I am going through this exact problem. I was recently dropped by my insurance company over what they claimed was a "pre-existing condintion". The so called PEC was that I had Hepatitis A back in 1974!
Within a month of losing my health insurance ( through the largest provider her in Florida ) I was admitted to the hospital with afib, and put on medication. The cardiologist told me I need to have a heart catheterization, since a stress test showed reversible ischemia. I have so far been unable to have the cath done. The hospital will not admit me without insurance, and so far I have been unable to find a company that will insure me after having been dropped!
In other words I have been given a possible death sentence! There are no "non-profit" hospitals here in Florida where I live. Likewise we have a very limited choice of insurance companies. This is one reason we really need healthcare reform in this country.
Just wanted to share what I have found out about getting new health insurance with a heart arrhythmia as a pre-existing condition:
Since insurance companies evaluate each applicant case by case, one still has a chance depending on the history of the condition.
Otherwise, if you are lucky enough to get a job with medical benefits and the company has a group insurance arrangement, than the preexisting condition is not a basis for insurance denial. This also goes for a group of "one".
In most states, there is a special "high risk" insurance available for those with serious conditions, which are otherwise considered uninsurable. Of course these are very costly, and in some states there are no cost ceilings for the premiums.
If you lose your health insurance due to getting laid off, there is a law that if you get a new insurance within 63 days, the insurance company may not deny you (despite pre-existing conditions).
I've also found several smaller private insurance companies that take high risk applicants at a somewhat higher price, however what these companies actually cover seems a little sketchy.
Hope this was somewhat useful for some - best regards!