Hi there! I totally understand your concern for your father and commend you for looking out for him. Usually, the signs and symptoms of a heart attack is a crushing chest pain (patients will often say that they feel like an elephant is sitting on their chest). If he has constant chest pain, a heart attack is possible, but less likely. I m not sure what bacteria he has, but taking penicillin for a stomach infection is unusual. The only stomach infection that I am aware of that is treated by antibiotics is H. Pylori, and that is treated by a combination of antibiotics (and penicillin is not one of them). Antibiotics tend to alter the flora of our GI tract (There are natural bacteria that live in the GI tract, and taking antibiotics can also kill the good bacteria). I would ask the doctor who prescribed the antibiotic what exactly he is trying to treat (penicillin is a very unusual choice for GI infections, period). I would also get him an EKG, which would check for any abnormalities going on with his heart. I certainly do think that his medications could be playing a role. I d recommend revisiting his medications and going over potential side effects with his doctor, especially the penicillin. I hope this helps. Feel free to contact me if you have any further questions. Thanks!