NYHA classification..

The most commonly used classification for  Heart Failure  is the  one developed by the New York Heart Association. 

 There are 4 functional classes defined by the degree of effort needed to elicit symptoms of HF:

• Class I - Asymptomatic.  The patient has a level of exertion comparable to that of a normal individual.
• Class II - Slight limitation of physical activity.  The patient is comfortable at rest but ordinary exertion results in symptoms.
• Class III – Marked limitation of physical activity. The patient is comfortable at rest but less-than-ordinary exertion results in symptoms.
• Class IV- Symptomatic at rest.

Although it is widely used, there are some criticisms of this classification scheme:

• Although functional class tends to decline over time, patients with chronic heart failure periodically develop acute decompensated heart failure and thus fluctuate between classes. 
• Even in the absence of measurable changes in ventricular function, changes in medications and diet may have favorable or adverse effects and the NYHA class can vary.
• The NYHA functional classification requires subjective assessment by the health care provider.
• Treatment may not differ significantly across the classes, limiting its usefulness in guiding treatment recommendations.

In light of these limitations, the ACCF/AHA has endorsed a new classification scheme to complement the NYHA functional classification.  The new classification scheme aims to objectively identify stages of illness over the course of the progression of disease so that specific prevention measures and/or treatment can be recommended for each stage.  The system recognizes HF as a syndrome that starts with risk factors and then progresses to asymptomatic and symptomatic phases.

• Stage A - at high risk for HF but without structural heart disease or symptoms of HF.
• Stage B - structural heart disease but without signs or symptoms of HF.
• Stage C - structural heart disease with prior or current symptoms of HF.
• Stage D - refractory HF requiring specialized interventions. These are patients with advanced structural heart disease and marked symptoms of heart failure at rest despite maximal medical therapy.

Hunt SA, Abraham WT, Chin MH, et al. 2009 focused update incorporated into the ACC/AHA 2005 Guidelines for the Diagnosis and Management of Heart Failure in Adults: a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines: developed in collaboration with the International Society for Heart and Lung Transplantation. Circulation. 2009;119(14):e391-479. Available at: http://www.ncbi.nlm.nih.gov.ezp-prod1.hul.harvard.edu/pubmed/19324966 [Accessed June 1, 2009].