What long term effect does a cardiac arrest have on your heart?

Depends on cause: The long-term effect of cardiac arrest on your heart depends on the reason for the initial arrest and on the quality of the cardiopulmonary resuscitation (cpr). For instance, CPR may not contribute to any long-term heart damage if it is initiated quickly and performed effectively particularly if the etiology of the cardiac arrest is from a non-cardiac cause.

Depends: On degree of damage or not. If with heart attack and dead muscle it can be severe. If a chemical issue, and no damage the heart may be fine.