Hello, First of all, it is commendable that you remember and try to be careful about your heart condition. There are many different types of tricuspid valve atresia, and regardless of details of how the particular defect that you have works, I think that it is best that you abstain from smoking marijuana, or smoking at all. Here s why. You have a heart condition, like you said, called tricuspid valve atresia. What happens in this condition, very often, is that there might be increased flow of blood into your pulmonary system ( your lungs), due to the defect in your heart. Basically your heart has a hard time pushing blood forward into your systemic (body) circulation, and there is a backlog of blood in your pulmonary (lungs) circulation. This can be symptomatic, or not. That is, it can give you trouble, for eg, breathlessness or frequent chest infections, or it might be more insidious, and give rise to problems in the long run. If it is asymptomatic at first, what happens often is that there is what we call pulmonary hypertension that sets in, and this causes even more complications. This said, the health of your lungs is already at risk, given your condition. If you smoke, you would be adding an extra insult to your lungs, and this would definitely be detrimental to your health. Furthermore, caving in to peer pressure to do marijuana might in the future leave doors open for you to think of trying more consequential drugs, which would definitely be very dangerous for your health, especially given your heart condition. To sum up, please do not take up smoking, or smoking marijuana. There are many ways of integrating with your peer other than taking up recreational drugs with them. I hope that my answer helps clear some of your doubts. If you have further questions please do not hesitate, and if you think seeing a doctor in person would help you better, by all means do make an appointment with your primary care to discuss the issue. It is a serious health issue.