Cardiac Resynchronization Therapy in Mild Heart Failure: A Review of the REVERSE and MADIT-CRT Trials

Cardiac resynchronization therapy has become part of the treatment strategy for advanced, symptomatic heart failure, but newly published trials show that more patients than previously realized may benefit from this therapy, including those with mild heart failure symptoms. The REVERSE and MADIT-CRT trials showed that cardiac resynchronization therapy reduces risk of hospitalization for heart failure and leads to beneficial reverse remodeling of the left ventricle in mild heart failure, especially in patients with prolonged QRS complexes. Ongoing studies aim to expand the indications for this therapy even further, including in patients with normal ejection fractions and a need for frequent ventricular pacing. The current body of evidence favors cardiac resynchronization therapy in patients with a depressed ejection fraction and prolonged QRS, even with minimal or no heart failure symptoms.     

Six minute corridor walk test as an outcome measure for the assessment of treatment in randomized, blinded intervention trials of chronic heart failure: a systematic review.

AIMS: The 6 min walk test (6MWT) is commonly used in clinical trials to assess treatments for heart failure, but its ability to distinguish between effective and ineffective treatments is questionable. The aim of this study is to investigate, using a systematic literature review, the utility of the 6MWT as a measure of the effectiveness of treatment in randomized controlled trials of heart failure. METHODS AND RESULTS: A literature search was performed using Medline, EMBASE, CINAHL, and Biological abstracts for randomized controlled trials that measured 6MWT between 1988 and 31 May 2004. A significant increase in 6MWT distance was observed in only 9 of 47 randomized controlled trials of pharmacological therapy; 2 of 6 trials of ACE-inhibitors; 3 of 17 trials of beta-blockers; 1 of 4 trials of digoxin; one trial of ibopamine; one trial of l-arginine; one trial of beriberine; and one trial showed superiority of captopril over flosequinan. A significant increase in 6MWT was observed in four out of six placebo-controlled trials of cardiac resynchronization. Smaller pharmacological trials with fewer centres were more likely to be positive; six out of nine positive pharmacological trials had four or less participating centres, raising the possibility of publication bias. Pharmacological trials including patients with more severe heart failure were more likely to show a significant improvement with therapy than trials of milder heart failure. Five out of seven pharmacological trials that reported an improvement in symptoms also reported an improvement in 6MWT distance. Of 30 pharmacological trials, 29 that reported no improvement in symptoms also reported no improvement in 6MWT. Using mean values in these trials, the age of patients appeared a more important determinant of 6MWT distance than New York Heart Association classification. CONCLUSION: The 6MWT has not yet been proven to be a robust test for the identification of effective pharmacological interventions although it appears useful for the assessment of cardiac resynchronization therapy. The results of the 6MWT were concordant with changes in symptoms, suggesting that it may be used as supportive evidence for symptom benefit. The test may be of greater value in patients with more advanced heart failure, where it may function as a maximal exercise test.     

Left ventricular assist devices: an alternative to medical therapy for end-stage heart failure

Although aggressive medical therapy and ultimately cardiac transplantation have long been the therapeutic mainstays for patients with end-stage heart failure, the left ventricular assist device (LVAD), which was originally used clinically as a bridge to transplantation, may also be used as destination therapy. LVAD therapy for selected patients has been shown in the REMATCH trial to be superior to medical therapy in ameliorating symptoms and improving outcome in patients with terminal heart failure. LVAD therapy has also proved useful in improving native heart function by neuroendocrine modulation and reverse remodeling. Furthermore, current evidence suggests that when LVAD therapy is utilized to improve ventricular function, it may be further enhanced when combined with aggressive medical therapy.     

Cardiac resynchronization therapy in patients with a narrow QRS

Although cardiac resynchronization therapy (CRT) is indicated in patients with moderate to severe heart failure with a wide QRS complex (> 120 ms), current guidelines exclude many heart failure patients with a narrow QRS. Detecting mechanical dyssynchrony on echocardiography has become a promising tool in selecting patients with a narrow QRS who may respond to CRT. Several small single-center studies identified patients with a narrow QRS (using echocardiography-based dyssynchrony criteria) who responded favorably to CRT; however, the results of two recent pilot studies remain elusive. The results of the RethinQ study do not provide necessary evidence for making clinical treatment decisions in this population. The lack of definitive evidence is the strongest rationale for conducting an adequately powered, long-term, end point-driven, randomized controlled trial to investigate whether CRT therapy can improve morbidity and mortality outcomes in heart failure patients with a narrow QRS. Such a trial, the EchoCRT trial, has recently been launched.     

Outcomes of elderly heart failure recipients of ICD and CRT

Implantable cardioverter defibrillator (ICD) therapy has been established as a highly effective method for primary and secondary prevention of sudden cardiac death in heart failure patients. In addition, cardiac resynchronization therapy (CRT) with and without defibrillator back-up improves symptoms, exercise capacity and prognosis in selected patients with advanced heart failure and intraventricular conduction delay. Unfortunately, mean patient age in ICD- and CRT-intervention trials was only 60 to 65 years with few patients being older than 75 years. None of these trials separately studied an elderly heart failure population. This review summarizes the available scientific evidence for the use of ICDs and CRT devices in elderly heart failure patients based on subgroup analyses of prospective randomized ICD- and CRT-intervention trials, and based on published cohort studies.     

Clinical cardiac regenerative studies in children

Although the incidence of pediatric heart failure is low, the mortality is relatively high, with severe clinical symptoms requiring repeated hospitalization or intensive care treatment in the surviving patients. Cardiac biopsy specimens have revealed a higher number of resident human cardiac progenitor cells, with greater proliferation and differentiation capacity, in the neonatal period as compared with adults, demonstrating the regeneration potential of the young heart, with rising interest in cardiac regeneration therapy in critically ill pediatric patients. We review here the available literature data, searching the MEDLINE, Google Scholar and EMBASE database for completed, and www.clinicaltrials.gov homepage for ongoing studies involving pediatric cardiac regeneration reports. Because of difficulties conducting randomized blinded clinical trials in pediatric patients, mostly case reports or cohort studies with a limited number of individuals have been published in the field of pediatric regenerative cardiology. The majority of pediatric autologous cell transplantations into the cardiac tissue have been performed in critically ill children with severe or terminal heart failure. Congenital heart disease, myocarditis, and idiopathic hypertrophic or dilated cardiomyopathy leading to congestive heart failure are some possible areas of interest for pediatric cardiac regeneration therapy. Autologous bone marrow mononuclear cells, progenitor cells, or cardiospheres have been applied either intracoronary or percutaneously intramyocardially in severely ill children, leading to a reported clinical benefit of cell-based cardiac therapies. In conclusion, compassionate use of autologous stem cell administration has led to at least short-term improvement in heart function and clinical stability in the majority of the critically ill pediatric patients.     

Preclinical and clinical assessment of the safety and potential efficacy of thalidomide in heart failure

BACKGROUND: Inflammatory mediators, especially tumor necrosis factor (TNF), have been implicated in heart failure (HF). Thalidomide has anti-inflammatory properties and selectively inhibits TNF. Thus far, thalidomide or thalidomide analogues have not been evaluated in patients with heart failure. METHODS: Thalidomide was assessed in preclinical and clinical studies. First, isolated cardiac myocytes were pretreated with thalidomide or thalidomide analogues, and TNF production was assessed after lipopolysaccharide (LPS) provocation. Second, to determine the safety and potential efficacy of thalidomide, an open-label dose escalation safety study was conducted in seven patients with advanced heart failure. RESULTS: Thalidomide and thalidomide analogues inhibited LPS-induced TNF biosynthesis in cardiac myocytes in a dose-dependent manner. Thalidomide analogues had a greater inhibitory effect on TNF production than did thalidomide. In patients with advanced HF, thalidomide was safe and potentially effective when used at lower doses. However, dose-limiting toxicity was observed in two patients. There was a significant increase in the 6-minute walk distance and a trend toward improvement in left ventricular ejection fraction and quality of life after 12 weeks of maintenance therapy with thalidomide. CONCLUSIONS: Taken together these results suggest that thalidomide or its derivatives may be useful in selected patients with HF. This potential needs to be studied in larger clinical trials.     

Treatment with B-Type Natriuretic Peptide for Chronic Decompensated Heart Failure: Insights Learned from the Follow-Up Serial Infusion of Nesiritide (FUSION) Trial

Several evidence-based treatment regimens are modestly effective in patients with moderately severe to severe heart failure, but truly effective therapies that improve symptoms, reduce hospitalizations, and extend meaningful survival do not exist for these patients. Only ventricular replacement therapy, with either heart transplantation or left ventricular assist devices, has been shown to significantly improve outcomes. Nesiritide, a recombinant B-type natriuretic peptide, is associated with significant reductions in filling pressure, with corresponding relief of symptoms, and diminished neurohormonal levels and has no inotropic effects and no evidence of proarrhythmia when given to patients with decompensated acute heart failure. Results of the Follow-Up Serial Infusion of Nesiritide (FUSION) trial suggest that a regimen incorporating nesiritide can be accomplished with a reasonable assurance of safety and tolerability; pre-study concerns regarding hypotension were not realized. A qualified look at outcomes data within FUSION I suggests that further study of this paradigm is reasonable, especially if the studied patient population includes patients with a low left ventricular ejection fraction and New York Heart Association (NYHA) class III disease with renal insufficiency, or patients with low left ventricular ejection fraction and NYHA class IV heart failure. Therefore, FUSION II, a double-blind, placebo-controlled trial, will randomly assign approximately 900 such patients to treatment with usual care plus nesiritide or usual care plus placebo and will use mortality/cardiorenal hospitalization as a composite end point. If positive data emerge from FUSION II that either confirm or strengthen the data in FUSION I, a new therapeutic option may be available for patients with chronic decompensated heart failure.     

Treatment with B-type natriuretic peptide for chronic decompensated heart failure: insights learned from the follow-up serial infusion of nesiritide (FUSION) trial

Several evidence-based treatment regimens are modestly effective in patients with moderately severe to severe heart failure, but truly effective therapies that improve symptoms, reduce hospitalizations, and extend meaningful survival do not exist for these patients. Only ventricular replacement therapy, with either heart transplantation or left ventricular assist devices, has been shown to significantly improve outcomes. Nesiritide, a recombinant B-type natriuretic peptide, is associated with significant reductions in filling pressure, with corresponding relief of symptoms, and diminished neurohormonal levels and has no inotropic effects and no evidence of proarrhythmia when given to patients with decompensated acute heart failure. Results of the Follow-Up Serial Infusion of Nesiritide (FUSION) trial suggest that a regimen incorporating nesiritide can be accomplished with a reasonable assurance of safety and tolerability; pre-study concerns regarding hypotension were not realized. A qualified look at outcomes data within FUSION I suggests that further study of this paradigm is reasonable, especially if the studied patient population includes patients with a low left ventricular ejection fraction and New York Heart Association (NYHA) class III disease with renal insufficiency, or patients with low left ventricular ejection fraction and NYHA class IV heart failure. Therefore, FUSION II, a double-blind, placebo-controlled trial, will randomly assign approximately 900 such patients to treatment with usual care plus nesiritide or usual care plus placebo and will use mortality/cardiorenal hospitalization as a composite end point. If positive data emerge from FUSION II that either confirm or strengthen the data in FUSION I, a new therapeutic option may be available for patients with chronic decompensated heart failure.     

Lipid management beyond the guidelines

The 2018 AHA/ACC cholesterol guideline builds on the 2013 ACC/AHA cholesterol guideline statin recommendations to provide more detailed recommendations for the use of nonstatin therapy risk stratification for primary prevention statin use. New information has become available after the development of the 2018 AHA/ACC cholesterol guideline that can further inform clinical practice. Proprotein convertase subtilisin kexin type-9 (PCSK9) monoclonal antibodies are now a reasonable or even good value following over 60% reductions in their acquisition price, and the identification of high risk patient groups most likely to benefit from further low-density lipoprotein cholesterol (LDL-C) lowering. Meta-analyses and clinical trial data now show that patients with LDL-C ≥ 100 mg/dl are more likely to experience progressively greater reductions in the risk of cardiovascular and total mortality and coronary heart disease events for progressively higher LDL-C levels. Icosapent ethyl, a highly concentrated form of modified EPA has been shown to reduce cardiovascular events in high risk patients with moderate hypertriglyceridemia on statin therapy. Comparisons with other statin guidelines revealed that statin initiation for those with ≥7.5% 10-year atherosclerotic cardiovascular disease (ASCVD) risk is the most effective strategy for reducing the most ASCVD events for the proportion of the population treated. Data from younger populations finally became available for coronary artery calcium (CAC) scoring (mean age of 51 years) which confirmed the value of CAC > 0 for identifying individuals at increased ASCVD risk most likely to benefit from statin initiation. This analysis also found that statins could keep CAC = 0 in those with risk factors. Epidemiologic pooling studies now clearly show that LDL-C and non-high-density lipoprotein cholesterol levels in young adulthood confer excess risk for ASCVD later in life. Accumulating data support earlier risk factor intervention trials as the next research priority.     

Statin therapy is associated with lower mortality among patients with severe heart failure

Experimental considerations suggest both potential harm and benefit from statin therapy in patients with severe heart failure. However, relations of statin therapy with clinical outcomes in severe heart failure are not well established. Using data from the Prospective Randomized Amlodipine Survival Evaluation (PRAISE) trial, we evaluated associations of statin therapy with total mortality among 1,153 patients with severe heart failure (ejection fraction <30% and New York Heart Association class IIIB or IV symptoms) of ischemic and nonischemic etiologies. Statin therapy was administered to 134 patients (12%) during the study period. Over a 1.3-year mean follow-up, there were 413 deaths (29 deaths/100 person-years). Adjusting for age, gender, diabetes, smoking, heart failure etiology, ejection fraction, and New York Heart Association class, statin therapy was associated with a 62% lower risk of death (hazard ratio 0.38, 95% confidence interval 0.23 to 0.65), or 1 fewer death/5 patients taking statin therapy for 1 year. This association was not greatly altered by additional adjustment for a variety of other patient characteristics, including serum cholesterol levels. After propensity score analyses, statin therapy was still associated with a 48% lower risk of death (hazard ratio 0.52, 95% confidence interval 0.30 to 0.89). Although this observational study does not prove causality, further investigation of potential benefits of statins in patients with severe heart failure appears warranted.     

Clinical Trials Update from the European Society of Cardiology Congress in Vienna, 2007: PROSPECT,EVEREST, ARISE,ALOFT, FINESSE,Prague-8, CARESS in MI and ACUITY

The Clinical Trials described in this article were presented at the Hotline and Clinical Trial Update Sessions of the European Society of Cardiology Congress held in September 2007 in Vienna, Austria. The sessions chosen for this article represent the scope of interest of Cardiovascular Drugs and Therapy. The presentations should be considered preliminary, as further analyses could alter the final publication of the results of these studies. PROSPECT evaluated echocardiographic criteria for optimal selection of patients with moderate to severe heart failure who may benefit from cardiac resynchronisation therapy, however concluded that no single echocardiographic measure can be recommended. EVEREST found that tolvaptan, a vasopressin V₂ antagonist, resulted in early weight reduction and improvement of dyspnoea in patients with acute heart failure, but lacked long term improvement. In ARISE, the anti-oxidant succinobucal did not affect the primary outcome in high risk cardiovascular patients, but improved the combination of cardiovascular death, myocardial infarction and stroke, and diabetic control in diabetics. ALOFT showed that the addition of the renin inhibitor aliskiren to an ACE inhibitor or ARB and a beta-blocker leads to favourable effects on neurohormonal actions in heart failure. FINESSE markedly improved coronary patency before PCI with half-dose reteplase/abciximab in STEMI patients, however without significantly improving short-term outcome. The Prague-8 Study evaluated whether routine clopidogrel administered >6 h pre-angiography would be a safe way to achieve therapeutic drug levels in case a follow-up intervention would be considered immediately, but appeared not justified because of bleeding complications. CARESS in MI showed that high risk patients with evolving STEMI who undergo thrombolytic therapy should undergo PCI early after the thrombolysis. Finally, the ACUITY trial found that in moderate or high risk Non ST elevation ACS patients triaged to PCI, coronary artery bypass graft (CABG) surgery, or medical management, bivalirudin, with or without associated GPIIb/IIIa inhibitor therapy, resulted in a marked reduction of bleeding at 30 days whilst preserving the ischemic and mortality benefit at 1 year follow up.     

Endothelin-1 concentrations in pericardial fluid are more elevated in patients with ischemic heart disease than in patients with nonischemic heart disease

There is epidemiologic evidence that the prognosis of patients with nonischemic heart failure is better than that for patients with ischemic heart failure. In addition, studies have revealed that patients with ischemic heart failure show a poorer response to medical therapy. However, the pathophysiologic difference between ischemic and nonischemic heart disease is unclear. To clarify this point, we measured atrial natriuretic peptide, brain natriuretic peptide, angiotensin II, endothelin (ET)-1. interleukin-1beta interleukin-6. tumor necrosis factor (TNF)-alpha soluble TNF receptor I, and soluble TNF receptor II concentrations in plasma and pericardial fluid in patients with ischemic or nonischemic heart disease undergoing cardiac surgery. The pericardial ET-1 concentration in patients with ischemic heart disease was statistically greater than that in patients with nonischemic heart disease (about 1.5-fold), although no difference was found in the plasma ET-1 concentration. These findings suggest that the production and secretion of ET-1 from the myocardium in patients with ischemic heart disease are augmented to a greater extent than in patients with nonischemic heart disease. This result may lead to a greater understanding of the pathophysiology of ischemic heart disease.     

Clinical trials update from the Heart Failure Society of America: EMOTE, HERB-CHF, BEST genetic sub-study and RHYTHM-ICD

This article summarises key presentations relevant to the pathophysiology, prevention or treatment of heart failure, from the Heart Failure Society of America annual meeting held in Toronto, Canada. Data from the EnoxiMone in intravenous inOTropE-dependent subjects (EMOTE) study suggest that the oral PDE-3 inhibitor enoximone may be effective for weaning severe heart failure patients from intravenous inotropic therapy. Hawthorn Extract Randomised Blinded Trial in CHF (HERB-CHF) failed to show a benefit of hawthorn extract added to conventional heart failure therapy. A genetic sub-group analysis of the Blocker Evaluation of Survival Trial (BEST) study showed that bucindolol reduced mortality and hospitalisations in patients who were homozygous for the Arg389 variant of the beta(1) adrenoceptor. In the Resynchronisation Hemodynamic Treatment for Heart Failure Management (RHYTHM-ICD) study, patients randomised to cardiac resynchronisation therapy (CRT) showed an improvement in symptoms and functional capacity compared to the control group.     

Clinical trials update: Highlights of the Scientific Sessions of Heart Failure 2001, a meeting of the Working Group on Heart Failure of the European Society of Cardiology. CONTAK-CD, CHRISTMAS, OPTIME-CHF

This article continues a series of reports summarising recent research developments pertinent to the topic of heart failure. This is a summary of presentations made at Scientific Sessions of Heart Failure 2001, a meeting of the Working Group on Heart Failure of the European Society of Cardiology. Clinical studies of particular interest to people caring for patients with heart failure include CONTAK-CD, CHRISTMAS and further updates on OPTIME-CHF. A brief review of the current status of cardiac resynchronisation therapy is included.     

Tumor necrosis factor-a in the failing human heart: Does it play a role in disease progression?

Summary An increasing body of clinical and experimental evidence suggesting that TNF^! may play a pathogenetic role in failing hearts continues to accumulate. Perhaps the most direct evidence for the role of TNF^! in heart failure will come from the analysis of the phase I study in which a soluble recombinant human TNF receptor: Fc fusion protein was utilized in patients with moderate to severe heart failure Enrollment in that trial was recently completed; the results will soon be available for analysis. But perhaps more importantly, the knowledge gained from studying the role of TNF^! in cardiac function draws attention to a series of molecules previously unrecognized as potential mediators in the pathogenesis of heart failure. Various cytokines and TNF^!, in particular, represent new targets for therapeutic intervention in patients with heart failure.     

Effects of enalapril in heart failure: a double blind study of effects on exercise performance,renal function,hormones, and metabolic state.

Several studies have shown symptomatic and haemodynamic improvement after the introduction of angiotensin converting enzyme inhibitors in patients with heart failure treated with diuretics. The concomitant long term effects of the new orally effective long acting angiotensin converting enzyme inhibitor, enalapril, on symptoms, exercise performance, cardiac function, arrhythmias, hormones, electrolytes, body composition, and renal function have been further assessed in a placebo controlled double blind cross over trial with treatment periods of eight weeks. Twenty patients with New York Heart Association functional class II to IV heart failure who were clinically stable on digoxin and diuretic therapy were studied. Apart from the introduction of enalapril, regular treatment was not changed over the study period; no order or period effects were noted. Enalapril treatment significantly improved functional class, symptom score for breathlessness, and exercise tolerance. Systolic blood pressure was significantly lower on enalapril treatment. Echocardiographic assessment indicated a reduction in left ventricular dimensions and an improvement in systolic time intervals. In response to enalapril, the plasma concentration of angiotensin II was reduced and that of active renin rose; plasma concentrations of aldosterone, vasopressin, and noradrenaline fell. There were significant increases in serum potassium and serum magnesium on enalapril. Glomerular filtration rate measured both by isotopic techniques and by creatinine clearance declined on enalapril while serum urea and creatinine rose and effective renal plasma flow increased. Body weight and total body sodium were unchanged indicating that there was no overall diuresis. There was a statistically insignificant rise in total body potassium, though the increase was related directly to pretreatment plasma renin (r = 0.5). On enalapril the improvement in symptoms, exercise performance, fall in plasma noradrenaline, and rise in serum potassium coincided with a decline in the frequency of ventricular extrasystoles recorded during ambulatory monitoring. Adverse effects were few. In patients with heart failure, enalapril had a beneficial effect on symptoms and functional capacity. The decline in glomerular filtration rate on enalapril may not be beneficial in early heart failure.     

Effects of enalapril in heart failure: a double blind study of effects on exercise performance, renal function, hormones, and metabolic state

Several studies have shown symptomatic and haemodynamic improvement after the introduction of angiotensin converting enzyme inhibitors in patients with heart failure treated with diuretics. The concomitant long term effects of the new orally effective long acting angiotensin converting enzyme inhibitor, enalapril, on symptoms, exercise performance, cardiac function, arrhythmias, hormones, electrolytes, body composition, and renal function have been further assessed in a placebo controlled double blind cross over trial with treatment periods of eight weeks. Twenty patients with New York Heart Association functional class II to IV heart failure who were clinically stable on digoxin and diuretic therapy were studied. Apart from the introduction of enalapril, regular treatment was not changed over the study period; no order or period effects were noted. Enalapril treatment significantly improved functional class, symptom score for breathlessness, and exercise tolerance. Systolic blood pressure was significantly lower on enalapril treatment. Echocardiographic assessment indicated a reduction in left ventricular dimensions and an improvement in systolic time intervals. In response to enalapril, the plasma concentration of angiotensin II was reduced and that of active renin rose; plasma concentrations of aldosterone, vasopressin, and noradrenaline fell. There were significant increases in serum potassium and serum magnesium on enalapril. Glomerular filtration rate measured both by isotopic techniques and by creatinine clearance declined on enalapril while serum urea and creatinine rose and effective renal plasma flow increased. Body weight and total body sodium were unchanged indicating that there was no overall diuresis. There was a statistically insignificant rise in total body potassium, though the increase was related directly to pretreatment plasma renin (r = 0.5). On enalapril the improvement in symptoms, exercise performance, fall in plasma noradrenaline, and rise in serum potassium coincided with a decline in the frequency of ventricular extrasystoles recorded during ambulatory monitoring. Adverse effects were few. In patients with heart failure, enalapril had a beneficial effect on symptoms and functional capacity. The decline in glomerular filtration rate on enalapril may not be beneficial in early heart failure.     

Longer-term effects of cardiac resynchronization therapy on mortality in heart failure [the CArdiac REsynchronization-Heart Failure (CARE-HF) trial extension phase].

AIMS: The CArdiac REsynchronization-Heart Failure study randomized patients with left ventricular ejection fraction < or =35%, markers of cardiac dyssynchrony, and persistent moderate or severe symptoms of heart failure despite pharmacological therapy, to implantation of a cardiac resynchronization therapy (CRT) device or not. The main study observed substantial benefits on morbidity and mortality during a mean follow-up of 29.4 months [median 29.6, interquartile range (IQR) 23.6-34.6]. Prior to study closure, an extension phase lasting a further 8 months (allowing time for data analysis and presentation) was declared during which cross-over was discouraged. METHODS AND RESULTS: This was an extension of the already reported open-label randomized trial described above. The primary outcome of the extension phase was all-cause mortality from the time of randomization to completion of the extension phase. The secondary outcome was mode of death. The mean follow-up was 37.4 months (median 37.6, IQR 31.5-42.5, range 26.1-52.6 months). There were 154 deaths (38.1%) in 404 patients assigned to medical therapy and 101 deaths (24.7%) in 409 patients assigned to CRT (hazard ratio 0.60, 95% CI 0.47-0.77, P<0.0001) without evidence of heterogeneity in pre-specified subgroups. A reduction in the risk of death due to heart failure (64 vs. 38 deaths; hazard ratio 0.55, 95% CI 0.37-0.82, P=0.003) and sudden death was observed (55 vs. 32; hazard ratio 0.54, 95% CI 0.35-0.84, P=0.005). CONCLUSION: The benefits of CRT observed in the main trial persist or increase with longer follow-up. Reduction in mortality was due to fewer deaths both from worsening heart failure and from sudden death.