What are the steps to diagnose heart failure?

Diagnosing Heart Failure: A Structured Approach

Begin with a detailed history and physical examination, followed by ECG and natriuretic peptide measurement, then proceed to echocardiography based on risk stratification—patients with prior myocardial infarction or elevated natriuretic peptides should receive echocardiography within 2 weeks. 1

Initial Clinical Assessment

History Elements with Proven Diagnostic Value

• Age, coronary artery disease history, and current loop diuretic use are the three historical factors with independent diagnostic value (combined c-statistic 0.83) 2
• Assess for dyspnea and fatigue, though these symptoms have poor specificity and correlation with severity 1
• Screen high-risk patients: those with coronary artery disease, hypertension, diabetes, cardiotoxic drug exposure, alcohol abuse, or family history of cardiomyopathy 3

Physical Examination Findings

Focus on six key findings with proven diagnostic value 2:

• Pulse rate and regularity
• Displaced apex beat
• Pulmonary rales
• Heart murmur
• Increased jugular venous pressure
• These physical findings combined with history achieve a c-statistic of 0.83 2

Essential Diagnostic Testing

Electrocardiogram (Critical Screening Tool)

• A normal ECG has >90% negative predictive value for excluding left ventricular systolic dysfunction 1
• Heart failure is highly unlikely with a normal ECG 1, 3
• An abnormal ECG warrants further investigation 1

Natriuretic Peptide Testing (Most Powerful Add-On Test)

Natriuretic peptide measurement provides the largest quantitative diagnostic contribution beyond history and physical examination, increasing diagnostic accuracy from c-statistic 0.83 to 0.86 with 69% net reclassification improvement 2

Interpret levels as follows 1:

• Normal (rules out heart failure): BNP <100 ng/L or NT-proBNP <400 ng/L
• Raised (intermediate risk): BNP 100-400 ng/L or NT-proBNP 400-2000 ng/L
• High (confirms high probability): BNP >400 ng/L or NT-proBNP >2000 ng/L

The ACC/AHA guidelines emphasize natriuretic peptides are most useful as a "rule out" test due to consistently high negative predictive values 1, 4

Chest Radiography

• Obtain chest X-ray to detect cardiomegaly and pulmonary congestion 1
• Has predictive value only in context of typical symptoms and abnormal ECG 1
• Heart failure is highly unlikely with a normal chest radiograph 3

Risk-Stratified Pathway to Echocardiography

Immediate Echocardiography (Within 2 Weeks)

Proceed directly to echocardiography for 1:

• Patients with prior myocardial infarction (bypass natriuretic peptide testing)
• Patients with high natriuretic peptide levels (BNP >400 ng/L or NT-proBNP >2000 ng/L)

Delayed Echocardiography (Within 6 Weeks)

For patients with 1:

• Raised natriuretic peptide levels (BNP 100-400 ng/L or NT-proBNP 400-2000 ng/L)

Echocardiography Findings Required for Diagnosis

Objective evidence of cardiac dysfunction at rest is necessary for diagnosis 1

The echocardiogram must assess 1:

• Left ventricular ejection fraction (most important parameter to distinguish systolic from preserved function)
• Valvular function
• Cardiac filling characteristics through Doppler measurements
• Etiology determination

Comprehensive Laboratory Evaluation

The ACC/AHA guidelines mandate the following initial laboratory panel 4:

• Complete blood count (identify anemia worsening symptoms)
• Serum electrolytes including sodium, potassium, calcium, and magnesium
• Renal function tests (BUN and creatinine for medication dosing and prognosis)
• Fasting blood glucose or glycohemoglobin
• Lipid profile
• Liver function tests (detect hepatic congestion)
• Thyroid-stimulating hormone (reversible cause easily missed)
• Urinalysis

Additional Testing in Selected Patients

Consider based on clinical suspicion 4:

• Hemochromatosis screening in younger patients with unexplained cardiomyopathy
• HIV testing in at-risk populations
• Rheumatologic workup, amyloidosis testing, or pheochromocytoma screening when history suggests

Additional Investigations to Consider

Pulmonary Function Testing

• Useful to exclude respiratory causes of breathlessness, not to diagnose heart failure 1
• Consider peak flow or spirometry 1

Exercise Testing

• Normal maximal exercise test in untreated patients excludes heart failure 1
• Limited value for diagnosis but useful for prognostic stratification 1

When Echocardiography is Insufficient

If echocardiography at rest is equivocal or inadequate 1, 3:

• Radionuclide angiography
• Contrast cineangiography
• Cardiac magnetic resonance imaging
• Stress echocardiography

Invasive Investigation

Generally not required for diagnosis but consider 1:

• Coronary angiography in patients with chest pain or acute decompensation
• Endomyocardial biopsy to elucidate specific causes
• Hemodynamic monitoring in severe refractory cases or shock

Critical Pitfalls to Avoid

• Never accept heart failure as a final diagnosis—always identify the underlying etiology and structural abnormality 1
• Do not skip TSH testing—thyroid dysfunction is a reversible cause easily missed 4
• Do not omit calcium and magnesium from electrolyte panels 4
• Do not rely on symptoms alone—poor correlation exists between symptoms and severity of cardiac dysfunction 1
• Avoid NSAIDs during diagnostic workup as they worsen heart failure 5