Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. I understand your concern and would explain that marijuana has adverse effects not only in persons which suffered from tetralogy of Fallot, but also in healthy individuals. You should know that this substance increases the risk for acute heart attack during the first hours that you smoke it. From the other hand, it may cause chronic changes to the coronary arteries. For this reason, I would encourage you to stop taking it. If you can not do this by your own, I would recommend you to search for professional help. Hope to have been helpful! Best regards, Dr. Iliri