Baddog
As of now, there have been just a few studies by independent companies/school/state sponsored. While these studies show good controls, they only test 1 or a couple e-cigs thus results should not be generalized to any e-cigarette as there are many different types now. Your doctor should look at the chemical list as well for e-cigarettes which can be found on wikipedia under e-cigs. Let me know what your doc says!
              
Links: Because ECF won't let me post links, you can find the web pages by copying and pasting these into google. The last one is the FDA study.
good luck
 
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  Electronic cigarette - Wikipedia, the free encyclopedia
   
  Study Reveals a Need to Evaluate and Regulate 'Electronic Cigarettes' – VCU News Center
   
  Evaluating the Acute Effects of Electronic Nicotine Delivery 
devices Marketed to Smokers. - Full Text View - ClinicalTrials. gov
   
  FDA and Public Health Experts Warn About Electronic Cigarettes