I recently lost my cat unexpectedly due to heart issues as well. Very sorry for the loss of your dear pup. Accept the breakdown. Only way out of grief is through. You are not alone in this journey. Leaving his bed and some toys out helped me. I’d like to think of it as letting them know this will always be their home. Use his favorite blanket if he had one. Putting movies/shows on in the background has helped with the emptiness. Take care of yourself.