Diagnosis of Endocarditis

Today we talked about a few issues. Firstly, the difference between a Transudate and Exudate in the analysis of pleural effusions. You can read more about this here.

We also discussed Endocarditis - and went through many of the peripheral stigmata of this condition. Have a look over here for more info.

Let's talk about the diagnosis of endocarditis for a minute...and think about the Duke Criteria. These are divided into major and minor criteria. For a Definite diagnosis of endocarditis, we require 2 major, 1 major + 3 minor, or 5 minor criteria. Alternatively, you can be confient in your diagnosis if you have pathologic evidence of endocarditis (eg. you have microbiologic evidence grown directly from a valve vegetation). Possible infective endocarditis is defined by 1 major + 1 minor criteria, or 3 minor criteria.

Okay...so what are the Major and Minor criteria? We will discuss these below, but here is a good link for details on the diagnosis and managment of Infective Endocarditis from the American Heart Association.

Major Criteria:

1. Positive blood cultures for endocarditis.

• typical microorganisms on two separate blood cultures (Strep, Staph, Enterococcus, HACEK etc)
• persistently positive blood cultures that grow an organism that can cause IE (eg. over a 12 hour period).
  
• Single positive blood culture for Coxiella burnetii or antiphase I IgG antibody titer >1:800.

2. Evidence of endocardial involvment

• Echocardiographic evidence: like an oscillating intracardiac mass, abscess, or dehiscence of a prosthetic valve.
• A NEW regurgitant murmer.

Minor Criteria:

1. Fever >38 degrees Celsius
   
2. Predisposing cardiac lesion or IV drug use.
3. Vascular phenomena: think about major arterial emboli, septic pulmonary infarcts, mycotic aneurysm, intracranial hemorrhage, conjunctival hemorrhages, Janeway lesions.
4. Immunologic phenomena: glomerulonephritis, Osler's nodes, Roth spots, positive rheumatoid factor.
5. Microbiologic evidence: positive blood culture but not meeting major criterion as noted previously.

Some other useful links:
here is the American Heart Assoication 2008 clinical guidelines on valvular heart diseases with a focus in infective endocardits.