It's difficult to comment on stopping medication due to lack of information, but generally that presents unpredictable problems and there is a risk/ benefit consideration to discontinue.
Most often a heart attack occurs from a rupture of soft plaque through the inner layer of coronary vessels causing a clot and interruption of blood supply tro heart cells and sometimes the breaking away of hard plaque in the artery lumen, and other heart problems.
But fatal spasms can occur in coronary arteries that don’t have coronary artery disease. It’s not always clear what causes a coronary artery spasm, but sometimes it can be related to:
Taking certain drugs, such as cocaine
Emotional stress or pain
Exposure to extreme cold
Cigarette smoking
My condolances to loss of your dad.
First of all, I am sorry to hear of the loss of your Dad. Something caused the heart attack like a blood clot or blockage in the artery. I am not sure why the nurse would tell him to quit taking the heart medication. The medication is very important. Did he die of a heart attack? Now, it is important for you to know your cholesterol levels, make sure that you are eating healthy. LDL levels should be 100 or below, HDL for men 40's, for women 50's, triglycerides below 150. Doctors are now recommending children as young as 2 to get their cholesterol checked if heart problems run in the family. My cousin was only 9, when it was discovered that he had coronary artery disease. He was heavy and slept a lot. Everyone thought that he was just lazy. It wasn't that, it was his heart. How old was your Dad when he had his heart attack 3 years ago? My Mom was also told to stop taking her beta blocker after she had heart surgery the first time at 58 years of age. She ended up in the hospital in serious condition. I am not sure why doctors sometimes want to get their patients off of the medication. It is proven that heart medication for people with heart disease is good to take and ace inhibitors can extend lifespan. Also, cholesterol medication helps prevent excessive blockage that some people produce no matter what they eat. I found that after my Mom had her final heart surgery that she had cardiomyopathy. None of us knew even my Mom did not know. If we would have known, she may have declined heart surgery which she died from last September. Every day my 5 year old asks if her Grandma is coming back "When will she be alive again". It is hard. Hope you find some comfort.