Heart Failure

Heart failure is a clinical syndrome resulting from structural or functional abnormalities that impair the ability of the heart to fill with blood, eject blood, or both. The resulting cardiovascular dysfunction can produce inadequate tissue perfusion, elevated intracardiac pressures, pulmonary congestion, systemic venous congestion, or combinations of these abnormalities.

Heart failure is not a single anatomical lesion. It can develop from diseases affecting the myocardium, cardiac valves, coronary circulation, pericardium, conduction system, or the pressure and volume loads imposed on the heart.

The syndrome may predominantly involve the left ventricle, right ventricle, or both ventricles. It may also occur with reduced ventricular contractile function or despite a relatively preserved left ventricular ejection fraction.

Normal Cardiac Pump Function

The heart functions as two coordinated pumps arranged in series. The right ventricle sends systemic venous blood through the pulmonary circulation, while the left ventricle receives pulmonary venous blood and ejects it into the systemic circulation.

Effective circulation depends on adequate ventricular filling, coordinated myocardial contraction, competent valves, appropriate heart rate and rhythm, and suitable vascular resistance.

Cardiac Output

Cardiac output is the volume of blood pumped by a ventricle per unit time.

It is determined by heart rate and stroke volume:

Cardiac Output = Heart Rate × Stroke Volume

Heart failure can impair cardiac output by reducing stroke volume, disrupting ventricular filling, altering heart rate or rhythm, or producing several of these abnormalities simultaneously.

Stroke Volume

Stroke volume is the amount of blood ejected by a ventricle during a single contraction.

It is influenced by preload, myocardial contractility, afterload, ventricular geometry, and valve function.

Ejection Fraction

Ejection fraction (EF) represents the proportion of end-diastolic ventricular volume ejected during systole.

It is commonly used to characterize left ventricular systolic function and to classify major heart failure phenotypes.

Major Heart Failure Categories

Category	General Feature
Heart failure with reduced ejection fraction	Impaired left ventricular systolic contraction with reduced ejection fraction
Heart failure with mildly reduced ejection fraction	Ejection fraction lies between typical reduced and preserved ranges
Heart failure with preserved ejection fraction	Clinical heart failure despite relatively preserved ejection fraction, commonly with abnormal ventricular filling and elevated filling pressures

Heart Failure With Reduced Ejection Fraction

Heart failure with reduced ejection fraction (HFrEF) is associated with impaired systolic ventricular performance.

The left ventricle does not eject a normal proportion of its end-diastolic volume, and ventricular dilation and remodeling may develop.

Systolic Dysfunction

Systolic dysfunction refers to impaired ability of the ventricle to contract and eject blood effectively.

Myocardial injury, dilated cardiomyopathy, chronic pressure or volume stress, and other abnormalities can reduce contractile performance.

Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) occurs when symptoms and signs of heart failure develop despite a relatively preserved left ventricular ejection fraction.

Abnormal ventricular relaxation, increased myocardial stiffness, elevated filling pressures, vascular abnormalities, and systemic comorbidities can contribute to the syndrome.

Diastolic Dysfunction

Diastolic dysfunction refers to impaired ventricular relaxation, filling, or compliance.

A stiff ventricle may require higher filling pressures to achieve an adequate end-diastolic volume, contributing to upstream venous congestion.

Left-Sided Heart Failure

Left-sided heart failure occurs when the left ventricle cannot adequately accommodate or eject blood arriving from the pulmonary circulation.

Elevated left ventricular filling pressure can be transmitted backward through the left atrium into the pulmonary veins and pulmonary capillaries.

Pulmonary Venous Congestion

Increasing pressure within the left atrium and pulmonary veins raises hydrostatic pressure within the pulmonary microcirculation.

This promotes movement of fluid from pulmonary capillaries into the interstitial tissues and, when severe, into alveolar spaces.

Pulmonary Edema

Pulmonary edema is accumulation of excess fluid within pulmonary interstitial tissue and alveoli.

In left-sided heart failure, increased pulmonary capillary hydrostatic pressure is an important mechanism of cardiogenic pulmonary edema.

Effects of Pulmonary Congestion

Pulmonary congestion can interfere with normal lung mechanics and gas exchange.

Patients may develop shortness of breath, reduced exercise tolerance, orthopnea, or episodes of acute respiratory distress when congestion becomes severe.

Right-Sided Heart Failure

Right-sided heart failure occurs when the right ventricle cannot effectively accommodate or eject systemic venous return into the pulmonary circulation.

Right ventricular dysfunction can cause elevated right atrial and systemic venous pressures.

Systemic Venous Congestion

Elevated right-sided filling pressures are transmitted backward into the systemic venous circulation.

This can produce distension of systemic veins and increased hydrostatic pressure in peripheral and visceral venous beds.

Peripheral Edema

Increased systemic venous and capillary hydrostatic pressure promotes accumulation of interstitial fluid.

Dependent peripheral edema is therefore a common manifestation of right-sided or biventricular heart failure.

Jugular Venous Distension

Elevated right atrial pressure can be reflected in the jugular venous system.

Visible elevation of jugular venous pressure provides a clinical indication of increased right-sided filling pressure.

Hepatic Congestion

Systemic venous congestion can extend into the hepatic veins and liver.

Persistent elevation of venous pressure can produce hepatomegaly, hepatic congestion, and abnormalities of liver function.

Ascites

Severe systemic venous congestion can contribute to accumulation of fluid within the peritoneal cavity, producing ascites.

Changes in renal sodium and water handling can further promote fluid retention.

Biventricular Heart Failure

Many patients eventually develop abnormalities involving both ventricles.

Left-sided heart failure can increase pulmonary vascular pressures and impose an increased workload on the right ventricle, while diseases affecting both ventricles can cause simultaneous systemic and pulmonary congestion.

Common Causes of Heart Failure

Heart failure can result from numerous cardiovascular disorders that damage the myocardium or impose abnormal pressure or volume loads on the heart.

Cause	Potential Effect
Coronary artery disease	Myocardial ischemia and loss of functioning myocardium
Myocardial infarction	Permanent myocardial injury and ventricular remodeling
Hypertension	Chronic pressure overload and ventricular hypertrophy
Valvular heart disease	Pressure or volume overload
Cardiomyopathy	Primary impairment of myocardial structure or function
Arrhythmias	Abnormal rate or loss of coordinated contraction
Congenital heart disease	Abnormal loading conditions or structural circulation

Coronary Artery Disease

Coronary artery disease can impair myocardial function through chronic ischemia or myocardial infarction.

Loss of viable myocardium can reduce contractile function and initiate progressive ventricular remodeling.

Myocardial Infarction

Myocardial infarction causes irreversible death of cardiac muscle within the affected vascular territory.

Scar formation and changes in ventricular geometry can reduce pumping efficiency and increase stress on remaining myocardium.

Hypertension

Chronic systemic hypertension increases the pressure against which the left ventricle must eject blood.

The ventricle initially adapts through myocardial hypertrophy, but prolonged pressure overload can contribute to impaired relaxation, increased stiffness, dilation, and eventual heart failure.

Valvular Heart Disease

Valve stenosis and regurgitation can impose abnormal pressure or volume loads on cardiac chambers.

Chronic loading abnormalities can produce hypertrophy, dilation, elevated filling pressures, and progressive ventricular dysfunction.

Cardiomyopathy

Cardiomyopathies are diseases of the myocardium associated with structural or functional abnormalities.

Dilated, hypertrophic, restrictive, and other forms of cardiomyopathy can produce heart failure through different anatomical and physiological mechanisms.

Arrhythmias and Heart Failure

Persistent tachyarrhythmias can reduce ventricular filling and may impair myocardial function over time.

Severe bradyarrhythmias can reduce cardiac output, while loss of atrioventricular or ventricular synchrony can further decrease pumping efficiency.

Ventricular Remodeling

Ventricular remodeling describes changes in ventricular size, shape, wall thickness, and tissue composition that occur in response to injury or chronic hemodynamic stress.

Although some remodeling initially helps maintain cardiac output, progressive remodeling can worsen ventricular function.

Ventricular Dilation

In some forms of systolic heart failure, the ventricle enlarges and becomes more spherical.

Dilation can increase wall stress and alter the mechanical relationship between the ventricular myocardium and atrioventricular valve apparatus.

Ventricular Hypertrophy

Chronic pressure overload stimulates myocardial hypertrophy.

Increased wall thickness can initially reduce wall stress, but excessive hypertrophy may increase myocardial oxygen demand and impair ventricular compliance.

Myocardial Fibrosis

Fibrosis can accumulate within chronically stressed or injured myocardium.

Fibrotic tissue alters ventricular compliance and can disrupt normal electrical conduction as well as mechanical function.

Compensatory Mechanisms

When cardiac output falls, several physiological systems respond in an attempt to preserve arterial pressure and perfusion of vital organs.

Important compensatory responses include sympathetic nervous system activation, renin-angiotensin-aldosterone system activation, fluid retention, and structural remodeling.

Sympathetic Nervous System Activation

Reduced effective arterial perfusion activates sympathetic pathways.

Sympathetic stimulation increases heart rate and contractility and produces vasoconstriction, which can temporarily support blood pressure and cardiac output.

Long-Term Sympathetic Effects

Persistent sympathetic activation increases cardiac workload and can contribute to vasoconstriction, arrhythmias, myocardial injury, and progressive ventricular dysfunction.

Renin-Angiotensin-Aldosterone System

Reduced renal perfusion and neurohormonal signaling activate the renin-angiotensin-aldosterone system (RAAS).

Angiotensin II promotes vasoconstriction, while aldosterone contributes to sodium and water retention.

Fluid Retention

Retention of sodium and water can increase circulating volume and ventricular filling.

Although increased preload may initially support stroke volume, excessive volume retention contributes to pulmonary and systemic congestion.

Natriuretic Peptides

Increased myocardial wall stress promotes release of natriuretic peptides, including B-type natriuretic peptide (BNP) and related peptides.

These hormones promote natriuresis and vasodilation and oppose some effects of volume-retaining neurohormonal systems.

Frank-Starling Mechanism

Within physiological limits, increased ventricular filling stretches myocardial fibers and can increase the force of contraction.

In advanced heart failure, however, further increases in filling pressure may produce congestion with relatively little improvement in stroke volume.

Preload

Preload relates to ventricular filling and myocardial fiber stretch before contraction.

Excessive filling pressures are central to many manifestations of congestive heart failure.

Afterload

Afterload represents the load against which a ventricle must eject blood.

Systemic hypertension increases left ventricular afterload, while pulmonary hypertension increases right ventricular afterload.

Forward and Backward Effects

Heart failure can be understood partly in terms of reduced forward flow and increased pressures behind the failing chamber.

Reduced forward flow may impair tissue perfusion, while backward transmission of pressure produces pulmonary or systemic venous congestion.

Reduced Tissue Perfusion

When cardiac output becomes inadequate, blood flow to tissues can fall.

Fatigue, exercise intolerance, cool extremities, altered renal function, and impaired cerebral perfusion can occur in severe cases.

Renal Effects

Reduced renal perfusion and neurohormonal activation alter renal handling of sodium and water.

This can reinforce volume expansion and congestion, creating an important interaction between cardiac and renal dysfunction.

Acute Heart Failure

Acute heart failure refers to rapid development or worsening of heart failure signs and symptoms.

It can occur after acute myocardial injury, severe valve dysfunction, arrhythmia, abrupt pressure changes, or decompensation of chronic heart failure.

Chronic Heart Failure

Chronic heart failure develops or persists over an extended period.

Structural remodeling and neurohormonal adaptation can allow temporary compensation, but the syndrome may progressively worsen or periodically decompensate.

Compensated Heart Failure

In compensated heart failure, physiological adaptations allow the circulation to maintain relatively stable function despite underlying cardiac abnormalities.

Symptoms may be mild or controlled even though structural heart disease persists.

Decompensated Heart Failure

Decompensated heart failure occurs when compensatory mechanisms are no longer sufficient to maintain stable circulation or when a precipitating event causes deterioration.

Congestion, dyspnea, edema, or impaired perfusion may worsen rapidly.

Common Clinical Features

• Shortness of breath
• Reduced exercise tolerance
• Fatigue
• Orthopnea
• Peripheral edema
• Jugular venous distension
• Rapid weight gain from fluid retention
• Pulmonary crackles when pulmonary congestion is present

Dyspnea

Dyspnea is a common symptom of left-sided heart failure.

Elevated pulmonary venous pressure and interstitial pulmonary fluid can increase the work of breathing and interfere with normal pulmonary function.

Orthopnea

Orthopnea is shortness of breath that develops or worsens when lying flat.

Changes in venous return and redistribution of fluid toward the thorax can worsen pulmonary congestion in susceptible patients.

Paroxysmal Nocturnal Dyspnea

Paroxysmal nocturnal dyspnea refers to episodes of severe breathlessness that awaken a person from sleep.

It is associated with increased pulmonary congestion in the recumbent state and other physiological changes occurring during sleep.

Exercise Intolerance

Reduced cardiac reserve limits the ability to increase cardiac output during physical activity.

Abnormal skeletal muscle perfusion and systemic changes associated with chronic heart failure can further contribute to exercise intolerance.

Diagnostic Assessment

Assessment of suspected heart failure combines clinical evaluation with tests that examine cardiac structure, function, rhythm, hemodynamics, and potential underlying causes.

Echocardiography

Echocardiography is central to the anatomical and functional evaluation of heart failure.

It can assess ventricular size, wall thickness, systolic function, diastolic parameters, valve anatomy and function, atrial size, and other structural abnormalities.

Electrocardiography

An electrocardiogram can demonstrate arrhythmias, conduction abnormalities, evidence of previous myocardial injury, ventricular hypertrophy, and other electrical findings relevant to heart failure.

Chest Imaging

Chest imaging can demonstrate cardiac enlargement, pulmonary vascular congestion, pleural effusions, and pulmonary edema in appropriate clinical settings.

Natriuretic Peptide Testing

Measurement of BNP or N-terminal pro-BNP can provide information related to myocardial wall stress.

These biomarkers are interpreted together with clinical findings and other investigations.

Hemodynamic Assessment

Selected patients may undergo invasive measurement of intracardiac and pulmonary vascular pressures.

These measurements can help characterize filling pressures, cardiac output, and pulmonary vascular hemodynamics.

Clinical Significance

Pulmonary Edema

Acute elevation of left-sided filling pressure can cause rapid accumulation of fluid within the lungs.

Severe pulmonary edema can substantially impair oxygen exchange and respiratory function.

Cardiogenic Shock

Cardiogenic shock is severe circulatory failure caused by inadequate cardiac pump function.

Marked reduction in cardiac output leads to systemic hypotension and inadequate perfusion of vital organs.

Cardiorenal Interaction

Heart failure and kidney dysfunction can reinforce one another through changes in perfusion, venous pressure, neurohormonal activity, and fluid balance.

Arrhythmias

Structural remodeling, myocardial fibrosis, chamber dilation, ischemia, and neurohormonal changes can create a substrate for atrial and ventricular arrhythmias.

Arrhythmias can in turn worsen heart failure by reducing filling or coordinated cardiac contraction.

Functional Mitral Regurgitation

Left ventricular dilation and altered geometry can displace papillary muscles and enlarge the mitral annulus.

This can impair leaflet coaptation and produce secondary, or functional, mitral regurgitation even when the valve leaflets themselves are not primarily diseased.

Functional Tricuspid Regurgitation

Right ventricular and tricuspid annular dilation can produce secondary tricuspid regurgitation.

The resulting volume overload can further worsen right-sided chamber enlargement and systemic venous congestion.

General Treatment Principles

Management depends on the type and cause of heart failure, ejection fraction, symptoms, hemodynamic status, and associated cardiovascular conditions.

Strategies may include treatment of the underlying cause, reduction of congestion, modification of maladaptive neurohormonal pathways, management of blood pressure and rhythm, and use of devices or surgery in selected patients.

Diuretics

Diuretics increase renal excretion of sodium and water and can reduce intravascular volume and congestion.

They are commonly used to relieve symptoms related to pulmonary and systemic fluid accumulation.

Neurohormonal Therapy

Several classes of medications used in heart failure act on pathways involved in sympathetic activation, the renin-angiotensin-aldosterone system, or other mechanisms that contribute to disease progression.

The specific therapeutic approach differs among heart failure phenotypes and individual patients.

Cardiac Resynchronization Therapy

Cardiac resynchronization therapy (CRT) uses coordinated ventricular pacing in selected patients with heart failure and electrical conduction abnormalities.

Improved timing of ventricular activation can increase mechanical efficiency in appropriately selected patients.

Implantable Cardioverter-Defibrillators

Selected patients with significant ventricular dysfunction or other high-risk characteristics may receive an implantable cardioverter-defibrillator (ICD).

The device detects and treats certain dangerous ventricular tachyarrhythmias.

Mechanical Circulatory Support

Mechanical devices can assist cardiac pumping in selected patients with severe heart failure.

Examples include ventricular assist devices used as temporary support, a bridge to transplantation, or longer-term therapy in appropriate circumstances.

Heart Transplantation

Heart transplantation may be considered in selected patients with advanced heart failure that remains severe despite other therapies.

The procedure replaces the failing heart with a donor organ capable of restoring effective cardiac pumping.

Left-Sided Versus Right-Sided Heart Failure

Feature	Left-Sided Failure	Right-Sided Failure
Primary chamber	Left ventricle	Right ventricle
Upstream congestion	Pulmonary veins and capillaries	Systemic veins
Common manifestations	Dyspnea, pulmonary congestion, pulmonary edema
Venous findings	Elevated pulmonary venous pressure	Jugular venous distension and peripheral venous congestion
Fluid accumulation	Predominantly pulmonary	Peripheral edema, hepatic congestion and ascites

Major Pathophysiological Changes

Change	Potential Effect
Reduced contractility	Reduced stroke volume and ejection fraction
Reduced ventricular compliance	Elevated filling pressure and impaired diastolic filling
Ventricular remodeling	Altered chamber geometry and progressive dysfunction
Sympathetic activation	Increased heart rate, contractility and vasoconstriction
RAAS activation	Vasoconstriction and sodium and water retention
Elevated filling pressures	Pulmonary or systemic venous congestion
Reduced cardiac output	Impaired tissue perfusion and exercise capacity

Key Features of Heart Failure

Feature	Key Point
Definition	Clinical syndrome caused by structural or functional cardiac abnormalities that impair filling or ejection
Major chambers involved	Left ventricle, right ventricle, or both
Major physiological problems	Reduced cardiac output and elevated filling pressures
Left-sided congestion	Pulmonary circulation
Right-sided congestion	Systemic venous circulation
Major structural adaptation	Ventricular remodeling
Important compensatory systems	Sympathetic nervous system and RAAS
Central imaging test	Echocardiography

Anatomical and Physiological Importance

Heart failure demonstrates how closely cardiac structure and circulatory function are linked. Changes in myocardial thickness, ventricular dimensions, chamber compliance, valve geometry, and electrical activation can alter the ability of the heart to receive and eject blood.

The location of ventricular dysfunction determines many of the anatomical consequences. Left-sided dysfunction primarily raises pressure within the pulmonary venous circulation, while right-sided dysfunction primarily raises pressure within the systemic venous circulation. When both ventricles are affected, pulmonary and systemic congestion can occur simultaneously.

Compensatory responses initially help preserve circulation but can become maladaptive when chronically activated. Ventricular remodeling, neurohormonal activation, vasoconstriction, and fluid retention can progressively increase cardiac workload and congestion, creating a cycle in which structural and functional abnormalities reinforce one another.