Major Arrhythmic Events In Patients Research Articles

Prediction of Major Arrhythmic Outcomes in Ischemic Cardiomyopathy: Value of Hibernating Myocardium in PET/CT.

Known predictors of major arrhythmic events (MAE) in patients with ischemic cardiomyopathy (ICM) include previous MAE and left ventricular ejection fraction (LVEF) ≤35%. Myocardial scars detected by perfusion imaging in ICM have been linked to MAE, but the prognostic significance of hibernating myocardium (HM) is unclear. The objective was to predict major arrhythmic events (MAE) from combined 13N-ammonia (NH3) and 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in ischemic cardiomyopathy (ICM). Consecutive patients with ICM undergoing combined NH3- and FDG-PET/CT were included. HM was quantified in relation to total left ventricular myocardium (i.e. ≥7% is large). The primary outcome was MAE (sudden cardiac death, ICD therapy, sustained ventricular tachycardia/fibrillation).Among 254 patients, median baseline LVEF was 35% (IQR 28-45) and 10% had an ICD. PET/CT identified ischemia in 94 (37%), scar in 229 (90%) and HM in 195 (77%) patients. Over a median follow-up of 5.4 (IQR 2.2-9.5) years, MAE occurred in 34 patients (13%). Large HM was associated with a lower incidence of MAE (HR 0.31, 95% CI 0.1-0.8, p=0.001). After multivariate adjustment for history of MAE, LVEF ≤35% and scar ≥10%, large HM remained significantly associated with a lower incidence of MAE (p=0.016). LVEF improved over time among patients with large HM (p=0.006) but did not change in those without (p=0.610) or small HM (p=0.240). HM conveys a lower risk of MAE in patients with ICM. This may be explained by an increase in LVEF when a large extent of HM is present.

Fragmented QRS, a strong predictor of mortality and major arrhythmic events in patients with nonischemic cardiomyopathy: A systematic review and meta-analysis.

Fragmented QRS (fQRS), which is associated with rhythm disturbances, can predispose the heart to fatal ventricular arrhythmias. Recently, accumulating studies indicates that fQRS is associated with poor prognosis in various types of cardiomyopathies. Therefore, we assessed the association between fQRS with all-cause mortality and major arrhythmic events (MAEs) in patients with nonischemic cardiomyopathy, in this systematic review and meta-analysis study. We performed a comprehensive search in databases of PubMed/Medline, EMBASE, and Web of Science from the beginning to December 31, 2022. Published observational studies (cohorts, case-control, or analytical cross-sectional studies) were included that report the prognostic value of fQRS in patients with different types of nonischemic cardiomyopathies for MAEs (sudden cardiac death, sudden cardiac arrest, sustained ventricular tachycardia [VT], ventricular fibrillation [VF], and appropriate shock) and all-cause mortality. We pooled risk ratios (RRs) through raw data and adjusted hazard ratios (aHRs) using "Comprehensive Meta-Analysis" software, Version 2.0. Nineteen cohort and three analytical cross-sectional studies were included in this meta-analysis involving a total of 4318 subjects with nonischemic cardiomyopathy (1279 with fQRS and 3039 without fQRS). FQRS was significantly associated with an increased risk of all-cause mortality in patients with nonischemic cardiomyopathy (pooled RR: 1.920; 95% confidence interval [CI]: 1.388-2.656, p < 0.0001/pooled HR: 1.729; 95% CI: 1.327-2.251, p < 0.0001). Also, the risk of developing MAEs in the presence of fQRS was significantly increased (pooled RR: 2.041; 95% CI: 1.644-2.533, p < 0.0001/pooled HR: 3.626; 95% CI: 2.119-6.204, p < 0.0001). In the subgroup analysis, the strongest association between fQRS presence and increased MAEs was observed in patients with hypertrophic cardiomyopathy (HCM) (pooled RR: 3.44; 95% CI: 2.07-5.71, p < 0.0001/pooled HR: 3.21; 95% CI: 2.04-5.06, p < 0.0001). Fragmented QRS could be a prognostic marker for all-cause mortality and MAEs in patients with various types of nonischemic cardiomyopathies, particularly HCM.

MRI Assessment of Myocardial Deformation for Risk Stratification of Major Arrhythmic Events in Patients With Non-Ischemic Cardiomyopathy Eligible for Primary Prevention Implantable Cardioverter Defibrillators.

Implantable cardioverter-defibrillator (ICD) intervention is an established prophylactic measure. Identifying high-benefit patients poses challenges. To assess the prognostic value of cardiac magnetic resonance imaging (MRI) parameters including myocardial deformation for risk stratification of ICD intervention in non-ischemic cardiomyopathy (NICM) while accounting for competing mortality risk. Retrospective and prospective. One hundred and fifty-nine NICM patients eligible for primary ICD (117 male, 54 ± 13 years) and 49 control subjects (38 male, 53 ± 5 years). Balanced steady state free precession (bSSFP) and three-dimensional phase-sensitive inversion-recovery late gadolinium enhancement (LGE) sequences at 1.5 T or 3 T. Patients underwent MRI before ICD implantation and were followed up. Functional parameters, left ventricular global radial, circumferential and longitudinal strain, right ventricular free wall longitudinal strain (RV FWLS) and left atrial strain were measured (Circle, cvi42). LGE presence was assessed visually. The primary endpoint was appropriate ICD intervention. Models were developed to determine outcome, with and without accounting for competing risk (non-sudden cardiac death), and compared to a baseline model including LGE and clinical features. Wilcoxon non-parametric test, Cox's proportional hazards regression, Fine-Gray competing risk model, and cumulative incidence functions. Harrell's c statistic was used for model selection. A P value <0.05 was considered statistically significant. Follow-up duration was 1176 ± 960 days (median: 896). Twenty-six patients (16%) met the primary endpoint. RV FWLS demonstrated a significant difference between patients with and without events (-12.5% ± 5 vs. -16.4% ± 5.5). Univariable analyses showed LGE and RV FWLS were significantly associated with outcome (LGE: hazard ratio [HR] = 3.69, 95% CI = 1.28-10.62; RV FWLS: HR = 2.04, 95% CI = 1.30-3.22). RV FWLS significantly improved the prognostic value of baseline model and remained significant in multivariable analysis, accounting for competing risk (HR = 1.73, 95% CI = 1.12-2.66). In NICM, RV FWLS may provide additional predictive value for predicting appropriate ICD intervention. 2 TECHNICAL EFFICACY: Stage 5.

Relation between non-sustained ventricular tachycardia and major arrhythmic events in patients with dilated cardiomyopathy caused by titin truncating variants

Abstract Background Truncating titin variants (TTNtv) are the most frequent monogenetic cause of dilated cardiomyopathy (DCM). Current data suggest that nonsustained ventricular arrhythmia is common in patients with TTVtv but its relation to the risk of major arrhythmic events (MAE) is uncertain. Purpose To investigated the relationship between NSVT recorded on Holter ECG or implanted device and MAE in patients with DCM. Methods We retrospectively studied consecutively evaluated patients with DCM (left ventricle ejection fraction (LVEF) below 50%) on echocardiography and a pathogenic TTNtv. Patients with obstructive coronary artery disease, valvular disease, ventricular tachycardia ablation during follow-up time and follow-up less than one month were excluded. Survival was modelled from the initial Holter or device implantation. NSVT was defined as ≥3 consecutive ventricular beats at a rate &amp;gt;120 beats per minute, lasting for &amp;lt;30 s. MAE was defined as sustained ventricular tachycardia (VT), ventricular fibrillation (VF), sudden cardiac death, implantable cardioverter defibrillator (ICD) treated ventricular arrhythmias (appropriate shock and ATP). The clinical endpoint was MAE (sustained VT, VF, sudden cardiac death, ICD shocks and ATP) and multivariable analysis was performed using Cox proportional hazards models. Event-free survival probabilities were estimated using the Kaplan-Meier method, and comparisons of Kaplan-Meier curves were made using log-rank tests. Results The cohort comprised 58 men and 30 women [mean age 49 ± 15 years; mean follow-up 3.5 ± 1.8 years]. Symptoms were NYHA class I in 56 patients, class II in 25 patients, class III in 7 patients and class IV in none. Holter ECGs were performed in 77 patients, 41 of whom had NSVT. Twenty five patients had pacemaker/ICD in situ; 14 had NSVT. Six patients had MAE; 4 with NSVT. Univariate analysis association between MAE and LVEF ≤35% (hazard ratio (HR), 9.03; 95% confidence interval (CI), 1.49-54.71; P=0.017), prolonged (&amp;gt;8 beats) NSVT (HR, 6.71; 95% CI, 1.22-36.98; P=0.029) and fast (&amp;gt;200 bpm) NSVT (HR, 5.09; 95% CI, 1.02-25.47; P=0.048). Kaplan-Meier showed similar differences in freedom from MAE (LVEF ≤35%; P=0.004, long NSVT; P=0.025, fast NSVT; P=0.031). Conclusion Fast and prolonged NSVT is associated with a higher risk of MAE in patients with TTNtv.Characteristics at the beginningSurvival probability for freedom

Machine learning analysis of complex late gadolinium enhancement patterns to improve risk prediction of major arrhythmic events.

Machine learning analysis of complex myocardial scar patterns affords the potential to enhance risk prediction of life-threatening arrhythmia in stable coronary artery disease (CAD). To assess the utility of computational image analysis, alongside a machine learning (ML) approach, to identify scar microstructure features on late gadolinium enhancement cardiovascular magnetic resonance (LGE-CMR) that predict major arrhythmic events in patients with CAD. Patients with stable CAD were prospectively recruited into a CMR registry. Shape-based scar microstructure features characterizing heterogeneous ('peri-infarct') and homogeneous ('core') fibrosis were extracted. An ensemble of machine learning approaches were used for risk stratification, in addition to conventional analysis using Cox modeling. Of 397 patients (mean LVEF 45.4 ± 16.0) followed for a median of 6 years, 55 patients (14%) experienced a major arrhythmic event. When applied within an ML model for binary classification, peri-infarct zone (PIZ) entropy, peri-infarct components and core interface area outperformed a model representative of the current standard of care (LVEF<35% and NYHA>Class I): AUROC (95%CI) 0.81 (0.81-0.82) vs. 0.64 (0.63-0.65), p = 0.002. In multivariate cox regression analysis, these features again remained significant after adjusting for LVEF<35% and NYHA>Class I: PIZ entropy hazard ratio (HR) 1.88, 95% confidence interval (CI) 1.38-2.56, p < 0.001; number of PIZ components HR 1.34, 95% CI 1.08-1.67, p = 0.009; core interface area HR 1.6, 95% CI 1.29-1.99, p = <0.001. Machine learning models using LGE-CMR scar microstructure improved arrhythmic risk stratification as compared to guideline-based clinical parameters; highlighting a potential novel approach to identifying candidates for implantable cardioverter defibrillators in stable CAD.

Late-Gadolinium Enhancement Interface Area and Electrophysiological Simulations Predict Arrhythmic Events in Patients With Nonischemic Dilated Cardiomyopathy.

ObjectivesThis study sought to investigate whether shape-based late gadolinium enhancement (LGE) metrics and simulations of re-entrant electrical activity are associated with arrhythmic events in patients with nonischemic dilated cardiomyopathy (NIDCM).BackgroundThe presence of LGE predicts life-threatening ventricular arrhythmias in NIDCM; however, risk stratification remains imprecise. LGE shape and simulations of electrical activity may be able to provide additional prognostic information.MethodsCardiac magnetic resonance (CMR)-LGE shape metrics were computed for a cohort of 156 patients with NIDCM and visible LGE and tested retrospectively for an association with an arrhythmic composite endpoint of sudden cardiac death and ventricular tachycardia. Computational models were created from images and used in conjunction with simulated stimulation protocols to assess the potential for re-entry induction in each patient’s scar morphology. A mechanistic analysis of the simulations was carried out to explain the associations.ResultsDuring a median follow-up of 1,611 (interquartile range: 881 to 2,341) days, 16 patients (10.3%) met the primary endpoint. In an inverse probability weighted Cox regression, the LGE–myocardial interface area (hazard ratio [HR]: 1.75; 95% confidence interval [CI]: 1.24 to 2.47; p = 0.001), number of simulated re-entries (HR: 1.40; 95% CI: 1.23 to 1.59; p < 0.01) and LGE volume (HR: 1.44; 95% CI: 1.07 to 1.94; p = 0.02) were associated with arrhythmic events. Computational modeling revealed repolarization heterogeneity and rate-dependent block of electrical wavefronts at the LGE–myocardial interface as putative arrhythmogenic mechanisms directly related to the LGE interface area.ConclusionsThe area of interface between scar and surviving myocardium, as well as simulated re-entrant activity, are associated with an elevated risk of major arrhythmic events in patients with NIDCM and LGE and represent novel risk predictors.

P1581 The global myocardial work index is a powerful predictor of major arrhythmic events in patients with organic heart disease and reduced left ventricular ejection fraction

Abstract Background Current guidelines recommend implantable cardioverter defibrillator (ICD) for primary prevention of sudden cardiac death in patients with left ventricular ejection fraction (2DE LVEF) by two-dimensional echocardiography≤ 35%. However, new echocardiography parameters of LV function such as the mechanical dispersion (MD), the LVEF by three-dimensional echocardiography (3DE) and the global myocardial work index (GWI) have been reported to provide a more accurate stratification of the arrhythmic risk, and potentially improve ICD patient selection. Purpose We wanted to compare the arrhythmic risk predictive power of the new parameters of LV function with the conventional 2DLVEF. Material and Methods we prospectively enrolled 216 patients (63 ± 12 years, 88% men) with organic heart diseases and 2DE LVEF &amp;lt;50%, in whom we re-measured LVEF using 3DE, and obtained MD and GWI using 2DE speckle tracking. Major arrhythmic events were defined as sudden cardiac death, sustained ventricular tachycardia, ventricular fibrillation and appropriate ICD shocks. We assessed the predictive power of 4 different parameters: 2DE LVEF&amp;lt; 35%; 3DE LVEF&amp;lt; 35%; MD &amp;gt; 80 ms; and GWI&amp;lt; 672 mmHg% to identify patients at risk of major arrhythmic events. Results During a mean follow-up of 27 ± 24 months, 24 patients (10%) experienced sudden cardiac death, whereas 28 patients (13%) presented major arrhythmic events. The predictive power in terms of major arrhythmic events prediction (Harrel C statistics) improved from 0.67 (95%CI 0.57-0.76) for 2DE LVEF&amp;lt; 35%, to 0.73 (95%CI 0.64-0.82) for 3DE LVEF&amp;lt; 35%, and 0.77 (95%CI 0.68-0.86) for GWI &amp;lt; 672 mm Hg%. Whereas, MD &amp;gt; 80 ms showed a limited predictive power (HCS= 0.53, 95%CI 0.41-0.76)). Conclusions GWI&amp;lt; 672 mm Hg% was the most accurate predictor of major arrhythmic events among echocardiography parameters in patients with organic heart disease and LVEF &amp;lt; 50%.

Wide QRS complex and the risk of major arrhythmic events in Brugada syndrome patients: A systematic review and meta-analysis.

BackgroundBrugada syndrome (BrS) is an inherited arrhythmic disease associated with an increased risk of major arrhythmic events (MAE). Previous studies reported that a wide QRS complex may be useful as a predictor of MAE in BrS patients. We aimed to assess the correlation of wide QRS complex with MAE by a systematic review and meta‐analysis.MethodsWe comprehensively searched the databases of MEDLINE and EMBASE from inception to June 2019. Included studies were cohort and case control studies that reported QRS duration and the relationship between wide QRS complex (>120 milliseconds) and MAE (sudden cardiac death, sudden cardiac arrest, ventricular fibrillation, sustained ventricular tachycardia, or appropriate shock). Data from each study were combined using the random‐effects model.ResultsTwenty‐two studies from 2007 to 2018 were included in this meta‐analysis involving 4,814 BrS patients. The mean age was 46.1 ± 12.8 years. The patients were predominately men (77.6%). Wide QRS duration was an independent predictor of MAE (pooled risk ratio 1.55, 95% confidence interval: 1.04‐2.30, P = .30, I 2 = 38.4%). QRS duration was wider in BrS who had history of MAE (weight mean difference = 8.12 milliseconds, 95% confidence interval: 5.75‐10.51 milliseconds).ConclusionsOur study demonstrated that QRS duration is wider in BrS who had history of MAE, and a wide QRS complex is associated with 1.55 times higher risk of MAE in BrS populations. Wide QRS complex can be considered for risk stratification in prediction of MAE in patients with BrS, especially when considering implantable cardioverter‐defibrillator placement in asymptomatic patients.

Atrial fibrillation and risk of major arrhythmic events in Brugada syndrome: A meta-analysis.

Brugada syndrome (BrS) is a common cause of sudden cardiac death (SCD). There is recent evidence that atrial fibrillation (AF) is associated with increased risk of SCD in general population. However, whether AF increases a risk of major arrhythmic events (MAE) in patients with BrS is still unclear. We performed a systematic review and meta-analysis to explore the effect of AF on MAE in BrS population. We searched the databases of MEDLINE and EMBASE from inception to March 2019. Included studies were published cohort studies reporting rates of MAE (ventricular fibrillation, sustained ventricular tachycardia, SCD, or sudden cardiac arrest) in BrS patients, with and without previous documented AF. Data from each study were combined using the random-effects model. Six studies from 1,703 patients were included. There was a significant association between AF and an increased risk of MAE in patients with BrS (pooled OR=2.37, 95% CI=1.36-4.13, p-value=.002, I2 =40.3%). Our meta-analysis demonstrated that AF is associated with an increased risk of MAE in patients with BrS.

ICD replacement in patients with intermediate left ventricular dysfunction under optimal medical treatment

BackgroundImplantable cardioverter-defibrillators (ICD) have a pivotal role in preventing major arrhythmic events in patients with severely reduced left ventricular ejection fraction (LVEF). Device replacement strategy is still controversial in patients without severely reduced left ventricular ejection fraction (LVEF) at the end of battery life. ObjectiveTo evaluate the long-term arrhythmic outcome of patients with ICD or and cardiac resynchronization therapy defibrillators (CRT-D) with normal or intermediate LVEF at the time of device replacement. MethodsAll consecutive patients with reduced ejection fraction heart failure, both from ischemic and non-ischemic origin, implanted with ICD or CRT-D for primary prevention from 2002 to 2009, were considered. The study population included patients without previous ICD interventions and without severe dysfunction (i.e. LVEF ≥ 35%) 60 [53–65] months after implantation (average battery duration). The outcome measure was the occurrence of appropriate ICD interventions in the long-term. ResultsAmong the 255 patients (150 ICDs; 105 CRT-D) evaluated, 45 (18%) had LVEF ≥ 35% without ICD interventions 5-year follow-up after implantation (15 ICD [10%]; 30 CRT-D [29%]). In the long term, ICD interventions were 4 (27%) in the ICD group and 5 (17%) in the CRT-D group. ConclusionsDespite the absence of severe left ventricular dysfunction at the time of battery replacement, a not negligible number of patients with ICD and CRT-D maintained a high risk of appropriate interventions in the long term, suggesting the opportunity of replacing the ICD regardless the amount of LV dysfunction.

Association between PR Interval, First-degree atrioventricular block and major arrhythmic events in patients with Brugada syndrome - Systematic review and meta-analysis.

BackgroundRisk stratification in patients with asymptomatic Brugada Syndrome is challenging, and despite recent advances, there is no clear evidence. The first‐degree atrioventricular block was hypothesized to be a predictor of arrhythmic events. Measurement of the PR interval and diagnosing atrioventricular block from surface ECG is easy, noninvasive, and cost‐effective. We aimed to assess the latest evidence on PR interval or first‐degree atrioventricular block and major arrhythmic events related to Brugada Syndrome.MethodsWe performed a comprehensive search in PubMed for “atrioventricular block” OR “PR interval” and “Brugada syndrome.” We included studies that have a component of PR interval and/or first‐degree atrioventricular block and major arrhythmic events related to Brugada Syndrome including syncope/VT/VF/appropriate ICD shocks/ICD implantation.ResultsWe included 1526 subjects from 7 studies. Pooled mean difference of PR interval in 4 studies showed a significant difference [MD 10.77 ms (2.97‐18.57) P = 0.007, moderate‐high heterogeneity I2 = 53% P = 0.08]. On sensitivity analysis by removing a study, it became MD 6.50 ms [1.97‐11.03], P = 0.005, heterogeneity I2 = 0% P = 0.52. Indicating that PR interval was prolonged by small margin. Pooled analysis of the association between a first‐degree atrioventricular block and major arrhythmic events was significant [OR 3.33 (2.02‐5.50) P < 0.001, low heterogeneity I2 = 0% P = 0.57].ConclusionFirst‐degree AV block is associated with more frequent major arrhythmic events in Brugada syndrome patients. PR interval seemed to be prolonged but is yet to be determined whether the PR interval association is still significant if it did not cross the first‐degree AVB threshold.

Ventricular Repolarization Dynamicity Provides Independent Prognostic Information Toward Major Arrhythmic Events in Patients With Idiopathic Dilated Cardiomyopathy

The purpose of this work was to evaluate whether ventricular repolarization dynamicity predicts major arrhythmic events in patients with idiopathic dilated cardiomyopathy (DCM). Arrhythmic risk stratification in patients with DCM is still an open issue. Ventricular repolarization analysis should provide relevant information, but QT interval and QT dispersion failed in predicting arrhythmic risk. The following parameters were evaluated in 179 consecutive DCM patients without history of sustained ventricular tachycardia (VT) and/or ventricular fibrillation (VF) at enrollment: QRS duration, QT interval corrected for heart rate, and QT dispersion at electrocardiogram (ECG); left ventricular ejection fraction (LVEF) and left ventricular end-diastolic diameter at echocardiogram; and nonsustained ventricular tachycardia (NSVT), heart rate variability (standard deviation of RR intervals), and ventricular repolarization dynamicity as measured by means of 24-h ECG monitoring, by calculating the slope of linear regression analysis of QT end and RR intervals (QTe-slope) and the value of mean QT end corrected for heart rate. During a mean follow-up of 39 months, 9 patients died suddenly and 15 experienced VT and/or VF. At multivariate analysis, LVEF (p = 0.047), NSVT (p = 0.022), and QTe-slope (p = 0.034) were significantly associated with arrhythmic events. Among the patients with a low LVEF, NSVT and/or steeper QTe-slope identified a subgroup at highest arrhythmic risk. In patients with DCM, QT dynamicity is independently associated with the occurrence of major arrhythmic events and improves the predictive accuracy of stratifying arrhythmic risk of these patients.

Autonomic Control in Patients Experiencing Atrial Fibrillation After Cardiac Surgery

Atrial fibrillation (AF) occurs in 20-40% of patients after open heart surgery and leads to an increased morbidity and prolonged hospital stay. Earlier studies have demonstrated that depressed baroreflex function predicts mortality and major arrhythmic events in patients surviving myocardial infarction. Cardiac surgery per se leads to decreased baroreflex sensitivity (BRS) and heart rate variability (HRV). Hence, the present study was aimed at analyzing the impact of the cardiovascular autonomous system on the development of postsurgical AF. The study covered 51 patients who consecutively underwent aortic valve replacement, coronary artery bypass surgery, or combined procedures. Noninvasive blood pressure and ECG were recorded the day before and 24 hour after surgery. BRS, linear as well as nonlinear HRV parameters were calculated using established methods. Eighteen patients developed AF during the first postoperative week, while 33 remained in sinus rhythm (SR) throughout the observation period. Patients with postoperative (PostOp) AF exhibited a significantly reduced preoperative (PreOp) BRS in terms of bradycardic and tachycardic regulation (average delayed slope [ms/mmHg]: SR: PreOp: 9.83 +/- 3.26, PostOp: 6.02 +/- 2.29, Pre-Post: P < 0.001; AF: PreOp: 7.59 +/- 1.99, PostOp: 6.39 +/- 3.67, Pre-Post: P < 0.044; AF vs SR: PreOp: P < 0.01, PostOp: ns). In both groups, surgery caused a decrease of BRS and HRV. Analysis of nonlinear dynamics revealed a tendency toward decreased system complexity caused by the operation; this trend was significant in patients remaining in sinus rhythm. Patients experiencing postoperative AF obviously suffer from an impaired BRS before surgery already. These findings may be used to guide prophylactic antiarrhythmic therapy.

Pacing-Induced Increase in QT Dispersion Predicts Sudden Cardiac Death Following Cardiac Resynchronization Therapy

This study was designed to determine whether cardiac resynchronization therapy (CRT) by means of biventricular pacing (BiVP) alters the QT interval (QT(c)) and QT dispersion (QTD), and whether such changes relate to the risk of developing major arrhythmic events (MAE). Prolonged QT(c) is associated with MAE. Left ventricular pacing and BiVP alter QT(c). A total of 75 patients with drug-resistant heart failure (New York Heart Association functional class III/IV) and QRS duration > or =120 ms underwent CRT. The QT(c) and QTD were measured before and 48 days after BiVP. Over 807 days (range 93 to 1,543 days), 11 patients had a MAE. Compared to baseline, at 48 days after CRT, QTD increased in 47% of patients and QT(c) decreased in 53%. The QT(c) at follow-up was higher in MAE patients compared with no-MAE patients (35.9 +/- 14.2 ms vs. 0.52 +/- 6.0 ms; p = 0.0323). Similar differential responses for QTD were observed (46.4 +/- 13.5 ms in MAE vs. -5.1 +/- 4.1 ms in no MAE, p < 0.0001). The MAE occurred in 29% of patients exhibiting an increase in QTD and in 3% of those exhibiting a decrease (p = 0.0017). In multiple regression analyses, change in QTD from baseline (DeltaQTD) strongly predicted MAE, independent of DeltaQT(c), QRS duration, and left ventricular ejection fraction and end-diastolic volume (p < 0.001). Differences in survival curves were observed when patients were dichotomized according to whether QTD increased or decreased in relation to baseline values (p < 0.0001). The MAE in patients with BiVP are related to pacing-induced increases in QTD. Measures of ventricular repolarization at the time of pacemaker implantation may guide selection of patients for combined CRT and defibrillator therapy.

Symbolic Dynamics of Heart Rate Variability

Sympathetic and parasympathetic systems are considered the principal rapidly reacting systems that control heart rate. We propose a symbolic analysis series to quantify the prevalence of sympathetic or parasympathetic cardiac modulation. This analysis decomposes the heart rate variability series in patterns lasting 3 beats and classifies them into 3 categories: nonvariable, variable, and very variable patterns referred to as 0V, 1V, and 2V patterns. First, we applied this method to experimental and pharmacological conditions characterized by sympathetic activation (tilt test, handgrip, nitroprusside, and high-dose atropine administration) or parasympathetic activation (phenylephrine and low-dose atropine administration) in 60 healthy subjects. An increase in sympathetic modulation and a vagal withdrawal elicited a significant increase in 0V patterns and a decrease in 2V patterns, whereas parasympathetic dominance induced the opposite, reflecting a reciprocal sympathovagal balance. The second part of the study considered a series of 300 beats before the onset of major arrhythmic events in patients with an implantable cardioverter-defibrillator. Symbolic analysis detected an increase in the percentage of 0V patterns before the onset of major arrhythmias compared with baseline (41.6+/-3.9% and 24.4+/-2.9%, respectively; P<0.01), indicating a sympathetic prevalence. On the other hand, the 2V patterns did not decrease before major arrhythmias, suggesting the presence of nonreciprocal autonomic modulations. Symbolic analysis of 3 beat sequences takes into account the different time course of sympathetic and parasympathetic cardiac modulations and seems appropriate for elucidating the neural pathophysiological mechanisms occurring during the short periods that precede acute cardiac events.

Long Runs of Non‐Sustained Ventricular Tachycardia on 24‐Hour Ambulatory Electrocardiogram Predict Major Arrhythmic Events in Patients with Idiopathic Dilated Cardiomyopathy

This study examined the prognostic significance of the rate and length of non-sustained (NS) ventricular tachycardia (VT) on 24-hour ambulatory electrocardiograms (ECG) recorded in 343 patients with idiopathic dilated cardiomyopathy (IDC) in the prospective Marburg Cardiomyopathy study. NSVT was defined as >/=3 consecutive ventricular premature beats at >120 bpm. During 52 +/- 21 months of follow-up, major arrhythmic events defined as sustained VT, VF, or sudden cardiac death occurred in 46 of 343 patients (13%). Patients with 3-4 beat runs of NSVT had a similar arrhythmia-free survival as patients without NSVT on baseline 24-hour ambulatory ECG. The incidence of major arrhythmic events during follow-up increased significantly from 2% per year in patients without NSVT, to 5% per year in patients with 5-9 beat runs of NSVT, to 10% per year in patients with >/=10 beat runs of NSVT (P < 0.05). Unlike the length, the rate of NSVT was similar in patients with versus without subsequent major arrhythmic events (163 +/- 23 vs 160 +/- 24 bpm). Thus, the length but not the rate of NSVT on 24-hour ambulatory ECG was a predictor of major arrhythmic events in patients with IDC. The presence of NSVT with >/=10 beat runs on ambulatory ECG was associated with a particularly high risk of major arrhythmic events.

Arrhythmia Risk Prediction in Idiopathic Dilated Cardiomyopathy Based on Heart Rate Variability and Baroreflex Sensitivity

This study examined the relation between heart rate variability (HRV) and baroreflex sensitivity (BRS) and subsequent major arrhythmic events (MAE), defined as sustained VT, VF or sudden death, in 263 patients with idiopathic dilated cardiomyopathy (IDC) in sinus rhythm. The predefined measure of HRV was the standard deviation of all normal-to-normal RR intervals (SDNN) on baseline 24-hour ambulatory ECG. BRS was determined by the phenylephrine method. Over 52 +/- 21 months of follow-up, MAE occurred in 38 patients (14%). SDNN at baseline 24-hour ambulatory ECG (106 +/- 46 vs 109 +/- 45, ns) and BRS (7.9 +/- 5.5 vs 7.7 +/- 5.3 ms/mmHg, ns) were both similar in patients with versus without MAE during follow-up. In contrast, left ventricular ejection fraction was significantly lower in patients with versus without MAE (24%+/- 7% vs 31%+/- 10%, P < 0.019. Neither HRV nor BRS predicted MAE in patients with IDC.

Prognostic value of heart rate variability for sudden death and major arrhythmic events in patients with idiopathic dilated cardiomyopathy

OBJECTIVEThis study was designed to evaluate the prognostic value of heart rate variability for sudden death, resuscitated ventricular fibrillation or sustained ventricular tachycardia in patients with idiopathic dilated cardiomyopathy.BACKGROUNDPrevious studies have shown that heart rate variability could predict arrhythmic events and sudden death in postinfarction patients, but the prognostic value of heart rate variability for arrhythmic events or sudden death in patients with idiopathic dilated cardiomyopathy has not been established.METHODSTime and frequency domain analysis of heart rate variability on 24-h electrocardiographic (ECG) recording was assessed in 116 patients with idiopathic dilated cardiomyopathy (91 men, aged 51 ± 12 years, left ventricular ejection fraction 34 ± 12%).RESULTSMean follow-up (± SD) was 53 ± 39 months. Sixteen patients reached one of the defined study end-points (sudden death, resuscitated ventricular fibrillation or sustained ventricular tachycardia) during follow-up. Using multivariate analysis, only reduced standard deviation of all normal-to-normal intervals (SDNN) (p = 0.02) and ventricular tachycardia during 24-h ECG recording (p = 0.02) predicted sudden death and/or arrhythmic events. For SDNN, a cutoff level of 100 ms seemed the best for the risk stratification.CONCLUSIONSDecrease in heart rate variability is an independent predictor of arrhythmic events and sudden death in idiopathic dilated cardiomyopathy, whether the mechanism of sudden death is ventricular tachyarrhythmia or not.