Adaptive CRT in patients with normal AV conduction and left bundle branch block: Does QRS duration matter?

Atrioventricular optimization improves cardiac resynchronization response in patients with long interventricular electrical delays: A pooled analysis of the SMART-AV and SMART-CRT trials

BACKGROUND

The utility of atrioventricular (AV) optimization (AVO) algorithms remains in question. A substudy of the SMART-AV trial found that patients with prolonged interventricular delays ≥70 ms were more likely to benefit from cardiac resynchronization therapy (CRT) with AVO. The SMART-CRT trial evaluated AVO on the basis of these results, but the study was underpowered.

OBJECTIVE

To increase statistical power, data from SMART-AV patients meeting the inclusion criterion of interventricular delay ≥70 ms were pooled with data from SMART-CRT to reassess AVO.

METHODS

SMART-CRT and SMART-AV were prospective, randomized, multicenter clinical trials. Patients in both studies were randomized to be programmed with an AVO algorithm (SmartDelay) or fixed AV delay (120 ms). Paired echocardiograms obtained at baseline and 6 months were compared, with CRT response defined as ≥15% reduction in left ventricular end-systolic volume.

RESULTS

A total of 451 complete patient data sets were pooled and analyzed. The baseline demographics between studies did not differ statistically in terms of age, sex, left ventricular ejection fraction, or left ventricular end-systolic volume. The AVO group had a greater proportion of CRT responders (SmartDelay, 73.9%; fixed, 63.1%; P = .014) and greater changes in measures of reverse remodeling. SmartDelay patients with a recommended sensed AV delay outside the nominal range (100-120 ms) had 2.3 greater odds of CRT response than fixed AV delay patients.

CONCLUSION

Greater CRT response and measures of reverse remodeling were observed in patients with SmartDelay enabled vs a fixed AV delay. This study supports the use of SmartDelay in patients with a CRT indication and interventricular delay ≥70 ms.

Clinical outcomes of automatic algorithms in cardiac resynchronization therapy: Systematic review and meta-analysis

Background

Algorithms to automatically adjust atrioventricular (AV) and interventricular (VV) intervals in cardiac resynchronization therapy (CRT) devices are common, but their clinical efficacy is unknown.

Objective

The purpose of this study was to evaluate automatic CRT algorithms in patients with heart failure for the reduction of mortality, heart failure hospitalizations, and clinical improvement.

Methods

We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) in patients with CRT using automatic algorithms that change AV and VV intervals dynamically without manual input, on a beat-to-beat basis. We performed a subgroup analysis including intracardiac electrogram-based (EGM) algorithms and contractility-based algorithms.

Results

Nine RCTs with 8531 participants were included, of whom 4275 (50.1%) were randomized to automatic algorithm. Seven of the 9 trials used EGM-based algorithms, and 2 used contractility sensors. There was no difference in all-cause mortality (10.3% vs 11.3%; odds ratio [OR] 0.90; 95% confidence interval [CI] 0.71-1.03; P = .13; I2 = 0%) or heart failure hospitalizations (15.0% vs 16.1%; OR 0.924; 95% CI 0.81-1.04; P = .194; I2 = 0%) between the automatic algorithm group and the control group. Study-defined clinical improvement was also not significantly different between groups (66.6% vs 63.3%; risk ratio 1.01; 95% CI 0.95-1.06; P = .82; I2 = 50%). In the contractility-based subgroup, there was a trend toward greater clinical improvement with the use of the automatic algorithm (75% vs 68.3%; OR 1.45; 95% CI 0.97-2.18; P = .07; I2 = 40%), which did not reach statistical significance. The overall risk of bias was low.

Conclusion

Automatic algorithms that change AV or VV intervals did not improve mortality, heart failure hospitalizations, or cardiovascular symptoms in patients with heart failure and CRT.

Effects of adaptive left bundle branch-optimized cardiac resynchronization therapy: a single centre experience

BACKGROUND

Adaptive cardiac resynchronization therapy (aCRT) is associated with improved clinical outcomes. Left bundle branch area pacing (LBBAP) has shown encouraging results as an alternative option for aCRT. A technique that can be accomplished effectively using LBBAP combined with coronary venous pacing (LOT-aCRT). We aimed to assess the feasibility and outcomes of LOT-aCRT.

METHODS

LOT-aCRT, capable of providing two pacing modes, LBBAP alone or LBBAP combined with LV pacing, was attempted in patients with CRT indications. Patients were divided into two groups: those with LBBAP and LV pacing (LOT-aCRT) and those with conventional biventricular pacing (BVP-aCRT).

RESULTS

A total of 21 patients were enrolled in the study (10 in the LOT-aCRT group, 11 in the BVP-aCRT group). In the LOT-aCRT group, the QRS duration (QRSd) via BVP was narrowed from 158.0 ± 13.0 ms at baseline to 132.0 ± 4.5 ms (P = 0.019) during the procedure, and further narrowed to 123.0 ± 5.7 ms (P < 0.01) via LBBAP. After the procedure, when LOT-aCRT implanted and worked, QRSd was further changed to 121.0 ± 3.8 ms, but the change was not significant (P > 0.05). In the BVP-aCRT group, BVP resulted in a significant reduction in the QRSd from 176.7 ± 19.7 ms at baseline to 133.3 ± 8.2 ms (P = 0.011). However, compared with LOT-aCRT, BVP has no advantage in reducing QRSd and the difference was statistically significant (P < 0.01). During 9 months of follow-up, patients in both groups showed improvements in the LVEF and NT-proBNP levels (all P < 0.01). However, compared with BVP-aCRT, LOT-aCRT showed more significant changes in these parameters (P < 0.01).

CONCLUSIONS

The study demonstrates that LOT-aCRT is clinically feasible in patients with systolic heart failure and LBBB. LOT-aCRT was associated with significant narrowing of the QRSd and improvement in LV function.

Design of Mid-Q Response: A prospective, randomized trial of adaptive cardiac resynchronization therapy in Asian patients

Aims

The aim of the Mid-Q Response study is to test the hypothesis that adaptive preferential left ventricular-only pacing with the AdaptivCRT algorithm has superior clinical outcomes compared to conventional cardiac resynchronization therapy (CRT) in heart failure (HF) patients with moderately wide QRS duration (≥120 ms and <150 ms), left bundle branch block (LBBB), and normal atrioventricular (AV) conduction (PR interval ≤200 ms).

Methods

This prospective, multi-center, randomized, controlled, clinical study is being conducted at approximately 60 centers in Asia. Following enrollment and baseline assessment, eligible patients are implanted with a CRT system equipped with the AdaptivCRT algorithm and are randomly assigned in a 1:1 ratio to have AdaptivCRT ON (Adaptive Bi-V and LV pacing) or AdaptivCRT OFF (Nonadaptive CRT). A minimum of 220 randomized patients are required for analysis of the primary endpoint, clinical composite score (CCS) at 6 months post-implant. The secondary and ancillary endpoints are all-cause and cardiovascular death, hospitalizations for worsening HF, New York Heart Association (NYHA) class, Kansas City Cardiomyopathy Questionnaire (KCCQ), atrial fibrillation (AF), and cardiovascular adverse events at 6 or 12 months.

Conclusion

The Mid-Q Response study is expected to provide additional evidence on the incremental benefit of the AdaptivCRT algorithm among Asian HF patients with normal AV conduction, moderately wide QRS, and LBBB undergoing CRT implant.

Impact of synchronized left ventricular pacing rate on risk for ventricular tachyarrhythmias after cardiac resynchronization therapy in patients with heart failure

BACKGROUND

The adaptive cardiac resynchronization therapy (aCRT) algorithm automatically produces synchronized left ventricular pacing (sLVP) with intrinsic atrioventricular conduction to improve clinical outcomes. However, relationship between sLVP percentage and risk for ventricular tachyarrhythmia (VT/VF) remains unclear. This study aimed to evaluate the clinical impact of sLVP rate on VT/VF occurrence.

METHODS

In total, 1,419 device interrogation data from 42 consecutive patients who underwent new aCRT device implantation were retrospectively analyzed. The primary endpoint was the first time VT/VF episode after aCRT device implantation.

RESULTS

During a median follow-up of 34 months, 15 patients had VT/VF episodes. Patients were divided into a high sLVP (the average sLVP percentage of ≥ 51.5%, n = 27) or low sLVP group (< 51.5%, n = 15). The high sLVP group had a significantly lower VT/VF incidence (22% vs. 60%; p = 0.014) and an independent predictor for VT/VF occurrence on multivariate analysis (hazard ratio 0.21; p = 0.007). LV ejection fraction improvements after 6 months (12.3 ± 8.7% vs. 2.8 ± 10.3%; p = 0.004) and 12 months (13.8 ± 9.3% vs. 6.2 ± 11.1%; p = 0.030) were significantly greater in the high sLVP group than in the low sLVP group. Age, PR interval, and left atrial diameter were significantly associated with the sLVP rate after aCRT.

CONCLUSIONS

Patients with high sLVP percentage after aCRT had lower long-term risk of VT/VF incidence with a favorable response to CRT. A synchronized pacing algorithm using intrinsic conduction may prevent malignant arrhythmias, as well as recover cardiac functions.

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.

Impact of adaptive cardiac resynchronization therapy in patients with systolic heart failure: Beyond QRS duration and morphology

BACKGROUND

Mechanical and electrical restoration by cardiac resynchronization therapy (CRT) with adaptive pacing algorithm (aCRT) in heart failure patients with a moderately wide (120-149 ms) QRS has not been fully evaluated. The purpose of this study was to investigate the therapeutic effect of aCRT compared with conventional biventricular CRT (BiV-CRT) regardless of QRS morphology.

METHODS

Seventeen consecutive patients with a QRS ≥120 ms, regardless of morphology, underwent CRT device implantation with an aCRT pacing algorithm. Propensity score matched analysis was performed to evaluate the impact of aCRT on the improvement in mechanical and electrical parameters after CRT device implantation using historical controls (HC) from the clinical registry of BiV-CRT (START trial).

RESULTS

Left ventricular (LV) volume significantly decreased after CRT in all patients in both the aCRT and HC groups. The difference in relative reduction of LV end-systolic volume (LVESV) was not significantly different between the 2 arms. QRS shortening after CRT was significantly greater in the aCRT group than in the BiV-CRT group, and the difference was prominent in patients with a moderately wide QRS (120-149 ms). In patients with a moderately wide QRS, the relative reduction in LVESV [39 (29-47)% vs. 2 (-6-20)%, p = 0.04] and proportion of LV volume responders (90% vs. 38%, p = 0.04) were significantly greater in the aCRT group than in the HC group. The proportion of volume responders was not significantly different in patients with a wide QRS (≥150 ms).

CONCLUSIONS

The aCRT algorithm improved electrical and mechanical parameters in patients with a moderately wide QRS, regardless of QRS morphology.

CRT Efficacy in "Mid-Range" QRS Duration Among Asians Contrasted to Non-Asians, and Influence of Height

OBJECTIVES

The purpose of this study was to test the hypotheses that cardiac resynchronization therapy (CRT) efficacy differed among Asians compared with non-Asian populations, differed between QRS duration (QRSd) ranges 120-149 and ≥150 ms, and was influenced by height in the multinational ADVANCE CRT trial.

BACKGROUND

CRT guidelines, derived from trials among U.S./European patients, assign weaker recommendations to those with midrange QRSd (QRSd <150 ms). Patient height may modulate CRT efficacy. Together, these may affect CRT prescription and efficacy in Asia.

METHODS

CRT response was assessed using the Clinical Composite Score 6 months postimplant (n = 934). Heart failure events and cardiac deaths were reported until 12 months. Asian and non-Asian patients were compared overall, by QRSd <150 ms (Asian n = 71 vs non-Asian n = 248), and QRSd ≥150 ms (Asian n = 180 vs non-Asian n = 435) and by height.

RESULTS

Asians comprised 27% (251 of 934) of the primary study population. More Asians had QRSd ≥150 ms (72% [180 of 251] vs 64% [435 of 683] in non-Asian patients; P = 0.022). Overall CRT response was better in Asians vs non-Asians (Clinical Composite Score 85% vs 65%; P <0.001), and following QRSd dichotomization (QRSd <150 ms: 80% vs 59%; P <0.001; QRS ≥150 ms: 86% vs 69%; P < 0.001). HF events and cardiac deaths were fewer in Asians irrespective of QRSd (P < 0.001). Stepwise multivariable analysis indicated that in group QRSd <150 ms, nonischemic cardiomyopathy, number of other comorbidities (0-1 vs ≥4), and atrial fibrillation influenced CRT response. The trend favoring Asian race (OR: 1.46; 95% CI: 0.72-2.95) was eliminated (OR: 1.00; 95% CI: 0.47-2.11) when height or QRSd/height were included (QRSd/height P = 0.006; OR: 1.64; 95% CI: 1.15-2.35). In QRSd <150 ms, probability of CRT response diminished as height increased, but increased with QRSd/height, in both Asians and non-Asians. In QRSd ≥150 ms, height or QRSd/height had minimal effect in Asians or non-Asians.

CONCLUSIONS

Height modulates CRT efficacy among patients with QRSd <150 ms and contributes to high probability of benefit from CRT among Asians. CRT should be encouraged among Asian patients with midrange QRSd. (Advance Cardiac Resynchronization Therapy [CRT] Registry; NCT01805154).

Economic implications of adding a novel algorithm to optimize cardiac resynchronization therapy: rationale and design of economic analysis for the AdaptResponse trial

AIMS

Although cardiac resynchronization therapy (CRT) has proven beneficial in several randomized trials, a subset of patients have limited clinical improvement. The AdaptivCRT algorithm provides automated selection between synchronized left ventricular or biventricular pacing with optimization of atrioventricular delays. The rationale and design of the economic analysis of the AdaptResponse clinical trial are described.

RATIONALE

The costs associated with HF hospitalization are substantial and are compounded by a high rate of readmission. HF hospitalization payments range from $1,001 for Greece to $12,235 for US private insurance. When examining the breakdown of HF-related costs, it is clear that approximately 55% of the hospitalization costs are directly attributable to length of stay. Notably, the mean costs of a CRT patient in need of a HF-related hospitalization are currently estimated to be an average of $10,679.

METHODS

The economic analysis of the AdaptResponse trial has two main objectives. The hospital provider objective seeks to test the hypothesis that AdaptivCRT reduces the incidence of all-cause re-admissions after a heart failure admission within 30 days of the index event. A negative binomial regression model will be used to estimate and compare the number of readmissions after an index HF hospitalization. The payer economic objective will assess cost-effectiveness of CRT devices with the AdaptivCRT algorithm relative to traditional CRT programming. This analysis will be conducted from a U.S. payer perspective. A decision analytic model comprised of a 6-month decision tree and a Markov model for long term extrapolation will be used to evaluate lifetime costs and benefits.

CONCLUSION

AdaptivCRT may offer improvements over traditional device programming in patient outcomes. How the data from AdaptResponse will be used to demonstrate if these clinical benefits translate into substantial economic gains is herein described.

Design and results of aCRT MID-Q study: Adoption of adaptive CRT in patients with normal AV conduction and moderately wide left bundle branch block

BACKGROUND

Sub-analysis of the adaptive CRT (aCRT) trial demonstrated the potential benefits of the aCRT algorithm over conventional echo-guided bi-ventricular (BiV) pacing in patients with left bundle branch block (LBBB) with moderately wide QRS (120-149 ms) and normal atrioventricular (AV) conduction.

METHODS

Adoption of Adaptive CRT in Patients with Left Bundle Branch Block and Moderately Wide QRS (aCRT MID-Q, UMIN Clinical Trials Registry Number: 000022452) was a multicenter, prospective, randomized, double-blind study designed to investigate the superiority of the aCRT pacing algorithm compared to echo-guided BiV pacing in patients with moderately wide LBBB and normal AV conduction. The primary endpoint was the improvement in clinical composite score (CCS) at 6 months; the secondary endpoints were changes in left ventricular (LV) end-systolic volume, LV ejection fraction, New York Heart Association classification, 6-min walk distance, and quality of life from baseline to 6 months post-randomization; heart failure administration; all-cause mortality; and cardiac mortality within 12 months.

RESULTS

The trial was terminated prematurely after enrollment of 39 patients (aCRT arm; n = 17, echo-guided BiV arm; n = 22) because of lower than expected enrollment. In the intention-to-treat analysis, the improvement of CCS was achieved in 10 patients (59%) in the aCRT arm (n = 17) and 16 patients (73%) in the echo-guided BiV arm (n = 22, p = 0.36). For the secondary endpoint, only 6-min walk distance was significantly greater in the aCRT arm than in the echo-guided BiV arm, and no difference was observed in the echocardiographic parameters. Heart failure hospitalization-free survival was also not significantly different (p = 0.91). There was no death during the follow-up.

CONCLUSIONS

Improvement of CCS was similarly observed after aCRT and echo-guided BiV in CRT recipients with moderately wide LBBB and normal AV conduction. A prospective study is needed to explore the impact of CRT and pacing algorithm on Japanese patients with moderately wide LBBB.

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.

Technology Advances to Improve Response to Cardiac Resynchronization Therapy: What Clinicians Should Know

Cardiac resynchronization therapy (CRT) is a well-established treatment for symptomatic heart failure patients with reduced left ventricular ejection fraction, prolonged QRS duration, and abnormal QRS morphology. The ultimate goals of modern CRT are to improve the proportion of patients responding to CRT and to maximize the response to CRT in patients who do respond. While the rate of CRT nonresponders has moderately but progressively decreased over the last 20 years, mostly in patients with left bundle branch block, in patients without left bundle branch block the response rate is almost unchanged. A number of technological advances have already contributed to achieve some of the objectives of modern CRT. They include novel lead design (the left ventricular quadripolar lead, and multipoint pacing), or the possibility to go beyond conventional delivery of CRT (left ventricular endocardial pacing, His bundle pacing). Furthermore, to improve CRT response, a triad of actions is paramount: reducing the burden of atrial fibrillation, reducing the number of appropriate and inappropriate interventions, and adequately predicting heart failure episodes. As in other fields of cardiology, technology and innovations for CRT delivery have been at the forefront in transforming-improving-patient care; therefore, these innovations are discussed in this review.

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.