(1 Corinthians 11:28-32 NIV) A man ought to examine himself before he eats of the bread and drinks of the cup. {29} For anyone who eats and drinks without recognizing the body of the Lord eats and drinks judgment on himself. {30} That is why many among you are weak and sick, and a number of you have fallen asleep. {31} But if we judged ourselves, we would not come under judgment. {32} When we are judged by the Lord, we are being disciplined so that we will not be condemned with the world.

A number of believers in the Corinthian church died because they handled the Lord's Supper sinfully. They went to Heaven.

I think that if Ananias and Sapphira weren't believers they wouldn't have come under God's discipline.