How is heart disease classified?

Heart Disease Classification

Heart disease is classified using multiple complementary systems: the ACC/AHA staging system (Stages A-D) for disease progression, the NYHA functional classification (Classes I-IV) for symptom severity, and anatomic classifications specific to the type of heart disease (congenital, valvular, ischemic, or cardiomyopathy). 1, 2

ACC/AHA Staging System for Heart Failure

The American College of Cardiology and American Heart Association developed a four-stage classification that emphasizes disease evolution and progression 1, 2:

• Stage A: Patients at high risk for developing heart failure but without structural heart disorder (e.g., hypertension, diabetes, coronary artery disease risk factors) 1, 2
• Stage B: Patients with structural heart disorder but who have never developed symptoms of heart failure (e.g., previous myocardial infarction, left ventricular hypertrophy, asymptomatic valvular disease) 1, 2
• Stage C: Patients with past or current symptoms of heart failure associated with underlying structural heart disease 1, 2
• Stage D: Patients with end-stage disease requiring specialized treatment strategies such as mechanical circulatory support, continuous inotropic infusions, cardiac transplantation, or hospice care 1, 2

This staging system is designed to complement, not replace, the NYHA functional classification, and patients are expected to advance from one stage to the next unless disease progression is slowed or stopped by treatment. 1

NYHA Functional Classification

The New York Heart Association classification grades symptom severity in patients with heart failure 1, 3, 2:

• Class I: No limitation of physical activity; ordinary physical activity does not cause undue fatigue, palpitation, or dyspnea 3, 2
• Class II: Slight limitation of physical activity; comfortable at rest but ordinary physical activity results in fatigue, palpitation, or dyspnea 3, 2
• Class III: Marked limitation of physical activity; comfortable at rest but less than ordinary activity causes fatigue, palpitation, or dyspnea 3, 2
• Class IV: Unable to carry on any physical activity without discomfort; symptoms of heart failure at rest 3, 2

The NYHA classification reflects a subjective assessment by a physician and changes frequently over short periods of time, which is why the ACC/AHA staging system was developed to provide more objective disease stratification. 1

Classification by Left Ventricular Ejection Fraction

Heart failure is further classified based on left ventricular ejection fraction (LVEF) 2:

• HFrEF (Heart Failure with Reduced Ejection Fraction): LVEF <40% 2
• HFmrEF (Heart Failure with Mildly Reduced Ejection Fraction): LVEF 41-49% 2
• HFpEF (Heart Failure with Preserved Ejection Fraction): LVEF ≥50% 2

Congenital Heart Disease Classification

The 2018 AHA/ACC guidelines classify adult congenital heart disease (ACHD) using an anatomic and physiological (AP) classification system 1:

Anatomic Classification

Patients are classified based on the "highest" relevant anatomic or physiological feature present 1:

• Class I (Simple): Isolated small ASD, isolated small VSD, mild isolated pulmonic stenosis, previously ligated or occluded ductus arteriosus, repaired secundum ASD or VSD without significant residual shunt or chamber enlargement 1

• Class II (Moderate Complexity): Aorto-left ventricular fistula, anomalous pulmonary venous connection, atrioventricular septal defects, congenital aortic or mitral valve disease, coarctation of the aorta, Ebstein anomaly, moderate-to-large unrepaired ASD or PDA, repaired tetralogy of Fallot, moderate or greater pulmonary valve regurgitation or stenosis 1

• Class III (Great Complexity/Complex): Cyanotic congenital heart defects (unrepaired or palliated), double-outlet ventricle, Fontan procedure, interrupted aortic arch, mitral atresia, single ventricle (including hypoplastic left heart), pulmonary atresia, transposition of the great arteries (d-TGA or l-TGA), truncus arteriosus 1

Physiological Stage Classification

The physiological stage is combined with anatomic classification to determine overall ACHD AP classification 1:

• Stage A: NYHA functional class I symptoms, no hemodynamic or anatomic sequelae 1
• Stage B: Mild hemodynamic sequelae (mild ventricular dysfunction, mild valvular disease) 1
• Stage C: Moderate-to-severe hemodynamic sequelae requiring intervention 1

For example, a normotensive patient with repaired coarctation of the aorta, normal exercise capacity, and normal end-organ function would be ACHD AP classification IIA, whereas a similar patient with ascending aortic diameter of 4.0 cm would be IIB, and if moderate aortic stenosis were also present, the classification would be IIC. 1

Cardiomyopathy Classification

The American Heart Association classifies cardiomyopathies into distinct morphological and functional phenotypes 4:

• Dilated cardiomyopathy: Characterized by severe systolic failure progressing to congestive heart failure 4, 5
• Hypertrophic cardiomyopathy: Notable for massive ventricular hypertrophy without obvious cause, impaired diastolic and systolic function, tendency for sudden death, and familial propensity 4, 5
• Restrictive cardiomyopathy: Demonstrates restriction to ventricular filling due to restrictive forces in the endomyocardium 4, 5
• Arrhythmogenic right ventricular cardiomyopathy 4
• Inflammatory cardiomyopathy 4

Cardiomyopathies are further subdivided into primary cardiomyopathies (genetic, nongenetic, and acquired) and secondary cardiomyopathies (myocardial involvement as part of systemic disorders). 4

Acute Heart Failure Classifications

Killip Classification

The Killip classification provides clinical estimation of circulatory impairment severity in acute myocardial infarction 2:

• Class I: No heart failure 2
• Class II: Heart failure with rales and S3 gallop 2
• Class III: Severe heart failure with pulmonary edema 2
• Class IV: Cardiogenic shock 2

Forrester Classification

The Forrester classification describes clinical and hemodynamic state based on perfusion and pulmonary capillary wedge pressure (PCWP) in acute myocardial infarction 2.

European Society of Cardiology Clinical Presentations

The ESC identifies six distinct presentations of acute decompensated heart failure: acute decompensated heart failure, hypertensive heart failure, pulmonary edema, cardiogenic shock, high-output failure, and right-sided heart failure 2.

Valvular Heart Disease Classification

Valvular heart disease is classified by the affected valve (aortic, mitral, tricuspid, or pulmonary) and the type of dysfunction (stenosis or regurgitation), with severity graded as mild, moderate, or severe 6.

Congenital Heart Disease Pathophysiological Classification

An alternative pathophysiological classification divides congenital heart defects based on clinical consequences 7:

• CHD with increased pulmonary blood flow: Septal defects without pulmonary obstruction and with left-to-right shunt 7
• CHD with decreased pulmonary flow: Septal defects with pulmonary obstruction and with right-to-left shunt 7
• CHD with obstruction to blood progression and no septal defects: No shunt present 7
• CHD incompatible with postnatal blood circulation 7
• CHD silent until adult age 7

Pulmonary Arterial Hypertension in Congenital Heart Disease

CHD-related pulmonary arterial hypertension (CHD-PAH) is categorized as a unique entity with specific subcategories 1:

• Dynamic PAH: Related to high shunt flow that responds to reduction of the shunt 1
• Immediate postoperative or "reactive" PAH 1
• Late postoperative PAH 1
• Secondary to lesions causing pulmonary venous hypertension 1
• Shunt reversal (Eisenmenger physiology) 1

PAH is hemodynamically defined as mean pulmonary artery pressure ≥25 mm Hg at rest, pulmonary capillary wedge pressure ≤15 mm Hg, and pulmonary vascular resistance ≥3 Wood units. 1

Clinical Application

When classifying a patient with heart disease, use the ACC/AHA staging system to determine disease progression, the NYHA classification to assess current symptom severity, and the appropriate anatomic classification based on the specific type of heart disease present. 1, 3, 2 These systems work together to guide treatment decisions, with the ACC/AHA stages linked to specific therapeutic interventions appropriate at each stage of illness. 1