I have no idea what you mean with "If you're like most people, you think that heart disease is a problem for others" ?
I am well aware of coronary artery disease and it doesn't have to occur slowly over time. I have had a blockage go from 0 on one Angiogram to 99% within 6 months. I class that as a short period of time. Put someone with heart disease on a bad diet, remove exercise, stress them out every day and get them to smoke 20 cigarettes a day or more and you will see just how quickly the disease can progress.
I think you should not make comments like that without knowing what you are talking about or who you are talking too - pretty ignorant.
If you're like most people, you think that heart disease is a problem for others. But heart disease is the number one killer in the U.S. It is also a major cause of disability. There are many different forms of heart disease. The most common cause of heart disease is narrowing or blockage of the coronary arteries, the blood vessels that supply blood to the heart itself. This is called coronary artery disease and happens slowly over time. It's the major reason people have heart attacks.
Here are possible side effects....
http://www.nhs.uk/medicine-guides/pages/MedicineSideEffects.aspx?condition=High%20blood%20pressure&medicine=Diltiazem%20Hydrochloride&preparation=Diltiazem%2060mg%20modified-release%20capsules