NDW,
After passing all medicals with flying colours, I was entered into the RAF for pilot training in 1970. On my second aircrew medical, the Group Captain medic detected a heart murmur. I was sent to hospital for check-ups egg etc. The heart specialist said who was the numpty who sent you here? You have a narrow rib cage and the heart is near to it, so it sounds louder.
I subsequently served over 30 years as a fast jet pilot.
Hope all turns out well for you.
M2N