INFECTIVE ENDOCARDITIS: (my class notes)

Fever is the most common symptom (80 to 85%) of infective endocarditis. Additional symptoms include chills, sweats, anorexia, weight loss, malaise, dyspnea, cough, stroke, headache, nausea/vomiting, myalgia/arthralgia, abdominal pain, back pain and confusion.  The onset of symptoms is estimated to be less than two weeks in patients with native valve endocarditis. The perioperative period post-cardiac valve replacement is two to five months or longer. Heart murmurs are noted in 80 to 85% of patients with infective endocarditis. The classic triad of infective endocarditis is fever, new murmur and positive blood cultures. The classic echocardiographic findings in infective endocarditis are valvular vegetation and valvular regurgitation.

Complications of infective endocarditis include:

Ø Congestive heart failure

Ø Embolization

Ø Valve ring abscess

Additional complications include valve leaflet vegetation, disruption (e.g. flail) with resultant regurgitation, perforation, aneurysm, fistula, dehiscence of prosthetic valve, pericardial effusion and hemodynamic compromise (e.g. valvular regurgitation, premature mitral valve closure, restrictive mitral valve inflow pattern, valvular stenosis (rare) and shunt).

Infective endocarditis is a greater risk in patients with prosthetic heart valve; the classic clinical setting for infective endocarditis is pre-existent valvular heart disease (e.g. rheumatic, myxomatous, congenital, prosthetic heart valve, intravenous drug abuse). A mode of infection (e.g. dental, surgical, and traumatic) is often identifiable. If a patient is an intravenous drug abuser normal right sided cardiac valves can be affected.

Vegetations are common to all types of infective endocarditis. They are situated most frequently on the valvular leaflets and less often on the endocardium of the ventricles or of the left atrium (McCallum’s patch of rheumatic carditis) and on the pulmonary or other arteries. The expected cardiac Doppler finding for infective endocarditis is valvular regurgitation. Approximately 15 % of patients do not have a new murmur due to valvular regurgitation with one possible explanation being that the vegetation is located on the base of the leaflet which may not disrupt valve closure. Valvular stenosis is a rare complication of native valve infective endocarditis.

The usual site of attachment for vegetation is on the atrial side (low pressure side) of the mitral and tricuspid valve leaflets. Aortic and pulmonary valve vegetations are usually found on the ventricular (low pressure side) of the valve. When the diameter of the vegetation exceeds 10 mm 50 % of patients develop at least one complication of infective endocarditis. In tricuspid valve endocarditis, pulmonary embolism is the most common complication.

Valve ring abscess is an uncommon but a serious typical complication of infective endocarditis and usually involves the aortic valve ring. Rupture of aortic ring abscess can occur creating a fistula.

Valve ring abscess usually presents as an area of echolucency (if cystic) or echoreflectant (if solid) around the valve ring or myocardium. Abscesses may be found in the aortic posterior annulus, peri-annular area, aortic-mitral intervalvular fibrosa, posterior aortic root and interventricular septum. For prosthetic heart valves, abscesses are usually seen around the sewing ring.

The sensitivity of detecting a vegetation with transthoracic two-dimensional echocardiography (TTE) is 65 to 80 % and with transesophageal echocardiography (TEE) it is95 %. It has been proposed that all patients with suspected infective endocarditis should undergo TEE examination. The clinical utility of cardiac magnetic resonance imaging has not been determined but has been useful in determining the presence of perivalvular extension of infection, aortic root aneurysm and fistulas.