Diagnostic Evaluation of Heart Failure

Heart failure (HF) is a clinical syndrome characterized by the heart’s inability to pump sufficient blood to meet the body’s metabolic demands or to do so only at the expense of elevated filling pressures. It is not a single disease but rather the final common pathway of a wide range of cardiovascular disorders such as ischemic heart disease, hypertension, cardiomyopathies, and valvular heart diseases.

Accurate and timely diagnosis of heart failure is essential because it guides treatment, improves prognosis, and prevents progression of the disease. However, diagnosing HF can be challenging, especially in its early stages, because symptoms are often nonspecific and overlap with other conditions such as lung disease or anemia.

The diagnostic evaluation of heart failure relies on a combination of:

Clinical history and physical examination
Electrocardiography (ECG), chest X-ray, and blood biomarkers
Imaging techniques such as echocardiography and cardiac MRI

This article explores each of these components in detail, emphasizing their diagnostic value, limitations, and integration into clinical decision-making.

1. History and Clinical Examination

The cornerstone of heart failure diagnosis begins with a thorough patient history and physical examination. These tools provide critical insight into the onset, progression, and severity of the disease.

A. Patient History

Key historical elements include:

Symptoms of heart failure
- Dyspnea (shortness of breath): One of the most common symptoms. Patients often experience exertional dyspnea early, progressing to dyspnea at rest in advanced disease.
- Orthopnea: Difficulty breathing when lying flat, often requiring patients to use multiple pillows at night.
- Paroxysmal nocturnal dyspnea (PND): Sudden episodes of breathlessness at night that awaken the patient.
- Fatigue and weakness: Result from poor cardiac output and tissue hypoperfusion.
- Edema and weight gain: Fluid accumulation in the legs, ankles, and abdomen due to increased venous pressures.
- Cough or wheezing: Often worse at night, sometimes associated with pink frothy sputum in pulmonary edema.
Risk factors and comorbidities
- Hypertension, diabetes mellitus, hyperlipidemia, obesity, smoking, and family history of cardiomyopathy.
- Past history of myocardial infarction, valvular disease, or myocarditis.
Functional status
- Classification using the New York Heart Association (NYHA) functional scale:
  - Class I: No limitation of physical activity.
  - Class II: Mild limitation.
  - Class III: Marked limitation.
  - Class IV: Symptoms at rest.

This classification provides both diagnostic and prognostic information.

B. Physical Examination

The physical exam helps detect congestive features and signs of impaired perfusion. Important findings include:

Vital signs
- Tachycardia, tachypnea, low oxygen saturation.
- Blood pressure may be low (in advanced HF) or high (in hypertensive HF).
General appearance
- Cachexia (advanced disease), cyanosis, or diaphoresis.
Neck examination
- Jugular venous distension (JVD): Reflects elevated right atrial pressure.
- Hepatojugular reflux: A sustained rise in JVP with abdominal pressure.
Chest and lung findings
- Crackles/rales in the lung bases from pulmonary edema.
- Pleural effusion may also be present.
Cardiac examination
- Displaced and diffuse apical impulse (LV enlargement).
- S3 gallop: Early diastolic sound, highly suggestive of systolic HF.
- S4 sound: Reflects stiff ventricles, common in diastolic dysfunction.
- Murmurs: Indicate associated valvular disease (e.g., mitral regurgitation).
Peripheral examination
- Edema (ankle, sacral, or ascites in severe cases).
- Cold extremities and weak pulses (low output).
- Hepatomegaly due to venous congestion.

While physical signs are invaluable, they can be nonspecific. Hence, further diagnostic testing is crucial.

2. ECG, Chest X-Ray, and Blood Tests

A. Electrocardiography (ECG)

ECG is not diagnostic of heart failure per se, but it provides clues to underlying causes and complications.

Findings in HF:
- Left ventricular hypertrophy (LVH) due to chronic hypertension.
- Q waves suggest prior myocardial infarction.
- ST-T changes suggest ischemia.
- Arrhythmias: Atrial fibrillation, ventricular tachycardia.
- Bundle branch blocks (especially LBBB), which may worsen systolic function.

A normal ECG makes significant systolic HF less likely. Thus, ECG is a valuable screening tool.

B. Chest X-Ray

A chest X-ray is a simple, quick test that evaluates cardiac size and pulmonary congestion.

Cardiomegaly: Enlarged cardiac silhouette indicates LV dilatation.
Pulmonary venous congestion: Redistribution of blood flow to the upper lobes.
Interstitial edema: Kerley B lines (thin horizontal lines at lung bases).
Alveolar edema: “Bat-wing” pattern in severe pulmonary edema.
Pleural effusion: Common in advanced HF.

Limitations: X-rays may appear normal in early or compensated HF.

C. Blood Tests

1. Natriuretic peptides (BNP and NT-proBNP)

Released by ventricles in response to volume and pressure overload.
BNP > 100 pg/mL or NT-proBNP > 300 pg/mL strongly suggests HF.
Useful for:
- Differentiating cardiac vs non-cardiac dyspnea.
- Prognostic assessment.
- Monitoring treatment response.

2. Routine laboratory evaluation

Complete blood count (CBC): Anemia can worsen symptoms.
Renal function tests (BUN, creatinine): Important since renal impairment influences therapy.
Electrolytes (Na+, K+): Hyponatremia indicates severe HF; potassium abnormalities influence arrhythmia risk.
Liver function tests: Elevated in hepatic congestion.
Thyroid function tests: Thyroid disease can mimic or worsen HF.
Cardiac troponins: Elevated in ACS-related HF or ongoing myocardial injury.

These investigations help in both diagnosis and management decisions.

3. Echocardiography and Cardiac MRI

A. Echocardiography

Echocardiography is the gold standard imaging tool for HF evaluation due to its availability, non-invasiveness, and diagnostic accuracy.

Key roles:

Assessment of systolic function
- Left ventricular ejection fraction (LVEF):
  - HF with reduced EF (HFrEF): LVEF < 40%.
  - HF with preserved EF (HFpEF): LVEF ≥ 50%.
  - HF with mildly reduced EF (HFmrEF): LVEF 41–49%.
- Global and regional wall motion abnormalities.
Diastolic function
- Doppler studies assess LV filling pressures and relaxation abnormalities.
Chamber size and hypertrophy
- LV dilatation or concentric hypertrophy.
- Left atrial enlargement.
Valvular disease
- Mitral regurgitation, aortic stenosis/regurgitation, tricuspid regurgitation.
Right ventricular function
- RV size, TAPSE (tricuspid annular plane systolic excursion).
Pericardial disease
- Detection of pericardial effusion and constrictive physiology.

Echocardiography is often repeated to monitor progression and guide therapy.

B. Cardiac Magnetic Resonance Imaging (MRI)

Cardiac MRI provides superior structural and tissue characterization. It is especially useful in:

Quantification of ventricular volumes and function: More accurate than echo.
Myocardial tissue characterization:
- Late gadolinium enhancement (LGE): Detects fibrosis, scar tissue (ischemic vs non-ischemic cardiomyopathy).
- Edema imaging: Useful in myocarditis.
Assessment of infiltrative diseases: Amyloidosis, sarcoidosis, hemochromatosis.
Congenital abnormalities and complex structural heart disease.

Limitations: Availability, cost, and contraindications (e.g., certain implanted devices).

Integration of Diagnostic Tools

A practical diagnostic approach usually proceeds as follows:

Clinical suspicion from history and examination.
Initial tests: ECG, chest X-ray, blood tests including BNP.
Definitive assessment: Echocardiography for function, structure, and etiology.
Advanced imaging (MRI, CT): In selected cases for further clarification.