The American College of Cardiology/American Heart Association classification of heart failure has four stages. They are listed below.
Stage A: Patients at risk for heart failure who have not yet developed structural heart changes (i.e. those with diabetes, those with coronary disease without prior infarct)
Stage B: Patients with structural heart disease (i.e. reduced ejection fraction, left ventricular hypertrophy, chamber enlargement) who have not yet developed symptoms of heart failure
Stage C: Patients who have developed clinical heart failure
Stage D: Patients with refractory heart failure requiring advanced intervention (i.e. biventricular pacemakers, left ventricular assist device, transplantation)
Note that the ACC/AHA classification is much different than the New York Heart Association (NYHA) functional classification system, in that there is no moving backwards to prior stages. Once symptoms develop, stage C heart failure is present and stage B will never again be achieved. In the NYHA classification, in contrast, patients can move between class I and class IV relatively quickly, as these are all designated on symptoms alone.