The spouse would only be liable and responsible for the deceased spouses medical bills if the living spouses name was on the medical bills.
If the living spouses name is not on the medical bills then no the living spouse would not be responsible for the deceased spouses medical bills.
However it could be possible for the debt collector to take things to court and then collect any assets that the deceased spouse owned without your name on it.
If your name is on the property or other assets and the assets are jointly owned then they can't take anything away from you or force you to pay the owed medical bills.