Text B. Mitral Valve Prolapse

In mitral valve prolapse, the valve leaflets bulge into the left atrium during ventricular contraction, some­times allowing leakage (regurgitation) of small amounts of blood into the atrium.

About 2 to 5 percent of the population has mi­tral valve prolapse. It rarely causes serious heart problems.

Symptoms and Diagnosis

Most people with mitral valve prolapse have no symptoms. Others have symptoms that are difficult to explain on the basis of the mechanical problem alone; these include chest pain, palpitations, migraine headaches, fatigue, and dizziness. In some people, blood pressure may fall below normal when they stand up; in others, slightly irregular heartbeats may cause palpitations (an awareness of the heartbeat).

A doctor diagnoses the condition after hearing the characteristic clicking sound through a stethoscope. Regurgitation is diagnosed if a murmur is heard during ventricular contraction. Echocardiography, an imaging technique that uses ultrasound waves, allows a doctor to view the prolapse and determine the severity of any regurgitation.

Treatment

Most people with mitral valve prolapse need no treatment. If the heart is beating too fast, a beta-blocker may be taken to slow the heart rate and to reduce palpitations and other symptoms.

If there's regurgitation, the person should take antibiotics before dental or surgical procedures because of the small risk that bacteria released during such procedures might infect the heart valve.

Notes:

bulge выпячиваться; выпирать; деформироваться

dizziness головокружение

 

Text C. Mitral Valve Stenosis

Mitral valve stenosis is a narrowing of the mitral valve opening that increases resistance to blood flow from the left atrium to the left ventricle.

Mitral valve stenosis almost always results from rheumatic fever, which is rare today in North America and Western Europe. Thus, in these parts of the world, mitral valve stenosis occurs mostly in older people who had rheumatic fever during childhood. In the rest of the world, rheumatic fever is common, and it leads to mitral valve ste­nosis in adults, teenagers, and sometimes even children. Typically, when rheumatic fever is the cause of mitral valve stenosis, the mitral valve leaflets are partially fused together.

Mitral valve stenosis also can be congenital. Infants born with the disorder rarely live beyond age 2, unless they have surgery. Myxoma (a non-cancerous tumor in the left atrium) or a blood clot can obstruct the flow of blood through the mitral valve, producing the same effect as mitral valve stenosis.

Symptoms and Diagnosis

If stenosis is severe, blood pressure increases in the left atrium and in the veins in the lungs, re­sulting in heart failure, in which fluid accumulates in the lungs (pulmonary edema). If a woman with severe mitral valve stenosis becomes pregnant, heart failure may develop rapidly. A person with heart failure easily becomes fatigued and short of breath. At first, shortness of breath may develop only during physical activity. Later, the symptoms may occur even during rest. Some people can breathe comfortably only when they're propped up with pillows or sitting upright. A plum-colored flush in the cheeks suggests that a person has mi­tral valve stenosis. High pressure in the veins in the lung may cause a vein or capillaries to burst and bleed slightly or massively into the lungs. En­largement of the left atrium can result in atrial fib­rillation—a rapid, irregular heartbeat.

Using a stethoscope, a doctor can hear a char­acteristic heart murmur as the blood rushes through the narrowed valve from the left atrium.

Unlike a normal valve, which opens silently, the valve often makes a snapping sound as it opens to allow blood into the left ventricle. The diagnosis is usually confirmed by electrocardiography, a chest x-ray showing an enlarged atrium, or echocardiography (an imaging technique that uses ultrasound waves). Sometimes cardiac catheterization is necessary to determine the extent and characteristics of the blockage.

Prevention and Treatment

Mitral valve stenosis can be prevented only by preventing rheumatic fever, a childhood illness that sometimes occurs after untreated strep throat (streptococcal throat infection).

Drugs such as beta-blockers, digoxin, and verapamil can slow the heart rate and help control atrial fibrillation. Digoxin also strengthens the heartbeat if heart failure occurs. Diuretics can re­duce the blood pressure in the lungs by reducing the volume of circulating blood.

If drug therapy doesn't reduce the symptoms satisfactorily, valve repair or replacement may be needed. A doctor may be able to simply stretch the valve opening using a procedure called bal­loon valvuloplasty. In this procedure, a balloon-tipped catheter is threaded through a vein and eventually into the heart. Once inside the valve, the balloon is inflated, separating the valve leaf­lets where they have fused together. Alternatively, heart surgery may be carried out to separate the fused leaflets. If the valve is too badly damaged, it may be surgically replaced with a mechanical valve or one made partly from a pig's valve.

People with mitral valve stenosis are given pre­ventive antibiotics before any dental or surgical procedure to reduce the risk of a heart valve infection.

 

Notes:

fuse соединять, сливать; растворять

congenital врождённый

prop подпирать; поддерживать, помогать

pillow подушка

plum-colore flush румянец сливово-красного цвета

 

Text D.