How heart failure is diagnosed:
tests and investigations

Article written and reviewed by Dr Luca Moretti

The diagnosis of heart failure is not based on a single symptom, a BNP value, or ejection fraction alone. The doctor combines symptoms and clinical signs, electrocardiography, blood tests, natriuretic peptides, and above all echocardiography. If the clinical picture is unclear or the cause needs to be identified, second-line investigations may be necessary.
The 2026 ESC guidelines recommend a structured assessment in patients with suspected heart failure, including natriuretic peptides, a 12-lead ECG, chest X-ray, blood tests, and transthoracic echocardiography.

The diagnostic pathway generally includes:

• assessment of symptoms, medical history, and clinical examination;
• electrocardiography;
• blood tests and assessment of kidney function, electrolytes, and other comorbidities;
• BNP or NT-proBNP;
• chest X-ray;
• transthoracic echocardiography;
• additional tests when needed to define the cause or resolve diagnostic uncertainty.

Heart failure is a clinical syndrome caused by a structural or functional abnormality of the heart. Diagnosis therefore requires symptoms and findings to be linked to an objectively demonstrable cardiac problem.

From symptoms to clinical suspicion

The pathway generally begins with problems such as breathlessness, reduced exercise tolerance, orthopnea, leg edema, and fatigue. The doctor also assesses previous myocardial infarction, hypertension, valvular heart disease, cardiomyopathy, arrhythmias, diabetes, kidney disease, and other factors that increase the likelihood of heart failure.
During the examination, the doctor may look for elevated jugular venous pressure, pulmonary crackles, peripheral edema, abnormal heart sounds, murmurs, and other signs of congestion or reduced cardiac output.

No single symptom or sign is accurate enough to confirm or exclude heart failure on its own. Even a person with marked dyspnea may have a respiratory cause, anemia, or another disorder; conversely, a patient with heart failure may have relatively subtle findings on examination, especially if already receiving treatment. The first stage therefore aims to establish how plausible the suspicion is and which tests should be performed.

ECG, blood tests, chest X-ray, and natriuretic peptides

A 12-lead ECG is recommended because it may show atrial fibrillation, conduction abnormalities, signs of previous myocardial infarction, hypertrophy, or other abnormalities that help clarify the clinical context and possible cause. A completely normal ECG makes heart failure with reduced systolic function less likely, but does not rule out all forms of heart failure.
Blood tests are also used to look for conditions that may cause or worsen symptoms. The 2026 ESC guidelines include a complete blood count, kidney function with eGFR and urinary albumin-to-creatinine ratio, electrolytes, liver and thyroid function, HbA1c, lipid profile, and iron status with ferritin and transferrin saturation.

Natriuretic peptides, particularly NT-proBNP and BNP, increase when the heart is exposed to greater wall stress. They are very useful for guiding the diagnostic pathway, but they are not a stand-alone positive/negative test independent of the rest of the assessment. The 2026 ESC guidelines suggest age-related outpatient NT-proBNP thresholds above which heart failure becomes more likely: at least 125 pg/mL below age 50, at least 250 pg/mL between ages 50 and 75, and at least 500 pg/mL above age 75. For BNP, a threshold of 35 pg/mL is used, without age-specific values.
Age, atrial fibrillation, and kidney disease can increase these markers; obesity can instead make them lower than expected. Their interpretation is discussed in more detail in the guide to BNP and NT-proBNP in heart failure.

Chest X-ray may show pulmonary congestion, pleural effusions, or cardiomegaly and, at the same time, help identify alternative pulmonary causes of dyspnea. A normal chest X-ray does not rule out heart failure.

Echocardiography: what it shows and why it is central

Transthoracic echocardiography is the fundamental imaging test. It allows assessment of cardiac chamber size, ventricular function, valves, estimated pulmonary pressure, wall motion, and numerous parameters of diastolic function. It also measures left ventricular ejection fraction, but the diagnosis is not synonymous with this number.
In the 2026 ESC guidelines, heart failure with reduced ejection fraction includes symptomatic patients with an EF below 50%. An ejection fraction of at least 50% does not, however, rule out the disease: in heart failure with preserved ejection fraction, other evidence of abnormal cardiac structure or function and elevated filling pressures is required.

Echocardiography also helps identify a possible cause, such as significant valvular disease, the consequences of ischemia, or abnormalities consistent with cardiomyopathy. It is therefore not used simply to determine whether EF is "low or normal", but to build a complete picture of how the heart is functioning.

When further investigations are needed

After the initial tests, the cause may need to be investigated further. Cardiac magnetic resonance imaging provides better myocardial tissue characterization and may be useful, for example, when myocarditis, cardiomyopathy, or infiltrative disease is suspected. Assessment of the coronary arteries with coronary CT angiography or invasive coronary angiography may be indicated when clinically relevant ischemic heart disease is suspected.
Exercise testing, cardiopulmonary exercise testing, rhythm monitoring, stress echocardiography, and, in selected cases, right heart catheterization may be used when functional capacity, arrhythmias, ischemia, or intracardiac pressures need to be clarified.

These tests are not performed automatically in every patient. The choice depends on the results already obtained, age, comorbidities, and above all the clinical question that must be answered. The goal is not to accumulate tests, but to confirm the syndrome and identify a treatable cause.

When the diagnosis is more difficult

One of the most complex situations is heart failure with preserved ejection fraction. The patient may have an apparently normal EF and symptoms that overlap with obesity, chronic lung disease, deconditioning, or other conditions. Natriuretic peptides may also be relatively low in some people, especially in the presence of obesity.
When suspicion remains high despite inconclusive initial tests, specialist assessment may require a more detailed echocardiographic analysis and, in selected cases, exercise testing or invasive hemodynamic measurements.

The practical principle is therefore simple: a normal test does not always end the diagnostic pathway if symptoms and clinical history remain strongly suggestive. Likewise, a high BNP or reduced ejection fraction does not automatically explain the cause: the result must always be interpreted in the overall context.

Frequently asked questions about the diagnosis of heart failure

What is the main test used to diagnose heart failure?
Transthoracic echocardiography is the central imaging test because it assesses cardiac structure and function, ejection fraction, valves, and other parameters. However, the diagnosis does not depend on a single test and integrates symptoms, clinical examination, natriuretic peptides, and other investigations.

Does a normal electrocardiogram rule out heart failure?
No. A normal ECG makes some forms, particularly heart failure with reduced systolic function, less likely but does not rule out all forms of heart failure, especially heart failure with preserved ejection fraction.

Do high BNP or NT-proBNP levels definitely mean heart failure?
No. Elevated values increase the likelihood of heart failure but can also be due to advanced age, atrial fibrillation, kidney disease, valvular heart disease, pulmonary hypertension, and other conditions. They must be interpreted in the clinical context.

Can you have heart failure with a normal ejection fraction?
Yes. In heart failure with preserved ejection fraction, LVEF is at least 50%, but compatible symptoms or signs are present together with other evidence of abnormal cardiac structure or function and elevated filling pressures.

When are cardiac MRI, coronary angiography, or other tests needed?
These are second-line tests used when the cause of heart failure, possible ischemia, cardiomyopathy, myocarditis, infiltrative disease, or valvular heart disease must be clarified, or when the diagnosis remains uncertain after the initial investigations.