The heart has four valves – the aortic, mitral, tricuspid and pulmonary valves. Like valves used in house plumbing, the heart valves open to allow fluid (blood) to be pumped forward, and they close to prevent fluid from flowing backward. Human heart valves are flaps of tissue called leaflets or cusps.
Heart valve problems fall into two major categories:
Stenosis – The opening of the valve is too narrow, and this interferes with the forward flow of blood
Regurgitation – The valve doesn't close properly. It leaks, sometimes causing a significant backflow of blood.
Heart valve problems can be congenital, which means present at birth, or acquired after birth. A heart valve problem is classified as congenital when some factor during fetal development causes the valve to form abnormally. Congenital heart valve disease affects about 1 in 1,000 newborns. Most of these infants have stenosis of either the pulmonary or the aortic valve.
Most of the time, a specific reason for the congenital heart valve problem cannot be determined. However, researchers believe that many cases are caused by genetic (inherited) factors. This is because there is a higher risk of valve abnormalities in the parents and siblings of affected newborns, compared with the overall risk of less than in the general population. Sometimes, the heart defect is related to health or environmental factors that affected the mother during pregnancy.
A heart valve problem is acquired if it occurs in a valve that was structurally normal at birth. Some causes of acquired heart valve problems include:
Rheumatic fever, an inflammatory illness that may follow an untreated strep throat infection
Endocarditis, inflammation and infection of the heart valves
Idiopathic calcific aortic stenosis, a degenerative condition seen primarily in the elderly, in which the aortic valve cusps become thickened, fused and infiltrated with calcium
Connective tissue disorders, such as Marfan's syndrome
Heart valve problems affect each valve in a slightly different way.
The aortic valve opens to allow blood to pass from the left ventricle to the aorta, the massive blood vessel that directs oxygenated blood from the heart to the rest of the body. Disorders of this valve include:
Congenital aortic stenosis – When a child is born with congenital aortic stenosis, the problem is usually a bicuspid aortic valve, meaning the valve has two flaps instead of the usual three. In about 10% of affected newborns, the aortic valve is so narrow that the child develops severe cardiac symptoms within in the first year of life. In the remaining 90%, congenital aortic stenosis is discovered when a heart murmur is found during a physical examination or a person develops symptoms later in life.
Acquired aortic stenosis – In adulthood, aortic stenosis typically is caused by rheumatic fever or idiopathic calcific aortic stenosis. Some recent research suggests that the same processes that cause atherosclerosis in the arteries of the heart may contribute to the development of aortic stenosis.
Aortic regurgitation – In aortic regurgitation, the aortic valve does not close properly, allowing blood to flow backward into the left ventricle. This decreases the forward flow of oxygenated blood through the aorta, while the backflow into the ventricle eventually dilates (stretches) the ventricle out of shape. In the past, adults with aortic regurgitation often had rheumatic fever in childhood. Today, other causes are more common, such as congenital heart disease, infection called endocarditis and connective tissue disorders.
Aortic valve problems in adults are more common in men than women.
The mitral valve opens to allow blood to pass from the left atrium to the left ventricle. Disorders of this valve include:
Mitral stenosis – Congenital mitral stenosis is rare. The typical adult patient is a woman whose mitral valve was damaged by rheumatic fever.
Mitral valve prolapse – In this condition, the leaflets of the mitral valve fail to close properly. It is a common condition, particularly among women between the ages of 14 and 30. The underlying cause is unknown, and the majority of patients never have symptoms. In most women with this condition, mitral valve prolapse has no significance. However, in men, the prolapse is more often related to abnormalities of the valve leaflets that tend to get worse over time. This can lead to severe mitral regurgitation.
Mitral regurgitation – In the past, rheumatic fever was the most often cause of mitral regurgitation. Today, mitral valve prolapse in men, endocarditis, ischemic heart disease and dilated cardiomyopathy are the most common causes.
The pulmonary valve, or pulmonic valve, is located between the right ventricle and the pulmonary artery. It allows oxygen-poor blood to flow from the right side of the heart to the lungs for oxygenation. Disorders of this valve include:
Congenital pulmonic stenosis – In the relatively few newborns with severe congenital pulmonic stenosis, the child develops heart failure or cyanosis (a bluish color to the lips, fingernails and skin) within the first month of life. In most cases, the valve is deformed, with two or three leaflets partially fused.
Adult disorders of the pulmonic valve – In adults, the pulmonic valve most often is damaged because of pulmonary hypertension (abnormally high pressure within the blood vessels in the lungs). Pulmonary hypertension can be related to chronic obstructive pulmonary disease or severe sleep apnea. It can also develop without any known underlying cause (called primary pulmonary hypertension). Damage from rheumatic fever or endocarditis is relatively rare.
The tricuspid valve allows blood to flow from the right atrium to the right ventricle. Disorders of this valve include:
Tricuspid stenosis – This usually is caused by an episode of rheumatic fever, which often damages the mitral valve at the same time. Tricuspid stenosis is rare in North America and Europe.
Tricuspid regurgitation – Tricuspid regurgitation typically occurs because of pulmonary hypertension, but it also can be caused by heart failure, myocardial infarction, endocarditis or trauma.