Yes, damaged cardiac muscle cells can be repaired. However, they cannot be fully restored. 

This is because the heart is a terminally developed organ. It has no potential for post-natal regeneration but it has been found to have limited intrinsic reparability or self-healing ability. When the cardiac muscle is damaged, the resulting loss of function cannot be fully restored. The potential for repairing damaged cardiac muscles depends on several factors, including the type and extent of damage, the individual's age, and their overall health.