In order to better classify heart failure, the American College of Cardiology Foundation and the American Heart Association in 2001 published a four-component staging of heart failure in which progression occurs in only one direction using risk factors as a classification model. The previous New York Heart Association functional class, based solely on symptoms, can still describe the current functional status of a patient in Stages B through D of the ACC/AHA Classification. But now the ACC/AHA classification allows for categorization of patients as their status changes by improving or becoming worse, especially in Stage C. Below one can see how these two classification methods crossover and classify a patient. With treatment, a heart failure patient can become asymptomatic, but will remain Stage C. Stage B is defined as development of structural heart disease in patients who never show symptoms or signs of heart failure. Most patients with a diagnosis of heart failure with either past or current symptoms are considered Stage C. Approximately 1% of patients with heart failure have progressed to an advanced Stage D.