Atlas of pathophysiology, 2 Edition

Part II - Disorders

Cardiovascular disorders

Endocarditis

Endocarditis, also known as infective or bacterial endocarditis, is an infection of the endocardium, heart valves, or cardiac prosthesis resulting from bacterial or fungal invasion.

Causes

·   I.V. drug abuse

·   Prosthetic heart valves

·   Mitral valve prolapse

·   Rheumatic heart disease

Other Predisposing Conditions

·   Congenital abnormalities—coarctation of aorta, tetralogy of Fallot

·   Subaortic and valvular aortic stenosis

·   Ventricular septal defects

·   Pulmonary stenosis

·   Marfan syndrome

·   Degenerative heart disease

·   Syphilis

·   Prior history of endocarditis

·   Pregnancy

·   Arteriovenous dialysis catheters

Native valve endocarditis (non-I.V. drug abusers)

·   Streptococci, especially Streptococcus viridans

·   Staphylococci

·   Enterococci

·   Fungi (rare)

I.V. drug abusers

·   Staphylococcus aureus

·   Streptococci

·   Enterococci

·   Gram-negative bacilli

·   Fungi

Prosthetic valve endocarditis (within 60 days of insertion)

·   Staphylococcal infection

·   Gram-negative aerobic organisms

·   Fungi

·   Streptococci

·   Enterococci

·   Diphtheroids

Pathophysiology

In endocarditis, bacteremia—even transient bacteremia following dental or urogenital procedures—introduces the pathogen into the bloodstream. This infection causes fibrin and platelets to aggregate on the heart valve tissue and engulf circulating bacteria or fungi that flourish and form friable, wartlike vegetative growths on the valves, the endocardial lining of a heart chamber, or the epithelium of a blood vessel. Such growths may cover the valve surfaces, causing ulceration and necrosis; they may also extend to the chordae tendineae, leading to rupture and subsequent valvular insufficiency. Ultimately, they may embolize to the spleen, kidneys, central nervous system, and lungs.

Signs and symptoms

·   Malaise, weakness, fatigue

·   Weight loss, anorexia

·   Arthralgia

·   Intermittent fever, night sweats, chills

·   Valvular insufficiency

·   Loud, regurgitant murmur

·   Suddenly changing murmur or new murmur in the presence of fever

·   Splenic infarction—left upper quadrant pain radiating to left shoulder, abdominal rigidity

·   Renal infarction—hematuria, pyuria, flank pain, decreased urine output

·   Cerebral infarction—hemiparesis, aphasia, other neurologic deficits

·   Pulmonary infarction—cough, pleuritic pain, pleural friction rub, dyspnea, hemoptysis

·   Peripheral vascular occlusion—numbness and tingling in an arm, leg, finger, or toe

Diagnostic test results

·   Positive blood cultures identify the causative organism.

Clinical Tip

Three or more blood cultures in a 24- to 48-hour period (each from a separate venipuncture) identify the causative organism in up to 90% of patients. Blood cultures should be drawn from three different sites with at least 1 to 3 hours between each draw.

·   Complete blood count shows normal or elevated white blood cell counts.

·   Blood smear shows abnormal histiocytes (macrophages).

·   Erythrocyte sedimentation rate is elevated.

·   Anemia panel reveals normocytic, normochromic anemia.

·   Urinalysis shows proteinuria and microscopic hematuria.

·   Serum rheumatoid factor is positive in about one-half of all patients after endocarditis is present for 6 weeks.

·   Echocardiography (particularly, transesophageal) identifies valvular damage.

·   Electrocardiogram shows atrial fibrillation or other arrhythmias.

·   Chest X-ray shows the presence of pulmonic emboli.

Treatment

·   Penicillin and an aminoglycoside, usually gentamicin

Clinical Tip

Any patient who's susceptible to endocarditis, such as those with valvular defects or another predisposing factor, should have prophylactic antibiotics prior to dental or other invasive procedures.

·   Bed rest

·   Aspirin or acetaminophen for fever and aches

·   Sufficient fluid intake

·   Corrective surgery, if refractory heart failure develops or if damage to heart structures occurs

·   Replacement of an infected prosthetic valve

P.55

TISSUE CHANGES IN ENDOCARDITIS

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