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Showing papers on "QRS complex published in 2002"


Journal ArticleDOI
TL;DR: Cardiac resynchronization results in significant clinical improvement in patients who have moderate-to-severe heart failure and an intraventricular conduction delay.
Abstract: Background Previous studies have suggested that cardiac resynchronization achieved through atrial-synchronized biventricular pacing produces clinical benefits in patients with heart failure who have an intraventricular conduction delay. We conducted a double-blind trial to evaluate this therapeutic approach. Methods Four hundred fifty-three patients with moderate-to-severe symptoms of heart failure associated with an ejection fraction of 35 percent or less and a QRS interval of 130 msec or more were randomly assigned to a cardiac-resynchronization group (228 patients) or to a control group (225 patients) for six months, while conventional therapy for heart failure was maintained. The primary end points were the New York Heart Association functional class, quality of life, and the distance walked in six minutes. Results As compared with the control group, patients assigned to cardiac resynchronization experienced an improvement in the distance walked in six minutes (+39 vs. +10 m, P=0.005), functional clas...

4,329 citations


01 Jan 2002
TL;DR: In this article, the authors evaluated the effect of implantable defibrillator on survival in patients with a prior myocardial infarction and a left ventricular ejection fraction of 0.30 or less.
Abstract: A BSTRACT Background Patients with reduced left ventricular function after myocardial infarction are at risk for lifethreatening ventricular arrhythmias. This randomized trial was designed to evaluate the effect of an implantable defibrillator on survival in such patients. Methods Over the course of four years, we enrolled 1232 patients with a prior myocardial infarction and a left ventricular ejection fraction of 0.30 or less. Patients were randomly assigned in a 3:2 ratio to receive an implantable defibrillator (742 patients) or conventional medical therapy (490 patients). Invasive electrophysiological testing for risk stratification was not required. Death from any cause was the end point. Results The clinical characteristics at base line and the prevalence of medication use at the time of the last follow-up visit were similar in the two treatment groups. During an average follow-up of 20 months, the mortality rates were 19.8 percent in the conventional-therapy group and 14.2 percent in the defibrillator group. The hazard ratio for the risk of death from any cause in the defibrillator group as compared with the conventional-therapy group was 0.69 (95 percent confidence interval, 0.51 to 0.93; P=0.016). The effect of defibrillator therapy on survival was similar in subgroup analyses stratified according to age, sex, ejection fraction, New York Heart Association class, and the QRS interval. Conclusions In patients with a prior myocardial infarction and advanced left ventricular dysfunction, prophylactic implantation of a defibrillator improves survival and should be considered as a recommended therapy. (N Engl J Med 2002;346:877-83.)

2,060 citations


Journal Article
TL;DR: In patients with a prior myocardial infarction and advanced left ventricular dysfunction, prophylactic implantation of a defibrillator improves survival and should be considered as a recommended therapy.
Abstract: Background: Patients with reduced left ventricular function after myocardial infarction are al risk for life threatening ventricular arrhythmias. This randomized trial was designed to evaluate the effect of an implantabledefibrillator on survival in such patients. Methods: Over the course of four years, we enrolled 1232 patients with a prior myocardial infarction and a left ventricular ejection fraction of 0.30 or less. Patients were randomly assigned in a 3:2 ratio to receive an implantable defibrillator (742 patients) or conventional medical therapy (490 patients). Invasive electrophysiological testing for risk stratification was not required. Death from any cause was the end point. Results: The clinical characteristics at base line and the prevalence of medication use at the time of the last follow-up visit were similar in the two treatment groups. During an average follow-up of 20 months. the mortality rates were 19.8 percent in the conventional-therapy group and 14.2 percent in the defibrillator group. The hazard ratio for the risk of death from any cause in the defibrillator group as compared with the conventional-therapy group as 0.69 (95 percent confidence interval, 0.51 to 0.93; P=0.016). The effect of defibrillator therapy on survival was similar in sub-group analyses stratified according to age, sex, ejection fraction. New York heart Association class, and the QRS interval. Conclusions: In patients with a prior myocardial infarction and advanced left ventricular dysfunction, prophylactic implantation of a defibrillator improves suvival and should beconsidered as a recommended therapy.

1,366 citations


Journal ArticleDOI
TL;DR: The authors provide an overview of these recent developments as well as of formerly proposed algorithms for QRS detection, which reflects the electrical activity within the heart during the ventricular contraction.
Abstract: The QRS complex is the most striking waveform within the electrocardiogram (ECG). Since it reflects the electrical activity within the heart during the ventricular contraction, the time of its occurrence as well as its shape provide much information about the current state of the heart. Due to its characteristic shape it serves as the basis for the automated determination of the heart rate, as an entry point for classification schemes of the cardiac cycle, and often it is also used in ECG data compression algorithms. In that sense, QRS detection provides the fundamentals for almost all automated ECG analysis algorithms. Software QRS detection has been a research topic for more than 30 years. The evolution of these algorithms clearly reflects the great advances in computer technology. Within the last decade many new approaches to QRS detection have been proposed; for example, algorithms from the field of artificial neural networks genetic algorithms wavelet transforms, filter banks as well as heuristic methods mostly based on nonlinear transforms. The authors provide an overview of these recent developments as well as of formerly proposed algorithms.

1,307 citations


Journal ArticleDOI
TL;DR: In patients with advanced heart failure and LBBB, baseline SPWMD is a strong predictor of the occurrence of reverse remodeling after CRT, thus suggesting its usefulness in identifying patients likely to benefit from biventricular pacing.

741 citations


Journal ArticleDOI
TL;DR: QRS prolongation is an independent predictor of both increased total mortality and sudden death in patients with heart failure and age, type of cardiomyopathy, and drug treatment group were not predictive of mortality.

395 citations


Journal ArticleDOI
TL;DR: Long-term resynchronization therapy results in atrial and ventricular reverse remodeling and improved hemodynamics, including left ventricular outflow tract and aortic velocity time integral and myocardial performance index, improved.
Abstract: Background— Long-term ventricular resynchronization therapy improves symptom status. Changes in left ventricular remodeling have not been adequately evaluated. Methods and Results— Fifty-three patients with systolic heart failure and bundle-branch block underwent implantation of biventricular stimulation (BVS) devices as part of a randomized trial. Echocardiograms were acquired at randomization and at 6-week intervals until completion of 12 weeks of continuous BVS. There were no changes in heart rate or QRS duration after 12 weeks of BVS. Serum norepinephrine values did not change with BVS. After 12 weeks of BVS, left atrial volume decreased. Left ventricular end-systolic and end-diastolic dimensions and left ventricular end-systolic volume also decreased after 12 weeks of BVS. Sphericity index did not change. Measures of systolic function, including left ventricular outflow tract and aortic velocity time integral and myocardial performance index, improved. Conclusions— Long-term resynchronization therapy...

294 citations


Journal ArticleDOI
TL;DR: This study was designed to assess the safety and feasibility of an atrio‐biventricular transvenous pacing system, and examine the long‐term effects of cardiac resynchronization in patients with advanced heart failure and ventricular conduction abnormalities.
Abstract: Background: recent short-term observations have shown an improvement in cardiac function and heart failure symptoms from atrio-biventricular pacing. This study was designed to assess the safety and feasibility of an atrio-biventricular transvenous pacing system, and examine the long-term effects of cardiac resynchronization in patients with advanced heart failure and ventricular conduction abnormalities. Methods and results: between August, 1997 and November, 1998, 103 patients received a cardiac resynchronization system (CRS) consisting of a pulse generator interfaced with an atrio-biventricular lead system, including a lead designed for left ventricular (LV) pacing via cardiac veins. Baseline evaluation included 12-lead electrocardiogram, estimation of New York Heart Association (NYHA) functional class, assessment of quality of life (QOL), and distance covered during a 6-min walk (6-MW). Detailed echocardiographic data were also collected in a subset of 46 patients. Measurements were repeated in all surviving patients at 1, 3, 6 and 12 months after implantation of the CRS. A single, self-limiting procedure-related complication occurred. Over a follow-up of 12 months, 21 patients died. The 12-month actuarial survival was 78% (CI 70–87%). Nine surviving patients were withdrawn from the study during long-term follow-up for miscellaneous reasons. At each point of follow-up, a significant shortening of QRS duration was measured. In addition, significant improvements were observed in mean NYHA functional class, 6-MW and QOL score. In the 46 patients with complete echocardiographic data, LV ejection fraction increased from 21.7±6.4% at baseline to 26.1±9.0% at last follow-up (P-0.006), LV end diastolic dimension decreased from 72.7±9.2 to 71.6±9.1 mm (P-0.233), interventricular mechanical delay decreased from 27.5±32.1 to 20.3±25.5 ms (P-0.243), mitral regurgitation apical four-chamber area decreased from 7.66±5.5 to 6.69±5.9 cm2 (P-0.197), and left ventricular filling time increased from 363±127 to 408±111 ms (P-0.002). Conclusions: long-term cardiac resynchronization can be safely and reliably achieved by transvenous atrial synchronized right and left ventricular pacing. These changes were accompanied by clinically relevant improvements in functional status and QOL, as well as a measurable increase in LV performance. The outcome of randomised controlled trials is awaited.

283 citations


Journal ArticleDOI
TL;DR: Experimental findings justify continuing attention for optimizing the site(s) of ventricular pacing in patients with normal and abnormal ventricular impulse conduction, and differences in LV pump function between (combinations of) pacing sites are poorly correlated with QRS duration.
Abstract: The main goal of this article was to review animal experimental work on the effect of asynchronous activation on ventricular pump function. During normal sinus rhythm and atrial pacing, the Purkinje system contributes significantly to the rapid electrical activation of the ventricles. In contrast, during ventricular pacing the impulse is almost exclusively conducted through the normal myocardium. As a consequence, electrical activation of the ventricles becomes asynchronous and has an abnormal sequence. The abnormal impulse conduction causes considerable disturbances to occur in regional systolic fiber shortening, mechanical work, blood flow, and oxygen consumption; low values occurring in early activated regions and values above normal being present in late activated regions. Many animal studies have now shown that the abnormal electrical activation, induced by ventricular pacing, leads to a depression of systolic and diastolic LV function. Pacing at the right ventricular apex (the conventional pacing site) reduces LV function more than pacing at the high ventricular septum or at LV sites. In canine hearts with experimental LBBB, LV pacing significantly improves LV pump function. Differences in LV pump function between (combinations of) pacing sites are poorly correlated with QRS duration. Therefore, the cause of the depression of LV function during abnormal electrical activation appears to be a combination of the asynchrony and the sequence of activation. These experimental findings justify continuing attention for optimizing the site(s) of ventricular pacing in patients with normal and abnormal ventricular impulse conduction.

283 citations


Journal ArticleDOI
01 Aug 2002-Chest
TL;DR: Almost 20% of a generalized heart failure population can be expected to have a prolonged QRS duration within the first year of diagnosis, suggesting that as many as20% of patients with heart failure may be candidates for biventricular pacing.

235 citations


Journal ArticleDOI
TL;DR: Local electrograms may be related to a myocardial abnormality in the epicardium of patients with the Brugada syndrome and can be recorded from the conus branch of the right coronary artery.

Journal ArticleDOI
TL;DR: In this article, the authors evaluated the prognostic value of interventricular and intraventricular dyssynchrony in idiopathic dilated cardiomyopathy (IDC).

Journal ArticleDOI
TL;DR: The characteristics and technique of catheter ablation from both the left and right coronary cusps to cure left ventricular outflow tract ventricular tachycardia are established.
Abstract: Catheter Ablation of LVOT VT from a Coronary Cusp. Introduction: Although radiofrequency energy usually is applied to the most favorable endocardial site in patients with outflow tract ventricular tachycardia, there are still some patients in whom the tachycardia can be ablated only from an epicardial site. We established the characteristics and technique of catheter ablation from both the left and right coronary cusps to cure left ventricular outflow tract ventricular tachycardia. Methods and Results: We studied 15 patients in whom VT was thought to originate from the coronary cusp by both activation and pace mapping after precise mapping of the right ventricle, left ventricle, pulmonary artery, coronary cusps, and anterior interventricular vein. Twelve-lead ECG analysis revealed an S wave on lead I, tall R wave on leads II, III, and aVF, and no S wave on either lead V 5 or V 6 . Precordial R wave transition occurred on leads V 1 and V 2 . The earliest ventricular electrogram at a successful ablation site was recorded 35 ′ 12 msec before QRS onset and 19 ′ 15 msec earlier than the earliest ventricular electrogram recorded from the anterior interventricular vein. Almost identical pace mappings were obtained from the coronary cusp. Catheter tip temperature was maintained at 55°C during energy delivery, and the distance from the tip to the ostium of each left and right coronary artery was >1.0 cm by coronary angiography. Conclusion: Left ventricular outflow tract VT that could not be ablated from an endocardial site could be safely eliminated by radiofrequency application to the left and right coronary cusps.

Journal ArticleDOI
TL;DR: A modified combined wavelet transform technique that has been developed to analyse multilead electrocardiogram signals for cardiac disease diagnostics and two alternate diagnostic criteria have been used to check the diagnostic authenticity of the test results.
Abstract: This paper deals with a modified combined wavelet transform technique that has been developed to analyse multilead electrocardiogram signals for cardiac disease diagnostics. Two wavelets have been used, i.e. a quadratic spline wavelet (QSWT) for QRS detection and the Daubechies six coefficient (DU6) wavelet for P and T detection. After detecting the fundamental electrocardiogram waves, the desired electrocardiogram parameters for disease diagnostics are extracted. The software has been validated by extensive testing using the CSE DS-3 database and the MIT/BIH database. A procedure has been evolved using electrocardiogram parameters with a point scoring system for diagnosis of cardiac diseases, namely tachycardia, bradycardia left ventricular hypertrophy, and right ventricular hypertrophy. As the diagnostic results are not yet disclosed by the CSE group, two alternate diagnostic criteria have been used to check the diagnostic authenticity of the test results. The consistency and reliability of the identifi...

Journal ArticleDOI
TL;DR: A filtered QRS duration >114 ms (abnormal SAECG) independently predicted the primary end point and cardiac death, independent of clinical variables, cardioverter-defibrillator implantation, and antiarrhythmic drug therapy.
Abstract: Background An abnormal signal-averaged ECG (SAECG) is a noninvasive marker of the substrate of sustained ventricular tachycardia after myocardial infarction. We assessed its prognostic ability in patients with asymptomatic unsustained ventricular tachycardia, coronary artery disease, and left ventricular dysfunction. Methods and Results A blinded core laboratory analyzed SAECG tracings from 1925 patients in a multicenter trial. Cox proportional hazards modeling was used to examine individual and joint relations between SAECG variables and arrhythmic death or cardiac arrest (primary end point), cardiac death, and total mortality. We also assessed the prognostic utility of SAECG at different levels of ejection fraction (EF). A filtered QRS duration >114 ms (abnormal SAECG) independently predicted the primary end point and cardiac death, independent of clinical variables, cardioverter-defibrillator implantation, and antiarrhythmic drug therapy. With an abnormal SAECG, the 5-year rates of the primary end poin...

Journal ArticleDOI
TL;DR: CRT improves hemodynamic performance in patients with heart failure with intraventricular conduction delays, and FT, AO(VTI), and MPI are useful parameters for noninvasive follow-up and optimization of pacing parameters.

Journal ArticleDOI
TL;DR: The data suggest that induction of VF by PVS depends on the severity ofdepolarization abnormalities but does not predict the recurrence of cardiac events in symptomatic Brugada syndrome, indicating that both depolarization and repolarization irregularities are important in the development of Vf.

Journal ArticleDOI
01 Aug 2002-Chest
TL;DR: The ECG is an inadequate screening tool to rule out the presence of clinically relevant pulmonary hypertension, either primary or secondary to collagen vascular disease.

Journal ArticleDOI
01 Jul 2002-Heart
TL;DR: A single measurement of QRSduration has significant prognostic value in elderly patients with heart failure and the increase in QRS duration over time is an even better predictor of adverse out comes.
Abstract: Aims: To investigate the hypothesis that changes in the ECG over time may be an important and readily available marker of prognostic value in patients with heart failure. Methods: 112 elderly patients (81 men) with stable heart failure, a mean (SD) age of 73.3 (4.4) years, left ventricular ejection fraction 38 (17)%, and peak oxygen consumption 15.1 (4.7) ml/kg/min had ECG measurements on two occasions a minimum of 12 (5) months apart. Results: During the subsequent follow up period (mean 27 (17) months) 45 patients died. QRS duration (p = 0.001) and heart rate (p = 0.03) at baseline were found by Cox proportional hazard method analysis to predict adverse outcomes in these patients. Of the changes in ECG parameters between the first and second visit, broadening of QRS duration (p = 0.001) predicted mortality. On Kaplan-Meier survival analysis, patients with 20% increase in QRS duration was associated with the worst prognosis. Progressive prolongation of QRS duration correlated closely with deterioration of LV systolic and diastolic function. Conclusion: A single measurement of QRS duration has significant prognostic value in elderly patients with heart failure and the increase in QRS duration over time is an even better predictor of adverse out comes.

Journal ArticleDOI
01 Jun 2002-BMJ
TL;DR: The most common changes associated with hyperkalaemia are tall, peaked T waves, reduced amplitude and eventually loss of the P wave, and marked widening of the QRS complex.
Abstract: To function correctly, individual myocardial cells rely on normal concentrations of biochemical parameters such as electrolytes, oxygen, hydrogen, glucose, and thyroid hormones, as well as a normal body temperature. Abnormalities of these and other factors affect the electrical activity of each myocardial cell and thus the surface electrocardiogram. Characteristic electrocardiographic changes may provide useful diagnostic clues to the presence of metabolic abnormalities, the prompt recognition of which can be life saving. It is important to recognise that some electrocardiographic changes are due to conditions other than cardiac disease so that appropriate treatment can be given and unnecessary cardiac investigation avoided Increases in total body potassium may have dramatic effects on the electrocardiogram. The most common changes associated with hyperkalaemia are tall, peaked T waves, reduced amplitude and eventually loss of the P wave, and marked widening of the QRS complex. View this table: Electrocardiographic features of hyperkalaemia The earliest changes associated with hyperkalaemia are tall T waves, best seen in leads II, III, and V2 to V4. Tall T waves are usually seen when the potassium concentration rises above 5.5-6.5 mmol/l. However, only about one in five hyperkalaemic patients will have the classic tall, symmetrically narrow and peaked T waves; the rest will merely have large amplitude T waves. Hyperkalaemia should always be suspected when the amplitude of the T wave is greater than or equal to that of the R wave in more than one lead. Serial changes in hyperkalaemia As the potassium concentration rises above 6.5-7.5 mmol/l, changes are seen in the PR interval and the P wave: the P wave widens and flattens and the PR segment lengthens. As the concentration rises, the P waves may disappear. The QRS complex will begin to widen with a potassium concentration of 7.0-8.0 mmol/l. Unlike right or left bundle branch blocks, the QRS …

Journal ArticleDOI
TL;DR: In both women and men, repolarization irregularity was greatest during morning hours, and there were substantial sex differences in both global repolarized homogeneity and regional homogeneity.
Abstract: The reason for sex differences in arrhythmic risk remains unclear. Heterogeneity of ventricular repolarization is directly linked to arrhythmogenesis; thus we investigated repolarization homogeneity and its circadian pattern in men and women. During 24-h Holter recordings in 60 healthy subjects (27 males), a 12-lead electrocardiogram (ECG) was obtained every 30 s. RR and QT intervals, and, after singular-value decomposition, two characteristics of repolarization homogeneity were calculated in each ECG. Corrected QT (QTc) values were obtained using an individually optimized heart rate (HR) correction formula. All values were averaged over 10-min time bands from 0000 to 2400. There were substantial sex differences in both global repolarization homogeneity (measured by the total cosine of the angle between QRS and T wave vectors) and regional homogeneity of repolarization (quantified independently by the relative T wave residuum). Whereas women throughout the 24 h followed more closely the pattern of inverse sequence between depolarization and repolarization, they also showed much higher localized repolarization heterogeneity than men. In both women and men, repolarization irregularity was greatest during morning hours. A sex difference was also observed for HR and QTc interval; however, the circadian patterns of the repolarization homogeneity descriptors were different from those of HR and QTc intervals.

Journal ArticleDOI
TL;DR: A method is presented for automatic analysis of the P-wave, based on lead II of a 12-lead standard ECG, in resting conditions during a routine examination for the detection of patients prone to atrial fibrillation (AF), one of the most prevalent arrhythmias.
Abstract: A method is presented for automatic analysis of the P-wave, based on lead II of a 12-lead standard ECG, in resting conditions during a routine examination for the detection of patients prone to atrial fibrillation (AF), one of the most prevalent arrhythmias. First, the P-wave was delineated, and this was achieved in two steps: the detection of the QRS complexes for ECG segmentation, using a wavelet analysis method, and a hidden Markov model to represent one beat of the signal for P-wave isolation. Then, a set of parameters to detect patients prone to AF was calculated from the P-wave. The detection efficiency was validated on an ECG database of 145 patients, including a control group of 63 people and a study group of 82 patients with documented AF. A discriminant analysis was applied, and the results obtained showed a specificity and a sensitivity between 65% and 70%.

Journal ArticleDOI
TL;DR: Biventricular pacing resulted in improvement of symptoms and quality of life, accompanied by improvement in 6-minute walking distance and LVEF, and 2-year survival was excellent.
Abstract: Biventricular pacing has been introduced to treat patients with end-stage heart failure, and short-term results of this technique are promising. Because data on longer follow-up are limited to 3-month follow-up, the sustained effect of biventricular pacing is unclear and long-term survival is unknown. Forty patients with end-stage heart failure in New York Heart Association (NYHA) functional class III or IV with left ventricular (LV) ejection fraction (EF) 120 ms, and left bundle branch block morphology received a biventricular pacemaker. At baseline, and at 3 and 6 months after implantation, the following parameters were evaluated: NYHA class, Minnesota quality-of-life score, QRS duration on surface electrocardiogram, 6-minute walking distance, and LVEF. Long-term follow-up was obtained for up to 2 years. All clinical parameters improved significantly at 3 months and remained unchanged at 6-month follow-up. LVEF increased from 24 ± 9% to 34 ± 11%. Before implantation, patients were hospitalized (for congestive heart failure) an average of 3.9 ± 5.3 days/year compared with 0.5 ± 1.5 days/year after implantation. Long-term follow-up showed a survival of 87.5% at 2 years. Thus, biventricular pacing resulted in improvement of symptoms and quality of life, accompanied by improvement in 6-minute walking distance and LVEF. These effects were observed at 3 months after implantation and were maintained at 6-month follow-up. Moreover, 2-year survival was excellent.

Journal ArticleDOI
TL;DR: This approach proves to be more effective in patients with postinfarction ventricular tachycardias, in comparison to patients with arrhythmogenic right ventricular dysplasia and idiopathic dilated cardiomyopathy, given the favourable acute and clinical long-term results.
Abstract: Aims The role of a novel non-contact mapping system (ESI 3000, Endocardial Solutions) to guide radiofrequency catheter ablation of untolerated ventricular tachycardia was investigated in 17 patients; 11 with prior myocardial infarction, three with arrhythmogenic right ventricular dysplasia, and three with idiopathic dilated cardiomyopathy. Methods Twenty-seven monomorphic ventricular tachycardias were induced (mean cycle 320±60ms, range 230–450ms), mapped for 15–20s, and terminated by overdrive pacing or DC shock. Off-line analysis of isopotential activation mapping was performed to identify the diastolic pathway and/or the exit point of the ventricular tachycardia reentry circuit. Radiofrequency current was applied to create a line of block across the diastolic pathway or around the exit point. Results All 27 ventricular tachycardias were mapped with the non-contact system. The endocardial exit point (−7±15ms before QRS onset) was defined in 21/21 postinfarction ventricular tachycardias, in 3/3 arrhythmogenic right ventricular dysplasia and in 1/3 idiopathic dilated cardiomyopathy ventricular tachycardias, respectively. The diastolic pathway (earliest endocardial diastolic activity: −65±49ms before QRS onset) was identified in 17/21 postinfarction ventricular tachycardias, in 1/3 arrhythmogenic right ventricular dysplasia and in 1/3 idiopathic dilated cardiomyopathy ventricular tachycardias, respectively. Catheter ablation was performed in 25/27 ventricular tachycardias (93%) in 15/17 patients (88%): 16/25 ventricular tachycardias (64%) were successfully ablated in 10/17 patients (59%). Catheter ablation was not performed in two patients or proved unsuccessful in five patients. At a follow-up of 15±5 months, there was no recurrence of documented ventricular tachycardia in all 10 patients with successful catheter ablation; in two of them a previously non-documented ventricular tachycardia occurred. A high recurrence of ventricular tachycardia was observed in patients with a failed procedure (5/7: 71%). No major complication or death occurred. Conclusions Non-contact mapping can be effectively used to map and guide radiofrequency catheter ablation of untolerated ventricular tachycardias. Given the favourable acute and clinical long-term results, this approach proves to be more effective in patients with postinfarction ventricular tachycardias, in comparison to patients with arrhythmogenic right ventricular dysplasia and idiopathic dilated cardiomyopathy.

Journal ArticleDOI
TL;DR: P wave signal‐averaged electrocardiography (SAECG) has been shown to have a potential role in identifying patients at risk of developing paroxysmal AF and those likely to change from paroxYSmal AF to chronic AF, and combining P wave duration with other predictors for AF improves the diagnostic value of P wave SAECG.
Abstract: AF is the most common sustained cardiac arrhythmia, and this prevalence is increasing. The impact of AF on morbidity and mortality is substantial, as are the socioeconomic consequences like higher health care costs, chronic disease management, and disabilities. Early recognition of patients at high risk for AF, combined with effective management, may help prevent AF from becoming chronic, helping to minimize potential health risks, costs, and other complications. P wave signal-averaged electrocardiography (SAECG) has been shown to have a potential role in identifying patients at risk of developing paroxysmal AF and those likely to change from paroxysmal AF to chronic AF. The theoretical rationale of P wave SAECG in patients with AF is delay in the intraatrial and interatrial conduction. Intraatrial conduction delays can be seen on the surface electrocardiogram as P wave prolongation, which is more visible with averaging techniques and high resolution recording devices. Averaging followed by amplification after proper filtering of the electrical signal allows more precise measurements of duration and amplitude of the P wave. Data on reproducibility, filter settings, number of beats to be averaged, and definitions of the onset and offset depend on the system used, which can be QRS or, preferably, P wave triggered. A prolonged P wave duration is one of the best predictors of perioperative AF, but the role of P wave SAECG in the paroxysmal form is less well defined. Combining P wave duration with other predictors for AF improves the diagnostic value of P wave SAECG.

Journal ArticleDOI
TL;DR: The optimum QRS duration for stratifying patients for medium to long-term event-free survival was 120 ms, and heart failure patients with moderate QRS prolongation share similar impairment of exercise capacity and functional class to those with severe prolongation.

Patent
21 Oct 2002
TL;DR: In this paper, a method and system for associating ECG waveform data with medical imaging data using ECG gating for dose reduction and image improvement by generating the ECG Waveform data using an electrocardiogram device is presented.
Abstract: A method and system for associating ECG waveform data with medical imaging data using ECG gating for dose reduction and image improvement by generating the ECG waveform data using an electrocardiogram device. The ECG data is first validated and then QRS complexes are detected using a detection function. An underlying cardiac rhythm based on the detected QRS complexes is analyzed and an even number N of substantially normally shaped consecutive QRS complexes are selected. An RR interval between consecutive QRS complexes is computed to yield N−1 intervals. Duration of a representative cardiac cycle by averaging at least a plurality of the N−1 intervals is determined. Once a representative cardiac cycle is determined, a method to control power and improve image quality with the presence of patient's having arrhythmias is disclosed.

Journal ArticleDOI
01 Nov 2002-Heart
TL;DR: In patients operated on for tetralogy of Fallot and with pulmonary regurgitation, ECG predictors of ventricular arrhythmias are influenced by several mechanical factors that may occur simultaneously, which include increased right ventricular volume, but also increases in left Ventricular volume and in right and left ventricular wall mass.
Abstract: Background: In patients with the tetralogy of Fallot, QRS prolongation predicts malignant ventricular arrhythmias. QRS prolongation may result from right ventricular dilatation. The relation of ECG markers to biventricular wall mass and volumes has not been assessed. Objective: To investigate the relations of surface ECG markers of depolarisation and repolarisation to right and left ventricular volume and biventricular wall mass. Methods: 37 Fallot patients (mean (SD) age 17 (9) years) were studied 14 (8) years after surgical repair; 34 had important pulmonary regurgitation. Left and right ventricular size was assessed from tomographic magnetic resonance imaging (MRI), and the amount of pulmonary regurgitation by velocity mapping MRI. QT, QRS, and JT duration and interlead dispersion markers were derived from a standard 12 lead ECG. Results: Mean QRS duration was significantly prolonged (133 (31) v 91 (11) ms in controls), as were dispersion of QRS (36 (17) v 20 (6) ms), QT interval (87 (48) v 42 (20) ms), and JT interval (93 (48) v 42 (19) ms). Biventricular volumes were increased (right ventricular end diastolic volume, 129 (41) v 70 (9) ml/m2; left ventricular end diastolic volume, 83 (16) v 69 (10) ml/m2), as was right ventricular wall mass (24 (7) v 17 (2) g/m2). QRS duration correlated best with right ventricular mass (r = 0.55, p < 0.01). Conclusions: In patients operated on for tetralogy of Fallot and with pulmonary regurgitation, ECG predictors of ventricular arrhythmias are influenced by several mechanical factors that may occur simultaneously. These include increased right ventricular volume, but also increases in left ventricular volume and in right and left ventricular wall mass.

Proceedings ArticleDOI
22 Sep 2002
TL;DR: A QRS complex detection algorithm was developed using the available leads of the electrocardiogram (ECG) using the combination of two improved versions of QRS detectors available in the literature.
Abstract: A QRS complex detection algorithm was developed using the available leads of the electrocardiogram (ECG). This detector is based on the combination of two improved versions of QRS detectors available in the literature. An important characteristic of this algorithm is the possibility of using two or more ECG channels for QRS detection. The first detection method is based on a cross number in a detection threshold defined by the authors. When a low reliability situation occurs in the first method, the output of the second detection method is used to confirm or reject the detection. The second method also uses an adaptive detection threshold defined by the authors and a candidate QRS is tested against some criteria that use features as amplitude, width and RR interval to validate the candidate as a QRS. Testing the algorithm with MIT/BIH Arrhythmia Database resulted in 99.22% sensitivity and 99.73% positive predictivity.

Journal ArticleDOI
TL;DR: In this article, the location of the accessory pathway (AP) in Wolff-Parkinson-White (WPW) syndrome can be determined accurately by the QRS polarity on resting ECG.
Abstract: AP Localization by QRS Polarity in Children. Introductions: Location of the accessory pathway (AP) in Wolff-Parkinson-White (WPW) syndrome can be determined accurately by the QRS polarity on resting ECG. These ECG characteristics may be different in children, and no algorithm has yet been tested. Methods and Results: A total of 153 resting ECGs of symptomatic children with WPW syndrome were retrospectively analyzed. The anatomic AP location had been established fluoroscopically at eight possible sites during radiofrequency catheter ablation. Two independent observers predicted AP location on blinded ECGs with a QRS polarity algorithm for adults using leads II, III, aVL, V 1 , and V 2 . Subsequently, the QRS polarity for all individual ECG leads was evaluated and a new algorithm for children was devised. With the adult algorithm, the observers correctly predicted only 55% to 58 % of AP locations. The septal and right-sided pathways often were inseparable, and mid-septal and parahisian pathways were missed. In the new children's algorithm, left lateral, left posteroseptal, and posteroseptal pathways shared a positive or intermediate QRS polarity on V 1 , with the left lateral pathway separated by a positive QRS polarity on lead III. Negative QRS polarity on lead V 1 and positive QRS polarity on lead V 3 were shared by right posteroseptal, mid-septal, parahisian, and anteroseptal pathways, with the latter two having a positive QRS polarity on lead aVF. Right lateral pathways had negative QRS polarity on lead V 1 and negative or intermediate QRS polarity on lead V 3 . Overall accuracy for these five regions was 90%. Conclusion: AP characterization by QRS polarity in children with WPW syndrome is more diverse than in adults and requires other ECG leads to establish five AP regions.