Mid-term outcomes of triple-site vs. conventional cardiac resynchronization therapy: A preliminary study

Evolving Concepts in Cardiac Physiologic Pacing in the Era of Conduction System Pacing

Cardiac physiologic pacing (CPP) has become a well-established therapy for patients with cardiomyopathy (left ventricular ejection fraction <35%) in the presence of a left bundle branch block. In addition, CPP can be highly beneficial in patients with pacing-induced cardiomyopathy and patients with existing cardiomyopathy expected to have a right ventricular pacing burden of >40%. The benefits of CPP with traditional biventricular pacing are only realized if adequate resynchronization can be achieved. However, left ventricular lead implantation can be limited by individual anatomic variation within the coronary venous system and can be adversely affected by underlying abnormal myocardial substrate (i.e., scar tissue), especially if located within the basal lateral wall. In the last 7 years the investigation of conduction system pacing (CSP) and its potential salutary benefits are being realized and have led to a rapid evolution in the field of cardiac resynchronization pacing. However, supportive evidence for CSP for patients eligible for cardiac resynchronization remains limited compared with data available for biventricular cardiac resynchronization, mostly derived from leading CSP investigative centers. In this review, we perform an up-to-date comprehensive review of the available literature on CPP.

Acute Hemodynamic Effect of a Novel Dual-Vein, Multisite Biventricular Pacing Configuration

BACKGROUND

Biventricular pacing (BVP) from multiple left ventricular (LV) sites could enhance the efficacy of cardiac resynchronization therapy (CRT) by engaging a greater myocardial mass.

OBJECTIVES

The goal of this study was to evaluate the acute hemodynamic effect of various multisite pacing (MSP) configurations against conventional BVP.

METHODS

Twenty patients with nonischemic dilated cardiomyopathy and left bundle branch block (mean age: 59 ± 14 years; LV ejection fraction: 27% ± 6%; native QRS: 171 ± 16 milliseconds) were investigated during a routine CRT implant procedure. In addition to conventional right atrial and right ventricular leads, 2 quadripolar leads were placed in the distant coronary venous branches. LV hemodynamics was evaluated by using a micromanometer-tipped catheter during atrioventricular BVP with 4 LV lead configurations: single-lead conventional BVP; single-lead multipoint pacing; triventricular pacing from distal dipoles of 2 LV leads; and maximum MSP (MSP-Max) from 4 dipoles of 2 LV leads.

RESULTS

Compared with right atrial pacing, any BVP configuration produced a significant increase in the maximal LV diastolic pressure rise (LVdP/dTMax) (a median relative increase of 28% [IQR: 8%-45%], 25% [IQR: 18%-46%], 36% [IQR: 18%-54%], and 38% [IQR: 28%-58%], respectively; all, P < 0.001). MSP-Max but no other multisite BVP generated a significant increase of the maximal LVdP/dTMax than conventional BVP (P = 0.041). Increased LVdP/dTMax during MSP-Max was associated with greater LV diameter and lower LV ejection fraction, independently of the QRS width.

CONCLUSIONS

The study shows the hemodynamic advantage of a novel dual-vein MSP-Max configuration that could be useful for CRT in patients with advanced LV remodeling.

Multi-lead pacing for cardiac resynchronization therapy in heart failure: a meta-analysis of randomized controlled trials

Aims

Multi-lead pacing is a potential therapy to improve response to cardiac resynchronization therapy (CRT) by providing rapid activation of the myocardium from multiple sites. Here, we perform a meta-analysis of randomized controlled trials to assess the efficacy of multi-lead pacing.

Methods and results

A literature search was performed which identified 251 unique records. After screening, 6 studies were found to meet inclusion criteria, with 415 patients included in the meta-analysis. Four studies performed multi-lead pacing with two left ventricular (LV) leads and one right ventricular (RV) lead. One study used two RV leads and one LV lead, and one study used both configurations. There was no difference between multi-lead pacing and conventional CRT in LV end-systolic volume [mean difference (MD) -0.54 mL, P = 0.93] or LV ejection fraction (MD 1.42%, P = 0.40). There was a borderline significant improvement in Minnesota Living With Heart Failure Questionnaire score for multi-lead pacing vs. conventional CRT (MD -4.46, P = 0.05), but the difference was not significant when only patients receiving LV-only multi-lead pacing were included (MD -3.59, P = 0.25). There was also no difference between groups for 6-min walk test (MD 15.06 m, P = 0.38) or New York Heart Association class at follow-up [odds ratio (OR) 1.49, P = 0.24]. There was no difference in mortality between groups (OR 1.11, P = 0.77).

Conclusion

This meta-analysis does not support the use of multi-lead pacing for CRT delivery. However, significant variation between studies was noted, and therefore a benefit for multi-lead pacing in select patients cannot be excluded, and further investigation may be warranted.

The evolution of cardiac resynchronization therapy and an introduction to conduction system pacing: a conceptual review

In chronic systolic heart failure and conduction system disease, cardiac resynchronization therapy (CRT) is the only known non-pharmacologic heart failure therapy that improves cardiac function, functional capacity, and survival while decreasing cardiac workload and hospitalization rates. While conventional bi-ventricular pacing has been shown to benefit patients with heart failure and conduction system disease, there are limitations to its therapeutic success, resulting in widely variable clinical response. Limitations of conventional CRT evolve around myocardial scar, fibrosis, and inability to effectively simulate diseased tissue. Studies have shown endocardial stimulation in closer proximity to the specialized conduction system is more effective when compared with epicardial stimulation. Several observational and acute haemodynamic studies have demonstrated improved electrical resynchronization and echocardiographic response with conduction system pacing (CSP). Our objective is to provide a systematic review of the evolution of CRT, and an introduction to CSP as an intriguing, though experimental physiologic alternative to conventional CRT.

Intraoperative Epicardial Triventricular Pacing in a Pediatric Patient

Cardiac resynchronization therapy (CRT) is used as an adjunctive therapy in adults with advanced heart failure but remains less commonly applied in pediatric patients. Further, CRT is traditionally conducted via biventricular transvenous pacing from the right ventricle and coronary sinus to activate the left ventricle and improve electromechanical synchrony; however, triventricular pacing, in which a third ventricular lead is utilized to activate an additional ventricular location, has been shown to be a feasible therapeutic alternative to typical CRT in patients with advanced heart failure or nonresponders. Limited adult studies involving triventricular pacing have been performed to date but no pediatric data are available. Thus, we present the case of a 12-month-old patient with congenital complete heart block and subsequent pacemaker-induced cardiomyopathy in whom triventricular epicardial pacing was applied in an effort to increase the available knowledge.

Multisite pacing and myocardial scars: a computational study

Cardiac resynchronization therapy (CRT) is a frequently effective treatment modality for dyssynchronous heart failure, however, 30% of patients do not respond, usually due to suboptimal activation of the left ventricle (LV). Multisite pacing (MSP) may increase the response rate, but its effect in the presence of myocardial scars is not fully understood. We use a computational model to study the outcome of MSP in an LV with scars in two different locations and of two different sizes. The LV was stimulated from anterior, posterior and lateral locations individually and in pairs, while a septal stimulation site represented right ventricular (RV) pacing. Intraventricular pressures were measured, and outcomes evaluated in terms of maximum LV pressure gradient (dP/dt_max)- change compared to isolated RV pacing. The best result obtained using various LV pacing locations included a combination of sites remote from scars and the septum. The highest dP/dt_max increase was achieved, regardless of scar size, using MSP with one pacing site located on the LV free wall opposite to the scar and one site opposite to the septum. These in silico modelling results suggest that making placement of pacing electrodes dependent on location of scarring, may alter acute haemodynamics and that such modelling may contribute to future CRT optimization.

Cardiac resynchronization therapy non-responder to responder conversion rate in the more response to cardiac resynchronization therapy with MultiPoint Pacing (MORE-CRT MPP) study: results from Phase I

Aims

To assess the impact of MultiPoint™ Pacing (MPP)—programmed according to the physician’s discretion—in non-responders to standard biventricular pacing after 6 months.

Methods and results

The study enrolled 1921 patients receiving a quadripolar cardiac resynchronization therapy (CRT) system capable of MPP™ therapy. A core laboratory assessed echocardiography at baseline and 6 months and defined volumetric non-response to biventricular pacing as <15% reduction in left ventricular end-systolic volume (LVESV). Clinical sites randomized patients classified as non-responders in a 1:1 ratio to receive MPP (236 patients) or continued biventricular pacing (231 patients) for an additional 6 months and evaluated rate of conversion to echocardiographic response. Baseline characteristics of both groups were comparable. No difference was observed in non-responder to responder conversion rate between MPP and biventricular pacing (31.8% and 33.8%, P = 0.72). In the MPP arm, 68 (29%) patients received MPP programmed with a wide LV electrode anatomical separation (≥30 mm) and shortest LV1–LV2 and LV2–RV timing delays (MPP-AS); 168 (71%) patients received MPP programmed with other settings (MPP-Other). MPP-AS elicited a significantly higher non-responder conversion rate compared to MPP-Other (45.6% vs. 26.2%, P = 0.006) and a trend in a higher conversion rate compared to biventricular pacing (45.6% vs. 33.8%, P = 0.10).

Conclusions

After 6 months, investigator-discretionary MPP programming did not significantly increase echocardiographic response compared to biventricular pacing in CRT non-responders.

Benefits of Multisite/Multipoint Pacing to Improve Cardiac Resynchronization Therapy Response

This article provides a general overview of the underlying mechanisms that support pacing from more discrete points and/or a wider vector (multisite and multipoint pacing) to improve left ventricular resynchronization. We performed a critical overview of the current literature and to identify some remaining knowledge gaps to spur further research. It was not our goal to provide a systematic review with a comprehensive bibliography, but rather to focus on selected publications that, in our opinion, have either expertly reviewed a specific aspect of cardiac resynchronization therapy or have been landmark studies in the field.

Long-term reverse remodeling by cardiac resynchronization therapy with MultiPoint Pacing: A feasibility study of noninvasive hemodynamics-guided device programming

BACKGROUND

Cardiac resynchronization therapy (CRT) with multipoint left ventricular (LV) pacing (MultiPoint Pacing [MPP]) improves acute hemodynamics and chronic outcomes in comparison to conventional biventricular pacing (BiV), though MPP programming questions persist.

OBJECTIVES

In this multicenter feasibility study, we evaluated the feasibility of using noninvasive systolic blood pressure (SBP) to guide MPP programming and assessed the chronic 6-month echocardiographic CRT response.

METHODS

Patients implanted with MPP-enabled CRT-defibrillator devices underwent noninvasive hemodynamic assessment (finger arterial pressure) during a pacing protocol that included atrial-only pacing and various BiV and MPP configurations. Each configuration was repeated 4 times, alternating with a reference pacing configuration, to calculate the SBP difference relative to reference (ΔSBP). CRT configurations with the greatest ΔSBP were programmed. An independent core laboratory analyzed baseline and 6-month echocardiograms, with CRT response defined as a 6-month reduction in LV end-systolic volume ≥ 15%.

RESULTS

Forty-two patients (71% male; LV ejection fraction 30.3% ± 7.5%; QRS duration 161 ± 19 ms; 26% had ischemic cardiomyopathy) were enrolled in 4 European centers. Relative to atrial-only pacing, the best BiV and best MPP configurations produced significant SBP elevations of 3.1 ± 4.2 (P < .01) and 4.1 ± 4.1 mm Hg (P < .01), respectively (BiV vs MPP; P < .01). Greater SBP elevations were associated with the best MPP compared with the best BiV configurations in 29 of 37 patients completing the pacing protocol (78%). Of MPP-programmed patients completing the 6-month follow-up visit, 23 of 27 (85%) were classified as CRT responders (6-month reduction in LV end-systolic volume 37.0% ± 13.6%).

CONCLUSION

Acute noninvasive hemodynamics after CRT device implantation predominantly favored MPP over BiV programming. MPP programming guided by noninvasive hemodynamics resulted in positive LV structural remodeling.

Triple-site pacing for cardiac resynchronization in permanent atrial fibrillation: follow-up results from a prospective observational study

Aims

Cardiac Resynchronization Therapy (CRT) is associated with a particularly high non-response rate in patients with atrial fibrillation (AF). We aimed to assess the effectiveness of triple-site (Tri-V) pacing CRT in this population.

Methods and results

Prospective observational study of patients with permanent AF who underwent CRT implantation with an additional right ventricle lead in the outflow tract septal wall. After implantation, programming mode (Tri-V or biventricular pacing) was selected based on cardiac output determination. Patients were classified as responders if NYHA class was reduced by at least one level and echocardiographic ejection fraction (EF) increased ≥ 10%, and as super-responders if in NYHA class I and EF ≥ 50%. Forty patients (93% male, mean age 72 ± 10 years) were included. Thirty-three were programmed in Tri-V. The following results pertain to this subgroup. At baseline, 58% were in NYHA class III and 36% NYHA class II. At 1 year follow-up, Minnesota QoL score was reduced (36 ± 23 vs. 8 ± 6; P = 0.001) and the 6MWT distance improved (384 ± 120 m to 462 ± 87 m, P = 0.003). Mean EF increased (26% ± 8 vs. 39 ± 10; P < 0.001 at 6 months and 41 ± 10; P < 0.001 at 12 months). Responder rate was 59% at 6 months and 79% at 12 months. Super-responder rate was 9% at 6 months and 16% at 12 months. One year survival free from heart failure hospitalization was 87.9%.

Conclusion

Tri-V CRT yielded higher response and super-response rates than usually reported for CRT in patients with permanent AF using clinical and remodeling criteria.

Comparison of triple-site ventricular pacing versus conventional cardiac resynchronization therapy in patients with systolic heart failure: A meta-analysis of randomized and observational studies

Background

Conventional cardiac resynchronization therapy (CRT, Bi‐V) is associated with no response in about 40% patients due to an insufficient resynchronization. Some studies showed triple‐site ventricular (Tri‐V) pacing had greater benefits compared with Bi‐V pacing, but the results of these studies were conflicting. We hypothesized that Tri‐V pacing had greater benefits on long‐term outcomes compared with Bi‐V pacing in patients with heart failure.

Methods

PubMed, EMBASE, and the Cochrane Library were searched for clinical studies with related outcomes. Weighted mean differences (WMD) and 95% confidence intervals (CIs) were calculated to compare the change in left ventricular ejection fraction (LVEF), left ventricular geometry, functional capacity, and quality of life between Tri‐V pacing group and control group.

Results

Five trials with 251 patients were included in the analysis. Patients in the Tri‐V pacing group had a greater improvement in LVEF (WMD 4.04; 95% CI 2.15‐5.92, P < .001) and NYHA classes (WMD −0.27; 95% CI −0.42 to −0.11, P = .001) compared with control group. However, there were no significant differences in left ventricular geometry, six‐min walk distance, or Minnesota Living With Heart Failure Questionnaire score between the two groups. The subgroup analyses showed there might be a greater improvement in LVEF in the Tri‐V pacing group in patients with QRS duration ≥ 155 ms (WMD 5.60; 95% CI 3.09‐8.10, P < .001).

Conclusions

The present analysis suggests that Tri‐V pacing has greater benefits in terms of an improvement in LVEF and functional capacity in patients with systolic heart failure, especially in patients with the duration of QRS ≥ 155 ms.

Comparison of single-coil lead versus dual-coil lead of implantable cardioverter defibrillator on lead-related venous complications in a canine model

PURPOSE

Dual- coil lead (DCL) of implantable cardioverter defibrillator (ICD) is preferred clinically in patients. However, it is related to higher risk of venous stenosis and thrombosis. The present study was done to compare the fibrosis and extraction of the leads between the single-coil lead (SCL) and DCL in animal models.

METHODS

This was a chronic animal study with a follow-up duration of 6 months. Twenty mongrel dogs were randomly divided into DCL group or SCL group. Venography was performed before the sacrifice to evaluate the venous stenosis in vivo. The maximum pulling-out tension of the ICD lead was measured by a tensometer. Hematoxylin-eosin stain and toluidine blue O stain were applied to show the pathological changes of the superior vena cava (SVC) to evaluate the fibrosis and the thickness of the SVC adjacent to the leads.

RESULTS

The DCL group showed higher incidence of venous stenosis (OR = 31.5; 95% CI, 2.35-422.3; p = 0.005). It revealed increased tension to extract the leads in the DCL group (5.96 ± 1.86 vs. 3.68 ± 1.46 N, p = 0.027). The difference of venous wall thickness of SVC was 4.3 ± 0.3 fold-changes between two groups (p = 0.007). Moreover, the degree of venous wall fibrosis in DCL group was more serious than that it in SCL group (3.61 ± 1.26 vs. 1.08 ± 1.35 mm², p = 0.015).

CONCLUSION

The DCL was proved to increase thrombosis, fibrosis, and stenosis in the SVC. Likewise, the DCL was mechanically harder to be extracted than the SCL. Our study showed that lead-related complications of the DCLs were higher than those of the SCLs regardless of the equal defibrillation thresholds between them. Results of the present study would help to choose the proper lead which could be removed.

Developments in Cardiac Resynchronisation Therapy

Cardiac resynchronisation therapy (CRT) is an important therapy for patients with heart failure with a reduced ejection fraction and interventricular conduction delay. Large trials have established the role of CRT in reducing heart failure hospitalisations and improving symptoms, left ventricular (LV) function and mortality. Guidelines from major medical societies are consistent in support of CRT for patients with New York Health Association (NYHA) class II, III and ambulatory class IV heart failure, reduced LV ejection fraction and QRS prolongation, particularly left bundle branch block. The current challenge facing practitioners is to maximise the rate of patients who respond to CRT and the magnitude of that response. Current areas of interest for achieving these goals include tailoring patient selection, individualising LV lead placement and application of new technologies and techniques for CRT delivery.

Haemodynamic effects of cardiac resynchronization therapy using single-vein, three-pole, multipoint left ventricular pacing in patients with ischaemic cardiomyopathy and a left ventricular free wall scar: the MAESTRO study

AIMS

The clinical response to cardiac resynchronization therapy (CRT) is variable. Multipoint left ventricular (LV) pacing could achieve more effective haemodynamic response than single-point LV pacing. Deployment of an LV lead over myocardial scar is associated with a poor haemodynamic response to and clinical outcome of CRT. We sought to determine whether the acute haemodynamic response to CRT using three-pole LV multipoint pacing (CRT3P-MPP) is superior to that to conventional CRT using single-site LV pacing (CRTSP) in patients with ischaemic cardiomyopathy and an LV free wall scar.

METHODS AND RESULTS

Sixteen patients with ischaemic cardiomyopathy [aged 72.6 ± 7.7 years (mean ± SD), 81.3% male, QRS: 146.0 ± 14.2 ms, LBBB in 14 (87.5%)] in whom the LV lead was intentionally deployed straddling an LV free wall scar (assessed using cardiac magnetic resonance), underwent assessment of LV + dP/dtmax during CRT3P-MPP and CRTSP. Interindividually, the ΔLV + dP/dtmax in relation to AAI pacing with CRT3P-MPP (6.2 ± 13.3%) was higher than with basal and mid CRTSP (both P < 0.001), but similar to apical CRTSP. Intraindividually, significant differences in the ΔLV + dP/dtmax to optimal and worst pacing configurations were observed in 10 (62.5%) patients. Of the 8 patients who responded to at least one configuration, CRT3P-MPP was optimal in 5 (62.5%) and apical CRTSP was optimal in 3 (37.5%) (P = 0.0047).

CONCLUSIONS

In terms of acute haemodynamic response, CRT3P-MPP was comparable an apical CRTSP and superior to basal and distal CRTSP. In the absence of within-device haemodynamic optimization, CRT3P-MPP may offer a haemodynamic advantage over a fixed CRTSP configuration.

Optimizing CRT - Do We Need More Leads and Delivery Methods

Cardiac resynchronization therapy (CRT) is an established therapeutic option in symptomatic heart failure with reduced ejection fraction and evidence of left ventricular (LV) conduction delay (QRS width ≥120 ms), especially when typical left bundle branch block is present. The rationale behind CRT is restoration of aberrant LV electrical activation. As there is considerable heterogeneity of the LV electrical activation pattern among CRT candidates, an individualized approach with targeting of the LV lead in the region of latest electrical activation while avoiding scar tissue may enhance CRT response. Echocardiography, electro anatomic mapping, and cardiac magnetic resonance imaging with late gadolinium enhancement are helpful to guide such targeted LV lead placement. However, an important limitation remains the anatomy of the coronary sinus, which often does not allow concordant LV lead placement in the optimal region. Epicardial LV lead placement through minimal invasive surgery or endocardial LV lead placement through transseptal punction may overcome this limitation, obviously with an increased complication risk. Furthermore, recent pacing algorithms suggest superiority of LV-only versus biventricular pacing in patients with preserved atrio ventricular (AV) conduction and a typical LBBB pattern. Finally, pacing from only one LV site might not overcome the wide electrical dispersion often seen in patients with LV conduction delays. Therefore, multisite pacing has gained significant interest to improve CRT response. The use of multiple LV leads may potentially lead to more favorable reverse remodeling, improved functional capacity and quality of life in CRT candidates, but adverse events and a shorter battery span are more frequent because of the extra lead. The use of one multipolar LV lead increases the number of pacing configurations within the same coronary sinus side branch (within small distances from each other) without the use of an additional lead. Small observational studies suggest that more effective resynchronization can be achieved with this approach. Finally, there are many reasons for non effective CRT delivery in carefully selected patients with an adequately implanted device. Multidisciplinary, post implantation care inside a dedicated CRT clinic ensures optimal CRT delivery, improves response rate and should be considered standard of care.

Left ventricular wall motion analysis to guide management of CRT non-responders

AIMS

A discordant left ventricular (LV) lead position can be responsible for cardiac resynchronization therapy (CRT) non-response. In this study, tailored optimization of the individual LV wall motion was evaluated for the outcome in these patients.

METHODS AND RESULTS

Two hundred and forty-six CRT outpatients were screened for non-response due to a discordant LV lead. In 17 patients, three-dimensional data of fluoroscopic rotation scan and echocardiography were integrated to analyse the individual LV wall motion with respect to the LV lead position. Optimization was guided by the systolic dyssynchrony index (SDI) and LV ejection fraction (LVEF) during different interventricular (VV)-delay programming. If re-programming failed, implantation of a second LV lead was performed. A discordant or partly concordant LV lead position was found in nearly all patients (16/17, 94%), which contributed to an unchanged baseline amount of LV dyssynchrony with either CRT on or off (SDI 11.3 vs. 11.0%; P = 0.744). In the majority of patients, VV-delay re-programming achieved better resynchronization, 4/17 patients needed implantation of a second LV lead. After 3 months, significant improvement of NYHA functional class (1 class; P = 0.004), peak oxygen consumption (10 vs. 13 mL/min/kg; P = 0.008), LVEF (27 vs. 39%; P = 0.003), and SDI (11.0 vs. 5.8; P = 0.02) was observed. Clinical and echocardiographic responses were found in 77 and 59%, respectively, with even good results on long-term follow-up.

CONCLUSION

Tailored optimization of the individual LV wall motion can lead to significant clinical and echocardiographic improvements in previous CRT non-responders with a discordant LV lead position.

Limitations of chronic delivery of multi-vein left ventricular stimulation for cardiac resynchronization therapy

PURPOSE

Dual-site epicardial left ventricular (LV) pacing represents one strategy to improve acute cardiac resynchronization therapy (CRT) response. However, the feasibility of this approach in the longer term may be hindered by system complexity. We assessed chronic outcomes of patients receiving dual-site LV pacing.

METHODS

Twenty patients with conventional CRT criteria were implanted with dual-site epicardial LV leads connected with bifurcating adapter. Mean energy required to capture the LV was calculated using threshold, impedance and pulse width. Values were obtained during implant and the following day. Follow-up data included lead parameters, ventricular arrhythmias and mortality.

RESULTS

Nineteen patients had successful dual LV lead placement. Mean age was 66 ± 11 years, mean left ventricular ejection fraction (LVEF) 26% ± 8 and 50% ischemic etiology. Mean energy to capture the LV was 1.95 μJ for LV1 during implant, rising to 8.61 μJ at day 1, p = 0.03. The energy required for LV2 was 2.37 μJ during implant, 11.55 μJ the next day, p = 0.004. Eleven percent had LV2 turned off during the implant due to high thresholds and/or a worsened acute hemodynamic response. Eleven percent had LV2 turned off day 1 post implant due to inability to capture LV2 at maximum output. All remaining 15 patients had LV2 programmed off, with a mean time of 255 days from implant. Thirty-two percent of patients received ATP or shock, and sixteen percent died over a mean follow-up of 1271 days. Thirty-seven percent of patients required generator replacement with mean longevity of 42 months, far shorter than the suggested lifespan of the device (58 months), p = 0.006.

CONCLUSION

Multisite epicardial LV lead placement may be acutely feasible and demonstrate beneficial hemodynamic results at implantation. Long-term delivery of this therapy is however problematic due to technical issues with pacing through the bifurcating adapter. This suggests the feasibility of this form of multisite CRT is limited.

Current Evidence and Recommendations for Cardiac Resynchronisation Therapy

The number of people in Europe living with symptomatic heart failure is increasing. Since its advent in the 1990s, cardiac resynchronisation therapy (CRT) has proven beneficial in terms of morbidity and mortality in selected heart failure (HF) patient populations, when combined with optimal pharmacological therapy. We review the evidence for CRT and the populations of HF patients it is currently shown to benefit, and those in which more research needs to be performed.

Left ventricular endocardial or triventricular pacing to optimize cardiac resynchronization therapy in a chronic canine model of ischemic heart failure

Cardiac resynchronization therapy (CRT) is a proven treatment for heart failure but ∼30% of patients appear to not benefit from the therapy. Left ventricular (LV) endocardial and multisite epicardial [triventricular (TriV)] pacing have been proposed as alternatives to traditional LV transvenous epicardial pacing, but no study has directly compared the hemodynamic effects of these approaches. Left bundle branch block ablation and repeated microembolizations were performed in dogs to induce electrical dysynchrony and to reduce LV ejection fraction to <35%. LVdP/d tmax and other hemodynamic indexes were measured with a conductance catheter during LV epicardial, LV endocardial, biventricular (BiV) epicardial, BiV endocardial, and TriV pacing performed at three atrioventricular delays. LV endocardial pacing was obtained with a clinically available pacing system. The optimal site was defined as the site that increased dP/d tmax by the largest percentage. Implantation of the endocardial lead was feasible in all canines ( n = 8) without increased mitral regurgitation seen with transesophageal echocardiography and with full access to the different LV endocardial pacing sites. BiV endocardial pacing increased dP/d tmax more than BiV epicardial and TriV pacing on average ( P < 0.01) and at the optimal site ( P < 0.01). There were no significant differences between BiV epicardial and TriV pacing. BiV endocardial pacing was superior to BiV epicardial and to TriV pacing in terms of acute hemodynamic response. Further investigation is needed to confirm the chronic benefit of this approach in humans.

Implantation feasibility, procedure-related adverse events and lead performance during 1-year follow-up in patients undergoing triple-site cardiac resynchronization therapy: a substudy of TRUST CRT randomized trial

INTRODUCTION

This substudy was to assess implantation feasibility and long-term safety of triple-site resynchronization therapy (CRT) in a series of consecutive patients included in a randomized trial.

METHODS AND RESULTS

One hundred consecutive patients enrolled into Triple-Site Versus Standard Cardiac Resynchronization Therapy Randomized Trial were analyzed. Eligibility criteria included NYHA class III-IV, sinus rhythm, QRS ≥ 120 milliseconds, left ventricular ejection fraction ≤35%, and significant mechanical dyssynchrony. Patients were randomized in a 1:1 ratio to conventional or triple-site CRT with defibrillator-cardioverter. After 12 months of resynchronization 30% of patients with conventional resynchronization and 12.5% with triple-site CRT were in NYHA functional class III or IV (P < 0.05). Implantation of triple-site systems was significantly longer (median 125 minutes vs 96 minutes; P < 0.001), with higher fluoroscopic exposure, especially in patients with very enlarged left ventricle or pulmonary hypertension. Implantation success-rate was similar in the triple-site and conventional group (94% vs 98%; P = NS); however, additional techniques had to be used in a greater proportion of the triple-site patients (33.3% vs 16%; P < 0.05). Long-term lead performance tests revealed significantly higher pacing threshold and lower impedance in the triple-site group. The 1-year incidence of serious, CRT-related adverse events was similar in triple-site and conventional group (20.8% vs 30%; P = NS).

CONCLUSIONS

Triple-site CRT is associated with more pronounced functional improvement than standard resynchronization. This form of pacing is equally safe and feasible as the conventional CRT. However, triple-site procedure is more time-consuming, associated with higher radiation exposure and the need to use additional techniques. Triple-site resynchronization is associated with less favorable electrical lead characteristics.

Alternate Site Pacing in Patients at Risk for Heart Failure

Cardiac pacing from the right ventricular apex is the most common site of cardiac pacing. During the last decade, several studies demonstrated the harmful effects of the iatrogenic left bundle branch block, which is observed in cardiac pacing from the right ven- tricular apex. These observations led to an interest in alternative right ventricular pacing sites aiming to achieve a more “physiological” pattern of ventricular activation. Alternate site pacing may involve His bun- dle, other right ventricular sites (outflow or septal sites), or left ventricular sites in either unifocal or bifo- cal or biventricular modes. Pacing from the right ven- tricular outflow tract has been studied extensively. Several studies showed that right ventricular outflow tract pacing has better hemodynamic effects and less harmful influence. Bifocal right ventricular (apical and outflow tract) pacing has been proposed for patients with heart failure where the coronary sinus approach to effect biventricular pacing turns out to be unsuccessful because of various reasons. Some studies examined left ventricular pacing alone as an alternative mode of pacing, and the results were quite encouraging but not conclusive. Finally, in heart failure patients not responding to biventricular pacing, the triple site pacing mode has been recently proposed. In triple site pacing, the leads are inserted in the right ventricular apex and outflow tract in conjunction with lateral left ventricular pacing. Improvement of exercise capacity and increased ejection fraction were observed with this triventricular pacing. Although more data from specifically designed randomized studies are needed, there are many alternative pacing sites, especially for patients at high risk of heart failure, which seems to be less harmful and better tolerated by the patients.