Midterm 'super-response' to cardiac resynchronization therapy by biventricular pacing with fusion: insights from electro-anatomical mapping

Emergent role of dynamic optimization in cardiac resynchronization therapy: Systematic review and network meta-analysis

AIMS

Suboptimal device programming is frequent in non-responders to cardiac resynchronization therapy (CRT). However, the role of device optimization and the most appropriate technique are still unknown. The aim of our study was to analyse the effect of different CRT optimization techniques within a network meta-analysis.

METHODS

A systematic search was conducted on MEDLINE, Embase and CENTRAL for studies comparing outcomes with empirical device settings or optimization using echocardiography, static algorithms or dynamic algorithms. Studies investigating the effect of optimization in non-responders were also analysed.

RESULTS

A total of 17 studies with 4346 patients were included in the quantitative analysis. Of the treatments and outcomes examined, a significant difference was found only between dynamic algorithms and echocardiography, with the former leading to a higher echocardiographic response rate [odds ratio (OR): 2.02, 95% confidence interval (CI) 1.21-3.35], lower heart failure hospitalization rate (OR: 0.75, 95% CI 0.57-0.99) and greater improvement in 6-minute walk test [mean difference (MD): 45.52 m, 95% credible interval (CrI) 3.91-82.44 m]. We found no significant difference between empirical settings, static algorithms and dynamic algorithms. Seven studies with 228 patients reported response rates after optimization in non-responders. Altogether, 34.3%-66.7% of initial non-responders showed improvement after optimization, depending on response criteria.

CONCLUSIONS

At the time of CRT implantation, dynamic algorithms may serve as a resource-friendly alternative to echocardiographic optimization, with similar or better mid-term outcomes. However, their superiority over empirical device settings needs to be investigated in further trials. For non-responders, CRT optimization should be considered, as the majority of patients experience improvement.

Nonischemic Super-Responders in Fusion CRT Pacing with Normal Atrioventricular Conduction

Background: Fusion CRT pacing (FCRT) is noninferior to biventricular pacing, according to the current data. The aim of this study is to assess the response to FCRT and to identify predictors of super-responders (SRs) in a nonischemic population with normal AV conduction. Methods: LV-only CRT patients (pts) with a right atrium/left ventricle pacing system implanted in two CRT centers in Romania were included. Device interrogation, exercise tests, echocardiography, and individualized drug optimization were performed every 6 months during close follow-up. SRs pts were defined as those with left ventricular end-systolic volume (LVESV) improvement ≥30% and stable ejection fraction (LVEF) ≥45%. Results: A total of 25 out of 83 pts (31%) were SRs, with nonischemic LBBB low EF cardiomyopathy (50 male, 62 ± 9 y.o.) initially included. Mean follow-up was 5 years ± 27 months. Patients were divided in two groups: SRs and non-SRs (52 responders/6 hypo-responders). Two predictors were found in the SRs group: a higher baseline LVEF (SRs 29 ± 5% vs. non-SRs 26 ± 5%, p = 0.02) and a lower pulmonary arterial systolic pressure (SRs 38 ± 11 mm Hg vs. non-SRs 50 ± 15 mmHg, p = 0.003). Baseline severe mitral regurgitation was found in 11% of SRs vs. 64% in the non-SRs group. Conclusions: SRs in the selected NICM-FCRT group are significative high. Higher baseline LVEF and mild pulmonary arterial hypertension were independently associated with super-response.

What Have We Learned in the Last 20 Years About CRT Non-Responders?

Although cardiac resynchronization therapy (CRT) has become well established in the treatment of heart failure, the management of patients who do not respond after CRT remains a key challenge. This review will summarize what we have learned about non-responders over the last 20 years and discuss methods for optimizing response, including the introduction of novel therapies.

Programming Algorithms for Cardiac Resynchronization Therapy

Current cardiac resynchronization therapy (CRT) implant guidelines emphasize the presence of electrical dyssynchrony (left bundle branch block (LBBB) and QRS > 150 ms) yet have modest predictive value for response and have not reduced the 30% nonresponse rate. Optimized programming to optimize CRT delivery has promised much but to date has largely been ineffective. What is missing is the understanding of LV paced effects (which are unpredictable) and optimal paced AV interval (that can be conserved during physiologic variations) that then can be incorporated into an individualized programming prescription. Automatic device-based algorithms that deliver electrical optimization and maintain this during ambulatory fluctuations in AV interval are discussed.

Betablockers and Ivabradine Titration According to Exercise Test in LV Only Fusion CRT Pacing

Background: Betablockers (BB)/ivabradine titration in fusion CRT pacing (CRTP) is understudied. Aim: To assess drug optimization using systematic exercise tests (ET) in fusion CRTP with preserved atrioventricular conduction (AVc). Methods: Changes in drug management were assessed during systematic follow-ups in CRTP patients without right ventricle lead. Shorter AVc (PR interval) allowed BB up-titration, while longer AVc needed BB down-titration, favoring ivabradine. Constant fusion pacing was the goal to improve outcomes. Results: 64 patients, 62.5 ± 9.5 y.o divided into three groups: shorter PR (<160 ms), normal (160−200 ms), longer (200−240 ms); follow-up 59 ± 26 months. Drugs were titrated in case of: capture loss due to AVc shortening (14%), AVc lengthening (5%), chronotropic incompetence (11%), maximum tracking rate issues (9%), brady/tachyarrhythmias (8%). Interventions: BB up-titration (78% shorter PR, 19% normal PR, 5% longer PR), BB down-titration (22% shorter PR, 14% normal PR), BB exclusion (16% longer PR), adding/up-titration ivabradine (22% shorter PR, 19% normal PR, 5% longer PR), ivabradine down-titration (22% shorter PR, 3% normal PR), ivabradine exclusion (11% normal PR, 5% longer PR). Drug strategy was changed in 165 follow-ups from 371 recorded (42% patients). Conclusions: BBs/ivabradine titration and routine ET during follow-ups in patients with fusion CRTP should be a standard approach to maximize resynchronization response. Fusion CRTP showed a positive outcome with important LV reverse remodeling and significant LVEF improvement in carefully selected patients.

Electrocardiography of cardiac resynchronization therapy: Pitfalls and practical tips

Cardiac resynchronization therapy (CRT) has been established as an effective mode of therapy in patients with heart failure and concurrent cardiac dyssynchrony, principally in the form of left bundle branch block (LBBB). The widespread use of CRT has ushered in a new landscape in 12-lead electrocardiography (ECG). ECG readings in these patients are most important to guide troubleshooting and also appropriate device programming, as well as discerning and managing nonresponders. A set of four ECG recordings need to accompany each patient with a CRT device, including a baseline ECG and recordings from monochamber (right and left ventricular) and biventricular pacing, which can be compared against a new recording to facilitate the evaluation of proper versus problematic biventricular pacing. Precordial ECG leads V1/2 acquired at the fourth intercostal space and limb leads, I and III, together with a quick assessment of perpendicular leads I and aVF to determine the quadrant of the QRS axis in the hexaxial diagram, may provide the framework for proper ECG interpretation in these patients. This important issue of 12-lead ECG in CRT patients is herein reviewed, pitfalls are pointed out and practical tips are provided for ECG reading to help recognize and manage problems with CRT device function. Furthermore, several pertinent ECG recordings and tabulated data are provided, and an algorithm is suggested that integrates prior algorithms and relevant information from current literature.

Clinical Utility of Body Surface Potential Mapping in CRT Patients

This paper reviews the current status of the knowledge on body surface potential mapping (BSPM) and ECG imaging (ECGI) methods for patient selection, left ventricular (LV) lead positioning, and optimisation of CRT programming, to indicate the major trends and future perspectives for the application of these methods in CRT patients. A systematic literature review using PubMed, Scopus, and Web of Science was conducted to evaluate the available clinical evidence regarding the usage of BSPM and ECGI methods in CRT patients. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) statement was used as a basis for this review. BSPM and ECGI methods applied in CRT patients were assessed, and quantitative parameters of ventricular depolarisation delivered from BSPM and ECGI were extracted and summarised. BSPM and ECGI methods can be used in CRT in several ways, namely in predicting CRT outcome, in individualised optimisation of CRT device programming, and the guiding of LV electrode placement, however, further prospective or randomised trials are necessary to verify the utility of BSPM for routine clinical practice.

Fusion Pacing with Biventricular, Left Ventricular-only and Multipoint Pacing in Cardiac Resynchronisation Therapy: Latest Evidence and Strategies for Use

Despite advances in the field of cardiac resynchronisation therapy (CRT), response rates and durability of therapy remain relatively static. Optimising device timing intervals may be the most common modifiable factor influencing CRT efficacy after implantation. This review addresses the concept of fusion pacing as a method for improving patient outcomes with CRT. Fusion pacing describes the delivery of CRT pacing with a programming strategy to preserve intrinsic atrioventricular (AV) conduction and ventricular activation via the right bundle branch. Several methods have been assessed to achieve fusion pacing. QRS complex duration (QRSd) shortening with CRT is associated with improved clinical response. Dynamic algorithm-based optimisation targeting narrowest QRSd in patients with intact AV conduction has shown promise in people with heart failure with left bundle branch block. Individualised dynamic programming achieving fusion may achieve the greatest magnitude of electrical synchrony, measured by QRSd narrowing.

Electrical wavefront fusion in heart failure patients with left bundle branch block and cardiac resynchronization therapy: Implications for optimization

BACKGROUND

Novel metrics of electrical dyssynchrony based on multi-electrode mapping and ECG-based markers of fusion are better predictors of cardiac resynchronization therapy (CRT) response than QRS duration.

OBJECTIVE

To describe a new methodology for measuring electrical synchrony based on wavefront fusion and electrocardiographic cancellation in patients with CRT and its potential for CRT optimization.

METHODS

Patients with left bundle branch block (LBBB) type conduction and CRT (n = 84) were studied at multiple device settings using an ECG belt (53 anterior and posterior electrodes). The area between combinations of anterior and posterior curves (AUC) was calculated and cardiac resynchronization index (CRI) defined as percent change in AUC compared to LBBB.

RESULTS

In 14 patients with complete heart block or atrial fibrillation, CRI at optimal ventriculo-ventricular delay (VVD) (40 ± 19 ms) was significantly higher than with simultaneous biventricular pacing (BiVp) (90 ± 8.6% vs. 54.2 ± 24.2%, p < 0.001). In all 70 patients paced LV-only, LV-paced wavefront was ahead of native wavefront at short atrio-ventricular delay (AVD) and CRI increased with increase in AVD, peaked, and then decreased. Optimal CRI during LV-only pacing was significantly better than optimal CRI with simultaneous BiVp (89.6 ± 8% vs. 64.4 ± 22%, p < 0.001), and occurred at AVD 68 ± 22 ms less than the atrial-RV sensed interval. With sequential BiVp, best CRI was 83.9 ± 13% (with LV preactivation of 40 ± 20 ms). Best CRI at any setting was markedly better than CRI at standard setting (91.6 ± 7.7% vs. 52.7 ± 23.3, p < 0.001).

CONCLUSION

We describe a novel non-invasive investigational tool that quantifies wavefront fusion and electrical dyssynchrony, and may allow for individualized CRT optimization.

Patient-tailored SyncAV algorithm: A novel strategy to improve synchrony and acute hemodynamic response in heart failure patients treated by cardiac resynchronization therapy

INTRODUCTION

Several automatic algorithms have developed to optimize the timing cycle setting in cardiac resynchronization therapy (CRT). The present study aims to investigate whether the novel device-based SyncAV algorithm could elicit better synchrony and acute hemodynamic response.

METHODS AND RESULTS

Thirty five patients undergoing CRT implantation were prospectively studied. The device was programmed to three biventricular (BiV) pacing modes sequentially after the procedure: QuickOpt algorithm (mode I), SyncAV algorithm with default 50 ms offset (mode II), and SyncAV algorithm with optimized offset minimizing QRS duration (QRSd) (mode III). After each setting, electrocardiographic and echocardiographic data were collected. As a result, QRSd was reduced from 172.8 ± 17.9 ms during intrinsic conduction to 153.1 ± 15.9 ms in mode I, further narrowed to 140.5 ± 16.7 ms in mode II, and reached shortest (134.8 ± 16.1 ms) in mode III (P < .01 for all). Besides, significantly shorter QT intervals were observed in mode I (453.2 ± 45.5 ms), mode II (443.9 ± 34.2 ms) and mode III (444.1 ± 28.7 ms), compared with native condition (472.5 ± 51.2 ms) (P < .01). All three BiV modes exhibited comparable T_p T_e interval and T_p T_e /QT ratio (P > .05). Mode I presented significantly higher aortic velocity time integral than intrinsic conduction (21.0 ± 6.4 cm vs 18.4 ± 5.5 cm; P < .01), which was even higher in mode II (22.0 ± 6.5 cm) and mode III (23.7 ± 6.5 cm). All three BiV modes significantly reduced standard deviation of time to peak contraction of 12-LV segments (Ts-SD) (Mode I: 55.2 ± 16.5 ms, Mode II: 50.2 ± 14.7 ms, Mode III: 45.4 ± 14.4 ms) compared with intrinsic conduction (66.3 ± 18.4 ms) (P < .01), with Mode III demonstrating the smallest (P < .01).

CONCLUSION

SyncAV CRT ameliorated electrical and mechanical synchrony as well as acute hemodynamic response beyond conventional QuickOpt optimization. An additional individualized adjustment to the SyncAV offset added to its advantage.

Exercise test is essential in LV-only fusion CRT pacing without right ventricle lead

Purpose: Left ventricle (LV)-only pacing is non-inferior to biventricular pacing but permanent fusion pacing is needed to ensure cardiac resynchronization therapy (CRT) responsiveness. The role of systematic exercise testing (ET) in these patients has not been established. This study was designed to assess clinical and therapeutic implications (device programming/drugs) of systematic ET in patients requiring fusion-pacing CRT without an right ventricle (RV) lead. Methods: Consecutive patients with a right atrium/LV-only dual-chamber (DDD) pacing system were included. Prospective data were obtained: device interrogation, ET, and echocardiography at every 6-month follow-up visit. CRT assessment during ET included maximal heart rate, beat-to-beat echocardiography analysis of LV fusion pacing, LV loss of capture, and improvement in exercise capacity. If LV loss of capture or unsatisfactory LV fusion pacing occurred, reprogramming was individualized for each patient and ET redone. Results: A total of 55 patients (29 male) aged 62±11 years were included. During follow-up (39±18 months), a total of 235 ETs were performed, with mean exercise load 6.4±1.3 metabolic equivalents of task (118±35 W, maximal heart rate 119±17 beats/min). Twenty patients (36%) had inadequate pacing or loss of LV capture during ET, due to exceeding the maximum tracking rate (11%), chronotropic incompetence (7%), and LV pacing outside the fusion-pacing band (18%), caused by physiological shortening of the PR interval or exagerated LV preexcitation during maximum exercise. Post-ET CRT-device optimization included reprogramming of rate-adaptive atrioventricular interval (total decrease 23±8 ms), individualized programming of maximum tracking rate, or rate-response function. Drug optimization was performed in 32% of patients, and ET redone in 36%. Conclusion: In one of three ETs, an intervention in device and medication optimization was done to ensure a better outcome. Routine ET should be a standard approach to maximize fusion-pacing CRT response during follow-up.

Electrocardiographic optimization techniques in resynchronization therapy

Cardiac resynchronization therapy (CRT) is a cornerstone of therapy for patients with heart failure, reduced left ventricular (LV) ejection fraction, and a wide QRS complex. However, not all patients respond to CRT: 30% of CRT implanted patients are currently considered clinical non-responders and up to 40% do not achieve LV reverse remodelling. In order to achieve the best CRT response, appropriate patient selection, device implantation, and programming are important factors. Optimization of CRT pacing intervals may improve results, increasing the number of responders, and the magnitude of the response. Echocardiography is considered the reference method for atrioventricular and interventricular (VV) intervals optimization but it is time-consuming, complex and it has a large interobserver and intraobserver variability. Previous studies have linked QRS shortening to clinical response, echocardiographic improvement and favourable prognosis. In this review, we describe the electrocardiographic optimization methods available: 12-lead electrocardiogram; fusion-optimized intervals (FOI); intracardiac electrogram-based algorithms; and electrocardiographic imaging. Fusion-optimized intervals is an electrocardiographic method of optimizing CRT based on QRS duration that combines fusion with intrinsic conduction. The FOI method is feasible and fast, further reduces QRS duration, can be performed during implant, improves acute haemodynamic response, and achieves greater LV remodelling compared with nominal programming of CRT.

Comparison of Echocardiographic and Electrocardiographic Mapping for Cardiac Resynchronisation Therapy Optimisation

Study hypothesis

We sought to investigate the association between echocardiographic optimisation and ventricular activation time in cardiac resynchronisation therapy (CRT) patients, obtained through the use of electrocardiographic mapping (ECM). We hypothesised that echocardiographic optimisation of the pacing delay between the atrial and ventricular leads-atrioventricular delay (AVD)-and the delay between ventricular leads-interventricular pacing interval (VVD)-would correlate with reductions in ventricular activation time.

Background

Optimisation of AVD and VVD may improve CRT patient outcome. Optimal delays are currently set based on echocardiographic indices; however, acute studies have found that reductions in bulk ventricular activation time correlate with improvements in acute haemodynamic performance.

Materials and methods

Twenty-one patients with established CRT criteria were recruited. After implantation, patients underwent echo-guided optimisation of the AVD and VVD. During this procedure, the participants also underwent noninvasive ECM. ECM maps were constructed for each AVD and VVD. ECM maps were analysed offline. Total ventricular activation time (TVaT) and a ventricular activation time index (VaT_10-90) were calculated to identify the optimal AVD and VVD timings that gave the minimal TVaT and VaT_10-90 values. We correlated cardiac output with these electrical timings.

Results

Echocardiographic programming optimisation was not associated with the greatest reductions in biventricular activation time (VaT_10-90 and TVaT). Instead, bulk activation times were reduced by a further 20% when optimised with ECM. A significant inverse correlation was identified between reductions in bulk ventricular activation time and improvements in LVOT VTI (p < 0.001), suggesting that improved ventricular haemodynamics are a sequelae of more rapid ventricular activation.

Conclusions

EAM-guided programming optimisation may achieve superior fusion of activation wave fronts leading to improvements in CRT response.

Optimization of Lead Placement in the Right Ventricle During Cardiac Resynchronization Therapy. A Simulation Study

Patients suffering from heart failure and left bundle branch block show electrical ventricular dyssynchrony causing an abnormal blood pumping. Cardiac resynchronization therapy (CRT) is recommended for these patients. Patients with positive therapy response normally present QRS shortening and an increased left ventricle (LV) ejection fraction. However, around one third do not respond favorably. Therefore, optimal location of pacing leads, timing delays between leads and/or choosing related biomarkers is crucial to achieve the best possible degree of ventricular synchrony during CRT application. In this study, computational modeling is used to predict the optimal location and delay of pacing leads to improve CRT response. We use a 3D electrophysiological computational model of the heart and torso to get insight into the changes in the activation patterns obtained when the heart is paced from different regions and for different atrioventricular and interventricular delays. The model represents a heart with left bundle branch block and heart failure, and allows a detailed and accurate analysis of the electrical changes observed simultaneously in the myocardium and in the QRS complex computed in the precordial leads. Computational simulations were performed using a modified version of the O'Hara et al. action potential model, the most recent mathematical model developed for human ventricular electrophysiology. The optimal location for the pacing leads was determined by QRS maximal reduction. Additionally, the influence of Purkinje system on CRT response was assessed and correlation analysis between several parameters of the QRS was made. Simulation results showed that the right ventricle (RV) upper septum near the outflow tract is an alternative location to the RV apical lead. Furthermore, LV endocardial pacing provided better results as compared to epicardial stimulation. Finally, the time to reach the 90% of the QRS area was a good predictor of the instant at which 90% of the ventricular tissue was activated. Thus, the time to reach the 90% of the QRS area is suggested as an additional index to assess CRT effectiveness to improve biventricular synchrony.

Optimizing Cardiac Resynchronization Therapy Devices in Follow-up to Improve Response Rates and Outcomes

Although cardiac resynchronization therapy (CRT) will improve symptoms and survival in selected heart failure patients, there still remains a high percentage of CRT recipients who do not obtain benefit from the therapy. During CRT follow-up, an effort should be made to identify and to treat reversible causes of nonresponse to CRT. This effort includes optimization of medical therapy, checking for appropriate and effective biventricular pacing, and treatment of arrhythmias and other reversible causes of CRT malfunction.

Programming Cardiac Resynchronization Therapy for Electrical Synchrony: Reaching Beyond Left Bundle Branch Block and Left Ventricular Activation Delay

BACKGROUND

QRS narrowing following cardiac resynchronization therapy with biventricular (BiV) or left ventricular (LV) pacing is likely affected by patient-specific conduction characteristics (PR, qLV, LV-paced propagation interval), making a universal programming strategy likely ineffective. We tested these factors using a novel, device-based algorithm (SyncAV) that automatically adjusts paced atrioventricular delay (default or programmable offset) according to intrinsic atrioventricular conduction.

METHODS AND RESULTS

Seventy-five patients undergoing cardiac resynchronization therapy (age 66±11 years; 65% male; 32% with ischemic cardiomyopathy; LV ejection fraction 28±8%; QRS duration 162±16 ms) with intact atrioventricular conduction (PR interval 194±34, range 128-300 ms), left bundle branch block, and optimized LV lead position were studied at implant. QRS duration (QRSd) reduction was compared for the following pacing configurations: nominal simultaneous BiV (Mode I: paced/sensed atrioventricular delay=140/110 ms), BiV+SyncAV with 50 ms offset (Mode II), BiV+SyncAV with offset that minimized QRSd (Mode III), or LV-only pacing+SyncAV with 50 ms offset (Mode IV). The intrinsic QRSd (162±16 ms) was reduced to 142±17 ms (-11.8%) by Mode I, 136±14 ms (-15.6%) by Mode IV, and 132±13 ms (-17.8%) by Mode II. Mode III yielded the shortest overall QRSd (123±12 ms, -23.9% [P<0.001 versus all modes]) and was the only configuration without QRSd prolongation in any patient. QRS narrowing occurred regardless of QRSd, PR, or LV-paced intervals, or underlying ischemic disease.

CONCLUSIONS

Post-implant electrical optimization in already well-selected patients with left bundle branch block and optimized LV lead position is facilitated by patient-tailored BiV pacing adjusted to intrinsic atrioventricular timing using an automatic device-based algorithm.

Electrocardiographic patterns in biventricular pacing delivered by second-generation cardiac resynchronization devices

BACKGROUND

With increasing use of cardiac resynchronization therapy (CRT), treating physicians should be familiar with different electrocardiographic (ECG) patterns of left ventricular (LV) lead and biventricular (BiV) pacing. However, there are a few publications on ECG patterns during BiV pacing.

PURPOSE

This study was sought to determine different ECG patterns in patients with BiV pacing.

METHODS

Twelve-lead ECGs during BiV pacing (right ventricular leads at apex and LV leads in one of the lateral coronary veins) were analyzed in 181 consecutive patients (121 male; mean age, 62.0 ± 13.5 years) with advanced heart failure and baseline left bundle branch block pattern after at least 6-month of uncomplicated CRT.

RESULTS

During BiV pacing, 65% of the patients showed a dominant R wave in V1. There was a right axis deviation in 57% in frontal plane. However, a left superior axis emerged in 34% and normal frontal plane axis in 9%. Sequential BiV pacing (73% vs. 58%, P = 0.04) and pacing from posterolateral coronary vein (80% vs. 60%, p = 0.045) were more likely to present with a dominant R wave in V1. In sequential pacing, AV interval was significantly longer in patients with negative complex in V1 than in those with positive complex (124 ± 21 vs. 116 ± 8.0, p = 0.005). A Q/q wave was detected in 85% of patients in lead I and 78% in lead aVL.

CONCLUSIONS

BiV pacing from lateral coronary venous branches and right ventricular apex characteristically presented with dominant R wave in V1, Q/q wave in leads I and aVL, and right or left superior axis. However, a negative complex in V1, QRS axis in other quadrants, and lack of Q/q wave in leads I and aVL did not necessarily indicate a problem.

Development and validation of a phase analysis tool to measure interventricular mechanical dyssynchrony from gated SPECT MPI

OBJECTIVES

The purpose of this study is to develop a right-ventricular (RV) phase analysis tool which when coupled with our left ventricular (LV) phase analysis tool can provide measurement of the interventricular mechanical dyssynchrony from gated SPECT myocardial perfusion imaging (MPI), and validate the tool by electrocardiography (ECG).

METHODS

For each patient, short-axis LV and RV SPECT MPI images were input into an automatic sampling algorithm to generate the 3D maximal count circumferential profiles for both LV and RV in each cardiac frame. Subsequently, the samples of LV and RV were separately used by our phase analysis tool based on the first-harmonic Fourier approximation to calculate the contraction onset for each sample. The difference between contraction onsets of the middle LV free wall and middle LV septal wall represented the LV contraction delay; the difference between contraction onsets of the middle RV free wall and middle RV septal wall represented the RV contraction delay. The difference between the LV and RV contraction delays represented the interventricular contraction delay, which was compared with the interventricular conduction delay classified by ECG to validate the concordance of interventricular mechanical and electrical dyssynchrony. Sixty-one bundle branch block (BBB) patients with ischemic-dilated cardiomyopathy (26, 42.6%) or non-ischemic-dilated cardiomyopathy (35, 57.4%), who underwent 12-lead surface ECG and gated resting Tc-99m sestamibi SPECT, were retrospectively analyzed in this study.

RESULTS

In the 30 patients with left bundle branch block (LBBB) by ECG, there were 27 patients whose LV contracted later than the RV according to SPECT; and in the 31 patients with right bundle branch block (RBBB) by ECG, there were 26 patients whose LV contracted earlier than the RV according to SPECT. In total, an agreement rate of 86.9% (53 of 61) was achieved between SPECT and ECG. The Kappa agreement rate was 73.8% (95% confidence interval 0.57-0.91).

CONCLUSION

The preliminary results showed promise for the measurement of interventricular mechanical dyssynchrony in BBB patients with dilated cardiomyopathy using our phase analysis tool.

Left univentricular pacing for cardiac resynchronization therapy

This review describes the rationale and published evidence for left univentricular pacing for cardiac resynchronization therapy, gives an overview of the existing optimization algorithms featuring this mode, and discusses future perspectives.

The influence of right ventricular stimulation on acute response to cardiac resynchronisation therapy

Background

The contribution of right ventricular (RV) stimulation to cardiac resynchronisation therapy (CRT) remains controversial. RV stimulation might be associated with adverse haemodynamic effects, dependent on intrinsic right bundle branch conduction, presence of scar, RV function and other factors which may partly explain non-response to CRT. This study investigates to what degree RV stimulation modulates response to biventricular (BiV) stimulation in CRT candidates and which baseline factors, assessed by cardiac magnetic resonance imaging, determine this modulation.

Methods and results

Forty-one patients (24 (59 %) males, 67 ± 10 years, QRS 153 ± 22 ms, 21 (51 %) ischaemic cardiomyopathy, left ventricular (LV) ejection fraction 25 ± 7 %), who successfully underwent temporary stimulation with pacing leads in the RV apex (RV_apex) and left ventricular posterolateral (PL) wall were included. Stroke work, assessed by a conductance catheter, was used to assess acute haemodynamic response during baseline conditions and RV_apex, PL (LV) and PL+RV_apex (BiV) stimulation.

Compared with baseline, stroke work improved similarly during LV and BiV stimulation (∆+ 51 ± 42 % and ∆+ 48 ± 47 %, both p < 0.001), but individual response showed substantial differences between LV and BiV stimulation. Multivariate analysis revealed that RV ejection fraction (β = 1.01, p = 0.02) was an independent predictor for stroke work response during LV stimulation, but not for BiV stimulation. Other parameters, including atrioventricular delay and scar presence and localisation, did not predict stroke work response in CRT.

Conclusion

The haemodynamic effect of addition of RV_apex stimulation to LV stimulation differs widely among patients receiving CRT. Poor RV function is associated with poor response to LV but not BiV stimulation.

Electronic supplementary material

The online version of this article (doi:10.1007/s12471-015-0770-x) contains supplementary material, which is available to authorized users.

Integration of mechanical, structural and electrical imaging to understand response to cardiac resynchronization therapy

INTRODUCTION AND OBJECTIVES

There is extensive controversy exists on whether cardiac resynchronization therapy corrects electrical or mechanical asynchrony. The aim of this study was to determine if there is a correlation between electrical and mechanical sequences and if myocardial scar has any relevant impact.

METHODS

Six patients with normal left ventricular function and 12 patients with left ventricular dysfunction and left bundle branch block, treated with cardiac resynchronization therapy, were studied. Real-time three-dimensional echocardiography and electroanatomical mapping were performed in all patients and, where applicable, before and after therapy. Magnetic resonance was performed for evaluation of myocardial scar. Images were postprocessed and mechanical and electrical activation sequences were defined and time differences between the first and last ventricular segment to be activated were determined. Response to therapy was defined as a reduction in left ventricular end-systolic volume ≥ 15% after 12 months of follow-up.

RESULTS

Good correlation between electrical and mechanical timings was found in patients with normal left ventricular function (r(2) = 0.88; P = .005) but not in those with left ventricular dysfunction (r(2) = 0.02; P = not significant). After therapy, both timings and sequences were modified and improved, except in those with myocardial scar.

CONCLUSIONS

Despite a close electromechanical relationship in normal left ventricular function, there is no significant correlation in patients with dysfunction. Although resynchronization therapy improves this correlation, the changes in electrical activation may not yield similar changes in left ventricular mechanics particularly depending on the underlying myocardial substrate.

Images as drivers of progress in cardiac computational modelling

Computational models have become a fundamental tool in cardiac research. Models are evolving to cover multiple scales and physical mechanisms. They are moving towards mechanistic descriptions of personalised structure and function, including effects of natural variability. These developments are underpinned to a large extent by advances in imaging technologies. This article reviews how novel imaging technologies, or the innovative use and extension of established ones, integrate with computational models and drive novel insights into cardiac biophysics. In terms of structural characterization, we discuss how imaging is allowing a wide range of scales to be considered, from cellular levels to whole organs. We analyse how the evolution from structural to functional imaging is opening new avenues for computational models, and in this respect we review methods for measurement of electrical activity, mechanics and flow. Finally, we consider ways in which combined imaging and modelling research is likely to continue advancing cardiac research, and identify some of the main challenges that remain to be solved.

Clinical response with adaptive CRT algorithm compared with CRT with echocardiography-optimized atrioventricular delay: a retrospective analysis of multicentre trials

AIMS

Adaptive cardiac resynchronization therapy (aCRT) is a novel algorithm for CRT pacing that provides automatic ambulatory selection between synchronized left ventricular (LV) or bi-ventricular (BiV) pacing and optimization of atrioventricular (AV) and inter-ventricular (VV) delays based on periodic measurement of intrinsic conduction. We aimed to compare the clinical response between aCRT and standard CRT in historical trials.

METHODS AND RESULTS

The treatment arm of the aCRT trial was compared with a pooled historical control (HC) derived from the CRT arms of four clinical trials (MIRACLE, MIRACLE ICD, PROSPECT, and InSync III Marquis) with respect to the proportion of patients who had an improved clinical composite score (CCS) at the 6-month follow-up. Patients in the HC underwent echocardiography-guided AV optimization after the implant. A propensity score model was used to adjust for 22 potential baseline confounders of the effect of CRT. Patients were stratified into quintiles according to the propensity score and the adjusted absolute treatment effect was obtained by averaging estimates across these quintiles. The propensity score model included 751 patients (aCRT: 266, historical trials: 485). The adjusted absolute difference in percent improved in CCS between the aCRT and HC arms was 11.9% [95% confidence interval (CI): 2.7-19.2%] favouring aCRT. The patients in the aCRT group were significantly more likely to have an improved CCS than the patients in the HC (odds ratio = 1.65, 95% CI: 1.1-2.5).

CONCLUSION

The aCRT algorithm may be associated with additional improvement in clinical response compared with historical CRT with echocardiographic AV optimization.

Feasibility of temporary biventricular pacing after off-pump coronary artery bypass grafting in patients with reduced left ventricular function

In selected patients undergoing cardiac surgery, our research group previously showed that optimized temporary biventricular pacing can increase cardiac output one hour after weaning from cardiopulmonary bypass. Whether pacing is effective after beating-heart surgery is unknown. Accordingly, in this study we examined the feasibility of temporary biventricular pacing after off-pump coronary artery bypass grafting. The effects of optimized pacing on cardiac output were measured with an electromagnetic aortic flow probe at the conclusion of surgery in 5 patients with a preoperative mean left ventricular ejection fraction of 0.26 (range, 0.15-0.35). Atrioventricular (7) and interventricular (9) delay settings were optimized in randomized order. Cardiac output with optimized biventricular pacing was 4.2 ± 0.7 L/min; in sinus rhythm, it was 3.8 ± 0.5 L/min. Atrial pacing at a matched heart rate resulted in cardiac output intermediate to that of sinus rhythm and biventricular pacing (4 ± 0.6 L/min). Optimization of atrioventricular and interventricular delay, in comparison with nominal settings, trended toward increased flow. This study shows that temporary biventricular pacing is feasible in patients with preoperative left ventricular dysfunction who are undergoing off-pump coronary artery bypass grafting. Further study of the possible clinical benefits of this intervention is warranted.

Electrocardiographic versus echocardiographic optimization of the interventricular pacing delay in patients undergoing cardiac resynchronization therapy

INTRODUCTION

Echocardiographic optimization of the VV interval may improve CRT response, but it is time-consuming and not routinely performed. The aim of this study was to compare the response to cardiac resynchronization therapy (CRT) when the interventricular pacing (VV) interval was optimized by tissue Doppler imaging (TDI) to CRT response when it was optimized following QRS width criteria.

METHODS AND RESULTS

The study included 156 consecutive CRT patients with severe heart failure and left bundle-branch block configuration. Atrioventricular interval was selected according to a pulsed Doppler assessment, and VV optimization was randomly assigned to echocardiography (ECHO group, n = 78) or electrocardiography (ECG group, n = 78). Optimal VV was defined for the ECHO group as producing the best LV intraventricular synchrony according to TDI displacement curves and for the ECG group as resulting in the narrowest QRS measured from the earliest deflection. At 6-month follow-up, percentage of echocardiographic responders (defined as neither death nor heart transplantation and a LV end-systolic volume reduction >10%) was higher in the ECG optimized group (50.0% vs 67.9%; P = 0.023), whereas clinical response (defined as neither death nor heart transplantation and >10% improvement in the 6-minute walking test) was similar in both groups (71.8% vs 73.1%; P = 0.858).

CONCLUSIONS

VV optimization based on QRS width obtained a higher percentage of responders in terms of LV reverse remodeling compared to the TDI method.

Bifocal right ventricular resynchronization for the failing right ventricle

The present case illustrates that in patients with right ventricular (RV) failure and right bundle branch block it is possible to resynchronize the RV without further worsening RV or left ventricular (LV) pump function, even in cases with various degrees of atrioventricular block. The acute response to different pacing configurations was analyzed in terms of dP/dt variations. Bifocal RV pacing (His bundle plus RV outflow tract pacing) achieved the best acute results and was chosen for permanent pacing. This pacing configuration was associated to clinical and echocardiographic improvement.