Introduction

The Valves. Valves are muscular flaps that open and close so blood will flow in the right direction. There are four valves in the heart:

• The tricuspid regulates blood flow between the right atrium and the right ventricle.
• The pulmonary valve opens to allow blood to flow from the right ventricle to the lungs.
• The mitral valve regulates blood flow between the left atrium and the left ventricle.
• The aortic valve allows blood to flow from the left ventricle to the ascending aorta.

Click the icon to see an image of the internal structures of the heart.

The Heart's Electrical System. The heartbeats are triggered and regulated by the conducting system, a network of specialized muscle cells that form an independent electrical system in the heart muscles. These cells are connected by channels that pass chemically caused electrical impulses.

Click the icon to see an image of the conduction system of the heart.

Description of Heart Failure

Heart failure is not a disease. It is a condition or process in which the heart is unable to pump enough blood to meet the needs of the body's tissues. The heart doesn't "fail" in the sense of ceasing to beat (as occurs during a heart attack). Rather, it weakens, usually over the course of months or years, so that it is unable to pump out all the blood that enters its chambers. As a result, fluids tend to build up in the lungs and tissues, causing congestion. This condition used to be called "congestive heart failure," but the name was officially changed to heart failure in 2005.  

Ways the Heart Can Fail. Heart failure can occur in several ways:

• The muscles of the heart pumps (ventricles) become thin and weakened. They stretch (dilate) to the extent that they cannot pump the blood with enough force to reach all the body's tissues.
• The heart muscles stiffen or thicken. Here, they lose elasticity and cannot relax. Insufficient blood enters the chamber, so not enough blood is pumped out into the body to serve its needs.
• Sometimes the valves of the heart are abnormal. (Valves open or close to control the flow of blood entering or leaving the heart). They may narrow, such as in aortic stenosis, causing a back up of blood, or they may close improperly so that blood leaks back into the heart. The mitral valve (which regulates blood flow between the two chambers on the left side of the heart) often becomes leaky in severe heart failure -- a condition called mitral regurgitation.