What could cause pain below the heart, on the rib side?

Hi doctor,

My father had mild chest pain. The doctor performed an angiogram and found a blockage in the blood vessel that pumps blood, which was also closed. We planned to place a stent. The next day, the doctor tested again and found that the blood vessel had opened and was normal, so the stent was not needed. A few days later, my father experienced pain below the heart, on the rib side, and he said something felt like it was pressing on his heart. We consulted a cardiologist again. The doctor examined him and said there was nothing to worry about and that he was fine.

Whenever he experienced this pain, we consulted the cardiologist, who reassured us that there was no issue with the heart. He has had this pain about three times so far. We also tested for gastric and neurological problems, but both came back fine after the examination. Despite this, he is still experiencing the same pain and is now considering another angiogram. I am unsure about the cause of the pain. Could you please provide some advice?