American Medical Association Family Medical Guide - American Medical Association [344]
Blood flow from the heart
When the heart receives oxygen-depleted blood from the rest of the body, the pulmonary valve opens to send the blood from the heart into the lungs for a fresh supply of oxygen. The lungs send the oxygen-rich blood back to the heart, and the aortic valve opens to allow the blood into the aorta, which sends it to the rest of the body.
Mitral Stenosis
Mitral stenosis occurs when the mitral valve, which is located between the left atrium (one of the two upper chambers of the heart) and the left ventricle (one of the two lower, pumping chambers of the heart), becomes scarred, the valve flaps (leaflets) stick together, and the channel becomes abnormally narrow. To pump blood through the narrowed opening, the atrium enlarges, and pressure inside the chamber gradually rises. This pressure is passed back through the pulmonary veins and capillaries to the lungs, which, over a period of years, become congested. To keep blood flowing through the lungs at a normal rate, the right ventricle also pumps harder and becomes enlarged.
Symptoms
The main symptom of mitral stenosis is shortness of breath. Shortness of breath occurs most often after exercise, but it also can occur during the night or whenever you lie down. When you are sleeping, you may awaken suddenly, feeling as though you can’t breathe. You may cough up small amounts of blood or blood-flecked, frothy phlegm. You may begin to wheeze, and breathing may become more difficult. These symptoms can be mistaken for bronchitis (see page 655).
As pressure builds throughout the circulatory system, you may experience fatigue, swollen ankles, or other symptoms of congestive heart failure (see page 570). Shortness of breath and fatigue can be disabling, especially if you are pregnant or if you have a chest infection, an overactive thyroid gland, or any condition that increases cardiac output. The main complication of mitral stenosis is atrial fibrillation (see page 581), which can cause heart failure and formation of a blood clot in the left atrium. A blood clot may break loose, travel through the bloodstream, and block a distant blood vessel, often in the brain, where it causes a stroke (see page 669).
About half of all people who have had rheumatic fever (see page 432) later develop heart valve damage, and nearly three quarters of these people have mitral stenosis. However, because rheumatic fever is rare today, mitral stenosis occurs much less frequently.
Mitral Stenosis
Healthy mitral valve
A healthy mitral valve allows oxygen-rich blood to flow from the left atrium into the left ventricle, the main pumping chamber of the heart.
Mitral stenosis
In mitral stenosis, the mitral valve narrows, restricting blood flow from the left atrium into the left ventricle and causing pressure to rise in the atrium. This pressure can lead to increased pressure and congestion in the lungs, eventually resulting in congestive heart failure.
Diagnosis
In some cases, a doctor detects mitral stenosis during a routine physical examination when listening to the heart through a stethoscope. If additional testing is needed, your doctor may order a chest X-ray, an electrocardiogram (ECG; see page 559), and possibly a Doppler echocardiogram (see page 561). A Doppler echocardiogram can measure the speed of blood flow through the mitral valve, allowing the doctor to determine how much the valve has narrowed.
Treatment
Your doctor may prescribe a diuretic to help your body eliminate excess fluid and decrease swelling. However, because diuretics may also cause loss of potassium (a mineral that is essential for the heart muscle to contract and maintain a normal heart rhythm), your doctor also may prescribe a potassium supplement. If you have atrial fibrillation, your doctor will prescribe medication to control it. He or she also may prescribe anticoagulants to prevent the formation of blood clots in the left atrium.