Skip to Main Content
Diagnosis Heart & Vascular

Heart Failure

To determine if you're suffering from heart failure, your doctor will compile a complete medical history, asking you about your symptoms and performing a physical exam.

Blood tests probably will be ordered to assess kidney and liver function, sodium and potassium levels, blood count and other measurements.

In addition, your doctor may order the following tests:

  • Chest X-ray To check the size of your heart and see if there is excess fluid in the heart or lungs.
  • Electrocardiogram (ECG or EKG) A simple, painless test that records the electrical activity of the heart through electrodes placed on the skin of the chest. The machine that does this test, often performed in the doctor's office, prints out a graph showing how the heart is beating and records electrical activity.

If these tests suggest heart failure, the next step will be an imaging study to evaluate the structure and function of the heart and measure the heart's ejection fraction (EJ) — the proportion of blood that is pushed out by the ventricle with each contraction or heartbeat. A normal heart pumps out one-half to two-thirds of the blood in the left ventricle with each heartbeat. An EJ below 40 percent indicates a weakened heart.

Based on the patient's medical history and symptoms, the doctor will order one or more of the following tests to measure the EJ and diagnose whether the problem is due to systolic or diastolic failure.

  • Echocardiography A safe, painless test that uses sound waves (ultrasound) to examine the heart's structure and motion. The patient lies still as a technician moves a device called a transducer over the chest. The transducer gives off silent sound waves that bounce off the heart. The sound waves create moving images of the chambers and valves of the heart that are viewed on a video monitor. This test provides information about the heart's pumping ability, blood-flow activity, valve function, size and pressure.
  • Radionuclide Venticulography This test also is called Multiple-Gated Acquisition Scanning (MUGA) and involves injecting a small amount of radioactive dye into a vein. Isotopes in the dye attach to red blood cells that are traced by a special camera as they pass through the heart and are circulated throughout the body. In turn, this test measures the heart's pumping ability. The dye is only mildly radioactive and is safely excreted in your urine. Sometimes, the images created by the nuclear medicine camera are synchronized with an electrocardiogram (ECG) that simultaneously measures the electrical activity of the heart. A nuclear medicine scan may be given twice — once when the patient is at rest and again when he or she is exercising.
  • Treadmill Exercise Test with peak VO2 This test measures how much oxygen the heart can provide to your muscles while you exercise.
  • Electrophysiology (EP) Study In an EP study, local anesthetics are used to numb areas in the groin or near the neck, and small flexible tubes called catheters are inserted through the blood vessels into the heart to record its electrical signals. During the procedure, the doctor studies the speed and flow of electrical signals through the heart, which allows him or her to identify rhythm problems and pinpoint abnormal areas.

The doctor uses information gathered from these tests to determine the type and severity of heart failure, the short-term outlook and the best course of treatment.

After the diagnosis is confirmed, the doctor usually will classify, or rank, the heart failure based on the severity of symptoms. The most commonly used classification system is called the New York Heart Association Functional Classification. Patients are placed in one of four categories, depending on the extent their condition affects the performance of normal physical activities. The four categories are:

  • Class I Patients in this category feel no symptoms and can perform ordinary physical activities without any limitations. They represent about 35 percent of patients with heart failure.
  • Class II Another 35 percent of patients with heart failure are in this category. They have mild symptoms, such as occasional swelling, and may be somewhat limited in their ability to exercise or do other strenuous activities. They don't feel symptoms when at rest.
  • Class III These patients are limited in their ability to exercise or participate in mildly strenuous activities, and are comfortable only at rest. About 25 percent of heart failure patients are in this class.
  • Class IV The most severe form of heart failure occurs in about 5 percent of patients. They are severely limited in their ability to perform any activity, having symptoms even while at rest.

UCSF Health medical specialists have reviewed this information. It is for educational purposes only and is not intended to replace the advice of your doctor or other health care provider. We encourage you to discuss any questions or concerns you may have with your provider.