Long-term survival in patients undergoing cardiac resynchronization therapy: the importance of performing atrio-ventricular junction ablation in patients with permanent atrial fibrillation

Cardiac resynchronization therapy in patients with atrial fibrillation: a meta-analysis

BACKGROUND AND OBJECTIVE

To combine the results of the best scientific evidence in order to compare the effects of cardiac resynchronization therapy (CRT) in heart failure patients with atrial fibrillation (AF) and in sinus rhythm (SR) and to determine the effect of atrioventricular nodal ablation in AF patients.

METHODS

The electronic databases PubMed, B-On and Cochrane CENTRAL were searched, and manual searches were performed, for randomized controlled trials and cohort studies up to November 2012. The endpoints analyzed were all-cause and cardiovascular mortality and response to CRT.

RESULTS

We included 19 studies involving 5324 patients: 1399 in AF and 3925 in SR. All-cause mortality was more likely in patients with AF compared to patients in SR (OR = 1.69; 95% CI: 1.20–2.37; p = 0.002). There were no statistically significant differences in cardiovascular mortality (OR = 1.36; 95% CI: 0.92–2.01; p = 0.12). AF was associated with an increased likelihood of lack of response to CRT (OR = 1.41; 95% CI: 1.15–1.73; p = 0.001). Among subjects with AF, ablation of the atrioventricular node was associated with a reduction in all-cause mortality (OR = 0.42; 95% CI: 0.22–0.80; p = 0.008), cardiovascular death (OR = 0.39; 95% CI: 0.20–0.75; p = 0.005) and the number of non-responders to CRT (OR = 0.30; 95% CI: 0.10–0.90; p = 0.03).

CONCLUSIONS

The presence of AF is associated with increased likelihood of all-cause death and non-response to CRT, compared to patients in SR. However, many patients with AF benefit from CRT. Atrioventricular nodal ablation appears to increase the benefits of CRT in patients with AF.

Rate control in atrial fibrillation

Control of the heart rate (rate control) is central to atrial fibrillation management, even for patients who ultimately require control of the rhythm. We review heart rate control in patients with atrial fibrillation, including the rationale for the intervention, patient selection, and the treatments available. The choice of rate control depends on the symptoms and clinical characteristics of the patient, but for all patients with atrial fibrillation, rate control is part of the management. Choice of drugs is patient-dependent. β blockers, alone or in combination with digoxin, or non-dihydropyridine calcium-channel blockers (not in heart failure) effectively lower the heart rate. Digoxin is least effective, but a reasonable choice for physically inactive patients aged 80 years or older, in whom other treatments are ineffective or are contraindicated, and as an additional drug to other rate-controlling drugs, especially in heart failure when instituted cautiously. Atrioventricular node ablation with pacemaker insertion for rate control should be used as an approach of last resort but is also an option early in the management of patients with atrial fibrillation treated with cardiac resynchronisation therapy. However, catheter ablation of atrial fibrillation should be considered before atrioventricular node ablation. Although rate control is a top priority and one of the first management issues for all patients with atrial fibrillation, many issues remain.

Mortality After Atrioventricular Nodal Radiofrequency Catheter Ablation With Permanent Ventricular Pacing in Atrial Fibrillation

Background—

Atrioventricular nodal radiofrequency ablation (AVNA) with permanent ventricular pacing can be used to control rate in patients with atrial fibrillation (AF). However, long-term outcomes after AVNA are uncertain, especially in light of irreversible pacemaker dependence.

Methods and Results—

We examined 9122 consecutive patients with AF. The outcomes in 453 patients with AVNA (26% of whom underwent an implantable cardiac defibrillator implant and 37% underwent cardiac resynchronization therapy implant) were compared with AF patients without AVNA after propensity score 1:1 matching. During follow-up in the propensity-matched cohort (2.41±3.23 years, median 1.23, quartiles 0.33–3.12), 100 patients died (yearly rate of death 6.6%). Mode of death was available in 86% of patients, which was cardiovascular in 67% of the patients (related to heart failure in 38%, sudden death in 5%, and other cardiovascular reason in 24%) and noncardiovascular in 33%. AVNA in patients with AF was associated with a lower risk of mortality (odds ratio 0.47, 95% confidence interval, 0.29–0.77; P =0.003), a lower risk of cardiovascular mortality (odds ratio =0.41, 95% confidence interval 0.23–0.73; P =0.003), and nonsignificant lower risk of stroke and thromboembolic events (odds ratio =0.61, 95% confidence interval 0.36–1.06; P =0.08).

Conclusions—

In sick AF patients with multiple comorbidities, AVNA with permanent ventricular pacing for rate control seems safe during follow-up and may be associated with lower mortality.

Cardiac Resynchronization in Patients with Atrial Fibrillation

Atrial fibrillation (AF) occurs in one of four patients undergoing cardiac resynchronization therapy (CRT).-Without special therapy, the prognosis of AF patients with CRT has been generally worse than those in sinus rhythm. The importance of a high percentage of biventricular pacing (BIV%) was confirmed in a large study where the mortality was inversely associated with BIV% both in the presence of normal sinus and atrial paced rhythm and with AF. The greatest reduction in mortality was observed with BIV% >98%. Patients with BIV% >99.6% experienced a 24% reduction in mortality (p < 0.001) while those with BIV% <94.8% had a 19% increase in mortality. The optimal BIV% cut-point was 98.7%. This cutoff would appear mandatory but it would be best to approach 100%. Careful evaluation of device interrogation data upon which the BiV% is based is essential because the memorized data can vastly overestimate the percentage of truly resynchronized beats since it does not account for fusion and pseudofusion between intrinsic (not paced) and paced beats. The recently published randomized CERTIFY trial provides unequivocal proof of the value of AV junctional (AVJ) ablation in CRT patients with AF. This trial confirmed the favorable results of AVJ ablation by many other studies and two important meta-analyses and therefore established the firm recommendation that the procedure should be performed in most, if not all, patients with permanent AF as well as those with frequent and prolonged episodes of paroxysmal AF. Patients after AVJ have improved mortality with a mortality similar to those in sinus rhythm. The AVJ ablation procedure carries the theoretical risk of device failure and death in pacemaker dependent patients. An inappropriate first ICD shock for AF seems to increase mortality. Increased long-term mortality after an inappropriate shock may be due to the underlying atrial arrhythmia substrate as opposed to the effect of the shock itself.

[Device therapy of chronic heart failure: Update 2015]

Cardiac pacemakers, implantable cardioverter defibrillators (ICD) and systems for cardiac resynchronization therapy (CRT) represent an important component of heart failure therapy. Pacemakers only play a role in bradycardia-associated heart failure and require optimal programming to prevent ventricular desynchronization. Primary prophylactic ICD implantation is indicated in patients with a left ventricular ejection fraction of ≤ 35 %, clinical stages NYHA II-III and a life expectancy > 1 year. The CRT is indicated in patients with a left bundle branch block but only in individual cases for other QRS morphologies of < 150 ms duration. The combination of CRT with a pacemaker or defibrillator must be decided on an individual basis. Device therapy in heart failure should always include remote monitoring to detect events early and to implement treatment accordingly. New developments include quadripolar left ventricular leads and pacing from multiple sites simultaneously thus enabling better resynchronization. Stimulation for modulation of cardiac contractility and the autonomous nervous system are currently being clinically tested. The optimal utilization of device therapy improves the course of heart failure and prevents cardiac decompensation and fatalities.

Atrial Fibrillation During Cardiac Resynchronization Therapy

The landmark trials on cardiac resynchronization therapy (CRT) have focused on patients with sinus rhythm at inclusion. Little data are available on the efficacy of CRT in patients with atrial fibrillation (AF), while AF has a high prevalence (20-40%) among patients receiving CRT. This review focuses on the detrimental effect of AF on CRT response and discusses management of patients with AF during CRT. Uncertainty remains as to which thresholds of AF burden can lead to a reduced response to CRT and every effort should be made in trying to assess and guarantee successful biventricular pacing in patients with AF.

Cardiac Resynchronization Therapy: How to Decrease Nonresponders

Nonresponse to cardiac resynchronization therapy (CRT) is still a major issue in therapy expansion. The description of fast, simple, cost-effective methods to optimize CRT could help in adapting pacing intervals to individual patients. A better understanding of the importance of appropriate patient selection, left ventricular lead placement, and device programming, together with a multidisciplinary approach and an optimal follow-up of the patients, may reduce the percentage of nonresponders.

Impact of Tricuspid Regurgitation on the Success of Atrioventricular Node Ablation for Rate Control in Patients With Atrial Fibrillation: The Node Blast Study

Atrioventricular node (AVN) ablation is an effective treatment for symptomatic patients with atrial arrhythmias who are refractory to rhythm and rate control strategies where optimal ventricular rate control is desired. There are limited data on the predictors of failure of AVN ablation. Our objective was to identify the predictors of failure of AVN ablation. This is an observational single-center study of consecutive patients who underwent AVN ablation in a large academic center. Baseline characteristics, procedural variables, and outcomes of AVN ablation were collected. AVN "ablation failure" was defined as resumption of AVN conduction resulting in recurrence of either rapid ventricular response or suboptimal biventricular pacing. A total of 247 patients drug refractory AF who underwent AVN ablation at our center with a mean age of 71 ± 12 years with 46% being males were included. Ablation failure was seen in 11 (4.5%) patients. There were no statistical differences between patients with "ablation failure" versus "ablation success" in any of the baseline clinical variables. Patients with moderate-to-severe tricuspid regurgitation (TR) were much more likely to have ablation failure than those with ablation success (8 [73%] vs 65 [27%]; p = 0.003). All 11 patients with ablation failure had a successful redo procedure, 9 with right and 2 with the left sided approach. On multivariate analysis, presence of moderate-to-severe TR was found to be the only predictor of failure of AVN ablation (odds ratio 9.1, confidence interval 1.99 to 42.22, p = 0.004). In conclusion, moderate-to-severe TR is a strong and independent predictor of failure of AVN ablation.

Atrioventricular Node Ablation

Cardiac resynchronization therapy (CRT) is a device-based, nonpharmacologic approach that has shown to improve the outcome in patients with heart failure in terms of mortality and morbidity reduction. Large randomized trials have virtually enrolled patients in New York Heart Association class III-IV, with reduced left ventricular ejection fraction, with evidence of electrical dyssynchrony, and receiving optimal medical therapy and who were in sinus rhythm. Guidelines remain imprecise as to defining differentiated approaches according to the forms of atrial fibrillation other than permanent. These recommendations remain unsupported by evidence derived from randomized controlled trials, which are much needed.

A review on atrioventricular junction ablation and pacing for heart rate control of atrial fibrillation

Atrioventricular junction ablation with permanent pacemaker implantation is a highly effective treatment approach in patients with atrial fibrillation and high ventricular rates resistant to other treatment modalities, especially in the elderly or those with severe comorbidities. Compared with pharmacological therapy alone, the so-called "ablate and pace" approach offers the potential for more robust control of ventricular rate. Atrioventricular junction ablation and pacing strategy is associated with improvement in symptoms, quality of life, and exercise capacity. Given the close relationship between atrial fibrillation and heart failure, there is a particular benefit of such a rate control in patients with atrial fibrillation and reduced systolic function. There is increasing evidence that cardiac resynchronization therapy devices may be beneficial in selected populations after atrioventricular junction ablation. The present review article focuses on the current recommendations for atrioventricular junction ablation and pacing for heart rate control in patients with atrial fibrillation. The technique, the optimal implantation time, and the proper device selection after atrioventricular junction ablation are also discussed.

Atrioventricular Junction Ablation In Atrial Fibrillation: Choosing The Right Patient And Pacing Device

Atrial fibrillation (AF) is the most common cardiac arrhythmia and despite advancements in rhythm control through direct catheter ablation, maintaining sinus rhythm is not possible in a large proportion of AF patients, who therefore are subject to a rate control strategy only. Nonetheless, in some of these patients pharmacological rate control may be ineffective, often leaving the patient highly symptomatic and at risk of developing tachycardia-induced cardiomyopathy and heart failure (HF). Catheter ablation of the atrioventricular junction (AVJ) with subsequent permanent pacemaker implantation provides definite rate control and represents an attractive therapeutic option when pharmacological rate control is not achieved. In patients with reduced ventricular function, cardiac resynchronization therapy (CRT) should be considered over right ventricular apical (RVA) pacing in order to avoid the deleterious effects associated with a high amount of chronic RVA pacing. Another group of patients that may also benefit from AVJ ablation are HF patients with concomitant AF receiving CRT. In this patient cohort AVJ ablation ensures near 100% biventricular pacing, thus allowing optimization of the therapeutic effects of CRT.

Device therapy for acute systolic heart failure and atrial fibrillation

Patients with newly diagnosed cardiomyopathy require careful assessment of cause and initiation of treatment before the decision is made to implant an internal cardiac defibrillator. In patients with medicine-refractory atrial fibrillation and cardiomyopathy, atrioventricular node ablation and implantation of a biventricular pacemaker is the therapy of choice when tachycardia-induced cardiomyopathy is suspected and curative therapy is not possible.

Validation of a simple risk stratification tool for patients implanted with Cardiac Resynchronization Therapy: the VALID-CRT risk score

AIMS

Mortality after cardiac resynchronization therapy (CRT) is difficult to predict. We sought to design and validate a simple prognostic score for patients implanted with CRT, based on readily available clinical variables, including age, gender, left ventricular ejection fraction (LVEF), New York Heart Association (NYHA) class, presence/absence of atrial fibrillation, presence/absence of atrioventricular junction ablation, coronary heart disease, diabetes, and implantation of a CRT device with defibrillation.

METHODS

For predictive modelling, 5153 consecutive patients enrolled in 72 European centres (79% male; LVEF 25.9 ± 6.85%; NYHA class III-IV 77.5%; QRS 158.4 ± 32.3 ms) were randomly split into derivation (70%) and validation (30%) samples. The primary endpoint was total mortality and the secondary endpoint was cardiovascular mortality. The final predictive model fit was assessed by plotting observed vs. predicted survival.

RESULTS

In the entire cohort, 1004 deaths occurred over a follow-up of 14 409 person years. Total mortality ranged from 3.1% to 28.2% at 2 years in the first and fifth quintile of the risk score, respectively. At 5 years, total mortality was 10.3%, 18.6%, 27.6%, 36.1%, and 58.8%, from the first to the fifth quintile. Compared with the lowest quintile (Q), total mortality was significantly higher in the other four quintiles [Q2 hazard ratio (HR) = 1.71; Q3 HR = 2.20; Q4 HR = 4.03; Q5 HR = 8.03; all P < 0.001). The final model, which was based on the entire cohort using the above variables, showed a good discrimination (Harrell's c = 0.70) and high explained variation (0.26). The mean predicted survival fitted well with the observed survival for up to 6 years of follow-up.

CONCLUSIONS

The VALID-CRT risk score, which is based on routine, readily available clinical variables, reliably predicted the long-term total and cardiovascular mortality in patients undergoing CRT. While this score cannot be used to predict the benefit of CRT, it may be useful for predicting survival after CRT. This may have useful implications for follow-up.

Update on Cardiac Resynchronisation Therapy for Heart Failure

Cardiac resynchronisation therapy (CRT) is well accepted therapy for the treatment of symptomatic systolic heart failure in defined patient subgroups. Large clinical trials over the past 20 years have shown that patients with a left ventricular (LV) systolic dysfunction and interventricular conduction delay benefit from this therapy. Recent advances in this field include the expansion indications for CRT to patients with mild heart failure and to those with a mildly depressed ejection fraction that require frequent right ventricular pacing. In addition, although CRT guidelines have included indications in atrial fibrillation, it is now clear that this is most effective when pacing is utilised nearly 100 % of the time, often requiring atrioventricular (AV) junction ablation. Strategies for optimising LV lead placement based on identifying late mechanical contraction or electrical delay are promising for maximising CRT response. Finally, the role of routine AV delay optimisation is no longer recommended based on the results of multicentre trials.

Comparison of the rhythm control treatment strategy versus the rate control strategy in patients with permanent or long-standing persistent atrial fibrillation and heart failure treated with cardiac resynchronization therapy - a pilot study of Cardiac Resynchronization in Atrial Fibrillation Trial (Pilot-CRAfT): study protocol for a randomized controlled trial

BACKGROUND

The only subgroups of patients with heart failure and atrial fibrillation in which the efficacy of cardiac resynchronization therapy has been scientifically proven are patients with indications for right ventricular pacing and patients after atrioventricular junction ablation. However it is unlikely that atrioventricular junction ablation would be a standard procedure in the majority of the heart failure patients with cardiac resynchronization therapy and concomitant atrial fibrillation due to the irreversible character of the procedure and a spontaneous sinus rhythm resumption that occurs in about 10% of these patients.

METHODS/DESIGN

Pilot-CRAfT is the first randomized controlled trial evaluating the efficacy of a rhythm control strategy in atrial fibrillation patients with cardiac resynchronization therapy devices. The aim of this prospective, single center randomized controlled pilot study is to answer the question whether the patients with cardiac resynchronization therapy and permanent atrial fibrillation would benefit from a strategy to restore and maintain sinus rhythm (that is 'rhythm control' strategy) in comparison to rate control strategy. The study population consists of 60 patients with heart failure and concomitant long-standing persistent or permanent atrial fibrillation who underwent a cardiac resynchronization therapy device implantation at least 3 months before qualification. Study participants are randomly assigned to the rhythm control strategy (including electrical cardioversion and pharmacotherapy) or to the rate control group whose goal is to control ventricular rate. The follow-up time is 12 months. The primary endpoint is the ratio of effectively captured biventricular beats. The secondary endpoints include peak oxygen consumption, six-minute walk test distance, heart failure symptom escalation, reverse remodelling of the heart on echo and quality of life.

TRIAL REGISTRATION

NCT01850277 registered on 22 April 2013 (ClinicalTrials.gov).

Positive response to cardiac resynchronization therapy reduces arrhythmic events after elective generator change in patients with primary prevention CRT-D

INTRODUCTION

Cardiac resynchronization therapy (CRT) and implantable cardioverter-defibrillators (ICD) are effective therapies for heart failure (HF) patients with cardiac dyssynchrony. Patients receiving primary prevention CRT-defibrillator that positively remodel might no longer qualify for ICD indication due to CRT-induced left ventricular ejection fraction (LVEF) improvement. We aimed to evaluate the outcome of CRT-D patients at the time of device replacement (DR).

METHODS AND RESULTS

Patients undergoing primary prevention CRT-D DR were prospectively included from November 2007 to March 2011 in 2 centers. CRT response was as defined as ≥1 NYHA class improvement and an increase in LVEF ≥10%. Before DR, all patients underwent echocardiography and device interrogation. Patients without theoretical ongoing ICD indication (TOII) at DR were defined as those with LVEF ≥40% without appropriate ICD therapy (appropriate therapy) during the first ICD service-life. A total of 107 consecutive patients were enrolled. Sixty-one patients (57%) were considered CRT responders after the index procedure. At the time of DR (56.4 ± 14.4 months from initial implant), 87% of CRT responders were free of appropriate therapy, compared with 70% of CRT nonresponders (P = 0.02). Thirty-nine patients (37%) did not meet the criteria for TOII. During follow-up (mean 26.4 ± 14.4 months after DR), 37 patients (95%) without TOII were free of appropriate therapy versus 49 of 68 patients (72%) with ongoing TOII (P = 0.007). By multivariable analysis, the only independent predictor of appropriate therapy after DR was TOII (hazard ratio = 6.43; P = 0.01).

CONCLUSION

Absence of theoretical ICD indication occurs in more than one-third of CRT-D patients undergoing DR. In addition, appropriate therapy rate is relatively low (2.2% per year) in this subgroup of patients.

Effects of atrioventricular nodal ablation on permanent atrial fibrillation patients with cardiac resynchronization therapy: a systematic review and meta-analysis

Cardiac resynchronization therapy (CRT) is a well-established therapy for patients with heart failure (HF) and wide QRS configuration, especially for those in sinus rhythm. However, for those with permanent AF, atrioventricular nodal (AVN) ablation use remains under debate. Our objective was to evaluate clinical outcomes and mortality of AVN ablation in HF patients with permanent AF receiving CRT. Electronic publication database and reference lists through October 1, 2013 were searched. Observational cohort studies comparing CRT patients with AF who received either AVN ablation or medical therapy were selected. Outcomes included mortality, CRT nonresponse, changes in left ventricular remodeling, and functional outcomes, such as New York Heart Association (NYHA) functional class, quality of life, and 6-minute hall walk distance. Of 1641 reports identified, 13 studies with 1256 patients were included. Among patients with permanent AF and insufficient biventricular pacing (< 90%), those who had undergone AVN ablation compared to those who did not had numerically lower all-cause mortality (risk ratio [RR]: 0.63, 95% confidence interval [CI]: 0.42 to 0.96, P = 0.03) and significantly lower nonresponse to CRT (RR: 0.41, 95% CI: 0.31 to 0.54, P < 0.00001). Furthermore, AVN ablation was not associated with additional improvements on left ventricular ejection fraction, NYHA functional class, 6-minute hall walking distance, and quality of life. In patients with permanent AF undergoing CRT, AVN ablation tended to reduce mortality potentially and improved clinical response when it was applied to patients with inadequate biventricular pacing (< 90%). Randomized controlled trials are needed to further address the efficacy of AVN ablation among this population.

Implant-based multiparameter telemonitoring of patients with heart failure (IN-TIME): a randomised controlled trial

BACKGROUND

An increasing number of patients with heart failure receive implantable cardioverter-defibrillators (ICDs) or cardiac resynchronisation defibrillators (CRT-Ds) with telemonitoring function. Early detection of worsening heart failure, or upstream factors predisposing to worsening heart failure, by implant-based telemonitoring might enable pre-emptive intervention and improve outcomes, but the evidence is weak. We investigated this possibility in IN-TIME, a clinical trial.

METHODS

We did this randomised, controlled trial at 36 tertiary clinical centres and hospitals in Australia, Europe, and Israel. We enrolled patients with chronic heart failure, NYHA class II-III symptoms, ejection fraction of no more than 35%, optimal drug treatment, no permanent atrial fibrillation, and a recent dual-chamber ICD or CRT-D implantation. After a 1 month run-in phase, patients were randomly assigned (1:1) to either automatic, daily, implant-based, multiparameter telemonitoring in addition to standard care or standard care without telemonitoring. Investigators were not masked to treatment allocation. Patients were masked to allocation unless they were contacted because of telemonitoring findings. Follow-up was 1 year. The primary outcome measure was a composite clinical score combining all-cause death, overnight hospital admission for heart failure, change in NYHA class, and change in patient global self-assessment, for the intention-to-treat population. The trial is registered with ClinicalTrials.gov, number NCT00538356.

FINDINGS

We enrolled 716 patients, of whom 664 were randomly assigned (333 to telemonitoring, 331 to control). Mean age was 65·5 years and mean ejection fraction was 26%. 285 (43%) of patients had NYHA functional class II and 378 (57%) had NYHA class III. Most patients received CRT-Ds (390; 58·7%). At 1 year, 63 (18·9%) of 333 patients in the telemonitoring group versus 90 (27·2%) of 331 in the control group (p=0·013) had worsened composite score (odds ratio 0·63, 95% CI 0·43-0·90). Ten versus 27 patients died during follow-up.

INTERPRETATION

Automatic, daily, implant-based, multiparameter telemonitoring can significantly improve clinical outcomes for patients with heart failure. Such telemonitoring is feasible and should be used in clinical practice.

FUNDING

Biotronik SE & Co. KG.

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.

Use of Cardiac Resynchronisation Therapy - Change of Clinical Settings

Current guidelines recommend cardiac resynchronisation therapy (CRT) for patients with severe left ventricular dysfunction (left ventricular ejection fraction [LVEF] ≤35 %), QRS duration of ≥120-150 ms (Class IA and IB indications) on surface electrocardiogram (ECG) and New York Heart Association (NYHA) class III or IV heart failure (HF) symptoms. Ongoing studies aim to expand the use of CRT in patients with asymptomatic or minimal symptoms left ventricular dysfunction. There have been studies that have shown benefit of CRT extended to this group of patients. There have also been different implications of the role of CRT in patients with atrial fibrillation (AF), patients with narrow QRS duration or with right bundle branch block (RBBB) on surface ECG, as well as patients with end-stage renal failure on dialysis therapy. This article aims to review the current body of evidence of expanding use of CRT in these populations.

Loss of continuous biventricular pacing in cardiac resynchronization therapy patients: incidence, causes, and outcomes

INTRODUCTION AND OBJECTIVES

In recent years, implantation of cardiac resynchronization therapy devices has significantly increased. The benefits of this therapy are directly related to the maintenance of continuous biventricular pacing. This study analyzed the incidence, causes, and outcomes of loss of continuous biventricular pacing, and the approach adopted.

METHODS

We analyzed the clinical and follow-up data of a series of consecutive patients from a single center who underwent implantation of a cardiac resynchronization therapy device.

RESULTS

The study included 136 patients. During a mean follow-up of 33.4 months, loss of continuous biventricular pacing occurred in 45 patients (33%). The most common causes included atrial tachyarrhythmias (21.3%), lead macrodislodgement (18%), and loss of left ventricular capture (13.1%). In most patients (88.5%), loss of continuous biventricular pacing was transient and correctable, and occurred earlier in the follow-up when the cause was lead macrodislodgement, oversensing, or extracardiac stimulation. There were no significant differences in mortality between patients with and without loss of continuous biventricular pacing (P=.88).

CONCLUSIONS

Despite technical advances in cardiac resynchronization therapy, loss of continuous biventricular pacing is common; however, this loss can usually be corrected. In most patients, continuous biventricular pacing can be ensured by close monitoring and follow-up and a proactive approach.

Battery longevity in cardiac resynchronization therapy implantable cardioverter defibrillators

AIMS

Cardiac resynchronization therapy (CRT) implantable cardioverter defibrillators (ICDs) deliver high burden ventricular pacing to heart failure patients, which has a significant effect on battery longevity. The aim of this study was to investigate whether battery longevity is comparable for CRT-ICDs from different manufacturers in a contemporary cohort of patients.

METHODS AND RESULTS

All the CRT-ICDs implanted at our institution from 1 January 2008 to 31 December 2010 were included in this analysis. Baseline demographic and clinical data were collected on all patients using the electronic medical record. Detailed device information was collected on all patients from scanned device printouts obtained during routine follow-up. The primary endpoint was device replacement for battery reaching the elective replacement indicator (ERI). A total of 646 patients (age 69 ± 13 years), implanted with CRT-ICDs (Boston Scientific 173, Medtronic 416, and St Jude Medical 57) were included in this analysis. During 2.7 ± 1.5 years follow-up, 113 (17%) devices had reached ERI (Boston scientific 4%, Medtronic 25%, and St Jude Medical 7%, P < 0.001). The 4-year survival rate of device battery was significantly worse for Medtronic devices compared with devices from other manufacturers (94% for Boston scientific, 67% for Medtronic, and 92% for St Jude Medical, P < 0.001). The difference in battery longevity by manufacturer was independent of pacing burden, lead parameters, and burden of ICD therapy.

CONCLUSION

There are significant discrepancies in CRT-ICD battery longevity by manufacturer. These data have important implications on clinical practice and patient outcomes.

Cardiac resynchronization therapy mechanisms in atrial fibrillation

This article examines how to assess the reliability of potential techniques for performing optimization of biventricular pacemakers in patients with atrial fibrillation. It explores the magnitude of improvement that is likely to be obtained with the optimization of biventricular pacing in this clinical setting and discusses the lessons that can be learned with regard to the mechanisms of action of biventricular pacing in the general heart failure population.

Continuous monitoring of atrial fibrillation in heart failure

In patients with atrial fibrillation (AF) undergoing cardiac resynchronization therapy (CRT) for heart failure, continuous monitoring of the percentage of biventricular BiV% pacing has shown that the greatest improvement and reduction in mortality occur with a BiV pacing greater than 98%. Continuous monitoring of BiV pacing has improved the CRT management of patients with AF. Continuous monitoring has generated important new questions about anticoagulant therapy, which require randomized trials. Anticoagulant therapy should probably be considered in patients who have a high risk of thromboembolism according to standard scoring systems.

Complete atrioventricular block does not reduce long-term mortality in patients with permanent atrial fibrillation treated with cardiac resynchronization therapy

AIMS

A maximum percentage of ventricular pacing is mandatory to obtain a good response to CRT. Atrioventricular junction (AVJ) ablation has been recommended to attain this objective in patients with AF.

THE AIMS OF OUR STUDY WERE

(i) to determine whether the presence of complete AVJ block (induced or spontaneous) improves survival in patients with permanent AF treated with CRT and (ii) to analyse the predictors of mortality in AF patients treated with CRT.

METHODS AND RESULTS

From a series of 608 patients treated with CRT in our centre from 2000 to 2011, a cohort of 155 patients with permanent AF was analysed. Patients in AF were divided into two groups, AF + AVJ block [76 (49%)] and AF non-AVJ block [79 (51%)]. Mean follow-up was 30 months (interquartile range 13-51 months). During the follow-up, 62 patients died. Overall and cardiovascular mortality were similar between both groups: hazard ratio (HR) 0.85, 95% confidence interval (CI) 0.51-1.39, P = 0.51 and HR 0.94, 95% CI 0.52-1.68, P = 0.82. Multivariate analysis identified three independent predictors of mortality: basal NYHA functional class IV (HR 2.25, 95% CI 1.12-4.22, P = 0.03), glomerular filtration rate (HR 0.98, 95% CI 0.96-0.99, P = 0.03), and LVEF (HR 0.94, 95% CI 0.89-0.99, P = 0.02).

CONCLUSIONS

AVJ block did not improve survival for patients in AF treated with CRT. Basal NYHA functional class IV, poor renal function, and LVEF were the independent predictors of mortality.

Role of Atrio-Ventricular Junction Ablation in Symptomatic Atrial Fibrillation for Optimization of Cardiac Resynchronization Therapy

Cardiac resynchronization (CRT) therapy is indicated in patients with at least mildly symptomatic heart failure, left ventricular ejection fraction ≤35% and wide QRS, and has been associated with decreased morbidity and mortality. Unfortunately, approximately 30% of the patients appropriately selected for therapy do not respond to CRT. Among the reasons for non-response, atrial fibrillation (AF) plays a prominent role. AF limits the degree of biventricular pacing during CRT, not only when the ventricular rate is fast and highly irregular, but also during periods of of relatively constant rate, by causing fusion and pseudo-fusion complexes. Importantly, achievement of nearly 100% biventricular pacing is necessary to derive benefit from CRT. A simple, albeit irreversible, method to maximize biventricular pacing in patients with AF who are otherwise eligible for CRT is atrioventricular junction (AVJ) ablation. In this review, we discuss the role of AVJ ablation in CRT optimization in patients with AF. The available evidence from observational non-randomized studies suggests that AVJ ablation in patients with AF qualifying for CRT may offer improvement in heart failure symptoms, better survival, and better cardiac function. In light of the inherent limitations of non-randomized studies, further randomized studies are needed to support this treatment option.

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.

Single beat determination of intraventricular systolic dyssynchrony in patients with atrial fibrillation and systolic dysfunction

Background:

Atrial fibrillation (AF) is the most common clinically significant cardiac arrhythmia. However, diagnosis of intraventricular dyssynchrony in patients with AF is difficult due to beat-to-beat variation. Additionally, evaluation of mechanical dyssynchrony in the traditional method is based on average of 5 to 10 beats, which is exhausting and time consuming. Single-beat evaluation of a beat with equal subsequent cardiac cycles has been proposed as an accurate method in patients with AF.

Objectives:

We proposed to evaluate intraventricular mechanical dyssynchrony by measuring time-to-peak systolic velocity between basolateral and basoseptal segments (septum to lateral wall delay) using Tissue Doppler Study (TDI) by two different methods.

Materials and Methods:

31 patient (68 ± 10.3 years) with heart failure (EF < 35%) and AF rhythm, R-R cycle length more than 500 msec were evaluated. We found a target beat in which preceding R-R (R-R1) to pre-preceding R-R (R-R2) ratio was 1(RR1/RR2 = 1) then measured the intraventricular dyssynchrony in that cycle. Intraventricular dyssynchrony was also determined and averaged for 8 consecutive cardiac cycles. The values at RR1/RR2 = 1 were compared with the average of intraventricular dyssynchrony in eight cycles and the relationship between dyssynchrony were evaluated by paired T-test, linear Pearson correlation (r2), linear regression analysis.

Results:

The average of dyssynchrony in eight cycles showed a positive correlation with dyssynchrony in target beat RR1/RR2 = 1. Average of dyssynchrony in target beat was 46.77 msec, and average of 8 cycle was = 47.701, (P value = 0.776, Pearson linear correlation 0.769).

Conclusions:

Measurement of intraventricular dyssynchromy in basoseptal and basolateral segments in AF and heart failure patients in a single beat with RR1/RR2 = 1 , were very similar to the average value of eight cardiac cycle.

Ablate and Pace: Is There Still a Role?

Despite the development of newer drugs and procedures to improve rhythm control, there is still a place for ablation of the atrioventricular junction (AVJ) in the management of selected patients with AF who are refractory to medical therapy, to improve quality of life, prevent ventricular dysfunction, and to optimize cardiac resynchronization therapy. We review all aspects of the "ablate and pace" strategy, from its history to patient selection, technique, outcomes and applications, and identify the need for randomized clinical trials to address some of the remaining questions regarding its application in some groups of patients.