To diagnose heart failure, a doctor will conduct a physical examination and ask about a person’s lifestyle habits, medical history, and family history. If they suspect heart failure, doctors will then order imaging and blood tests.

Based on symptoms and any heart abnormalities, the healthcare team can classify the person’s heart failure and develop a treatment plan.

This article focuses on heart failure symptoms, diagnostic tests for heart failure, and the heart failure classification systems doctors use to direct care and predict outcomes.

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People should report the following symptoms to a doctor:

  • shortness of breath
  • unexplained tiredness or fatigue
  • persistent coughing
  • swelling due to fluid trapped in body tissues, or edema
  • nausea or appetite loss
  • confusion or impaired thinking
  • increased heart rate
  • intolerance to exercise

The above symptoms may be due to heart failure.

An echocardiogram is an ultrasound image of the heart.

During echocardiography, a person lies motionless while the doctor or technician moves a device called a transducer over the chest.

The transducer sends high-frequency sound waves and transmits the resulting echoes as electrical impulses to the echocardiography machine.

The echo machine then turns the electrical impulses into still and moving pictures of the heart for examination.

Doctors use echocardiograms to assess the heart’s thickness and ejection fraction. Ejection fraction refers to the proportion of blood the heart pumps out during a contraction.

An EKG measures the electrical activity of someone’s heart.

During an EKG, a doctor attaches electrodes to the person’s chest. Wires connect the electrodes to an EKG machine, which measures and records the heart’s rhythm, beats, and electrical conduction.

An EKG can show signs of heart damage and enlargement.

To diagnose heart failure, healthcare professionals may order several blood tests, including:

  • a basic metabolic panel
  • a complete blood count
  • iron studies
  • a B-type natriuretic peptide test
  • a lipid profile
  • thyroid function tests

Doctors check levels of significant substances and check for biomarkers that can indicate heart strain. This can also help diagnose strain on the liver and kidneys, which can develop due to heart failure.

Learn more about different types of blood tests.

During a chest X-ray, a healthcare professional uses radiology equipment to take pictures of a person’s heart, lungs, blood vessels, and airways.

During the X-ray, a person will stand up or lie on a table. The doctor will take images from the front and back. They may also take images from the sides.

Because chest X-rays involve radiation, pregnant people should ensure that the doctor knows their pregnancy status. The doctor can then weigh up the risks and benefits of the test.

An exercise stress test, or treadmill test, shows how well a person’s heart responds to physical stress. It can also indicate blockages in the coronary arteries, which can contribute to heart failure.

An exercise stress test involves walking on a treadmill or riding a stationary bicycle at varying speeds and inclines while wearing monitoring equipment, such as electrodes and blood pressure cuffs.

The test monitors a person’s heart rate and rhythm, blood pressure, and breathing, as well as how tired the person feels during the test.

A doctor will check the person’s heart activity and blood pressure before and after the test.

If a person cannot physically perform an exercise stress test, the doctor may give them medication to make their heart work harder, as it would during exercise.

A doctor may also order a nuclear stress test. They inject a radionuclide, a radioactive substance that makes a person’s blood flow visible via a special camera for radioactive material. This allows the doctor to determine whether the person’s heart muscles are getting enough blood flow.

A person may do a nuclear stress test while exercising or after receiving special medication to mimic stress to the heart.

Several other tests can help doctors diagnose heart failure, including:

  • CT scan: A CT scan takes information from multiple X-rays to create 2- or 3-dimensional pictures of internal body parts.
  • Magnetic resonance imaging (MRI): An MRI scan also creates images of a person’s internal body parts but uses a magnetic field and radiofrequency waves rather than X-rays.
  • Coronary angiogram: Coronary angiography uses X-rays and contrast dye to create a coronary angiogram, which is a detailed image of a person’s coronary arteries.
  • Nuclear or PET imaging: This test produces 3-dimensional images of the heart and can detect whether the heart muscles are getting enough blood and if there is damage to the heart. PET scans can diagnose specific types of heart disease, such as sarcoidosis.
  • Myocardial biopsy: For a myocardial biopsy, a doctor inserts a small tube into the person’s groin or neck and through the blood vessels to the heart. Here, they take a sample of heart tissue and analyze it.

To discover more evidence-based information and resources about cardiovascular health, visit our dedicated hub.

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The American College of Cardiology (ACC) and the American Heart Association (AHA) developed a heart failure staging system based heavily on structural or functional heart abnormalities:

StageHeart abnormalities
AAt risk for heart failure.
No heart abnormalities.
No heart failure symptoms.
BHeart abnormality and no heart failure symptoms.
CHeart abnormality and clinical heart failure with symptoms.
DRefractory heart failure that requires advanced interventions, such as mechanical support devices.

The New York Heart Association (NYHA) classification system relies on a person’s functional capacity, or symptoms during physical activity and rest, to classify their heart failure.

Functional capacity refers to the amount of physical activity that someone can perform. Symptoms may include shortness of breath, fatigue, and heart palpitations.

Unlike the ACC/AHA classification, the NYHA classification allows movement from one class to another. More specifically, a person can move backward to prior stages.

ClassFunctional capacity
INo limitation of physical activity.
Regular activity does not cause symptoms.
IIComfortable at rest.
Some limitation of physical activity.
Regular physical activity causes symptoms.
IIIComfortable at rest.
Significant limitation of physical activity.
Less-than-usual physical activity causes symptoms.
IVSymptoms of heart failure at rest.
Unable to engage in any physical activity without discomfort.
Discomfort increases with any physical activity.

For years, doctors have used the NYHA classification system as a foundational risk stratification tool for heart failure. However, some researchers question whether the system is reliable for determining a person’s treatment.

For example, researchers in 2019 studied data from several clinical trials and found that the mortality rates varied greatly among people in the same heart failure classes.

Likewise, researchers in 2022 studied data from a different clinical trial and determined the objective measures and long-term prognosis for people in NYHA classes I and II overlapped significantly.

They also found that some patients defined as asymptomatic by their doctors were at substantial risk for adverse outcomes.

When diagnosing heart failure, doctors typically start with reviewing a person’s symptoms, recording their medical history, and conducting a physical exam before moving on to more conclusive diagnostic tests.

Once a doctor makes a heart failure diagnosis, they can classify it and develop a treatment and management plan.