First of all, when was his last follow up with his cardiologist? If it has been awhile I would recommend he contact his doctor and schedule an appointment. It would benefit him to tell the person setting up the appointment that he has been experiencing chest pain for which he has been taking nitroglycerin. He should not take more than 3 tablets per episode and should space them 5 minutes apart for unrelieved chest pain. If he's still having chest pain after 3 pills, he should call 911 and go to the ER. It is not uncommon after a bypass to have the grafts block off again. I would definitely not dismiss these symptoms as he could experience having a "heart attack". Heart pain is caused by a lack of oxygen to the tissues as is evidenced in blockages. Some can be stented and others require surgery, some have to be managed with taking medications but all this should be determined by your physician. It's good you're attentive as it seems for whatever reason he's not telling you, you can intervene and let him know your concern and his need to follow up. I pray all will go well, just encourage him not to ignore his symptoms. Good luck!