Heart Anatomy

The four cardiac valves are classified into two types - the atrioventricular [mitral and tricuspid] and the semilunar [aortic and pulmonic] valves. This is an important distinction. During systole, atrioventricular valves are closed and semilunar valves are open.

In diastole the opposite is true. Atrioventricular valves are open to allow ventricular filling and semilunar valves are closed to prevent backflow of blood to the heart from either systemic circulation or pulmonary circulation.

In normal persons these valves perform these functions very well. In disease the most common abnormalities of these valves are:

  • Stenosis (narrowing)
  • Insufficiency (failure to close completely - causing backflow or leaks, also known as Regurgitation)
  • A combination of Stenosis and Insufficiency

Because atrioventricular and semilunar valves function oppositely in the cardiac cycle the effects of stenosis and insufficiency are different. Stenosis of the semilunar valves causes systolic murmurs (AS, PS). Stenosis of the atrioventricular valves causes diastolic murmurs. Insufficiency of the semilunar valves is associated with diastolic murmurs (AI, PI). Insufficiency of the atrioventricular valves causes systolic murmurs (MR, TR).