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Heart Failure Practice Essentials Heart failure develops when the heart, via an abnormality of cardiac function (detectable or not), fails to pump blood at a rate commensurate with the requirements of the metabolizing tissues or is able to do so only with an elevated diastolic filling pressure. See the image below.

This chest radiograph shows an enlarged cardiac silhouette and edema at the lung bases, signs of acute heart failure.

Signs and symptoms Signs and symptoms of heart failure include the following:                 

Exertional dyspnea and/or dyspnea at rest Orthopnea Acute pulmonary edema Chest pain/pressure and palpitations Tachycardia Fatigue and weakness Nocturia and oliguria Anorexia, weight loss, nausea Exophthalmos and/or visible pulsation of eyes Distention of neck veins Weak, rapid, and thready pulse Rales, wheezing S 3 gallop and/or pulsus alternans Increased intensity of P 2 heart sound Hepatojugular reflux Ascites, hepatomegaly, and/or anasarca Central or peripheral cyanosis, pallor See Clinical Presentation for more detail.

Diagnosis Heart failure criteria, classification, and staging The Framingham criteria for the diagnosis of heart failure consists of the concurrent presence of either 2 major criteria or 1 major and 2 minor criteria.[1] Major criteria include the following:  

Paroxysmal nocturnal dyspnea Weight loss of 4.5 kg in 5 days in response to treatment

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Neck vein distention Rales Acute pulmonary edema Hepatojugular reflux S 3 gallop Central venous pressure greater than 16 cm water Circulation time of 25 seconds Radiographic cardiomegaly Pulmonary edema, visceral congestion, or cardiomegaly at autopsy Minor criteria are as follows:

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Nocturnal cough Dyspnea on ordinary exertion A decrease in vital capacity by one third the maximal value recorded Pleural effusion Tachycardia (rate of 120 bpm) Bilateral ankle edema The New York Heart Association (NYHA) classification system categorizes heart failure on a scale of I to IV,[2] as follows:

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Class I: No limitation of physical activity Class II: Slight limitation of physical activity Class III: Marked limitation of physical activity Class IV: Symptoms occur even at rest; discomfort with any physical activity The American College of Cardiology/American Heart Association (ACC/AHA) staging system is defined by the following 4 stages[3, 4] :

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Stage A: High risk of heart failure but no structural heart disease or symptoms of heart failure Stage B: Structural heart disease but no symptoms of heart failure Stage C: Structural heart disease and symptoms of heart failure Stage D: Refractory heart failure requiring specialized interventions Testing The following tests may be useful in the initial evaluation for suspected heart failure [3, 5, 6] :

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Complete blood count (CBC) Urinalysis Electrolyte levels Renal and liver function studies Fasting blood glucose levels Lipid profile Thyroid stimulating hormone (TSH) levels B-type natriuretic peptide levels N-terminal pro-B-type natriuretic peptide Electrocardiography Chest radiography 2-dimensional (2-D) echocardiography Nuclear imaging [7] Maximal exercise testing Pulse oximetry or arterial blood gas See Workup for more detail.

Management Treatment includes the following: 

Nonpharmacologic therapy: Oxygen and noninvasive positive pressure ventilation, dietary sodium and fluid restriction, physical activity as appropriate, and attention to weight gain  Pharmacotherapy: Diuretics, vasodilators, inotropic agents, anticoagulants, beta blockers, and digoxin Surgical options Surgical treatment options include the following:    

Electrophysiologic intervention Revascularization procedures Valve replacement/repair Ventricular restoration

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Extracorporeal membrane oxygenation Ventricular assist devices Heart transplantation Total artificial heart

Pathophysiology The common pathophysiologic state that perpetuates the progression of heart failure is extremely complex, regardless of the precipitating event. Compensatory mechanisms exist on every level of organization, from subcellular all the way through organ-to-organ interactions. Only when this network of adaptations becomes overwhelmed does heart failure ensue. [8, 9, 10, 11, 12]

Adaptations Most important among the adaptations are the following[13] :   

The Frank-Starling mechanism, in which an increased preload helps to sustain cardiac performance Alterations in myocyte regeneration and death Myocardial hypertrophy with or without cardiac chamber dilatation, in which the mass of contractile tissue is augmented  Activation of neurohumoral systems The release of norepinephrine by adrenergic cardiac nerves augments myocardial contractility and includes activation of the renin-angiotensin-aldosterone system [RAAS], the sympathetic nervous system [SNS], and other neurohumoral adjustments that act to maintain arterial pressure and perfusion of vital organs. In acute heart failure, the finite adaptive mechanisms that may be adequate to maintain the overall contractile performance of the heart at relatively normal levels become maladaptive when trying to sustain adequate cardiac performance. [14] The primary myocardial response to chronic increased wall stress is myocyte hypertrophy, death/apoptosis, and regeneration.[15] This process eventually leads to remodeling, usually the eccentric type. Eccentric remodeling further worsens the loading conditions on the remaining myocytes and perpetuates the deleterious cycle. The idea of lowering wall stress to slow the process of remodeling has long been exploited in treating heart failure patients. [16] The reduction of cardiac output following myocardial injury sets into motion a cascade of hemodynamic and neurohormonal derangements that provoke activation of neuroendocrine systems, most notably the above-mentioned adrenergic systems and RAAS.[17] The release of epinephrine and norepinephrine, along with the vasoactive substances endothelin-1 (ET-1) and vasopressin, causes vasoconstriction, which increases calcium afterload and, via an increase in cyclic adenosine monophosphate (cAMP), causes an increase in cytosolic calcium entry. The increased calcium entry into the myocytes augments myocardial contractility and impairs myocardial relaxation (lusitropy). The calcium overload may induce arrhythmias and lead to sudden death. The increase in afterload and myocardial contractility (known as inotropy) and the impairment in myocardial lusitropy lead to an increase in myocardial energy expenditure and a further decrease in cardiac output. The increase in myocardial energy expenditure leads to myocardial cell death/apoptosis, which results in heart failure and further reduction in cardiac output, perpetuating a cycle of further increased neurohumoral stimulation and further adverse hemodynamic and myocardial responses. In addition, the activation of the RAAS leads to salt and water retention, resulting in increased preload and further increases in myocardial energy expenditure. Increases in renin, mediated by decreased stretch of the glomerular afferent arteriole, reduce delivery of chloride to the macula densa and increase beta1-adrenergic activity as a response to decreased cardiac output. This results in an increase in angiotensin II (Ang II) levels and, in turn, aldosterone levels, causing stimulation of the release of aldosterone. Ang II, along with ET-1, is crucial in maintaining effective intravascular homeostasis mediated by vasoconstriction and aldosterone-induced salt and water retention. The concept of the heart as a self-renewing organ is a relatively recent development. [18] This new paradigm for myocyte biology has created an entire field of research aimed directly at augmenting myocardial regeneration. The rate of myocyte turnover has been shown to increase during times of pathologic stress. [15]In heart failure, this mechanism for replacement becomes overwhelmed by an even faster increase in the rate of myocyte loss. This imbalance of hypertrophy and death over regeneration is the final common pathway at the cellular level for the progression of remodeling and heart failure.

Ang II Research indicates that local cardiac Ang II production (which decreases lusitropy, increases inotropy, and increases afterload) leads to increased myocardial energy expenditure. Ang II has also been shown in vitro and in vivo to increase the rate of myocyte apoptosis.[19] In this fashion, Ang II has similar actions to norepinephrine in heart failure. Ang II also mediates myocardial cellular hypertrophy and may promote progressive loss of myocardial function. The neurohumoral factors above lead to myocyte hypertrophy and interstitial fibrosis, resulting in increased myocardial volume

and increased myocardial mass, as well as myocyte loss. As a result, the cardiac architecture changes, which, in turn, leads to further increase in myocardial volume and mass.

Myocytes and myocardial remodeling In the failing heart, increased myocardial volume is characterized by larger myocytes approaching the end of their life cycle. [20] As more myocytes drop out, an increased load is placed on the remaining myocardium, and this unfavorable environment is transmitted to the progenitor cells responsible for replacing lost myocytes. Progenitor cells become progressively less effective as the underlying pathologic process worsens and myocardial failure accelerates. These features—namely, the increased myocardial volume and mass, along with a net loss of myocytes—are the hallmark of myocardial remodeling. This remodeling process leads to early adaptive mechanisms, such as augmentation of stroke volume (Frank-Starling mechanism) and decreased wall stress (Laplace's law), and, later, to maladaptive mechanisms such as increased myocardial oxygen demand, myocardial ischemia, impaired contractility, and arrhythmogenesis. As heart failure advances, there is a relative decline in the counterregulatory effects of endogenous vasodilators, including nitric oxide (NO), prostaglandins (PGs), bradykinin (BK), atrial natriuretic peptide (ANP), and B-type natriuretic peptide (BNP). This decline occurs simultaneously with the increase in vasoconstrictor substances from the RAAS and the adrenergic system, which fosters further increases in vasoconstriction and thus preload and afterload. This results in cellular proliferation, adverse myocardial remodeling, and antinatriuresis, with total body fluid excess and worsening of heart failure symptoms.

Systolic and diastolic failure Systolic and diastolic heart failure each result in a decrease in stroke volume. [21, 22]This leads to activation of peripheral and central baroreflexes and chemoreflexes that are capable of eliciting marked increases in sympathetic nerve traffic. Although there are commonalities in the neurohormonal responses to decreased stroke volume, the neurohormonemediated events that follow have been most clearly elucidated for individuals with systolic heart failure. The ensuing elevation in plasma norepinephrine directly correlates with the degree of cardiac dysfunction and has significant prognostic implications. Norepinephrine, while directly toxic to cardiac myocytes, is also responsible for a variety of signal-transduction abnormalities, such as down-regulation of beta1-adrenergic receptors, uncoupling of beta2-adrenergic receptors, and increased activity of inhibitory G-protein. Changes in beta1-adrenergic receptors result in overexpression and promote myocardial hypertrophy.

ANP and BNP ANP and BNP are endogenously generated peptides activated in response to atrial and ventricular volume/pressure expansion. ANP and BNP are released from the atria and ventricles, respectively, and both promote vasodilation and natriuresis. Their hemodynamic effects are mediated by decreases in ventricular filling pressures, owing to reductions in cardiac preload and afterload. BNP, in particular, produces selective afferent arteriolar vasodilation and inhibits sodium reabsorption in the proximal convoluted tubule. It also inhibits renin and aldosterone release and, therefore, adrenergic activation. ANP and BNP are elevated in chronic heart failure. BNP, in particular, has potentially important diagnostic, therapeutic, and prognostic implications. For more information, see the Medscape Reference article Natriuretic Peptides in Congestive Heart Failure.

Other vasoactive systems Other vasoactive systems that play a role in the pathogenesis of heart failure include the ET receptor system, the adenosine receptor system, vasopressin, and tumor necrosis factor-alpha (TNF-alpha). [23] ET, a substance produced by the vascular endothelium, may contribute to the regulation of myocardial function, vascular tone, and peripheral resistance in heart failure. Elevated levels of ET-1 closely correlate with the severity of heart failure. ET-1 is a potent vasoconstrictor and has exaggerated vasoconstrictor effects in the renal vasculature, reducing renal plasma blood flow, glomerular filtration rate (GFR), and sodium excretion. TNF-alpha has been implicated in response to various infectious and inflammatory conditions. Elevations in TNF-alpha levels have been consistently observed in heart failure and seem to correlate with the degree of myocardial dysfunction. Some studies suggest that local production of TNF-alpha may have toxic effects on the myocardium, thus worsening myocardial systolic and diastolic function. In individuals with systolic dysfunction, therefore, the neurohormonal responses to decreased stroke volume result in temporary improvement in systolic blood pressure and tissue perfusion. However, in all circumstances, the existing data the notion that these neurohormonal responses contribute to the progression of myocardial dysfunction in the long term.

Heart failure with normal ejection fraction In diastolic heart failure (heart failure with normal ejection fraction [HFNEF]), the same pathophysiologic processes occur that lead to decreased cardiac output in systolic heart failure, but they do so in response to a different set of hemodynamic and circulatory environmental factors that depress cardiac output. [24]

In HFNEF, altered relaxation and increased stiffness of the ventricle (due to delayed calcium uptake by the myocyte sarcoplasmic reticulum and delayed calcium efflux from the myocyte) occur in response to an increase in ventricular afterload (pressure overload). The impaired relaxation of the ventricle then leads to impaired diastolic filling of the left ventricle (LV). Morris et al found that RV subendocardial systolic dysfunction and diastolic dysfunction, as detected by echocardiographic strain rate imaging, are common in patients with HFNEF. This dysfunction is potentially associated with the same fibrotic processes that affect the subendocardial layer of the LV and, to a lesser extent, with RV pressure overload. This may play a role in the symptomatology of patients with HFNEF.[25]

LV chamber stiffness An increase in LV chamber stiffness occurs secondary to any one of, or any combination of, the following 3 mechanisms:   

Rise in filling pressure Shift to a steeper ventricular pressure-volume curve Decrease in ventricular distensibility A rise in filling pressure is the movement of the ventricle up along its pressure-volume curve to a steeper portion, as may occur in conditions such as volume overload secondary to acute valvular regurgitation or acute LV failure due to myocarditis. A shift to a steeper ventricular pressure-volume curve results, most commonly, not only from increased ventricular mass and wall thickness (as observed in aortic stenosis and long-standing hypertension) but also from infiltrative disorders (eg, amyloidosis), endomyocardial fibrosis, and myocardial ischemia. Parallel upward displacement of the diastolic pressure-volume curve is generally referred to as a decrease in ventricular distensibility. This is usually caused by extrinsic compression of the ventricles.

Concentric LV hypertrophy Pressure overload that leads to concentric LV hypertrophy (LVH), as occurs in aortic stenosis, hypertension, and hypertrophic cardiomyopathy, shifts the diastolic pressure-volume curve to the left along its volume axis. As a result, ventricular diastolic pressure is abnormally elevated, although chamber stiffness may or may not be altered. Increases in diastolic pressure lead to increased myocardial energy expenditure, remodeling of the ventricle, increased myocardial oxygen demand, myocardial ischemia, and eventual progression of the maladaptive mechanisms of the heart that lead to decompensated heart failure.

Arrhythmias While life-threatening rhythms are more common in ischemic cardiomyopathy, arrhythmia imparts a significant burden in all forms of heart failure. In fact, some arrhythmias even perpetuate heart failure. The most significant of all rhythms associated with heart failure are the life-threatening ventricular arrhythmias. Structural substrates for ventricular arrhythmias that are common in heart failure, regardless of the underlying cause, include ventricular dilatation, myocardial hypertrophy, and myocardial fibrosis. At the cellular level, myocytes may be exposed to increased stretch, wall tension, catecholamines, ischemia, and electrolyte imbalance. The combination of these factors contributes to an increased incidence of arrhythmogenic sudden cardiac death in patients with heart failure.

Etiology Most patients who present with significant heart failure do so because of an inability to provide adequate cardiac output in that setting. This is often a combination of the causes listed below in the setting of an abnormal myocardium. The list of causes responsible for presentation of a patient with heart failure exacerbation is very long, and searching for the proximate cause to optimize therapeutic interventions is important. From a clinical standpoint, classifying the causes of heart failure into the following 4 broad categories is useful:    

Underlying causes: Underlying causes of heart failure include structural abnormalities (congenital or acquired) that affect the peripheral and coronary arterial circulation, pericardium, myocardium, or cardiac valves, thus leading to increased hemodynamic burden or myocardial or coronary insufficiency Fundamental causes: Fundamental causes include the biochemical and physiologic mechanisms, through which either an increased hemodynamic burden or a reduction in oxygen delivery to the myocardium results in impairment of myocardial contraction Precipitating causes: Overt heart failure may be precipitated by progression of the underlying heart disease (eg, further narrowing of a stenotic aortic valve or mitral valve) or various conditions (fever, anemia, infection) or medications (chemotherapy, NSAIDs) that alter the homeostasis of heart failure patients Genetics of cardiomyopathy: Dilated, arrhythmic right ventricular and restrictive cardiomyopathies are known genetic causes of heart failure.

Underlying causes

Specific underlying factors cause various forms of heart failure, such as systolic heart failure (most commonly, left ventricular systolic dysfunction), heart failure with preserved LVEF, acute heart failure, high-output heart failure, and right heart failure. Underlying causes of systolic heart failure include the following:         

Coronary artery disease Diabetes mellitus Hypertension Valvular heart disease (stenosis or regurgitant lesions) Arrhythmia (supraventricular or ventricular) Infections and inflammation (myocarditis) Peripartum cardiomyopathy Congenital heart disease Drugs (either recreational, such as alcohol and cocaine, or therapeutic drugs with cardiac side effects, such as doxorubicin)  Idiopathic cardiomyopathy  Rare conditions (endocrine abnormalities, rheumatologic disease, neuromuscular conditions) Underlying causes of diastolic heart failure include the following:       

Coronary artery disease Diabetes mellitus Hypertension Valvular heart disease (aortic stenosis) Hypertrophic cardiomyopathy Restrictive cardiomyopathy (amyloidosis, sarcoidosis) Constrictive pericarditis Underlying causes of acute heart failure include the following:

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Acute valvular (mitral or aortic) regurgitation Myocardial infarction Myocarditis Arrhythmia Drugs (eg, cocaine, calcium channel blockers, or beta-blocker overdose) Sepsis Underlying causes of high-output heart failure include the following:

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Anemia Systemic arteriovenous fistulas Hyperthyroidism Beriberi heart disease Paget disease of bone Albright syndrome (fibrous dysplasia) Multiple myeloma Pregnancy Glomerulonephritis Polycythemia vera Carcinoid syndrome Underlying causes of right heart failure include the following:

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Left ventricular failure Coronary artery disease (ischemia) Pulmonary hypertension Pulmonary valve stenosis Pulmonary embolism Chronic pulmonary disease Neuromuscular disease

Precipitating causes of heart failure A previously stable, compensated patient may develop heart failure that is clinically apparent for the first time when the intrinsic process has advanced to a critical point, such as with further narrowing of a stenotic aortic valve or mitral valve. Alternatively, decompensation may occur as a result of failure or exhaustion of the compensatory mechanisms but without any change in the load on the heart in patients with persistent, severe pressure or volume overload. In particular, consider whether the patient has underlying coronary artery disease or valvular heart disease. The most common cause of decompensation in a previously compensated patient with heart failure is inappropriate reduction in the intensity of treatment, such as dietary sodium restriction, physical activity reduction, or drug regimen

reduction. Uncontrolled hypertension is the second most common cause of decompensation, followed closely by cardiac arrhythmias (most commonly, atrial fibrillation). Arrhythmias, particularly ventricular arrhythmias, can be life threatening. Also, patients with one form of underlying heart disease that may be well compensated can develop heart failure when a second form of heart disease ensues. For example, a patient with chronic hypertension and asymptomatic LVH may be asymptomatic until a myocardial infarction (MI) develops and precipitates heart failure. Systemic infection or the development of unrelated illness can also lead to heart failure. Systemic infection precipitates heart failure by increasing total metabolism as a consequence of fever, discomfort, and cough, increasing the hemodynamic burden on the heart. Septic shock, in particular, can precipitate heart failure by the release of endotoxin-induced factors that can depress myocardial contractility. Cardiac infection and inflammation can also endanger the heart. Myocarditis or infective endocarditis may directly impair myocardial function and exacerbate existing heart disease. The anemia, fever, and tachycardia that frequently accompany these processes are also deleterious. In the case of infective endocarditis, the additional valvular damage that ensues may precipitate cardiac decompensation. Patients with heart failure, particularly when confined to bed, are at high risk of developing pulmonary emboli, which can increase the hemodynamic burden on the right ventricle by further elevating right ventricular (RV) systolic pressure, possibly causing fever, tachypnea, and tachycardia. Intense, prolonged physical exertion or severe fatigue, such as may result from prolonged travel or emotional crisis, is a relatively common precipitant of cardiac decompensation. The same is true of exposure to severe climate change (ie, the individual comes in with a hot, humid environment or a bitterly cold one). Excessive intake of water and/or sodium and the istration of cardiac depressants or drugs that cause salt retention are other factors that can lead to heart failure. Because of increased myocardial oxygen consumption and demand beyond a critical level, the following high-output states can precipitate the clinical presentation of heart failure:             

Profound anemia Thyrotoxicosis Myxedema Paget disease of bone Albright syndrome Multiple myeloma Glomerulonephritis Cor pulmonale Polycythemia vera Obesity Carcinoid syndrome Pregnancy Nutritional deficiencies (eg, thiamine deficiency, beriberi) Longitudinal data from the Framingham Heart Study suggests that antecedent subclinical left ventricular systolic or diastolic dysfunction is associated with an increased incidence of heart failure, ing the notion that heart failure is a progressive syndrome.[26, 27] Another analysis of over 36,000 patients undergoing outpatient echocardiography reported that moderate or severe diastolic dysfunction, but not mild diastolic dysfunction, is an independent predictor of mortality. [28]

Genetics of cardiomyopathy Autosomal dominant inheritance has been demonstrated in dilated cardiomyopathy and in arrhythmic right ventricular cardiomyopathy. Restrictive cardiomyopathies are usually sporadic and associated with the gene for cardiac troponin I. Genetic tests are available at major genetic centers for cardiomyopathies. [29] In families with a first-degree relative who has been diagnosed with a cardiomyopathy leading to heart failure, the at-risk patient should be screened and followed.[29] The recommended screening consists of an electrocardiogram and an echocardiogram. If the patient has an asymptomatic left ventricular dysfunction, it should be treated. [29]

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Heart Failure