Atlas of pathophysiology, 2 Edition

Part II - Disorders

Cardiovascular disorders

Rheumatic Heart Disease

A systemic inflammatory disease of childhood, acute rheumatic fever develops after infection of the upper respiratory tract with group A beta-hemolytic streptococci. It mainly involves the heart, joints, central nervous system, skin, and subcutaneous tissues, and commonly recurs. Rheumatic heart disease refers to the cardiac manifestations of rheumatic fever and includes pancarditis during the early acute phase and chronic valvular disease later. Cardiac involvement develops in up to 50% of patients.

Rheumatic fever tends to run in families, lending support to the existence of genetic predisposition. Environmental factors also seem to be significant in the development of the disorder.

Age Alert

In lower socioeconomic groups, the incidence of rheumatic heart disease is highest in children between ages 5 and 15, probably because of malnutrition and crowded living conditions.

Causes

Rheumatic fever is caused by group A beta-hemolytic streptococcal pharyngitis.

Rheumatic fever appears to be a hypersensitivity reaction to a group A beta-hemolytic streptococcal infection. Because few persons (3%) with streptococcal infections contract rheumatic fever, altered host resistance must be involved in its development or recurrence.

Pathophysiology

The antigens of group A streptococci bind to receptors in the heart, muscle, brain, and synovial joints, causing an autoimmune response. Because the antigens of the streptococcus are similar to some antigens of the body's own cells, antibodies may attack healthy body cells.

Carditis may affect the endocardium, myocardium, or pericardium during the early acute phase. Later, heart valve damage may cause chronic valvular disease.

Signs and symptoms

·         Polyarthritis or migratory joint pain

·         Erythema marginatum

·         Subcutaneous nodules

·         Chorea

·         Streptococcal infection a few days to 6 weeks before onset of symptoms

·         Fever

·         New or worsening mitral or aortic murmur

·         Pericardial friction rub

·         Chest pain, commonly pleuritic

·         Dyspnea, tachypnea, nonproductive cough, bibasilar crackles, edema

Diagnostic test results

·         During the acute phase, complete blood count reveals an elevated white blood cell count and an elevated erythrocyte sedimentation rate.

·         Hemoglobin and hematocrit are decreased because of suppressed erythropoiesis during inflammation.

·         C-reactive protein is positive, especially during the acute phase.

·         Cardiac enzyme levels are increased in severe carditis.

·         Antistreptolysin-O titer is elevated in 95% of patients within 2 months of onset.

·         Throat cultures show the presence of group A beta-hemolytic streptococci; however, they usually occur in small numbers.

·         Electrocardiography shows a prolonged PR interval.

·         Chest X-rays show normal heart size or cardiomegaly, pericardial effusion, or heart failure.

·         Echocardiography detects valvular damage and pericardial effusion, measures chamber size, and provides information on ventricular function.

·         Cardiac catheterization provides information on valvular damage and left ventricular function.

Clinical Tip

Jones Criteria for diagnosis require either two major criteria or one major criterion and two minor, plus evidence of a previous group A streptococcal infection.

Major criteria

·         Carditis

·         Migratory joint pain

·         Sydenham's chorea

·         Subcutaneous nodules, usually near tendons or bony prominences of joints, especially the elbows, knuckles, wrists, and knees

·         Erythema marginatum

Minor criteria

·         Fever

·         Arthralgia

·         Elevated acute phase reactants

·         Prolonged PR interval

Treatment

·         Prompt treatment of all group A beta-hemolytic streptococcal pharyngitis with oral penicillin V or I.M. benzathine penicillin G; erythromycin for patients with penicillin hypersensitivity

·         Salicylates

·         Corticosteroids

·         Strict bed rest for about 5 weeks

·         Sodium restriction, angiotensin-converting enzyme inhibitors, digoxin, and diuretics

·         Corrective surgery, such as commissurotomy, valvuloplasty, or valve replacement for severe mitral or aortic valvular dysfunction that causes persistent heart failure

·         Secondary prevention of rheumatic fever, which begins after the acute phase subsides:

§  monthly I.M. injections of penicillin G benzathine or daily doses of oral penicillin V or sulfadiazine

§  continued treatment, usually for at least 5 years or until age 21, whichever is longer

·         Prophylactic antibiotics for dental work and other invasive or surgical procedures

P.71

SEQUELAE OF RHEUMATIC HEART DISEASE

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