Electrophysiological demonstration of nonselective His-Purkinje system capture with para-Hisian pacing

BACKGROUND

The adverse effects of conventional right ventricular (RV) apical pacing prompted the search for more physiological pacing sites, such as selective and nonselective His bundle pacing (HBP), a variant of nonselective HBP (para-Hisian pacing), and mid-septal pacing. However, knowledge of their true benefit on the physiology of ventricular activation, lead stability, and pacing thresholds is limited.

METHODS AND RESULTS

We included 152 consecutive patients (mean age 61 ± 24, 63% men) in this retrospective study. Of these, 137 patients with different bradyarrhythmias underwent active fixation lead implantation at the RV apex (n = 54), para-Hisian region (n = 66), or mid interventricular septum (n = 17). Fifteen patients with ventricular preexcitation due to an accessory pathway not undergoing pacing were included as controls. A 12‑lead ECG was recorded in all patients, and cardiac electrical synchrony was assessed using the Synchromax® cross-correlation cardiac synchrony index (CSI).

RESULTS

QRS duration was prolonged in all pacing sites: from 114 ± 28 to 160 ± 29 (RV apex), from 110 ± 28 to 122 ± 29 (para-Hisian), and from 121 ± 24 to 154 ± 30 (mid interventricular septum). The CSI was significantly improved only in patients undergoing para-Hisian pacing, despite a slight widening of the QRS interval. There was no difference in pacing thresholds and sensed R-wave voltage between pacing sites. Only 1 lead, implanted at the para-Hisian region (1.5%), was dislodged towards the mid septum 48 h after implantation but did not require repositioning.

CONCLUSIONS

QRS duration was not associated with changes in CSI, meaning that QRS width does not significantly affect electrical synchrony.

Apical or Septal Right Ventricular Location in Patients Receiving Defibrillation Leads: A Systematic Review and Meta-Analysis

This study reviews the published data comparing the efficacy and safety of apical and septal right ventricle defibrillator lead positioning at 1-year follow-up. Systemic research on Medline (PubMed), ClinicalTrials.gov, and Embase was performed using the keywords "septal defibrillation," "apical defibrillation," "site defibrillation," and "defibrillation lead placement," including implantable cardioverter-defibrillator and cardiac resynchronization therapy devices. Comparisons between apical and septal position were performed regarding R-wave amplitude, pacing threshold at a pulse width of 0.5 ms, pacing and shock lead impedance, suboptimal lead performance, left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter, readmissions due to heart failure and mortality rates. A total of 5 studies comprising 1438 patients were included in the analysis. Mean age was 64.5 years, 76.9% were male, with a median LVEF of 27.8%, ischemic etiology in 51.1%, and a mean follow-up period of 26.5 months. The apical lead placement was performed in 743 patients and septal lead placement in 690 patients. Comparing the 2 placement sites, no significant differences were found regarding R-wave amplitude, lead impedance, suboptimal lead performance, LVEF, left ventricular end-diastolic diameter, and mortality rate at 1-year follow-up. Pacing threshold values favored septal defibrillator lead placement (P = 0.003), as well as shock impedance (P = 0.009) and readmissions due to heart failure (P = 0.02). Among patients receiving a defibrillator lead, only pacing threshold, shock lead impedance, and readmission due to heart failure showed results favoring septal lead placement. Therefore, generally, the right ventricle lead placement does not appear to be of major importance.

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.

Global longitudinal strain predicts responders after cardiac resynchronization therapy-a systematic review and meta-analysis

To evaluate the association between baseline global longitudinal strain (GLS) and ΔGLS (difference of baseline GLS and follow-up) and cardiac resynchronization therapy (CRT) response defined either with clinical or with echocardiographic characteristics. This meta-analysis was performed in accordance to both the Meta-Analysis of Observational Studies in Epidemiology and Strengthening the Reporting of Observational Studies in Epidemiology guidelines. Two independent investigators performed a comprehensive systematic search in MedLine, EMBASE and Cochrane databases through September 2019 without limitations. Data analysis was performed by using the Review Manager software (RevMan), version 5.3, and Stata 13 software. A p value of less than 0.05 (two-tailed) was considered statistically significant. Twelve studies (1004 patients, mean age 63.8 years old, males 69.4%) provided data on the association of baseline GLS with the response to CRT therapy. We found that CRT responders had significantly better resting GLS values compared with non-responders [GLS mean difference -2.13 (-3.03, -1.23), p < 0.001, I² 78%]. Furthermore, CRT responders had significantly greater improvement of GLS at follow-up compared with non-responders [ΔGLS mean difference -3.20 (-4.95, -1.45), p < 0.001, I² 66%]. These associations remained significant in a subgroup analysis including only studies with similar CRT response definition. In this meta-analysis, we found that CRT responders had a baseline and ΔGLS significantly higher than the non-responders strengthening the central role of GLS as a tool for selecting candidates for CRT. Furthermore, improved GLS values after CRT may be used to better define CRT responders.

Merits of Different Ventricular Lead Locations on Left Ventricular Myocardial Strain and Dyssynchrony in Patients with Cardiac Resynchronization Therapy

BACKGROUND

The idea behind cardiac resynchronization therapy (CRT) is to pace both ventricles resulting in a synchronized electro-mechanical coupling of the left ventricle (LV), meaning every effort should be made to improve the percentage of CRT responders.

OBJECTIVES

This study aimed at demonstrating the short-term effect of right ventricular apical (RVA) and mid-septal (RVS) lead locations combined with different LV lead positions on LV myocardial strain, dyssynchrony, and clinical outcomes.

METHODS

We examined 60 patients with indication for CRT before and after 6 months of implantation for clinical outcome and CRT response (6-min walk test [6MWT], NYHA class, decrease in left ventricular end systolic volume [LVESV] by >15%), dyssynchrony, and myocardial strain.

RESULTS

After 6 months of follow-up, the two RV lead locations represented a significant improvement in 6MWT, left ventricular ejection fraction, and LVESV in comparison to baseline values, but no significant difference was found between both groups. With regards to NYHA class improvement, p values were insignificant between the groups (0.44 and 0.88) at baseline and 6 months after implantation, respectively. The mean 6MWT was 273.8 m in the RVA group compared to 279.0 m in the RVS group (p = 0.84) at baseline. After 6 months of CRT implantation, the 6MWT mean was 326.5 m in the RVA group compared to 316.2 m in the RVS group (p = 0.74). The posterolateral cardiac vein site showed a significant improvement when combined with RVS location in interventricular and intraventricular dyssynchrony, global longitudinal strain, global circumferential strain, and apical circumferential strain (p = 0.01 0.032, 0.02, 0.005, and 0.049), respectively.

CONCLUSION

RVS is not inferior and provides a good alternative to RVA pacing in short-term follow-up. However, the QRS duration, myocardial strain, and dyssynchrony varies depending on RV and LV stimulation sites. Long-term morbidity and mortality outcomes according to LV lead location in coronary sinus need more assessment.

Influence of the Right Ventricular Lead Location on Ventricular Arrhythmias in Cardiac Resynchronization Therapy

Background:

The influence of different right ventricular lead locations on ventricular arrhythmias (VTA) in patients with a cardiac resynchronization therapy (CRT) is not clear. This study aimed to evaluate the influence on VTA in patients with a CRT when right ventricular lead was positioned at the right ventricular middle septum (RVMS) and the right ventricular apical (RVA).

Methods:

A total of 352 patients implanted with a CRT-defibrillator (CRT-D) between May 2012 and July 2016 in the Department of Cardiology of Anhui Provincial Hospital were included. Two-year clinical and pacemaker follow-up data were collected to evaluate the influence of the right ventricular lead location on VTA. Patients were divided into the RVMS group (n = 155) and the RVA group (n = 197) based on the right ventricular lead position. The VTA were compared between these two groups using a Kaplan-Meier curve and Cox multivariate analysis.

Results:

When the left ventricular lead location was not considered, RVMS and RVA locations did not affect VTA. However, the subgroup analysis results showed that when the left ventricular lead was positioned at the anterolateral cardiac vein (ALCV), the RVMS group had an increased risk of ventricular arrhythmias and appropriate defibrillation (hazard ratio [HR] = 3.29, P = 0.01 and HR = 4.33, P < 0.01, respectively); when the left ventricular lead was at the posterolateral cardiac vein (PLCV), these risks in the RVMS group decreased (HR = 0.45, P = 0.02 and HR = 0.33, P < 0.01, respectively), and when the left ventricular lead was at the lateral cardiac vein, there was no difference between the two groups. In regard to inappropriate defibrillation, there was no significant difference among all these groups.

Conclusions:

When the left ventricular lead was positioned at ALCV or PLCV, the right ventricular lead location was associated with VTA and appropriate defibrillation after CRT. Greater distances between leads not only improved cardiac function but also may reduce the risk of VTA.

Clinical and echocardiographic response of apical vs nonapical right ventricular lead position in CRT: A meta-analysis

Background

Traditionally the right ventricular (RV) pacing lead is placed in the RV apex in cardiac resynchronization therapy (CRT). It is not clear whether nonapical placement of the RV lead is associated with a better response to CRT. We aimed to perform a meta‐analysis of all randomized controlled trials (RCTs) that compared apical and nonapical RV lead placement in CRT.

Methods

We searched PubMed, EMBASE, Cochrane, Scopus, and relevant references for studies and performed meta‐analysis using random effects model. Our main outcome measures were all‐cause mortality, composite of death and heart failure hospitalization, improvement in ejection fraction (EF), left ventricle end‐diastolic volume (LVEDV), left ventricle end‐systolic volume (LVESV), and adverse events.

Results

Seven RCTs with a total population of 1641 patients (1199 apical and 492 nonapical) were included in our meta‐analysis. There was no difference in all‐cause mortality (5% vs 4.3%, odds ratio (OR) = 0.86; 95% confidence interval (CI) 0.45‐1.64; P = .65; I² = 11%) and a composite of death and heart failure hospitalization (14.2% vs 12.9%, OR = 0.92; 95% CI: 0.61‐1.38; P = .68; I² = 0) between apical and nonapical groups. No difference in improvement in EF (Weighted mean difference (WMD) = 0.37; 95% CI: −2.75‐3.48; P = .82; I² = 68%), change in LVEDV (WMD = 3.67; 95% CI: −4.86‐12.20; P = .40; I² = 89%) and LVESV (WMD = −1.20; 95% CI: −4.32‐1.91; P = .45; I² = 0) were noted between apical and nonapical groups. Proportion of patients achieving >15% improvement in EF was similar in both groups (OR = 0.85; 95% CI: 0.62‐1.16; P = .31; I² = 0).

Conclusion

In patients with CRT, nonapical RV pacing is not associated with improved clinical and echocardiographic outcomes compared with RV apical pacing.

Right heart-pulmonary circulation unit and cardiac resynchronization therapy

Clinical response to cardiac resynchronization therapy (CRT) has been known for years to be highly variable, with a spectrum of responses from no change or even deterioration of cardiac function to spectacular improvements. In the plethora of clinical, echocardiographic, biohumoral, and electrophysiological predictors of response to CRT and postimplant issues besides patient selection, the role of right ventricular (RV) function has been largely overlooked. In reviewing current evidence, we noticed conflicting results between observational studies and randomized trials not only concerning the impact of baseline RV function on CRT efficacy but also on the effects of CRT on RV size and function. Hence, we aimed to provide a critical reappraisal of current knowledge and unresolved issues on the reciprocal interactions between RV function and CRT, shifting the spotlight on the concept of right heart pulmonary circulation unit and on the clinical and prognostic significance of impaired ventricular-arterial coupling reserve. In this viewpoint, we propose that (1) CRT should not be denied to potential candidate because of "isolated" RV dysfunction and (2) assessment of baseline right heart pulmonary circulation unit and its dynamic response to pharmacological stress should be considered in future studies, as well as in the preimplant evaluation of individual candidates among other clinical factors.

Comparison of right ventricular septal pacing and right ventricular apical pacing in patients receiving cardiac resynchronization therapy defibrillators: the SEPTAL CRT Study

AIMS

Cardiac resynchronization therapy (CRT) is a recommended treatment of heart failure (HF) patients with depressed left ventricular ejection fraction and wide QRS. The optimal right ventricular (RV) lead position being a matter of debate, we sought to examine whether RV septal (RVS) pacing was not inferior to RV apical (RVA) pacing on left ventricular reverse remodelling in patients receiving a CRT-defibrillator.

METHODS AND RESULTS

Patients (n = 263, age = 63.4 ± 9.5 years) were randomly assigned in a 1:1 ratio to RVS (n = 131) vs. RVA (n = 132) pacing. Left ventricular end-systolic volume (LVESV) reduction between baseline and 6 months was not different between the two groups (-25.3 ± 39.4 mL in RVS group vs. -29.3 ± 44.5 mL in RVA group, P = 0.79). Right ventricular septal pacing was not non-inferior (primary endpoint) to RVA pacing with regard to LVESV reduction (average difference = -4.06 mL; P = 0.006 with a -20 mL non-inferiority margin). The percentage of 'echo-responders' defined by LVESV reduction >15% between baseline and 6 months was similar in both groups (50%) with no difference in the time to first HF hospitalization or death (P = 0.532). Procedural or device-related serious adverse events occurred in 68 patients (RVS = 37) with no difference between the two groups (P = 0.401).

CONCLUSION

This study demonstrates that septal RV pacing in CRT is non-inferior to apical RV pacing for LV reverse remodelling at 6 months with no difference in the clinical outcome. No recommendation for optimal RV lead position can hence be drawn from this study.

CLINICALTRIALS GOV NUMBER

NCT 00833352.

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.

Is cardiac resynchronization therapy for right ventricular failure in pulmonary arterial hypertension of benefit?

Pulmonary arterial hypertension is a manifestation of a group of disorders leading to pulmonary vascular remodeling and increased pulmonary pressures. The right ventricular (RV) response to chronic pressure overload consists of myocardial remodeling, which is in many ways similar to that seen in left ventricular (LV) failure. Maladaptive myocardial remodeling often leads to intraventricular and interventricular dyssychrony, an observation that has led to cardiac resynchronization therapy (CRT) for LV failure. CRT has proven to be an effective treatment strategy in subsets of patients with LV failure resulting in improvement in LV function, heart failure symptoms, and survival. Current therapy for pulmonary arterial hypertension is based on decreasing pulmonary vascular resistance, and there is currently no effective therapy targeting the right ventricle or maladaptive ventricular remodeling in these patients. This review focuses on the RV response to chronic pressure overload, its effect on electromechanical coupling and synchrony, and how lessons learned from left ventricular cardiac resynchronization might be applied as therapy for RV dysfunction in the context of pulmonary arterial hypertension.

Interventricular lead separation is critical for NT-proBNP reduction after cardiac resynchronization therapy

AIMS

Effective cardiac resynchronization therapy may depend upon the distance between left ventricular (LV) and right ventricular (RV) pacing leads. We assessed the influence of lead separation upon circulating NT-proBNP.

MATERIALS & METHODS

In total, 132 patients underwent assessment, including NT-proBNP assay, before and after cardiac resynchronization therapy. 3D lead separation was calculated from postero-anterior and lateral chest radiography.

RESULTS

Lead separation correlated with NT-proBNP reduction (r = 0.25; p = 0.004). Circulating NT-proBNP only fell in those with lead separation in the upper two quartiles. Deteriorating NT-proBNP occurred in 44 patients. Lead separation was less in these patients compared with those with an improvement (corrected 3D lead separation: 148.0 ± 5.38 and 170.5 ± 4.21 mm, respectively; p = 0.0018).

CONCLUSION

Left ventricular-right ventricular lead separation correlates with postcardiac resynchronization therapy improvements in circulating NT-proBNP, a powerful marker of heart failure status and prognosis. Attention should be paid to achieving maximal lead separation at implantation.

Influence of pacing site characteristics on response to cardiac resynchronization therapy

BACKGROUND

Transmural scar occupying left ventricular (LV) pacing regions has been associated with reduced response to cardiac resynchronization therapy (CRT). However, spatial influences of lead tip delivery relative to scar at both pacing sites remain poorly explored. This study evaluated scar distribution relative to LV and right ventricular (RV) lead tip placement through coregistration of late gadolinium enhancement MRI and cardiac computed tomographic (CT) findings. Influences on CRT response were assessed by serial echocardiography.

METHODS AND RESULTS

Sixty patients receiving CRT underwent preimplant late gadolinium enhancement MRI, postimplant cardiac CT, and serial echocardiography. Blinded segmental evaluations of mechanical delay, percentage scar burden, and lead tip location were performed. Response to CRT was defined as a reduction in LV end-systolic volume ≥15% at 6 months. The mean age and LV ejection fraction were 64±9 years and 25±7%, respectively. Mean scar volume was higher among CRT nonresponders for both the LV (23±23% versus 8±14% [P=0.01]) and RV pacing regions (40±32% versus 24±30% [P=0.04]). Significant pacing region scar was identified in 13% of LV pacing regions and 37% of RV pacing regions. Absence of scar in both regions was associated with an 81% response rate compared with 55%, 25%, and 0%, respectively, when the RV, LV, or both pacing regions contained scar. LV pacing region dyssynchrony was not predictive of response.

CONCLUSIONS

Myocardial scar occupying the LV pacing region is associated with nonresponse to CRT. Scar occupying the RV pacing region is encountered at higher frequency and seems to provide a more intermediate influence on CRT response.

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.

Paced QRS duration as a predictor for clinical heart failure events during right ventricular apical pacing in patients with idiopathic complete atrioventricular block: results from an observational cohort study (PREDICT-HF)

AIMS

The aim of this study was to investigate the predictive ability of paced QRS duration (pQRSd) for heart failure events among patients receiving right ventricular apical pacing (RVAP).

METHODS AND RESULTS

A total of 194 patients with complete atrioventricular block receiving pacemaker treatment were enrolled and stratified to group 1, pQRSd < 160 ms, n = 53; group 2, 160 ≤ pQRSd < 190 ms, n = 97; and group 3, pQRSd ≥ 190 ms, n = 44. Study outcomes were heart failure events, changes in pQRSd, and changes in left ventricular ejection fraction (LVEF). During the 3-year follow-up, the incidence of heart failure events was 9.4, 27.8, and 56.8% in groups 1, 2, and 3, respectively (P < 0.001). Among the patients without heart failure events, the pQRSd at 3 years remained longer than that at baseline (162.1 ± 22.6 vs. 160.9 ± 22.1 ms, P < 0.05), whereas among patients who experienced heart failure events, the prolonged pQRSd at 3 years seemed more pronounced as compared with baseline (184.1 ± 21.1 vs. 179.8 ± 21 ms, P < 0.001). Linear regression demonstrated that a decrease in LVEF was positively correlated with pQRSd over time (relative risk 0.423; P < 0.05). The receiver operating charactersitic curve showed that the cut-off value of pQRSd was 165 ms with a sensitivity of 0.789.

CONCLUSION

A prolonged pQRSd has a detrimental effect on long-term cardiac function during RVAP in patients with complete atrioventricular block. pQRSd could be a useful predictor to identify patients who are at risk for heart failure events during RVAP.

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.

Clinical, laboratory, and pacing predictors of CRT response

A decade of research has established the role of cardiac resynchronization therapy (CRT) in medically refractory, moderate to severe systolic heart failure (HF) with intraventricular conduction delay. CRT is an electrical therapy instituted to reestablish ventricular synchronization in order to improve cardiac function and favorably modulate the neurohormonal system. CRT confers a mortality benefit, improved HF hospitalizations, and functional outcome in this population, but not all patients consistently demonstrate a positive CRT response. The nonresponder rate varies from 20% to 40%, depending on the defined response criteria. Efforts to improve response to CRT have focused on a number of fronts. Methods to optimize the correction of electrical and mechanical dyssynchrony, which is the primary target of CRT, has been the focus of research, in addition to improving patient selection and optimizing post-implant care. However, a major issue in dealing with improving nonresponse rates has been finding an accurate and generally accepted definition of "response" itself. The availability of a standard consensus definition of CRT response would enable the estimation of nonresponder burden accurately and permit the development of strategies to improve CRT response. In this review, we define various aspects of "response" to CRT and outline variability in the definition criteria and the problems with its inconsistencies. We describe clinical, laboratory, and pacing predictors that influence CRT response and outcome and how to optimize response.

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.

Correlation of body mass index and responder status in heart failure patients after cardiac resynchronization therapy: Does the obesity paradox exist?

Aims: We investigated the influence of body mass index (BMI) on the prevalence of responder status in chronic heart failure patients after cardiac resynchronization therapy (CRT).

Methods: Data on 169 patients with resynchronization therapy were analyzed. Patients were categorized on the basis of the BMI measured at device implantation according to the WHO classification, as normal (BMI: 18.5–24.9 kg/m2), overweight (BMI: 25–29.9 kg/m2) or obese (BMI:≥30 kg/m2). Patients were considered responders if left ventricular ejection fraction was increased by at least 5% at 6-month follow-up.

Results: The mean age in the study population was 60.9±10.86 years (females 29%). The BMI subgroups did not exhibit any significant differences in baseline characteristics (age, gender, left ventricular ejection fraction or NYHA class). Elevated BMIs were associated with higher prevalence of responder status (overweight: 71.4%, obese: 63.0%) relative to subjects with a normal BMI (44.7%) (p=0.015).

Conclusions: In this CRT population, overweight status was associated with a more favorable response to CRT, indicating that the response may possibly be influenced by factors other than those directly related to the heart status or the technical details of the CRT.