I have pts that are receiving cardioverter-defibrillators which would be 00534, but under the code in the relative value guide it says to code 00537 for electrophysiologic studies for cardioverter-defibrillators. When a pt is getting a new cardioverter-defibrillator, wouldnt the Dr always test it? how do i know when to use 00537 instead of 00534????