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Structure & Function of the Heart:

Risk factors for Coronary Artery disease:

Coronary Artery Disease:

Emergency Complications of Heart Attack:

Coronary Artery Bypass Grafting (CABG):

Rheumatic Fever and Heart Valve Diseases:

Heart Transplantation and Assisted devices

Important Heart Questions and Answers

Common Drugs Used For Treatment of Heart Diseases

Have your Child been diagnosed with a Congenital Heart Disease??

 

Structure of the Heart Valves (Anatomy of the Heart Valves)

The efficiency of the heart as a pump depends not only on the force of its contractions but also on the correct functioning of its four valves. The valves are subject to a variety of disorders most commonly the failure to open or close properly. A serious valve disorder can have a progressively debilitating effect that can ultimately be fatal unless surgery is performed to correct the problem.

The heart has four valves. Two of them are situated between the upper and lower chambers (atrium and ventricle) on each side of the heart,  the tricuspid valve on the right and the mitral valve on the left. The other two lie at the exit of each ventricle into the two large arteries carrying blood from the heart, the pulmonary valve at the exit from the right ventricle into the pulmonary artery, and the aortic valve at the exit from the left ventricle into the aorta.

The valves allow blood to pass into and out of the heart chambers in one direction only, with no backflow of blood. They consist of cupped, or bowl shaped, segments called cusps. When blood is moving in the right direction, the cusps separate widely; when blood tries to move in the opposite direction, the cusps close tightly and form a watertight seal.

When the ventricles contract, the pulmonary and aortic valves open to let blood out of the heart. Between heartbeats, the ventricles relax and the aortic and pulmonary valves close. The tricuspid and mitral valves then open to allow blood to pass into the heart from the body tissues and lungs. To summarize:

  1. The aortic valve allows the flow of blood from the left ventricle to the aorta during left ventricular contraction. It also prevents backward flow of blood form the aorta to the left ventricle during its relaxation.
  2. The mitral valve allows the flow of blood from the left atrium into the left ventricle during left ventricular relaxation. It also prevents leaking of blood from the left ventricle to the left atrium during left ventricular contraction.
  3. The tricuspid valve  allows the flow of blood from the right atrium into the right ventricle during right ventricular relaxation. It also prevents leaking of blood from the right ventricle to the right atrium during left ventricular contraction.
  4. The pulmonary valve allows the flow of blood from the right ventricle to the pulmonary artery during right ventricular contraction. It also prevents backward flow of blood form the pulmonary artery to the right ventricle during its relaxation.

The opening and closing of the valves is brought about by movement of blood and by constantly changing differences in pressure on either side of the valves. The mitral and tricuspid valves are subject to considerable pressure when the powerful lower chambers (ventricles) contract. To prevent the cusps of the valves from ballooning upward into the atria under this pressure, they are connected by strong fibrous cords (called chordae tendineae) to short, fingerlike muscles (called papillary muscles) rising from the floors of the ventricles. The papillary muscles contract and tense the cords when the valves close.

The aortic and pulmonary valves, which are smaller and have more rigid cusps than the other two valves, are less liable to be pushed backward out of position under pressure so they do not require the same fastening mechanism.

Valve disorders fall into two principal groups. The first includes disorders in which a valve is narrowed or fails to open properly, obstructing the forward flow of blood. This is called stenosis, and usually occurs when the affected valves have become inflamed or calcified. It may also occur as a congenital defect.

The second group of valve disorders includes those in which the valves fail to close properly, causing a backward leakage, or regurgitation, of blood. These valves are called incompetent or insufficient. Backward leakage of blood may result from coronary heart disease, from rheumatic heart disease, or from bacterial endocarditis.

Of the four valves, those on the left side of the heart, the aortic and mitral valves,are more commonly affected by disorders because the more powerful contractions of the left ventricle place a greater strain on these two valves.

 

 

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