Potential causes of valvular stenosis

Valvular stenosis may develop before birth (e.g., is inherited or congenital) or may be acquired after birth as a result of other conditions, such as:

Types of valvular stenosis

There are four types of valvular stenosis, which correspond to the four types of heart valves: aortic stenosis, mitral stenosis, tricuspid stenosis and pulmonary stenosis.

Aortic stenosis is the narrowing of the aortic valve, located between the left ventricle and the aorta. Aortic stenosis is the most common type of valvular stenosis, as well as the most common type of valvular heart disease in general. It is estimated to occur in four of every 1000 live births. The severity of aortic stenosis can vary and is usually not detected in children until they are school-aged.

When the valves are thickened but flow is not blocked, the condition is known as aortic sclerosis, which is a common condition in patients who are over 65 years old (25 percent of this population has some form of the condition). Though this was previously believed to be a harmless condition, recent findings indicate that patients with aortic sclerosis are at a 50 percent higher risk for cardiovascular disease and heart attack. They are also more likely to develop aortic stenosis.

Less common variations of AS include:

• Subaortic stenosis. A condition in which AS occurs because of an obstruction in the left ventricle below the aortic valve.
  
  
• Supravalvular AS. A condition in which the blockage is located above the valve. This is sometimes known as the “hourglass deformity” because of the constricted shape of the aorta and the aorta valve.

In all forms of aortic stenosis, the left ventricle is forced to work harder because the flow of blood from the left ventricle to the aorta is compromised. Eventually, the walls of the ventricle can enlarge and thicken (a condition known as left ventricular hypertrophy), wear out and lead to heart failure. Proper diagnosis and appropriate treatment are crucial in repairing the underlying problem and preventing this destructive cycle from getting started.

Aortic stenosis can be caused by any of the following:

• Congenital heart disease. In this situation, the child is born with a bicuspid (two-flapped) or unicuspid (one-flapped) aortic valve rather than a tricuspid (three-flapped) aortic valve. While this opening often does not initially block blood flow, the aortic valve does not open as widely as it should, leading to rough and turbulent blood flow. The resulting “wear and tear” on this malformed valve can lead to aortic stenosis.
  
  
• Buildup of calcium. A progressive disease called idiopathic calcific aortic stenosis or senile calcific aortic stenosis  may occur, mostly in elderly people. In this disease, the valve cusps become thick and stiff from a buildup of calcium. The valve’s mobility is decreased as the buildup weighs down and fuses the aortic valve’s flaps, and the heart is overworked as it tries to pump an adequate blood flow to the rest of the body.

Mitral stenosis is a narrowing of the mitral valve between the left atrium and left ventricle. The valve can become so narrowed that it is little more than a slit. This leads to a reduction in the blood flow to the left ventricle, decreasing overall cardiac output. Also, in pure mitral stenosis, the right side of the heart is overburdened as blood backs up through the lungs and pulmonary blood vessels. This places additional pressure on the right ventricle and atrium and may result in right-sided heart failure. In some cases, however, mitral stenosis occurs in conjunction with some form of aortic stenosis, which may result in left-sided heart failure.


Mitral stenosis can be caused by one of the following:

• The most common occurrence is in women (80 percent of cases) who have experienced rheumatic fever. This may result in fusion of the valve leaflets, thickening or calcification of the valve leaflets, or thickening and shortening of the small strands that connect the valve leaflets to the heart wall (chordae tendineae). Rheumatic fever is rare in the United States, although it is still prevalent in developing countries.
  
  
• Rarely, it may be caused by a heart defect or other form of congenital heart disease.

Symptoms of mitral stenosis typically appear when the patient is in his or her 40s or 50s. Symptoms tend to be aggravated by exercise of periods of excitement, when the body's heart rate naturally increases. Sometimes symptoms appear earlier, such as during pregnancy, when the body's increased blood demands increase the heart's workload.

Tricuspid stenosis is a narrowing of the tricuspid valve, located between the right atrium and the right ventricle. Even when rheumatic fever was relatively common, the occurrence of tricuspid stenosis was relatively rare.

The congenital form (developing before birth) of pulmonic stenosis involves the partial fusion of two or three leaflets of the opening of the pulmonic valve. Its occurrence today is rare.

Pregnant women with valvular disease require extra medical attention before, during and after the pregnancy. This is largely due to the otherwise normal increase in cardiac output during pregnancy. Some heart valve conditions, like mitral valve prolapse, are not typically associated with pregnancy complications. Severe aortic stenosis, though, should be corrected before a woman becomes pregnant. Depending on the type of valve disorder, women will be advised to have regular visits to a cardiologist during the course of their pregnancy.