Hi There Its a pleasure to answer to your question, i have read the details provided by you, as your father has already been through a major cardiac bypass having multiple grafts and after that he again got another attack. Its important to know that heart looses muscle mass with every attack and Muscle means function (contracting power), and reduced cardiac function can also means a patient drowsy . After an attack patients usually remains drowsy for few days as their body recovers from the trauma by upto certain extent. What we need to make sure is that: * His BP is not going low * Serum Electrolytes by blood test * And and ECHOCARDIOGRAPHY done in the upcoming visit so that the meds can be planned accordingly. Wish you Good Luck