Primary Results From the SmartDelay Determined AV Optimization: A Comparison to Other AV Delay Methods Used in Cardiac Resynchronization Therapy (SMART-AV) Trial

Using Machine-Learning for Prediction of the Response to Cardiac Resynchronization Therapy: The SMART-AV Study

OBJECTIVES

This study aimed to apply machine learning (ML) to develop a prediction model for short-term cardiac resynchronization therapy (CRT) response to identifying CRT candidates for early multidisciplinary CRT heart failure (HF) care.

BACKGROUND

Multidisciplinary optimization of cardiac resynchronization therapy (CRT) delivery can improve long-term CRT outcomes but requires substantial staff resources.

METHODS

Participants from the SMART-AV (SmartDelay-Determined AV Optimization: Comparison of AV Optimization Methods Used in Cardiac Resynchronization Therapy [CRT]) trial (n = 741; age: 66 ± 11 years; 33% female; 100% New York Heart Association HF class III-IV; 100% ejection fraction ≤35%) were randomly split into training/testing (80%; n = 593) and validation (20%; n = 148) samples. Baseline clinical, electrocardiographic, echocardiographic, and biomarker characteristics, and left ventricular (LV) lead position (43 variables) were included in 8 ML models (random forests, convolutional neural network, lasso, adaptive lasso, plugin lasso, elastic net, ridge, and logistic regression). A composite of freedom from death and HF hospitalization and a >15% reduction in LV end-systolic volume index at 6 months after CRT was the end point.

RESULTS

The primary end point was met by 337 patients (45.5%). The adaptive lasso model was the most more accurate (area under the receiver operating characteristic curve: 0.759; 95% confidence interval [CI]: 0.678-0.840), well calibrated, and parsimonious (19 predictors; nearly half potentially modifiable). Participants in the 5th quintile compared with those in the 1st quintile of the prediction model had 14-fold higher odds of composite CRT response (odds ratio: 14.0; 95% CI: 8.0-14.4). The model predicted CRT response with 70% accuracy, 70% sensitivity, and 70% specificity, and should be further validated in prospective studies.

CONCLUSIONS

ML predicts short-term CRT response and thus may help with CRT procedure and early post-CRT care planning. (SmartDelay-Determined AV Optimization: A Comparison of AV Optimization Methods Used in Cardiac Resynchronization Therapy [CRT] [SMART-AV]; NCT00677014).

Cardiac Magnetic Resonance Assessment of Response to Cardiac Resynchronization Therapy and Programming Strategies

OBJECTIVES

The objective was to determine the feasibility and effectiveness of cardiac magnetic resonance (CMR) cine and strain imaging before and after cardiac resynchronization therapy (CRT) for assessment of response and the optimal resynchronization pacing strategy.

BACKGROUND

CMR with cardiac implantable electronic devices can safely provide high-quality right ventricular/left ventricular (LV) ejection fraction (RVEF/LVEF) assessments and strain.

METHODS

CMR with cine imaging, displacement encoding with stimulated echoes for the circumferential uniformity ratio estimate with singular value decomposition (CURE-SVD) dyssynchrony parameter, and scar assessment was performed before and after CRT. Whereas the pre-CRT scan constituted a single "imaging set" with complete volumetric, strain, and scar imaging, multiple imaging sets with complete strain and volumetric data were obtained during the post-CRT scan for biventricular pacing (BIVP), LV pacing (LVP), and asynchronous atrial pacing modes by reprogramming the device outside the scanner between imaging sets.

RESULTS

100 CMRs with a total of 162 imaging sets were performed in 50 patients (median age 70 years [IQR: 50 years-86 years]; 48% female). Reduction in LV end-diastolic volumes (P = 0.002) independent of CRT pacing were more prominent than corresponding reductions in right ventricular end-diastolic volumes (P = 0.16). A clear dependence of the optimal CRT pacing mode (BIVP vs LVP) on the PR interval (P = 0.0006) was demonstrated. The LVEF and RVEF improved more with BIVP than LVP with PR intervals ≥240 milliseconds (P = 0.025 and P = 0.002, respectively); the optimal mode (BIVP vs LVP) was variable with PR intervals <240 milliseconds. A lower pre-CRT displacement encoding with stimulated echoes CURE-SVD was associated with greater improvements in the post-CRT CURE-SVD (r = -0.69; P < 0.001), LV end-systolic volume (r = -0.58; P < 0.001), and LVEF (r = -0.52; P < 0.001).

CONCLUSIONS

CMR evaluation with assessment of multiple pacing modes during a single scan after CRT is feasible and provides useful information for patient care with respect to response and the optimal pacing strategy.

Optimized implementation of cardiac resynchronization therapy: a call for action for referral and optimization of care

Cardiac resynchronization therapy (CRT) is one of the most effective therapies for heart failure with reduced ejection fraction and leads to improved quality of life, reductions in heart failure hospitalization rates and all-cause mortality. Nevertheless, up to two-thirds of eligible patients are not referred for CRT. Furthermore, post-implantation follow-up is often fragmented and suboptimal, hampering the potential maximal treatment effect. This joint position statement from three European Society of Cardiology Associations, Heart Failure Association (HFA), European Heart Rhythm Association (EHRA) and European Association of Cardiovascular Imaging (EACVI), focuses on optimized implementation of CRT. We offer theoretical and practical strategies to achieve more comprehensive CRT referral and post-procedural care by focusing on four actionable domains: (i) overcoming CRT under-utilization, (ii) better understanding of pre-implant characteristics, (iii) abandoning the term 'non-response' and replacing this by the concept of disease modification, and (iv) implementing a dedicated post-implant CRT care pathway.

Contemporary ICD Use in Patients with Heart Failure

Despite constant breakthroughs in heart failure (HF) therapy, the population of HF patients resume to grow and is linked to increased mortality and morbidity. Ventricular arrhythmias (VA) are one of the leading causes of mortality in HF subjects. Implantable cardioverter-defibrillators (ICDs) are currently the gold standard in treatment, preventing arrhythmic sudden cardiac death (SCD) episodes. However, the death rates related to HF remain elevated, as not all HF subjects benefit equally. Cardiac resynchronization therapy (CRT) has emerged as a novel approach for HF patients. These devices have been thoroughly investigated in major randomized controlled studies but continue to be underutilized in various countries. This review discusses the use of ICD in HF populations on top of treatments.

State-of-the-art narrative review: multimodality imaging in electrophysiology and cardiac device therapies

Cardiac electrophysiology procedures have evolved to provide improvement in morbidity and mortality for many patients. Cardiac resynchronization therapy (CRT), implantable cardioverter/defibrillator (ICD) placement and lead extraction procedures are proven procedures, associated with significant reductions in patient morbidity and mortality as well as improved quality of life. The applications and optimization of these therapies are an evolving field. The optimal use and outcomes of cardiac electrophysiology procedures require a multidisciplinary approach to patient selection, device selection, and procedural planning. Cardiac imaging using echocardiography plays a key role in selection of patients for CRT therapy, for guidance of left ventricular (LV) lead placement, and for optimization of atrioventricular pacing delays in patients with CRT. Cardiac computed tomography (CT) is an important tool in assessment of lead perforation, as well as assessing risk of lead extraction and procedural planning. Cardiac magnetic resonance imaging (MRI) is an important adjunct to transthoracic echocardiography for patient selection and risk stratification for defibrillator therapy for multiple disease states including ischemic cardiomyopathy, hypertrophic cardiomyopathy, cardiac sarcoidosis, and arrhythmogenic right ventricular cardiomyopathy (ARVC). Cardiac positron emission tomography (PET) is a useful adjunct to the diagnosis of device infections as well as inflammatory conditions including cardiac sarcoidosis. Our review attempts to summarize the contemporary roles of multimodality imaging in CRT therapy, ICD therapy and lead extraction therapy.

Optimized implementation of cardiac resynchronization therapy: a call for action for referral and optimization of care: A joint position statement from the Heart Failure Association (HFA), European Heart Rhythm Association (EHRA), and European Association of Cardiovascular Imaging (EACVI) of the European Society of Cardiology

Cardiac resynchronization therapy (CRT) is one of the most effective therapies for heart failure with reduced ejection fraction and leads to improved quality of life, reductions in heart failure hospitalization rates and all-cause mortality. Nevertheless, up to two-thirds of eligible patients are not referred for CRT. Furthermore, post-implantation follow-up is often fragmented and suboptimal, hampering the potential maximal treatment effect. This joint position statement from three European Society of Cardiology Associations, Heart Failure Association (HFA), European Heart Rhythm Association (EHRA) and European Association of Cardiovascular Imaging (EACVI), focuses on optimized implementation of CRT. We offer theoretical and practical strategies to achieve more comprehensive CRT referral and post-procedural care by focusing on four actionable domains: (i) overcoming CRT under-utilization, (ii) better understanding of pre-implant characteristics, (iii) abandoning the term 'non-response' and replacing this by the concept of disease modification, and (iv) implementing a dedicated post-implant CRT care pathway.

Prevention of non-response to cardiac resynchronization therapy: points to remember

Cardiac resynchronization therapy (CRT) is an important and effective therapy for end-stage heart failure. Non-response to CRT is one of the main obstacles to its application in clinical practice. There is no uniform consensus or definition of CRT “response.” Clinical symptoms, ventricular remodeling indices, and cardiovascular events have been reported to be associated with non-responders. To prevent non-response to CRT, three aspects should be thoroughly considered: preoperative patient selection, electrode implantation, and postoperative management. Preoperative selection of appropriate patients for CRT treatment is an important step in preventing non-response. Currently, the CRT inclusion criteria are mainly based on the morphology of QRS waves in deciding ventricular dyssynchrony. Echocardiography and cardiac magnetic resonance are being explored to predict nonresponse to CRT. The location of left ventricular electrode implantation is a current hot spot of research; it is important to identify the location of the latest exciting ventricular segment and avoid scars. Cardiac magnetic resonance and ultrasonic spot tracking are being progressively developed in this field. Some new techniques such as His Bundle pacing, endocardial electrodes, and novel sensors are also being investigated. Postoperative management of patients is another essential step towards preventing non-response; it mainly focuses on the treatment of the disease itself and CRT program control optimization. CRT treatment is just one part of the overall treatment of heart failure, and multidisciplinary efforts are needed to improve the overall outcome.

Pacing at accelerated heart rate during echocardiography-guided atrioventricular optimisation following cardiac resynchronisation therapy

Introduction

Although echo-guided atrioventricular optimisation (AVO) is standardly performed at rest, this approach may not provide optimal AV synchrony during daily activities.

Material and methods

The AVO protocol at one of two hospital campuses had been modified to be performed while pacing at an accelerated heart rate. We tested if this approach would improve the yield from AVO compared to the other campus, where AVO was performed at the intrinsic sinus rate.

Results

Between campuses, no significant differences were seen in demographics, chamber sizes, left ventricular ejection fraction, and diastolic function grade. Those having AVO at C2 were more likely to demonstrate “fusion prone” physiology (36% vs. 9%; p = 0.006) and were more likely to display either “truncation- or fusion-prone” physiology (58% vs. 27%; p = 0.007).

Conclusions

When AVO was performed at an accelerated heart rate, patients with “truncation-prone” or “fusion-prone” physiology were identified more readily.

Usefulness of Hemodynamic Device-Based Optimization in Heterogeneous Patients Implanted with Cardiac Resynchronization Therapy Defibrillator

Optimization of the atrioventricular (AV) and interventricular (VV) timings of the CRT is the most supposed correctable variable to improve the rate of CRT responder. The aim of the present study has been to evaluate if there is a specific subgroup of patients who can actually benefit the most from a hemodynamic optimization of AV. This is a prospective, observational single-center study that enrolled consecutive patients with clinical indication for CRT; all patients were implanted with CRT-D devices with SonR technology, able to automatically adjust AV and VV delay on a weekly basis. Among 57 patients, 39 (69%) showed a LVESV reduction > 15%. The SonR was able to modify the pacing parameters, but an increase of left atrial diameter was associated to a reduced AV variability, suggesting that an impaired left atrial function could potentially reduce the ability of the SonR algorithm to adjust the correct timing of pacing. Graphical abstract Patients with respectively a high (A) and low (B) AV timing variability, among several parameters that could potentially influence the AV timing, only left atrial dimensions demonstrated a significant impact. In fact an increase of left atrial diameter was associated to a reduced AV variability, suggesting that an impaired left atrial function could potentially reduce the ability of the SonR algorithm to adjust the correct timing of pacing.

Multimodality imaging in the diagnosis, risk stratification, and management of patients with dilated cardiomyopathies: an expert consensus document from the European Association of Cardiovascular Imaging

Dilated cardiomyopathy (DCM) is defined by the presence of left ventricular or biventricular dilatation and systolic dysfunction in the absence of abnormal loading conditions or coronary artery disease sufficient to explain these changes. This is a heterogeneous disease frequently having a genetic background. Imaging is important for the diagnosis, the prognostic assessment and for guiding therapy. A multimodality imaging approach provides a comprehensive evaluation of all the issues related to this disease. The present document aims to provide recommendations for the use of multimodality imaging according to the clinical question. Selection of one or another imaging technique should be based on the clinical condition and context. Techniques are presented with the aim to underscore what is 'clinically relevant' and what are the tools that 'can be used'. There remain some gaps in evidence on the impact of multimodality imaging on the management and the treatment of DCM patients where ongoing research is important.

Non-invasive hemodynamic determination of patient-specific optimal pacing mode in cardiac resynchronization therapy

PURPOSE

Cardiac resynchronization therapy (CRT) devices have multiple programmable pacing parameters. The purpose of this study was to determine the best pacing mode, i.e., associated with the greatest acute hemodynamic response, in each patient.

METHODS

Patients in sinus rhythm and intact atrioventricular conduction were included within 3 months of implantation of devices featuring SyncAV and multipoint pacing (MPP) algorithms. The effect of nominal biventricular pacing using the latest activated electrode (BiV-Late), optimized atrioventricular delay (AVD), nominal and optimized SyncAV, and anatomical MPP was determined by non-invasive measurement of systolic blood pressure (SBP). CRT response was defined as SBP increase > 10% relative to baseline.

RESULTS

Thirty patients with left bundle branch block (LBBB) were included. BiV-Late increased SBP compared to intrinsic rhythm (128 ± 21 mmHg vs. 121 ± 22 mmHg, p = 0.0002). The best pacing mode further increased SBP to 140 ± 19 mmHg (p < 0.0001 vs. BiV-Late). The proportion of CRT responders increased from 40% with BiV-Late to 80% with the best pacing mode (p = 0.0005). Compared to BiV-Late, optimized AVD and optimized SyncAV increased SBP (to 134 ± 21 mmHg, p = 0.004, and 133 ± 20 mmHg, p = 0.0003, respectively), but nominal SyncAV and MPP did not. The best pacing mode was variable between patients and was different from nominal BiV-Late in 28 (93%) patients. Optimized AVD was the most frequent best mode, in 14 (47%) patients.

CONCLUSION

In patients with LBBB, the best pacing mode was patient-specific and doubled the magnitude of acute hemodynamic response and the proportion of acute CRT responders compared to nominal BiV-Late pacing.

TRIAL REGISTRATION

ClinicalTrials.gov : NCT03779802.

Pacemaker-mediated tachycardia in a dual-lead CRT-D: What is the mechanism?

A 73-year-old gentleman with dilated cardiomyopathy, left bundle branch block and a left ventricular (LV) ejection fraction of 20% was implanted with two LV leads in a tri-ventricular cardiac resynchronisation therapy defibrillator (CRT-D) trial. As a part of the trial he was programmed with fusion-based CRT therapy with dual LV lead only pacing. The patient presented to local heart failure service 12 years after implant, after a positive response to CRT therapy, with increase in fatigue, shortness of breath and bilateral pitting oedema. The patient sent a remote monitoring transmission that suggested loss of capture on one of the LV leads. This coupled with atrial ectopics was producing a high burden of pacemaker-mediated tachycardia (PMT) that was not seen when both LV leads had been capturing. What is the mechanism for this? Dual LV-lead tri-ventricular leads have been shown to have variable improvements in CRT response but with an increased complexity of implant procedure. This is the first case report of PMT-induced heart failure exacerbation in a tri-ventricular device following loss of LV capture of one lead.

Noninvasive cardiac output measurement based optimization in nonresponders of cardiac resynchronization therapy

BACKGROUND

Cardiac resynchronization therapy (CRT) is an important and effective therapy for end-stage heart failure (HF). Nonresponse to CRT is one of the main obstacles to its application in clinical practice. Herein, we investigated the utilization of the optimization technique using noninvasive cardiac output measurement (NICOM) based Mobil-O-Graph device that measures several circulation parameters noninvasively.

METHODS

Seventy-five CRT nonresponder HF patients with an implanted CRT device were included. Patients were randomized equally to 3 groups: NICOM, echocardiographic, and empirical optimization groups. After 3 months of optimization, changes in six minutes walk test (6-MWT), cardiac output (CO), left ventricular ejection fraction (LVEF), and end-systolic volume (LVESV) were measured. New York Heart Association (NYHA) class and hospitalization for HF were also determined.

RESULTS

There were no statistically significant differences among the three groups in terms of demographics, baseline characteristics. In the NICOM group, the 6-MWT, LVEF, CO, and LVESV measurements showed significant improvements compared to baseline values (P < .05). There was no significant improvement in 6-MWT, LVEF, CO, NYHA class, and LVESV in Echo and Empirical groups after 3 months (P > .05). 6-MWT, CO, LVESV percentages, and hospitalization for HF were significantly different between the groups (P < .05). In post hoc analyzes, the percentages of the change in 6-MWT, CO, LVESV, and hospitalization for HF were significantly higher in the NICOM group (P < .017).

CONCLUSIONS

This study suggests that Mobil-O-Graph device optimization according to CO measures does appear to have potential hemodynamic and clinical benefits in nonresponder CRT patients. Use of Mobil-O-Graph device as an option for optimization of CRT devices can be an attractive method of improving CRT outcomes.

Real-world behavior of CRT pacing using the AdaptivCRT algorithm on patient outcomes: Effect on mortality and atrial fibrillation incidence

Background

The AdaptivCRT (aCRT) algorithm continuously adjusts cardiac resynchronization therapy (CRT) according to intrinsic atrioventricular conduction, providing synchronized left ventricular pacing in patients with normal PR interval and adaptive BiV pacing in patients with prolonged PR interval. Previous analyses demonstrated an association between aCRT and clinical benefit. We evaluated the incidence of patient mortality and atrial fibrillation (AF) with aCRT compared with standard CRT in a real‐world population.

Methods and Results

Patients enrolled in the Medtronic Personalized CRT Registry and implanted with a CRT from 2013‐2018 were divided into aCRT ON or standard CRT groups based upon device‐stored data. A Frailty survival model was used to evaluate the potential survival benefit of aCRT, accounting for patient heterogeneity and center variability. Daily AF burden and first device‐detected AF episodes of various durations were recorded by the device during follow‐up.

A total of 1814 CRT patients with no reported long‐standing AF history at implant were included. Mean follow‐up time was 26.1 ± 16.5 months and 1162 patients (64.1%) had aCRT ON. Patient survival probability at 36 months was 88.3% for aCRT ON and 83.7% for standard CRT (covariate‐adjusted hazard ratio [HR] = 0.71, 95% CI: 0.53‐0.96, P = .028). Mean AF burden during follow‐up was consistently lower in aCRT ON patients compared with standard CRT. At 36 months, the probability of AF was lower in patients with aCRT ON, regardless of which AF definition threshold was applied (6 minutes‐30 days, all P < .001).

Conclusion

Use of the AdaptivCRT algorithm was associated with improved patient survival and lower incidence of AF in a real‐world, prospective, nonrandomized registry.

Long-term follow-up after cardiac resynchronization therapy-optimization in a real-world setting: A single-center cohort study

BACKGROUND

Suboptimal device programming is among the reasons for reduced response to cardiac resynchronization therapy (CRT). However, whether systematic optimization is beneficial remains unclear, particularly late after CRT implantation. The aim of this single-center cohort study was to assess the effect of systematic atrioventricular delay (AVD) optimization on echocardiographic and device parameters.

METHODS

Patients undergoing CRT optimization at the University Hospital Zurich between March 2011 and January 2013, for whom a follow-up was available, were included. AVD optimization was based on 12-lead electrocardiography (ECG) and echocardiographic left ventricular inflow characteristics. Parameters were assessed at the time of CRT optimization and follow-up, and were compared between patients with AVD optimization (intervention group) and those for whom no AVD optimization was deemed necessary (control group).

RESULTS

Eighty-one patients with a mean age of 64 ± 11 years were included in the analysis. In 73% of patients, AVD was deemed suboptimal and was changed accordingly. After a median follow-up time of 10.4 (IQR 6.2 to 13.2) months, the proportion of patients with sufficient biventricular pacing (> 97% pacing) was greater in the intervention group (78%) compared to controls (50%). Furthermore, AVD adaptation was associated with an improvement in interventricular mechanical delay (decrease of 6.6 ± 26.2 ms vs. increase of 4.3 ± 17.7 ms, p = 0.034) and intraventricular septal-to-lateral delay (decrease of 0.9 ± 48.1 ms vs. increase of 15.9 ± 15.7 ms, p = 0.038), as assessed by tissue Doppler imaging. Accordingly, a reduction was observed in mitral regurgitation along with a trend towards reduced left ventricular volumes.

CONCLUSIONS

In this "real-world" setting systematic AVD optimization was associated with beneficial effects regarding biventricular pacing and left ventricular remodeling. These data show that AVD optimization may be advantageous in selected CRT patients.

Cardiac Strains As a Tool for Optimization of Cardiac Resynchronization Therapy in Non-responders: a Pilot Study

Background

Approximately 30% of patients do not respond to implantation of Cardiac Resynchronization Therapy – Defibrillators (CRT-D). The aim of this study was to investigate the potential for cardiac strain speckle tracking to optimize the performance of CRT-D in non-responding patients.

Methods

30 patients not responding to Cardiac Resynchronization Therapy-Defibrillators after 3 months were randomly divided into control and intervention groups. Atrioventricular interval was adjusted so that E and A waves did not overlap, the interventricular interval was subsequently optimized to yield maximum improvement of the sum of longitudinal+radial+circumferential strains. The left ventricular ejection fraction (LVEF) and NYHA improvement 3 months after optimization were evaluated and use of other strain combinations assessed.

Results

A significant correlation between the (combined) strain change and LVEF improvement was detected (p<0.01). 75% of patients with non-ischemic etiology of heart failure who did not respond to the original CRT-D reacted favorably with significant LVEF and NYHA improvement. The area strain was the best predictor of LVEF/NYHA improvement in those patients. No significant improvement was recorded in patients with ischemic etiology.

Conclusions

AV and VV optimization based on speckle tracking is a very promising method potentially leading to a significant improvement of the outcome of CRT-D, especially in patients with non-ischemic etiology of heart failure.

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.

Comparison of measures of ventricular delay on cardiac resynchronization therapy response

BACKGROUND

Left ventricular (LV) pacing at sites of prolonged LV delay (QLV) or at long interventricular delay (right ventricle [RV]-LV) is strongly associated with cardiac resynchronization therapy (CRT) response. QLV and RV-LV have been independently evaluated, but little is known regarding the interrelationship between these measures or of delay to the RV.

OBJECTIVE

The purpose of this study was to evaluate the relationship between measures of electrical delay on CRT response in the SMART-AV (SmartDelay Determined AV Optimization: A Comparison to Other AV Delay Methods Used in Cardiac Resynchronization Therapy) trial.

METHODS

In 419 patients, QLV and RV-LV were measured. CRT response was defined as a >15% reduction in LV end-systolic volume from implant to 6 months. The correlation between QLV and RV-LV and the clinical variables associated with the difference between QLV and RV-LV (QRV) were determined. Multivariable logistic regression was used to analyze the association between these measures on CRT response. A machine learning algorithm was used to construct a classification tree to predict response to CRT.

RESULTS

The cohort was 66% male (age 66 ± 11 years), 75% had left bundle branch block; and QRS was 150 ± 25 ms. QLV and RV-LV were highly correlated (R² = 0.71). A longer QRV was observed among patients with right bundle branch block, ischemic cardiomyopathy, and increased QRS. In a multivariable model including QLV, RV-LV, and other known predictors of CRT response, RV-LV, but not QLV, remained associated with CRT response (odds ratio 1.13; 95% confidence interval 1.02-1.26; P = .017). Combining the 2 measures achieved better prediction of CRT response in the group with intermediate RV-LV.

CONCLUSION

RV-LV is a better predictor of CRT response than QLV. There is incremental value in using both measurements or QRV in certain subpopulations.

The effect of posture, exercise, and atrial pacing on atrioventricular conduction in systolic heart failure

BACKGROUND

Optimization of atrioventricular (AV) intervals for cardiac resynchronization therapy (CRT) programming is typically performed in supine patients at rest, which may not reflect AV timing in other conditions.

OBJECTIVE

To evaluate the effects of posture, exercise, and atrial pacing on intrinsic AV intervals in patients with CRT devices.

METHODS

Rate-dependent A-V delay by exercise was a multicenter, prospective trial of patients in sinus rhythm following CRT implantation. Intracardiac electrograms were recorded to analyze atrial to right ventricular (ARV), atrial to left ventricular (ALV), and RV to LV (VV) time intervals. Heart rate was increased with incremental atrial pacing in different postures, followed by an exercise treadmill test.

RESULTS

This study included 36 patients. At rest, AV intervals changed minimally with posture. With atrial pacing, AV interval immediately increased compared with sinus rhythm, with ARV slopes being 8.1 ± 7.7, 8.8 ± 13.4, and 6.8 ± 6.5 milliseconds per beat per minute (ms/bpm) and ALV slopes being 8.2 ± 7.7, 9.1 ± 12.8, and 7.0 ± 6.5 ms/bpm for supine, standing and sitting positions, respectively. As the paced heart rate increased, ARV and ALV intervals increased more gradually with similar trends. Interventricular conduction times changed less than 0.2 ms/bpm with atrial pacing. During exercise, the direction of change of intrinsic ARV intervals, as heart rate increased, was variable between patients with relatively small overall group changes (0.1 ± 1.4 and 0.2 ± 1.2 ms/bpm for ARV and ALV, respectively).

CONCLUSION

Posture and exercise have a smaller effect on AV timing compared with atrial pacing. However, individualized optimization and dynamic rate related changes may be needed to maintain optimal fusion with left ventricular (LV) stimulation.

Design and rationale for the Stimulation Of the Left Ventricular Endocardium for Cardiac Resynchronization Therapy in non-responders and previously untreatable patients (SOLVE-CRT) trial

BACKGROUND

Cardiac resynchronization therapy (CRT) improves outcomes, functional capacity and quality of life in patients with heart failure. Despite two decades of experience with CRT, the rate of non-response remains approximately 30%. CRT efficacy is impacted by pacing location, which is anatomically limited in conventional systems. A new wireless endocardial left ventricular (LV) pacing system allows CRT without such limitations and has shown promise in open-label studies. The purpose of this study is to evaluate its use in a patient population with poor therapeutic alternatives.

METHODS

The SOLVE CRT study is an international, multi-center, randomized, double-blind, sham-controlled trial of patients with Class I and IIa indications for CRT who have either failed to respond to or have been unable to receive conventional CRT. Enrollment will comprise 350 patients implanted with the wireless CRT system randomized 1:1 to therapy on (Treatment) or therapy off (Control) for the six-month period over which trial primary endpoints will be evaluated. The primary safety endpoint will measure the proportion of patients free from system- and procedure-related complications. Primary efficacy endpoints will assess absolute change in LV end-systolic volume LVESV, proportion of patients reducing LVESV by ≥15% and clinical composite score for Treatment versus Control patients. Primary endpoints will be evaluated on an intention-to-treat basis, though per-protocol and as-treated analysis will also be performed.

CONCLUSION

SOLVE-CRT will quantify the safety and effectiveness of wireless CRT in non-responders to conventional CRT and indicated patients who have been unable to receive CRT via the usual transvenous approach.

Novel Device-Based Algorithm Provides Optimal Hemodynamics During Exercise in Patients With Cardiac Resynchronization Therapy

BACKGROUND

An adaptive cardiac resynchronization therapy (aCRT) algorithm has been described for synchronized left ventricular (LV) pacing and continuous optimization of cardiac resynchronization therapy (CRT). However, there are few algorithmic data on the effect of changes during exercise.

METHODS AND RESULTS

We enrolled 27 patients with availability of the aCRT algorithm. Eligible patients were manually programmed to optimal atrioventricular (AV) and interventricular (VV) delays by using echocardiograms at rest or during 2 stages of supine bicycle exercise. We compared the maximum cardiac output between manual echo-optimization and aCRT-on during each phase. After initiating exercise, the optimal AV delay progressively shortened (P<0.05) with incremental exercise levels. The manual-optimized settings and aCRT resulted in similar cardiac performance, as demonstrated by a high concordance correlation coefficient between the LV outflow tract velocity time integral (LVOT-VTI) during each exercise stage (Ex.1: r=0.94 P<0.0008, Ex.2: r=0.88 P<0.001, respectively). Synchronized LV-only pacing in patients with normal AV conduction could provide a higher LVOT-VTI as compared with manual-optimized conventional biventricular pacing at peak exercise (P<0.05).

CONCLUSIONS

The aCRT algorithm was physiologically sound during exercise by patients.

Optimized adaptive enrichment designs for three-arm trials: learning which subpopulations benefit from different treatments

We consider the problem of designing a confirmatory randomized trial for comparing two treatments versus a common control in two disjoint subpopulations. The subpopulations could be defined in terms of a biomarker or disease severity measured at baseline. The goal is to determine which treatments benefit which subpopulations. We develop a new class of adaptive enrichment designs tailored to solving this problem. Adaptive enrichment designs involve a preplanned rule for modifying enrollment based on accruing data in an ongoing trial. At the interim analysis after each stage, for each subpopulation, the preplanned rule may decide to stop enrollment or to stop randomizing participants to one or more study arms. The motivation for this adaptive feature is that interim data may indicate that a subpopulation, such as those with lower disease severity at baseline, is unlikely to benefit from a particular treatment while uncertainty remains for the other treatment and/or subpopulation. We optimize these adaptive designs to have the minimum expected sample size under power and Type I error constraints. We compare the performance of the optimized adaptive design versus an optimized nonadaptive (single stage) design. Our approach is demonstrated in simulation studies that mimic features of a completed trial of a medical device for treating heart failure. The optimized adaptive design has $25\%$ smaller expected sample size compared to the optimized nonadaptive design; however, the cost is that the optimized adaptive design has $8\%$ greater maximum sample size. Open-source software that implements the trial design optimization is provided, allowing users to investigate the tradeoffs in using the proposed adaptive versus standard designs.

Devices in Heart Failure Patients-Who Benefits From ICD and CRT?

Despite advances in heart failure treatment, this condition remains a relevant medical issue and is associated with a high morbidity and mortality. The cause of death in patients suffering from heart failure is not only a result of hemodynamic failure, but can also be due to ventricular arrhythmias. Implantable cardioverter defibrillators (ICDs) are these days the only tool to significantly reduce arrhythmic sudden death; but not all patients benefit to the same extend. In addition, cardiac resynchronization therapy (CRT) is another tool which is used in patients suffering from heart fialure. Even though both devices have been investigated in large randomized trials, both ICD and CRT remain underutilized in many countries. This brief review focuses on various aspects in this regard including a short overview on upcoming device novelties in the near future.

Improving Cardiac Resynchronisation Therapy

CRT is a cornerstone of therapy for patients with heart failure and reduced ejection fraction. By restoring left ventricular (LV) electrical and mechanical synchrony, CRT can reduce mortality, improve LV function and reduce heart failure symptoms. Since its introduction, many advances have been made that have improved the delivery of and enhanced the response to CRT. Improving CRT outcomes begins with proper patient selection so CRT is delivered to all populations that could benefit from it, and limiting the implantation of CRT in those with a small chance of response. In addition, advancements in LV leads and delivery technologies coupled with multimodality imaging and electrical mapping have enabled operators to place coronary sinus leads in locations that will optimise electrical and mechanical synchrony. Finally, new pacing strategies using LV endocardial pacing or His bundle pacing have allowed for CRT delivery and improved response in patients with poor coronary sinus anatomy or lack of response to traditional CRT.

CRT Optimization: What Is New? What Is Necessary?

Cardiac resynchronization therapy (CRT) has proven to improve quality of life, reduce heart failure hospitalization, and prolong life in selected heart failure patients with reduced ejection fraction, on optimal medical therapy and with electrical dyssynchrony. To ensure maximal benefit for CRT patients, optimization of care should be implemented. This begins with appropriate referring as well as selecting patients, knowing that the presence of left bundle branch block and QRS ≥ 150 ms is associated with the greatest reverse remodeling. The LV lead, preferably quadripolar, is best targeted in a postero-lateral position. After implantation, optimal device programming should aim for maximal biventricular pacing and in selected cases further electrical delay optimization might be of use. Even as important, is the implementation of thorough multidisciplinary heart failure care with medication uptitration, remote monitoring, rehabilitation, and patient education. The role of newer pacing strategies as endocardial or His-bundle pacing remains the subject of ongoing investigation.

Efficacy of Cardiac Resynchronization Therapy Using Automated Dynamic Optimization and Left Ventricular-only Pacing

BACKGROUND

Although device-based optimization has been developed to overcome the limitations of conventional optimization methods in cardiac resynchronization therapy (CRT), few real-world data supports the results of clinical trials that showed the efficacy of automatic optimization algorithms. We investigated whether CRT using the adaptive CRT algorithm is comparable to non-adaptive biventricular (BiV) pacing optimized with electrocardiogram or echocardiography-based methods.

METHODS

Consecutive 155 CRT patients were categorized into 3 groups according to the optimization methods: non-adaptive BiV (n = 129), adaptive BiV (n = 11), and adaptive left ventricular (LV) pacing (n = 15) groups. Additionally, a subgroup of patients (n = 59) with normal PR interval and left bundle branch block (LBBB) was selected from the non-adaptive BiV group. The primary outcomes included cardiac death, heart transplantation, LV assist device implantation, and heart failure admission. Secondary outcomes were electromechanical reverse remodeling and responder rates at 6 months after CRT.

RESULTS

During a median 27.5-month follow-up, there was no significant difference in primary outcomes among the 3 groups. However, there was a trend toward better outcomes in the adaptive LV group compared to the other groups. In a more rigorous comparisons among the patients with normal PR interval and LBBB, similar patterns were still observed.

CONCLUSION

In our first Asian-Pacific real-world data, automated dynamic CRT optimization showed comparable efficacy to conventional methods regarding clinical outcomes and electromechanical remodeling.

Long-Term Effect of Different Optimizing Methods for Cardiac Resynchronization Therapy in Patients with Heart Failure: A Randomized and Controlled Pilot Study

AIM

During cardiac resynchronization therapy (CRT), optimized programming of the atrioventricular (AV) delay and ventricular-to-ventricular (VV) interval can lead to improved hemodynamics, symptomatic response, and left ventricular systolic function. Currently, however, there is no recommendation for the best optimization method. This study aimed to compare the long-term clinical outcomes of 4 different CRT optimization methods.

METHODS

One hundred and twenty-four consecutive CRT patients with severe heart failure and left bundle-branch block configuration were randomly assigned into four groups to undergo AV/VV delay optimization through echocardiogram (ECHO; n = 30), electrocardiogram (ECG; n = 32), QuickOpt algorithm (n = 28), and nominal AV/VV (n = 36) groups. Patients were followed up and underwent examinations, including New York Heart Association (NYHA) cardiac functional classification, 6-min walking distance (6MWD), and echocardiography, at 6, 12, 24, 36, and 48 months, respectively. The patients' survival and clinical outcomes were compared among the four groups.

RESULTS

Kaplan-Meier survival analyses showed that the median survival was the same in the 4 groups: ECHO, 43 months; ECG, 44 months; QuickOpt, 44 months, and nominal, 41 months. At the 6-month follow-up, the reduction in left ventricular end diastolic diameter (LVEDD) was significantly less in the nominal group (-1.91 ± 2.58 mm) than that in the other three groups (ECHO: -3.70 ± 2.78 mm, p = 0.012; ECG: -3.53 ± 3.14 mm, p = 0.020; QuickOpt: -3.46 ± 2.65 mm, p = 0.032); 6MWD was significantly shorter in the nominal group (87.88 ± 34.76 m) than that in the other three groups (ECHO: 120.63 ± 56.93 m, p = 0.006; ECG: 114.97 ± 54.95 m, p = 0.020; QuickOpt: 114.57 ± 35.41 m, p = 0.027). Left ventricular ejection fraction (LVEF) significantly increased in ECHO (7.23 ± 2.76%, p = 0.010), ECG (8.50 ± 3.17%, p < 0.001), and QuickOpt (8.39 ± 2.90%, p < 0.001) compared with the nominal group (5.35 ± 2.59%). There were no significant differences among the groups in the aforementioned parameters at 24, 36, and 48 months, respectively.

CONCLUSION

While LVEDD, LVEF, 6MWD, and NYHA were significantly improved in ECHO, ECG, and QuickOpt at 6 months, there were no significant improvements in any of the groups at 12, 24, and 48 months. These findings suggested that the long-term effect of the four CRT methods for heart failure was not significantly different.

How to maximize QRS narrowing

BACKGROUND

Cardiac resynchronization therapy (CRT) resulting in maximal QRS narrowing may be associated with improved outcomes.

METHODS

Various atrioventricular (AV) delay settings, including the new SyncAV™ algorithm (St. Jude Medical/Abbott, St. Paul, MN, USA), aimed at maximal QRS narrowing were tested in an 81-year old CRT recipient.

RESULTS

Maximal QRS narrowing from 160 to 100 ms was achieved with a manually programmed value of SyncAV™ -30 ms. At 2 months, the patient proved to be a CRT super-responder.

CONCLUSION

SyncAV™ algorithm is a new way for effective QRS narrowing with potentially improved outcomes.

Change in indication for cardiac resynchronization therapy?

Cardiac resynchronization therapy (CRT) has rapidly evolved as a standard therapy for heart failure (HF) patients with ventricular conduction delay. Although in early trials, only patients with sinus rhythm and advanced stages of HF have been candidates for CRT, more recent data have expanded the indications to patients with mild-to-moderate HF and atrial fibrillation and patients in need of antibradycardia pacing with reduced left ventricular function. On the other hand, it is now well recognized that patients with a wide QRS (>150 ms) and left bundle branch block morphology benefit most from CRT, whereas in patients with a more narrow QRS complex (<130 ms) CRT may actually be harmful despite the evidence of ventricular dyssynchrony by echocardiography. There is no prospective randomized study showing mortality benefit from a combined CRT defibrillating device over a CRT pacer alone. This is especially important because recent data indicate that older patients with non-ischaemic cardiomyopathy may not benefit from the implantable cardioverter-defibrillator as much as previously thought. Thus, the decision for a CRT pacer versus CRT defibrillating should be tailored to the therapeutic goal (improvement in prognosis versus symptomatic relief), patient age, underlying cardiac disease and comorbidities. This article gives an overview over the current indications for CRT according to published literature and the European guidelines for pacing and HF.

Non-response to Cardiac Resynchronization Therapy

PURPOSE OF REVIEW

Cardiac resynchronization therapy (CRT) is an effective treatment option for therapy-refractory mild to severe heart failure (HF) patients with reduced ejection fraction and left ventricular (LV) conduction delay. Multiple clinical trials have shown that CRT improves cardiac function and overall quality of life, as well as reduces HF hospitalizations, health care costs, and mortality.

RECENT FINDINGS

Despite its effectiveness, the "non-response" rate to CRT is around 30%, remaining a major challenge that faces electrophysiologists and researchers. It has been recently suggested that the etiology of CRT non-response is multifactorial, and it requires a multifaceted approach to address it. In this focused review, we will summarize the definitions of CRT non-response, identify key factors for CRT non-response, and offer a simplified framework to address CRT non-response with the main goal of improving CRT outcomes.

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.

Optimization of CRT programming using non-invasive electrocardiographic imaging to assess the acute electrical effects of multipoint pacing

AIM

Quadripolar lead technology and multi-point pacing (MPP) are important clinical adjuncts in cardiac resynchronization therapy (CRT) pacing aimed at reducing the rate of non-response to therapy. Mixed results have been achieved using MPP and it is critical to identify which patients require this approach and how to configure their MPP stimulation, in order to achieve optimal electrical resynchronization.

METHODS & RESULTS

We sought to investigate whether electrocardiographic imaging (ECGi), using the CARDIOINSIGHT ™ inverse ECG mapping system, could identify alterations in electrical resynchronization during different methods of device optimization. In no patient did a single form of programming optimization provide the best electrical response. The effects of utilizing MPP were idiosyncratic and highly patient specific. ECGi activation maps were clearly able to discern changes in bulk LV activation during differing MPP programming. In two of the five subjects, MPP resulted in more rapid activation of the left ventricle compared to standard CRT; however, in the remaining three patients, the use of MPP did not appear to acutely improve electrical resynchronization. Crucially, this cohort showed evidence of extensive LV scarring which was well visualized using both CMR and ECGi voltage mapping.

CONCLUSIONS

Our work suggests a potential role for ECGi in the optimization of non-responders to CRT, as it allows the fusion of activation maps and scar analysis above and beyond interrogation of the 12 lead ECG.

Statistical ranking of electromechanical dyssynchrony parameters for CRT

Objective

Mechanical evaluation of dyssynchrony by echocardiography has not replaced ECG in routine cardiac resynchronisation therapy (CRT) evaluation because of its complexity and lack of reproducibility. The objective of this study was to evaluate the potential correlations between electromechanical parameters (atrioventricular, interventricular and intraventricular from the dyssynchrony model presented in 2000), their ability to describe dyssynchrony and their potential use in resynchrony.

Methods

455 sets of the 18 parameters of the model obtained in 91 patients submitted to various pacing configurations were evaluated two by two using a Pearson correlation test and then by groups according to their ability to describe dyssynchrony, using the Column selection method of machine learning.

Results

The best parameter is duration of septal contraction, which alone describes 25% of dyssynchrony. The best groups of 3, 4 and ≥8 variables describe 59%, 73% and almost 100% of dyssynchrony, respectively. Left pre-ejection interval is highly and significantly correlated to a maximum of other variables, and its decrease is associated with the favourable evolution of all other correlated parameters. Increase in filling duration and decrease in duration of septum to lateral wall contraction difference are not associated with the favourable evolution of other parameters.

Conclusions

No single electromechanical parameter alone can fully describe dyssynchrony. The 18-parameter model can be simplified, but still requires at least 4-8 parameters. Decrease in left pre-ejection interval favourably drives resynchrony in a maximum of other parameters. Increase in filling duration and decrease in septum-lateral wall difference do not appear to be good CRT targets.

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.

Understanding non-response to cardiac resynchronisation therapy: common problems and potential solutions

Heart failure is a complex clinical syndrome associated with a significant morbidity and mortality burden. Reductions in left ventricular (LV) function trigger adaptive mechanisms, leading to structural changes within the LV and the potential development of dyssynchronous ventricular activation. This is the substrate targeted during cardiac resynchronisation therapy (CRT); however, around 30-50% of patients do not experience benefit from this treatment. Non-response occurs as a result of pre-implant, peri-implant and post implant factors but the technical constraints of traditional, transvenous epicardial CRT mean they can be challenging to overcome. In an effort to improve response, novel alternative methods of CRT delivery have been developed and of these endocardial pacing, where the LV is stimulated from inside the LV cavity, appears the most promising.

Development of a biomarker panel to predict cardiac resynchronization therapy response: Results from the SMART-AV trial

BACKGROUND

Predicting a favorable cardiac resynchronization therapy (CRT) response holds great clinical importance.

OBJECTIVE

The purpose of this study was to examine proteins from broad biological pathways and develop a prediction tool for response to CRT.

METHODS

Plasma was collected from patients before CRT (SMART-AV [SmartDelay Determined AV Optimization: A Comparison to Other AV Delay Methods Used in Cardiac Resynchronization Therapy] trial). A CRT response was prespecified as a ≥15-mL reduction in left ventricular end-systolic volume at 6 months, which resulted in a binary CRT response (responders 52%, nonresponders 48%; n = 758).

RESULTS

Candidate proteins (n = 74) were evaluated from the inflammatory, signaling, and structural domains, which yielded 12 candidate biomarkers, but only a subset of these demonstrated predictive value for CRT response: soluble suppressor of tumorgenicity-2, soluble tumor necrosis factor receptor-II, matrix metalloproteinase-2, and C-reactive protein. These biomarkers were used in a composite categorical scoring algorithm (Biomarker CRT Score), which identified patients with a high/low probability of a response to CRT (P <.001) when adjusted for a number of clinical covariates. For example, a Biomarker CRT Score of 0 yielded 5 times higher odds of a response to CRT compared to a Biomarker CRT Score of 4 (P <.001). The Biomarker CRT Score demonstrated additive predictive value when considered against a composite of clinical variables.

CONCLUSION

These unique findings demonstrate that developing a biomarker panel for predicting individual response to CRT is feasible and holds potential for point-of-care testing and integration into evaluation algorithms for patients presenting for CRT.

Galectin-3 predicts response and outcomes after cardiac resynchronization therapy

BACKGROUND

Cardiac resynchronization therapy (CRT) reduces symptoms, morbidity and mortality in chronic heart failure patients with wide QRS complexes. However, approximately one third of CRT patients are non-responders. Myocardial fibrosis is known to be associated with absence of response. We sought to see whether galectin-3, a promising biomarker involved in fibrosis processes, could predict response and outcomes after CRT.

METHODS

Consecutive patients eligible for implantation of a CRT device with a typical left bundle branch block ≥ 120 ms were prospectively included. Serum Gal-3 level, Selvester ECG scoring, and cardiac magnetic resonance with analysis of late gadolinium enhancement (LGE) were ascertained. Response to CRT was defined by a composite endpoint at 6 months: no death, nor hospitalization for major cardiovascular event, and a significant decrease in left ventricular end-systolic volume of 15% or more.

RESULTS

Sixty-one patients were included (age 61 ± 5 years, ejection fraction 27 ± 5%), 59% with non-ischemic cardiomyopathy. At 6 months, 49 patients (80%) were considered responders. Responders had a lower percentage of LGE (8 ± 13% vs 22 ± 16%, p = 0.006), and a trend towards lower rates of galectin-3 (16 ± 6 ng/mL vs 19 ± 8 ng/mL, p = 0.13). LGE ≥ 14% and Gal-3 ≥ 22 ng/mL independently predicted response to CRT (OR = 0.17 [0.03-0.62], p = 0.007, and OR = 0.11 [0.02-0.04], p < 0.001, respectively). At 48 months of follow-up, 12 patients had been hospitalized for a major cardiovascular event or had died. Galectin-3 level predicted long-term outcomes (HR = 3.31 [1.00-11.34], p = 0.05).

CONCLUSIONS

Gal-3 serum level predicts the response to CRT at 6 months and long-term outcomes in chronic heart failure patients.

Cardiac resynchronization therapy: a comprehensive review

Despite improved understanding of heart failure (HF) and advances in medical treatments, its prevalence continues to rise, and the role of implantable devices continues to evolve. While cardiac resynchronization therapy (CRT) is an accepted form of treatment for many suffering from HF, there is an ever-evolving body of evidence examining novel indications, optimization of lead placement and device programming, with several competing technologies now also on the horizon. This review aims to take a clinical perspective on the major trials, current indications, controversies and emerging aspects of CRT in the treatment of HF.

Vectorcardiographic QRS area is associated with long-term outcome after cardiac resynchronization therapy

BACKGROUND

Recent studies have suggested that vectorcardiographic measures predict left ventricular (LV) reverse remodeling and clinical outcome in patients receiving cardiac resynchronization therapy (CRT).

OBJECTIVES

The objectives of this study were to compare predictive abilities of different vectorcardiographic measures (QRS area and sum absolute QRS-T integral) and transformation methods (Kors and inverse Dower) and to assess the independent association between the best predictor and outcomes in CRT recipients.

METHODS

This retrospective study included CRT recipients with a digital baseline electrocardiogram, QRS duration ≥120 ms, and ejection fraction ≤35%. The end point was a composite of heart transplantation, LV assist device implantation, or all-cause death. Analyses were performed for the overall cohort and for a prespecified subgroup of patients with left bundle branch block (LBBB).

RESULTS

Of 705 included patients with a mean age of 66.6 ± 11.5 years, 492 (70%) were men, 374 (53%) had ischemic heart disease, and 465 (66%) had LBBB. QRS area from vectorcardiograms derived via the Kors transformation demonstrated the best predictive value. In multivariable Cox regression, patients with a smaller QRS area (≤ 95 μVs) had an increased hazard in the overall cohort (adjusted hazard ratio 1.65; 95% CI 1.25-2.18 P < .001) and in the LBBB subgroup (adjusted hazard ratio 1.95; 95% CI 1.38-2.76 P < .001). QRS area was associated with outcome in patients with QRS duration <150 ms (unadjusted hazard ratio 3.85; 95% CI 2.02-7.37 P < .001) and in patients with QRS duration ≥150 ms (unadjusted hazard ratio 1.76; 95% CI 1.32-2.34 P < .001).

CONCLUSION

Vectorcardiographic QRS area is associated with survival free from heart transplantation and LV assist device implantation in CRT recipients.

Effect of Interventricular Electrical Delay on Atrioventricular Optimization for Cardiac Resynchronization Therapy

BACKGROUND

Routine atrioventricular optimization (AVO) has not been shown to improve outcomes with cardiac resynchronization therapy (CRT). However, more recently subgroup analyses of multicenter CRT trials have identified electrocardiographic or lead positions associated with benefit from AVO. Therefore, the purpose of this analysis was to evaluate whether interventricular electrical delay modifies the impact of AVO on reverse remodeling with CRT.

METHODS

This substudy of the SMART-AV trial (SMARTDELAY Determined AV Optimization) included 275 subjects who were randomized to either an electrogram-based AVO (SmartDelay) or nominal atrioventricular delay (120 ms). Interventricular delay was defined as the time between the peaks of the right ventricular (RV) and left ventricular (LV) electrograms (RV-LV duration). CRT response was defined prospectively as a >15% reduction in LV end-systolic volume from implant to 6 months.

RESULTS

The cohort was 68% men, with a mean age of 65±11 years and LV ejection fraction of 28±8%. Longer RV-LV durations were significantly associated with CRT response ( P<0.01) for the entire cohort. Moreover, the benefit of AVO increased as RV-LV duration prolonged. At the longest quartile, there was a 4.26× greater odds of a remodeling response compared with nominal atrioventricular delays ( P=0.010).

CONCLUSIONS

Baseline interventricular delay predicted CRT response. At long RV-LV durations, AVO can increase the likelihood of reverse remodeling with CRT. AVO and LV lead location optimized to maximize interventricular delay may work synergistically to increase CRT response.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov . Unique identifier: NCT00874445.

Optimal site selection and image fusion guidance technology to facilitate cardiac resynchronization therapy

INTRODUCTION

Cardiac resynchronization therapy (CRT) has emerged as one of the few effective treatments for heart failure. However, up to 50% of patients derive no benefit. Suboptimal left ventricle (LV) lead position is a potential cause of poor outcomes while targeted lead deployment has been associated with enhanced response rates. Image-fusion guidance systems represent a novel approach to CRT delivery, allowing physicians to both accurately track and target a specific location during LV lead deployment.

AREAS COVERED

This review will provide a comprehensive evaluation of how to define the optimal pacing site. We will evaluate the evidence for delivering targeted LV stimulation at sites displaying favorable viability or advantageous mechanical or electrical properties. Finally, we will evaluate several emerging image-fusion guidance systems which aim to facilitate optimal site selection during CRT.

EXPERT COMMENTARY

Targeted LV lead deployment is associated with reductions in morbidity and mortality. Assessment of tissue characterization and electrical latency are critical and can be achieved in a number of ways. Ultimately, the constraints of coronary sinus anatomy have forced the exploration of novel means of delivering CRT including endocardial pacing which hold promise for the future of CRT delivery.

The rationale and design of the SMART CRT trial

AIMS

The SMART CRT study will assess the efficacy of an atrioventricular optimization algorithm to improve reverse remodeling among patients undergoing cardiac resynchronization therapy (CRT) in the presence of interventricular electrical delay.

METHODS AND RESULTS

The SMART CRT study is a global, multicenter, prospective, randomized study of patients undergoing CRT implantation. The primary endpoint of this trial is response rate to CRT, defined as decrease in left ventricular end-systolic volume (LVESV) ≥15% at 6 months compared to preimplant baseline. Additional prespecified analyses are: (1) clinical composite endpoint combining all-cause mortality, heart failure events, New York Heart Association class, and Quality of Life (using a patient global assessment instrument); (2) the individual components of the clinical composite endpoint; (3) 6-minute walk distance; (4) Kansas City Cardiomyopathy Questionnaire; (5) LVESV as a continuous variable; and (6) absolute left-ventricular ejection fraction. Subjects with intraventricular delay ≥ 70 ms measured between the right ventricular and left ventricular pacing leads will be randomized in a 1:1 ratio to have either an AV Delay and pacing chamber determined by SmartDelay™ or a Fixed AV Delay of 120 ms with biventricular pacing. Enrollment of an estimated 726 of subjects from up to 100 centers worldwide is planned to achieve 436 randomized subjects and 370 complete data sets required to power the primary endpoint.

CONCLUSIONS

This trial will provide important data regarding the importance of AV Delay programming in patients with prolonged interventricular delay at the pacing sites.