Text. Infective Endocarditis

 

Infective endocarditis is an infection of the endo­cardium and the heart valves.

Bacteria (less often, fungi) that either enter the bloodstream or, in rare instances, contaminate the heart during open heart surgery can lodge on heart valves and infect the endocardium. Abnor­mal or damaged valves are most susceptible to infection, but normal valves can be infected by some aggressive bacteria, especially those pres­ent in large numbers. Accumulations of bacteria and blood clots on the valves (called vegetations) can break loose and travel to vital organs, where they can block arterial blood flow. Such obstruc­tions are very serious: they can cause stroke, heart attack, and infection and damage in the area where they lodge.

Infective endocarditis can come on suddenly and become life threatening within days (called acute infective endocarditis), or it can develop gradually and subtly over a period of weeks to several months (called subacute infective endo­carditis).

Causes

Although bacteria aren't normally found in the blood, an injury to the skin, lining of the mouth, or gums (even an injury from a normal activity such as chewing or brushing the teeth) can allow a small number of bacteria to invade the bloodstream. Gingivitis (infection and inflammation of the gums), minor skin infections, and infections elsewhere in the body may allow bacteria to enter the bloodstream, increasing the risk of endocar­ditis. Certain surgical, dental, and medical pro­cedures also may introduce bacteria into the bloodstream—for example, the use of intrave­nous lines to provide fluids, nutrition, or medications; cystoscopy (insertion of a viewing tube to examine the bladder); and colonoscopy (insertion of a viewing tube to examine the large intestine). In people with normal heart valves, no harm is done, and the body's white blood cells destroy these bacteria. Damaged heart valves, however, may trap the bacteria, which then lodge on the endocardium and start to multiply. Rarely, when a heart valve is replaced with an artificial (prosthetic) valve, bacteria may be introduced; these bacteria are more likely to be resistant to antibiotics. People with a birth defect or abnor­mality that allows blood to leak from one part of the heart to another (for instance, from one ven­tricle to the other) also have an increased risk of endocarditis.

A few bacteria in the blood (bacteremia) may not cause immediate symptoms, but bacteremia may develop into septicemia, a severe blood in­fection typically causing high fever, chills, shak­ing, and low blood pressure. A person with sep­ticemia is particularly at risk of developing endocarditis.

The bacteria that cause acute bacterial endo­carditis are sometimes aggressive enough to in­fect normal heart valves; the bacteria that cause subacute bacterial endocarditis nearly always in­fect abnormal or damaged valves. In the United States, most cases of endocarditis occur in people with birth defects of the heart chambers and valves, people with artificial heart valves, and el­derly people with valve damage from childhood rheumatic fever or with heart valve changes as­sociated with aging. Injecting drug users are at high risk of developing endocarditis because they often inject bacteria directly into their blood­stream through dirty needles, syringes, or drug solutions.

In injecting drug users and people who develop endocarditis from prolonged catheter use, the inlet valve to the right ventricle (the tricuspid valve) is most often infected. In most other cases of endocarditis, the inlet valve to the left ventricle (the mitral valve) or the outlet valve from the left ventricle (the aortic valve) is infected. For a per­son with an artificial valve, the risk of infective endocarditis is greatest during the first year after surgery; after that the risk diminishes but remains slightly higher than normal. For unknown rea­sons, the risk always is greater with an artificial aortic valve than with an artificial mitral valve and with a mechanical valve rather than with one transplanted from a pig.

Symptoms

Acute bacterial endocarditis usually begins sud­denly with a high fever (102° F. to 104° F; 38, 8- 40^{o C}), fast heart rate, tiredness, and rapid and extensive heart valve damage. Dislodged endocardial veg­etations (emboli) can travel to other areas and create additional infection sites. Collections of pus (abscesses) may develop at the base of in­fected heart valves or wherever infected emboli settle. Heart valves may be perforated, and major leaks may develop within a few days. Some people go into shock, and their kidneys and other organs stop functioning (a condition called sepsis syn­drome). Arterial infections can weaken blood ves­sel walls, causing them to rupture. The rupture can be fatal, particularly if it's in the brain or near the heart.

Subacute bacterial endocarditis may produce symptoms for months before heart valve damage or emboli make the diagnosis clear to the doctor. Symptoms may include tiredness, mild fever (99° F. to 101° F; 37,2-38,3^o C), weight loss, sweating, and a low red blood cell count (anemia). A doctor may suspect endocarditis in a person with a fever and no ob­vious source of infection if the person has a new heart murmur or if the sound of an existing mur­mur has changed. A doctor may note an enlarged spleen. Very small spots resembling tiny freckles may appear on the skin, and similar spots may appear in the whites of the eyes or under the fingernails. These spots are areas of minuscule bleeding caused by tiny emboli that have broken off the heart valves. Larger emboli may cause stomach pain, sudden blockage of an artery to an arm or leg, a heart attack, or stroke.

Other symptoms of acute and subacute bacte­rial endocarditis may include chills, joint pain, pale skin, rapid heartbeat, painful nodules under the skin, confusion, and blood in the urine.

Endocarditis of an artificial heart valve may be an acute or subacute infection. Compared with infection of a natural valve, infection of an artifi­cial valve is more likely to spread to the heart muscle at the base of the valve and loosen the valve. Emergency surgery is then needed to re­place the valve because heart failure from severe valvular leaks can be fatal. Alternatively, the heart's electrical conduction system may be in­terrupted, resulting in slowing of the heartbeat, which may lead to a sudden loss of consciousness or even death.

Diagnosis

People suspected of having acute bacterial en­docarditis usually are hospitalized promptly for diagnosis and treatment. Because the symptoms of subacute bacterial endocarditis are initially vague, the infection may damage heart valves or spread to other sites before it's diagnosed. Un­treated subacute endocarditis is just as life threat­ening as acute endocarditis.

A doctor may suspect endocarditis based on the symptoms alone, particularly when they oc­cur in someone with a predisposing condition. Echocardiography, which uses reflected sound waves to create an image of the heart can iden­tify heart valve vegetations and damage. To iden­tify the disease-causing bacteria, a doctor may have blood samples drawn and cultured. Because bacteria are only intermittently released into the bloodstream in large enough numbers to be iden­tified, three or more samples are taken at different times to increase the likelihood that at least one will contain enough bacteria to be grown in the laboratory. Various antibiotics are tested against the bacteria to determine the best one to use.

Sometimes bacteria can't be cultured from blood samples. The reason may be that special techniques are needed to grow the particular bac­teria, or the patient may have taken antibiotics that didn't cure the infection but did reduce the number of bacteria enough to hide their pres­ence. Another possibility: the patient doesn't have endocarditis but has one of several condi­tions very similar to endocarditis, such as a heart tumor.

Prevention and Treatment

As a preventive measure, people with heart valve abnormalities, artificial valves, or congeni­tal defects are given antibiotics before dental and surgical procedures; this is why dentists and sur­geons need to know if a person has had a heart valve disorder. Although the risk of endocarditis isn't very high for surgical procedures and pre­ventive antibiotics aren't always effective, the consequences of endocarditis are so severe that most doctors believe that giving antibiotics be­fore these procedures is a reasonable precaution.

Because treatment usually consists of at least 2 weeks of high-dose intravenous antibiotics, peo­ple with bacterial endocarditis are almost always treated in the hospital. Antibiotics alone don't always cure an infection on artificial valves. Heart surgery may be needed to repair or replace dam­aged valves and remove vegetations.

 

Notes:

сontaminate заражать, загрязнять

trap улавливать

chill озноб

shak­ing дрожь

freckles веснушки

vague неясный, неопределённый

Pericardial Disease

 

The pericardium is a flexible, stretchable, two-layered sac that envelops the heart. It contains just enough lubricating fluid between the two lay­ers for them to slide easily over one another. The pericardium keeps the heart in position, prevents the heart from overfilling with blood, and protects the heart from chest infections. However, the peri­cardium isn't essential to life; if the pericardium is removed, there's no measurable effect on the heart's performance.

In rare cases, the pericardium is missing at birth, or it has weak spots or holes in it. These defects can be dangerous because the heart or a major blood vessel might bulge (herniate) through a hole in the pericardium and become trapped, which could cause death in minutes. Therefore, these defects are usually surgically re­paired; if such repair isn't feasible, the whole peri­cardium may be removed. Aside from birth de­fects, diseases of the pericardium can come from infections, injuries, and widespread tumors.

Text A. Acute Pericarditis

 

Acute pericarditis is inflammation of the pericar­dium that begins suddenly and is often painful; the inflammation causes fluid and blood products such as fibrin, red blood cells, and white blood cells to pour into the pericardial space.

Acute pericarditis has many causes, ranging from viral infections (which may be painful but are short-lived and usually have no lasting ef­fects) to life-threatening cancer. Other causes in­clude AIDS, heart attack (myocardial infarction), heart surgery, systemic lupus erythematosus, rheumatoid disease, kidney failure, injury, radia­tion treatment, and leakage of blood from an aor­tic aneurysm (a balloonlike weakening of the aorta). Acute pericarditis also may result as a side effect of certain drugs, such as anticoagulants, penicillin, procainamide, phenytoin, and phenyl-butazone.

Symptoms and Diagnosis

Usually, acute pericarditis causes fever and chest pain, which typically extends to the left shoulder and sometimes down the left arm. The pain may be similar to that of a heart attack, ex­cept that it tends to be made worse by lying down, coughing, or even deep breathing. Pericarditis may cause cardiac tamponade, a potentially fatal condition.

A doctor can diagnose acute pericarditis by the patient's description of the pain and by listening through a stethoscope placed on the patient's chest. Pericarditis can produce a crunching sound similar to the creaking of a leather shoe. A chest x-ray and echocardiography (a test that uses ultrasound waves to create an image of the heart) may show too much fluid in the pericar­dium. Echocardiography also may reveal the un­derlying cause—for example, a tumor—and show the pressure of the pericardial fluid on the right chambers of the heart; high pressure is a possible warning sign of cardiac tamponade. Blood tests can detect some of the conditions that cause peri­carditis—for example, leukemia, AIDS, infections, rheumatic fever, and increased blood levels of urea resulting from kidney failure.

Prognosis and Treatment

The prognosis depends on the cause. When pericarditis is caused by a virus or when the cause isn't apparent, recovery usually takes 1 to 3 weeks. Complications or recurrences can slow recovery. People with cancer that has invaded the pericardium rarely survive beyond 12 to 18 months.

Doctors usually hospitalize people with peri­carditis, give them drugs that reduce inflamma­tion and pain (such as aspirin or ibuprofen), and watch them for complications (particularly cardiac tamponade). Intense pain may require an opiate, such as morphine, or a corticosteroid. The most commonly used drug for intense pain is prednisone.

Further treatment of acute pericarditis varies, depending on the underlying cause. Cancer pa­tients may respond to chemotherapy (anticancer drugs) or radiation therapy, but these patients often undergo surgical removal of the pericar­dium. People on dialysis because of kidney failure usually respond to changes in their dialysis pro­grams. Doctors treat bacterial infections with an­tibiotics and surgically drain the pus from the pericardium. Drugs that may cause the pericarditis are discontinued whenever possible.

People with repeated episodes of pericarditis resulting from a virus, an injury, or an unknown cause may get relief from aspirin, ibuprofen, or corticosteroids. In some cases, colchicine is ef­fective. If drug treatment fails, usually the peri­cardium is removed surgically.

 

Notes:

lubricating смазывающий

bulge выпячиваться, выпирать; деформироваться

feasible осуществимый, возможный; годный

cardiac tamponade тампонада сердца