Heart failure is the pathophysiologic state in which the heart, via an abnormality of cardiac function (detectable or not), fails to pump blood at a rate commensurate with the requirements of the metabolizing tissues, or is able to do so only with an elevated diastolic filling pressure.
To maintain the pumping function of the heart, compensatory mechanisms increase blood volume, cardiac filling pressure, heart rate, and cardiac muscle mass. However, despite these mechanisms, there is progressive decline in the ability of the heart to contract and relax, resulting in worsening heart failure.

Signs and symptoms of heart failure include tachycardia and manifestations of venous congestion (e.g., edema) and low cardiac output (e.g., fatigue). Breathlessness is a cardinal symptom of left ventricular failure that may manifest with progressively increasing severity.

The New York Heart Association classification for heart failure is based on the relationship between symptoms and the amount of effort required to provoke them:
- Class I patients have no limitation of physical activity.
- Class II patients have slight limitation of physical activity.
- Class III patients have marked limitation of physical activity.
- Class IV patients have symptoms even at rest and are unable to carry on any physical activity without discomfort.

See reference for more information.

Adapted from Medscape Drugs & Diseases. Heart failure. Available at http://emedicine.medscape.com/article/163062-overview#showall. Accessed February 15, 2016. To view the entire article and all other content on the Medscape Drugs & Diseases site, a free, one-time registration is required.