This is a really tough question! Unfortunately, especially in middle aged men who are at risk of heart attack, it can often be difficult to tell the difference between bad heartburn and a heart attack.
Some of the symptoms that are more concerning for heart attack include pressure in the chest that comes on with activity, sweating or shortness of breath, or radiation of the pain from the chest to the jaw or to the back or to the arm.
However, basically any episode of severe chest pain in a middle aged man should be investigated urgently by a doctor
, probably in an emergency room. This is because it can be life threatening to miss a heart attack. A doctor would perform an electrocardiogram, which is an electrical tracing of the heart, as well as some simple blood tests looking for damage to the heart muscle. If these tests are negative, they may also recommend a stress test, which is a test in which your dad would have to exercise while having his heart monitored for signs of a heart attack.
I would encourage you to strongly suggest to your father that he get evaluated right away by a doctor, in an ER setting if necessary!