Covariate Adjustment in Heart Failure Randomized Controlled Clinical Trials: A Case Analysis of the HF-ACTION Trial

Greater Pain Severity Is Associated with Worse Outcomes in Patients with Heart Failure

We examined the relationship between pain severity and outcomes in patients with heart failure with reduced ejection fraction (HFrEF) in the HF-ACTION randomized controlled trial. Trends of health-related quality of life (HRQoL) measures grouped by patients' self-reported baseline bodily pain severity were compared using correlation tests, and the association between pain severity and clinical outcomes (including a primary composite endpoint of all-cause mortality and all-cause hospitalization) was assessed using multivariable adjusted analyses. Of the 2310 patients, 22.9% reported no pain, 45.8% very mild/mild, 24.9% moderate, and 6.4% severe/very severe. Greater pain severity was associated with worse HRQoL measures (EuroQoL-5D-3L and Kansas City Cardiomyopathy Questionnaire; both p < 0.0001). Compared to those reporting no pain, patients reporting severe/very severe pain had greater risk for the primary endpoint (adjusted hazard ratio 1.42, 95% confidence interval 1.11-1.83, p = 0.01). In patients with HFrEF, greater pain severity was associated with worse HRQoL and clinical outcomes. Trial Registration: NCT00047437.

Impact of baseline covariate imbalance on bias in treatment effect estimation in cluster randomized trials: Race as an example

Individual-level baseline covariate imbalance could happen more frequently in cluster randomized trials, and may influence the observed treatment effect. Using computer and real-data simulations, this paper quantifies the extent and impact of covariate imbalance on the estimated treatment effect for both continuous and binary outcomes, and relates it to the degree of imbalance for different numbers of clusters, cluster sizes, and covariate intraclass correlation coefficients. We focused on the impact of race as a covariate, given the emphasis of regulatory and funding bodies on understanding the influence of demographic characteristics on treatment effectiveness. We found that bias in the treatment effect is proportional to both the degree of baseline covariate imbalance and the covariate effect size. Larger numbers of clusters result in lower covariate imbalance, and increasing cluster size is less effective in reducing imbalance compared to increasing the number of clusters. Models adjusted for important baseline confounders are superior to unadjusted models for minimizing bias in both model-based simulations and an innovative simulation based on real clinical trial data. Higher outcome intraclass correlation coefficients did not affect bias but resulted in greater variance in treatment estimates.

Exercise Training in Patients With Chronic Heart Failure and Atrial Fibrillation

BACKGROUND

The safety and efficacy of aerobic exercise in heart failure (HF) patients with atrial fibrillation (AF) has not been well evaluated.

OBJECTIVES

This study examined whether outcomes with exercise training in HF vary according to AF status.

METHODS

HF-ACTION (Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training) randomized 2,331 ambulatory HF patients with ejection fraction ≤35% to exercise training or usual care. We examined clinical characteristics and outcomes (mortality/hospitalization) by baseline AF status (past history of AF or AF on baseline electrocardiogram vs. no AF) using adjusted Cox models and explored an interaction with exercise training. We assessed post-randomization AF events diagnosed via hospitalizations for AF and reports of serious arrhythmia caused by AF.

RESULTS

Of 2,292 patients with baseline rhythm data, 382 (17%) had AF, 1,602 (70%) had sinus rhythm, and 308 (13%) had "other" rhythm. Patients with AF were older and had lower peak Vo₂. Over a median follow-up of 2.6 years, AF was associated with a 24% per year higher rate of mortality/hospitalization (hazard ratio [HR]: 1.53; 95% confidence interval [CI]: 1.34 to 1.74; p < 0.001) in unadjusted analysis; this did not remain significant after adjustment (HR: 1.15; 95% CI: 0.98 to 1.35; p = 0.09). There was no significant difference in AF event rates by randomized treatment assignment in the overall population or by baseline AF status (all p > 0.10). There was no interaction between AF and exercise training on measures of functional status or clinical outcomes (all p > 0.10).

CONCLUSIONS

AF in patients with chronic HF was associated with older age, reduced exercise capacity at baseline, and a higher overall rate of clinical events, but not a differential response to exercise training for clinical outcomes or changes in exercise capacity. (Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training [HF-ACTION]; NCT00047437).

Psychosocial Factors, Exercise Adherence, and Outcomes in Heart Failure Patients: Insights From Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training (HF-ACTION)

BACKGROUND

Psychosocial factors may influence adherence with exercise training for heart failure (HF) patients. We aimed to describe the association between social support and barriers to participation with exercise adherence and clinical outcomes.

METHODS AND RESULTS

Of patients enrolled in Heart Failure: A Controlled Trial Investigating Outcomes of Exercise Training (HF-ACTION), 2279 (97.8%) completed surveys to assess social support and barriers to exercise, resulting in the perceived social support score (PSSS) and barriers to exercise score (BTES). Higher PSSS indicated higher levels of social support, whereas higher BTES indicated more barriers to exercise. Exercise time at 3 and 12 months correlated with PSSS (r= 0.09 and r= 0.13, respectively) and BTES (r=-0.11 and r=-0.12, respectively), with higher exercise time associated with higher PSSS and lower BTES (All P<0.005). For cardiovascular death or HF hospitalization, there was a significant interaction between the randomization group and BTES (P=0.035), which corresponded to a borderline association between increasing BTES and cardiovascular death or HF hospitalization in the exercise group (hazard ratio 1.25, 95% confidence interval 0.99, 1.59), but no association in the usual care group (hazard ratio 0.83, 95% confidence interval 0.66, 1.06).

CONCLUSIONS

Poor social support and high barriers to exercise were associated with lower exercise time. PSSS did not impact the effect of exercise training on outcomes. However, for cardiovascular death or HF hospitalization, exercise training had a greater impact on patients with lower BTES. Given that exercise training improves outcomes in HF patients, assessment of perceived barriers may facilitate individualized approaches to implement exercise training therapy in clinical practice.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00047437.

Central nervous system circuits modified in heart failure: pathophysiology and therapeutic implications

The pathophysiology of heart failure (HF) is characterized by an abnormal activation of neurohumoral systems, including the sympathetic nervous and the renin-angiotensin-aldosterone systems, which have long-term deleterious effects on the disease progression. Perpetuation of this neurohumoral activation is partially dependent of central nervous system (CNS) pathways, mainly involving the paraventricular nucleus of the hypothalamus and some regions of the brainstem. Modifications in these integrative CNS circuits result in the attenuation of sympathoinhibitory and exacerbation of sympathoexcitatory pathways. In addition to the regulation of sympathetic outflow, these central pathways coordinate a complex network of agents with an established pathophysiological relevance in HF such as angiotensin, aldosterone, and proinflammatory cytokines. Central pathways could be potential targets in HF therapy since the current mainstay of HF pharmacotherapy aims primarily at antagonizing the peripheral mechanisms. Thus, in the present review, we describe the role of CNS pathways in HF pathophysiology and as potential novel therapeutic targets.

Effects of exercise training on outcomes in women with heart failure: analysis of HF-ACTION (Heart Failure-A Controlled Trial Investigating Outcomes of Exercise TraiNing) by sex

OBJECTIVES

The authors hypothesized that the women enrolled in the HF-ACTION (Heart Failure-A Controlled Trial Investigating Outcomes of Exercise TraiNing) trial and randomly assigned to exercise training (ET) would improve functional capacity as measured by peak oxygen uptake (VO2) compared with those in the usual care group. Furthermore, they hypothesized that the improvement in peak VO2 would correlate with prognosis. They explored whether exercise had a differential effect on outcomes in women versus men.

BACKGROUND

There is less evidence for the benefit of ET in women with heart failure (HF) compared with men because of the small numbers of women studied.

METHODS

HF-ACTION was a randomized trial of ET versus usual care in 2,331 patients with class II-IV HF and a left ventricular ejection fraction of ≤35%. Sex differences in the effects of randomized treatment on clinical outcomes were assessed through the use of a series of Cox proportional hazards models, controlling for covariates known to affect prognosis in HF-ACTION.

RESULTS

Women had lower baseline peak VO2 and 6-min walk distance than did men (median, 13.4 vs. 14.9 ml/min/kg and 353 vs. 378 m, respectively). An increase in peak VO2 at 3 months was present in women and men in the ET group (mean ± SD; median, 0.88 ± 2.2, 0.80 and 0.77 ± 2.7, 0.60, respectively, women vs. men; p = 0.42). Women randomly assigned to ET had a significant reduction in the primary endpoint, (hazard ratio: 0.74) compared with men (hazard ratio: 0.99) randomly assigned to ET, with a significant treatment-by-sex interaction (p = 0.027).

CONCLUSIONS

Although there is no significant difference between men and women in the effect of ET on peak VO2 change at 3 months, ET in women with HF is associated with a larger reduction in rate of the combined endpoint of all-cause mortality and hospital stay than in men.