One or several symptoms, such as fatigue, shortness of breath or fluid retention, can provide the first clue that a patient is suffering heart failure. The condition may also be suspected after a heart attack or other traumatic cardiac event, since such events often leave the heart injured.

In diagnosing heart failure, a physician or cardiologist looks at a patient’s complete medical history and conducts a comprehensive physical exam. If heart failure is suspected, the easiest and most common test to identify it is the echocardiogram, or echo.

In echocardiography, a doctor uses ultrasound — bouncing high-frequency sound waves off the patient’s heart — to produce an image on a video monitor. The heart’s size and structures are made visible in enough detail for the doctor to evaluate its performance and condition, and identify problem areas. An echo shows how efficiently the heart chambers fill with blood and pump blood out and allows the doctor to estimate the heart’s ejection fraction, or the percentage of blood within the heart that is pumped out with each beat. The doctor can then determine if heart failure is present, estimate to what degree, and say whether the problem has to do with the heart filling (diastolic failure) or emptying (systolic failure).

The most commonly-used nomenclature for classifying degrees of heart failure severity is that developed by the New York Heart Association in 1964.* Patients with mild heart failure are classified in this four-tier system as those who show symptoms when they exert themselves. The remaining tiers match the increasing physical limitations of patients as their heart failure worsens. In overview, the NYHA classes are:

  • Class I Patient is comfortable with ordinary physical activity, but elevated activity causes symptoms, such as fatigue and shortness of breath.
  • Class II Patient is comfortable at rest, but ordinary physical activity causes symptoms.
  • Class III Even light activity causes patient fatigue, heart palpitation, or shortness of breath.
  • Class IV Patient shows symptoms at rest, and any physical activity only increases the discomfort.

*”Diseases of the Heart and Blood Vessels: Nomenclature and Criteria for Diagnosis. 6th ed.” The Criteria Committee of the New York Heart Association. Boston, Mass: Little Brown, 1964.