Heart failure (HF) can be defined as an abnormality of cardiac structure or function leading to failure of the heart to deliver oxygen at a rate commensurate with the requirements of the metabolizing tissues, despite normal filling pressures (or only at the expense of increased filling pressures). Approximately 1 – 2% of the general population in developed countries have HF, with the prevalence rising to ≥ 10% among persons 70 years of age or older (1).
The diagnosis of HF can be difficult, especially in the early stages. Although symptoms bring patients to medical attention, many of the symptoms of HF (breathlessness, elevated jugular venous pressure, hepatojugular reflux, fatigue, tiredness) are non-specific and do not, always discriminate between HF and other medical problems. Symptoms that are more specific (i.e. orthopnoea and paroxysmal nocturnal dyspnoea) are less common, especially in patients with milder symptoms, and are, therefore, insensitive (2).
Echocardiography provides information about cardiac anatomy (e.g. volumes, geometry, mass) and function (e.g. LV function and wall motion, valvular function, right ventricular function, pulmonary artery pressure, pericardium) and is essential for the diagnosis and prognosis of HF. Of the several imaging modalities available, echocardiography is the method of choice in patients with suspected HF for reasons of accuracy, availability (including portability), safety, and cost (3).
Where the availability of echocardiography is limited, an alternative approach to diagnosis is to measure the blood concentration of a natriuretic peptide, a family of hormones secreted in increased amounts when the heart is diseased or the load on any chamber is increased (e.g.by AF, pulmonary embolism, and some non-cardiovascular conditions, including renal failure). Most importantly the N-terminal pro–B-type natriuretic peptide (NT-proBNP) is a powerful neurohormonal predictor of prognosis in HF and can be used to titrate therapy (4). Current guidelines combine echocardiographic assessment with NT-proBNP levels for baseline and follow-up evaluation of patients with HF (1).
Several new molecules have been proposed as biomarkers for evaluating HF. Among them, the most promising are cardiotrophin-1 (CT-1) and galectin-3. CT-1 is a 21.5-kDa protein, member of the interleukin 6 (IL-6) family of cytokines – first described by Pennica et al. (5) to induce cardiomyocyte hypertrophy by atrial natriuretic peptide secretion and myosin light chains organisation into sarcomeres. Regarding CT-1 and HF, Talwar et al. (6) were the first to report that plasma CT-1 levels correlate with the degree of systolic dysfunction in HF patients. Plasma CT-1 levels are also increased in patients with diastolic heart failure and positively correlate with left ventricular filing pressures. Galectin-3 is one of the key links between inflammation and fibrosis at the cardiovascular level. Galectin-3 is a profibrotic agent by itself and also mediates aldosterone-induced cardiac, vascular and renal fibrosis. In this context, it is not surprising that galectin-3 is a biomarker for chronic HF prognosis (7).
Lung ultrasound (LUS) through B-line evaluation has been recently proposed as a simple, noninvasive, and semiquantitative tool to assess extravascular lung water (8). B-lines have been shown to be correlated to NT-proBNP and echocardiographic parameters in patients with acute dyspnea (9) or chronic HF (10). LUS can also identify clinically silent pulmonary edema, suggesting that it could be added to the clinical evaluation to improve hemodynamic profiling and treatment optimization. The recognition and quantification of pulmonary congestion are crucial steps in a thorough evaluation of patients with HF in any clinical setting. LUS seems to be a simple and accurate method for assessing decompensation in HF patients.
There is also a strong evidence of the impact of obesity and overall body composition on the development and progression of heart failure. Understanding of this complex interplay is limited, but has clinical value given the recognized impact of adiposity and weight loss on predicting heart failure outcomes. Adipocytes are sensitive to natriuretic peptides, activating lipolysis and enhancing the expression of brown adipocyte genes; increasing energy use and thermogenesis (11). Natriuretic peptides stimulate the release of adipokines, specifically adiponectin and leptin, which increase energy use and weight reduction (11). Adipokines are involved in whole body energy metabolism, and adiponectin is particularly involved in the regulation of skeletal muscle metabolism and weight loss in patients with heart failure.
Bioimpedance analysis is relatively inexpensive, safe, portable, and gives additional information on the different fluid compartments, fat and lean tissue composition. Bioimpedance appears to be one of the most promising and increasingly used techniques to objectively determine fluid status. This technique has been introduced in different forms during the last 15 years (single/multiple frequency, segmental/whole-body bioimpedance) but recently gained momentum on the basis of new solid evidence from clinical studies on fluid status assessment. It has been validated in both healthy persons and patients with chronic kidney disease by isotope dilution methods, by accepted reference body composition methods, and by techniques that measure relative changes in fluid volumes. In contrast to earlier bioimpedance methodologies, the bioimpedance spectroscopy (BIS) expresses body composition as a three-compartment model, providing overhydration, lean tissue index (LTI), and fat tissue index (FTI), whereby LTI and FTI are the respective tissue masses normalized to height squared. BIS defines the individual fluid status/overload on the basis of an individual’s normal extracellular volume, taking into account the individual’s body composition. Recent studies indicate that the fluid overload indices derived from BIA measurement are independent predictors of mortality in prevalent hemodialysis (HD) patients, and importantly, using this method to actively guide HD patients toward normohydration, blood pressure, arterial stiffness and even survival (12) may be improved.
To date, no study has evaluated BIS performance for the body compartment (fluid, lean and fat mass) assessment in HF patients. The main aim of this study was to compare BIS derived fluid status parameters (overhydration, total body water, extracellular water and intracellular water) with clinical evaluation, LUS, cardiac biomarkers, and echocardiographic characteristics in a cohort of patients with HF and also to determine the impact of the these parameters on different outcomes in the same population. Additionally, we will also test the association between BIS derived body compartments (LTI, FTI) with echocardiographic parameters and adipokines in the same population of HF patients.
References:
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