"I had open heart surgery 9 weeks ago to repair the mitral valve, and a single by bypass. I also developed Afib which was treated last week with electric cardioversion. I have not used marijuana since the surgery, but did prior mostly in the evening to sleep well and to help alleviate pain in one shoulder. Is it safe to use marijuana in my present condition?"
Marijuana can increase heart rate, so it is important that you discuss any therapy you are considering with your surgeon. Most likely, you will at least need to be able to ascend one flight of stairs without difficulty before taking any substance that may increase heart rate. Furthermore, smoked marijuana may damage blood vessels and increase blood pressure. Smoking of any substance should absolutely be avoided.