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Aims: From a patient and health system perspective, managing worsening heart failure (WHF) as an outpatient has become a priority. Remote management allows early detection of WHF, enabling timely intervention with the aim of preventing hospitalization. The objective of the study was to evaluate the feasibility and safety of remotely managing WHF events using a multiparametric platform., Methods and Results: All patients enrolled in the heart failure remote management programme of the Bordeaux University Hospital Telemedicine Center between 1 January and 31 December 2021 were included in the study. Follow-up data were collected until 1 March 2022. Inclusion criteria were chronic heart failure (HF) with New York Heart Association ≥II symptoms and an elevated B-type natriuretic peptide (BNP > 100 pg/mL or N-terminal-pro-BNP > 1000 pg/mL). Patient assessments were performed remotely and included measurements of body weight, blood pressure, heart rate, symptoms, biochemical parameters, and data from cardiac implantable electronic devices when available. In total, 161 patients (71 ± 11 years old, 79% male) were followed for a mean of 291 ± 66 days with a mean adherence to the remote monitoring system of 80 ± 20%. Over this period, 52 (32.3%) patients had 105 WHF events, of which 66 (63%) were successfully managed remotely, the remaining requiring hospitalization. Freedom from WHF events and hospitalization at 300 days were 66% and 85%, respectively (P < 0.001 for the difference). Increased level of BNP was associated with an increased risk of WHF event [hazard ratio (HR) per unit increase in BNP: 1.001; 95% confidence interval (CI) 1-1.002; P = 0.001] and hospitalization (HR 1.002; 95% CI 1.002-1.003; P = 0.002). A decrease in the level of glomerular filtration rate was associated with an increased risk of hospitalization (HR per unit decrease in estimated glomerular filtration rate: 0.946; 95% CI 0.906-0.989; P = 0.014). WHF event recurrence and (re)hospitalization rates at 1-month were similar among patients managed remotely (18% and 12%, respectively) and those requiring hospitalization (21% and 10%, respectively). Iatrogenic complications occurred more often during hospitalization than remote management (26% vs. 3%, P < 0.001)., Conclusions: Our study suggests that remote management of WHF events based on a multiparametric approach led by a telemedical centre is feasible and safe. Adopting such a strategy for patients with chronic HF could reduce HF-related hospitalizations with expected benefits for patients, care providers, and health care systems., (© 2023 The Authors. ESC Heart Failure published by John Wiley & Sons Ltd on behalf of European Society of Cardiology.)

Background: In patients with cardiac resynchronization therapy defibrillators (CRT-Ds), the need for implantable cardioverter-defibrillator (ICD) back-up may be questionable at time of CRT-D replacement (REP) if ICD implant criteria are no longer met due to an improved left ventricular ejection fraction (LVEF) and if no major ventricular arrhythmic event (VAE) occurred during the CRT-D lifetime. The aim of our study was to assess the relevance of ICD back-up and predictors of VAE after REP in primary prevention CRT-D patients., Methods: The prospective, observational, international BioCONTINUE study investigated the rate of patients with at least 1 sustained VAE (sVAE) post-REP and searched for predictive factors of sVAE., Results: Two hundred seventy-six patients (70 ± 10 years, 77% men, mean LVEF 40.6 ± 12.6%) were followed for 28.4 ± 10.2 months. The rate of patients with sVAE was 8.3%, 10.3%, and 21.2% at 1, 2, and 4 years post-REP. Patients without persistent ICD indication at REP still had a sVAE rate of 5.7% (95% CI 2.3-11.5%) at 2 years. In multivariate analysis, predictive factors of subsequent sVAE were (i) persistent ICD indication (hazard ratio (HR) 3.6; 95% CI 1.6-8.3; p = 0.003); (ii) 64-72 years of age as compared to ≥ 79 years (HR 3.7; 95% CI 1.4-9.7; p = 0.008); and (iii) ischemic heart disease (HR 4.4; 95% CI 2.1-9.3; p < 0.0001)., Conclusions: The risk of sVAE (21.2% at 4 years post-REP) depends on age, ischemic heart disease, and ICD indication at the time of REP. A non-trivial risk of sVAE remains in patients without persistent ICD indication., Clinical Trial Registration: NCT02323503., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The degree and pattern of conduction disease seem determinant when assessing potential cardiac resynchronization therapy (CRT) candidates. In the present review, the authors discuss the available noninvasive techniques that can be used to acquire ventricular activation time maps. They describe what body surface mapping has taught us about left bundle branch block, right bundle branch block, intraventricular conduction delay, and right ventricular pacing and discuss the ability of derived parameters of electrical dyssynchrony to predict long-term clinical response to CRT or His bundle pacing., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Initially, left ventricular (LV) endocardial pacing was performed as a bailout procedure after unsuccessful transvenous cardiac resynchronization therapy implantation in the presence of surgical contraindications. Additional possible advantages of endocardial LV pacing are a more physiologic activation, being less arrhythmogenic, more effective on the hemodynamic level, with better thresholds, and without the risk of phrenic stimulation. Different techniques have been proposed to stimulate the LV endocardium in humans, with feasibility and safety studies involving limited numbers of patients. In this review, we will describe the different techniques proposed to allow LV endocardial pacing, the results observed, and then we will discuss the reasons why LV endocardial pacing seems to be out of fashion today and what are the possible perspectives for development., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: Possible mechanisms of left-axis deviation (LAD) in the setting of left bundle branch block (LBBB) include differences in cardiac electrophysiology, structure, or anatomic axis., Objective: The purpose of this study was to clarify the mechanism(s) responsible for LAD in patients with LBBB., Methods: Twenty-nine patients with nonischemic cardiomyopathies and LBBB underwent noninvasive electrocardiographic imaging (ECGi), cardiac computed tomography, and magnetic resonance imaging in order to define ventricular electrical activation, characterize cardiac structure, and determine the cardiac anatomic axis., Results: Sixteen patients had a normal QRS axis (NA) (mean axis 8° ± 23°), whereas 13 patients had LAD (mean axis -48° ± 13°; P <.001). Total activation times were longer in the LAD group (112 ± 25 ms vs 91 ± 14 ms; P = .01) due to delayed activation of the basal anterolateral region (107 ± 10 ms vs 81 ± 17 ms; P <.001). Left ventricular (LV) activation in patients with LAD was from apex to base, in contrast to a circumferential pattern of activation in patients with NA. Apex-to-base delay was longer in the LA group (95 ± 13 ms vs 64 ± 21 ms; P <.001) and correlated with QRS frontal axis (R 2 = 0.67; P <.001). Both groups were comparable with regard to LV end-diastolic volume (295 ± 84 mL vs LAD 310 ± 91 mL; P = .69), LV mass (177 ± 33 g vs LAD 180 ± 37 g; P = .83), and anatomic axis., Conclusion: LAD in LBBB appears to be due to electrophysiological abnormalities rather than structural factors or cardiac anatomic axis., (Copyright © 2021 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Introduction: We investigated whether pacing-induced electrical dyssynchrony at the time of cardiac resynchronization therapy (CRT) device implantation was associated with chronic CRT response., Methods and Results: We included a total of 69 consecutive heart failure patients who received a CRT device. Left (LVp-RVs) and right (RVp-LVs) pacing-induced interlead delays were measured intraoperatively and used to determine if there was paced left ventricular (LV) dyssynchrony, defined as present when LVp-RVs is larger than RVp-LVs. CRT response was defined as a reduction in LV end-systolic volume ≥15%, 6 months after implantation. Paced left ventricular dyssynchrony (PLVD) was associated with ischemic cardiomyopathy (ICM) (χ 2 : 8; P = .005) but not with QRS morphology nor with pacing lead positions. In a univariate analysis, PLVD (odds ratio [OR], 6.53; 95% confidence interval [CI], 2.2-18.9; P = .001), atypical left bundle branch block (LBBB) (OR, 3.3; 95% CI, 1.2-9.4; P = .022), and ICM (OR, 5.2; 95% CI, 1.6-17; P = .006) were associated with nonresponse. In a multivariate analysis, both PLVD (OR, 9.74; 95% CI, 2.8-33.9; P < .0001) and atypical LBBB (OR, 5.6; 95% CI, 1.5-20.3; P = .009) were independently associated with nonresponse. Adding PLVD to a model based on QRS morphology provided a significant and meaningful incremental value to predict LV reverse remodeling after CRT (χ 2 to enter: 8; P < .005). Computer simulations corroborate these findings by showing that, while intrinsic electrical dyssynchrony is a prerequisite, the level of pacing-induced dyssynchrony modulates acute CRT response., Conclusion: In addition to the intrinsic electrical substrate, PLVD is strongly associated with less LV reverse remodeling, demonstrating that measuring the electrical substrate during pacing has additional value for prediction of CRT response in an already well-selected patient population., (© 2020 Wiley Periodicals, Inc.)

Introduction: Some cardiac resynchronization therapy (CRT) device manufacturers (Biotronik, Germany; Boston Scientific, United States) have implemented left ventricular (LV) sensing functionality to prevent pacing into the vulnerable phase. Physicians are only partially aware of programming pitfalls related to LV sensing and general programming advice is lacking., Methods and Results: We provide an illustrative case-series-based review of the variety of potential problems with LV sensing. LV sensing may inappropriately impair CRT delivery due to LV-sensing issues or improper device programming. This can cause beat-wise loss of resynchronization but also ongoing desynchronization. On the other hand, LV sensing provides additional diagnostic information, which may reveal intermittent problems of the LV lead such as capture loss. We summarize the available evidence to provide manufacturer-specific recommendations on device programming and troubleshooting for daily clinical practice., Conclusion: CRT devices with LV sensing may suffer from impaired resynchronization due to programming pitfalls. If LV sensing is active (nominal setting in Biotronik and Boston Scientific devices), careful lookout for related problems and resynchronization percentage is required. Optimization is mandatory and even deactivation of LV sensing may have to be considered., (© 2019 Wiley Periodicals, Inc.)

Cardiac fibrosis is associated with heart failure and poor prognosis. Fibrosis biomarkers have been poorly evaluated as a tool to predict cardiac resynchronization therapy (CRT) response generating conflicting results. The present study assessed the predictive value of cardiac fibrosis biomarkers on CRT response. Patients underwent clinical examination, echocardiography and blood fibrosis biomarker evaluation prior to CRT implantation. At six months, a positive response to CRT was defined by a composite endpoint of no death or hospitalization for heart failure, and presence of left ventricular (LV) reverse remodeling (decrease in LV end-systolic volume ≥15%). Sixty patients were included in a multicenter study. At 6 months, 38 were positive responders to CRT and reached the response criteria (63%). Compared to non-responders, CRT responders displayed lower concentration levels of the fibrosis biomarkers procollagen type I C-terminal propeptide [PICP 135[99-166] ng/ml vs. 179[142-226]ng/ml, p = 0.001)] and procollagen type III N-terminal propeptide [PIIINP 5.50[3.66-8.96] ng/ml vs. 8.01[5.01-11.86]ng/ml, p = 0.014)] at baseline. In multivariate analysis, a PICP ≤ 163 ng/ml was associated with a positive CRT response [OR = 7.8(1.3-46.7), p = 0.023] independently of the presence of LBBB, QRS duration, LV lead position or non-ischemic cardiomyopathy. Altogether, the present findings show that a lower degree of cardiac fibrosis is associated with a positive response after CRT implantation. PICP evaluation before CRT implantation could help improve patient selection.

Cardiac resynchronization therapy (CRT) is an effective intervention in selected patients with moderate-to-severe heart failure with reduced ejection fraction and abnormal left ventricular activation time. The non-response rate of approximately 30% has remained nearly unchanged since this therapy was introduced 25 years ago. While intracardiac mapping is widely used for diagnosis and guidance of therapy in patients with tachyarrhythmia, its application in characterization of the electrical substrate to elucidate the mechanisms involved in CRT response remain anecdotal. In the present review, we describe the traditional determinants of CRT response before presenting novel non-invasive techniques used for CRT optimization. We discuss efforts to identify the target electrical substrate to guide the deployment of pacing electrodes during the operative procedure. Non-invasive body surface mapping technologies such as ECG imaging or ECG belt enables prediction of acute and chronic CRT response. While electrical dyssynchrony parameters provide high predictive accuracy for CRT response when obtained during intrinsic conduction, their predictive value is less when acquired during CRT or LV-pacing. Key messages Classic predictors of CRT response are female gender, NYHA class ≤ III, left ventricular ejection fraction ≥25%, QRS duration ≥150 ms and estimated glomerular filtration rate ≥60 mL/min. ECG-imaging is a comprehensive non-invasive mapping system which allows to express the amount of electrical asynchrony of a CRT candidate. Non-invasive body surface mapping technologies enables excellent prediction of acute and chronic CRT response before implantation. When performed during CRT or LV-pacing, the added value of these mapping systems remains unclear.

Background: Electrocardiographic mapping (ECM) expresses electrical substrate through magnitude and direction of the activation delay vector (ADV). We investigated to what extent the response to cardiac resynchronization therapy (CRT) is determined by baseline ADV and by ADV modification through CRT and optimization of left ventricular (LV) pacing site., Methods: ECM was performed in 79 heart failure patients (4 RBBB, 12 QRS < 120 ms, 23 non-specific conduction delay [NICD] and 40 left bundle branch block [LBBB]). 67 patients (QRS ≥ 120 ms) underwent CRT implantation and in 26 patients multiple LV pacing site optimization was performed. ADV was calculated from locations/depolarization times of 2000 virtual epicardial electrodes derived from ECM. Acute response was defined as ≥10% LVdP/dt max increase, chronic response by composite clinical score at 6 months., Results: During intrinsic conduction, ADV direction was similar in patients with QRS < 120 ms, NICD and LBBB, pointing towards the LV free wall, while ADV magnitude was larger in LBBB (117 ± 25 ms) than in NICD (70 ± 29 ms, P < 0.05) and QRS < 120 ms (52 ± 14 ms, P < 0.05). Intrinsic ADV accurately predicted the acute (AUC = 0.93) and chronic (AUC = 0.90) response to CRT. ADV change by CRT only moderately predicted response (highest AUC = 0.76). LV pacing site optimization had limited effects: +3 ± 4% LVdP/dt max when compared to conventional basolateral LV pacing., Conclusion: The baseline electrical substrate, adequately measured by ADV amplitude, strongly determines acute and chronic CRT response, while the extent of its modification by conventional CRT or by varying LV pacing sites has limited effects., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: The predictive value of interventricular versus intraventricular dyssynchrony for response to cardiac resynchronization therapy (CRT) remains unclear. We investigated the relative importance of both ventricular electrical substrate components for left ventricular (LV) hemodynamic function., Methods and Results: First, we used the cardiovascular computational model CircAdapt to characterize the isolated effect of intrinsic interventricular and intraventricular activation on CRT response (ΔLVdP/dt max ). Simulated ΔLVdP/dt max (range: 1.3%-26.5%) increased considerably with increasing interventricular dyssynchrony. In contrast, the isolated effect of intraventricular dyssynchrony in either the LV or right ventricle was limited (ΔLVdP/dt max range: 12.3%-18.3% and 14.1%-15.7%, respectively). Effects of activation during biventricular pacing on ΔLVdP/dt max were small. Second, electrocardiographic imaging-derived activation characteristics of 51 CRT candidates were used to personalize ventricular activation in CircAdapt. The individualized models were subsequently used to assess the accuracy of ΔLVdP/dt max prediction based on the electrical data. The model-predicted ΔLVdP/dt max was close to the actual value in patients with left bundle branch block (measured-simulated: 2.7±9.0%) when only intrinsic interventricular dyssynchrony was personalized. Among patients without left bundle branch block, ΔLVdP/dt max was systematically overpredicted by CircAdapt (measured-simulated: 9.2±7.1%). Adding intraventricular activation to the model did not improve the accuracy of the response prediction., Conclusions: Computer simulations revealed that intrinsic interventricular dyssynchrony is the dominant component of the electrical substrate driving the response to CRT. Intrinsic intraventricular dyssynchrony and any dyssynchrony during biventricular pacing play a minor role in this respect. This may facilitate patient-specific modeling for prediction of CRT response., Clinical Trial Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01270646., (© 2018 American Heart Association, Inc.)

Prognosis of heart failure with reduced ejection fraction (HFrEF) is improved by drug optimization according to guidelines; however, little is known regarding such optimization in HFrEF patients with an implantable cardioverter defibrillator (ICD) or cardiac resynchronization therapy (CRT). This study aimed to describe implementation of this optimized strategy and its impact in patients implanted with an ICD/CRT. Using a 1/97th representative sample of the French national health-care insurance system claims database, a retrospective cohort study was conducted including HFrEF patients implanted with ICD or CRT between January 2009 and December 2014. HFrEF treatments were analyzed before and after ICD/CRT implantation. Heart failure (HF) hospitalization and survival were examined at 1, 3, and 5 years: 378 patients (135 CRT, 243 ICD) with a mean age of 68 ± 13 years were included. Mean follow-up was 23 months [11-42]. At baseline, 36% of patients had no or only 1 HFrEF drug among β-blockers, angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, and mineralocorticoid receptor antagonists, whereas 26% of patients received an optimal treatment (all 3 classes). At 3 months after ICD/CRT implantation, the prescription rate of HFrEF drugs was higher than baseline but returned to preimplantation levels at the end of follow-up. HF hospitalization rate was higher in the nonoptimized patient group (28% vs 14%, p = 0.001). Optimal HFrEF treatment was associated with better survival (hazard ratio = 0.59 [0.4-0.86], p = 0.006). In conclusion, HFrEF drugs are underprescribed before and after ICD/CRT implantation despite the demonstration that HFrEF drug optimization also reduces death and HF hospitalization in this population., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: In contrast to patients with left bundle branch block (LBBB), heart failure patients with narrow QRS and nonspecific intraventricular conduction delay (NICD) display a relatively limited response to cardiac resynchronization therapy. We sought to compare left ventricular (LV) activation patterns in heart failure patients with narrow QRS and NICD to patients with LBBB using high-density electroanatomic activation maps., Methods and Results: Fifty-two heart failure patients (narrow QRS [n=18], LBBB [n=11], NICD [n=23]) underwent 3-dimensional electroanatomic mapping with a high density of mapping points (387±349 LV). Adjunctive scar imaging was available in 37 (71%) patients and was analyzed in relation to activation maps. LBBB patients typically demonstrated (1) a single LV breakthrough at the septum (38±15 ms post-QRS onset); (2) prolonged right-to-left transseptal activation with absence of direct LV Purkinje activity; (3) homogeneous propagation within the LV cavity; and (4) latest activation at the basal lateral LV. In comparison, both NICD and narrow QRS patients demonstrated (1) multiple LV breakthroughs along the posterior or anterior fascicles: narrow QRS versus LBBB, 5±2 versus 1±1; P =0.0004; NICD versus LBBB, 4±2 versus 1±1; P =0.001); (2) evidence of early/pre-QRS LV electrograms with Purkinje potentials; (3) rapid propagation in narrow QRS patients and more heterogeneous propagation in NICD patients; and (4) presence of limited areas of late activation associated with LV scar with high interindividual heterogeneity., Conclusions: In contrast to LBBB patients, narrow QRS and NICD patients are characterized by distinct mechanisms of LV activation, which may predict poor response to cardiac resynchronization therapy., (© 2017 American Heart Association, Inc.)

Remote monitoring (RM) receives a Class I: Level of Evidence: A recommendation for the follow-up of patients with implantable cardioverter-defibrillators, positioning the technology as standard of care. RM is often seen and sold as a plug-and-play technology, whereas fundamental differences exist in the philosophy and conception of the 5 main RM systems. The capabilities and limitations of the different RM systems need to be understood and taken into account when the decision is made to remotely manage an individual patient. The purpose of this review is to provide to the cardiologist practical information about RM systems' specificities with respect to the different technical and clinical alerts. Clinically based indications and programming suggestions are provided., (Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Aims: Left ventricular (LV) lead implantation through the coronary sinus (CS) can be limited and sometimes not possible-alternative approaches are needed. Minimally invasive, robotically guided LV lead implantation has major advantages, but there are little published data about the short- and long-term follow-ups, in terms of feasibility, safety, electrical performance, and impact on clinical outcome., Methods and Results: A total of 21 heart failure patients underwent robotically guided LV lead implantation using the Da Vinci Robotic System. Indications were failed implant with conventional approach through the CS (n = 16) and non-response to conventional cardiac resynchronization therapy (n = 5). During the procedure, the entire LV free wall was exposed through 3 transthoracic ports (10 mm diameter each) allowing ample choice of stimulation site and the ability to implant 2 LV leads via a Y connector. Patients were prospectively followed up for 1 year. The two LV leads were successfully implanted in all patients. No peri-procedural complications were observed. After a mean stay in the intensive care unit of 1.2 ± 4 days, the 21 patients were hospitalized in the EP department for 6.7 ± 2.9 days. Acute LV thresholds were excellent (1.0 V ± 0.6/0.4 ms) and stayed stable at 1-year follow-up (1.5 V ± 0.6/0.4 ms, P = 0.21). Four patients demonstrated an increased threshold (>2 V/0.4 ms). There was no phrenic nerve stimulation. After 12 months, in the failed implant group, 69% of the patients were echocardiographic and clinical responders., Conclusion: The robotic approach was feasible, safe, and minimally invasive. Accordingly, robotically guided LV lead implantation seems to offer a new alternative when conventional approaches are not suitable., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2016. For permissions please email: journals.permissions@oup.com.)

Introduction: Cardiac resynchronisation therapy (CRT) was initially developed to treat patients with left bundle branch block (LBBB). However, many patients with heart failure have a widened QRS but neither left-BBB nor right-BBB; this is called non-specific intraventricular conduction delay (NICD). It is unclear whether CRT is effective in this subgroup of patients., Methods and Analysis: The NICD-CRT study is a prospective, double-blind, randomised (1:1), parallel-arm, multicentre trial comparing the effects of CRT in patients with heart failure, a reduced left ventricular ejection fraction (LVEF <35%) and NICD, who have been implanted with a device (CRT-pacemaker or CRT-defibrillator) that has or has not been activated. Enrolment began on 15 July 2015 and should finish within 3 years; 40 patients have already been randomised and 11 centres have agreed to participate. The primary end point is the comparison of the proportion of patients improved, unchanged or worsened over the subsequent 12 months. 100 patients per group are required to demonstrate a difference between groups with a statistical power of 90%, a type I error of 0.05% (two-sided) and a loss to follow-up of 10%. This trial will add substantially to the modest amount of existing data on CRT in patients with NICD and should reduce uncertainty for guidelines and clinical practice when added to the pool of current information., Ethics and Dissemination: Local ethics committee authorisations have been obtained since May 2015. We will publish findings from this study in a peer-reviewed scientific journal and present results at national and international conferences., Trial Registration Number: NCT02454439; pre-results., Competing Interests: Conflicts of Interest: None declared., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.)

Background: Biventricular pacing (BVP) may not achieve complete electrical resynchronization., Objective: The purpose of this study was to assess whether the resynchronizing effect of BVP varies among patients depending on the underlying electrical substrate., Methods: High-resolution electrocardiographic mapping with invasive measurement of the maximal rate of systolic left ventricular (LV) pressure rise (LVdP/dtmax) was performed during baseline activation and during BVP in 61 patients with heart failure with various conduction delays: 13 with narrow QRS duration (<120 ms), 22 with nonspecific intraventricular conduction disturbance, and 26 with left bundle branch block. Electrical dyssynchrony, both during baseline activation and BVP, was quantified by total and LV activation times (TAT and LVTAT) and by ventricular electrical uncoupling (VEU = mean LVTAT - mean right ventricular activation time). Response to BVP was defined as a ≥10% increase in LVdP/dtmax., Results: The electrical activation pattern during BVP was similar for all patient groups and, hence, not dependent on baseline conduction disturbance. During BVP, TAT, LVTAT, and VEU were similar for all groups and were either not correlated or weakly correlated with the change in LVdP/dtmax. In contrast, changes in electrical dyssynchrony correlated significantly with the change in LVdP/dtmax: r=0.71, 0.69, and 0.69 for ∆TAT, ∆LVTAT, and ∆VEU, respectively (all P < .001). Responders showed higher baseline dyssynchrony levels and BVP-induced dyssynchrony reduction than did nonresponders (all P < .001); in nonresponders, BVP worsened activation times than did baseline activation., Conclusion: BVP does not eliminate electrical dyssynchrony, but rather brings it to a common level independent of the patient's underlying electrical substrate. Therefore, BVP is of benefit to patients with dyssynchrony but not to patients with insufficient electrical dyssynchrony in whom it induces an iatrogenic electropathy., (Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Causes for diverse effects of cardiac resynchronization therapy (CRT) are poorly understood. Because CRT is an electrical therapy, it may be best understood by detailed characterization of electrical substrate and its interaction with pacing. Electrocardiogram (ECG) features affect CRT outcomes. However, the surface ECG reports rudimentary electrical data. In contrast, noninvasive electrocardiographic imaging provides high-resolution single-beat ventricular mapping. Several complex characteristics of electrical substrate, not decipherable from the 12-lead ECG, are linked to CRT effect. CRT response may be improved by candidate selection and left ventricular lead placement directed by more precise electrical evaluation, on an individual patient basis., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Aims: It is unclear how the position of the left ventricular (LV) lead relative to a scar affects the haemodynamic response in patients with dyssynchronous heart failure receiving cardiac resynchronization therapy. We investigated this complex interaction using a computational model., Methods and Results: The CircAdapt computational cardiovascular system model was used to simulate heart failure with left bundle branch block (LBBB). Myocardial scar was induced in four different regions of the LV free wall (LVFW). We then simulated biventricular pacing (BVP) in each heart, in which LV lead position was varied. The LV lead position leading to maximal acute change in LV stroke volume (SV) was defined as optimal lead position. In LBBB without scar, SV increase was maximal when pacing the LVFW region most distant from the septum. With a scar adjacent to the septum, maximal response was achieved when pacing remote from both the septum and the scar. When the scar was located further from the septum, the BVP-induced increase of SV was small. For all hearts, pacing from the optimal LV lead position resulted in the most homogeneous distribution of local ventricular myofibre work and the largest increase in summed left and right ventricular pump work., Conclusions: These computer simulations suggest that, in hearts with LBBB and scar, the optimal LV lead position is a compromise between a position distant from the scar and from the septum. In infarcted hearts, the best haemodynamic effect is achieved when electromechanical resynchronization of the remaining viable myocardium is most effective., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2014. For permissions please email: journals.permissions@oup.com.)

Introduction: Recent studies have demonstrated that left ventricular (LV) pacing site is a critical parameter in optimizing cardiac resynchronization therapy (CRT). The present study evaluates the effect of pacing from different LV locations on QRS duration (QRSd) and their relationship to acute hemodynamic response in congestive heart failure patients., Methods and Results: Thirty-five patients with nonischemic dilated cardiomyopathy and left bundle branch block referred for CRT device implantation were studied. Eleven predetermined LV pacing sites were systematically assessed in random order: epicardial: coronary sinus (CS); endocardial: basal and mid-cavity (septal, anterior, lateral, and inferior), apex, and the endocardial site facing the CS pacing site. For each patient QRSd and +dP/dtmax during baseline (AAI) and DDD LV pacing at 2 atrioventricular delays were compared. Response to CRT was significantly better in patients with wider baseline QRSd (≥150 milliseconds). Hemodynamic response was inversely correlated to increase of QRSd during LV pacing (short atrioventricular [AV] delay: r = 0.44, P < 0.001; long AV delay: r = 0.59, P < 0.001). Compared to baseline, LV pacing at the site of shortest QRSd significantly improved +dP/dtmax (+18 ± 25%, P < 0.001) but was not superior to other conventional strategy (lateral wall, CS pacing, and echo-guided) and was inferior to a hemodynamically guided strategy., Conclusions: In our study, we have demonstrated that changes of QRSd during LV pacing correlated with acute hemodynamic response and that LV pacing location was a primary determinant of paced QRSd. Although QRSd did not predict the maximum hemodynamic response, our results confirm the link between electrical activation and hemodynamic response of the LV during CRT., (© 2014 Wiley Periodicals, Inc.)

Objectives: The purpose of this study was to enhance understanding of the working mechanism of cardiac resynchronization therapy by comparing animal experimental, clinical, and computational data on the hemodynamic and electromechanical consequences of left ventricular pacing (LVP) and biventricular pacing (BiVP)., Background: It is unclear why LVP and BiVP have comparative positive effects on hemodynamic function of patients with dyssynchronous heart failure., Methods: Hemodynamic response to LVP and BiVP (% change in maximal rate of left ventricular pressure rise [LVdP/dtmax]) was measured in 6 dogs and 24 patients with heart failure and left bundle branch block followed by computer simulations of local myofiber mechanics during LVP and BiVP in the failing heart with left bundle branch block. Pacing-induced changes of electrical activation were measured in dogs using contact mapping and in patients using a noninvasive multielectrode electrocardiographic mapping technique., Results: LVP and BiVP similarly increased LVdP/dtmax in dogs and in patients, but only BiVP significantly decreased electrical dyssynchrony. In the simulations, LVP and BiVP increased total ventricular myofiber work to the same extent. While the LVP-induced increase was entirely due to enhanced right ventricular (RV) myofiber work, the BiVP-induced increase was due to enhanced myofiber work of both the left ventricle (LV) and RV. Overall, LVdP/dtmax correlated better with total ventricular myofiber work than with LV or RV myofiber work alone., Conclusions: Animal experimental, clinical, and computational data support the similarity of hemodynamic response to LVP and BiVP, despite differences in electrical dyssynchrony. The simulations provide the novel insight that, through ventricular interaction, the RV myocardium importantly contributes to the improvement in LV pump function induced by cardiac resynchronization therapy., (Copyright © 2013 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Reproducibility and hemodynamic efficacy of optimization of AV delay (AVD) of cardiac resynchronization therapy (CRT) using invasive LV dp/dtmax are unknown., Method and Results: 25 patients underwent AV delay (AVD) optimisation twice, using continuous left ventricular (LV) dp/dtmax, systolic blood pressure (SBP) and pulse pressure (PP). We compared 4 protocols for comparing dp/dtmax between AV delays: We assessed for dp/dtmax, LVSBP and LVPP, test-retest reproducibility of the optimum. Optimization using immediate absolute dp/dtmax had poor reproducibility (SDD of replicate optima=41 ms; R(2)=0.45) as did delayed absolute (SDD 39 ms; R(2)=0.50). Multiple relative had better reproducibility: SDD 23 ms, R(2)=0.76, and (p<0.01 by F test). Compared with AAI pacing, the hemodynamic increment from CRT, with the nominal AV delay was LVSBP 2% and LVdp/dtmax 5%, while CRT with pre-determined optimal AVD gave 6% and 9% respectively., Conclusions: Because of inevitable background fluctuations, optimization by absolute dp/dtmax has poor same-day reproducibility, unsuitable for clinical or research purposes. Reproducibility is improved by comparing to a reference AVD and making multiple consecutive measurements. More than 6 measurements would be required for even more precise optimization--and might be advisable for future study designs. With optimal AVD, instead of nominal, the hemodynamic increment of CRT is approximately doubled., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Objectives: This study sought to investigate whether noninvasive electrocardiographic activation mapping is a useful method for predicting response to cardiac resynchronization therapy (CRT)., Background: One third of the patients appear not to respond to CRT when they are selected according to QRS duration., Methods: We performed electrocardiographic activation mapping in 33 consecutive CRT candidates (QRS duration ≥120 ms). In 18 patients, the 12-lead electrocardiographic morphology was left bundle branch block (LBBB), and in 15, it was nonspecific intraventricular conduction disturbance (NICD). Three indexes of electrical dyssynchrony were derived from intrinsic maps: right and left ventricular total activation times and ventricular electrical uncoupling (VEU) (difference between the left ventricular [LV] and right ventricular mean activation times). We assessed the ability of these parameters to predict response, measured using a clinical composite score, after 6 months of CRT., Results: Electrocardiographic maps revealed homogeneous patterns of activation and consistently greater VEU and LV total activation time (LVTAT) in patients with LBBB compared with heterogeneous activation sequences and shorter VEU and LVTAT in NICD patients (VEU: 75 ± 12 ms vs. 40 ± 22 ms; p < 0.001; LVTAT: 115 ± 21 ms vs. 91 ± 34 ms; p = 0.03). LBBB and NICD patients had similar right ventricular total activation times (62 ± 30 ms vs. 58 ± 26 ms; p = 0.7). The area under the receiver-operating characteristic curve indicated that VEU (area under the curve [AUC]: 0.88) was significantly superior to QRS duration (AUC: 0.73) and LVTAT (AUC: 0.72) for predicting CRT response (p < 0.05). With a 50-ms cutoff value, VEU identified CRT responders with 90% sensitivity and 82% specificity whether LBBB was present or not., Conclusions: Ventricular electrical uncoupling measured by electrocardiographic mapping predicted clinical CRT response better than QRS duration or the presence of LBBB., (Copyright © 2013 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Introduction: Response rate after cardiac resynchronization therapy (CRT) remains suboptimal. We sought to identify pre- and intraprocedural predictors of response using MRI., Methods and Results: Sixty patients underwent MRI before CRT. Left ventricular (LV) volumes and ejection fraction were assessed on cine images. Intra-LV dyssynchrony was defined as the maximal delay between first peaks of radial wall motion over 20 segments. Myocardial scar extent was quantified using delayed-enhanced MRI. After CRT, the paced LV segment was characterized on preprocedural MRI with respect to presence of scar and mechanical delay, the latter being quantified using time to first peak of wall motion, expressed in percentage of the total LV activation. Echocardiography was performed before and 6 months after CRT to quantify reverse remodeling (RR). Mean RR at 6 months was 30 ± 29% of baseline LV end-systolic volume. At univariate analysis, RR related to baseline LV end-diastolic and end-systolic volumes (R(2) = 0.101, P = 0.01; R(2) = 0.072, P = 0.04), intra-LV mechanical dyssynchrony (R(2) = 0.351, P < 0.0001), scar extent (R(2) = 0.273, P < 0.0001), and presence of scar at pacing site (R(2) = 0.100, P = 0.01). QRS duration and mechanical delay at pacing site were not found related to RR (R(2) = 0.041, P = 0.12 and R(2) = 0.012, P = 0.4, respectively). At multivariate analysis intra-LV mechanical dyssynchrony, scar extent, and LV end-diastolic volume were independent predictors of RR (R(2) = 0.307, P = 0.001; R(2) = 0.096, P = 0.002, R(2) = 0.078, P = 0.005, respectively)., Conclusion: Intra-LV dyssynchrony and scar extent are independent predictors of RR after CRT. Scar at pacing site is associated to a lesser response to CRT. Mechanical delay at this site has no impact on the response., (© 2013 Wiley Periodicals, Inc.)

Cardiac resynchronization therapy (CRT) is a proven treatment for heart failure and requires the implantation of a left ventricular (LV) lead, usually placed in a tributary of the coronary sinus. Encouraged by the fact that approximately 30 % of the patients receiving CRT do not benefit from this therapy, LV endocardial pacing has been proposed as an alternative to traditional LV transvenous epicardial pacing. Endocardial LV pacing has a number of potential advantages over conventional LV epicardial pacing, including a more physiological endocardial-to-epicardial transmural activation sequence, a faster ventricular activation, a larger choice of stimulation sites and a potential superior hemodynamic performance. On the other hand, cardiologists will have to deal with new implant techniques' (transseptal), higher risk of thromboembolic events, and challenging extraction procedures of infected material. The future of endocardial stimulation will depend on the results of randomized studies adequately powered to assess the feasibility, the safety and the effectiveness of this new pacing strategy.

Background: The efficacy of biventricular (BiV) pacing in patients with a narrow or moderately prolonged QRS duration remains questionable., Objective: To assess the hypothesis that electrical dyssynchrony is required to obtain hemodynamic benefit from BiV pacing by investigating the relationship between intrinsic QRS duration and hemodynamic response to BiV pacing in a patient population covering a broad spectrum of QRS duration., Methods: Eighty-two consecutive heart failure patients underwent cardiac resynchronization therapy implantation irrespective of their QRS duration. Thirty-four patients had a narrow QRS duration (<120 ms), whereas 11 patients had a moderately prolonged QRS duration (≥120 to <150 ms) and 37 patients had a severely prolonged QRS duration (≥150 ms). After implantation, invasive left ventricular (LV) dP/dt measurements were compared between intrinsic rhythm and simultaneous BiV pacing with an optimized atrioventricular delay., Results: A high correlation (r = .65; P < .001) was observed between baseline QRS duration and changes in LV dP/dt(max) induced by BiV pacing. BiV pacing was ineffective in patients with a narrow QRS duration (+0.4% ± 6.1%; P = ns). No significant increase in LV dP/dt(max) was observed in patients with a QRS duration of ≥120 to <150 ms (+4.4% ± 6.9%; P = .06), whereas patients with a QRS duration of ≥150 ms exhibited a significant increase in LV dP/dt(max) (+17.1% ± 13.4%; P <.001). Only 9% of the patients with a narrow QRS duration exhibited a ≥10% increase in LV dP/dt(max)., Conclusions: Baseline QRS duration is linearly related to acute hemodynamic response to BiV pacing. Patients with a narrow QRS duration do not derive hemodynamic improvement. This improvement is also limited in patients with a moderately prolonged QRS duration, raising questions about the potential clinical benefit of this therapy in these patients., (Copyright © 2012 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: The relationship between depression and heart failure is neither coincidental nor trivial, since depression is a powerful predictor of re-hospitalization and mortality. We prospectively studied the prevalence and impact of depression on the clinical outcomes of patients attending for cardiac resynchronization therapy (CRT). We specifically examined whether patients with depression have a different rate of response to CRT and whether CRT has an effect on depressive symptoms., Methods: Sixty-eight recipients of CRT systems were included. The depressive status was evaluated before implant and after 6 months by a structured diagnostic interview measuring Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria of major depression and by a self-report questionnaire (Center for Epidemiological Studies Depression Scale, CES-D). The CRT response was assessed at 6 months by a clinical composite score., Results: At inclusion, DSM-IV criteria of major depression were identified in 41% of the population, while using the self-report questionnaire 65% were observed to have mild to major depressive symptoms (CES-D ≥ 16). Only 4 patients were taking antidepressants. At 6 months, 75% were considered responders to CRT. Response to CRT did not differ between those with and without depression at baseline. The rate of patients with depression at 6 months was significantly lower in responders to CRT compared with nonresponders., Conclusions: We found a high prevalence of depressive symptoms in patients receiving CRT systems. Patients with depression should not be excluded from CRT, because they demonstrate a similar rate of response than the persons without depression and the responders are less likely to be depressed at 6 months., (© 2012 Wiley Periodicals, Inc.)

Cardiac resynchronization therapy (CRT) is an established treatment for patients with moderate-to-severe heart failure and a wide QRS complex. However, the amount of reverse remodeling and clinical improvement is highly variable and poorly predictable. The left ventricular pacing site is of critical importance for the CRT response but is often imposed by the coronary sinus anatomical constraints and may result in suboptimal resynchronization. Alternative pacing sites, such as endocardial LV pacing or multisite pacing, have been proposed to improve CRT response rates and may be considered in nonresponders to standard resynchronization. However, adequately powered randomized studies are required to determine whether these pacing strategies result in improved outcome.

Cardiac resynchronization therapy (CRT) is an established treatment for selected heart failure patients with conduction disease. Many studies aimed at quantifying mechanical dyssynchrony in CRT candidates when it became apparent that 30-50% of CRT recipients showed no improvement after implantation. As these, often echocardiography-based, measurements have not yet succeeded in estimating the mechanical substrate in an accurate and reproducible manner, interest in electrical substrate has renewed. In this review, current knowledge concerning electrical substrate in CRT candidates will be explored and applied to current CRT practice, highlighting why the electrical substrate is both essential and sufficient for successful CRT. Finally, novel ways to better measure and treat the electrical substrate are discussed.

Biventricular resynchronization, a therapy recommended for patients presenting with left ventricular (LV) dysfunction and ventricular dyssynchrony, requires the implantation of an LV lead, usually placed in a lateral or posterolateral tributary of the coronary sinus. Despite important progress made in the development of dedicated instrumentation, the procedure remains sometimes challenging and unsuccessful in a minority of patients. In the rare instances of unsuccessful transvenous implantations occurring in the presence of major surgical contraindications, a few operators have implanted the LV lead transseptally, an approach limited by technical difficulties and by the thromboembolic risk associated with the presence of a lead inside the LV cavity. The interest in this approach was recently renewed by 2 studies in an animal model and in humans, respectively, which both found a distinctly superior hemodynamic performance associated with endocardial compared with epicardial stimulation. This review discusses the advantages and disadvantages of LV endocardial stimulation, examines the various techniques of LV endocardial stimulation, and projects their future applications in light of these highly promising recent results. The implementation of endocardial stimulation will ultimately depend on: 1) the development of safe, effective, and durable instrumentation, and reliable and reproducible intraprocedural methods to identify the optimal site of stimulation; and 2) the completion of controlled trials confirming the superiority of this technique compared with standard cardiac resynchronization therapy., (Copyright (c) 2010 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: We sought to evaluate the impact of the left ventricular (LV) pacing site on hemodynamic response to cardiac resynchronization therapy (CRT)., Background: CRT reduces morbidity and mortality in heart failure patients. However, 20% to 40% of eligible patients may not fully benefit from CRT device implantation. We hypothesized that selecting the optimal LV pacing site could be critical in this issue., Methods: Thirty-five patients with nonischemic dilated cardiomyopathy referred for CRT device implantation were studied. Intraventricular dyssynchrony and latest activated LV wall were defined by tissue Doppler imaging analysis before the study. Eleven predetermined LV pacing sites were systematically assessed in random order: basal and mid-cavity (septal, anterior, lateral, inferior), apex, coronary sinus (CS), and the endocardial site facing the CS pacing site. For each patient, +dP/dT(max), -dP/dT(min), pulse pressure, and end-systolic pressure during baseline (AAI) and DDD LV pacing were compared. Two atrioventricular delays were tested., Results: Major interindividual and intraindividual variations of hemodynamic response depending on the LV pacing site were observed. Compared with baseline, LV DDD pacing at the best LV position significantly improved +dP/dT(max) (+31 +/- 26%, p < 0.001) and was superior to pacing the CS (+15 +/- 23%, p < 0.001), the lateral LV wall (+18 +/- 22%, p < 0.001), or the latest activated LV wall (+11 +/- 17%, p < 0.001)., Conclusions: The pacing site is a primary determinant of the hemodynamic response to LV pacing in patients with nonischemic dilated cardiomyopathy. Pacing at the best LV site is associated acutely with fewer nonresponders and twice the improvement in +dP/dT(max) observed with CS pacing., (Copyright 2010 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: The choice of the optimal left ventricular (LV) pacing site remains an issue in patients requiring cardiac resynchronization therapy (CRT)., Aim: This prospective study compared the outcome of patients paced at the most delayed LV region with that of patients paced at any other LV site., Methods: Forty-four patients with severe heart failure underwent three-dimensional (3D) echocardiography before implantation and 3 days after implantation of a CRT device, to determine the most delayed LV region during spontaneous rhythm and during right ventricular pacing. The patients were divided subsequently into four groups: group 1 (n=19), LV lead placed at the most delayed echocardiographic site in spontaneous rhythm; group 2 (n=25), LV lead placed at any other site; group 3 (n=21), LV lead placed at the most delayed echocardiographic site during right ventricular pacing; group 4 (n=23), LV lead placed at any other site., Results: No significant differences were observed between the four groups before implantation. After 6 months of CRT, no significant differences were observed between groups 1 and 2 or between groups 3 and 4 in terms of change in New York Heart Association functional class, Minnesota living with heart failure questionnaire, 6-minute walk test, peak exercise oxygen consumption, 3D ventricular dyssynchrony and 3D LV ejection fraction., Conclusion: Implantation of the LV lead in the most delayed region of the left ventricle determined by 3D echocardiography did not result in additional improvement in symptoms or LV function.

Background: Multisite left ventricular (multi-LV) epicardial pacing has been proposed as an alternative to conventional single-site LV (single-LV) pacing to increase the efficacy of cardiac resynchronization therapy. Objective: To compare the effects of multi-LV versus single-LV pacing in dogs with left bundle branch block (LBBB). Methods: Studies were performed in 9 anaesthetized dogs with chronic LBBB using 7 LV epicardial electrodes. Each electrode was tested alone and in combination with 1, 2, 3, and 6 other electrodes, the sequence of which was chosen on the basis of practical real-time electrical mapping to determine the site of the latest activation. LV total activation time (LVTAT) and dispersion of repolarization (DRep) were measured by using approximately 100 electrodes around the ventricles. LV contractility was assessed as the maximum derivative of left ventricular pressure (LVdP/dtmax ). Results: Single-LV pacing provided, on average, a −4.0% ± 9.3% change in LVTAT and 0.2% ± 13.7% change in DRep. Multi-LV pacing markedly decreased both LVTAT and DRep in a stepwise fashion to reach −41.3% ± 5% (P < .001 for overall comparison) and −14.2% ± 19.5% (P < .02 for overall comparison) in the septuple-LV pacing configuration, respectively. Single-LV pacing provided a mean increase of 10.7% ± 7.7% in LVdP/dtmax. LVdP/dtmax incrementally increased by the addition of pacing electrodes to 16.4% ± 8.7% (P < .001 for overall comparison). High response to single-LV pacing could not be improved further during multi-LV pacing. Conclusions: Compared with single-LV pacing, multi-LV pacing can considerably reduce both LVTAT and DRep in dogs with LBBB, but the improvement in contractility is limited to conditions where single-LV pacing provides suboptimal improvement. Further studies are warranted to determine whether these acute effects translate in antiarrhythmic properties and better long-term outcomes. [Copyright &y& Elsevier]

. Introduction: Preliminary studies have revealed a high correlation between peak endocardial acceleration (PEA) measured with a sensor embedded in a ventricular lead and human cardiac contractility. In this study we assessed (1) the contributions made by measurements of PEA1, an index of ventricular systolic contraction, from the right atrium, and (2) the feasibility of recording a fourth component of PEA (PEA4), coincident with atrial contraction and corresponding to the phonocardiographic fourth heart sound. Methods: We placed a PEA sensor embedded at the tip of a right atrial lead in 9 pigs. A 7F Millar catheter tip micromanometer was introduced into the left ventricular (LV) cavity to measure dP/dt. Myocardial contractility was increased by infusion of dobutamine and depressed by the infusion of esmolol. We searched, during VDD pacing, for PEA4 following atrial systole, while gradually lengthening the atrioventricular delay. Ventricular fibrillation was then triggered by rapid stimulation. Results: The changes in PEA1 were correlated with the changes in LV dP/dt (r = 0.91; P < 0.001). A low-frequency component of the endocardial signal (PEA4) was visible approximately 50 milliseconds after the atrial electrogram in all experiments. Following the induction of ventricular fibrillation, PEA4 remained visible on the endocardial recording, simultaneous with the sensed atrial electrogram. Conclusions: This study confirms the merit of embedding a PEA sensor in an atrial lead. The exploitation of the information provided by the PEA1 signal remains pertinent and the possibility to record an additional PEA4 component offers the perspective of new clinical applications. (J Cardiovasc Electrophysiol, Vol. 22, pp. 579-583 May 2011) [ABSTRACT FROM AUTHOR]

Aims Although the electrical stimulation of an ischaemic tissue adversely affects the left ventricular (LV) systolic function, the optimal stimulation site in patients with non-ischaemic cardiomyopathy has not been systematically studied. We hypothesized that the local stimulation characteristics at the time of device implantation predict the response to cardiac resynchronization therapy (CRT). Methods and results We measured the impedance, sensing, and capture threshold of a bipolar LV lead in 138 patients with non-ischaemic cardiomyopathy undergoing first implantation of CRT device for drug refractory heart failure. All patients underwent echocardiography at baseline and at 6 months post-implantation. An absence of favourable response to CRT was defined as <15% decrease in echocardiographic LV end-systolic volume (LVESV) at 6 months. Echocardiographic response to CRT was observed in 70% of patients. The LV lead measurements predicted neither the optimal stimulation site nor the response to CRT. Left ventricular capture threshold (1.50 ± 1.1 vs. 1.32 ± 0.8V) and impedance (725 ± 287 vs. 720 ± 261 Ω) were similar between the responders and the non-responders. Independent of baseline LV ejection fraction or ESV, the LV R-wave amplitude at implantation was significantly higher (P = 0.0038) in responders (12.7 ± 5.2 mV) than in non-responders (9.7 ± 6.3 mV), with an area under the receiver operating characteristic curve of 0.7. Conclusion Response to CRT, as determined by decrease in LVESV at 6 months, was associated with significantly higher LV R-wave amplitude at the time of device implantation. [ABSTRACT FROM PUBLISHER]