Generally, blockages less than 50% are left alone but need to be monitored, up to 75%-80% usually can be stented, 100% blockages generally require bypass. As for
the damage to the heart
, it may not be a blockage, it could be scare tissue damage or an electrical impulse issue, that's why they are doing the cath. I have no blockages yet have EF 17% and stress test images show severe damage and restricted perfusion.