My grandmother had rheumatic heart disease. Is that the same as coronary heart disease?

No. It comes from the late effects of an earlier infection with the streptococcus bacteria called rheumatic fever, which was much more common fifty years ago, before antibiotics were available. Rheumatic fever damages one or more of the heart’s valves. Modem cardiac surgery is now able to fix these valves and return a person to a nearly normal state of health.