Hi, Thanks for writing to Health Care Magic, I am Dr Asad Riaz, I have closely read your question and I understand your concerns, I will hereby guide you regarding your health related problem. After your father had a stent placed in one of tge arteries that supply his heart nuscle to relieve the blockade, he must have been put on certain medications to maintain the patency if this stent and help his heart muscle. 2 of these medications, that is ACE inhibitors and nitrates cause dizziness upon standing due to a drop in blood pressure, temporarily. In that case it is advisable to take them at night time or for the doese to be reduced. That decision is best to be made by your cardiologist. However, if the pain in jaw that he reports increases wth exertion he should get a stress test done to check for any further problems in his heart similar to those that happened prior to when the stent was placed I hope this answered your question, if you have more feel free to ask. Regards. Dr.Asad Riaz. General and Family Physician..