Lewis, Gregory D.

Abstract Heart failure with preserved ejection fraction (HFpEF) is a heterogeneous entity with complex pathophysiology and manifestations. Phenomapping is the process of applying statistical learning techniques to patient data to identify distinct subgroups based on patterns in the data. Phenomapping has emerged as a technique with potential to improve the understanding of different HFpEF phenotypes. Phenomapping efforts have been increasing in HFpEF over the past several years using a variety of data sources, clinical variables, and statistical techniques. This review summarizes methodologies and key takeaways from these studies, including consistent discriminating factors and conserved HFpEF phenotypes. We argue that phenomapping results to date have had limited implications for clinical care and clinical trials, given that the phenotypes, as currently described, are not reliably identified in each study population and may have significant overlap. We review the inherent limitations of aggregating and utilizing phenomapping results. Lastly, we discuss potential future directions, including using phenomapping to optimize the likelihood of clinical trial success or to drive discovery in mechanisms of the disease process of HFpEF.

There is a lack of consensus on how we define heart failure with preserved ejection fraction (HFpEF), with wide variation in diagnostic criteria across society guidelines. This lack of uniformity in disease definition stems in part from an incomplete understanding of disease pathobiology, phenotypic heterogeneity, and natural history. We review current knowledge gaps and existing diagnostic tools and algorithms. We present a simple approach to implement these tools within the constraints of the current knowledge base, addressing separately (1) hospitalized individuals with rest congestion, where diagnosis is more straightforward; and (2) individuals with exercise intolerance, where diagnosis is more complex. Here, a potential role for advanced or provocative testing, including evaluation of hemodynamic responses to exercise is considered. More importantly, we propose focus areas for future studies to develop accurate and feasible diagnostic tools for HFpEF, including animal models that recapitulate human HFpEF, and human studies that both address a fundamental understanding of HFpEF pathobiology, and new diagnostic approaches and tools, as well. In sum, there is an urgent need to more accurately define the syndrome of HFpEF to inform diagnosis, patient selection for clinical trials, and, ultimately, future therapeutic approaches.

Abstract Aims Patient-reported quality of life (QOL) is a highly prognostic and clinically relevant endpoint in patients with heart failure (HF) with preserved ejection fraction (HFpEF). The relationships between QOL and different markers of HF severity remain unclear, particularly as they relate to functional capacity and directly measured activity levels. We hypothesized that QOL would demonstrate a stronger relationship with measures of exercise capacity and adiposity compared to other disease measures. Methods and results This is a secondary analysis of the National Heart, Lung, and Blood Institute-sponsored RELAX, NEAT-HFpEF and INDIE-HFpEF trials to determine the relationships between QOL (assessed by the Kansas City Cardiomyopathy Questionnaire and Minnesota Living with Heart Failure Questionnaire) and different domains reflecting HF severity, including maximal aerobic capacity (peak oxygen consumption), submaximal exercise capacity (6-min walk distance), volume of daily activity (accelerometry), physician-estimated functional class, resting echocardiography, and plasma natriuretic peptide levels. A total of 408 unique patients with chronic HFpEF were split into tertiles of QOL scores defined as QOLworst, QOLintermediate, QOLbest. The QOLworst HFpEF group was youngest, with a higher body mass index, greater prevalence of class II obesity and diabetes, and the lowest N-terminal pro-brain natriuretic peptide (NT-proBNP) levels. After adjustment for age, sex and body mass index, poorer QOL was associated with worse physical capacity and activity levels, assessed by peak oxygen consumption, 6-min walk distance and actigraphy, but was not associated with NT-proBNP or indices from resting echocardiography. QOL was similarly reduced in patients with and without prior HF hospitalization. Conclusions Quality of life in HFpEF is poorest in patients who are young, obese and have diabetes, and is more robustly tied to measures reflecting functional capacity and daily activity levels rather than elevations in NT-proBNP or prior HF hospitalization. These findings have major implications for the understanding of QOL in HFpEF and for the design of future clinical trials targeting symptom improvement in HFpEF. Clinical Trial Registration: RELAX, NCT00763867; NEAT-HFpEF, NCT02053493; INDIE-HFpEF, NCT02742129.

Approximately half of patients with heart failure have preserved ejection fraction. There is no proven treatment that improves outcome. The pathophysiology of heart failure with preserved ejection fraction is complex and includes left ventricular systolic and diastolic dysfunction, pulmonary vascular disease, endothelial dysfunction, and peripheral abnormalities. Multiple lines of evidence point to impaired nitric oxide (NO)-cGMP bioavailability as playing a central role in each of these abnormalities. In contrast to traditional organic nitrate therapies, an alternative strategy to restore NO-cGMP signaling is via inorganic nitrite. Inorganic nitrite, previously considered to be an inert byproduct of NO metabolism, functions as an important in vivo reservoir for NO generation, particularly under hypoxic and acidosis conditions. As such, inorganic nitrite becomes most active at times of greater need for NO signaling, as during exercise when left ventricular filling pressures and pulmonary artery pressures increase. Herein, we present the rationale and design for the INDIE-HFpEF trial (Inorganic Nitrite Delivery to Improve Exercise Capacity in Heart Failure with Preserved Ejection Fraction), which is a multicenter, randomized, double-blind, placebo-controlled cross-over study assessing the effect of inhaled inorganic nitrite on peak exercise capacity, conducted in the National Heart, Lung, and Blood Institute–sponsored Heart Failure Clinical Research Network. Clinical Trial Registration URL: http://www.clinicaltrials.gov . Unique identifier: NCT02742129.

Abstract Background While abnormal left ventricular (LV) global longitudinal strain (GLS) has been described in patients with heart failure with preserved ejection fraction (HFpEF), its prevalence and clinical significance are poorly understood. Methods and results Patients enrolled in the RELAX trial of sildenafil in HFpEF (LV ejection fraction ≥50%) in whom two-dimensional, speckle-tracking LV GLS was possible (n = 187) were analysed. The distribution of LV GLS and its associations with clinical characteristics, LV structure and function, biomarkers, exercise capacity and quality of life were assessed. Baseline median LV GLS was −14.6% (25th and 75th percentile, −17.0% and −11.9%, respectively) and abnormal (≥ − 16%) in 122/187 (65%) patients. Patients in the tertile with the best LV GLS had lower N-terminal pro-brain natriuretic peptide (NT-proBNP) [median 505 pg/mL (161, 1065) vs. 875 pg/mL (488, 1802), P = 0.008) and lower collagen IIIN-terminal propeptide (PIIINP) levels [median 6.7 µg/L (5.1, 8.1) vs. 8.1 µg/L (6.5, 10.5), P = 0.001] compared with the tertile with the worst LV GLS. There was also a modest linear relationship with LV GLS and log-transformed NT-proBNP and PIIINP (r = 0.29, P < 0.001 and r = 0.19, P = 0.009, respectively). We observed no linear association of LV GLS with Minnesota Living with Heart Failure scores, 6-min walk distance, peak oxygen consumption, or expiratory minute ventilation/carbon dioxide excretion slope. Conclusions Impaired LV GLS is common among HFpEF patients, indicating the presence of covert systolic dysfunction despite normal LV ejection fraction. Impaired LV GLS was associated with biomarkers of wall stress and collagen synthesis and diastolic dysfunction but not with quality of life or exercise capacity, suggesting other processes may be more responsible for these aspects of the HFpEF syndrome.