Hi,
Yes, there is a possibility to have a heart attack even though you are taking plavix and lipitor. Plavix prevents clot formation, while lipitor reduces plaque formation with in the vessels, but do not completely stop them from occurring. And this inturn depends upon various other factors like smoking, alcohol, life style, physical activity, long standing chronic conditions like hypertension, diabetes etc. Best.
Plavix reduces the probability of having blood clots that could block the vessels from normal blood flow and cause a heart attack. Blood clots can still occur, but the risk is reduced.
Lipitor helps prevent plaque buildup in the vessels. With plaque buildup in coronary vessel that exceeds 70% may cause symptoms and require treatment to prevent heart failure or a heart attack.
Hope this provides some insight, and thanks for the question.