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ObjectiveTo explore the left and right ventricular myocardial strain and dyssynchrony in patients with Micra AV leadless pacing implantation, and to further analyze the impact of implantation site on myocardial strain and dyssynchrony. MethodsA retrospective study was conducted on 43 patients with Micra AV implantation and 20 patients with high-degree atrioventricular block (Ⅱdegree typeⅡand Ⅲ degree atrioventricular block) at the Department of Cardiology, Zhongshan Hospital from April 2023 to December 2023. The demographic information and clinical characteristics of the patients were collected. Echocardiography and speckle tracking imaging techniques were used to obtain conventional echocardiographic parameters, myocardial strain, and dyssynchrony indices of patients in the two groups, including global longitudinal strain (GLS), free wall longitudinal strain (FWLS), peak strain dispersion (PSD) of 18 left ventricular segments, PSD of 6 right ventricular segments, and other indices. According to the implantation location of Micra AV, the patients were further divided into middle group (right ventricular septum), high group (right ventricular inflow tract), and low group (apical region), and the differences in myocardial strain and dyssynchrony indices among the three subgroups were compared. ResultsThe left ventricular GLS (LVGLS), right ventricular GLS (RVGLS), and right ventricular FWLS (RVFWLS) of the Micra AV group were significantly lower than those of the conduction block group (P＜0.001), and the right ventricular dyssynchrony of the Micra AV group was significantly higher than that of the conduction block group (P＜0.05). Comparison of myocardial strain and dyssynchrony at different implantation sites showed that the LVGLS of the high implantation group was significantly higher than that of the middle and low implantation groups, and the left ventricular dyssynchrony index Yu was significantly lower than that of the middle group (P＜0.05); the right ventricular ejection fraction (RVEF) of the low implantation group was significantly lower than that of the high group, and the right ventricular 6-segment PSD was significantly higher than that of the middle and high implantation groups (P＜0.05). ConclusionsCompared with patients with high-degree atrioventricular block, patients with Micra AV leadless pacing have reduced left and right ventricular strain, and the implantation of low position had greater effect.

Chronic right ventricular (RV) pacing is an often-unrecognized cause of cardiomyopathy, despite research that has revealed that chronic RV pacing can cause significant cardiomyopathy and heart failure, leading causes of hospitalization in the United States. Studies have found that chronic RV apical pacing results in ventricular dyssynchrony, reduced cardiac function, and heart failure. This article describes the deleterious effects of permanent cardiac pacemakers and their association with cardiomyopathy and heart failure. More research is needed to investigate other forms of pacing and treatment to prevent ventricular dyssynchrony and myocardial remodeling. [ABSTRACT FROM AUTHOR]

The author discusses a study published in the issue which evaluated the effects after leadless pacing (LPM) Micra implantation on biventricular function and tricuspid regurgitation (TR) in patients over a follow-up period of 12.2 months. Topics include the observed decline in both left ventricular (LV) and right ventricular (RV) systolic function overtime, importance of proper and early recognition of TR, and the frequency and under-recognition of pacing-induced TR.

Purpose of the Review: Dyssynchrony occurs when portions of the cardiac chambers contract in an uncoordinated fashion. Ventricular dyssynchrony primarily impacts the left ventricle and may result in heart failure. This entity is recognized as a major contributor to the development and progression of heart failure. A hallmark of dyssynchronous heart failure (HFd) is left ventricular recovery after dyssynchrony is corrected. This review discusses the current understanding of pathophysiology of HFd and provides clinical examples and current techniques for treatment. Recent Findings: Data show that HFd responds poorly to medical therapy. Cardiac resynchronization therapy (CRT) in the form of conventional biventricular pacing (BVP) is of proven benefit in HFd, but is limited by a significant non-responder rate. Recently, conduction system pacing (His bundle or left bundle branch area pacing) has also shown promise in correcting HFd. Summary: HFd should be recognized as a distinct etiology of heart failure; HFd responds best to CRT. [ABSTRACT FROM AUTHOR]

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Electrical disturbances, such as atrial fibrillation (AF), dyssynchrony, tachycardia, and premature ventricular contractions (PVCs), are present in most patients with heart failure (HF). While these disturbances may be the consequence of HF, increasing evidence suggests that they may also cause or aggravate HF. Animal studies show that longer-lasting left bundle branch block, tachycardia, AF, and PVCs lead to functional derangements at the organ, cellular, and molecular level. Conversely, electrical treatment may reverse or mitigate HF. Clinical studies have shown the superiority of atrial and pulmonary vein ablation for rhythm control and AV nodal ablation for rate control in AF patients when compared with medical treatment. Ablation of PVCs can also improve left ventricular function. Cardiac resynchronization therapy (CRT) is an established adjunct therapy currently undergoing several interesting innovations. The current guideline recommendations reflect the safety and efficacy of these ablation therapies and CRT, but currently, these therapies are heavily underutilized. This review focuses on the electrical treatment of HF with reduced ejection fraction (HFrEF). We believe that the team of specialists treating an HF patient should incorporate an electrophysiologist in order to achieve a more widespread use of electrical therapies in the management of HFrEF and should also include individual conditions of the patient, such as body size and gender in therapy fine-tuning. [ABSTRACT FROM AUTHOR]

Congenital complete atrioventricular block (CCAVB) is usually due to failure of atrioventricular nodal conduction with preservation of the His‐Purkinje system. Most patients with CCAVB ultimately require pacemaker therapy to restore physiologic heart rates, dealing with the detrimental effects of chronic right ventricular (RV) pacing on cardiac structure and function. The ideal stimulation pattern aims to mimic the normal conduction to restore electromechanical coupling, preventing the harmful effects of lack of atrioventricular and inter‐intraventricular synchrony. This can be done through conduction system pacing. Using His bundle pacing (HBP) for cardiac resynchronization therapy in two complete congenital atrioventricular block patients, we have reported better exercise tolerance and echocardiographic improvements related to reversible left ventricular dysfunction that can be corrected by restoration of the normal activation pathway via the His‐Purkinje network. [ABSTRACT FROM AUTHOR]

Abstract Congenital complete atrioventricular block (CCAVB) is usually due to failure of atrioventricular nodal conduction with preservation of the His‐Purkinje system. Most patients with CCAVB ultimately require pacemaker therapy to restore physiologic heart rates, dealing with the detrimental effects of chronic right ventricular (RV) pacing on cardiac structure and function. The ideal stimulation pattern aims to mimic the normal conduction to restore electromechanical coupling, preventing the harmful effects of lack of atrioventricular and inter‐intraventricular synchrony. This can be done through conduction system pacing. Using His bundle pacing (HBP) for cardiac resynchronization therapy in two complete congenital atrioventricular block patients, we have reported better exercise tolerance and echocardiographic improvements related to reversible left ventricular dysfunction that can be corrected by restoration of the normal activation pathway via the His‐Purkinje network.

Background: Delivery of cardiac resynchronization therapy (CRT) requires left ventricular myocardial capture to achieve clinical benefits., Objective: We sought to determine whether ineffective pacing affects survival., Methods: Ineffective ventricular pacing (VP) was defined as the difference between the percentage of delivered CRT (%VP) and the percentage of effective CRT in CRT devices. Using the Optum de-identified electronic health record data set and Medtronic CareLink data warehouse, we identified patients implanted with applicable devices with at least 30 days of follow-up. Kaplan-Meier and Cox proportional hazards models assessed the impact of %VP and % ineffective VP on survival., Results: Among 7987 patients with 2.1 ± 1.0 years of follow-up, increasing ineffective VP was associated with decreasing survival: the highest observed survival was in the quartile with <0.08% ineffective VP and the lowest survival was in the quartile with >1.47% ineffective VP (85.1% vs 75.7% at 3 years; P < .001). As expected, patients with more than the median %VP of 97.7% had better survival than did patients with <97.7% VP (84.2% vs 77.8%; P < .001). However, patients who had >97.7% VP but >2% ineffective VP had similar survival to patients with <97.7% VP but ≤2% ineffective VP (81.6% vs 79.4%; P = .54). A multivariable Cox proportional hazards model demonstrated that <97.7% VP (adjusted hazard ratio 1.29; 95% confidence interval 1.14-1.46; P < .001) and >2% ineffective VP (hazard ratio 1.35; 95% confidence interval 1.18-1.54; P < .001) were both significantly associated with decreased survival., Conclusion: Ineffective VP is associated with decreased survival. In addition to maximizing the percentage of delivered CRT pacing, every effort should be made to minimize ineffective VP., Competing Interests: Disclosures Dr Mittal serves as a consultant to Boston Scientific and Medtronic. Drs Koehler, Stadler, Ghosh, and Klepfer are employees and shareholders of Medtronic. Dr Piccini is supported by R01AG074185 from the National Institutes of Aging. He also receives grants for clinical research from Abbott, the American Heart Association, Boston Scientific, iRhythm, and Philips and serves as a consultant to ABVF, Abbott, AbbVie, Boston Scientific, ElectroPhysiology Frontiers, Kardium, LivaNova, Medtronic, Milestone Pharmaceuticals, Sanofi, Philips, and UpToDate. The rest of the authors report no conflicts of interest., (Copyright © 2024 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: This study aimed to evaluate the feasibility and clinical value of real time three‐dimensional echocardiography (RT‐3DE) for assessing ventricular systolic dysfunction and dyssynchrony in children with an functional single right ventricle (FSRV) having undergone the Fontan procedure. Methods: Twenty‐five children with an FSRV and 25 healthy children were enrolled in our study. RV volume analysis was performed compared with magnetic resonance imaging (MRI) as the reference standard in FSRV patients. The patients were divided into wide and narrow QRS interval groups. Global and regional functions of the RV in three compartments (inflow, body, and outflow) were compared between FSRV and control subjects, including RV systolic dyssynchrony indices of maximal difference of time to minimal volume (Tmsv‐Dif), standard deviation of time to minimal volume (Tmsv‐SD), maximal difference of time to minimal volume corrected by R‐R interval (Tmsv‐Dif%), and standard deviation of time to minimal volume corrected by R‐R interval (Tmsv‐SD%). Results: RT‐3DE measurements were significantly lower than MRI measurements for RV‐EDV, RV‐ESV, RV‐SV, and RVEF (p < 0.01).Compared with controls, patients with an FRSV had significantly higher dyssynchrony indices and significantly lower global EF in both narrow QRS interval and wide QRS interval groups. Tmsv‐SD% was shown to be most strongly correlated with MRI‐RVEF (r = −.570, p = 0.003). Conclusions: RT‐3DE tended to underestimate RV ventricular volume in children with FSRV. Children with an FSRV and either a wide or narrow QRS interval had reduced ventricular function and higher dyssynchrony than normal subjects. Worsening RV dyssynchrony is associated with overall decline in function after the Fontan operation. [ABSTRACT FROM AUTHOR]

Right ventricular apex (RVA) is still the most common implanted site in the world. There are a large number of RVA pacing population who have been carrying dual-chamber permanent pacemaker (PPM) over decades. Comparison of left ventricular dyssynchrony, morphology and systolic function between RVA pacing population and healthy population is unknown. This case-control study enrolled 61 patients suffered from complete atrioventricular block (III°AVB) for replacement of dual-chamber PPM. Then, 61 healthy controls matched with PPM patients in gender, age, follow-up duration and complications were included. The lead impedance, pacing threshold and sensing were compared between at implantation and long-term follow-up. Left ventricular (LV) dyssynchrony, morphology and systolic function were compared between RVA pacing population (RVA group) and healthy population (healthy group) at implantation (baseline) and follow-up. And clarify the predictors of LV systolic function in RVA group at follow-up. After 112.44 ± 34.94 months of follow-up, comparing with parameters at implantation, atrial lead impedance decreased significantly (690 ± 2397 Ω vs 613 ± 2257 Ω， p = 0.048); atrial pacing threshold has a increased trend and P-wave amplitude has a decreased trend, but there was no statistical differences; while, RVA ventricular lead threshold increased significantly (0.50 ± 0.23 V vs 0.91 ± 0.47 V， p < 0.001), impedance (902 ± 397 Ω vs 680 ± 257 Ω， p < 0.001) and R-wave amplitude (11.71 ± 9.40mv vs 7.00 ± 6.91 mv， p < 0.001) decreased significantly. Compared with healthy group, long-term RVA pacing significantly increased ventricular dyssynchrony (mean QRS duration, 156.21 ± 29.80 ms vs 97.08 ± 15.70 ms， p < 0.001), left atrium diameter (LAD, 40.61 ± 6.15 mm vs 37.49 ± 4.80 mm， p = 0.002), left ventricular end-diastolic diameter (LVEDD, 49.15 ± 5.93 mm vs 46.41 ± 3.80 mm， p = 0.003), left ventricular hypertrophy (LVMI, 121.86 ± 41.52 g/m2 vs 98.41 ± 25.29 g/m2， p < 0.001), significantly deteriorated degree of tricuspid regurgitation (p < 0.001), and significantly decreased left ventricular ejection fraction (LVEF, 61.38 ± 8.10% vs 64.64 ± 5.85%, p = 0.012), but after long-term RVA pacing, the mean LVEF was still more than 50%. Long-term RVA group LVEF was negatively correlated with preimplantation LVMI (B = -0.055， t = −2.244， p = 0.029), LVMI at follow-up (B = −0.081， t = −3.864， p = 0.000) and tricuspid regurgitation at follow-up (B = −3.797， t = −3.599， p = 0.001). In conclusion, although long-term RVA pacing has significantly effects on left ventricular dyssynchrony, morphology and systolic function in III°AVB patients, the mean LVEF is still >50%. High preimplantation LVMI can predict the decline of LVEF. • We have compared long-term changes of RVA pacing lead parameters as well as LV asynchrony, morphology and function difference between RVA pacing and healthy people at follow-up. • Furthermore, we have identified the predictors for decline of LVEF at follow-up. • To the best of our knowledge, this is the first study evaluation the comprehensive information of RVA pacing at 10 years follow-up, especially comparing with healthy people. [ABSTRACT FROM AUTHOR]

Background: Right ventricular (RV) pacing causes delayed activation of remote ventricular segments. We used the ultra‐high‐frequency ECG (UHF‐ECG) to describe ventricular depolarization when pacing different RV locations. Methods: In 51 patients, temporary pacing was performed at the RV septum (mSp); further subclassified as right ventricular inflow tract (RVIT) and right ventricular outflow tract (RVOT) for septal inflow and outflow positions (below or above the plane of His bundle in right anterior oblique), apex, anterior lateral wall, and at the basal RV septum with nonselective His bundle or RBB capture (nsHBorRBBp). The timings of UHF‐ECG electrical activations were quantified as left ventricular lateral wall delay (LVLWd; V8 activation delay) and RV lateral wall delay (RVLWd; V1 activation delay). Results: The LVLWd was shortest for nsHBorRBBp (11 ms [95% confidence interval = 5–17]), followed by the RVIT (19 ms [11–26]) and the RVOT (33 ms [27–40]; p <.01 between all of them), although the QRSd for the latter two were the same (153 ms (148–158) vs. 153 ms (148–158); p =.99). RV apical capture not only had a longer LVLWd (34 ms (26–43) compared to mSp (27 ms (20–34), p <.05), but its RVLWd (17 ms (9–25) was also the longest compared to other RV pacing sites (mean values for nsHBorRBBp, mSp, anterior and lateral wall captures being below 6 ms), p <.001 compared to each of them. Conclusion: RVIT pacing produces better ventricular synchrony compared to other RV pacing locations with myocardial capture. However, UHF‐ECG ventricular dysynchrony seen during RVIT pacing is increased compared to concomitant capture of basal septal myocytes and His bundle or proximal right bundle branch. [ABSTRACT FROM AUTHOR]

Background: Nonfluoroscopic 3-dimensional (3D) electroanatomic mapping systems (EAMs) have been developed to guide cardiac catheter navigation and reduce fluoroscopy. Selective right ventricular (RV) septal pacing could prevent pacing-induced left ventricular (LV) dysfunction.Objective: The purpose of this study was to determine whether EAM-guided selective RV septal pacing preserves LV contractility/synchrony in pediatric patients with complete atrioventricular block (CAVB) and no other congenital heart defects.Methods: Prospective analysis of children/adolescents who underwent EAM-guided selective RV pacing was performed. A 3D pacing map guided ventricular lead implantation at septal sites with narrow paced QRS. Serial echocardiograms were obtained after pacemaker implantation to monitor for function (volumes, ejection fraction [EF], global longitudinal/circumferential strain) and synchrony (interventricular mechanical delay, septal to posterior wall motion delay, systolic dyssynchrony index). Data are reported as median (25th-75th percentile).Results: Thirty-two CAVB patients (age 9.8 [7.0-14.0] years; 11 with a previous pacing system) underwent selective RV septal pacing (13 DDD, 19 VVIR pacemaker; midseptum 22, parahisian 7, RV outflow tract 3) with narrow paced QRS (110 [100-120] ms) and low radiation exposure. Follow-up over 24 (5-33) months showed preserved LV function and synchrony, without significant differences between pacing sites (midseptum-parahisian) and mode (VVIR-DDD). EF decreased after implantation in patients without previous pacing, although values were mainly within normal limits. Three parahisian patients underwent early lead repositioning.Conclusion: EAM-guided selective RV septal pacing is a feasible technique associated with preserved LV systolic function and synchrony and low radiation exposure in pediatric patients with CAVB. [ABSTRACT FROM AUTHOR]

R-wave singularity (RWS) measures the intermittence or discontinuousness of R waves. It has been broadly used in QRS (QRS complex of electrocardiogram) detection, electrocardiogram (ECG) beats classification, etc. In this article, we novelly developed RWS to the analysis of QRS morphology as the measurement of ventricular dyssynchrony and tested the hypothesis that RWS could enhance the discrimination between control and acute myocardial infarction (AMI) patients. Holter ECG recordings were obtained from the Telemetric and Holter ECG Warehouse database, among which database Normal was extracted as normal controls (n = 202) and database AMI (n = 93) as typical subjects of autonomic nervous system dysfunction and cardiac electrical dyssynchrony with high risk for cardiac arrhythmias and sudden cardiac death. Experimental results demonstrate that RWS measured by Lipschitz exponent calculated from 5-min Holter recordings was significantly less negative in early AMI and late AMI than that in Normal subjects for overall, elderly, and elderly male groups, which suggested the heterogeneous depolarization of the ventricular myocardium during AMI. Receiver operating characteristic curve analyses show that combined with heart rate variability parameters, Lipschitz exponent provides higher accuracy in distinguishing between the patients with AMI and healthy control subjects for overall, elderly, elderly male, and elderly female groups. In summary, our study demonstrates the significance of using RWS to probe the cardiac electrical dyssynchrony for AMI. Lipschitz exponent may be valuable and complementary for existing cardiac resynchronization therapy and autonomic nervous system assessment.

R-wave singularity (RWS) measures the intermittence or discontinuousness of R waves. It has been broadly used in QRS (QRS complex of electrocardiogram) detection, electrocardiogram (ECG) beats classification, etc. In this article, we novelly developed RWS to the analysis of QRS morphology as the measurement of ventricular dyssynchrony and tested the hypothesis that RWS could enhance the discrimination between control and acute myocardial infarction (AMI) patients. Holter ECG recordings were obtained from the Telemetric and Holter ECG Warehouse database, among which database Normal was extracted as normal controls (n = 202) and database AMI (n = 93) as typical subjects of autonomic nervous system dysfunction and cardiac electrical dyssynchrony with high risk for cardiac arrhythmias and sudden cardiac death. Experimental results demonstrate that RWS measured by Lipschitz exponent calculated from 5-min Holter recordings was significantly less negative in early AMI and late AMI than that in Normal subjects for overall, elderly, and elderly male groups, which suggested the heterogeneous depolarization of the ventricular myocardium during AMI. Receiver operating characteristic curve analyses show that combined with heart rate variability parameters, Lipschitz exponent provides higher accuracy in distinguishing between the patients with AMI and healthy control subjects for overall, elderly, elderly male, and elderly female groups. In summary, our study demonstrates the significance of using RWS to probe the cardiac electrical dyssynchrony for AMI. Lipschitz exponent may be valuable and complementary for existing cardiac resynchronization therapy and autonomic nervous system assessment. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate right ventricle (RV) dyssynchrony and its relation with mortality using speckle‐tracking echocardiography (STE) in patients with acute inferior myocardial infarction (IMI). Methods: One hundred and fifty‐eight consecutive patients with acute IMI treated with primary percutaneous coronary intervention, and 44 healthy subjects were included. RV myocardial involvement (RVMI) was defined as an elevation >1 mm in V1 or V4R and/or the presence of a culprit lesion at the proximal portion of the first RV marginal branch after reviewing coronary angiography. Patients were followed for 3 years to determine the cardiovascular mortality. Results: Overall, 70 patients with IMI had RVMI. IMI patients had significantly higher RV peak systolic longitudinal strain dyssynchrony (PLSSD) index, lower peak longitudinal systolic strain (PLSS), longer time to PLSS, and time to PLSS differences compared to healthy controls while the patients with RVMI had significantly worse values compared to patients without RVMI and healthy controls. Twenty‐seven patients (17.1%) died within 2 years. RVMI was more prevalent in mortality group, and they had significantly higher RV PSSD index, whereas they had lower RV free wall PLSS and longer time to PLSS differences. Receiver operating characteristics (ROC) analysis revealed that a RV PLSSD index > 65 ms predicted mortality with a sensitivity of 88.9% and specificity of 71.8% in IMI patients. Conclusions: Intra‐ and inter‐ventricular dyssynhcrony may develop in patients with acute IMI, especially in those with RV involvement, which might have a negative effect on the prognosis of these patients. [ABSTRACT FROM AUTHOR]

Copyright of Medical Review - Cardiovascular Diseases is the property of Medical University - Sofia, Central Medical Library and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Pacing is an established and ubiquitous treatment of bradycardias and some types of heart failure. The optimal pacing lead position which maximizes cardiac function and minimizes deterioration of ventricular function remains controversial. The desire to achieve a physiological pacing system that mimics cardiac function has led to the investigation of several potential pacing sites. This editorial provides an overview of past and current pacing lead position and summaries the current and future direction of physiological pacing. [ABSTRACT FROM AUTHOR]

Pacing is a well established therapy for bradycardia support and certain types of heart failure. Despite technological advances the optimal pacing lead position remains controversial. Right ventricular pacing, particularly apical has been the site of choice but the induction of abnormal cardiac depolarization and the recognition of an increased risk of impairment of left ventricular systolic function, heart failure and mortality has driven a desire for a true physiological pacing system. A number of different lead positions have been determined and of these His bundle pacing appears to most closely mimic normal ventricular conduction. This article reviews the background to the development of physiological pacing, evaluates historical data for right ventricular pacing and the basis for change and new lead positions. [ABSTRACT FROM AUTHOR]

Various degree of ventricular activation by accessory pathway (AP) and normal conduction system in a patient with pre-excited atrial fibrillation (AF) may lead to ventricle dyssynchrony and cardiomyopathy. [ABSTRACT FROM AUTHOR]

Permanent His bundle pacing (PHBP) has shown significant clinical benefits in patients requiring ventricular pacing compared with conventional right ventricular pacing. There is an emerging role for PHBP in patients with interventricular dyssynchrony. This article reviews the mechanisms and the available data on the use of PHBP in overcoming dyssynchrony. [ABSTRACT FROM AUTHOR]

Echocardiographic assessment of left ventricular mechanical dyssynchrony (LVMD) received great interest with the appearance of Cardiac resynchronization therapy ever since the first successful implants. Recent guidelines still keep QRS duration as the main selection criterion for diagnosing the presence of LVMD. However, measurement of QRS duration, which is an electrical phenomenon, seems to provide only a crude estimate on myocardial activation and is poorly correlated with the presence of LVMD. Echocardiography seems to be a more reliable tool for correctly identifying candidates for CRT and thus reducing the number of clinical non-responders. Recently LMVD was found to be associated with other cardiac and noncardiac diseases. Therefore, echocardiographic assessment of LVMD will always remain of importance. The aim of this article is to present a simplified, step-wise approach for the assessment of LVMD which can be easily followed and performed by echocardiographers to produce reliable, reproducible results for the assessment of LVMD.

Purpose: The aim of this proof-of-concept study is to introduce new high-dynamic ECG technique with potential to detect temporal-spatial distribution of ventricular electrical depolarization and to assess the level of ventricular dyssynchrony.Methods: 5-kHz 12-lead ECG data was collected. The amplitude envelopes of the QRS were computed in an ultra-high frequency band of 500-1000 Hz and were averaged (UHFQRS). UHFQRS V lead maps were compiled, and numerical descriptor identifying ventricular dyssynchrony (UHFDYS) was detected.Results: An electrical UHFQRS maps describe the ventricular dyssynchrony distribution in resolution of milliseconds and correlate with strain rate results obtained by speckle tracking echocardiography. The effect of biventricular stimulation is demonstrated by the UHFQRS morphology and by the UHFDYS descriptor in selected examples.Conclusions: UHFQRS offers a new and simple technique for assessing electrical activation patterns in ventricular dyssynchrony with a temporal-spatial resolution that cannot be obtained by processing standard surface ECG. The main clinical potential of UHFQRS lies in the identification of differences in electrical activation among CRT candidates and detection of improvements in electrical synchrony in patients with biventricular pacing. [ABSTRACT FROM AUTHOR]

Background: Stress-induced dyssynchrony has been shown to be independently correlated with clinical outcomes in patients with dilated cardiomyopathy (DCM) and narrow QRS complexes. However, the extent to which stress levels affect inter- and intraventricular dyssynchrony parameters remains unknown.Methods: Ten large dogs were submitted to tachycardia-induced DCM by pacing the right ventricular apex for 3-4 weeks to reach a target ejection fraction (EF) of 35% or less. Stress was then induced in DCM dogs by administering intravenous dobutamine up to a maximum of 20 μg·kg-1·min-1. Hemodynamic and ventricular dyssynchrony data were analyzed by left ventricular (LV) pressure measurements and gated blood pool SPECT (GBPS) imaging. In order to assess mechanical dyssynchrony in DCM subjects and compare it with that of 8 normal counterparts, we extracted the following data: count-based indices of LV contraction homogeneity index (CHI), entropy and phase standard deviation, and interventricular dyssynchrony index.Results: A significant LV intraventricular dyssynchrony (CHI: 96.4 ± 1.3% in control vs 78.6% ± 10.9% in DCM subjects) resulted in an intense LV dysfunction in DCM subjects (EF: 49.5% ± 8.4% in control vs 22.6% ± 6.0% in DCM), compared to control subjects. However, interventricular dyssynchrony did not vary significantly between the two groups. Under stress, DCM subjects showed a significant improvement in ventricular functional parameters at each level (EF: 22.6% ± 6.0% at rest vs 48.1% ± 5.8% at maximum stress). All intraventricular dyssynchrony indices showed a significant increase in magnitude of synchrony from baseline to stress levels of greater than or equal to 5 μg·kg-1·min-1 dobutamine. There were individual differences in the magnitude and pattern of change in interventricular dyssynchrony during the various levels of stress.Conclusions: Based on GBPS analyses, different levels of functional stress, even in close intervals, can have a significant impact on hemodynamic and intraventricular dyssynchrony parameters in a DCM model with narrow QRS complex. [ABSTRACT FROM AUTHOR]