While doctors define heart failure in stages or classifications, it represents a progression of heart muscle weakness. Sometimes people refer to this process as chronic heart failure but technically that term isn't correct.

    The New York Heart Association (NYHA) puts the stages of heart failure into four classifications:

Class I: no limitations in activity. Normal activities can be performed.

Class II: mild limitations and mild symptoms with activity; no symptoms at rest

Class III: noticeable limitations in activity; only comfortable at rest

Class IV: symptoms occur at any level of activity and uncomfortable even resting

    The American Heart Association along with the American College of Cardiology grades heart failure in four stages, and takes into account that heart failure can be present even before symptoms appear:

Stage A: No heart failure, but at high risk due to another medical condition that can lead to heart failure, such as high blood pressure, diabetes, obesity, or coronary artery disease.

Stage B: The heart has been damaged by the patient's other medical condition(s) or other factors, but no symptoms are present yet.

Stage C: The heart is damaged and the patient is experiencing heart failure symptoms.

Stage D: The patient has severe heart failure that requires specialized care, despite receiving treatment (end-stage).