My dad had this.  What we heard was by the time they discover the problem, the 
infection has done quite a bit of damage.  My dad was on IV-antibiotics for 
weeks before they replaced his valve.  Having night sweats was his first alert 
to any infection.  Took MONTHS for a doctor to diagnose the correct condition.  
My sister figured it out faster on webmd.  

So, timing is everything.  

Cindy