There are several diseases veterans can have that the VA calls "presumptive conditions." "Presumptive conditions" are illnesses that don't need the usual amount of evidence to file a VA disability claim. This is because certain materials used by the military are known to cause health problems to the servicemembers exposed to them. Certain health problems are linked to times and locations of service. So, veterans who served in Vietnam don't need evidence for Agent Orange related conditions.
Ischemic heart disease (IHD) is a presumptive condition of Agent Orange exposure. Agent Orange can cause several diseases. IHD, also called coronary artery disease (CAD), is a heart problem where arteries build up plaque, restricting oxygen flow in the blood. This can cause a heart attack if the arties get completely clogged with plaque. You may suffer from other "presumptive conditions." To check, look up your period of service on this exposure tool. Since some conditions might not have obvious symptoms, Vietnam era veterans should take a free Agent Orange Registry health exam for possible health problems related to the chemical.
Continue to help filing a VA disability claim. Make note: if you had a heart attack as a result of IHD/CAD, the scars from your surgery should each get their own % when calculating your disability rating. Scars from surgery are secondary conditions to your IHD/CAD.