Right ventricular lead location and outcomes among patients with cardiac resynchronization therapy: A meta-analysis

BACKGROUND

Cardiac resynchronization therapy (CRT) has been demonstrated to improve heart failure (HF) symptoms, reverse LV remodeling, and reduce mortality and HF hospitalization (HFH) in patients with a reduced left ventricular (LV) ejection fraction (LVEF). Prior studies examining outcomes based on right ventricular (RV) lead position among CRT patients have provided mixed results. We performed a systematic review and meta-analysis of randomized controlled trials and prospective observational studies comparing RV apical (RVA) and non-apical (RVNA) lead position in CRT.

METHODS

Our meta-analysis was constructed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for systematic reviews and meta-analyses. We searched EMBASE and MEDLINE. Eligible studies reported on at least one of the following outcomes of interest: all-cause mortality, the composite endpoint of death and first HFH hospitalization, change in LVEF, New York Heart Association (NYHA) class improvement, and change in LV end systolic volume (LVESV). We performed meta-analysis summaries using a DerSimonian-Laird random-effects model and conservatively used the Knapp-Hartung approach to adjust the standard errors of the estimated model coefficients.

RESULTS

We included nine studies representing a total of 1832 patients. Of those, 1318 (72%) patients had RVA lead placement and 514 (28%) had RVNA lead placement. The mean age of patients was 65.5 ± 4.4 years, and they were predominantly men (69%-97%). There was no statistically significant difference in all-cause mortality by RVA vs. RVNA (OR = 0.77, 95% CI 0.32-1.89; I2 = 16.7%, p = 0.31), or in the combined endpoint of all-cause mortality and first HFH (OR 0.88, 95% CI 0.62-1.25; I2 = 0%, p = 0.84). Also, there was no difference between RVA and RVNA for NYHA class improvement (OR = 1.03, 95% CI 0.9-1.17; I2 = 0%, p = 0.99), change in LVEF (mean difference (MD) = 1.33, 95% CI -1.45 to 4.10; I2 = 47%; p = 0.093), and change in LVESV (MD = -1.11, 95% CI -3.34 to 1.12; I2 = 0%; p = 0.92).

CONCLUSION

This meta-analysis shows that in CRT pacing, RV lead position does not appear to be associated with clinical outcomes or LV reverse remodeling. Further studies should focus on the relationship of RV lead vis-à-vis LV lead location, and its clinical importance.

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.

Incidence, definition, diagnosis, and management of the cardiac resynchronization therapy nonresponder

PURPOSE OF REVIEW

Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with mild-to-severe heart failure. However, up to 40% of CRT recipients are nonresponders. This review addresses important aspects with regard to the identification and management of CRT nonresponders.

RECENT FINDINGS

Mid-term clinical or echocardiographic nonresponse is associated with worse clinical outcomes during the extended follow-up. A number of predictors are indicative of CRT response, which include patient characteristics, electrical determinants, and imaging techniques from preimplant to postimplant period, and can be grouped as modifiable and nonmodifiable contributors to treatment response. Advanced age, male sex, ischemic cause, end-stage heart failure, inadequate electrical delay, and absence of mechanical dyssynchrony are regarded as unfavorable but nonmodifiable factors, for which considering underutilization of CRT by refining patient selection is reasonable. On the contrary, more efforts should be made to optimize patient management by correcting those modifiable factors, such as suboptimal medical therapy, uncontrolled atrial fibrillation, left ventricular lead dislodgement or inappropriate location, loss of biventricular capture, and lack of device optimization.

SUMMARY

Proper management and careful selection of CRT recipients will transform a proportion of treatment nonresponders into responders, which is vital to improve patients' outcome.

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.

Optimizing benefit from CRT: role of speckle tracking echocardiography, the importance of LV lead position and scar

Cardiac resynchronization therapy is demonstrated to be effective in patients with advanced heart failure. Correcting mechanical dyssynchrony is proposed as the predominant mechanism of response. Achieving optimum left ventricular lead position, at the site of maximal mechanical dyssynchrony but away from transmural scar, is identified as one of the main determinants of both symptomatic and prognostic benefit. Strategies employing multimodality cardiac imaging techniques have been used to identify this optimal pacing site, in addition to any potential anatomical limitations to successful implantation. Speckle tracking echocardiography offers prospective lead targeting, incorporating pathophysiological determinants of cardiac resynchronization therapy response. This review considers the key factors in defining optimum left ventricular lead location, emphasizing the role of myocardial scar. The use of speckle tracking echocardiography and the potential for this technique to be incorporated into routine practice to guide the implant strategy in an individual patient is discussed.

Focus on right ventricular outflow tract septal pacing

Experimental and clinical studies have shown that right ventricular apical pacing may result in long-term deleterious effects on account of its negative impact on left ventricular remodeling through desynchronization. This risk appears more pronounced in patients with even moderate left ventricular dysfunction and generally occurs after at least 1 year of pacing. As right ventricular apical pacing may be associated with the development of organic mitral insufficiency, other sites that allow for more physiological stimulation, such as right ventricular outflow tract septal pacing, have been developed, with good feasibility and reproducibility. However, the prospective randomized studies and meta-analyses to date have only demonstrated a modest effect on ejection fraction in the medium term, without any significant effect on quality of life and morbimortality. However, the absence of a favorable effect for right ventricular outflow tract septal pacing compared with right ventricular apical pacing in terms of clinical manifestations and patient prognosis appears to be more associated with the designs of these studies, which were not homogeneous with regard to methodology used, judgment criteria, follow-up and, especially, statistical power. Two randomized prospective multicentre studies are currently ongoing in order to evaluate the favorable effect of infundibular septal pacing, when considering the indirect negative effects of right ventricular apical pacing as reported in the literature.

Optimizing cardiac resynchronization therapy for congestive heart failure

In patients with advanced systolic heart failure and mechanical dyssynchrony, cardiac resynchronization therapy (CRT) is an effective means of improving symptoms and reducing mortality. There are now several recognized approaches to optimize CRT. Imaging modalities can assist with identifying the myocardium with the latest mechanical activation for targeted left ventricular lead implantation. Device programming can be tailored to maximize biventricular pacing, and thereby is its benefit. Cardiac imaging has shown that atrioventricular and interventricular intervals can be adjusted to further reduce dyssynchrony. We review these various approaches that maximize the benefit derived from CRT.

Canadian Cardiovascular Society guidelines on the use of cardiac resynchronization therapy: evidence and patient selection

Recent landmark trials provided the impetus to update the recommendations for cardiac resynchronization therapy (CRT). This article provides guidance on the prescription of CRT within the confines of published data. A future article will explore the implementation of these guidelines. These guidelines are intended to serve as a framework for the prescription of CRT within the Canadian health care system and beyond. They were developed through a critical evaluation of the existing literature, and expert consensus. The panel unanimously adopted each recommendation. The 8 recommendations relate to ensuring the adequacy of medical therapy before the initiation of CRT, the use of symptom severity to select candidates for CRT, differing recommendations based on the presence or absence of sinus rhythm, the presence of left bundle branch block vs other conduction patterns, and QRS duration. The use of CRT in the setting of chronic right ventricular pacing, left ventricular lead placement, and the routine assessment of dyssynchrony to guide the prescription of CRT are also included. The strength of evidence was weighed, taking full consideration of any risks of bias, as well as any imprecision, inconsistency, and indirectness of the available data. The strength of each recommendation and the quality of evidence were adjudicated. Trade-offs between desirable and undesirable consequences of alternative management strategies were considered, as were values, preferences, and resource availability. These guidelines were externally reviewed by experts, modified based on those reviews, and will be updated as new knowledge is acquired.

Right ventricular pacing and sensing function in high posterior septal and apical lead placement in cardiac resynchronization therapy

BACKGROUND

The conventional right ventricular (RV) lead position in cardiac resynchronization therapy pacemakers (CRT-P) is the RV apex (RV-A). Little is known about electrophysiological stability and associated complications of pacing leads in RV high posterior septal (RV-HS) position in CRT-P.

METHODS

Two hundred and thirty-five consecutive CRT-P patients were included from 1999-2010. Pacing thresholds at 0.5ms and 2.5V, sensing electrograms and lead impedances were measured at implant and repeated 1,3,6,12,18 and 24 months after CRT-P. Electrophysiological measurements of leads located in RV-A and RV-HS were analyzed retrospectively. Bipolar RV leads were used, including high impedance leads, passive fixation and active fixation.

RESULTS

RV pacing leads were implanted in RV-A (n=79) and RV-HS (n=156). Average RV pacing thresholds from CRT implant procedure to 24-month follow-up at 0.5ms were 0.77±0.69V in RV-A and 0.71±0.35V in RV-HS (P=0.31), and at 2.5V were 0.06±0.08ms in RV-A and 0.07±0.05ms in RV-HS (P=0.12). Average RV electrogram amplitudes from baseline to 24 months after CRT were 15.3±6.9mV in RV-A and 12.1±6.0mV in RV-HS (P=0.55). Average RV impedances during follow-up were 850±286Ω in RV-A and 618±147Ω in RV-HS (P=0.57). Similar RV lead revisions between RV-A and RV-HS were observed after 2-year follow-up (P=0.55).

CONCLUSION

The RV-HS lead position demonstrated stable and acceptable long-term pacing and sensing function, with rates of complications comparable to conventional RV-A lead position in CRT. The RV-HS lead position is feasible in CRT-P.

Adverse response to cardiac resynchronisation therapy in patients with septal scar on cardiac MRI preventing a septal right ventricular lead position

PURPOSE

Myocardial scar is an adverse factor when considering which patients are likely to respond to cardiac resynchronisation therapy (CRT). We hypothesized that septal scarring on magnetic resonance imaging (MRI) may be associated with a poor outcome from CRT, which may relate to the inability to place the right ventricular (RV) lead in the septum.

METHODS

Fifty patients (ejection fractions, 25 ± 8%; 45 men, 62.8 ± 14 years; 26 dilated cardiomyopathy; and 24 ischaemic cardiomyopathy (ICM)) receiving CRT underwent delayed enhancement cardiac MRI to assess location and burden of myocardial scar. Acute hemodynamic response (AHR) was evaluated at implant with a pressure wire in the left ventricular (LV) cavity. LV remodelling was determined by reduction in LV end-systolic volume at 6 months.

RESULTS

The presence of ICM with septal scar was associated with a poor acute and chronic response to CRT. This was predominantly due to a worse response in patients with septal scar. Patients without septal scar had a better AHR with a 26.7 ± 28.9% rise in LV dP/dt (max) from baseline vs. -2.8 ± 14.5% for patients with septal scar (P = 0.01) with Biventricular (BIV) pacing. A greater proportion remodelled (56% vs. 20% (P = 0.02)). Furthermore, only 33% of patients with septal scar had an RV septal lead compared with 66% with no septal scar (P = 0.03).

CONCLUSIONS

The presence of septal scar was associated with a poor acute and chronic response to CRT. This may relate to the inability to achieve a RV septal lead placement.

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.

Biophysical modeling to simulate the response to multisite left ventricular stimulation using a quadripolar pacing lead

BACKGROUND

Response to cardiac resynchronization therapy (CRT) is reduced in patients with posterolateral scar. Multipolar pacing leads offer the ability to select desirable pacing sites and/or stimulate from multiple pacing sites concurrently using a single lead position. Despite this potential, the clinical evaluation and identification of metrics for optimization of multisite CRT (MCRT) has not been performed.

METHODS

The efficacy of MCRT via a quadripolar lead with two left ventricular (LV) pacing sites in conjunction with right ventricular pacing was compared with single-site LV pacing using a coupled electromechanical biophysical model of the human heart with no, mild, or severe scar in the LV posterolateral wall.

RESULT

The maximum dP/dt(max) improvement from baseline was 21%, 23%, and 21% for standard CRT versus 22%, 24%, and 25% for MCRT for no, mild, and severe scar, respectively. In the presence of severe scar, there was an incremental benefit of multisite versus standard CRT (25% vs 21%, 19% relative improvement in response). Minimizing total activation time (analogous to QRS duration) or minimizing the activation time of short-axis slices of the heart did not correlate with CRT response. The peak electrical activation wave area in the LV corresponded with CRT response with an R(2) value between 0.42 and 0.75.

CONCLUSION

Biophysical modeling predicts that in the presence of posterolateral scar MCRT offers an improved response over conventional CRT. Maximizing the activation wave area in the LV had the most consistent correlation with CRT response, independent of pacing protocol, scar size, or lead location.

Sites of left and right ventricular lead implantation and response to cardiac resynchronization therapy observations from the REVERSE trial

OBJECTIVES

The objective of this study is to ascertain the effects of the left (LV) and right (RV) ventricular lead tip position in response to cardiac resynchronization therapy (CRT).

BACKGROUND

The REVERSE randomized trial examined the effects of CRT in patients with asymptomatic or mildly symptomatic heart failure (HF).

METHODS

We analysed data collected from the active group (CRT-ON) of REVERSE in whom the precise locations of the LV and RV ventricular lead tips were determined from postoperative chest roentgenograms as part of a prespecified sub-study. LV position was classified as lateral or non-lateral, and apical or non-apical. RV position was classified as apical or non-apical. Echocardiographic LV end-systolic volume index (LVESVi), QRS duration, and clinical outcomes at 12-24 months of follow-up were evaluated with respect to the lead tip position. The primary trial endpoint was the proportion of patients with a worsened HF clinical composite response, scored as improved, unchanged, or worsened.

RESULTS

Totally 346 patients included in this analysis were followed for a median of 12.6 months (interquartile range: 11.9-23.9 months). The proportion of worsened HF clinical composite response did not correlate with lead position, whereas a significantly greater decrease in the powered secondary endpoint of LVESVi was observed with the non-apical vs. the apical LV lead positions. CRT-paced QRS duration was significantly shorter than at baseline in patients with lateral vs. non-lateral LV position, as well non-apical vs. apical LV position. The incidence of composite endpoint of death and first hospitalization for HF was lower in the LV lateral than in the non-lateral (HR 0.44; 95% CI 0.19-0.99; P= 0.04), and in the LV non-apical than in the apical group (HR 0.27; 95% CI 0.11-0.63; P= 0.001). No significant differences were observed between RV apical and non-apical positions of the lead tip.

CONCLUSIONS

A more favourable outcome of CRT with regard to LV reverse remodelling and the composite of time to death or first HF hospitalization was observed when the LV lead tip was implanted in the lateral wall, away from the apex, while the position of the RV lead tip was indifferent. The long-term change in QRS duration was significantly associated with the position of the LV lead tip. ClinicalTrials.gov Identifier: NCT00271154.