RV synchrony in 16 children with HLHS and RV and left ventricular (LV) synchrony in 16 healthy age-matched control subjects. We further investigated relations between QRS duration and mechanical dyssynchrony and between mechanical dyssynchrony and systolic function. Results Children with HLHS had significant RV mechanical dyssynchrony versus LV and RV control subjects (strain 37 ± 35 vs 8 ± 8 milliseconds, P = .003 [LV], 9 ± 11 milliseconds, P = .005 [RV]; strain rate 31 ± 37 vs 10 ± 13 milliseconds, P = .04 [LV], 14 ± 15 milliseconds, P = .09 [RV]). There was no significant relationship between QRS duration and mechanical dyssynchrony and no obvious relation between the degree of mechanical dyssynchrony and the RV fractional area of change. Conclusions Children with HLHS have RV mechanical dyssynchrony unrelated to surface electrocardiographic QRS duration. This may contribute to RV dysfunction and may indicate the usefulness of cardiac resynchronization therapy in this population.

Reduced systolic wave generation and increased peripheral wave reflection in chronic heart failure

Abstract: In human heart failure the role of wave generation by the ventricle and wave reflection by the vasculature is contentious. The aim of this study was to compare wave generation and reflection in nor...

QRS template matching for recognition of ventricular ectopic beats.

Abstract: We propose a quasi real-time method for discrimination of ventricular ectopic beats from both supraventricular and paced beats in the electrocardiogram (ECG). The heartbeat waveforms were evaluated within a fixed-length window around the fiducial points (100 ms before, 450 ms after). Our algorithm was designed to operate with minimal expert intervention and we define that the operator is required only to initially select up to three ‘normal’ heartbeats (the most frequently seen supraventricular or paced complexes). These were named original QRS templates and their copies were substituted continuously throughout the ECG analysis to capture slight variations in the heartbeat waveforms of the patient’s sustained rhythm. The method is based on matching of the evaluated heartbeat with the QRS templates by a complex set of ECG descriptors, including maximal cross-correlation, area difference and frequency spectrum difference. Temporal features were added by analyzing the R-R intervals. The classification criteria were trained by statistical assessment of the ECG descriptors calculated for all heartbeats in MIT-BIH Supraventricular Arrhythmia Database. The performance of the classifiers was tested on the independent MIT-BIH Arrhythmia Database. The achieved unbiased accuracy is represented by sensitivity of 98.4% and specificity of 98.86%, both being competitive to other published studies. The provided computationally efficient techniques enable the fast post-recording analysis of lengthy Holter-monitor ECG recordings, as well as they can serve as a quasi real-time detection method embedded into surface ECG monitors.

Magnetocardiographic determination of the developmental changes in PQ, QRS and QT intervals in the foetus.

Abstract: In order to determine developmental changes in atrioventricular (PQ), ventricular depolarizing (QRS) and QT intervals of the foetal heart, we recorded foetal magnetocardiographic waveforms using a superconducting quantum interference device system in a magnetically shielded room in 150 uncomplicated foetuses of gestational age >20 wk. Recording of the QRS waveform was successful in 128 (85%) of the subjects, based on unaveraged tracings. After signal averaging of the data from these 128 cases, P waves were recognized in 102 (68%) subjects and T waves in 64 (43%). The QRS interval, ranging from 32-74 ms, showed a positive linear correlation with the gestational age, which probably reflects an increase in the number and size of myocardial cells. The PQ interval showed low correlation with the gestational age, and was rather constant, with an average value of 100 ms. The QT interval ranged from 180-302 ms, and tended to be slightly shorter during early gestation. Although the success rate of measuring the PQ and QT intervals was unsatisfactory for this methodology to prevail in a clinical setting, these values provide the basis for in utero non-invasive investigation of foetal cardiac activity by magnetocardiography.

Comparison of long-term follow-up of electrocardiographic features in Brugada syndrome between the SCN5A-positive probands and the SCN5A-negative probands.

Abstract: To investigate changes of electrocardiographic parameters with aging and their relation to the presence of SCN5A mutation in probands with Brugada syndrome (BS), we measured several electrocardiographic parameters prospectively during long-term follow-up (10 ± 5 years) in 8 BS probands with SCN5A mutation (SCN5A-positive group, all men; age 46 ± 10 years) and 36 BS probands without SCN5A mutation (SCN5A-negative group, all men; age 46 ± 13 years). Throughout the follow-up period, depolarization parameters, such as P-wave (lead II), QRS (leads II, V 2 , V 5 ), S-wave durations (leads II, V 5 ), and PQ interval (leads II) were all significantly longer and S-wave amplitude (II, V 5 ) was significantly deeper in the SCN5A-positive group than in the SCN5A-negative group. The SCN5A-positive group showed a significantly longer corrected QT interval (lead V 2 ) and higher ST amplitude (lead V 2 ) than those in the SCN5A-negative group. The depolarization parameters increased with aging during the follow-up period in both groups; however, the PQ interval (lead II) and QRS duration (lead V 2 ) were prolonged more prominently and the QRS axis deviated more to the left with aging in the SCN5A-positive group than in the SCN5A-negative group. In conclusion, conduction slowing was more marked and more progressively accentuated in Brugada probands with SCN5A mutation than in those without SCN5A mutation.