Hey, so I have am acquired prolonged QT. So when I am on ADD meds I have the prolonged Qt and when I am off the meds my heart is perfectly normal. I was wondering if using Marijuana could be very harmful to me?
PS: I don't plan on using it, I never would. I was just very curious.

It could go either way. If you become overly paranoid when smoking it, as some people do, then it could potentially lead to cardiac arrest because of the increased heart rate. It also lowers your blood pressure while on it and I am not sure what that would do considering your condition.

However, marijuana is considered by many in the medical industry to be a therapeutic drug used to treat a wide array of conditions.

I am curious do you have ADD? Or are you just taking the meds for either recreational reasons or for another condition? What meds are you taking, there may also be drug interaction issues though it is very rare.

If your in a state where medical marijuana is prescribed I would talk to your physician and see what he recommends in regard to the safety since he knows the most about your medical background.

Honestly without a full knowledge of your medical history it would be unsafe for anyone to answer this question.