Predictors of response to cardiac resynchronization therapy (PROSPECT)--study design

Optimal use of echocardiography in cardiac resynchronisation therapy

Echocardiography has several roles in patients with cardiac resynchronisation therapy (CRT). First, it can optimise selection of CRT candidates by demonstration of left ventricular (LV) dyssynchrony. Second, it can be used to assess immediate response to CRT, including detection of acute LV resynchronisation. Echocardiography is also useful to evaluate long-term benefit from CRT. Finally, echocardiography is important in optimisation of pacemaker settings, including AV and VV optimisation.

Results of the SCART study: selection of candidates for cardiac resynchronisation therapy

OBJECTIVE

To prospectively determine whether prespecified electrocardiographic, echocardiographic and tissue Doppler imaging (TDI) selection criteria may predict a positive response to cardiac resynchronisation therapy (CRT).

METHODS

In this multicentre, prospective, non-randomised study, 96 heart failure patients with New York Heart Association class III-IV symptoms, an ejection fraction of < or =35%, and at least one marker of ventricular dyssynchrony according to prespecified electrocardiographic, echocardiographic or TDI criteria were enrolled. The primary endpoint was an improvement in the clinical composite score at 6 months.

RESULTS

At enrolment, 70 patients fulfilled the electrocardiographic criterion (QRS duration > or =150 ms), 77 patients showed echocardiographic signs of dyssynchrony, and 37 patients met the TDI dyssynchrony criteria. The overall responder rate was 78/96 (81%). In particular, the primary endpoint was reached in 68 patients who fulfilled the echocardiographic criteria as compared with 10 patients who did not (88 vs. 53%, P = 0.001). The patients who met the echocardiographic criteria showed a significant greater reduction in left ventricular end-systolic diameter (P = 0.029) and a higher improvement in quality of life (P = 0.017) than patients who did not. Neither electrocardiographic nor TDI criteria seemed to predict a positive response to CRT.

CONCLUSIONS

In our patient population, mechanical indexes of dyssynchrony as assessed by echocardiography appeared to identify CRT responders. Although TDI is useful for evaluating ventricular dyssynchrony after CRT, the prespecified TDI inclusion criteria adopted in this investigation did not increase the number of CRT responders.

Measurements of mechanical asynchrony in patients with heart failure: is the puzzle completed?

Numerous randomized clinical trials demonstrated the beneficial effects of cardiac resynchronization therapy (CRT) in the treatment of moderate to severe heart failure. Despite careful patient selection, there is still a percentage of non-responders, that is as high as 30-50%. Patients are selected mainly on electrocardiogram criteria. Recent studies have observed that the severity of mechanical systolic asynchrony is a much better predictor of a response after CRT. Echocardiography allows a non-invasive evaluation atrioventricular and inter- and intraventricular synchrony; furthermore, recent advances have provided direct evidence of wall motion resynchronization in patients receiving CRT. Nevertheless, although many authors tried to search for the best echocardiographic index to identify systolic asynchrony, and consequently responders to CRT before the procedure, this issue is still a matter of debate. Our aim was to make an updated review of the more recent studies on this topic.

Clinical trials update from the European Society of Cardiology Congress 2007: 3CPO, ALOFT, PROSPECT and statins for heart failure

This article provides information and a commentary on trials relevant to the pathophysiology, prevention and treatment of heart failure, presented at the European Society of Cardiology Congress 2007. Unpublished reports should be considered as preliminary data, as analyses may change in the final publication. In the 3CPO study, non-invasive ventilation produced a more rapid resolution of symptoms in patients hospitalised with acute cardiogenic pulmonary oedema; but had no effect on survival, compared to standard oxygen therapy. The ALOFT study showed that the selective oral renin inhibitor aliskiren reduces plasma BNP levels and is well tolerated in patients with heart failure receiving ACE inhibitors or ARBs, although the study was not powered to show clinical benefit. In the PROSPECT study, no echocardiographic measure of mechanical dyssynchrony was identified that was useful for identifying patients more or less likely to respond to CRT. Low dose atorvastatin reduced the incidence of sudden cardiac death in a small placebo controlled study of patients with advanced chronic heart failure.

Cardiac Resynchronization Therapy: Variations in Echo-Guided Optimized Atrioventricular and Interventricular Delays During Follow-Up

BACKGROUND

Relatively few data are available on long-term echocardiographic optimization of atrioventricular (AV) and interventricular (VV) delay programming in cardiac resynchronization therapy (CRT). We assessed variations in optimized AV and VV delays during long-term follow-up.

METHODS

Thirty-seven consecutive heart failure patients received Doppler echocardiographic optimization of AV and VV delay within 48 hours from CRT device implantation, at 6 months and at 12 months (the last for the first enrolled 14 patients).

RESULTS

After implantation, median optimized AV delay was 100 ms (range, 45 ms); VV optimization led to simultaneous biventricular activation in 4 patients, left ventricular preactivation in 17 patients and right ventricular preactivation in 16 patients. At 12 months median AV delay decreased to 85 ms (23 ms) (P < 0.05 vs. baseline). With respect to previous assessment, VV delay variations > or =40 ms were observed in 41% of the patients at 6 months and in 57% of the tested patients at 12 months. A nonconcordance (by Kappa test) of optimized VV delays was found between each new assessment and the previous one. VV delay optimization was associated with significant (P < 0.001) increases in aortic velocity time integral both at baseline and during follow-up.

CONCLUSIONS

Echocardiographic optimization of AV and VV delay is associated with broad intraindividual variability during follow-up. A new assessment of optimized VV delays during long-term follow-up reveals a nonconcordance with previous values and provides increases in forward stroke volume.

New guidelines for cardiac resynchronisation therapy: simplicity or complexity for the doctor?

See article on page 1134

[Electrotherapy of cardiac failure]

Intracardiac conduction disturbances, mostly manifested as a left bundle branch block (LBBB), are common findings in cardiac failure and associated with a poor prognosis. LBBB is a marker of disease progression and also leads to worsened cardiac hemodynamics by dyssynchronous contraction that can accelerate progression of the underlying disease. Cardiac resynchronization therapy (CRT) can reduce the negative effects of these disturbances leading to improvement in hemodynamics and long-term improvement in cardiopulmonary exercise tolerance, reduction of left ventricular volumes and functional mitral regurgitation. Prospective multicenter studies, such as the CARE-HF and COMPANION trials have demonstrated reduced mortality with CRT or combined treatment with defibrillator capability (CRT-D). Thus, CRT has been adopted in the current guidelines of cardiology societies. Nevertheless, there are a number of open issues with CRT, such as the high number of non-responders or the value of CRT in patients with atrial fibrillation, narrow QRS complex and mild cardiac failure or asymptomatic left ventricular dysfunction. In addition, the question whether every CRT patient needs a device with defibrillating capabilities is not fully resolved, at least for patients with dilative cardiomyopathy.

Echocardiography in Heart Failure

Echocardiography is well qualified to meet the growing need for noninvasive imaging in the expanding heart failure (HF) population. The recently-released American College of Cardiology/American Heart Association guidelines for the diagnosis and management of HF labeled echocardiography "the single most useful diagnostic test in the evaluation of patients with HF...," because of its ability to accurately and noninvasively provide measures of ventricular function and assess causes of structural heart disease. It can also detect and define the hemodynamic and morphologic changes in HF over time and might be equivalent to invasive measures in guiding therapy. In this article we will discuss: 1) the clinical uses of echocardiography in HF and their prognostic value; 2) the use of echocardiography to guide treatment in HF patients; and 3) promising future techniques for echocardiographic-based imaging in HF. In addition, we will highlight some of the limitations of echocardiography.

Echocardiographic evaluation of cardiac dyssynchrony

First described a decade ago, cardiac resynchronization therapy (CRT) has recently become a proven therapeutic strategy for refractory heart failure. Large clinical trials have shown a reduction in both morbidity and mortality in patients treated with CRT. Initial patient selection has relied mainly on electrocardiographic criteria, which allows identification of only 70% of responders. Accordingly, echocardiographic criteria were developed to identify mechanical dyssynchrony in an effort to improve patient selection. Multiple echocardiographic criteria have since been proposed, with no consensus as to which parameter better predicts CRT response. Although comparison studies using different criteria are underway, current evaluation of dyssynchrony should probably use an integrated multiparameter approach. The objective of the present article was to review the role of echocardiography in the evaluation of cardiac dyssynchrony in clinical practice.

Imaging techniques in cardiac resynchronization therapy

Cardiac resynchronization therapy is a high cost therapeutic option with proven efficacy on improving symptoms of ventricular failure and for reducing both hospitalization and mortality. However, a significant number of patients do not respond to cardiac resynchronization therapy that is due to various reasons. Identification of the optimal pacing site is crucial to obtain the best therapeutic result that necessitates careful patient selection. Currently, using echocardiography for mechanical dyssynchrony assessment performs patient selection. Multi-Detector-Row Computed Tomography (MDCT) and Magnetic Resonance Imaging (MRI) are new imaging techniques that may assist the cardiologist in patient selection. These new imaging techniques have the potential to improve the success rate of cardiac resynchronization therapy, due to pre-interventional evaluation of the venous coronary anatomy, to evaluation of the presence of scar tissue, and to improved evaluation of mechanical dyssynchrony. In conclusion, clinical issues associated with heart failure in potential candidates for cardiac resynchronization therapy, and the information regarding this therapy that can be provided by the imaging techniques echocardiography, MDCT, and MRI, are reviewed.

Reduced Ventricular Volumes and Improved Systolic Function With Cardiac Resynchronization Therapy

Background— Cardiac resynchronization therapy has emerged as an important therapy for advanced systolic heart failure. Among available cardiac resynchronization therapy pacing modes that restore ventricular synchrony, it is uncertain whether simultaneous biventricular (BiV), sequential BiV, or left ventricular (LV) pacing is superior. The Device Evaluation of CONTAK RENEWAL 2 and EASYTRAK 2: Assessment of Safety and Effectiveness in Heart Failure (DECREASE-HF) trial is the first randomized trial comparing these 3 cardiac resynchronization therapy modalities.

Methods and Results— The DECREASE-HF Trial is a multicenter trial in which 306 patients with New York Heart Association class III or IV heart failure, an LV ejection fraction ≤35%, and a QRS duration ≥150 ms were randomized to simultaneous BiV, sequential BiV, or LV pacing. LV volumes and systolic and diastolic function were assessed with echocardiography at baseline, 3 months, and 6 months. All groups had a significant reduction in LV end-systolic and end-diastolic dimensions ( P <0.001). The simultaneous BiV pacing group had the greatest reduction in LV end-systolic dimension ( P =0.007). Stroke volume ( P <0.001) and LV ejection fraction ( P <0.001) improved in all groups with no difference across groups.

Conclusions— Compared with LV pacing, simultaneous BiV pacing was associated with a trend toward greater improvement in LV size. There is little difference between simultaneous BiV pacing and sequential BiV pacing as programmed in this trial.

Cardiac resynchronization therapy

About 30% of patients with left ventricular systolic dysfunction also have ventricular conduction delays (prolonged QRS duration greater than 0.12 second) most frequently seen as left bundle branch block. This intraventricular conduction delay causes nonsynchronous ventricular activation between the right ventricle and the left ventricle (or dyssychrony), compromising cardiac function. Cardiac resynchronization therapy, or biventricular pacing, is a recent intervention for ventricular dyssychrony that incorporates 3 leads for pacing the right atrium and simultaneous pacing of the right ventricle and left ventricle. Left ventricular lead placement can be difficult to implant because of coronary venous anatomy and can require longer procedure time for the patient. Restoring ventricular synchrony has been shown to decrease septal wall dyskinesis, decrease mitral regurgitation, increase left ventricular filling time, decrease pulmonary capillary wedge pressure, and reverse ventricular modeling.

Tissue Doppler predicts long-term clinical outcome after cardiac resynchronization therapy

BACKGROUND

Pulsed-wave tissue Doppler imaging (TDI) was shown to predict short-term left ventricular functional recovery after cardiac resynchronization therapy (CRT). However, few data are available regarding the baseline cardiac asynchrony and clinical outcome after CRT. Therefore, we aimed to investigate the prognostic value of pre-CRT cardiac asynchrony on clinical outcome after CRT.

METHODS

The study population consisted of 48 consecutive patients with moderate to severe heart failure and a wide QRS complex undergoing implantation of biventricular pacemaker. Cardiac asynchrony was assessed at pulsed-wave TDI from measurements of regional electromechanical coupling times in basal segments of both ventricles (Sum asynchrony). Clinical end-points were cardiac mortality and hospitalization for worsening heart failure.

RESULTS

During a follow-up period of 970+/-319 days, clinical end-point (9 deaths, 15 hospitalizations) occurred in 24 patients (clinical nonresponders). At baseline, responders showed higher asynchrony than nonresponders (153+/-57 ms vs. 103+/-58 ms, p<0.01). Sum asynchrony of >98 ms showed the highest accuracy (AUC=0.80, sensitivity 92%, specificity 67%) to identify responders. In contrast, baseline NYHA class, conventional echo-Doppler indices and QRS complex duration were similar in both groups. Eight end-point events (3 deaths) occurred in 30 patients with significant Sum asynchrony (>98 ms) as compared to 16 events (6 deaths) in 18 patients with smaller Sum asynchrony (27% vs. 89%; HR 0.14; 95% CI 0.04 to 0.46; p<0.001). Favorable clinical outcome was associated with larger left ventricular functional recovery at 2 years follow-up (p<0.001).

CONCLUSIONS

TDI-derived index of baseline intra- and interventricular asynchrony appears to predict long-term clinical outcome after CRT.

[Heart failure in 2006]

This article are summarizes the most relevant articles in the field of heart failure including epidemiology, diagnostic and therapeutic issues. Therapy includes drugs, cardiac resinchronization therapy, automatic implantable defibrillator, heart transplantation and cell therapy. Stem cell therapy is feasible and short term data indicates it is safe. However there are unresolved concerns on arrhythmias, restenosis and efficacy. At this point experts recommend that medium-sized randomized controlled trials, using surrogate endpoints, should be carried out to establish the efficacy and safety of this form of treatment.

Measurement of left ventricular dyssynchrony in patients with ischaemic cardiomyopathy: a comparison of real-time three-dimensional and tissue Doppler echocardiography

BACKGROUND

Real-time three-dimensional echocardiography (RT3DE) is an alternative modality to tissue Doppler imaging (TDI) for assessment of intraventricular dyssynchrony but its role is yet to be defined.

OBJECTIVES

To (1) compare RT3DE and TDI for assessment of intraventricular dyssynchrony; (2) determine whether the two techniques agreed regarding the magnitude of dyssynchrony and identification of the site of maximal mechanical delay; and (3) investigate the reason for disagreement.

PATIENTS

100 patients with ischaemic cardiomyopathy.

SETTING

Tertiary referral cardiac unit.

MAIN OUTCOME MEASURES

Dispersion in time interval from QRS onset to peak sustained systolic tissue velocity by TDI (SD-T(TV)) and to minimal systolic volume by RT3DE (SD-T(3D)) between 12 ventricular segments.

RESULTS

RT3DE image quality was adequate for measurement of SD-T3D in 77 (77%) patients. In the whole population, SD-T(TV) was 40 (20) ms and SD-T3D was 8.3% (3.4%). RT3DE identified a smaller proportion of patients as having significant dyssynchrony than TDI (49 (64%) patients vs 32 (42%) patients; p<0.01). The correlation between SD-T(TV) and SD-T3D was poor (r = 0.11, p = NS). There was concordance between TDI and RT3DE in identifying the site of maximal mechanical delay in 12 (16%) patients. Validating the two techniques with anatomical M-mode (AMM) as a parameter of radial timing revealed better agreement with RT3DE than with TDI (chi2 = 11.8, p = 0.001).

CONCLUSION

In patients with ischaemic cardiomyopathy, TDI and RT3DE show poor agreement for evaluating the magnitude of intraventricular dyssynchrony and the site of maximal mechanical delay. This may partly relate to their respective assessment of longitudinal versus radial timing.

Heart failure: metabolic derangements and therapeutic rationale

In the USA, over two-thirds of patients with heart failure (HF) are cared for by primary care practitioners exclusively. Significant progress has been made through basic science and clinical research focusing on the prevention of HF via control of known risk factors. There has also been a great deal of progress in both pharmacologic and nonpharmacologic management of the disease. These therapeutic interventions, however, continue to be underutilized, with seemingly inadequate translation of new evidence and updated guidelines (American College of Cardiology/American Heart Association, European Society of Cardiology, Canadian Cardiovascular Society, and Heart Failure Society of America updates in 2005-2006) into clinical practice. In this review, we discuss the pathophysiology of HF in addition to the metabolic derangements and therapeutic rationale surrounding current treatment options, with a particular focus on the interventions that have been shown and recommended in updated guidelines to prevent the disease or halt its progression.

Cardiac resynchronization therapy in clinical practice: need for electrical, mechanical, clinical and logistic synchronization

Considering the relatively short history of cardiac resynchronization therapy (CRT), the amount of available evidence of efficacy is impressive, and effectiveness studies are now required. Transfer of our experimentally gained knowledge into the real world raises issues that call for synchronization among the many specialists involved in chronic heart failure (CHF) management and CRT decision making. From an economic perspective, the demonstrated ability of CRT to reduce hospitalizations could help ease the burden on health systems derived from the growing incidence of CHF. Recent American College of Cardiology/American Heart Association guideline revisions should encourage a synchronized approach to rational deployment of CRT in selected patients. Nevertheless, current QRS criteria for CRT candidacy do not directly address the key issue of identification of patients with a pacing-correctable mechanical dyssynchrony (and in clinical trials, 25-30% of implanted patients did not respond to CRT). Echocardiography could become an important adjunct (or even an alternative) to QRS duration for patient selection; routine implementation would require use of straightforward, reproducible measurements, possibly obtainable on standard equipment. Echocardiography could also help optimize site location, although this would not eliminate lead placement problems. A series of issues remain open for investigation, including the potential of CRT in patients with atrial fibrillation, impact of devices with defibrillation ability, effects of electrical/pharmacological tailoring, need for confirmation that efficacy of CRT extends into the long term and possible use of CRT in mild CHF. Interdisciplinary synchronization in the various phases of CRT (screening, proposing, implementing, optimizing and monitoring) should eventually help develop a coordinated system for patient referral.

Cardiac resynchronization therapy or atrio-biventricular pacing—what should it be called?

Reduced cardiac efficiency caused by suboptimal synchronization of the heart's normal contraction might contribute to the development of or exacerbate heart failure. Conceptually and in practice cardiac dyssynchrony is complex. Recent studies have shown that atrio-biventricular pacing can improve cardiac synchrony in many patients and improve cardiac function, symptoms and exercise capacity, and reduce morbidity and mortality substantially. Randomized controlled trials, however, indicate that the severity of cardiac dyssynchrony, as conventionally measured, is a poor guide to treatment benefit and that correction of dyssynchrony accounts for only part of the benefit of atrio-biventricular pacing. Although some of the benefits of atrio-biventricular pacing might be mediated by cardiac resynchronization, much of the benefit could be mediated by mechanisms that are as yet unknown. Withholding atrio-biventricular pacing in patients who do not exhibit cardiac dyssynchrony on imaging but otherwise fulfil the entry criteria used in randomized controlled trials of this therapy could be unwise. Here, we examine the evidence that cardiac resynchronization is indeed the mechanism by which atrio-biventricular pacing exerts its effects.

Cardiac Resynchronization Treatment of Heart Failure

Cardiac resynchronization therapy (CRT) is well established as a treatment for patients with moderate to severe heart failure on optimal medical therapy. Early studies demonstrated improved functional capacity and evidence of reverse remodeling; more recently, CRT has been associated with a survival benefit in advanced heart failure both with and without a defibrillator. We review the eight landmark trials in CRT. To date, criteria have focused on electrical delay, but echocardiographic parameters emphasize the importance of mechanical delay or ventricular dyssynchrony. With the exponential rise in implants, new issues have emerged, such as optimal device programming, identifying appropriate candidates, and accounting for cases without clinical benefit from CRT.

[Resynchronization therapy of heart failure]

Heart failure has a high prevalence and it has a poor prognosis despite the advances in pharmacological treatment. Cardiac resynchronization therapy with biventricular pacemaker has a clinically proven efficacy in the treatment of heart failure with intraventricular dyssynchrony. Conventionally the therapy is indicated in severe drug refractory heart failure (NYHA III-IV) with optimal drug treatment, increased QRS duration (> or = 120 ms), echocardiographic parameters (left ventricular ejection fraction at most 35%). Implementation of new methods (tissue doppler echocardiography, CT, MRI, electroanatomical mapping) can help to select potentially responding patients. Individual optimization of therapy can be performed with non-invasive and invasive methods, the efficacy can be improved even in responding patients. Due to the outstanding efficiency widening the indications is a must. Currently, the efficacy is being investigated in mild heart failure and patients with narrow QRS. Several other questions (transvenous or surgical implantation, need of an implantable defibrillator) will be answered in future trials.

Usefulness of clinical, electrocardiographic, and echocardiographic parameters to detect cardiac asynchrony in patients with left ventricular dysfunction secondary to ischemic or nonischemic heart disease

OBJECTIVES

Specific evaluation using echocardiographic Doppler is superior to the measurement of the QRS complex to detect cardiac asynchrony. Nevertheless, no clinical, electrocardiographic, or echocardiographic parameters have been evaluated to obtain an accurate and easy-to-use marker of cardiac asynchrony in patients with depressed left ventricular (LV) ejection fraction. Our aim was to determine whether there is any marker of cardiac asynchrony in patients with LV systolic dysfunction that allows us to obviate the performance of a specific echocardiographic study before cardiac resynchronization therapy.

METHODS

In all, 316 consecutive patients with LV ejection fraction less than 40% were enrolled. Interventricular asynchrony was defined as an interventricular mechanical delay longer than 40 milliseconds. Intraventricular asynchrony was defined as the difference between time from Q wave to LV ejection end and the time from Q wave to the end of the systolic wave of the most delayed basal segment by Doppler tissue imaging greater than 50 milliseconds.

RESULTS

In all, 177 (56%) had ischemic and 139 (44%) had nonischemic heart disease. The logistic regression analysis showed that only the presence of left bundle branch block was an independent predictor of interventricular asynchrony despite the cause of the underlying disease (odds ratio and 95% confidence interval 7.2 [3.9-13.4], P < .001; 5.99 [2.7-13.2], P < .001; and 8.75 [3.2-23.8], P < .001 for the total population, ischemic and nonischemic groups, respectively). Nevertheless, none of the studied parameters was found as a predictor of intraventricular asynchrony.

CONCLUSIONS

The presence of left bundle branch block is a marker of interventricular asynchrony in patients with ventricular dysfunction despite the cause of the underlying cardiac disease. Nevertheless, intraventricular cardiac asynchrony cannot be detected using conventional parameters. A specific echocardiographic evaluation before cardiac resynchronization therapy must be performed in all these patients. Our aim was to determine whether there is any marker of cardiac asynchrony in patients with left ventricular systolic dysfunction that allows us to obviate the performance of a specific echocardiographic study before cardiac resynchronization therapy. Our results showed that only the presence of left bundle branch block was an independent predictor of interventricular asynchrony despite the cause of the underlying disease but none of the studied parameters was found as a predictor of intraventricular asynchrony.

Cardiac resynchronization therapy for chronic heart failure: why does it not always work?

Since coronary angiography and ventriculography are performed in all of these patients with LV dysfunction and symptoms of heart failure, it seems silly to waste the opportunity to study this technique and its value in identifying patients who will respond to CRT, at least in the immediate post-CRT state. The critical factors that may result in a successful long-term positive result of CRT in patients with optimal device programming and optimized medical therapy for heart failure are these: (1) Venous anatomy suitable for electrical stimulation of the LV free wall. (2) Viable myocardium in the septum and the LV free wall. (3) Adequate perfusion of the microcirculation in the distribution where the leads are being placed.

Cardiac resynchronization therapy: redefining the role of device therapy in heart failure

That cardiac dyssynchrony can contribute to a decline in cardiac efficiency has been recognized in one form or another for at least 50 years. Although revascularization and beta-blockers can improve cardiac synchrony, there was little interest in or awareness of this clinical entity until the advent of specific, highly effective therapy using atriobiventricular pacing, often described as cardiac resynchronization therapy. Over the last few years, significant advances in cardiac resynchronization therapy technology and the publication of large-scale clinical trials using cardiac resynchronization therapy devices in patients with heart failure have led to the widespread use of these devices. This review will briefly describe the complex nature of cardiac dyssynchrony, what is known about its epidemiology, the effects of cardiac resynchronization therapy, appropriate patient selection, practical aspects, such as implantation and monitoring, and some still unanswered questions.

Comparison of 1-year effects of left ventricular and biventricular pacing in patients with heart failure who have ventricular arrhythmias and left bundle-branch block: the Bi vs Left Ventricular Pacing: an International Pilot Evaluation on Heart Failure Patients with Ventricular Arrhythmias (BELIEVE) multicenter prospective randomized pilot study

BACKGROUND

Little is known on the chronic effects of left ventricular pacing (LV) in heart failure.

METHODS

Seventy-four patients with LBBB, QRS >130 milliseconds, New York Heart Association class (Bradley DJ, Bradley EA, Braughman KL, et al. Cardiac resynchronization and death from progressive heart failure: a meta-analysis of randomized controlled trials. JAMA 2003;289:730-40.) II, LV ejection fraction (LVEF) <35%, and a class I cardioverter/defibrillator indication were implanted with CRT-D devices and were randomized to either LV or biventricular (BiV) pacing. Response (defined as increases of >5 points increase of LVEF and/or > or = 10% 6-minute walking test [6MWT]) between LV and BiV pacing were compared in an attempt to define the number of patients needed to claim noninferiority of LV pacing. In addition, absolute change in LVEF at 12 months in heart failure patients treated with LV pacing was evaluated. The safety of LV pacing was assessed comparing the total number of ventricular arrhythmia episodes, of hospitalizations, and of deaths between the two pacing modes.

RESULTS

The percentage of responders was comparable for both groups (LV = 75%, BiV = 70%, P = .788); based on the 95% CI of the difference between the groups, 1100 patients would be needed to claim noninferiority of LV pacing (with a 5% CI lower limit). LV pacing induced siginificant LVEF increase (5.2%, P = .002). These results remained unchanged after performing adjustment analyses. There were no differences in the numbers of ventricular arrhythmias, hospitalizations, and death events between the 2 pacing modes.

CONCLUSIONS

At 12 months, percentage of responders to LV pacing was similar to BIV pacing. Furthermore, LV pacing achieved a significant increase of ejection fraction. LV pacing is both safe and feasible.

Left ventricular dyssynchrony in patients with heart failure: pathophysiology, diagnosis and treatment

The number of patients with chronic heart failure is increasing rapidly in the Western world. Despite the introduction of new pharmacologic therapies, the prognosis of these patients remains poor. Left ventricular (LV) dyssynchrony is a frequently observed feature in patients with heart failure, and is recognized as an important predictor of poor outcome if left untreated. The presence of LV dyssynchrony leads to inefficient LV contraction with a decreased cardiac output. Moreover, patients with LV dyssynchrony are at increased risk of adverse cardiac events. New therapeutic options targeted at restoring normal mechanical synchrony, such as cardiac resynchronization therapy, have been shown to improve clinical symptoms and prognosis in patients with heart failure. The beneficial effects of cardiac resynchronization therapy are predominantly mediated by this treatment's ability to reduce LV dyssynchrony. Given these results, adequate identification of LV dyssynchrony in patients with heart failure is of paramount importance. Several new imaging techniques are proving useful for diagnosis of LV dyssynchrony. In particular, advanced echocardiographic techniques (e.g. tissue Doppler imaging) and conductance catheter techniques are two accurate methods for quantification of LV dyssynchrony. In this review, we discuss the pathophysiology, diagnosis and treatment of LV dyssynchrony in patients with heart failure.

Differential change in left ventricular mass and regional wall thickness after cardiac resynchronization therapy for heart failure

AIMS

LV reverse remodelling has been shown to be a favourable response after cardiac resynchronization therapy (CRT) in many clinical trials. This study investigated whether left ventricular (LV) reverse remodelling after CRT has any structural benefit, which include the improvement of LV mass or regional wall thickness.

METHODS AND RESULTS

Fifty patients (66 +/- 11 years) receiving CRT were followed up for at least 3 months. Echocardiography with tissue Doppler imaging was performed serially before and at day 1 and 3 months after CRT. Although LV end-systolic volume (LVESV) was decreased at day 1 after CRT (141 +/- 74 vs. 129 +/- 71 cm(3), P < 0.001), further LV reverse remodelling was observed at 3 months (110 +/- 67 cm(3), P < 0.001 vs. day 1). LV ejection fraction increased at day 1 (26.5 +/- 9.3 vs. 28.5 +/- 9.1%, P < 0.005) and was further improved at 3 months (34.2 +/- 10.5%, P < 0.001 vs. day 1). However, reduction of LV mass (231 +/- 67 vs. 213 +/- 59 g, P < 0.001) and regional wall thickness was only observed at 3 months, but not at day 1. The improvement of LV mass correlated with the change in LVESV (r = 0.66, P < 0.001) and the baseline systolic asynchrony index (Ts-SD) (r = -0.52, P < 0.001). LV mass was only decreased significantly in responders of LV reverse remodelling (245 +/- 66 vs. 207 +/- 61 g, P < 0.001), but increased in non-responders (209 +/- 64 vs. 223 +/- 56 g, P = 0.02). Responders had significant decrease in thickness of all the four walls for -6 to -11% (all P < or =0.02), whereas non-responders had increased thickness in septal and lateral walls for +11% (both P < 0.05).

CONCLUSION

The acute reduction in LV volume after CRT is mediated by haemodynamic and geometric benefits without actual changes in LV mass. However, at 3-month follow-up, reduction in LV mass and regional wall thickness was demonstrated, which represents structural reverse remodelling. Such benefit was only observed in volumetric responders but was worsened in non-responders.

Clinical predictors and timing of New York Heart Association class improvement with cardiac resynchronization therapy in patients with advanced chronic heart failure: results from the Multicenter InSync Randomized Clinical Evaluation (MIRACLE) and Multicenter InSync ICD Randomized Clinical Evaluation (MIRACLE-ICD) trials

BACKGROUND

Based on current patient selection criteria, a significant proportion of recipients of cardiac resynchronization therapy (CRT) do not respond to treatment. The purpose of this analysis is to identify predictors and characterize the timing of response to CRT in patients with advanced heart failure.

METHODS

Patients randomized to receive CRT in the MIRACLE and MIRACLE-ICD trials, designed to assess the benefit of CRT compared with standard medical therapy in patients with advanced heart failure, left ventricular ejection fraction <0.35, and QRS > or =130 milliseconds, were included for this analysis. Patients with an improvement of > or =1 New York Heart Association (NYHA) class from baseline to the 6-month follow-up were considered responders and those who had no change or worse NYHA class or died were classified as nonresponders. Responders were subdivided into early (within 1-3 months) and late (6 months).

RESULTS

One hundred forty-three (64%) of 224 and 190 (61%) of 313 patients in the MIRACLE and MIRACLE-ICD trials, respectively, responded to therapy, with 81 (57%) of 143 and 100 (53%) of 190 responding early. Several but differing factors predicted CRT response and timing in the two trials with a high sensitivity (89%-90%) but, owing to a low specificity (31%-49%), a modest predictive accuracy (66%-75%).

CONCLUSIONS

Based on improvement of > or =1 NYHA class, less than two thirds of patients enrolled in the MIRACLE or MIRACLE-ICD trials responded to CRT, with just more than half responding within the first month. Several factors predicted CRT response and timing, but given their modest predictive accuracy, comparable for both studies, additional methods for selecting candidates most likely to benefit from CRT are needed.

Selecting patients for cardiac resynchronization therapy: electrical or mechanical dyssynchrony?

Cardiac resynchronization therapy (CRT) markedly reduces morbidity and mortality in patients with heart failure and prolonged QRS duration. Landmark trials have included over 4000 patients based on their electrocardiogram. A few small, observational, non-randomized, single centre studies of short duration have suggested that echocardiographic measurement of mechanical dyssynchrony may better identify patients likely to benefit from CRT. We objectively review the meaning and measurement of electrical and mechanical dyssynchrony, the strengths and weaknesses of echocardiographic indices of dyssynchrony, and the controversial issue of predicting response to treatment. We conclude that proposals to alter current guidelines for patient selection, and include echocardiography, are misguided. Echocardiographic assessment will only become credible and applicable to clinical practice once used to select patients for large prospective randomized trials which show an improvement in clinical outcome.

Cardiac resynchronization therapy: Part 1--issues before device implantation

Cardiac resynchronization therapy (CRT) has been used extensively over the last years in the therapeutic management of patients with end-stage heart failure. Data from 4,017 patients have been published in eight large, randomized trials on CRT. Improvement in clinical end points (symptoms, exercise capacity, quality of life) and echocardiographic end points (systolic function, left ventricular size, mitral regurgitation) have been reported after CRT, with a reduction in hospitalizations for decompensated heart failure and an improvement in survival. However, individual results vary, and 20% to 30% of patients do not respond to CRT. At present, the selection criteria include severe heart failure (New York Heart Association functional class III or IV), left ventricular ejection fraction <35%, and wide QRS complex (>120 ms). Assessment of inter- and particularly intraventricular dyssynchrony as provided by echocardiography (predominantly tissue Doppler imaging techniques) may allow improved identification of potential responders to CRT. In this review a summary of the clinical and echocardiographic results of the large, randomized trials is provided, followed by an extensive overview on the currently available echocardiographic techniques for assessment of LV dyssynchrony. In addition, the value of LV scar tissue and venous anatomy for the selection of potential candidates for CRT are discussed.

Effects of cardiac resynchronization therapy on disease progression in chronic heart failure

Despite the alleviation of symptoms and longer survival conferred by pharmacological management of chronic congestive heart failure (CHF), this progressive syndrome remains associated with high morbidity and premature death. A new treatment of CHF should ideally alleviate symptoms, improve functional capacity, decrease mortality, and slow or reverse its progression without adding risks for the patient that outweighs the benefits. Growing evidence indicates that devices implanted to resynchronize ventricular contraction are a beneficial adjunct in the treatment of CHF. This review discusses the remodelling process, and its clinical and prognostic significance. We also discuss the impact of CRT, on remodelling and disease progression with a particular focus on patients with asymptomatic or mild heart failure (NYHA Class I-II).

Progress in Cardiovascular Disease: Technical Considerations in Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) has been shown to improve symptoms, ventricular function, and survival in patients with left ventricular systolic dysfunction and ventricular conduction delay. Patients with moderate to severe drug-refractory heart failure symptoms along with ventricular dyssynchrony, manifested as prolongation of the QRS duration on the surface electrocardiogram, benefit from CRT. Owing to the growing awareness and application of CRT, a large number of patients have been identified as candidates for this therapy, making it necessary for clinicians involved in the care of such patients to be adequately knowledgeable of various aspects of CRT implementation. In particular, clinicians involved in the care of these patients must be aware of the practical considerations in preparing patients for the implantation procedure, careful surveillance for early or late procedure-related complications, and knowledge of the fundamental device features so as to tailor therapeutic and programming techniques to improve long-term response to CRT. This review addresses the technical considerations of the implantation procedure and device function with emphasis on the initial and long-term programming to ensure optimal delivery of CRT.

The problem of non-response to cardiac resynchronization therapy

PURPOSE OF REVIEW

Cardiac resynchronization therapy improves quality of life, exercise performance, left ventricular ejection fraction, and reduces heart failure hospitalizations and mortality in patients with New York Heart Association class III or IV congestive heart failure and intraventricular conduction delay. A number of key clinical research questions remain, perhaps most importantly the issue of why apparently suitable patients do not respond to cardiac resynchronization therapy. These issues are also relevant to patients who do respond to cardiac resynchronization therapy as potentially their response might be further increased. This article will review the data regarding the frequency of the problem of non-response to cardiac resynchronization therapy and then discuss the postulated reasons and potential solutions.

RECENT FINDINGS

Rates of non-response to cardiac resynchronization therapy are often quoted as 20-30%, but a critical analysis of the data would suggest the true non-responder rate can be estimated as perhaps 40-50%. The data indicate that on a population basis non-response is multi-factorial and the extent of mechanical dyssynchrony, left ventricular pacing site and cause of congestive heart failure are likely to be important. Ongoing research is exploring the utility of various techniques for quantifying mechanical dyssynchrony and the potential benefits of targeted left ventricular lead placement and post-implant optimization.

SUMMARY

Cardiac resynchronization therapy is a major breakthrough in treatment for advanced congestive heart failure patients. There is substantial rate of non-response to this therapy, however, and research is exploring various ways to increase the response to the technique.

La insuficiencia cardíaca en el año 2005

This article is a review of developments reported in the field of heart failure in the last year. It covers advances in epidemiology, pathophysiology and therapy, including cardiac resynchronization therapy and heart transplantation. Today, management of heart failure is complex. It depends on the participation of numerous health professionals under the guidance of a cardiologist. The increasing prevalence of heart failure means that continuing research is mandatory.

Imaging techniques in cardiac electrophysiology

Modern cardiac electrophysiology procedures include catheter-based arrhythmia ablation and transvenous device implantation, which are highly dependent on accurate, real-time cardiac imaging. With the realization that anatomic structures are critical to successful electrophysiologic procedures, accurately defining a patient's cardiac anatomy has become more important. Fluoroscopy allows for 2D imaging of cardiac structures in real-time, and is used to guide catheter and lead placement, but does not allow for visualization of soft tissues. Intracardiac echocardiography allows for both direct visualization of anatomic structures within the heart and real-time imaging during catheter placement. Despite advances in intracardiac echocardiography catheters that allow for larger windows, the ability to accurately delineate anatomic structures depends on the patient's anatomy and operator experience. Neither of these techniques allows for electrical mapping of the heart; however, both anatomic and electrical intracardiac mapping can be achieved with advanced mapping systems. These systems allow for real-time catheter localization, help elucidate cardiac anatomy, evaluate electrical activation during arrhythmias and guide catheter placement for deliverance of radiofrequency current. More recently, 3D cardiac computed tomography has been used to accurately define intracardiac anatomy; however, catheter tracking and electrical mapping cannot be performed by computed tomography. Mapping systems are now being merged with computed tomography images to produce an accurate anatomic and electrical map of the heart to guide catheter ablations. The objective of this paper is to describe the current imaging and mapping techniques used in electrophysiologic procedures.

Cardiac resynchronization therapy: the MGH experience

Cardiac resynchronization therapy (CRT) has gained acceptance as a useful form of device therapy for patients with refractory congestive heart failure. Despite recent technical advances, a significant number of patients continue to remain unresponsive to this form of therapy. This article provides an overview of CRT, highlights several unresolved issues and describes ongoing research efforts to address some of these important questions.