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.

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.

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.

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.

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.

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.

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.

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.

Free floating right atrial thrombus in two asymptomatic patients after electrophysiological study: role of routine echocardiography after ablation.

This report presents two patients with free floating right atrial and atrioventricular thrombi after electrophysiology study which were treated with thrombolysis in the first patient and surgical operation in the second patient without any complication.

Delayed cardiac perforation by one small body diameter defibrillator lead.

We report a 37-year-old man who presented with continuous chest pain 6 weeks after implantable cardioverter-defibrillator implantation. Implantable cardioverter-defibrillator interrogation indicated complete loss of capture even with maximum output. Chest radiography and echocardiography confirmed extracardiac location of lead tip. After lead repositioning in electrophysiology laboratory, acceptable pacing threshold was obtained with no complication. This report demonstrates a case of delayed cardiac perforation after implantation of the St Jude Medical Durata implantable cardioverter-defibrillator lead.

Presence of macrovolt T wave alternans and short coupled PVC simultaneously in a patient with long QT syndrome.

This report presents a patient with macrovolt T wave alternans, PVC with R on T or a long-short sequence followed by torsades de pointes.

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

Prediction of response to cardiac resynchronization therapy using simple electrocardiographic and echocardiographic tools.

AIMS: To predict response to cardiac resynchronization therapy (CRT) in patients with heart failure (HF) and intraventricular conduction delay. METHODS AND RESULTS: The study population consisted of 82 consecutive HF patients with standard CRT indications. Patients were classified as responders, if they were alive without cardiac decompensation and experienced >or=15% decrease in left ventricular end-systolic volume. Sixty-eight percent of the enrolled patients responded to CRT. When compared with non-responders, responders had a wider baseline QRS width (P = 0.001), more marked QRS shortening (DeltaQRS) immediately after CRT (P = 0.001), and a better improvement in aortic velocity time integral (VTI) 24 h after CRT (P = 0.02). Moreover, there was a trend towards a greater baseline intraventricular dyssynchrony in the responder group (P = 0.07). By multivariable logistic regression, the baseline QRS width (OR: 0.95, 95% CI: 0.90-0.97, P = 0.001), DeltaQRS (OR: 1.038, 95% CI: 1.012-1.064, P = 0.003), and acute aortic VTI (OR: 0.81, 95% CI: 0.68-0.96, P = 0.017) emerged as independent predictors of response to CRT. Receiver operating characteristic curve analysis identified a QRS width >145 ms, DeltaQRS >20 ms, and aortic VTI >14 cm to predict responders. CONCLUSION: A positive response to CRT was observed in 68% of the patients. Cardiac resynchronization therapy response is predictable using simple electrocardiographic and echocardiographic data.

ST-segment depression as a risk factor in hypertrophic cardiomyopathy.

AIMS: From the spectrum of electrocardiogram (ECG) changes that may occur in hypertrophic cardiomyopathy (HCM), there is no criterion reported to be useful for risk stratification. We sought to determine whether there was a relationship between the resting ECG findings and prognosis in patients with HCM. METHODS AND RESULTS: We retrospectively analysed data on 173 consecutive patients admitted to our centre with a diagnosis of HCM. The 12-lead ECGs were assessed for underlying rhythm, PR interval, QRS voltages, QRS width, corrected QT interval, ST-segment deviation, T-wave inversion, and left atrial enlargement (LAE). During a mean follow-up of 50 months, 6.4% of patients had a combined endpoint [sudden death or appropriate implantable cardioverter-defibrillator (ICD) therapy]. The frequency of the combined endpoint was greater in patients with syncope, non-sustained ventricular tachycardia, maximal left ventricular (LV) wall thickness >or=30 mm, and ST-segment depression in the high lateral leads (all P < 0.05). Other ECG findings (LV hypertrophy, LAE, abnormal Q wave, abnormal ST-T changes, and underlying rhythm), family history of sudden death, and LV outflow obstruction were not related to the combined endpoint. The results of our multivariate analysis demonstrated that ST-segment depression in the high lateral leads (OR: 20.0, 95% CI: 12.7-27.5; P = 0.0001) and syncope (OR: 19.0, 95% CI: 11.7-26.9; P = 0.0001) were the predictors of sudden death or appropriate ICD therapy in patients with HCM. CONCLUSION: The results of this study indicated that, in addition to generally accepted risk factors, ST-segment depression in the high lateral leads could be of prognostic significance in HCM patients.

Effect of right ventricular lead location on response to cardiac resynchronization therapy in patients with end-stage heart failure.

AIMS: It is currently recommended to implant the left ventricular (LV) pacing lead at the lateral wall. However, the optimal right ventricular (RV) pacing lead location for cardiac resynchronization therapy (CRT) remains controversial. We sought to investigate whether optimizing the site for placement of the RV lead could further improve the long-term response to CRT in patients with advanced heart failure. METHODS AND RESULTS: Between October 2006 and December 2007, a total of 73 consecutive patients with standard indication for CRT were enrolled. The enrolled patients were divided into two groups based on the RV lead location. There were 50 patients in RV apex (RVA) group and 23 patients in RV high septum (RVHS). The primary study endpoint was a decrease in LV end-systolic volume (LVESV) by >15% at 6-month follow-up. The secondary endpoints were improvement in New York Heart Association (NYHA) class by >or=1 point and decrease in brain-type natriuretic peptide (BNP) levels by >50% after CRT. At 6-month follow-up, improvement in NYHA class by >or=1 point (RVA: 72% vs. RVHS: 74%, P = 0.76), decrease in LVESV by >or=15% (RVA: 65% vs. RVHS: 64%, P = 0.76), and decrease in BNP level by >50% (RVA: 70% vs. RVHS: 69%, P = 0.88) were observed in similar proportion of the two groups. When we separately assessed the significance of RV pacing site in three LV stimulation sites, there were no significant differences in terms of clinical improvement (62 vs. 64%, P = 0.74) and decrease in LVESV by >15% (63 vs. 62%, P = 0.78) between RVA and RVHS pacing when the LV stimulation site was lateral cardiac vein. In anterolateral vein pacing site, the RVA stimulation was associated with higher clinical (88 vs. 47%, P = 0.05), echocardiographic (75 vs. 32%, P = 0.02), and neurohormonal responses (80 vs. 50%, P = 0.04) compared with that in RVHS site. When LV was paced from posterolateral vein, RVHS pacing was superior to RVA in terms of the clinical improvement (85 vs. 35%, P = 0.01), echocardiographic response (72 vs. 30%, P = 0.01), and decrease in BNP levels (75 vs. 50%, P = 0.04). CONCLUSION: The present study did not show any difference between RVA and RVHS pacing sites in terms of overall improvement in clinical outcome and LV reverse remodelling following CRT. However, effect of RV lead location on CRT response varies depending on LV stimulation site.

Predictors of syncope in patients with hypertrophic cardiomyopathy.

BACKGROUND: Approximately 30% of patients with hypertrophic cardiomyopathy (HCM) suffer syncope and syncope was the only symptom associated with sudden death. However, no systematic studies in large cohorts looking at predictors of syncope are available in the literature. Therefore, we sought to determine predictors of syncope in patients with HCM. METHODS: One hundred and seventy-three consecutive patients with HCM and a mean age of 42 +/- 18 years (range 10-78) underwent extensive clinical, electrocardiographic, and echocardiographic testing to identify predictors of syncope. RESULTS: During the mean follow-up duration of 50 months, syncope occurred in 28% of the HCM patients. Univariate analysis showed male gender, age <40 years, family history of sudden death, PR interval, QRS width, >or=2 bursts of nonsustained ventricular tachycardia (NSVT), >or=3 bursts of nonsustained supraventricular tachycardia (NSSVT), maximum left ventricular wall thickness >or=30 mm, and abnormal blood pressure response, out of 24 demographic, clinical, hemodynamic, electrocardiographic, and echocardiographic features, to be significantly associated with syncope. Of these nine variables, the only independent predictors of syncope at multivariate analysis were age <40 years (odds ratio [OR]: 4.4, 95% confidence interval [CI]: 2.2-16, P = 0.003), >or=2 bursts of NSVT (OR: 9.9, 95% CI: 2.0-46, P = 0.0001), and >or=3 bursts of NSSVT (OR: 2.7, 95% CI: 0.38-8.25, P = 0.001). The concomitant occurrence of all three variables had a sensitivity of 87% and specificity of 73% in identifying the patients with syncopal events. CONCLUSIONS: The results of this study showed that age <40 years, bursts of NSVT, and NSSVT were independently associated with the risk of syncope in patients with HCM. Demographic data and ambulatory ECG findings could help in risk stratification of patients with HCM.

Inappropriate Shock delivered by Implantable Cardioverter Defibrillator--Cardiac Resynchronization Therapy (ICD-CRT) due to myopotential oversensing.

The clinical efficacy of ICD-CRT therapy depends on accurate sensing of intracardiac signals and sensing algorithms. We report the occurrence of sensing abnormality in a patient with ICD-CRT. In this patient, oversensing of myopotentials during strenuous muscular activity resulted in an inappropriate ICD-CRT discharge. Although modern ICDs are highly effective in detecting and terminating malignant tachyarrhythmias, their detection specificity must be improved. It is possible to find the mechanism of arrhythmia by EGM. Simple device reprogramming make it possible to avoid the oversensing of myopotentials.

Can successful radiofrequency ablation of atrioventricular nodal reentrant tachycardia be predicted by pattern of junctional ectopy?

BACKGROUND: Emergence of junctional rhythm (JR) during radiofrequency (RF) current delivery directed at the periatrioventricular nodal region has been shown to be a marker of success in atrioventricular nodal reentrant tachycardia (AVNRT). Whereas the characteristics of JR during RF ablation of slow pathway have already been studied, the electrophysiologic features of different patterns of JR are yet to be evaluated. The aim of this study was to investigate in detail the characteristics of the JR that develops during the RF ablation of the slow pathway. MATERIALS AND RESULTS: The study population consisted of 95 patients: 56 women and 33 men (mean age, 47.2 +/- 16.3 years) who underwent slow pathway ablation because of AVNRT. A combined anatomical and electrogram mapping approach was used, and AVNRT was successfully eliminated in all patients. This study identified 7 patterns for JR during the RF ablation of slow pathway: junction-junction-junction, sinus-junction-sinus, intermittent burst, sparse, no junction, sinus-junction-junction, and sinus-junction-block . The characteristics of JR, such as mean cycle length and total number, were gathered. The incidence of JR was significantly higher during effective applications of RF energy than during ineffective applications (P = .001). The mean number of junctional ectopy was 19.6 +/- 19. The total number of junctional ectopy was significantly higher during effective applications of RF energy than during ineffective applications (24.6 +/- 18.8 vs 8.4 +/- 13.2; P < .001). We found a significant difference between the effective and ineffective applications of RF energy in the mean cycle length of the junctional ectopy (464.6 +/- 167.5 vs 263.4 +/- 250.2; P < .01). The patterns of JR were compared between effective and ineffective applications. We managed to show a significant correlation between patterns of JR and successful ablation (P = .01). Logistic regression analysis revealed that the presence of sinus-junction-sinus, sinus-junction-junction, and sinus-junction-block patterns of JR was a predictor of a successful RF ablation (confidence interval [CI], 1.67-15.92 [P < .004]; CI, 1.02-85.62 [P = .048]; and CI, 1.06-32.02 [P = .042], respectively). CONCLUSION: This study confirms that JR is often present during successful slow pathway ablation. The pattern of JR is useful as indicator of success.

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.