Primary Results From the SmartDelay Determined AV Optimization: A Comparison to Other AV Delay Methods Used in Cardiac Resynchronization Therapy (SMART-AV) Trial

Effects of AV delay and VV delay on left atrial pressure and waveform in ambulant heart failure patients: insights into CRT optimization

BACKGROUND

We hypothesized that left atrial pressure (LAP) obtained by a permanent implantable sensor is sensitive to changes in cardiac resynchronization therapy (CRT) settings and could guide CRT optimization to improve the response rate. We investigated the effect of CRT optimization on LAP and its waveform parameters in ambulant heart failure (HF) patients.

METHODS

CRT optimization was performed in eight ambulant HF patients, using echocardiography as reference. LAP waveform was acquired at each of eight atrioventricular (AV) intervals and five inter-ventricular (VV) intervals. Selected waveform parameters were also evaluated for their sensitivity to CRT changes and agreement with echocardiography-guided optimal settings.

RESULTS

Optimal AV and VV intervals varied considerably between patients. All patients exhibited significant changes in waveform morphology with AV optimization. Optimal AV delay determined from echocardiography ranged between 140 ms and 225 ms. Mean LAP tended to be lower at optimal setting 14 ± 3 mmHg compared to shorter (<100 ms) or longer (>160 ms) AV settings (P = 0.16). There were clear trends to smaller peak a-wave (P = 0.11) and gentler positive a-slope (P = 0.15) and positive v-slope (P = 0.09) with longer AV delays. Mean LAP and negative v-wave slope correlated well with echo-guided optimal setting, r = 0.91 (P = 0.001) and 0.79 (P = 0.03), respectively. No significant effects on LAP or waveform were seen during VV optimization.

CONCLUSIONS

LAP and its waveform changes considerably with AV optimization. There is good agreement between echo-guided optimal setting and LAP. LAP could provide an objective guide to CRT optimization. (Clinical Trial Registry information: URL: http://www.clinicaltrials.gov. Unique Identifier: NCT00632372).

Cardiac resynchronization therapy plus coupled pacing improves acutely myocardial function in heart failure patients

BACKGROUND

Coupled pacing (CP), which consists of an additional beat delivered after ventricular refractory period, has been proposed to reduce ventricular rate and increase ventricular contractility. We hypothesized that CP may be added to cardiac resynchronization therapy (CRT) to improve CRT effect in heart failure (HF) patients.

METHODS

The study included 20 consecutive HF patients in sinus rhythm referred for CRT-defibrillator (CRT-D) implantation (baseline left ventricular ejection fraction [LVEF] 27 ± 6%, baseline QRS duration 149 ± 33 ms, age = 63 ± 11 years). CP associated with CRT (CRT + CP) was delivered during CRT-D implantation from the right and left ventricular leads simultaneously. Echocardiography data were collected at baseline, during CRT and CRT + CP to assess changes in LVEF, cardiac output (CO), longitudinal global strain assessed by speckle tracking, and LV dyssynchrony (opposing wall delay using tissue Doppler imaging).

RESULTS

Compared to the conventional CRT, heart rate (HR) markedly decreased during CRT + CP (79 ± 20 beats/min vs 51 ± 8 beats/min, P < 0.0001) and was associated with a significant increase in LVEF (30 ± 8% vs 35 ± 8%, P = 0.0002) and peak of longitudinal global strain (-6 ± 2% vs -8 ± 2%, P < 0.0001). Importantly, during CRT + CP, CO increased (3.8 ± 1.0 L/min vs 4.4 ± 1.4 L/min, P = 0.004) and cardiac synchronicity remained unchanged (38 ± 24 ms for CRT alone vs 27 ± 18 ms for CRT + CP, P = 0.1).

CONCLUSION

In sinus rhythm HF patients, acute CP application in addition to CRT decreases HR and contributes to myocardial contractility and CO improvement without deleterious impact on ventricular synchronicity.

Hemodynamic benefit of rest and exercise optimization of cardiac resynchronization therapy

The optimal method of cardiac resynchronization therapy (CRT) optimization is as yet unknown. We sought to investigate the responses of optimization at rest and on exercise. This 2 stage study involved 59 patients (age 65 ± 10, 75% male), who had all recently undergone successful CRT implantation. In the first stage, the 6-month response was compared between 30 individuals who underwent resting echocardiographic optimization of CRT [atrioventricular (AV delay) plus ventriculo-ventricular delays (VV delay)], compared with the 29 who did not. In the second stage, a subset of 37 patients from the original cohort were randomized (double-blind) to either resting echocardiographic optimization (n = 20) or exercise echocardiographic optimization (n = 17) and followed for a further 6 months. Clinical and echocardiographic data were collected at each stage. Patients undergoing rest optimization demonstrated improvement in almost all variables and significantly in B-type natriuretic peptide (BNP) in contrast to those without optimization. In a linear regression model, the only significant predictor of BNP change was whether an individual underwent resting optimization or not (β = 0.38, P = 0.04). In those undergoing resting optimization, the degree of change in AV delay was correlated with improvement in left ventricle (LV) end-diastolic volume (r(2)  = 0.33, P < 0.01). Optimization on exercise was associated with a significant decrease in 6-minute walk test compared to those randomized to rest optimization possibly due to inducing nonoptimization at rest. In conclusion, echocardiographic optimization of CRT at rest is superior to no optimization or optimization on exercise. Patients with the greatest change in AV delay to reach optimal may undergo greater LV remodeling.

Canadian Cardiovascular Society guidelines on the use of cardiac resynchronization therapy: implementation

Recent studies have provided the impetus to update the recommendations for cardiac resynchronization therapy (CRT). This article provides guidance on the implementation of CRT and is intended to serve as a framework for the implementation of CRT within the Canadian health care system and beyond. These guidelines were developed through a critical evaluation of the existing literature, and expert consensus. The panel unanimously adopted each recommendation. The 9 recommendations relate to patient selection in the presence of comorbidities, delivery and optimization of CRT, and resources required to deliver this therapy. The strength of evidence was weighed, taking full consideration of any risk of bias, and 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.

Impact of QRS Morphology and Duration on Outcomes After Cardiac Resynchronization Therapy

Background—

The impact of QRS morphology and duration on the effectiveness of cardiac resynchronization therapy (CRT) has been usually assessed separately. The interaction between these 2 simple ECG parameters and their effect on CRT has not been systematically assessed in a large-scale clinical trial.

Methods and Results—

The Resynchronization–Defibrillation for Ambulatory Heart Failure Trial showed that implantable cardioverter defibrillator-CRT was associated with a significant reduction in the primary end point of all-cause mortality or heart failure hospitalization. For this substudy, we excluded patients in atrial fibrillation and those with a previous pacemaker. All baseline ECGs were reviewed by a panel of 3 experienced electrocardiographers. A total of 1483 patients were included in this study. Of these, 1175 had left bundle-branch block (LBBB) and 308 had non-LBBB. In patients with LBBB receiving implantable cardioverter defibrillator-CRT, there was a reduction in the primary outcome and in each individual component of the primary outcome. Furthermore, there was continuous relationship between QRS duration and extent of benefit. In patients with non-LBBB and QRS ≥160 ms, the hazard ratio for the primary outcome was 0.52 (0.29–0.96; P =0.033); in patients with QRS <160 ms, the hazard ratio was 1.38 (0.88–2.14; P =0.155).

Conclusions—

In patients with LBBB, there was a continuous relationship between broader QRS and greater benefit from implantable cardioverter defibrillator-CRT. However, our data do not support the use of implantable cardioverter defibrillator-CRT in patients with non-LBBB, especially when the QRS duration is <160 ms. There may be some delayed benefit when the QRS is ≥160 ms, but this needs further investigation.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00251251.

Impact of Ejection Fraction on the Clinical Response to Cardiac Resynchronization Therapy in Mild Heart Failure

Background—

Current guidelines recommend cardiac resynchronization therapy (CRT) in mild heart failure (HF) patients with QRS prolongation and ejection fraction (EF) ≤30%. To assess the effect of CRT in less severe systolic dysfunction, outcomes in the REsynchronization reVErses Remodeling in Systolic left vEntricular dysfunction (REVERSE) study were evaluated in which patients with left ventricular (LV) ejection fraction (LVEF) >30% were included.

Methods and Results—

The results of patients with baseline EF >30% (n=177) and those with EF ≤30% (n=431), as determined by a blinded core laboratory, were compared. In the LVEF >30% subgroup, there was a trend for improvement in the clinical composite response with CRT ON versus CRT OFF ( P =0.06) and significant reductions in LV end systolic volume index (−6.7±21.1 versus 2.1±17.6 mL/m 2 ; P =0.01) and LV mass (−20.6±50.5 versus 5.0±42.4 g; P =0.04) after 12 months. The time to death or first HF hospitalization was significantly prolonged with CRT (hazard ratio, 0.26; P =0.012). In the LVEF <30% subgroup, significant improvements in clinical composite response ( P =0.02), reverse remodeling parameters, and time to death or first HF hospitalization (hazard ratio, 0.58; P =0.047) were observed. After adjusting for important covariates, the CRT ON assignment remained independently associated with improved time to death or first HF hospitalization (hazard ratio, 0.54; P =0.035), whereas there was no significant interaction with LVEF.

Conclusions—

Among subjects with mild HF, QRS prolongation, and LVEF >30%, CRT produced reverse remodeling and similar clinical benefit compared with subjects with more severe LV systolic dysfunction.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifier: NCT00271154.

Three-dimensional echocardiographic optimization improves outcome in cardiac resynchronization therapy compared to ECG optimization: a randomized comparison

AIMS

There is little consensus on optimal atrioventricular (AV) and ventricular-to-ventricular (VV) intervals in cardiac resynchronization therapy (CRT). The aim of this study was to examine a novel combination of Doppler echocardiography (DE) and three-dimensional echocardiography (3DE) for individualized AV- and VV-interval optimization compared to conventional electrocardiogram (ECG) optimization.

METHODS

In this double-blind, randomized controlled trial, 77 patients (male: 57, age: 68 ± 10 years) with severely reduced ejection fraction (EF), New York Heart Association (NYHA) class III or IV, and wide QRS complex (>120 ms) have been included. Patients were randomized to either AV- and VV-interval optimization using DE and 3DE (group 1, n = 39) or ECG (group 2, n = 38). 3DE was performed in all patients for the evaluation of left ventricular (LV) dimensions, EF and systolic dyssynchrony index (SDI), and NYHA class obtained before CRT and after 3 months. Primary endpoint of the study was clinical response to CRT, defined as a reduction of NYHA class by ≥1 score. Secondary endpoints were change of EF, LV volumes, and SDI.

RESULTS

There were significantly more responders in group 1 (82%) than in group 2 (58%, P = 0.021). Similarly, group 1 showed a larger increase in EF (7.0 ± 6.0% vs 3.4 ± 5.6%, P = 0.015) and a more pronounced reduction of SDI (-4.5 ± 5.9% vs -1.5 ± 5.6%, P = 0.039) than group 2.

CONCLUSION

Compared with conventional ECG optimization, this novel echocardiographic optimization protocol resulted in a significantly higher response rate, improved LV systolic function, and may be used to select the optimal AV and VV intervals in CRT.

Cardiac resynchronisation therapy optimisation strategies: systematic classification, detailed analysis, minimum standards and a roadmap for development and testing

In this article an international group of CRT specialists presents a comprehensive classification system for present and future schemes for optimising CRT. This system is neutral to the measurement technology used, but focuses on little-discussed quantitative physiological requirements. We then present a rational roadmap for reliable cost-effective development and evaluation of schemes. A widely recommended approach for AV optimisation is to visually select the ideal pattern of transmitral Doppler flow. Alternatively, one could measure a variable (such as Doppler velocity time integral) and "pick the highest". More complex would be to make measurements across a range of settings and "fit a curve". In this report we provide clinicians with a critical approach to address any recommendations presented to them, as they may be many, indistinct and conflicting. We present a neutral scientific analysis of each scheme, and equip the reader with simple tools for critical evaluation. Optimisation protocols should deliver: (a) singularity, with only one region of optimality rather than several; (b) blinded test-retest reproducibility; (c) plausibility; (d) concordance between independent methods; and (e) transparency, with all steps open to scrutiny. This simple information is still not available for many optimisation schemes. Clinicians developing the habit of asking about each property in turn will find it easier to win now down the broad range of protocols currently promoted. Expectation of a sophisticated enquiry from the clinical community will encourage optimisation protocol-designers to focus on testing early (and cheaply) the basic properties that are vital for any chance of long term efficacy.

Interplay of electrical wavefronts as determinant of the response to cardiac resynchronization therapy in dyssynchronous canine hearts

BACKGROUND

The relative contribution of electromechanical synchronization and ventricular filling to the optimal hemodynamic effect in cardiac resynchronization therapy (CRT) during adjustment of stimulation-timings is incompletely understood. We investigated whether optimal hemodynamic effect in CRT requires collision of pacing-induced and intrinsic activation waves and optimal filling of the left ventricle (LV).

METHODS AND RESULTS

CRT was performed in dogs with chronic left bundle-branch block (n=8) or atrioventricular (AV) block (n=6) through atrial (A), right ventricular (RV) apex, and LV-basolateral pacing. A 100 randomized combinations of A-LV/A-RV intervals were tested. Total activation time (TAT) was calculated from >100 contact mapping electrodes. Mechanical interventricular dyssynchrony was determined as the time delay between upslopes of LV and RV pressure curves. Settings providing an increase in LVdP/dtmax (maximal rate of rise of left ventricular pressure) of ≥90% of the maximum LVdP/dtmax value were defined as optimal (CRTopt). Filling was assessed by changes in LV end-diastolic volume (EDV; conductance catheter technique). In all hearts, CRTopt was observed during multiple settings, providing an average LVdP/dtmax increase of ≈15%. In AV-block hearts, CRTopt exclusively depended on interventricular-interval and not on AV-interval. In left bundle-branch block hearts, CRTopt occurred at A-LV intervals that allowed fusion of LV-pacing-derived activation with right bundle-derived activation. In all animals, CRTopt occurred at settings resulting in the largest decrease in TAT and mechanical interventricular dyssynchrony, whereas LV EDV hardly changed.

CONCLUSIONS

In left bundle-branch block and AV-block hearts, optimal hemodynamic effect of CRT depends on optimal interplay between pacing-induced and intrinsic activation waves and the corresponding mechanical resynchronization rather than filling.

Clinical response with adaptive CRT algorithm compared with CRT with echocardiography-optimized atrioventricular delay: a retrospective analysis of multicentre trials

AIMS

Adaptive cardiac resynchronization therapy (aCRT) is a novel algorithm for CRT pacing that provides automatic ambulatory selection between synchronized left ventricular (LV) or bi-ventricular (BiV) pacing and optimization of atrioventricular (AV) and inter-ventricular (VV) delays based on periodic measurement of intrinsic conduction. We aimed to compare the clinical response between aCRT and standard CRT in historical trials.

METHODS AND RESULTS

The treatment arm of the aCRT trial was compared with a pooled historical control (HC) derived from the CRT arms of four clinical trials (MIRACLE, MIRACLE ICD, PROSPECT, and InSync III Marquis) with respect to the proportion of patients who had an improved clinical composite score (CCS) at the 6-month follow-up. Patients in the HC underwent echocardiography-guided AV optimization after the implant. A propensity score model was used to adjust for 22 potential baseline confounders of the effect of CRT. Patients were stratified into quintiles according to the propensity score and the adjusted absolute treatment effect was obtained by averaging estimates across these quintiles. The propensity score model included 751 patients (aCRT: 266, historical trials: 485). The adjusted absolute difference in percent improved in CCS between the aCRT and HC arms was 11.9% [95% confidence interval (CI): 2.7-19.2%] favouring aCRT. The patients in the aCRT group were significantly more likely to have an improved CCS than the patients in the HC (odds ratio = 1.65, 95% CI: 1.1-2.5).

CONCLUSION

The aCRT algorithm may be associated with additional improvement in clinical response compared with historical CRT with echocardiographic AV optimization.

Optimal utilization and management of implanted cardiac rhythm devices in patients hospitalized for heart failure

Improved utilization and optimization of device therapy in the management of patients with decompensated heart failure (HF) is an important clinical priority. Diagnostic cardiac rhythm device data have been shown to predict hospitalization for HF. Cardiac resynchronization therapy is a highly effective therapy for the prevention of HF hospitalization. Evaluation and optimization of cardiac resynchronization therapy should be considered in all patients admitted with HF despite cardiac resynchronization therapy.

Targeting left ventricular lead placement to improve cardiac resynchronization therapy outcomes

Although cardiac resynchronization therapy (CRT) has been established as an important treatment modality for heart failure patients, at least one third of CRT recipients do not respond to this therapy or derive minimal benefit from it. The impact of the site of left ventricular (LV) pacing on outcome after CRT has been examined extensively. Initial studies suggested benefit of posterior or lateral sites but subsequent work has yielded conflicting results. There also remain conflicting results of apical vs basal pacing sites. Avoiding LV lead placement at sites of transmural scar is however a viable strategy. In addition, The TARGET and STARTER trials, 2 independent, randomized, prospective studies, have demonstrated that targeting LV lead placement to sites of latest LV mechanical activation as defined by speckle tracking echocardiography remains the most promising method to improve clinical outcome after CRT.

Effect of atrioventricular and ventriculoventricular delay optimization on clinical and echocardiographic outcomes of patients treated with cardiac resynchronization therapy: a meta-analysis

BACKGROUND

Optimization of atrioventricular (AV) and ventriculoventricular (VV) delays of cardiac resynchronization therapy (CRT) devices maximizes left ventricular filling and stroke volume. However, the incremental value of these optimizations over empiric device programming remains unclear. The objective of this analysis was to perform a systematic review and meta-analysis of the effects of AV and VV delay optimization on clinical and echocardiographic end points of patients with heart failure treated with CRT.

METHODS

A standardized search strategy was performed and identified 12 trials comparing AV and/or VV delay optimization and conventional CRT device programming and their effects on various clinical and echocardiographic outcomes. Pooled odds ratios were analyzed using random-effect meta-analysis with Mantel-Haenszel method.

RESULTS

Combined data from a total of 4,356 patients with heart failure treated with CRT showed no differences in clinical or echocardiographic outcomes between patients who underwent AV and/or VV delay optimization and patients who underwent empiric device programming (Mantel-Haenszel odds ratio 0.86 [95% CI 0.68-1.09], P value for overall effect = .21 by intention-to-treat analysis).

CONCLUSION

The current literature suggests that routine AV and/or VV delay optimization has a neutral effect on clinical and echocardiographic outcomes based on pooled data from randomized and nonrandomized studies. Standardization of patient selection and optimization timing and method may help to further define the role of CRT device optimization.

Optimizing cardiac resynchronization therapy for congestive heart failure

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

Cardiac resynchronisation therapy: a randomised trial of factory or echocardiographic settings for optimum response

BACKGROUND

We aimed to assess whether echocardiographically-optimised atrioventricular (AV) and interventricular (VV) delay programming provided any additional benefit over standard settings following biventricular pacemaker implantation in patients with advanced heart failure.

METHODS

Paired data were collected on 22 patients (aged 67.5 ± 8.3 years, 16 male) with refractory heart failure, NYHA class III/IV symptoms, sinus rhythm, LBBB and a broad QRS complex >120 ms. All patients underwent implantation of a biventricular pacemaker and were randomised to eight weeks of factory pacing mode (Mode 1) or echocardiographically-guided pacing mode (Mode 2), followed by eight weeks in the alternate mode, in a randomised blinded crossover design.

RESULTS

Peak oxygen consumption, 6 min walk distance, NYHA class and quality of life scores improved after biventricular pacing, but no significant difference was found between the two modes, with the exception of peak oxygen consumption score (baseline: 14.8 ± 0.9, Mode 1: 14.6 ± 1.2, Mode 2: 16.1 ± 1.2 mL/kg/min), which was better in Mode 2 than Mode 1 (p 0.003).

CONCLUSION

Transthoracic echocardiographic optimisation of AV and VV delays following biventricular pacing may offer additional clinical benefit in an unselected group of patients when compared with factory settings.

Association between frequent cardiac resynchronization therapy optimization and long-term clinical response: a post hoc analysis of the Clinical Evaluation on Advanced Resynchronization (CLEAR) pilot study

Aims

The long-term clinical value of the optimization of atrioventricular (AVD) and interventricular (VVD) delays in cardiac resynchronization therapy (CRT) remains controversial. We studied retrospectively the association between the frequency of AVD and VVD optimization and 1-year clinical outcomes in the 199 CRT patients who completed the Clinical Evaluation on Advanced Resynchronization study.

Methods and results

From the 199 patients assigned to CRT-pacemaker (CRT-P) (New York Heart Association, NYHA, class III/IV, left ventricular ejection fraction <35%), two groups were retrospectively composed a posteriori on the basis of the frequency of their AVD and VVD optimization: Group 1 (n = 66) was composed of patients ‘systematically’ optimized at implant, at 3 and 6 months; Group 2 (n = 133) was composed of all other patients optimized ‘non-systematically’ (less than three times) during the 1 year study. The primary endpoint was a composite of all-cause mortality, heart failure-related hospitalization, NYHA functional class, and Quality of Life score, at 1 year. Systematic CRT optimization was associated with a higher percentage of improved patients based on the composite endpoint (85% in Group 1 vs. 61% in Group 2, P < 0.001), with fewer deaths (3% in Group 1 vs. 14% in Group 2, P = 0.014) and fewer hospitalizations (8% in Group 1 vs. 23% in Group 2, P = 0.007), at 1 year.

Conclusion

These results further suggest that AVD and VVD frequent optimization (at implant, at 3 and 6 months) is associated with improved long-term clinical response in CRT-P patients.

Comparison of different invasive hemodynamic methods for AV delay optimization in patients with cardiac resynchronization therapy: implications for clinical trial design and clinical practice

Background

Reproducibility and hemodynamic efficacy of optimization of AV delay (AVD) of cardiac resynchronization therapy (CRT) using invasive LV dp/dt_max are unknown.

Method and results

25 patients underwent AV delay (AVD) optimisation twice, using continuous left ventricular (LV) dp/dt_max, systolic blood pressure (SBP) and pulse pressure (PP). We compared 4 protocols for comparing dp/dt_max between AV delays:

Immediate absolute: mean of 10 s recording of dp/dt_max acquired immediately after programming the tested AVD,

Delayed absolute: mean of 10 s recording acquired 30 s after programming AVD,

Single relative: relative difference between reference AVD and the tested AVD,

Multiple relative: averaged difference, from multiple alternations between reference and tested AVD.

We assessed for dp/dt_max, LVSBP and LVPP, test–retest reproducibility of the optimum.

Optimization using immediate absolute dp/dt_max had poor reproducibility (SDD of replicate optima = 41 ms; R² = 0.45) as did delayed absolute (SDD 39 ms; R² = 0.50). Multiple relative had better reproducibility: SDD 23 ms, R² = 0.76, and (p < 0.01 by F test).

Compared with AAI pacing, the hemodynamic increment from CRT, with the nominal AV delay was LVSBP 2% and LVdp/dt_max 5%, while CRT with pre-determined optimal AVD gave 6% and 9% respectively.

Conclusions

Because of inevitable background fluctuations, optimization by absolute dp/dt_max has poor same-day reproducibility, unsuitable for clinical or research purposes. Reproducibility is improved by comparing to a reference AVD and making multiple consecutive measurements. More than 6 measurements would be required for even more precise optimization — and might be advisable for future study designs. With optimal AVD, instead of nominal, the hemodynamic increment of CRT is approximately doubled.

How to improve outcomes: should we put more emphasis on programming and medical care and less on patient selection?

Many factors contribute to the pathophysiology and progression of heart failure (HF), offering the potential for many synergistic therapeutic approaches to its management. For patients, who have systolic HF, prolonged QRS and receiving guideline-indicated pharmacological therapy, cardiac resynchronization therapy (CRT) may provide additional benefits in terms of symptom improvement and mortality reduction. Nevertheless, in many patients, moderate or severe symptoms may persist or recur after CRT implantation due to either the severity or progression of the underlying disease, the presence of important co-morbidities or suboptimal device programming. Identifying and, where possible, treating the reasons for persistent or recurrent symptoms in patients who have received CRT is an important aspect of patient care. The present review summarizes the available evidence on this topic.

Cardiac resynchronization therapy: a breakthrough in heart failure management

Heart failure is now considered an epidemic. In patients with heart failure, electrical and mechanical dyssynchrony, evident primarily as prolongation of the QRS-complex on the surface electrocardiogram, is associated with detrimental effects on the cardiovascular system at several levels. In the past 10 years, studies have demonstrated that by stimulating both cardiac ventricles simultaneously, or almost simultaneously [cardiac resynchronization therapy (CRT)], the adverse effects of dyssynchrony can be overcome. Here, we provide a comprehensive overview of different aspects of CRT including the rationale behind and evidence for efficacy of the therapy. Issues with regard to gender effects and patient follow-up as well as a number of unresolved concerns will also be discussed.

The Contemporary Role of Echocardiography in Improving Patient Response to Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) is an important therapy for heart failure patients with widened electrocardiographic QRS complexes and depressed ejection fractions, however, approximately one-third do not respond. This article presents a practical contemporary approach to the utility of echocardiography to improve CRT patient response by assessing mechanical dyssynchrony, optimizing left ventricular lead positioning, and performing appropriate echo-Doppler optimization, along with future potential roles. Specifically, recent long-term outcome data are presented that demonstrates that baseline dyssynchrony is a powerful marker associated with CRT response, in particular for patients with narrower QRS duration or non left bundle branch block morphology. Advances in speckle tracking echocardiography to tailor delivery of CRT by guiding LV lead position is discussed, including data from randomized clinical trials supporting targeting the LV lead toward the site of latest activation. In addition, an update on the current role of Doppler echocardiographic device optimization after CRT implantation is reviewed.