What Causes Tightness In Chest?

Hi. My husband has been experiencing tightness in chest. We were at the hospital. He was admitted and they did stress tests as well as many other testing. He is 56 years old. they told him that his heart is fine and is actually in great shape. but the tightness is still there and also having trouble sleeping. They told him it was most likely stress. I don't know what to do for him. Any thoughts?