Value of right ventricular-left ventricular interlead electrical delay to predict reverse remodelling in cardiac resynchronization therapy: the INTER-V pilot study

Role of Electrical Delay in Cardiac Resynchronization Therapy Response

Traditionally, left ventricular (LV) lead position was guided by anatomic criteria of pacing from the lateral wall of the LV. However, large trials showed little effect of LV lead position on outcomes, other than noting worse outcomes with apical positions. Given the poor correlation of cardiac resynchronization therapy (CRT) outcomes with anatomically guided LV lead placement, focus shifted toward more physiologic predictors such as targeting the areas of delayed mechanical and electrical activation. Measures of left ventricular delay and interventricular delay are strong predictors of CRT response.

Changes in cardiac conduction time following cardiac resynchronization therapy: rationale and design of the RECOVER study

BACKGROUND

It has been known that ventricular conduction delays play a key role in the cardiac resynchronization therapy (CRT) response of patients with advanced heart failure (HF). However, no study to our knowledge has yet evaluated the serial changes in conduction times measured between different electrodes of CRT devices.

METHODS AND RESULTS

The Reduction or Extension of Conduction Time with Ventricular Electromechanical Remodeling (RECOVER) study (NCT04397224) was designed to investigate serial changes in interelectrode conduction times and to elucidate their prognostic value. We plan to enroll 100 patients implanted with CRT systems with endocardial quadripolar left ventricular leads. Patients will be scheduled for follow-up every 3 months over a period of 2 years, where they will undergo measurement of interelectrode conduction times to evaluate their serial changes. The primary outcome of the RECOVER study is the correlation between the degree of conduction time changes and the CRT response as defined by echocardiography. The time course and prognostic value of the serial changes in conduction times will be investigated as well.

CONCLUSION

The RECOVER study is investigating whether serial changes in interelectrode conduction times can be useful parameters in predicting the CRT response or detecting worsening HF at an early stage.

Interrelationships between interventricular electrical delays in cardiac resynchronization therapy

INTRODUCTION

In cardiac resynchronization therapy, pacing the left ventricle (LV) at sites of prolonged electrical delay is associated with better outcomes. We sought to characterize the interrelationships between intrinsic, right-ventricular (RV)-paced, and LV-paced interventricular delays.

METHODS AND RESULTS

The following electrical timings were measured at implantation for all electrodes of the LV quadripolar leads: QLV, interventricular delay in intrinsic rhythm (RVs-LVs), in RV-paced rhythm (RVp-LVs), and in LV-paced rhythm (LVp-RVs). We included 32 patients (78% men, age 72 years, LV ejection fraction 29%, left bundle branch block 84%). QLV and RVs-LVs were correlated (R²  = .72, p < .0001), as were RVs-LVs and RVp-LVs (R²  = .27, p = .002) and RVp-LVs and LVp-RVs (R²  = .60, p < .001). Direction of activation along the four LV lead electrodes was concordant between RVs-LVs and RVp-LVs in only 17 (53%) patients. The latest-activated electrodes in RVs-LVs and RVp-LVs were concordant in 26 (81%) patients, adjacent in 3 (9%) patients, and remote in 3 (9%) patients. Biventricular-paced QRS duration varied by more than 10 ms between the two electrodes in half of the patients with dissimilar latest electrodes. Among the seven echocardiographic nonresponders at 6 months, the programmed electrode was remote from the latest electrode in RVs-LVs in five patients and in RVp-LVs in three patients.

CONCLUSION

Intrinsic and RV-paced interventricular electrical delays are correlated, but there is substantial heterogeneity between patients. The latest-activated electrode may be different between RVs-LVs and RVp-LVs, and this might have important implications in selecting the optimal LV vector.

Left ventricular paced activation in cardiac resynchronization therapy patients with left bundle branch block and relationship to its electrical substrate

Background

Cardiac resynchronization therapy (CRT) uses left ventricular (LV) pacing to restore rapid synchronized LV activation when it is delayed in patients with myocardial disease.

Objective

Although intrinsic LV activation delays are understood, little is known about reactions to LV stimulation and whether they are affected by QRS duration (QRSd), morphology, LV substrate, or choice of electrode pair. The purpose of this study was to test these interactions.

Methods

In 120 heart failure patients with left bundle branch block (LBBB) and QRS >120 ms receiving CRT with quadripolar LV leads, device-based measurements of intrinsic activation delay (qLV) and paced inter- (and intra-) LV conduction times were evaluated at the proximal and distal LV bipoles.

Results

During intrinsic conduction, qLV varied little between the proximal and distal pairs in patients with LBBB (n = 120; age 68 ± 11 years; 63% male; ejection fraction 25% ± 7%; 33% ischemic cardiomyopathy; QRSd 162 ± 19 ms). A minority (30%) had conduction barriers (ie, gradients) (ΔqLV 29 ± 8 ms vs 9 ± 5 ms in patients without gradients; P <.01), which occurred equally in ischemic and nonischemic patients. A majority were functional (and not scar-mediated), as they resolved with pacing in most patients (75%). Importantly, LV-paced conduction times were unrelated to baseline QRS morphology (LBBB 166 ± 30 ms vs RBBB control 172 ± 30 ms; P = NS), longer than intrinsic conduction (166 ± 30 ms vs 129 ± 28 ms; P <.01), and varied significantly by electrode pair (ie, small distances) and etiology. Correlation between intrinsic activation delay (qLV) and LV-paced conduction time was poor (R² = 0.278; P <.05).

Conclusion

LV-paced effect, which is core to CRT, is unpredictable based on conventionally used measures and should be considered during CRT optimization.

Differences in right-to-left vs left-to-right interventricular conduction times in patients indicated to cardiac resynchronization therapy

INTRODUCTION

Differences in conduction times from right ventricle to left ventricle and from left ventricle to right ventricle respectively were observed during biventricular devices implantation when changing pacing vector direction. In this article the phenomenon of interventricular conduction time differences is described and assessed in relationship to various clinical and electrophysiological parameters.

METHODS

In 62 consecutive patients (9 females) interventricular conduction times between right and left ventricle in both directions were measured during cardiac resynchronization therapy device implantation procedure. Complex pacing protocol was performed.

RESULTS

Investigated individuals was divided into 3 subgroups according to type of interventricular conduction pattern and statistically tested with various clinical data. Substantial differences in right-to-left vs left-to-right conduction times (> 5 ms, range 7-72 ms) were observed in 24 (39%) of all patients. They were more common in patients with dilated cardiomyopathy (20 of 38, 53%) compared to 4 (17%) of 24 patients with coronary artery disease (p = 0.011). The phenomenon occurred more often in hypertensive patients (p = 0.012). Other tested factors were nonsignificant.

CONCLUSIONS

There are almost no data on this topic. The occurrence of conduction difference phenomenon is quite common in dilated cardiomyopathy while it is rare in coronary artery disease. We assume the diffuse nature of the disease and the way of remodeling of myocardium play the main role. Knowledge of this phenomenon could be useful in personalized cardiac resynchronization therapy optimization.

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.

Three-dimensional interlead distance predicts response and outcomes after cardiac resynchronization therapy

BACKGROUND

Approximately one-third of patients do not respond favourably to cardiac resynchronization therapy (CRT). A longer distance between ventricular leads may improve response.

AIM

To study the impact of the true three-dimensional interlead distance (ILD) on outcomes.

METHODS

Consecutive patients undergoing CRT device implantation were included prospectively. Interlead separation was measured from postprocedural anterior-posterior and lateral chest X-rays. The three-dimensional ILD was calculated using the Pythagorean theorem. Response to CRT was defined using a composite clinical score at 6 months.

RESULTS

Forty-two patients were included (mean age 70±9 years; QRS duration 154±31ms; left ventricular ejection fraction 26±7%; 50% ischaemic). At 6 months, 71% of patients were considered to be responders. Responders had a significantly longer ILD (108±17 vs. 87±21mm; P=0.002). When the ILD was corrected for cardiac size, the optimal cut-off value was ≥ 0.53 for predicting response (sensitivity 83%, specificity 75%, area under the curve 0.84; P=0.0002). Similar results were obtained in a historical retrospective cohort. The use of proximal electrodes on the left ventricular lead was associated with a longer ILD in 95% of patients, compared with more distal pacing configurations. In the total cohort of 74 patients (median follow-up, 420 days), those with an indexed ILD ≥ 0.53 had a 70% reduction in risk of hospitalization for heart failure (P=0.004).

CONCLUSION

Longer three-dimensional ILD corrected for cardiac size measured on chest radiographs can accurately predict response to CRT and outcomes. This simple variable may be used to identify optimal lead placement and pacing configuration during CRT implantation.

Interventricular Electrical Delay Is Predictive of Response to Cardiac Resynchronization Therapy

OBJECTIVES

This study was conceived to evaluate the relationship between interventricular electrical delay, as measured by the right ventricle-left ventricle (RV-LV) interval, and outcomes in a prospectively designed substudy of the SMART-AV (SMARTDELAY determined AV Optimization) trial.

BACKGROUND

Despite the well-documented benefit of cardiac resynchronization therapy (CRT), the nonresponder rate remains an important clinical problem. Implanting LV leads by traditional anatomic criteria has limited impact on outcomes. However, pacing at sites with late electrical activation improves CRT response rates. Thus, we hypothesized that interventricular electrical delay is associated with improved CRT outcomes.

METHODS

This was a multicenter study of patients with advanced heart failure undergoing CRT implantation. In 419 subjects, the unpaced RV-LV interval was measured in sinus rhythm. LV volumes and ejection fraction were measured by echocardiography at baseline and after 6 months of CRT by a blinded core laboratory. Quality of life (QOL) was assessed by a standardized questionnaire.

RESULTS

When separated by quartiles based on interventricular delay, the magnitudes of LV volumes, ejection fraction and the QOL measure increased significantly with prolongation of RV-LV delay (p < 0.05). The LV end-systolic volume response rate increased progressively from 30% to 75% (p < 0.001), and the QOL response rate increased from 50% to 65% (p = 0.08). Patients in the highest quartile of RV-LV had a 5.98-fold increase (p < 0.001) in their odds of a reverse remodeling response, with female sex, ischemic etiology, and baseline LV end-systolic volume being the other independent predictors of response.

CONCLUSIONS

Baseline interventricular delay is a potent independent predictor of remodeling and QOL responses with CRT.

Apical vs. non-apical right ventricular pacing in cardiac resynchronization therapy: a meta-analysis

AIMS

Cardiac resynchronization therapy (CRT) has been shown to improve outcomes in patients with heart failure. The optimal site of right ventricular (RV) stimulation in CRT has not been established. We aimed to conduct a meta-analysis of randomized-controlled trials and observational studies comparing the mid- and long-term effects of RV apical (RVA) and non-apical (RVNA) pacing on CRT outcomes.

METHODS

We systematically searched the Cochrane library, EMBASE, and MEDLINE databases for studies evaluating RVA vs. RVNA pacing in CRT with regards to left ventricular end-systolic volume (LVESV) reduction, functional status improvement (defined as ≥1 New York Heart Association class improvement), and the clinical outcome of mortality or cardiovascular hospitalization. Effect estimates [standardized mean difference (SMD) and odds ratio (OR) with 95% confidence intervals (CI)] were pooled using random-effect models.

RESULTS

Twelve studies comprising 2670 patients (1655 with an apical and 1015 with a non-apical RV lead position) were included. In meta-analyses, LVESV reduction and functional status improvement were similar in patients with RVA and RVNA pacing (SMD 0.13, 95% CI: -0.24 to 0.50, P = 0.48; OR 1.08, 95% CI: 0.81 to 1.45, P = 0.60, respectively). Data regarding mortality and hospitalizations could not be pooled due to a small number of relevant studies with significant heterogeneity.

CONCLUSION

Our meta-analysis suggests that in CRT patients the effects of RVA or RVNA pacing on LV remodelling and functional status are similar. Mortality and morbidity outcomes with different RV lead positions should be further assessed in randomized clinical trials.

Sex differences in device therapy for heart failure: utilization, outcomes, and adverse events

BACKGROUND

Multiple studies of heart failure patients demonstrated significant improvement in exercise capacity, quality of life, cardiac left ventricular function, and survival from cardiac resynchronization therapy (CRT), but the underenrollment of women in these studies is notable. Etiological and pathophysiological differences may result in different outcomes in response to this treatment by sex. The observed disproportionate representation of women suggests that many women with heart failure either do not meet current clinical criteria to receive CRT in trials or are not properly recruited and maintained in these studies.

METHODS

We performed a systematic literature review through May 2014 of clinical trials and registries of CRT use that stratified outcomes by sex or reported percent women included. One-hundred eighty-three studies contained sex-specific information.

RESULTS

Ninety percent of the studies evaluated included ≤ 35% women. Fifty-six articles included effectiveness data that reported response with regard to specific outcome parameters. When compared with men, women exhibited more dramatic improvement in specific parameters. In the studies reporting hazard ratios for hospitalization or death, women generally had greater benefit from CRT.

CONCLUSIONS

Our review confirms women are markedly underrepresented in CRT trials, and when a CRT device is implanted, women have a therapeutic response that is equivalent to or better than in men, while there is no difference in adverse events reported by sex.

Long-term clinical response to cardiac resynchronisation therapy under a multidisciplinary model

BACKGROUND

Cardiac resynchronisation therapy (CRT) is established in the management of cardiac failure in patients with systolic dysfunction. Clinical response to CRT is not uniform, and response has been difficult to predict.

AIM

Patient management within a high volume, multidisciplinary service focused on optimal delivery of CRT would improve response rates.

METHODS

Four hundred and thirty-five consecutive patients who underwent CRT under a multidisciplinary heart failure service were enrolled prospectively over a 5-year period. Medically optimised, symptomatic patients with an ejection fraction (EF) <35%, widened QRS or abnormal dyssynchrony index were included. Left ventricular lead position was targeted anatomically to the segment of latest mechanical activation, and electrically to a site with maximal intrinsic intracardiac electrogram separation. Routine device and clinical follow up, as well as CRT optimisations, were performed at baseline and at 3-monthly intervals. Responders were defined as having an absolute reduction in left ventricular end-diastolic diameter >10% and an improvement in EF >5%.

RESULTS

With a mean follow up of 53 ± 11 months, response rate to CRT was 81%. Mean EF improved from 26 ± 10% to 37 ± 11%, and mean left ventricular end-diastolic diameter reduced from 68.6 ± 9.2 mm to 57.8 ± 9.3 mm. Predictors of response were sinus rhythm, high dyssynchrony index and intrinsic electrical dyssynchrony >80 ms. Successful LV lead implantation at initial procedure was achieved in 99.1%, and at latest follow up 94.6% of initial LV leads were still active.

CONCLUSION

CRT undertaken with a unit focus on optimal LV lead positioning and device optimisation, along with a multidisciplinary follow-up model, results in an excellent response rate to CRT.

Improved relationship between left and right ventricular electrical activation after cardiac resynchronization therapy in heart failure patients can be quantified by body surface potential mapping

OBJECTIVES

Few studies have evaluated cardiac electrical activation dynamics after cardiac resynchronization therapy. Although this procedure reduces morbidity and mortality in heart failure patients, many approaches attempting to identify the responders have shown that 30% of patients do not attain clinical or functional improvement. This study sought to quantify and characterize the effect of resynchronization therapy on the ventricular electrical activation of patients using body surface potential mapping, a noninvasive tool.

METHODS

This retrospective study included 91 resynchronization patients with a mean age of 61 years, left ventricle ejection fraction of 28%, mean QRS duration of 182 ms, and functional class III/IV (78%/22%); the patients underwent 87-lead body surface mapping with the resynchronization device on and off. Thirty-six patients were excluded. Body surface isochronal maps produced 87 maximal/mean global ventricular activation times with three regions identified. The regional activation times for right and left ventricles and their inter-regional right-to-left ventricle gradients were calculated from these results and analyzed. The Mann-Whitney U-test and Kruskall-Wallis test were used for comparisons, with the level of significance set at p≤0.05.

RESULTS

During intrinsic rhythms, regional ventricular activation times were significantly different (54.5 ms vs. 95.9 ms in the right and left ventricle regions, respectively). Regarding cardiac resynchronization, the maximal global value was significantly reduced (138 ms to 131 ms), and a downward variation of 19.4% in regional-left and an upward variation of 44.8% in regional-right ventricular activation times resulted in a significantly reduced inter-regional gradient (43.8 ms to 17 ms).

CONCLUSIONS

Body surface potential mapping in resynchronization patients yielded electrical ventricular activation times for two cardiac regions with significantly decreased global and regional-left values but significantly increased regional-right values, thus showing an attenuated inter-regional gradient after the cardiac resynchronization therapy.

Clinical implication of right ventricular to left ventricular interlead sensed electrical delay in cardiac resynchronization therapy

AIMS

To evaluate the clinical implication of right ventricular (RV) to left ventricular (LV) interlead sensed electrical delay (RV-LVs) and the relation to ventricular lead position in cardiac resynchronization therapy (CRT).

METHODS AND RESULTS

Eighty-five consecutive CRT patients (mean age 66 ± 11 years) received LV lead prospectively targeted to the latest mechanical activated segment (concordant), assessed by two-dimensional speckle tracking radial strain (ST-RS) echocardiography. The RV lead was randomized to RV apex (n= 43) or RV high posterior septum (n= 42). Right ventricular to left ventricular interlead sensed electrical delay was obtained during the CRT implant procedure. Intraventricular dyssynchrony was evaluated by ST-RS echocardiography. Interventricular mechanical delay (IVMD) was measured by using pulse-wave Doppler. Separated by the median RV-LVs (82 ms), a long RV-LVs demonstrated more LV end-systolic volume (LVESV) reduction than a short RV-LVs (-27 ± 20 vs. -16 ± 22%; P= 0.02), 6 months after CRT (6FU). Right ventricular to left ventricular interlead sensed electrical delay correlated to IVMD (r = 0.50; P< 0.001) and intraventricular dyssynchrony (r = 0.25; P= 0.02) at baseline. Concordant LV leads (n= 61) demonstrated superior reduction of LVESV (P= 0.005) 6 months after CRT; however, both RV lead positions had similar effects. Right ventricular to left ventricular interlead sensed electrical delay was irrespective to LV lead concordance and RV lead position (P= ns). Independent predictors to reverse remodelling (reduction of LVESV ≥ 15%) at 6FU were concordant LV lead (odds ratio, 3.210; P= 0.029) and IVMD (odds ratio, 1.028; P= 0.026).

CONCLUSION

Right ventricular to left ventricular interlead sensed electrical delay was not predictive to LV reverse remodelling affected by CRT at 6FU. Concordant LV leads demonstrated superior LV reverse remodelling at 6FU. Right ventricular to left ventricular interlead sensed electrical delay was irrespective of ventricular lead position and might be insufficient to target optimal LV lead position in CRT.

TRIAL REGISTRATION

http://clinicaltrials.gov. Unique identifier: NCT01035489.

Electrical activation in the coronary sinus branches as a guide to cardiac resynchronisation therapy: rationale for a coordinate system

BACKGROUND

For successful cardiac resynchronisation therapy (CRT) a spatial and electrical separation of right and left ventricular electrodes is essential. The spatial distribution of electrical delays within the coronary sinus (CS) tributaries has not yet been identified.

OBJECTIVE

Electrical delays within the CS are described during sinus rhythm (SR) and right ventricular pacing (RVP). A coordinate system grading the mitral ring from 0° to 360° and three vertical segments is proposed to define the lead positions irrespective of individual CS branch orientation.

METHODS

In 13 patients undergoing implantation of a CRT device 6±2.5, (median 5) lead positions within the CS were mapped during SR and RVP. The delay to the onset and the peak of the local signal was measured from the earliest QRS activation or the pacing spike. Fluoroscopic positions were compared to localizations on a nonfluoroscopic electrode imaging system.

RESULTS

During SR, electrical delays in the CS were inhomogenous in patients with or without left bundle branch block (LBBB). During RVP, the delays increased by 44±32 ms (signal onset from 36±33 ms to 95±30 ms; p<0.001, signal peak from 105±44 ms to 156±30 ms; p<0.001). The activation pattern during RVP was homogeneous and predictable by taking the grading on the CS ring into account: (% QRS) = 78-0.002 (grade-162)(2), p<0.0001. This indicates that 78% of the QRS duration can be expected as a maximum peak delay at 162° on the CS ring.

CONCLUSION

Electrical delays within the CS vary during SR, but prolong and become predictable during RVP. A coordinate system helps predicting the local delays and facilitates interindividual comparison of lead positions irrespective of CS branch anatomy.

Lead positioning strategies to enhance response to cardiac resynchronization therapy

Left ventricular lead position is one of the main determinants of CRT response. There are several approaches in LV lead positioning that include favoring an optimal anatomical position or targeting either the segment with maximal mechanical dyssynchrony or a region with maximal electrical delay. The conventional LV lead implantation faces several technical difficulties that may prevent the obtaining of a stable position and good performance of the LV lead without phrenic nerve stimulation. In addition, implant of the LV pacing lead in areas with myocardial scar may result in less than optimal cardiac resynchronization. Several strategies have been proposed to overcome all these obstacles including multimodality cardiac imaging to help in preprocedural or intraprocedural identification of the latest activated areas of the LV and the potential anatomical constraints. In selected patients, the surgical implant may be a solution to overcome these constraints. In the future, LV endocardial or epicardial multisite pacing may deliver an enhanced response to CRT.