What Causes Hyper Acidity With History Of Angioplasty?

Age 50, 6 feets, 70 kgs, went through an angioplasty 16 years ago for single vessel. Since last 1year having hyperacidity problem, got endoscopy done detected mild gastritis, also detected severe vitamin b 12 defeciency. Having trouble after walking for about 10 minutes seems like something moves from the stomach towards the chest and blocks the same have to stop and only after one minute can i start walking again. But on certain days even if I walk for 30 minutes the symptoms does not show am confused. Am on some Athrovsatitn and ecosprin now for the heart problem. The cardiologist has said that it is possibliy a acidity problem whereas the gastroenterologist says to get a Cardiac eveluation done am confused