Comparison of de novo implantation vs. upgrade cardiac resynchronisation therapy: a multicentre experience.

BACKGROUND: The clinical safety and consequences of upgrade procedures compared with de novo cardiac resynchronisation therapy (CRT) implantation in heart failure remain unclear. The present study aimed to assess clinical and procedural consequences of patients undergoing CRT upgrade as compared to de novo CRT implantations. METHODS: In this prospective cohort study, two subgroups were considered as the study population as (1) de novo group that CRT was considered on optimised medical treatment with heart failure of NYHA functional class from II to IV, left ventricular ejection fraction (LVEF) of ≤35%, and QRS width of >130 ms and (2) upgrade group including the patients with previously implantable cardioverter defibrillator (ICD) with the indications for upgrading to CRT. The two groups were compared regarding the changes in clinical outcome and echocardiography parameters. RESULTS: The procedure was successful in 95.9% of patients who underwent CRT upgrade and 100% of those who underwent de novo CRT implantation. It showed a significant improvement in LVEF, severity of mitral regurgitation and NYHA functional classification, without any difference between the two study groups. Overall procedural related complications were reported in 10.8% and 3.8% (p = .093) and cardiac death in 5.4% and 2.5% (p = .360), respectively, with no overall difference in postoperative outcome between the two groups. CONCLUSIONS: Upgrading to CRT is a safe and effective procedure regarding improvement of functional class, left ventricular function status and post-procedural outcome.

QTc interval measurement in patients with right bundle branch block: A practical method.

BACKGROUND AND AIM: Prolonging the QT interval in the right bundle branch block (RBBB) can create challenges for electrophysiologists in estimating repolarization time and eliminating the effect of depolarization changes on QT interval. In this study, we aimed to develop a practice formula to eliminate the effect of depolarization changes on QT interval in patients with RBBB. METHODS: This prospective study evaluated accidentally induced RBBB in patients undergoing electrophysiological study. Two expert electrophysiologists recorded the ECG parameters, including QRS duration, QT interval, and cycle length, in the patients. The formula was developed based on QT interval differences (with and without RBBB) and its proportion to QRS. Additionally, the Bazzet, Rautaharju, and Hodge formulas were used to evaluate QTc. RESULTS: We evaluated 96 patients in this study. The mean QT interval without RBBB was 369.39 ± 37.38, reaching 404.22 ± 39.23 after inducing RBBB. ΔQT was calculated as 34.83 ± 17.61, and the ratio of ΔQT/QRS with RBBB was almost 23%. Our formula is: (QTwith RBBB  - 23% × QRS). Subtraction of 25% instead of 23% seems more straightforward and practical. Our formula could also predict the QTc interval in RBBB based on the Bazzet, Rautaharju, and Hodge formulas. CONCLUSION: Previous formulas for QT correction were hard to apply in the clinical setting or were not specified for RBBB. Our new formula allows a rapid and practical method for QT correction in RBBB in clinical practice.

Electrophysiological and therapeutic effects of amiodarone in patients with preexcited atrial fibrillation.

Background: Atrial fibrillation (AF) with fast ventricular response over an overt accessory pathway (AP) (preexcited AF) with a short anterograde refractory period is a potentially malignant arrhythmia. This study aimed to evaluate the safety and efficacy of amiodarone for preexcited AF management. Materials and Methods: This study enrolled 103 patients with evidence of AP in electrocardiography. Patients with preexcited AF were included in the study. Intravenous amiodarone (300 mg) was infused for 30 min for all patients in the AF rhythm. Electrophysiological parameters were evaluated before amiodarone injection and 2 h after pharmacological or electrical cardioversion. Results: Antegrade and retrograde refractory periods of the atrioventricular node (AVN) and AP, as well as antegrade and retrograde Wenckebach points of AVN, were increased significantly after amiodarone infusion. Furthermore, the mean of the shortest preexcited RR interval was increased during the monitoring period. Comparing the preexcited index at the beginning of the study and before cardioversion (2 h later) revealed that the QRS complexes changed to a wider pattern as the preexcitation index changed from 80.61 to 92.26 (P < 0.001). Nineteen (18.4%) patients converted to the sinus rhythm with amiodarone infusion. No ventricular arrhythmia was detected during monitoring. Conclusion: Amiodarone could be considered a safe drug in patients with preexcited AF for rate control despite its relatively low efficacy in conversion to the sinus rhythm.

Cryoballoon ablation results and complications in mid-term follow-up of patients with atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) is the most common cardiac arrhythmia, and its prevalence increases with advancing age. Pulmonary vein isolation is a standard approach in drug refractory paroxysmal AF which could be performed by cryoballoon ablation (CBA). We tried to evaluate its efficacy and safety in Iranian patients with AF. METHODS: From 2015 to 2017, 97 patients with paroxysmal and persistent AF were enrolled in our observational historical cohort study. They were visited 1 and 6 months post-procedure in order to assess the efficacy (recurrence) and safety. Recurrence was defined as 30 seconds of arrhythmia on their 48-hours Holter monitoring. RESULTS: Ninety-seven patients enrolled in the study, 64 (66.0%) of them were men, and their mean age was 55 ± 12 years. Hypertension was reported in 41 patients (42.3%), as the most common cardiac risk factor. 71 patients (73.2%) patients with paroxysmal AF and 15 patients (15.5%) with persistent AF underwent the procedure. After 6 months, recurrence was documented in only 17 patients (17.5%), and 82.5% of the patients were free from the recurrence. Post-procedural complication was detected only in 3 patients (3.1%). CONCLUSION: In our study, the mid-term success and safety of CBA in patients with paroxysmal AF was showed. CBA is a safe and effective method in paroxysmal AF, and even in some cases with persistent AF.

Assessment of QT and JT Intervals in Patients With Left Bundle Branch Block.

BACKGROUND: Prolongation of the QT interval is considered a risk factor for cardiac adverse events and mortality. Left bundle branch block (LBBB) lengthens the QT interval. The corrected QT interval (QTc) is most likely overestimated because its prolongation is caused by increases in depolarization duration and not in repolarization. OBJECTIVES: In this study, we aimed to apply corrected JT interval (JTc) as an appropriate measure of ventricular repolarization for predicting QTc in a formula. PATIENTS AND METHODS: The study population consisted of 101 patients with sinus rhythm (SR) and narrow QRS complexes (< 120 milliseconds). All patients underwent electrophysiology studies or ablation. A diagnostic catheter was positioned in the right ventricular apex (RVA) to induce LBBB at two different cycle lengths (CLs; 600 and 700 mv). The intrinsic QRS complex, QT time, and JT time were measured during SR and subsequent RVA pacing. The JTc was derived simply by subtracting the QRS duration from the QTc. RESULTS: Stimulation from the RVA increased the QTc from 456.20 ± 38.63 ms to 530.67 ± 47.73 ms at a CL of 600 (P < 0.0001) and to 502.32 ± 47.26 ms at 700 CL (P < 0.0001). JTc showed no significant changes with stimulation from the RVA (102.97 ± 11.35 ms vs. 103.59 ± 10.67 ms, P = 0.24). There was no significant correlation between JTc and QRS complex duration. A significant correlation was seen between QRS and QTc at both CLs. The ROC curve indicated that sensitivity of 80% and specificity of 67% were obtained with JTc duration of 92.6 ms. CONCLUSIONS: Right ventricular pacing increases the QT interval without increasing the JT interval. Our results confirm that JTc, as an index of repolarization, is independent of ventricular depolarization. Therefore, it can be applied for predicting QTc in patients with LBBB.

Complex genetic background in a large family with Brugada syndrome.

The Brugada syndrome (BrS) is an inherited arrhythmia characterized by ST-segment elevation in V1-V3 leads and negative T wave on standard ECG. BrS patients are at risk of sudden cardiac death (SCD) due to ventricular tachyarrhythmia. At least 17 genes have been proposed to be linked to BrS, although recent findings suggested a polygenic background. Mutations in SCN5A, the gene coding for the cardiac sodium channel Nav1.5, have been found in 15-30% of index cases. Here, we present the results of clinical, genetic, and expression studies of a large Iranian family with BrS carrying a novel genetic variant (p.P1506S) in SCN5A. By performing whole-cell patch-clamp experiments using HEK293 cells expressing wild-type (WT) or p.P1506S Nav1.5 channels, hyperpolarizing shift of the availability curve, depolarizing shift of the activation curve, and hastening of the fast inactivation process were observed. These mutant-induced alterations lead to a loss of function of Nav1.5 and thus suggest that the p.P1506S variant is pathogenic. In addition, cascade familial screening found a family member with BrS who did not carry the p.P1506S mutation. Additional next generation sequencing analyses revealed the p.R25W mutation in KCNH2 gene in SCN5A-negative BrS patients. These findings illustrate the complex genetic background of BrS found in this family and the possible pathogenic role of a new SCN5A genetic variant.

Predicting the outcome in patients with unexplained syncope and suspected cardiac cause: role of electrophysiologic studies.

OBJECTIVE: Unexplained syncope is a challenge facing electrophysiologists. The prognosis varies widely depending on underlying causes, specially, cardiac ones. We sought to determine the abnormal electrophysiolgic (EP) study results as predictors of prognosis in syncope patients with suspected cardiac cause and risk factors associated with mortality. METHODS: A total of 227 consecutive patients with unexplained syncope were prospectively enrolled in this study. EP study was performed in 177 patients in base of inclusion criteria. These patients, in whom a cardiac cause of syncope was suspected, underwent EP study and if negative, head-up tilts test (HUTT). Complete follow-up was obtained for 132 patients for 20.0±10.8 months. RESULTS: A cardiac cause of syncope was established in 35%, a neurally mediated syncope in 35.6%, and in the rest 29.4% the cause of syncope remained unexplained despite a throughout neurologic and cardiologic evaluation. Logistic analysis revealed that the significant predictors of a cardiac cause of syncope were the absence of prodromal symptoms, left bundle branch block (LBBB), sever left ventricle (LV) dysfunction and male gender. At logistic analysis, the presence of LBBB (OR=6.63; 95% CI: 1.09-40) was significantly associated with outcome of death. CONCLUSION: The present study provides evidence that presence of LBBB, abnormal EP study result and structural heart disease (SHD) have prognostic value in patients with suspected cardiac cause of syncope. The patients with SHD and unexplained syncope who had a negative EP study have a good long-term prognosis even in the presence of LV dysfunction.

Role of electrophysiological study in patients with syncope and bundle branch block.

BACKGROUND: The finding of bundle branch block (BBB) in patients with syncope suggests that paroxysmal atrioventricular block (AVB) or ventricular tachyarrhythmia (VT) may be the cause of syncope. Guidelines for cardiac pacing and cardiac resynchronization therapy have been recommended to perform electrophysiological study (EPS) for confirming main cause of syncope. Therefore, the aim of our study was to evaluate the role of EPS in patients with syncope and BBB. MATERIALS AND METHODS: We evaluated 133 patients (mean age 63 ± 13.8 years) with past history of syncope and BBB from April 2002 to December 2010 who referred to Arrhythmia clinic in two tertiary care centers. All patients underwent EPS on admission time. The frequency distributions of AVB and VT in patients were determined. RESULTS: Left bundle branch block was diagnosed in 184 (82.1%) patients. 133 of them had preserved left ventricular ejection fraction (LVEF ≥45%) that in 91 (68.4%) of those, EPS finding was normal. In 41 (30.8%) patients AVB was reported. In 2 (1.5%) patients VT and atrioventricular nodal reentrant tachycardia were seen. Coronary artery disease was more common in patients with AVB and abnormal EPS finding (P = 0.02). CONCLUSION: Ventricular tachyarrhythmia was a rare electrophysiological finding in those with syncope, bifascicular block, and preserved LVEF. Considering cost-effect benefit, pacemaker or implantable loop recorder implantation is suggested; however, EPS may not be necessary to perform before permanent pacemaker implantation.

Electrocardiographic (ECG) clues to differentiate idiopathic right ventricular outflow tract tachycardia (RVOTT) from arrhythmogenic right ventricular cardiomyopathy (ARVC).

INTRODUCTION: Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a genetic cardiomyopathy that most commonly affects young adults. The most commonly observed reason of death in patients suffering from ARVC/D is sudden cardiac death (SCD). On the other hand, idiopathic right ventricular outflow tract tachycardia (RVOT VT) usually has a benign course. Both of the entities may have ventricular tachycardia (VT) with left bundle branch block (LBBB) pattern and inferior axis. We tried to propose new discriminating electrocardiographic indices for differentiation of foretold entities. MATERIAL AND METHOD: This was a retrospective study. We reviewed records of patients admitted between 2003 and 2012 with the diagnosis of either ARVC/D or RVOT VT that presented with VT (LBBB morphology). RESULT: A total of fifty nine patients (30 RVOT VT and 29 ARVC/D) were enrolled. In ARVC/D group, men were dominant while the reverse was true of RVOT VT. Palpitation was more common in the RVOT VT group (90% vs. 66.7%), but aborted SCD and sustained VT were more common in ARVC/D group. The new ECG criteria proposed by us mean QRS duration in V1-V3, QRS difference in right and left precordial leads, S wave upstroke duration, JT interval dispersion, QRS and JT interval of right to left precordial leads were all significantly longer in ARVC/D when compared to RVOT VT patients (p < 0.001). CONCLUSION: The proposed ECG criteria can be used for non-invasive diagnosis of ARVC/D and incorporation in the future updates of ARVC/D task force criteria.

Prediction of midterm performance of active-fixation leads using current of injury.

BACKGROUND: There are only limited prospective data on the clinical relevance of current of injury (COI) as a predictor of the midterm performance of active-fixation leads. This study sought to investigate whether it is possible to predict the midterm performance of active-fixation leads using COI recorded at the time of implantation. METHODS AND RESULTS: One hundred fifty patients (78 men; mean age, 63 ± 19 years) who received active-fixation pacing (n = 201) and defibrillator (n = 51) leads were studied. COI was measured from the intracardiac bipolar electrogram recorded at the time of lead implantation. The study outcome was good lead performance at 6 months, defined as P wave ≥ 1.5 mV, threshold <1.5 V for atrial lead, R-wave ≥ 5 mV, and threshold <1 V for ventricular lead. A total of 102 active-fixation atrial and 150 ventricular leads were implanted. During a 6-month follow-up, invasive intervention was required for seven atrial and seven ventricular leads. In multivariate analysis, COI was the only independent predictor of good outcome for the active-fixation atrial (odds ratio [OR]: 5.67, 95% confidence interval [CI]: 2.18-14.76, P = 0.001) and ventricular leads (OR: 3.99, 95% CI: 1.08-21.26, P = 0.002). Receiver-operating characteristic analysis identified ST-segment elevation ≥2.0 mV for the atrial leads (sensitivity, 75%; specificity, 89%) and ≥10.0 mV for the ventricular leads (sensitivity, 70%; specificity, 87%) as optimal cutoffs for good midterm performance. CONCLUSIONS: Midterm performance of active-fixation leads is predictable using COI recorded at the time of lead implantation. A ST-segment elevation ≥2.0 mV in the atrial leads and ≥10.0 mV in the ventricular leads are recommended to improve the lead performance at 6 months.

Ventricular tachyarrhythmia after coronary bypass surgery: incidence and outcome.

BACKGROUND: Ventricular tachyarrhythmia after coronary artery bypass graft is common and the occurrence has been described, but the incidence and risk factors are not well defined. AIM: To evaluate the incidence of arrhythmias and to detect high-risk populations. METHODS: In this prospective study, 856 consecutive patients undergoing coronary artery bypass graft were monitored for new-onset ventricular tachyarrhythmias: non-sustained monomorphic ventricular tachyarrhythmia, sustained monomorphic ventricular tachyarrhythmia, sustained polymorphic ventricular tachyarrhythmia, and ventricular fibrillation. Detailed analyses of the clinical, demographic, echocardiographic, and surgical findings and arrhythmias occurrence was carried out during 6 months of follow-up. RESULTS: The incidence of ventricular tachyarrhythmia was 26.6% (17.6% non-sustained monomorphic ventricular tachycardia, 5.5% sustained monomorphic ventricular tachycardia, 0.8% sustained polymorphic ventricular tachycardia, and 2.7% ventricular fibrillation). The strongest degrees of statistical significance were for low ejection fraction (p = 0.01) and ischemic heart disease (p = 0.02). The incidence of ventricular fibrillation (61%) was greatest in the first 48 h after surgery. Postoperative myocardial infarction (p = 0.03) and hemodynamic instability (p = 0.05) were also predictors of arrhythmia occurrence. Recurrence of arrhythmia was highest in the ventricular fibrillation group (52%). The correlations between tachyarrhythmia, age, sex, electrolyte disorders, body mass index, and systemic or pulmonary hypertension were not significant. CONCLUSION: In view of the strong relationship between ventricular arrhythmias and low ejection fraction, ischemic heart disease, coronary artery disease severity, postoperative myocardial infection, and hemodynamic impairment, continuous monitoring is necessary, especially in the first 48 h after coronary artery bypass surgery.

The effect of left ventricular (LV) remodeling on ventricular arrhythmia in cardiac resynchronization therapy (CRT-D) patients (antiarrhythmic effect of CRT).

BACKGROUND: In patients with low ejection fraction and ventricular dyssynchrony, cardiac resynchronization therapy (CRT) is an accepted therapeutic modality. In these patients, CRT can improve the quality of life and exercise tolerance in addition to improved survival. On the other hand, antiarrhythmic effects of CRT is a place of debate. METHOD: In this study, we evaluated the effect of CRT-induced reverse remodeling on ventricular arrhythmia in heart failure patients. Patients with CRT were divided to two groups of responders and nonresponders. Responders were those with reduction of LVESD of more than 10% or increase in LVEF of more than 5%. They were visited and device analysis was performed during the follow-up. RESULTS: One hundred and nineteen patients were enrolled in this study. Those with reverse remodeling experienced fewer ventricular arrhythmias after two years of follow-up (N = 2 vs 11, P = 0.001). CONCLUSION: Reverse remodeling associated with CRT implantation can result in decreased frequency of ventricular arrhythmias.

Predictors of local venous complications resulting from electrophysiological procedures.

BACKGROUND: Thromboembolic complications resulting from radiofrequency catheter ablation (RFCA) have an overall incidence of 0.6%. Multiple intracardiac catheters are often necessary for electrophysiological study and RFCA therapy. Therefore, the placement of multiple venous sheaths in one femoral vein is always required for multiple intracardiac catheter insertion. The safety of the placement of multiple separate venous sheaths has been studied previously in a non-randomized study, but the placement of multiple sheaths via one venous line has not been fully studied. METHODS AND RESULTS: A randomized clinical trial was conducted with a total of 200 patients. We studied the safety of placing multiple sheaths via one venous line, and the effect of heparin on deep vein thrombosis (DVT) and on in situ thrombosis. DVT was not seen in our patients. We observed a significant decrease in the rate of in situ thrombosis in patients who received heparin during the procedure (28% vs 11%, p = 0.04). The type of cannulation changed the in situ thrombosis rate independently of the heparinization protocol. The rate of in situ thrombosis was higher when placing sheaths via one venous line regardless of the heparinization protocol used (16% vs 6%, p = 0.1 for the group on heparin, and 38% vs 18%, p = 0.04 for the other group). In the group cannulated with only one venous line (100 patients), heparinization significantly decreased the rate of in situ thrombosis (16% vs 38%, p = 0.023), but there was an insignificant decrease in the separate cannulation group (6% vs 18%, p = 0.12). Advanced age had no effect on thrombosis. Surprisingly, there was a significantly greater rate of in situ thrombosis (not DVT) among women than among men (26% vs 11%, p = 0.01), regardless of the heparinization protocolor the type of cannulation. CONCLUSIONS: Given the local venous complications and DVT after electrophysiological procedures, heparinization is not necessary for right-sided electrophysiological procedures. In situ thrombosis is a minor complication that can be reduced by heparinization in patients undergoing one-line cannulation and in women during longer procedures.

Evaluation of the patients with syncope during the first month after coronary artery bypass graft.

BACKGROUND: Syncope is a well-known risk factor for adverse cardiovascular event in patients with coronary artery disease, especially those with previous myocardial infarction (MI) or left ventricular dysfunction. The aim of this study was to assess electrophysiologic findings and results of head-up tilt test (HUTT) in patients with syncope and without orthostatic changes in blood pressure during the first month after coronary artery bypass graft (CABG). MATERIALS AND METHODS: A total of 20 patients with syncope during the first month after CABG were prospectively enrolled in this study from June 2002 to April 2006. Electrophysiologic study (EPS) was performed in all of them. HUTT was performed in all of the patients regardless of the result of EPS. RESULTS: The mean age of patients was 60.3±11 years. Twelve patients were males. EPS was negative in 18 patients. HUTT was positive in 10 patients. Six patients had old MI. Ischemic insult occurred in one patient after CABG. Left bundle branch was present in two patients. There was a significant relationship between the duration of bed rest after CABG and positive HUTT (P value = 0.021). All of the patients except one did not experience syncope during the follow-up period. CONCLUSION: In patients with syncope during the first month post CABG, in whom an arrhythmic cause is suspected, the other cause of syncope like orthostatic intolerance should be considered. Being bedridden for an extended period of time post CABG can be a predisposing factor.

Induction and aggravation of atrioventricular valve regurgitation in the course of chronic right ventricular apical pacing.

AIMS: Valvular regurgitation, especially on the right side of the heart, is a common finding even in patients without endocardial pacing leads. The severity of valvular regurgitation can change after permanent pacemaker (PPM) implantation. Ventricular pacing has been shown to cause ventricular dysfunction. The purpose of this study was to evaluate the mid-term effects of right ventricular (RV) apical pacing on atrioventricular (AV) valvular regurgitation in patients with a normal left ventricular function before PPM implantation. METHODS AND RESULTS: Patients who required dual-chamber pacemakers due to a high-degree AV block were enrolled in the study. Initial echocardiography was performed before PPM implantation and re-evaluation by echocardiography was performed every 24 months thereafter. A total of 125 patients (61 male; mean age: 66.57 ± 6.45 years) were included in the study, and 115 pacemaker-dependent patients were followed up (mean ± SD; 4.08 ± 0.8 years). Echocardiography demonstrated mild tricuspid regurgitation (TR) and mitral regurgitation (MR) in 70 (60.1%) and 34 (29.6%) patients before PPM implantation, respectively. Moderate TR and MR were detected in 10 (8.7%) and 1 (0.9%) patients, respectively. Thirty-six (31.6%) patients showed moderate-to-severe TR at long-term follow-up, compared with the 10 (8.7%) patients, who had the same degree of TR before RV apical pacing (P < 0.001). Mild and moderate MR were detected in 54 (47%) and 8 (7%) patients after PPM implantation on the last echocardiography(P < 0.001). Baseline systolic pulmonary artery pressure (PAP) was 29.24 ± 8.45 mmHg, which increased to 36 ± 11 mmHg on the last echocardiography (P < 0.001). CONCLUSION: Considering the haemodynamic effects at mid-term follow-up, left ventricular dysfunction is rare in patients with RV apical pacing and normal baseline left ventricular function. Right ventricular apical pacing is associated with a significant increase in the prevalence and severity of TR and MR.

Successful Implantation of Transvenous Pacing System via Persistent Left Superior Vena Cava and Coronary Sinus in Small Children.

Transvenous pacemaker implantation tends to be difficult in the setting of a persistent left superior vena cava (SVC) and an absent or inaccessible right SVC. We report two small children in whom transvenous pacing leads were successfully inserted via a persistent left SVC. This technique was safe in our cases; however, favorable long-term result has yet to be demonstrated.

Electrical storm in Brugada syndrome during pregnancy.

Clinical and molecular characterization of the Brugada syndrome has progressed rapidly since its initial description. The role of hormonal changes during pregnancy and postpartum period on the pathogenesis of Brugada syndrome has not been studied. Herein, we describe a case of revelation of Brugada syndrome during pregnancy in a young woman who presented with electrical storm as the first manifestation. Low-dose isoproterenol infusion followed by oral quinidine inhibited the recurrence of ventricular tachyarrhythmia and normalized the electrocardiographic pattern. We emphasize the importance of hormonal changes during pregnancy as a precipitating factor for arrhythmic events in Brugada syndrome.

Signal-averaged electrocardiography in patients with advanced heart failure: a better indicator of left ventricular enlargement compared with conventional electrocardiography.

BACKGROUND: The signal-averaged electrocardiography is a noninvasive method to evaluate the presence of the potentials generated by tissues activated later than their usual timing in the cardiac cycle. The purpose of this study was to demonstrate the correlation between the filtered QRS duration obtained via the signal-averaged electrocardiography and left ventricular dimensions and volumes and then to compare it with the standard electrocardiography. METHODS: We included patients with advanced systolic left ventricular dysfunction (ejection fraction ≤ 35%). All the patients underwent surface twelve-lead electrocardiography, signal-averaged electrocardiography, and echocardiography. RESULTS: The study included 86 patients with a mean age of 54.66 ± 13.23 years. The mean left ventricular ejection fraction was 18.31 ± 5.49%; the mean QRS duration was 0.14 ± 0.02 sec; and 52% of the patients had left bundle branch block. The mean filtered QRS duration was 145.87 ± 24.89 ms. Our data showed a significant linear relation between the filtered QRS duration and left ventricular end-systolic volume, left ventricular end-diastolic volume, left ventricular end-systolic diameter, and left ventricular end-diastolic diameter; the correlation coefficient was, however, not good. There was no significant correlation between the QRS duration and left ventricular diameters and volumes. CONCLUSION: The filtered QRS duration has a better correlation with left ventricular dimensions and volumes than does the QRS duration in the standard electrocardiography.

Significance of signal averaged electrocardiography in patients with advanced heart failure and intraventricular conduction delay.

AIMS: Signal averaged electrocardiography is a noninvasive method to evaluate the presence of the potentials that are generated by tissues, activated later than their usual timing in the cardiac cycle. The purpose of this study was to demonstrate the correlation of data obtained via signal averaged electrocardiography and left ventricular dyssynchrony. METHODS: We included the patients with advanced systolic left ventricular dysfunction (ejection fraction