When valves in the heart or blood vessels fail to function?

When there is a problem in blood flow there is the risk of cellular death. In the heart, this complication can be fatal, however, this may not be as problematic in the rest of the body depending on the size or the artery blocked.

When there is a problem in the blood flow of the heart, which is supplied by the coronary arteries, the myocytes of the heart can die. If a smaller artery in heart is blocked, this cell death can even go unnoticed, but will lead to the fibrosis of the heart tissue, not only making it less compliant, but potentially causing problems in the way the heart functions such as re-entry, which can lead to arrhythmias.

In the rest of the body, the blockage of a major vessel can be a big problem. However, if a small blood vessel is blocked the body may have collateral circuits to continue blood supply to tissue. An example of this is the internal thoracic arterty supplying posterior intercostal muscles through the anterior intercostal arteries if the posterior intercostal arteries become blocked.

So, blockage of blood vessels can lead to some big problems, especially in the heart; however, the body does have ways of supplying blood to tissues if they become blocked.