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NEUROHUMORAL, CARDIAC, AND INFLAMMATORY INDICATORS IN
DETERMINING THE SEVERITY AND PROGRESSION OF HEART FAILURE
Akromov Iskandar Rahmonkul ogli
Assitant lecturer at the Alfraganus University
Email address: akromoviskandar@gmail.com
https://doi.org/10.5281/zenodo.14908691
Abstract
Heart failure is a widespread condition among adults, contributing significantly to global
morbidity and mortality. Its principal risk factors include coronary artery disease,
hypertension, obesity, diabetes mellitus, chronic pulmonary disorders, a family history of
cardiovascular disease, and cardiotoxic treatments. A key contributor to poor outcomes in
heart failure patients is the ongoing progression of the disease. This review examines the
evidence regarding both established and emerging neurohumoral biomarkers for managing
and diagnosing heart failure progression. Although numerous biomarkers have been suggested
as potentially useful, none yet emdiv the ideal characteristics needed for effective screening,
diagnosis, prognosis, and therapeutic management. Furthermore, the clinical and
pathophysiological importance of these biomarkers may vary according to the disease's
presentation, stage, and severity. We also discuss the primary classifications of heart failure
based on left ventricular ejection fraction—including heart failure with preserved ejection
fraction, heart failure with reduced ejection fraction, and the newly defined heart failure with
mid-range ejection fraction. Specific biomarker panels may offer varying predictive
performance for the progression of heart failure, particularly in forecasting the future course
of the disease and in monitoring adverse or reverse left ventricular remodeling. This article
aims to provide an overview of both the fundamental and additional mechanisms underlying
heart failure progression, contributing to a more comprehensive understanding of its
pathogenesis.
Nervous System Activation in Heart Failure Progression
The rapid activation of both systemic and cardiac sympathetic nervous systems (SNS) is
one of the earliest adaptive responses in heart failure. While initially compensatory, SNS
activation also has harmful effects. The release of catecholamines can trigger various
arrhythmias and worsen myocardial ischemia. Elevated levels of plasma epinephrine are
known to exert direct toxic effects on cardiac myocytes, promoting hypertrophy and apoptosis.
Additionally, norepinephrine induces signal transduction abnormalities, such as down-
regulation of beta-1 receptors and uncoupling of beta-2 receptors, which can lead to reflex
tachycardia as well as malignant ventricular arrhythmias. The maladaptive vasoconstriction
induced by SNS activation further contributes to organ failures, including pulmonary
hypertension and renal failure.
This early increase in sympathetic activity, coupled with a reduction in parasympathetic
tone, represents a fundamental maladaptive mechanism in the onset and progression of heart
failure. This imbalance forms the basis of the neuroendocrine model of heart failure, which is
characterized by vasoconstrictive, profibrotic, and arrhythmogenic effects. The decreased
activity of the parasympathetic nervous system results in abnormal autonomic regulation and
reduced heart rate variability.
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As heart failure worsens, circulating norepinephrine levels rise. Clinical evidence suggests
that certain treatments, like valsartan, can blunt this increase, whereas others, such as
mineralocorticoid receptor antagonists, may not have the same effect. Along with
catecholamines, chromogranin-A—a component of adrenal chromaffin granules—appears to
play a role in regulating the adrenergic system, with elevated levels observed in both acute and
chronic heart failure and potential prognostic implications.
Within heart failure, the activation of sympathetic signaling pathways coincides with a
reduction in cardiac beta receptor number, density, and responsiveness, along with the
downregulation of key signaling molecules such as Gsα and adenylyl cyclase. These changes,
while potentially protective by reducing arrhythmias, apoptosis, and hypertrophy, can also lead
to functional deterioration through energy depletion. Additionally, the significant upregulation
and activation of G-protein coupled receptor kinases (GRKs) further disrupt beta receptor
signaling, contributing to the progression of heart failure.
Natriuretic Peptides
Human brain natriuretic peptide (BNP) and its amino-terminal fragment (NT-proBNP)
are generated in equal amounts from the cleavage of the 108-amino acid precursor, proBNP, by
convertases such as corin and furin. Once formed, the active BNP is quickly broken down in the
div by enzymes including dipeptidyl peptidase IV and neprilysin. Both BNP and NT-proBNP
are predominantly produced by ventricular myocytes in response to increased myocardial wall
stress caused by volume or pressure overload. These peptides play a critical role in the
progression of heart failure, owing to their diuretic, natriuretic, vasodilatory, and anti-
hypertrophic effects.
Since the early 2000s, numerous studies have demonstrated the clinical utility of testing
for B-type natriuretic peptides, supporting their use as circulating biomarkers for diagnosing
and monitoring the severity and progression of heart failure. Today, BNP and NT-proBNP
assays are routinely employed in various clinical settings for heart failure management. Robust
evidence indicates that these biomarkers are especially valuable in diagnosing heart failure in
patients presenting with dyspnea. Trials such as Breathing Not Properly and the ProBNP
Investigation of Dyspnea have shown that measuring BNP and NT-proBNP in emergency room
patients with shortness of breath provides high diagnostic accuracy and a strong negative
predictive value, particularly when BNP levels are below 100 ng/L. Although diagnostic
thresholds may be lower in outpatient settings, the value of these peptides in diagnosing heart
failure has been consistently validated. In a study involving approximately 800 patients with
chronic heart failure, BNP and NT-proBNP levels were strongly associated with left ventricular
systolic dysfunction, with area under the curve values of 0.803 and 0.730, respectively. In stable
patients with heart failure with reduced ejection fraction, circulating BNP levels correlate with
disease severity and tend to rise with worsening symptoms as classified by the NYHA system.
Major scientific organizations, including the American College of Cardiology, American
Heart Association, Heart Failure Society of America, and European Society of Cardiology,
endorse the use of natriuretic peptide assays for diagnostic purposes. However, there is no
universal diagnostic cutoff, which can place these measurements into a "grey zone."
Additionally, levels of BNP and NT-proBNP can be affected by factors such as gender, age, and
comorbid conditions—especially renal function—necessitating that their interpretation be
integrated with the overall clinical assessment.
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Cardiac Troponins
Cardiac troponins are released into the bloodstream when the membranes of heart
muscle cells are damaged, especially following cardiac necrosis, making them the gold standard
biomarkers for diagnosing myocardial infarction. Troponin, an essential intracellular protein
for regulating muscle contraction, comprises three subunits: Troponin I, T, and C. Importantly,
cardiac troponins I (cTnI) and T (cTnT) are exclusive to heart muscle cells, unlike Troponin C,
which is also present in skeletal muscle. Consequently, elevated levels of circulating cardiac
troponins specifically indicate ongoing myocardial damage, and they have been used for
decades to identify myocardial infarction.
Beyond myocardial infarction, elevated cardiac troponin levels have also been observed
in cases of acute heart failure, in the decompensation of chronic heart failure, and in other
conditions with less well-defined mechanisms of heart injury, such as septic shock, pulmonary
embolism, myocarditis, drug-induced cardiotoxicity, and renal dysfunction. Patients with
severe infections, those admitted to intensive care units, or those who succumb to illness tend
to have markedly higher troponin levels.
One possible explanation for increased cardiac troponins in chronic heart failure is a
mismatch between myocardial oxygen supply and demand—either reversible or irreversible.
This release can result from both acute and chronic myocardial stress, including chronic
subclinical or sub-endocardial ischemia, or from direct injury to heart cells. It may also reflect
an increased turnover of cardiomyocytes in the setting of progressive myocardial dysfunction,
which might explain why troponin levels can be detectable in non-cardiac conditions
characterized by significant metabolic demand relative to supply, such as hypotension and
shock. Alternatively, elevated circulating troponin levels might be partly due to impaired renal
clearance rather than solely increased myocardial damage.
In the general population, high-sensitivity assays that measure cTnT can detect
subclinical cardiac injury and have been associated with an increased risk of structural heart
disease and all-cause mortality. These newer assays frequently detect measurable troponin
levels even in individuals without heart failure, and the detected levels are independently
linked to all-cause mortality, cardiovascular mortality, and the development of heart failure,
even after accounting for factors such as renal function, NT-proBNP, and hs-CRP.
BIOMARKERS OF FIBROSIS: Transforming Growth Factor-β1 (TGF-β1)
TGF-β1 is a highly potent cytokine that plays a central role in tissue repair and is a key
driver of fibrosis when its production is sustained. Elevated levels of TGF-β1 are commonly
found in almost every fibrotic condition. Increasing evidence suggests that oxidative stress is a
contributing factor to fibrogenesis in various tissues, including the liver, lungs, arteries,
nervous system, and heart.
In the heart, cardiac fibroblasts are essential for remodeling after myocardial infarction,
forming replacement scar tissue in the infarcted area while also promoting fibrosis in non-
infarcted regions. TGF-β1 is secreted by various cells—such as infiltrating lymphocytes,
platelets, activated macrophages, injured myocytes, and fibroblasts—and stimulates the
deposition of extracellular matrix at sites of injury. This occurs through the induction of new
matrix proteins like collagens, fibronectin, and proteoglycans, as well as through the inhibition
of proteases and the stimulation of protease inhibitors.
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Moreover, TGF-β1 enhances the expression of cell-surface integrin receptors, which
strengthens cell-matrix interactions and promotes matrix assembly. Its effects are further
amplified by an autoinductive feedback mechanism, where TGF-β1 stimulates its own
production. Normally, binding of TGF-β1 to proteoglycans in the matrix or near the cell surface
may signal the termination of its production once tissue repair is complete. However, in the
setting of repeated injury, this autoinduction persists, leading to continuous overproduction of
TGF-β1 and relentless extracellular matrix synthesis, ultimately resulting in fibrosis.
Additionally, reactive oxygen species have been shown to upregulate both TGF-β1 and collagen
type I expression in various tissues, underscoring the critical role of TGF-β1 in cell proliferation,
differentiation, migration, and extracellular matrix production in the myocardium.
Galectin-3 (Gal-3)
Galectin-3 is a soluble β-galactoside-binding lectin that plays a significant mechanistic
role in the development of cardiac fibrosis and remodeling, and it helps identify high-risk
subgroups among heart failure patients, serving both as a risk marker and a risk factor.
Increasing evidence suggests that Gal-3 is crucial for macrophage migration and phagocytic
activity. Once released by macrophages, Gal-3 can stimulate fibroblast proliferation and
modulate collagen synthesis by increasing collagen I production and altering the collagen I-to-
collagen III ratio. In addition to its involvement in liver and kidney fibrosis, Gal-3 is strongly
linked to the formation of cardiac fibrosis and is a key determinant of cardiac remodeling and
heart failure progression, possibly through interactions with aldosterone-mediated damage
pathways.
Experimental studies highlighting Gal-3's role in fibrotic, inflammatory, and remodeling
processes in heart failure have spurred interest in its potential use as a plasma biomarker. In a
2006 study comparing NT-proBNP, apelin, and Gal-3 in patients presenting with acute dyspnea,
only 209 out of 599 were eventually diagnosed with heart failure. Although Gal-3 demonstrated
limited diagnostic accuracy for acute heart failure, it emerged as the strongest predictor of early
adverse events, such as re-hospitalization for heart failure or all-cause mortality within 60 days.
Subsequent research confirmed that Gal-3 could also forecast long-term outcomes in another
cohort of acute heart failure patients, with a proposed cutoff of 14.97 ng/mL, independent of
echocardiographic parameters like left ventricular dimensions, ejection fraction, and right
ventricular pressure.
Further investigations into Gal-3's prognostic role have been conducted in substudies of
larger clinical trials. For instance, in the Deventer-Alkmaar HF (DEAL-HF) study, Gal-3 levels
were measured in 232 patients with chronic heart failure (NYHA III-IV) over a 6.5-year follow-
up. A baseline Gal-3 level, using a cutoff of 17.6 ng/mL, predicted all-cause mortality even after
adjustments for age, gender, creatinine clearance, and NT-proBNP. When patients were
stratified based on both NT-proBNP and Gal-3 levels, those with elevated levels of both
biomarkers exhibited a 1.5- to 2-fold higher mortality rate compared to other groups. However,
in a larger cohort of 895 chronic heart failure patients with a left ventricular ejection fraction
below 35% from the HF-ACTION study, Gal-3 lost its standalone prognostic significance for
predicting a composite outcome of all-cause death or re-hospitalization after accounting for
peak oxygen consumption and NT-proBNP levels.
CONCLUSIONS
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In addition to well-established biomarkers such as NT-proBNP and hs-CRP, a variety of
novel substances are under extensive investigation. Both fundamental and preclinical evidence
support the use of biomarker evaluation as a promising approach for better characterizing
heart failure and tailoring individualized therapies. Despite over 30 years of clinical research
and the development of many effective treatments for heart failure, the rates of cardiovascular
events—including hospitalizations, emergency department visits, office consultations, acute
interventions, and mortality—remain unacceptably high. A deeper understanding of the
molecular pathophysiology of heart failure may unlock new pharmacologic targets, highlighting
the urgent need for innovative therapies that address previously unexplored pathways in all
patients with heart failure.
Ultimately, the focus must shift toward the quality of clinical studies that aim to refine
diagnostic and predictive models, as well as the use of biomarkers to customize therapeutic
strategies.
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