What is the definition, causes, classification, and management of heart failure according to the most updated guidelines?

Heart Failure: Definition, Causes, Classification, and Management

Heart failure is a clinical syndrome characterized by typical symptoms (breathlessness, fatigue, ankle swelling) AND objective evidence of structural or functional cardiac abnormality that impairs the ventricle's ability to fill with or eject blood, resulting in reduced cardiac output and/or elevated intracardiac pressures. 1, 2

Definition

Heart failure requires both clinical manifestations and demonstrable cardiac dysfunction 3, 1:

• Cardinal symptoms: Dyspnea (at rest or on exertion), fatigue, and peripheral edema 3, 2
• Physical signs: Elevated jugular venous pressure, pulmonary crackles (rales), pleural effusion, peripheral edema, hepatomegaly, tachycardia, and third heart sound 1, 2
• Objective cardiac abnormality: Must demonstrate structural or functional myocardial abnormality through echocardiography, elevated natriuretic peptides (BNP/NT-proBNP), abnormal ECG, or cardiac murmurs 1

Important caveat: The term "heart failure" is preferred over "congestive heart failure" because not all patients present with volume overload—some have primarily exercise intolerance with minimal fluid retention 3.

Causes and Etiology

Coronary artery disease accounts for approximately two-thirds of heart failure cases with left ventricular systolic dysfunction 3:

Primary Causes:

• Ischemic heart disease: Most common cause in Western populations 3
• Hypertension: Major preventable cause 3
• Dilated cardiomyopathy: Up to 30% may have genetic etiology 3
• Valvular heart disease: Remains common, particularly mitral regurgitation 3

Other Identifiable Causes:

• Myocardial toxins (alcohol, chemotherapy agents) 3
• Myocarditis 3
• Thyroid disease 3
• Idiopathic dilated cardiomyopathy 3

Classification Systems

1. Classification by Left Ventricular Ejection Fraction (LVEF)

The European Society of Cardiology and American Heart Association classify heart failure into three categories based on LVEF 1, 2:

• HFrEF (Heart Failure with Reduced Ejection Fraction): LVEF ≤40% 1, 2
• HFmrEF (Heart Failure with Mid-range Ejection Fraction): LVEF 41-49% 1, 2
• HFpEF (Heart Failure with Preserved Ejection Fraction): LVEF ≥50% 1, 2

Critical distinction: Patients with normal or preserved LVEF may have severe disability, while those with very low ejection fraction may be asymptomatic—there is poor correlation between systolic dysfunction severity and functional impairment 3.

2. NYHA Functional Classification

The New York Heart Association classification quantifies symptom severity and functional limitation 3, 1, 2:

• Class I: No limitation of physical activity; ordinary activity does not cause undue fatigue, dyspnea, or palpitations 3
• Class II: Slight limitation; comfortable at rest but ordinary activity results in symptoms 3
• Class III: Marked limitation; comfortable at rest but less than ordinary activity causes symptoms 3
• Class IV: Unable to carry out any physical activity without discomfort; symptoms present even at rest 3

3. ACC/AHA Staging System

This progressive staging system complements NYHA classification and emphasizes prevention 3:

• Stage A: At risk for heart failure but no structural heart disease or symptoms
• Stage B: Structural heart disease but no symptoms (asymptomatic left ventricular dysfunction)
• Stage C: Structural heart disease with prior or current symptoms
• Stage D: Refractory heart failure requiring specialized interventions

Key principle: Patients advance through stages and cannot regress (unlike NYHA class which fluctuates with treatment), making this useful for guiding stage-specific therapies 3.

Diagnostic Approach

Essential Diagnostic Tests:

• Electrocardiogram: A normal ECG makes heart failure, especially systolic dysfunction, unlikely 3, 1
• Natriuretic peptides (BNP/NT-proBNP): Low-normal concentrations in untreated patients make heart failure unlikely 3, 1
• Echocardiography: Gold standard for confirming diagnosis and determining LVEF category 2
• Laboratory assessment: Renal function, electrolytes, complete blood count 2

Management

Prevention (Primary Objective)

Prevention of heart failure should always be the primary objective, particularly in patients with hypertension and coronary artery disease 3:

• Aggressive treatment of hypertension and coronary disease delays or prevents ventricular dysfunction and heart failure (Class I, Level A) 3
• Remove or treat underlying causes when possible: ischemia, toxic substances, alcohol, thyroid disease 3

Pharmacological Management for HFrEF

Core quadruple therapy for HFrEF includes 2:

1. ACE inhibitors/ARBs/ARNIs: First-line for mortality reduction 2
2. Beta-blockers: Essential for reducing mortality and hospitalizations 2
3. Mineralocorticoid receptor antagonists (MRAs): Proven mortality benefit 2
4. SGLT2 inhibitors: Newer addition with proven mortality benefit 2

Diuretics are essential for symptomatic relief of fluid overload but do not improve mortality 3, 2.

Non-Pharmacological Management

Lifestyle modifications and patient education are crucial 3, 2:

• Sodium restriction: More important in advanced than mild heart failure 3
• Fluid restriction: 1.5-2 L/day in advanced heart failure 3
• Alcohol: Moderate intake (1 beer or 1-2 glasses wine/day) permitted except in alcoholic cardiomyopathy where it is prohibited 3
• Daily weight monitoring: Report weight gains >2 kg in 3 days 2
• Exercise training: Improves skeletal muscle function and functional capacity in stable NYHA class II-III patients 3, 2
• Rest: Physical or bed rest recommended in acute heart failure or destabilization 3

Drugs to Avoid

The following medications should be avoided or used with extreme caution 3:

• NSAIDs and COX-2 inhibitors 3
• Class I antiarrhythmic agents 3
• Calcium antagonists (verapamil, diltiazem, short-acting dihydropyridines) 3
• Tricyclic antidepressants 3
• Corticosteroids 3
• Lithium 3

Device and Surgical Interventions

Consider for appropriate candidates 3:

• Biventricular (cardiac resynchronization) pacing 3
• Implantable cardioverter-defibrillator (ICD) 3
• Revascularization (catheter interventions and/or surgery) 3
• Mitral valve repair 3
• Mechanical circulatory support for refractory heart failure 2
• Heart transplantation, ventricular assist devices 3

Follow-up and Monitoring

Structured follow-up is essential for optimal outcomes 2:

• Schedule early follow-up within 7-14 days after hospital discharge 2
• Implement multidisciplinary heart failure disease-management programs 2
• Monitor renal function and electrolytes regularly, especially after medication changes 2
• Before discharge, ensure acute episode resolved, congestion absent, and stable oral diuretic regimen established for at least 48 hours 2

Advanced Heart Failure (Stage D)

For refractory symptoms despite optimal medical therapy 2:

• Consider mechanical circulatory support 2
• Palliative care consultation to improve quality of life 2

Pathophysiology and Prognosis

Heart failure is a progressive disease characterized by ventricular remodeling 3:

• Remodeling involves chamber dilation, hypertrophy, and increased sphericity 3
• This process precedes symptoms by months or years and continues after symptom onset 3
• Despite improved mortality with modern therapy, heart failure carries a 50% five-year mortality 4

Common pitfall: Clinicians often fail to appreciate the progressive nature of left ventricular dysfunction, missing opportunities for early intervention and prevention 3.