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Infective endocarditis overview

Published: June 20, 2009. Updated: July 29, 2009

The endocardium is a smooth layer of tissue that covers the insides of the heart covering the heart muscles. It leads to reduced friction of blood as it passes against the heart wall. Bacterial infection of the endocardial lining of the heart is known as infective endocarditis.

  • Subacute form: this is a disease caused by the infection of previously deformed valves by weak bacterial organisms e.g. viridans streptococci.
  • Acute infective endocarditis: this is a disease caused infection of normal valves by strong, aggressive bacterial organisms.

When bacteria reach the blood during the course of any infection it disseminates on sterile vegetations (little projections on the endocardium) that result from any form of injury. Bacteria are trapped in the vegetations and infect it.

The infection requires high pressure areas and hence is common in mitral and aortic valve lesions (as the left side of the heart is stronger) and in weak incompetent valves more than tight valves (stenosis).

It never occurs in a failing heart and never occurs with atrial fibrillation (AF) as the atrial muscles become inefficient and do not produce the required pressure. It is also common in congenital heart diseases with significant shunting of blood (VSD, PDA, coarctation, Tetralogy and PS).

Predisposing factors include deformed valves, intravenous drug abusers (in which the acute form is common as injections may carry the aggressive forms of bacteria mentioned above), prosthesis (which are generally due to skin organisms but may be due to fungi etc.)

What are the symptoms

This is not very easy, but generally any one?that is predisposed or develops heart symptoms in addition to fever then infective endocarditis (IE) should be suspected. These should be examined for a change in the character of a previous heart murmur or the appearance of a new one. Other manifestations of the disease include Roth spots, Osler's nodes, Janeway nodules, splinter hemorrhage and clubbing. Septic emboli to Brain, Lung, Kidney and Spleen and mycotic aneurysms.

Rheumatoid factor is positive in patients with endocarditis for > 6 weeks.

How is infective endocarditis diagnosed

The definitive diagnosis requires blood cultures to test for the existence bacterial organisms in the blood and to indicate the proper antibiotic.

How is it treated

Prophylactic treatment

Antibiotics are indicated for patients with predisposing lesions before undergoing surgical manipulation leading to bacteremia.

  • Dental, urinary tract infections
  • High risk patients with prosthetic valves undergoing genitourinary or GIT procedures

Curative treatment

Cultures are drawn and empiric antibiotics are given. Many antibiotic regimens exist.

Once the results of cultures appear therapy is continued according to the results and the response of the patient to empiric treatment.

Replacement of the infected valve or prosthesis may be indicated.


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