What to do if patient refuses to insert a feeding tube?

My grandpa has dementia and has been struggling for the past year. hes been in and out of hospitals becos of his heart as well. a week ago he suffered a stroke. He is partially conscious now and semi awake. His mind is clearly alive but he is struggling to respond and talk. He falls in and out of sleep and has not been eating. Hes been surviving off the IV drip. Without food, its going to be hard for him to survive this time. Because of the stroke, he lost the sbility to swallow. The doctors tried to insert a nasal feeding tube, but hes resisting because he indicates to us that its too painful when they insert it in. We dont know what option we have left. We cant go into surgery to open his stomach because his heart is too weak. Has anyone had experience with inserting feeding tubes or other alternative ways to get food into their bodies?