What Causes Excessive Sweating And Rash On Stomach And Back?

Hi, my husband had a trible heart by pass in October of last year. Today he was putting up a light and he started pouring sweat, he took of his shirt to cool down and he was broke out in to a rash, his stomach, and back. Question should he go back to his heart dr. so he can figure out what happen, or what? Thank you,