Infective Endocarditis

· Inflammation of the endocardium including chordae tendinae and valves of the heart

· Generally arises secondary to acute infection elsewhere in the body or in cases of preexisting cardiac disease

· It occurs more frequently in patients with a preexisting heart disease eg:

o rheumatic heart disease, congenital heart disease, previous cardiac surgery (esp prosthetic valves), previous endocarditis

· Abnormal endocardium, cardiac valves or prosthetic material may serve as a nidus for infection; they are not as well protected by the body’s immune system as normal tissue

· In persons with no preexisting heart disease, is seen in IV drug users & children < 2 years

a) Pathological Complications

• disease characterised by vegetative growths on the valve leaflets
• microbes enter blood

—> lodge on endocardial surface

—> multiply & precipitate thrombosis

—> stimulates formation of fibrin around organism

—> formation of vegetations

• on healing

—> vegetations become covered by endothelium & calcium

—> endothelium becomes scarred

—> surface susceptible to reinfection

• laden with pathogenic microbes, these lesions cause dysfunction by:

• spread infectious organism from valves to other structures of heart
• spread infectious organism via blood to end organs eg brain & kidney
• release of vegetative particles
• emboli

§ secondary ischaemia & infarction in end organs

• functional valvular dysfunction [esp aortic & mitral regurgitation] usually affects left side of heart —> emboli travel to systemic circulation
• may involve right side of heart(eg drug abusers) —> emboli travel to lungs resulting in pulmonary hypertension, pulmonary dysfunction

b) Time course with and without treatment

• Portals for entry of organism into blood include: dental surgery, URTI, GIT surgery, genitourinary surgery, cardiac surgery, iv cannulae
• Acute bacterial endocarditis (ABE)

§ staph aureus

§ developing over a period of less than 2 weeks

§ hospitalisation may occur within a few days

• Subacute bacterial endocarditis (SBE)

§ streptococcus viridans/epidermis

§ symptoms developing over weeks to several months

• Symptoms are flu-like including fever, chills, fatigue, anorexia, aches & pains
• Most patients develop heart murmurs & tachycardia
• Heart failure & associated signs & symptoms may occur
• Dislodgment of vegetations —> embolisation

· left side: petechia skin, splinter haemorrhages under nails, reduced peripheral pulses, CVA, MI, abdo pain (bowel infarction), back pain (kidney infarction)

· right side: pulmonary embolism, increased resp rate, pleuritic pain, cough

• Primary goal is to kill source of infection as quickly as possible with prolonged antibiotic cover (4 — 8 weeks)
• Anticoagulant therapy for embolization is sometimes cautiously given
• Heparin is avoided

c) Indications for surgery

§ Surgery is required to correct structural lesions if heart failure is severe or if develop significant arterial emboli

§ Surgery may be indicated to replace offending valves that are disseminating symptomatic vegetations regardless of valvular function

§ The presence of an active infection is not a contraindication to cardiac surgery in patients whose valves and their supporting structures have been severely destroyed or injured by the infection