Endocarditis - Causes, Symptoms and Treatment
What is Endocarditis?
Also called infective endocarditis and bacterial endocarditis, endocarditis is an infection of the endocardium, heart valves, or a cardiac prosthesis, resulting from bacterial or fungal invasion. This invasion produces vegetative growths on the heart valves, the endocardial lining of a heart chamber, or the endothelium of a blood vessel that may embolize to the spleen, kidneys, central nervous system, and lungs.
In endocarditis, fibrin and platelets aggregate on the valve tissue and engulf circulating bacteria or fungi that flourish and produce friable verrucous vegetations . Such vegetations may cover the valve surfaces, causing ulceration and necrosis; they may also extend to the chordae tendineae, leading to their rupture and subsequent valvular insufficiency.
Untreated endocarditis is usually fatal, but with proper treatment, about 70% of patients recover. The prognosis is worst when endocarditis causes severe valvular damage, leading to insufficiency and heart failure, or when it involves a prosthetic valve.
What are the Causes of Endocarditis?
Most commonly, endocarditis occurs in l.V. drug abusers, patients with prosthetic heart valves, and those with mitral valve prolapse (especially males with a systolic murmur). These conditions have surpassed rheumatic heart disease as the leading risk factor.
Other predisposing conditions include coarctation of the aorta; tetralogy of Fallot; subaortic and valvular aortie stenosis; ventricular septal defects; pulmonary stenosis; Marfan's syndrome; degenerative heart disease, especially calcific aortic stenosis; and, rarely, syphilitic aortic valve. Some patients with endocarditis have no underlying heart disease.
Microbes that cause infection differ among patient groups. In patients with native valve endocarditis who aren't I.V. drug abusers, causative organisms usually include, in order of frequency, streptococci (especially Streptococcus viridans), staphylococci, and enterococci. Although many other bacteria occasionally cause the disorder, fungal causes are rare in this group. The mitral valve is involved most commonly, followed by the aortic valve.
In patients who are I.V. drug abusers, Staphylococcus aureus is the most common infecting organism. Less frequently, streptococci, enterococci, gramnegative bacilli, or fungi cause the disorder. Most often the tricuspid valve is involved, followed by the aortic valve and then the mitral valve.
In patients with prosthetic valve endocarditis, early cases (those that develop within 60 days of valve insertion) are usually due to staphylococcal infection. Gramnegative aerobic organisms, fungi, streptococci, enterococci, or diphtheroids may also cause the disorder. The course of the infection is often fulminating and associated with a high mortality rate. Late cases (those that develop after 60 days) present similarly to native valve endocarditis.
What are the Signs and Symptoms of Endocarditis?
Early clinical features of endocarditis are usually nonspecific and include malaise, weakness, fatigue, weight loss, anorexia, arthralgia, night sweats, chills, valvular insufficiency and, in 90% of patients, an intermittent fever that may recur for weeks. A more acute onset is associated with highly pathogenic organisms such as S. aureus.
Endocarditis often causes a loud, regurgitant murmur that is typical of the underlying heart lesion. A suddenly changing murmur or the discovery of a new murmur in the presence of fever is a classic physical sign of endocarditis.
In about 30% of patients, embolization from vegetating lesions or diseased valvular tissue may produce the following features of splenic, renal, cerebral, or pulmonary infarction or peripheral vascular occlusion:
1. Splenic Infarction: Pain in the left upper quadrant, radiating to the left shoulder; abdominal rigidity
2. Renal Infarction: Hematuria, pyuria, flank pain, decreased urine output
3. Cerebral Infarction: Hemiparesis, aphasia, or other neurologic deficits
4. Pulmonary Infarction (most common in right-sided endocarditis, which usually occurs in I.V. drug abusers and after cardiac surgery): cough, pleuritic pain, pleural friction rub, dyspnea, hemoptysis
5. Peripheral Vascular Occlusion: Numbness and tingling in an arm or a leg, finger, or toe or signs of impending peripheral gangrene.
Other signs include splenomegaly; petechiae of the skin (especially common on the upper anterior trunk) and the buccal, pharyngeal, or conjunctival mucosa; and splinter hemorrhages under the nails. Rarely, endocarditis produces Osler's nodes (tender, raised subcutaneous lesions on the fingers or toes), Roth's spots (hemorrhagic areas with white centers on the retina), and Janeway lesions (purplish macules on the palms or soles).
Diagnosis for Endocarditis
Three or more blood cultures in a 24- to 48-hour period (each from a separate site) identify the causative microbe in up to 90% of patients. The remaining 10% may have negative blood cultures, possibly suggesting fungal infection or infections that are difficult to diagnose, such as Haemophilus parainfluenzae. Research has supported the use of guidelines commonly referred to as the Duke criteria. The Duke approach distinguishes between major and minor criteria.
Other abnormal but nonspecific laboratory test results include:
1. Normal or elevated white blood cell count.
2. Abnormal histiocytes (macrophages).
3. Elevated erythrocyte sedimentation rate.
4. Normocytic, normochromic anemia (in 70% to 90% of endocarditis cases).
5. Positive serum rheumatoid factor (in about one-half of all patients with endocarditis after the disease is present for 3 to 6 weeks).
6. Echocardiography may identify valvular damage; electrocardiography may show atrial fibrillation and other arrhythmias that accompany valvular disease.
7. Transesophageal echocardiography (TEE) is extremely sensitive and specific for detecting perivalvular extensions of infection.
Treatment for Endocarditis
The goal of treatment is to eradicate the infecting organism. Antimicrobial therapy should start promptly and continue over 4 to 6 weeks. Selection of an antibiotic is based on identification of the infecting microbe and on sensitivity studies. While awaiting test results or if blood cultures are negative, empiric antimicrobial therapy is based on the likely infecting microbe.
Supportive treatment includes bed rest, aspirin for fever and aches, and sufficient fluid intake. Severe valvular damage, especially aortic or mitral insufficiency, may necessitate corrective surgery if refractory heart failure develops or in cases in which an infected prosthetic valve must be replaced.
Special Considerations and Prevention Tips for Endocarditis
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