Question: Missouri Subscriber Answer: If the firing resulted from an automatic implantable cardiac defibrillator (AICD) malfunction, you should report 996.04 (Mechanical complication of cardiac device,implant, and graft; due to automatic implantable cardiac defibrillator). Alternatively, the patient may have had a dysrhythmia that caused the defibrillator to fire as it's supposed to. In that case, you would use the heart condition as the primary diagnosis code, such as a code from the 427 series (Cardiac dysrhythmias). Then you would report V45.02 (Cardiac device in situ; automatic implantable cardiac defibrillator) to indicate that the patient has an AICD.