Association between QRS shortening and mortality after cardiac resynchronization therapy: Results from the DANISH study

BACKGROUND

Changes in QRS duration (∆QRS) are often used in the clinical setting to evaluate the effect of cardiac resynchronization therapy (CRT), although an association between ∆QRS and outcomes is not firmly established. We aimed to assess the association between mortality and ∆QRS after CRT in patients from the DANISH (Danish Study to Assess the Efficacy of ICDs in Patients with Non-Ischemic Systolic Heart Failure on Mortality) study.

METHODS

We included all patients from DANISH who received a CRT device and had available QRS duration data before and after implantation. Cox proportional hazards models were used to assess associations between ∆QRS (post-CRT QRS minus pre-CRT QRS) and mortality.

RESULTS

Complete data were available in 572 patients. Median baseline QRS duration was 160 ms (IQR [146;180]). Post-CRT QRS was recorded a median of 48 days (IQR [33;86]) after implantation, and the median ∆QRS was -14 ms (IQR [-38;-3]). During a median follow-up of 4.1 years (IQR [2.5;5.8]), 106 patients died. In crude Cox regression, all-cause mortality was reduced by 6% per 10 ms shortening of QRS (HR 0.94; CI: 0.88-1.00, p = 0.04). The effect did not remain significant after multivariable adjustment (HR 1.01, CI: 0.93-1.10, p = 0.77). Further, no association was found between ∆QRS and improvement of New York Heart Association functional class at 6 months (OR 1.03, CI: 0.96-1.10, p = 0.42).

CONCLUSION

In a large cohort of patients with non-ischemic cardiomyopathy, reduction of QRS duration after CRT was not associated with changes in mortality during long-term follow-up.

Virtual pacing of a patient's digital twin to predict left ventricular reverse remodelling after cardiac resynchronization therapy

AIMS

Identifying heart failure (HF) patients who will benefit from cardiac resynchronization therapy (CRT) remains challenging. We evaluated whether virtual pacing in a digital twin (DT) of the patient's heart could be used to predict the degree of left ventricular (LV) reverse remodelling post-CRT.

METHODS AND RESULTS

Forty-five HF patients with wide QRS complex (≥130 ms) and reduced LV ejection fraction (≤35%) receiving CRT were retrospectively enrolled. Echocardiography was performed before (baseline) and 6 months after CRT implantation to obtain LV volumes and 18-segment longitudinal strain. A previously developed algorithm was used to generate 45 DTs by personalizing the CircAdapt model to each patient's baseline measurements. From each DT, baseline septal-to-lateral myocardial work difference (MWLW-S,DT) and maximum rate of LV systolic pressure rise (dP/dtmax,DT) were derived. Biventricular pacing was then simulated using patient-specific atrioventricular delay and lead location. Virtual pacing-induced changes ΔMWLW-S,DT and ΔdP/dtmax,DT were correlated with real-world LV end-systolic volume change at 6-month follow-up (ΔLVESV). The DT's baseline MWLW-S,DT and virtual pacing-induced ΔMWLW-S,DT were both significantly associated with the real patient's reverse remodelling ΔLVESV (r = -0.60, P < 0.001 and r = 0.62, P < 0.001, respectively), while correlation between ΔdP/dtmax,DT and ΔLVESV was considerably weaker (r = -0.34, P = 0.02).

CONCLUSION

Our results suggest that the reduction of septal-to-lateral work imbalance by virtual pacing in the DT can predict real-world post-CRT LV reverse remodelling. This DT approach could prove to be an additional tool in selecting HF patients for CRT and has the potential to provide valuable insights in optimization of CRT delivery.

Prognostic implications of invasive hemodynamics during cardiac resynchronization therapy: Stroke work outperforms dP/dtmax

Background

Invasive measurements of left ventricular (LV) hemodynamic performance can evaluate acute response to cardiac resynchronization therapy (CRT).

Objective

The study sought to determine which metric, maximum rate of LV pressure rise (LV dP/dtmax) or LV stroke work (LVSW), is more strongly associated with long-term prognosis.

Methods

CRT patients were prospectively included from 3 academic centers. Invasive pressure-volume loop measurements during implantation were performed, and LV dP/dtmax and LVSW were determined at baseline and during biventricular pacing (BVP) as well as their relative increase (%Δ). Hazard ratios (HRs) for the primary outcome of 8-year all-cause mortality were derived using Cox proportional hazards. The secondary endpoint was echocardiographic response, defined as 6-month LV end-systolic volume reduction ≥15%.

Results

Paired data from 82 patients were analyzed (67% male; age 66 ± 9 years; QRS duration 158 ± 22 ms, median survival time 72 months). Survival was better when LVSW during BVP was ≥4400 mL∙mm Hg (HR 0.21, 95% CI 0.08-0.58, P < .003) or when ΔLVSW% was ≥10% (HR 0.22, 95% CI 0.08-0.65, P = .006). In multivariate analysis, following direct comparison of continuous measures of acute ΔLV dP/dtmax% and ΔLVSW%, only ΔLVSW% remained associated with the primary endpoint (HR 0.982 per percentage point, P = .028). In contrast to LV dP/dtmax (all P > .05), significant associations with echocardiographic response were found for stroke work during BVP (area under the receiver-operating characteristic curve 0.745, P = .001) and ΔLVSW% (area under the receiver-operating characteristic curve 0.803, P < .001).

Conclusion

Stroke work, but not LV dP/dtmax, is consistently associated with long-term prognosis and response after CRT. Our results therefore favor the use of stroke work as the hemodynamic parameter to predict long-term outcome after CRT.

Progress in Cardiac Resynchronisation Therapy and Optimisation

Cardiac resynchronisation therapy (CRT) has become the cornerstone of heart failure (HF) treatment. Despite the obvious benefit from this therapy, an estimated 30% of CRT patients do not respond ("non-responders"). The cause of "non-response" is multi-factorial and includes suboptimal device settings. To optimise CRT settings, echocardiography has been considered the gold standard but has limitations: it is user dependent and consumes time and resources. CRT proprietary algorithms have been developed to perform device optimisation efficiently and with limited resources. In this review, we discuss CRT optimisation including the various adopted proprietary algorithms and conduction system pacing.

Machine learning-powered, device-embedded heart sound measurement can optimize AV delay in patients with CRT

BACKGROUND

Continuous optimization of atrioventricular (AV) delay for cardiac resynchronization therapy (CRT) is mainly performed by electrical means.

OBJECTIVE

The purpose of this study was to develop an estimation model of cardiac function that uses a piezoelectric microphone embedded in a pulse generator to guide CRT optimization.

METHODS

Electrocardiogram, left ventricular pressure (LVP), and heart sounds were simultaneously collected during CRT device implantation procedures. A piezoelectric alarm transducer embedded in a modified CRT device facilitated recording of heart sounds in patients undergoing a pacing protocol with different AV delays. Machine learning (ML) was used to produce a decision-tree ensemble model capable of estimating absolute maximal LVP (LVPmax) and maximal rise of LVP (LVdP/dtmax) using 3 heart sound-based features. To gauge the applicability of ML in AV delay optimization, polynomial curves were fitted to measured and estimated values.

RESULTS

In the data set of ∼30,000 heartbeats, ML indicated S1 amplitude, S2 amplitude, and S1 integral (S1 energy for LVdP/dtmax) as most prominent features for AV delay optimization. ML resulted in single-beat estimation precision for absolute values of LVPmax and LVdP/dtmax of 67% and 64%, respectively. For 20-30 beat averages, cross-correlation between measured and estimated LVPmax and LVdP/dtmax was 0.999 for both. The estimated optimal AV delays were not significantly different from those measured using invasive LVP (difference -5.6 ± 17.1 ms for LVPmax and +5.1 ± 6.7 ms for LVdP/dtmax). The difference in function at estimated and measured optimal AV delays was not statiscally significant (1 ± 3 mm Hg for LVPmax and 9 ± 57 mm Hg/s for LVdP/dtmax).

CONCLUSION

Heart sound sensors embedded in a CRT device, powered by a ML algorithm, provide a reliable assessment of optimal AV delays and absolute LVPmax and LVdP/dtmax.

Tracking Early Systolic Motion for Assessing Acute Response to Cardiac Resynchronization Therapy in Real Time

An abnormal systolic motion is frequently observed in patients with left bundle branch block (LBBB), and it has been proposed as a predictor of response to cardiac resynchronization therapy (CRT). Our goal was to investigate if this motion can be monitored with miniaturized sensors feasible for clinical use to identify response to CRT in real time. Motion sensors were attached to the septum and the left ventricular (LV) lateral wall of eighteen anesthetized dogs. Recordings were performed during baseline, after induction of LBBB, and during biventricular pacing. The abnormal contraction pattern in LBBB was quantified by the septal flash index (SFI) equal to the early systolic shortening of the LV septal-to-lateral wall diameter divided by the maximum shortening achieved during ejection. In baseline, with normal electrical activation, there was limited early-systolic shortening and SFI was low (9 ± 8%). After induction of LBBB, this shortening and the SFI significantly increased (88 ± 34%, p < 0.001). Subsequently, CRT reduced it approximately back to baseline values (13 ± 13%, p < 0.001 vs. LBBB). The study showed the feasibility of using miniaturized sensors for continuous monitoring of the abnormal systolic motion of the LV in LBBB and how such sensors can be used to assess response to pacing in real time to guide CRT implantation.

Pacing Optimized by Left Ventricular dP/dtmax

Left ventricular (LV) dP/dt_max provides a sensitive measure of the acute hemodynamic response to cardiac resynchronization therapy (CRT) and can predict reverse remodeling on echocardiography. Its use to guide LV lead placement has been shown to improve outcomes in a multicenter randomized trial. Given the invasive protocol required for measurement, it is unlikely to be universally beneficial for patients undergoing CRT but may be useful for patients who do not respond to conventional CRT, or in those who have borderline indications or risk factors for non-response. In such cases, LV dP/dt_max may help guide LV lead placement, optimize device programming, and select the best alternative method of delivering CRT, such endocardial LV pacing or conduction system pacing.

Left Ventricular Lead Placement Guided by Reduction in QRS Area

Background: Reduction in QRS area after cardiac resynchronization therapy (CRT) is associated with improved long-term clinical outcome. The aim of this study was to investigate whether the reduction in QRS area is associated with hemodynamic improvement by pacing different LV sites and can be used to guide LV lead placement. Methods: Patients with a class Ia/IIa CRT indication were prospectively included from three hospitals. Acute hemodynamic response was assessed as the relative change in maximum rate of rise of left ventricular (LV) pressure (%∆LVdP/dt_max). Change in QRS area (∆QRS area), in QRS duration (∆QRS duration), and %∆LVdP/dt_max were studied in relation to different LV pacing locations within a patient. Results: Data from 52 patients paced at 188 different LV pacing sites were investigated. Lateral LV pacing resulted in a larger %∆LVdP/dt_max than anterior or posterior pacing (p = 0.0007). A similar trend was found for ∆QRS area (p = 0.001) but not for ∆QRS duration (p = 0.23). Pacing from the proximal electrode pair resulted in a larger %∆LVdP/dt_max (p = 0.004), and ∆QRS area (p = 0.003) but not ∆QRS duration (p = 0.77). Within patients, correlation between ∆QRS area and %∆LVdP/dt_max was 0.76 (median, IQR 0.35; 0,89). Conclusion: Within patients, ∆QRS area is associated with %∆LVdP/dt_max at different LV pacing locations. Therefore, QRS area, which is an easily, noninvasively obtainable and objective parameter, may be useful to guide LV lead placement in CRT.

Optimal CRT Implantation-Where and How To Place the Left-Ventricular Lead?

Purpose of Review

Cardiac resynchronization therapy (CRT) represents a well-established and effective non-pharmaceutical heart failure (HF) treatment in selected patients. Still, a significant number of patients remain CRT non-responders. An optimal placement of the left ventricular (LV) lead appears crucial for the intended hemodynamic and hence clinical improvement. A well-localized target area and tools that help to achieve successful lead implantation seem to be of utmost importance to reach an optimal CRT effect.

Recent Findings

Recent studies suggest previous multimodal imaging (CT/cMRI/ECG torso) to guide intraprocedural LV lead placement. Relevant benefit compared to empirical lead optimization is still a matter of debate. Technical improvements in leads and algorithms (e.g., multipoint pacing (MPP), adaptive algorithms) promise higher procedural success. Recently emerging alternatives for ventricular synchronization such as conduction system pacing (CSP), LV endocardial pacing, or leadless pacing challenge classical biventricular pacing.

Summary

This article reviews current strategies for a successful planning, implementation, and validation of the optimal CRT implantation. Pre-implant imaging modalities offer promising assistance for complex cases; empirical lead positioning and intraoperative testing remain the cornerstone in most cases and ensure a successful CRT effect.

Acute recoordination rather than functional hemodynamic improvement determines reverse remodelling by cardiac resynchronisation therapy

PURPOSE

Cardiac resynchronisation therapy (CRT) improves left ventricular (LV) function acutely, with further improvements and reverse remodelling during chronic CRT. The current study investigated the relation between acute improvement of LV systolic function, acute mechanical recoordination, and long-term reverse remodelling after CRT.

METHODS

In 35 patients, LV speckle tracking longitudinal strain, LV volumes & ejection fraction (LVEF) were assessed by echocardiography before, acutely within three days, and 6 months after CRT. A subgroup of 25 patients underwent invasive assessment of the maximal rate of LV pressure rise (dP/dt_max,) during CRT-implantation. The acute change in dP/dt_max, LVEF, systolic discoordination (internal stretch fraction [ISF] and LV systolic rebound stretch [SRSlv]) and systolic dyssynchrony (standard deviation of peak strain times [2DS-SD18]) was studied, and their association with long-term reverse remodelling were determined.

RESULTS

CRT induced acute and ongoing recoordination (ISF from 45 ± 18 to 27 ± 11 and 23 ± 12%, p < 0.001; SRS from 2.27 ± 1.33 to 0.74 ± 0.50 and 0.71 ± 0.43%, p < 0.001) and improved LV function (dP/dt_max 668 ± 185 vs. 817 ± 198 mmHg/s, p < 0.001; stroke volume 46 ± 15 vs. 54 ± 20 and 52 ± 16 ml; LVEF 19 ± 7 vs. 23 ± 8 and 27 ± 10%, p < 0.001). Acute recoordination related to reverse remodelling (r = 0.601 and r = 0.765 for ISF & SRSlv, respectively, p < 0.001). Acute functional improvements of LV systolic function however, neither related to reverse remodelling nor to the extent of acute recoordination.

CONCLUSION

Long-term reverse remodelling after CRT is likely determined by (acute) recoordination rather than by acute hemodynamic improvements. Discoordination may therefore be a more important CRT-substrate that can be assessed and, acutely restored.

Second European Society of Cardiology Cardiac Resynchronization Therapy Survey: the Italian cohort

AIM

Adherence to guidelines was not homogeneous in Europe, according to the survey on cardiac resynchronization therapy conducted in 2008-2009. The aim of our study was to compare the results in the Italian and European cohorts of the Second European Cardiac Resynchronization Therapy Survey.

METHODS

Patients' characteristics, procedural data and follow-up were collected. Italian records were compared with European countries.

RESULTS

Italian hospitals enrolled 526 patients. The italian cohort was older (71.6 ± 9.5 vs. 68.4 ± 10.8; P < 0.00001), had less severe NYHA class (>II 47.2 vs. 59.6%; P < 0.00001), higher ejection fraction (30.3 ± 7.4 vs. 28.4 ± 8.2%; P < 0.00001), and less atrial fibrillation prevalence (34.4 vs. 41.2%; P = 0.00197) than the European cohort. Italian patients were more frequently hospitalized for heart failure in the previous year (51.9 vs. 46.2%; P = 0.01118) and had lower mean QRS duration (151 ± 26 vs. 157 ± 27 ms; P < 0.0001). CRT-D were more often implanted in Italian patients (79.3 vs. 69.3%; P < 0.00001). The complication rate was similar (4.6% vs. 5.6%; ns). The rate of use of ACEi/ARBs in Italy was lower than in Europe (77.2 vs. 86.9%; P < 0.00001). Patients were followed up in the implantation centre (92.1 vs. 86%; P = 0.00014), but rarely with remote monitoring (25.9 vs. 30%; P = 0.04792).

CONCLUSION

The survey demonstrates important similarities as well as substantial differences regarding most of the aspects evaluated. Efforts to implement adherence to guidelines will be endorsed in Italy.

Evaluating multisite pacing strategies in cardiac resynchronization therapy in the preclinical setting

Background

Multisite pacing strategies that improve response to cardiac resynchronization therapy (CRT) have been proposed. Current available options are pacing 2 electrodes in a multipolar lead in a single vein (multipoint pacing [MPP]) and pacing using 2 leads in separate veins (multizone pacing [MZP]).

Objective

The purpose of this study was to compare in a systematic manner the acute hemodynamic response (AHR) and electrophysiological effects of MPP and MZP and compare them with conventional biventricular pacing (BiVP).

Methods

Hemodynamic and electrophysiological effects were evaluated in a porcine model of acute left bundle branch block (LBBB) (n = 8). AHR was assessed as LVdP/dtmax. Activation times were measured using >100 electrodes around the epicardium, measuring total activation time (TAT) and left ventricular activation time (LVAT).

Results

Compared to LBBB, BiVP, MZP, and MPP reduced TAT by 26% ± 10%, 32% ± 13%, and 32% ± 14%, respectively (P = NS between modes) and LVAT by 4% ± 5%, 11% ± 5%, and 12% ± 5%, respectively (P <.05 BiVP vs MPP and MZP). On average, BiVP increased LVdP/dtmax by 8% ± 4%, and optimal BiVP increased LVdP/dtmax by 13% ± 4%. The additional improvement in LVdP/dtmax by MZP and MPP was significant only when its increase during BiVP and decrease in TAT were poor (lower 25% of all sites in 1 subject). The increase in LVdP/dtmax was larger when large interelectrode distances (>5 cm vs <2.2 cm) were used.

Conclusion

In this animal model of acute LBBB, MPP and MZP create similar degrees of electrical resynchronization and hemodynamic effect, which are larger if interelectrode distance is large. MPP and MZP increase the benefit of CRT only if the left ventricular lead used for BiVP provides poor response.

Left ventricular global longitudinal strain and mechanical dispersion predict response to multipoint pacing for cardiac resynchronization therapy

PURPOSE

To evaluate the acute effect of multipoint pacing (MPP) and search for the better baseline predictors of response to MPP for guiding patient selection.

METHODS

We enrolled 46 heart failure patients scheduled for implantation of MPP-enabled cardiac resynchronization therapy (CRT) devices. An acute pacing protocol including conventional CRT and MPP pacing configurations was performed after implantation. Echocardiography was used at baseline and during pacing test, and response was defined as left ventricular (LV) end-systolic volume (ESV) reduction ≥ 15% at 6-month follow-up.

RESULTS

MPP response was present in 32 (69%) patients. Responders showed significantly superior LV ejection fraction, global longitudinal peak strain (GLPS), and mechanical dispersion (MD) with MPP than with conventional CRT (all P < 0.05). Baseline GLPS (OR 1.524; 95% CI 1.031-2.251; P = 0.034) and MD (OR 1.048; 95% CI 1.016-1.081; P = 0.003) were independent predictors of MPP response in multivariate regression analysis. Both |GLPS| and MD were significantly correlated with percentage change in LVESV (▵LVESV%) at 6-month follow-up (r = 0.731 and r = 0.696, respectively; all P < 0.001). |GLPS| ≥ 5.0% combined with MD ≥ 120 ms predicted MPP response with the optimal sensitivity of 91% and specificity of 71% (AUC = 0.848, P < 0.001).

CONCLUSIONS

MPP tends to be superior to conventional CRT in improving acute response. |GLPS| and MD can successfully predict response to MPP, and their combination can further improve the prediction accuracy of response.

Left ventricular end-systolic volume is a more sensitive marker of acute response to cardiac resynchronization therapy than contractility indices: insights from an experimental study

Aims

There are conflicting data and no consensus on how to measure acute response to cardiac resynchronization therapy (CRT). This study investigates, which contractility indices are best markers of acute CRT response.

Methods and results

In eight anaesthetized dogs with left bundle branch block, we measured left ventricular (LV) pressure by micromanometer and end-diastolic volume (EDV) and end-systolic volume (ESV) by sonomicrometry. Systolic function was measured as LV ejection fraction (EF), peak rate of LV pressure rise (LV dP/dtmax) and as a gold standard of contractility, LV end-systolic elastance (Ees), and volume axis intercept (V0) calculated from end-systolic pressure-volume relations (ESPVR). Responses to CRT were compared with inotropic stimulation by dobutamine. Both CRT and dobutamine caused reduction in ESV (P < 0.01) and increase in LV dP/dtmax (P < 0.05). Both interventions shifted the ESPVR upwards indicating increased contractility, but CRT which reduced V0 (P < 0.01), caused no change in Ees. Dobutamine markedly increased Ees, which is the typical response to inotropic stimulation. Preload (EDV) was decreased (P < 0.01) by CRT, and there was no change in EF. When adjusting for the reduction in preload, CRT increased EF (P = 0.02) and caused a more marked increase in LV dP/dtmax (P < 0.01).

Conclusion

Increased contractility by CRT could not be identified by Ees, which is a widely used reference method for contractility. Furthermore, reduction in preload by CRT attenuated improvement in contractility indices such as EF and LV dP/dtmax. These results suggest that changes in LV volume may be more sensitive markers of acute CRT response than conventional contractility indices.

Current role of echocardiography in cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) is an established treatment for patients with heart failure and left ventricular systolic dysfunction. Patients are usually assessed by echocardiography, which provides a number of anatomical and functional information used for cardiac dyssynchrony assessment, prognostic stratification, identification of the optimal site of pacing in the left ventricle, optimization of the CRT device, and patient follow-up. Compared to other cardiac imaging techniques, echocardiography has the advantage to be non-invasive, repeatable, and safe, without exposure to ionizing radiation or nefrotoxic contrast. In this article, we review current evidence about the role of echocardiography before, during, and after the implantation of a CRT device.

Non-invasive, model-based measures of ventricular electrical dyssynchrony for predicting CRT outcomes

AIMS

Left ventricular activation delay due to left bundle branch block (LBBB) is an important determinant of the severity of dyssynchronous heart failure (DHF). We investigated whether patient-specific computational models constructed from non-invasive measurements can provide measures of baseline dyssynchrony and its reduction after CRT that may explain the degree of long-term reverse ventricular remodelling.

METHODS AND RESULTS

LV end-systolic volume reduction (ΔESV_LV) measured by 2D trans-thoracic echocardiography in eight patients following 6 months of CRT was significantly (P < 0.05) greater in responders (26 ± 20%, n = 4) than non-responders (11 ± 16%, n = 4). LV reverse remodelling did not correlate with baseline QRS duration or its change after biventricular pacing, but did correlate with baseline LV endocardial activation measured by electroanatomic mapping (R²=0.71, P < 0.01). Patient-specific models of LBBB ventricular activation with parameters obtained by matching model-computed vectorcardiograms (VCG) to those derived from standard patient ECGs yielded LV endocardial activation times that correlated well with those measured from endocardial maps (R²=0.90). Model-computed 3D LV activation times correlated strongly with the reduction in LVESV (R²=0.93, P < 0.001). Computed decreases due to simulated CRT in the time delay between LV septal and lateral activation correlated strongly with ΔESV_LV (R²=0.92, P < 0.001). Models also suggested that optimizing VV delays may improve resynchronization by this measure of activation delay.

CONCLUSIONS

Patient-specific computational models constructed from non-invasive measurements can compute estimates of LV dyssynchrony and their changes after CRT that may be as good as or better than electroanatomic mapping for predicting long-term reverse remodelling.

New insights from a computational model on the relation between pacing site and CRT response

AIMS

Cardiac resynchronization therapy (CRT) produces clinical benefits in chronic heart failure patients with left bundle-branch block (LBBB). The position of the pacing site on the left ventricle (LV) is considered an important determinant of CRT response, but the mechanism how the LV pacing site determines CRT response is not completely understood. The objective of this study is to investigate the relation between LV pacing site during biventricular (BiV) pacing and cardiac function.

METHODS AND RESULTS

We used a finite element model of BiV electromechanics. Cardiac function, assessed as LV dp/dt_max and stroke work, was evaluated during normal electrical activation, typical LBBB, fascicular blocks and BiV pacing with different LV pacing sites. The model replicated clinical observations such as increase of LV dp/dt_max and stroke work, and the disappearance of a septal flash during BiV pacing. The largest hemodynamic response was achieved when BiV pacing led to best resynchronization of LV electrical activation but this did not coincide with reduction in total BiV activation time (∼ QRS duration). Maximum response was achieved when pacing the mid-basal lateral wall and this was close to the latest activated region during intrinsic activation in the typical LBBB, but not in the fascicular block simulations.

CONCLUSIONS

In these model simulations, the best cardiac function was obtained when pacing the mid-basal LV lateral wall, because of fastest recruitment of LV activation. This study illustrates how computer modeling can shed new light on optimizing pacing therapies for CRT. The results from this study may help to design new clinical studies to further investigate the importance of the pacing site for CRT response.

Prediction of optimal cardiac resynchronization by vectors extracted from electrograms in dyssynchronous canine hearts

INTRODUCTION

Proper optimization of atrioventricular (AV) and interventricular (VV) intervals can improve the response to cardiac resynchronization therapy (CRT). It has been demonstrated that the area of the QRS complex (QRSarea) extracted from the vectorcardiogram can be used as a predictor of optimal CRT-device settings. We explored the possibility of extracting vectors from the electrograms (EGMs) obtained from pacing electrodes and of using these EGM-based vectors (EGMVs) to individually optimize acute hemodynamic CRT response.

METHODS AND RESULTS

Biventricular pacing was performed in 13 dogs with left bundle branch block (LBBB) of which five also had myocardial infarction (MI), using 100 randomized AV- and VV-settings. Settings providing an acute increase in LV dP/dt_max ≥ 90% of the highest achieved value were defined as optimal. The prediction capability of QRSarea derived from the EGMV (EGMV-QRSarea) was compared with that of QRS duration. EGMV-QRSarea strongly correlated to the change in LV dP/dt_max (R = -0.73 ± 0.19 [LBBB] and -0.66 ± 0.14 [LBBB + MI]), while QRS duration was more poorly related to LV dP/dt_max changes (R = -0.33 ± 0.25 [LBBB] and -0.47 ± 0.39 [LBBB + MI]). This resulted in a better prediction of optimal CRT-device settings by EGMV-QRSarea than by QRS duration (LBBB: AUC = 0.89 [0.86-0.93] vs. 0.76 [0.69-0.83], P < 0.01; LBBB + MI: AUC = 0.91 [0.84-0.99] vs. 0.82 [0.59-1.00], P = 0.20, respectively).

CONCLUSION

In canine hearts with chronic LBBB with or without MI, the EGMV-QRSarea predicts acute hemodynamic CRT response and identifies optimal AV and VV settings accurately. These data support the potency of EGM-based vectors as a noninvasive, easy and patient-tailored tool to optimize CRT-device settings.

Exploring the Electrophysiologic and Hemodynamic Effects of Cardiac Resynchronization Therapy: From Bench to Bedside and Vice Versa

Cardiac resynchronization therapy (CRT) is an important therapy for heart failure patients with prolonged QRS duration. In patients with left bundle branch block the altered left ventricular electrical activation results in dyssynchronous, inefficient contraction of the left ventricle. CRT aims to reverse these changes and to improve cardiac function. This article explores the electrophysiologic and hemodynamic changes that occur during CRT in patient and animal studies. It also addresses how novel techniques, such as multipoint and endocardial pacing, can further improve the electromechanical response.

In Heart Failure Patients with Left Bundle Branch Block Single Lead MultiSpot Left Ventricular Pacing Does Not Improve Acute Hemodynamic Response To Conventional Biventricular Pacing. A Multicenter Prospective, Interventional, Non-Randomized Study

INTRODUCTION

Recent efforts to increase CRT response by multiSPOT pacing (MSP) from multiple bipols on the same left ventricular lead are still inconclusive.

AIM

The Left Ventricular (LV) MultiSPOTpacing for CRT (iSPOT) study compared the acute hemodynamic response of MSP pacing by using 3 electrodes on a quadripolar lead compared with conventional biventricular pacing (BiV).

METHODS

Patients with left bundle branch block (LBBB) underwent an acute hemodynamic study to determine the %change in LV+dP/dtmax from baseline atrial pacing compared to the following configurations: BiV pacing with the LV lead in a one of lateral veins, while pacing from the distal, mid, or proximal electrode and all 3 electrodes together (i.e. MSP). All measurements were repeated 4 times at 5 different atrioventricular delays. We also measured QRS-width and individual Q-LV durations.

RESULTS

Protocol was completed in 24 patients, all with LBBB (QRS width 171±20 ms) and 58% ischemic aetiology. The percentage change in LV+dP/dtmax for MSP pacing was 31.0±3.3% (Mean±SE), which was not significantly superior to any BiV pacing configuration: 28.9±3.2% (LV-distal), 28.3±2.7% (LV-mid), and 29.5±3.0% (LV-prox), respectively. Correlation between LV+dP/dtmax and either QRS-width or Q-LV ratio was poor.

CONCLUSIONS

In patients with LBBB MultiSPOT LV pacing demonstrated comparable improvement in contractility to best conventional BiV pacing. Optimization of atrioventricular delay is important for the best performance for both BiV and MultiSPOT pacing configurations.

TRIAL REGISTRATION

ClinicalTrials.gov NTC01883141.

Acute contractile recovery extent during biventricular pacing is not associated with follow-up in patients undergoing resynchronization

Background

It has been reported that contractility, as assessed using dobutamine infusion, is independently associated with reverse remodeling after CRT. Controversy, however, exists about the capacity of this approach to predict a long-term clinical response. This study's purpose was to assess whether long-term CRT clinical effects can be predicted according to acute inotropic response induced by biventricular stimulation (CRT on), as compared with AAI–VVI right stimulation pacing mode (CRT off), quantified at the time of implantation.

Methods

In 98 patients (ejection fraction 29 ± 10%), acute changes in left ventricular (LV) elastance (Ees), arterial elastance (Ea), and Ees/Ea, as assessed from slope changes of the force–frequency relation obtained when the heart rate increased, and also assessed while measuring triplane LV volumes and continuous noninvasive blood pressure, were related to death or rehospitalization during a 3-year follow-up. Other covariances tested were age, gender, disease etiology, QRS duration, amount of mitral regurgitation, LV diastolic volume, ejection fraction, and the degree of asynchrony and longitudinal strain at baseline.

Results

There was a marked increment in the Ees slope with CRT (interaction P = 0.004), no Ea change, and modest Ees/Ea increase (interaction P < 0.05). In Cox analysis, however, neither slope changes nor baseline values of Ees, Ea, and Ees/Ea were associated with long-term follow-up. Only ventricular diastolic volume (direct relation P = 0.002) and QRS duration (inverse relation P = 0.009) predicted death/rehospitalization.

Conclusions

Acute contractile recovery in CRT patients is not associated with 3 years prognosis. Instead, death or rehospitalization can be predicted from QRS duration and LV diastolic volume at baseline.

Pathophysiology of dyssynchrony: of squirrels and broken bones

The genesis of cardiac resynchronisation therapy (CRT) consists of 'bedside' research and 'bench' studies that are performed in series with each other. In this field, the bench studies are crucial for understanding the pathophysiology of dyssynchrony and resynchronisation. In a way, CRT started with the insight that abnormal ventricular conduction, as caused by right ventricular pacing, has adverse effects. Out of this research came the ground-breaking insight that 'simple' disturbances in impulse conduction, which were initially considered innocent, proved to result in a host of molecular and cellular derangements that lead to a vicious circle of remodelling processes that facilitate the development of heart failure. As a consequence, CRT does not only correct conduction abnormalities, but also improves myocardial properties at many levels. Interestingly, corrections by CRT do not exactly reverse the derangements, induced by dyssynchrony, but also activate novel pathways, a property that may open new avenues for the treatment of heart failure.

Haemodynamic effects of cardiac resynchronization therapy using single-vein, three-pole, multipoint left ventricular pacing in patients with ischaemic cardiomyopathy and a left ventricular free wall scar: the MAESTRO study

AIMS

The clinical response to cardiac resynchronization therapy (CRT) is variable. Multipoint left ventricular (LV) pacing could achieve more effective haemodynamic response than single-point LV pacing. Deployment of an LV lead over myocardial scar is associated with a poor haemodynamic response to and clinical outcome of CRT. We sought to determine whether the acute haemodynamic response to CRT using three-pole LV multipoint pacing (CRT3P-MPP) is superior to that to conventional CRT using single-site LV pacing (CRTSP) in patients with ischaemic cardiomyopathy and an LV free wall scar.

METHODS AND RESULTS

Sixteen patients with ischaemic cardiomyopathy [aged 72.6 ± 7.7 years (mean ± SD), 81.3% male, QRS: 146.0 ± 14.2 ms, LBBB in 14 (87.5%)] in whom the LV lead was intentionally deployed straddling an LV free wall scar (assessed using cardiac magnetic resonance), underwent assessment of LV + dP/dtmax during CRT3P-MPP and CRTSP. Interindividually, the ΔLV + dP/dtmax in relation to AAI pacing with CRT3P-MPP (6.2 ± 13.3%) was higher than with basal and mid CRTSP (both P < 0.001), but similar to apical CRTSP. Intraindividually, significant differences in the ΔLV + dP/dtmax to optimal and worst pacing configurations were observed in 10 (62.5%) patients. Of the 8 patients who responded to at least one configuration, CRT3P-MPP was optimal in 5 (62.5%) and apical CRTSP was optimal in 3 (37.5%) (P = 0.0047).

CONCLUSIONS

In terms of acute haemodynamic response, CRT3P-MPP was comparable an apical CRTSP and superior to basal and distal CRTSP. In the absence of within-device haemodynamic optimization, CRT3P-MPP may offer a haemodynamic advantage over a fixed CRTSP configuration.

Exploring the Electrophysiologic and Hemodynamic Effects of Cardiac Resynchronization Therapy: From Bench to Bedside and Vice Versa

Cardiac resynchronization therapy (CRT) is an important therapy for heart failure patients with prolonged QRS duration. In patients with left bundle branch block the altered left ventricular electrical activation results in dyssynchronous, inefficient contraction of the left ventricle. CRT aims to reverse these changes and to improve cardiac function. This article explores the electrophysiologic and hemodynamic changes that occur during CRT in patient and animal studies. It also addresses how novel techniques, such as multipoint and endocardial pacing, can further improve the electromechanical response.

The impact of beat-to-beat variability in optimising the acute hemodynamic response in cardiac resynchronisation therapy

BACKGROUND

Acute indicators of response to cardiac resynchronisation therapy (CRT) are critical for developing lead optimisation algorithms and evaluating novel multi-polar, multi-lead and endocardial pacing protocols. Accounting for beat-to-beat variability in measures of acute haemodynamic response (AHR) may help clinicians understand the link between acute measurements of cardiac function and long term clinical outcome.

METHODS AND RESULTS

A retrospective study of invasive pressure tracings from 38 patients receiving an acute pacing and electrophysiological study was performed. 602 pacing protocols for left ventricle (LV) (n = 38), atria-ventricle (AV) (n = 9), ventricle-ventricle (VV) (n = 12) and endocardial (ENDO) (n = 8) optimisation were performed. AHR was measured as the maximal rate of LV pressure development (dP/dtMx) for each beat. The range of the 95% confidence interval (CI) of mean AHR was ~ 7% across all optimisation protocols compared with the reported CRT response cut off value of 10%. A single clear optimal protocol was identifiable in 61%, 22%, 25% and 50% for LV, AV, VV and ENDO optimisation cases, respectively. A level of service (LOS) optimisation that aimed to maximise the expected AHR 5th percentile, minimising variability and maximising AHR, led to distinct optimal protocols from conventional mean AHR optimisation in 34%, 78%, 67% and 12.5% of LV, AV, VV and ENDO optimisation cases, respectively.

CONCLUSION

The beat-to-beat variation in AHR is significant in the context of CRT cut off values. A LOS optimisation offers a novel index to identify the optimal pacing site that accounts for both the mean and variation of the baseline measurement and pacing protocol.

The relative role of patient physiology and device optimisation in cardiac resynchronisation therapy: A computational modelling study

Cardiac resynchronisation therapy (CRT) is an established treatment for heart failure, however the effective selection of patients and optimisation of therapy remain controversial. While extensive research is ongoing, it remains unclear whether improvements in patient selection or therapy planning offers a greater opportunity for the improvement of clinical outcomes. This computational study investigates the impact of both physiological conditions that guide patient selection and the optimisation of pacing lead placement on CRT outcomes. A multi-scale biophysical model of cardiac electromechanics was developed and personalised to patient data in three patients. These models were separated into components representing cardiac anatomy, pacing lead location, myocardial conductivity and stiffness, afterload, active contraction and conduction block for each individual, and recombined to generate a cohort of 648 virtual patients. The effect of these components on the change in total activation time of the ventricles (ΔTAT) and acute haemodynamic response (AHR) was analysed. The pacing site location was found to have the largest effect on ΔTAT and AHR. Secondary effects on ΔTAT and AHR were found for functional conduction block and cardiac anatomy. The simulation results highlight a need for a greater emphasis on therapy optimisation in order to achieve the best outcomes for patients.

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Ventricular conduction block indicates patient response to CRT.

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Placement of CRT pacing leads strongly affects response to therapy.

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Improved treatment planning should be prioritised in order to maximise CRT outcomes.

Cardiac resynchronization therapy update: evolving indications, expanding benefit?

Cardiac resynchronisation therapy (CRT) is an effective intervention for appropriately selected patients with heart failure, but exactly how it works is uncertain. Recent data suggest that much, or perhaps most, of the benefits of CRT are not delivered by re-coordinating left ventricular dyssynchrony. Atrio-ventricular resynchronization, reduction in mitral regurgitation and prevention of bradycardia are other potential mechanisms of benefit that will vary from one patient to the next and over time. Because there is no single therapeutic target, it is unlikely that any single measure will accurately predict benefit. The only clinical characteristic that appears to be a useful predictor of the benefits of CRT is a QRS duration of >140 ms. Many new approaches are being developed to try to improve the effectiveness of and extend the indications for CRT. These include smart pacing algorithms, better pacing-site targeting, new sensors, multipoint pacing, remote device monitoring and leadless endocardial pacing. Whether CRT is effective in patients with atrial fibrillation or whether adding a defibrillator function to CRT improves prognosis awaits further evidence.

Vectorcardiography for optimization of stimulation intervals in cardiac resynchronization therapy

Current optimization of atrioventricular (AV) and interventricular (VV) intervals in cardiac resynchronization therapy (CRT) is time consuming and subject to noise. We aimed to prove the principle that the best hemodynamic effect of CRT is achieved by cancelation of opposing electrical forces, detectable from the QRS morphology in the 3D vectorcardiogram (VCG). Different degrees of left (LV) and right ventricular (RV) pre-excitation were induced, using variation in AV intervals during LV pacing in 20 patients with left bundle branch block (LBBB) and variation in VV intervals during biventricular pacing in 18 patients with complete AV block or atrial fibrillation. The smallest QRS vector area identified stimulation intervals with minimal systolic stretch (median difference [IQR] 20 ms [−20, 20 ms] and maximal hemodynamic response (10 ms [−20, 40 ms]). Reliability of VCG measurements was superior to hemodynamic measurements. This study proves the principle that VCG analysis may allow easy and reliable optimization of stimulation intervals in CRT patients.

Multisite left ventricular pacing in cardiac resynchronization therapy

Cardiac resynchronization therapy is an effective treatment for selected patients with heart failure and left bundle branch block dyssynchrony. Unfortunately, about a third of patients, so-called nonresponders, do not display any symptomatic or structural improvements after the treatment. In another 5% of patients, the left ventricular lead cannot be implanted due to technical limitations. Novel quadripolar pacing lead and associated multisite pacing technology has the potential to help improve both of these problems. The technology and applications of these leads are reviewed and the novel technique of multisite pacing from two poles of one quadripolar lead is discussed. This technology may improve response to cardiac resynchronization therapy for some patients.

Strategies to improve cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) emerged 2 decades ago as a useful form of device therapy for heart failure associated with abnormal ventricular conduction, indicated by a wide QRS complex. In this Review, we present insights into how to achieve the greatest benefits with this pacemaker therapy. Outcomes from CRT can be improved by appropriate patient selection, careful positioning of right and left ventricular pacing electrodes, and optimal timing of electrode stimulation. Left bundle branch block (LBBB), which can be detected on an electrocardiogram, is the predominant substrate for CRT, and patients with this conduction abnormality yield the most benefit. However, other features, such as QRS morphology, mechanical dyssynchrony, myocardial scarring, and the aetiology of heart failure, might also determine the benefit of CRT. No single left ventricular pacing site suits all patients, but a late-activated site, during either the intrinsic LBBB rhythm or right ventricular pacing, should be selected. Positioning the lead inside a scarred region substantially impairs outcomes. Optimization of stimulation intervals improves cardiac pump function in the short term, but CRT procedures must become easier and more reliable, perhaps with the use of electrocardiographic measures, to improve long-term outcomes.

High-density epicardial activation mapping to optimize the site for video-thoracoscopic left ventricular lead implant

Background

The left ventricular (LV) lead local electrogram (EGM) delay from the beginning of the QRS complex (QLV) is considered a strong predictor of response to cardiac resynchronization therapy. We have developed a method for fast epicardial QLV mapping during video-thoracoscopic surgery to guide LV lead placement.

Methods

A three-port, video-thoracoscopic approach was used for LV free wall epicardial mapping and lead implantation. A decapolar electrophysiological catheter was introduced through one port and systematically attached to multiple accessible LV sites. The pacing lead was targeted to the site with maximum QLV. The LV free wall activation pattern was analyzed in 16 pre-specified anatomical segments.

Results

We implanted LV leads in 13 patients with LBBB or IVCD. The procedural and mapping times were 142 ± 39 minutes and 20 ± 9 minutes, respectively. A total of 15.0 ± 2.2 LV segments were mappable with variable spatial distribution of QLV-optimum. The QLV ratio (QLV/QRSd) at the optimum segment was significantly higher (by 0.17 ± 0.08, p < 0.00001) as compared to an empirical midventricular lateral segment. The LV lead was implanted at the optimum segment in 11 patients (at an adjacent segment in 2 patients) achieving a QLV ratio of 0.82 ± 0.09 (range 0.63–0.93) and 99.5 ± 0.6% match with intraprocedural mapping.

Conclusion

Video-thoracoscopic LV lead implantation can be effectively and safely guided by epicardial QLV mapping. This strategy was highly successful in targeting the selected LV segment and resulted in significantly higher QLV ratios compared to an empirical midventricular lateral segment.

Optimal Strategies on Avoiding CRT Nonresponse

OPINION STATEMENT

The high rate of nonresponse to cardiac resynchronization therapy (CRT) has remained nearly unchanged since the treatment was introduced. We believe that this is directly related to the many persisting unknowns regarding the mechanical function of asynchronous hearts and the use of electrical stimulation to counteract the deleterious effects of that asynchrony. As a consequence, the key questions pertaining to the pre-implant, intra-implant, and postimplant phases remain unanswered or only partially answered. QRS duration is an imperfect selection criterion, as it does not discriminate the activation pattern. The inclusion of QRS morphology in the international professional practice guidelines is an important first step toward increasing the yield of this therapy. The invasive and the noninvasive electrical mapping techniques seem highly promising and need to be tested in large trials. The site of stimulation is a key element of the response to CRT; additional research must be pursued in this field.

A comparison of left ventricular endocardial, multisite, and multipolar epicardial cardiac resynchronization: an acute haemodynamic and electroanatomical study

AIMS

Alternative forms of cardiac resynchronization therapy (CRT), including biventricular endocardial (BV-Endo) and multisite epicardial pacing (MSP), have been developed to improve response. It is unclear which form of stimulation is optimal. We aimed to compare the acute haemodynamic response (AHR) and electrophysiological effects of BV-Endo with MSP via two separate coronary sinus (CS) leads or a single-quadripolar CS lead.

METHODS AND RESULTS

Fifteen patients with a previously implanted CRT system received a second temporary CS lead and left ventricular (LV) endocardial catheter. A pressure wire and non-contact mapping array were placed into the LV cavity to measure LVdP/dtmax and perform electroanatomical mapping. Conventional CRT, BV-Endo, and MSP were then performed (MSP-1 via two epicardial leads and MSP-2 via a single-quadripolar lead). The best overall AHR was found using BV-Endo pacing with a 19.6 ± 13.6% increase in AHR at the optimal endocardial site over baseline (P < 0.001). There was an increase in LVdP/dtmax with MSP-1 and MSP-2 compared with conventional CRT, but this was not statistically significant. Biventricular endocardial pacing from the optimal site was significantly superior to conventional CRT (P = 0.039). The AHR achieved when BV-Endo pacing was highly site specific. Within individuals, the best pacing modality varied and was affected by the underlying substrate. Left ventricular activation times did not predict the optimal haemodynamic configuration.

CONCLUSION

Biventricular endocardial pacing and not MSP was superior to conventional CRT, but was highly site specific. Within individuals, however, different methods of stimulation are optimal and may need to be tailored to the underlying substrate.