It sounds to me like it could be angina of some sort, rather than heartburn. My father had symptoms for at least 3 yrs and a reduction in his level of activity - significant, he could not walk even a block, without chest pain by the time he was cath'ed. He minimized it completely to everyone but especially my Mum and the three of us.
However, he was told by his GP repeatedly, it was not a problem (this is social medicine in New Zealand), and until he was basically confined to a chair, he would not get a cath ordered. As I recall they did not even do a stress test. When I pushed him to use their private insurance (and that took a lot of pushing), he finally was cath'ed and they found a 95% plus blockage in two arteries. My point is, some men are stubborn as all get out.
If he has sought emergent care for the pain, its very doubtful that its heartburn, though not impossible. I guess the other thing to think about is gall bladder or pancreas, but that would be checked with a complete workup. The best thing to do, is when it comes on, have him take some liquid maalox or similar, if its not relieved pretty much immediately, then he needs to go to the ER again asap. Then be completely evaluated for chest pain. That is what he should check in with as his symptoms at the desk, NOT heart burn.
A catheterization is the gold standard for checking for CAD. If there is any doubt, its worth doing the test, the worst that can happen is they find nothing, the best that can happen is they find something, fix it and he feels much better. Best of luck with this.
Fiona
It sounds to me that this pain, being exertional in nature and not related to food intake, in your father who given his age and risk factors has, even without the presence of any symptoms, already a high likelihood of having coronary disease, is cardiac and not gastrointestinal in nature. Give the severity of the pain, the fact that is occurs sometimes at rest and required emergency room care, I concur with your family friend that the only test that would rule out coronary atherosclerosis is a diagnostic angiogram. A negative stress test, in this patient population by no means excludes coronary artery disease.