Mid-term follow up of thromboembolic complications in left ventricular endocardial cardiac resynchronization therapy

Beyond Conventional Cardiac Resynchronisation Therapy: A Review of Electrophysiological Options in the Management of Chronic Heart Failure

The incidence of heart failure (HF) continues to grow and burden our health care system. Electrophysiological aberrations are common amongst patients with heart failure and can contribute to worsening symptoms and prognosis. Targeting these abnormalities with cardiac and extra-cardiac device therapies and catheter ablation procedures augments cardiac function. Newer technologies aimed to improvement procedural outcomes, address known procedural limitations and target newer anatomical sites have been trialled recently. We review the role and evidence base for conventional cardiac resynchronisation therapy (CRT) and its optimisation, catheter ablation therapies for atrial arrhythmias, cardiac contractility and autonomic modulation therapies.

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.

Leadless left ventricular stimulation with WiSE-CRT System - Initial experience and results from phase I of SOLVE-CRT Study (nonrandomized, roll-in phase)

BACKGROUND

Left ventricular (LV) endocardial pacing is a promising method to deliver cardiac resynchronization therapy (CRT). WiSE-CRT is a wireless LV endocardial pacing system, and delivers ultrasonic energy to an LV electrode.

OBJECTIVE

The purpose of this study was to present short-term outcomes with the WiSE-CRT system in centers with no prior implanting experience.

METHODS

Data were prospectively collected from 19 centers where WiSE-CRT systems were implanted during the roll-in phase of the SOLVE-CRT trial. Patients were followed at 1, 3, and 6 months, including transthoracic echo (TTE) at 6 months.

RESULTS

The WiSE-CRT was successfully implanted in all 31 attempted cases, and 30 patients completed the 6-month follow-up. One patient underwent heart transplantation 1 month after implantation, and was excluded. Fourteen (46.7%) patients demonstrated ≥1 NYHA class improvement. TTE data were available in 29 patients. LV ejection fraction, LV end-systolic volume, and LV end-diastolic volume improved from 28.3% ± 6.7% to 33.5% ± 6.9% (P < .001), 134.9 ± 51.3 mL to 111.1 ± 40.3 mL (P = .0004), and 185.4 ± 58.8 mL to 164.9 ± 50.6 mL (P = .0017), respectively. There were 3 (9.7%) device-related type 1 complications: 1 insufficient LV pacing, 1 embolization of an unanchored LV electrode, and 1 skin infection.

CONCLUSIONS

We demonstrated a high success rate of LV endocardial electrode placement in centers with no prior implanting experience. Favorable clinical responses in heart failure symptoms and significant LV reverse remodeling were noted.

Three-dimensional echocardiography definitively delineates a malpositioned permanent pacing lead in a patient with chronic chest pain

Inadvertent malpositioning of a cardiac pacing lead into the left heart chambers is a rare complication of transvenous pacing. We report a patient with a history of a transient ischemic attack and chronic chest pain whose left atrial pacing lead location was revealed by transesophageal three-dimensional (3D) echocardiography during evaluation of an inter-atrial shunt.

Non-infective left ventricular lead complications requiring re-intervention following cardiac resynchronization therapy: prevalence, causes and outcomes

PURPOSE

Left ventricular (LV) lead complications in cardiac resynchronization therapy are challenging and poorly reported. We aimed to establish prevalence, causes and outcomes of LV lead complications requiring re-intervention.

METHODS

We analysed the rate of complications in 2551 consecutive patients who received a transvenous de novo LV lead as part of a cardiac resynchronization therapy device between 2000 and 2018. LV lead complications requiring re-intervention were identified; those due to infection were excluded. Patient, procedural and device characteristics, and outcomes were examined for non-infective LV lead complications requiring re-intervention.

RESULTS

During a median of 4.7 years, 142 (5.6%) patients required re-intervention for non-infective LV lead complications with a decrease from 10.7% between 2000 and 2004, 8.7% between 2005 and 2009, 3.2% between 2010 and 2014 to 3.2% after 2014. The most common complications were LV lead displacement (50%), high pacing threshold (28%) and phrenic nerve stimulation (15%). Of the complications, 79 (56%) occurred within 90 days post-implant and 63 (44%) later. At the end of the study period, 132/142 patients (93%) had a functional LV lead. Lead re-intervention was associated with higher risk of complications (20%), but no increase in mortality (P = 0.19). Quadripolar leads had longer longevity and lower risk of complications compared with unipolar and bipolar LV leads.

CONCLUSIONS

A small but significant proportion of patients required LV lead re-intervention for complications following de novo implant. Lead displacement accounted for half of the re-interventions. Re-intervention was associated with a higher complication rate, but 92% of these patients had functional LV leads at the end of follow-up.

Long-term single-centre large volume experience with transseptal endocardial left ventricular lead implantation

Aims

The aim of our study was to investigate the long-term efficacy and safety of transseptal endocardial left ventricular lead implantation (TELVLI).

Methods and results

Transseptal endocardial left ventricular lead implantation was performed in 54 patients (44 men, median age 69, New York Heart Association III–IV stage) between 2007 and 2017 in a single centre. In 36 cases, the transseptal puncture (TP) was performed via the femoral vein, and in 18 cases, the TP and also the left ventricular (LV) lead placement were performed via the subclavian vein. An electrophysiological deflectable catheter was used to reach the LV wall through the dilated TP hole. The LV lead implantation was successful in all patients. A total of 54 patients were followed up for a median of 29 months [interquartile range (IQR) 8–40 months], the maximum follow-up time was 94 months. Significant improvement in the LV ejection fraction was observed at the 3-month visit, from the median of 27% (IQR 25–34%) to 33% (IQR 32–44%), P < 0.05. Early lead dislocation was observed in three cases (5%), reposition was performed using the original puncture site in all. The patients were maintained on anticoagulation therapy with a target international normalized ratio between 2.5 and 3.5. Four thromboembolic events were noticed during follow-up. A total of 27 patients died, with a median survival of 15 months (IQR 6–40).

Conclusion

The TELVLI is an effective approach for cardiac resynchronization therapy (CRT) however it is associated with a substantial thromboembolic risk (7%).

Multicenter prospective observational long-term follow-up study of endocardial cardiac resynchronization therapy using the Jurdham procedure

BACKGROUND

Endocardial cardiac resynchronization therapy (eCRT) avoids the limitations and failures of coronary sinus (CS) resynchronization. However, data regarding long-term outcomes are lacking.

OBJECTIVE

The purpose of this study was to report the long-term outcome of eCRT performed using the Jurdham procedure in a real-world setting.

METHODS

eCRT was performed in patients who failed a CS implant or failed to respond to cardiac resynchronization therapy (CRT), or in selected patients requiring lifelong oral anticoagulation (OAC). Left ventricular ejection fraction (LVEF), New York Heart Association functional class (NYHA FC), and left ventricular stimulation parameters were assessed during long-term follow-up (FU).

RESULTS

From August 2009 to March 2018, the Jurdham procedure was performed in 88 patients at 15 centers in 8 countries, with FU of 32.88 ± 61.52 months (range 0-88 months; 196 patient-years). NYHA FC improved from 2.9 preimplant to 1.3 during FU. LVEF increased <10 percentage points from baseline in 7% of patients, between 10 and 20 percentage points in 11% of patients, and >20 percentage points in 82% of patients. All-cause mortality at 60 months was 30.5%. Three transient ischemic attacks (1.53 per 100 patient-years) and 6 strokes (3.06 per 100 patient-years) occurred. Of the 6 patients with stroke, 4 (66%) had almost complete recovery.

CONCLUSION

eCRT using the Jurdham procedure is an effective and safe technique in anticoagulated patients. This approach may be an attractive option for patients with failed CS implants or nonresponders to CS CRT. In addition, it might be a reasonable approach as a first option for treatment of patients requiring lifelong OAC.

Comparison between endocardial and epicardial cardiac resynchronization in an experimental model of non-ischaemic cardiomyopathy

Aims

Pacing from the left ventricular (LV) endocardium might increase the likelihood of response to cardiac resynchronization therapy. However, experimental and clinical data supporting this assumption are limited and controversial. The aim of this study was to compare the acute response of biventricular pacing from the LV epicardium and endocardium in a swine non-ischaemic cardiomyopathy (NICM) model of dyssynchrony.

Methods and results

A NICM was induced in six swine by 3 weeks of rapid ventricular pacing. Biventricular stimulation was performed from 16 paired locations in the LV (8 epicardial and 8 endocardial) with two different atrioventricular (80 and 110 ms) intervals and three interventricular (0, +30, -30 ms) delays. The acute response of the aortic blood flow, LV and right ventricular (RV) pressures, LVdP/dtmax and LVdP/dtmin and QRS complex width and QT duration induced by biventricular stimulation were analysed. The haemodynamic and electrical beneficial responses to either LV endocardial or epicardial biventricular pacing were similar (ΔLVdP/dtmax: +7.8 ± 2.2% ENDO vs. +7.3 ± 1.5% EPI, and ΔQRS width: -16.8 ± 1.3% ENDO vs. -17.1 ± 1.9% EPI; P = ns). Pacing from LV basal regions either from the epicardium or endocardium produced better haemodynamic responses as compared with mid or apical LV regions (P < 0.05). The LV regions producing the maximum QRS complex shortening did not correspond to those inducing the best haemodynamic responses (EPI: r2 = 0.013, P = ns; ENDO: r2 = 0.002, P = ns).

Conclusion

Endocardial LV pacing induced similar haemodynamic changes than pacing from the epicardium. The response to endocardial LV pacing is region dependent as observed in epicardial pacing.

Left Ventricular Endocardial Pacing/Leadless Pacing

Several clinical trials have established the role of cardiac resynchronization therapy in patients with heart failure, impaired left ventricular function and dyssynchrony. Challenges to traditional therapy include coronary sinus anatomy and failure to respond. Left ventricular endocardial pacing could overcome anatomic constraints, provide more flexibility, and allow for more physiologic activation. Cases and case series have demonstrated the promise of the approach. Preclinical studies support the superior hemodynamic effects of left ventricular endocardial pacing. Leadless left ventricular endocardial pacing is a recent innovation that is undergoing prospective testing. Successful delivery may be associated with clinical response and positive cardiac structural remodeling.

Left ventricular endocardial pacing in the real world: Five years of experience at a single center

BACKGROUND

A left ventricular (LV) endocardial lead implant to achieve cardiac resynchronization therapy (CRT) is feasible when a conventional implant failed due to anatomical or technical issues or when the venous implant was performed but the patient did not respond to the therapy.

METHODS

Data about the implantation procedure (age, sex, clinical characteristics, anticoagulant use, and previous devices), patient characteristics (indication, technique used, lead model, complications), and follow-up (clinical and echocardiographic outcome, LV lead electrical measurements) were analyzed for all CRT systems implanted using LV endocardial lead, due to failed conventional implant or nonresponse, between April 2011 and November 2016.

RESULTS

Thirty-five patients were implanted with an active fixation LV endocardial lead during the study period, without significant complications. There were no dislodgements or severe complications related to the implant procedure in the follow-up period (36 ± 20 months) and a high percentage of patients responded to therapy, as assessed by several indicators.

CONCLUSIONS

An LV endocardial lead implant was feasible when the conventional technique had previously failed or was not effective. A high rate of response was achieved without any significant complications.

Thrombo-embolic events in left ventricular endocardial pacing: long-term outcomes from a multicentre UK registry

Aims

Endocardial left ventricular (LV) pacing is a viable alternative in patients with failed coronary sinus (CS) lead implantation. However, long-term thrombo-embolic risk remains unknown. Much of the data have come from a small number of centres. We examined the safety and efficacy of endocardial LV pacing to determine the long-term thrombo-embolic risk.

Methods and results

Registries from four UK centres were combined to include 68 patients with endocardial leads with a mean follow-up of 20 months. These were compared to a matched 1:2 control group with conventional CS leads. Medical records were reviewed, and patients contacted for follow-up. Ischaemic stroke occurred in four patients (6%) in the endocardial arm providing an annual event rate (AER) of 3.6% over a 20 month follow-up; compared to 9 patients (6.6%) amongst controls with an AER of 3.4% over a 23-month follow-up. Regression analyses showed a significant association between sub-therapeutic international normalized ratio and stroke (P = 0.0001) in the endocardial arm. There was no association between lead material and mode of delivery (transatrial/transventricular) and stroke. Mortality rate was 12 and 15 per 100 patient years in the endocardial and control arm respectively with end-stage heart failure being the commonest cause.

Conclusion

Endocardial LV lead in heart failure patients has a good success rate at 1.6 year follow-up. However, it is associated with a thrombo-embolic risk (which is not different from conventional CS leads) attributable to sub-therapeutic anticoagulation. Randomized control trials and studies on non-vitamin K antagonist oral anticoagulants are required to ascertain the potential of widespread clinical application of this therapeutic modality.

[Leadless endocardial ultrasound based left ventricular stimulation : WISE CRT System: alternative to conventional methods]

There are still several limitations in delivering cardiac resynchronisation therapy (CRT). After 6 months, 20-40% of patients fail to have clinical benefit due to various reasons. Endocardial stimulation rather than conventional epicardial pacing has been shown to be more physiological, improves electrical stimulation of the left ventricle (LV), has less dispersion of electrical activity and results in better resynchronisation. The WiSE™ CRT System ("Wireless stimulation endocardial system"; EBR Systems, Sunnyvale, CA, USA) provides an option for wireless, LV endocardial pacing triggered by a conventional right ventricular pacing spike from a co-implant. The feasibility of the WiSE™ CRT System has been successfully demonstrated in a population of failed cardiac resynchronisation patients with either failed implantation of a conventional system, nonresponse to conventional therapy or upgrade from pacemaker or defibrillator, where a conventional system was not an option. The WiSE™ CRT System is an innovative technology with promising safety, performance and preliminary efficacy.

Systematic review and meta-analysis of left ventricular endocardial pacing in advanced heart failure: Clinically efficacious but at what cost?

INTRODUCTION

Cardiac resynchronization using a left ventricular (LV) epicardial lead placed in the coronary sinus is now routinely used in the management of heart failure patients. LV endocardial pacing is an alternative when this is not feasible, with outcomes data sparse.

OBJECTIVE

To review the available evidence on the efficacy and safety of endocardial LV pacing via meta-analysis.

METHODS

EMBASE, MEDLINE, and COCHRANE databases with the search term "endocardial biventricular pacing" or "endocardial cardiac resynchronization" or "left ventricular endocardial" or "endocardial left ventricular." Comparisons of pre-and post-QRS width, LV ejection fraction (LVEF), and New York Heart Association (NYHA) functional classification was performed, and mean differences (and respective 95% confidence interval [CI]) applied as a measurement of treatment effect.

RESULTS

Fifteen studies, including 362 patients, were selected. During a mean follow-up of 40 ± 24.5 months, death occurred in 72 patients (11 per 100 patient-years). Significant improvements in LVEF (mean difference 7.9%, 95% CI 5-10%, P < 0.0001; I²  = 73%), QRS width (mean difference: -41% 95% -75 to -7%; P < 0.0001; I²  = 94%), and NYHA class (mean difference: -1.06, 95% CI -1.2 to -0.9, P < 0.0001; I²  = 60%), (all P < 0.0001) occurred. Stroke rate was 3.3-4.2 per 100 patient-years, which is higher than equivalent heart failure trial populations and recent meta-analysis that included small case series.

CONCLUSION

LV endocardial lead implantation is a potentially efficacious alternative to CS lead placement, but preliminary data suggest a potentially higher risk of stroke during follow-up when compared to the expected incidence of stroke in similar cohorts of patients.

Up-to-date cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) has been first reported more than 10 years ago as a therapy for patients with severe chronic heart failure. The efficacy of CRT has been proven in many studies that it improves not only quality of life but also the prognosis of the patients. Its indication has been expanded for patients with mild heart failure. On the other hand, some patients cannot receive enough benefit through CRT. The position of the left ventricular lead is limited due to the anatomy of coronary sinus branches, pacing threshold of the myocardium, phrenic nerve stimulation, and so on. Also, the right selection of the candidates for CRT is critical to receive the most benefit of this therapy. The target of this review article is to describe the efficacy and the indication of CRT, which can be of any help to enroll more patients with heart failure who are likely to get benefits through CRT.

Exploring the Electrophysiologic and Hemodynamic Effects of Cardiac Resynchronization Therapy: From Bench to Bedside and Vice Versa

Cardiac resynchronization therapy (CRT) is an important therapy for heart failure patients with prolonged QRS duration. In patients with left bundle branch block the altered left ventricular electrical activation results in dyssynchronous, inefficient contraction of the left ventricle. CRT aims to reverse these changes and to improve cardiac function. This article explores the electrophysiologic and hemodynamic changes that occur during CRT in patient and animal studies. It also addresses how novel techniques, such as multipoint and endocardial pacing, can further improve the electromechanical response.

Long-term cerebral thromboembolic complications of transapical endocardial resynchronization therapy

Purpose

Cardiac resynchronization therapy (CRT) is an established therapeutic option in selected heart failure patients (pts). However, the transvenous left ventricular (LV) lead implantation remains ineffectual in a considerable number of pts. Transapical LV (TALV) lead implantation is an alternative minimally invasive, surgical, endocardial implantation technique. The aim of the present prospective study is to determine the long-term outcome, including the cerebral thromboembolic complications, of pts who underwent TALV lead placement.

Methods

Twenty-six CRT candidates (19 men (78 %); mean age 61 ± 10 years) with a previously failed transvenous approach underwent TALV lead placement as a last resort therapy. The following data was collected: mortality rate, reoperation rate, and cerebrovascular event rate. Patients underwent a cerebral CT scan to determine any possible cerebrovascular event related to the presence of the TALV lead.

Results

Eleven out of 26 (47 %) patients survived after a median follow-up of 40 ± 24.5 months. Major acute ischemic stroke occurred in two cases, while in one case transient ischemic stroke was observed. Cerebral CT scan examination performed in asymptomatic patients revealed chronic ischemic lesions with minimal extension in two patients. Reoperation occurred in one case due to TALV lead fracture.

Conclusions

This is the first study reporting the long-term outcome, mortality, and thromboembolic event rate exclusively after TALV lead implantation. Patients who underwent TALV lead implantation have a comparable long-term mortality rate to conventional CRT, although a major ischemic cerebrovascular event after TALV lead implantation is worrisome and has an impact on the outcome.

Alternative to left ventricular lead implantation through the coronary sinus: 1-year experience with a minimally invasive and robotically guided approach

AIMS

Left ventricular (LV) lead implantation through the coronary sinus (CS) can be limited and sometimes not possible-alternative approaches are needed. Minimally invasive, robotically guided LV lead implantation has major advantages, but there are little published data about the short- and long-term follow-ups, in terms of feasibility, safety, electrical performance, and impact on clinical outcome.

METHODS AND RESULTS

A total of 21 heart failure patients underwent robotically guided LV lead implantation using the Da Vinci Robotic System. Indications were failed implant with conventional approach through the CS (n = 16) and non-response to conventional cardiac resynchronization therapy (n = 5). During the procedure, the entire LV free wall was exposed through 3 transthoracic ports (10 mm diameter each) allowing ample choice of stimulation site and the ability to implant 2 LV leads via a Y connector. Patients were prospectively followed up for 1 year. The two LV leads were successfully implanted in all patients. No peri-procedural complications were observed. After a mean stay in the intensive care unit of 1.2 ± 4 days, the 21 patients were hospitalized in the EP department for 6.7 ± 2.9 days. Acute LV thresholds were excellent (1.0 V ± 0.6/0.4 ms) and stayed stable at 1-year follow-up (1.5 V ± 0.6/0.4 ms, P = 0.21). Four patients demonstrated an increased threshold (>2 V/0.4 ms). There was no phrenic nerve stimulation. After 12 months, in the failed implant group, 69% of the patients were echocardiographic and clinical responders.

CONCLUSION

The robotic approach was feasible, safe, and minimally invasive. Accordingly, robotically guided LV lead implantation seems to offer a new alternative when conventional approaches are not suitable.

Haemodynamic evaluation of alternative left ventricular endocardial pacing sites in clinical non-responders to cardiac resynchronisation therapy

Introduction

Non response to cardiac resynchronisation therapy (CRT) may be related to the position of the coronary sinus lead.

Methods

We studied the acute haemodynamic response (AHR) from alternative left ventricular (LV) endocardial pacing sites in clinical non-responders to CRT. AHR and the interval from QRS onset to LV sensing (Q-LV interval) from four different endocardial pacing sites were evaluated in 24 clinical non-responders. A rise in LVdP/dtmax ≥ 15 % from baseline was considered a positive AHR. We also compared the AHR from endocardial with the corresponding epicardial lead position.

Results

The implanted system showed an AHR ≥ 15 % in 5 patients. In 9 of the 19 remaining patients, AHR could be elevated to ≥ 15 % by endocardial LV pacing. The optimal endocardial pacing site was posterolateral. There was no significant difference in AHR between the epicardial and the corresponding endocardial position. The longest Q-LV interval corresponded with the best AHR in 12 out of the 14 patients with a positive AHR, with an average Q-LV/QRS width ratio of 90 %.

Conclusions

Acute haemodynamic testing may indicate an alternative endocardial pacing site with a positive AHR in clinical non-responders. The Q-LV interval is a strongly correlated with the optimal endocardial pacing site. Endocardial pacing opposite epicardial sites does not result in a better AHR.

Exploring the Electrophysiologic and Hemodynamic Effects of Cardiac Resynchronization Therapy: From Bench to Bedside and Vice Versa

Cardiac resynchronization therapy (CRT) is an important therapy for heart failure patients with prolonged QRS duration. In patients with left bundle branch block the altered left ventricular electrical activation results in dyssynchronous, inefficient contraction of the left ventricle. CRT aims to reverse these changes and to improve cardiac function. This article explores the electrophysiologic and hemodynamic changes that occur during CRT in patient and animal studies. It also addresses how novel techniques, such as multipoint and endocardial pacing, can further improve the electromechanical response.

Pacing site in pacemaker dependency: is right ventricular septal lead position the answer?

The right ventricular apex has been the traditional site for lead placement in patients with atrioventricular block. Pacing at the right ventricular apex may have long-term deleterious effects on left ventricular (LV) function, promoting heart failure and increasing mortality. Pacing at the right ventricular septum has been proposed to minimize deterioration in LV function. Although experimental data suggest that septal pacing protects LV function, clinical studies have provided conflicting results. A recent large study in patients with heart block did not show a protective effect with septal pacing. Other pacing approaches are becoming increasingly relevant; however, prediction of what method should be employed in which patient is not currently possible. Other factors such as baseline LV function and associated co-morbidities impact LV function, irrespective of pacing site. Continued monitoring of cardiac function post-implant is therefore critical to ongoing care. An algorithm for managing patients with atrioventricular block is proposed.

Cardiac resynchronization therapy update: evolving indications, expanding benefit?

Cardiac resynchronisation therapy (CRT) is an effective intervention for appropriately selected patients with heart failure, but exactly how it works is uncertain. Recent data suggest that much, or perhaps most, of the benefits of CRT are not delivered by re-coordinating left ventricular dyssynchrony. Atrio-ventricular resynchronization, reduction in mitral regurgitation and prevention of bradycardia are other potential mechanisms of benefit that will vary from one patient to the next and over time. Because there is no single therapeutic target, it is unlikely that any single measure will accurately predict benefit. The only clinical characteristic that appears to be a useful predictor of the benefits of CRT is a QRS duration of >140 ms. Many new approaches are being developed to try to improve the effectiveness of and extend the indications for CRT. These include smart pacing algorithms, better pacing-site targeting, new sensors, multipoint pacing, remote device monitoring and leadless endocardial pacing. Whether CRT is effective in patients with atrial fibrillation or whether adding a defibrillator function to CRT improves prognosis awaits further evidence.

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.

ECG Patterns In Cardiac Resynchronization Therapy

Cardiac resynchronization therapy is an established treatment modality in heart failure. Though non-response is a serious issue. To address this issue, a good understanding of the electrical activation during underlying intrinsic ventricular activation, biventricular as well as right- and left ventricular pacing is needed. By interpreting the 12-lead electrocardiogram, possible reasons for suboptimal treatment can be identified and addressed. This article reviews the literature on QRS morphology in cardiac resynchronization therapy and its role in optimization of therapy.

Strategies to improve cardiac resynchronization therapy

Cardiac resynchronization therapy (CRT) emerged 2 decades ago as a useful form of device therapy for heart failure associated with abnormal ventricular conduction, indicated by a wide QRS complex. In this Review, we present insights into how to achieve the greatest benefits with this pacemaker therapy. Outcomes from CRT can be improved by appropriate patient selection, careful positioning of right and left ventricular pacing electrodes, and optimal timing of electrode stimulation. Left bundle branch block (LBBB), which can be detected on an electrocardiogram, is the predominant substrate for CRT, and patients with this conduction abnormality yield the most benefit. However, other features, such as QRS morphology, mechanical dyssynchrony, myocardial scarring, and the aetiology of heart failure, might also determine the benefit of CRT. No single left ventricular pacing site suits all patients, but a late-activated site, during either the intrinsic LBBB rhythm or right ventricular pacing, should be selected. Positioning the lead inside a scarred region substantially impairs outcomes. Optimization of stimulation intervals improves cardiac pump function in the short term, but CRT procedures must become easier and more reliable, perhaps with the use of electrocardiographic measures, to improve long-term outcomes.