Our findings from a 10-year single-center experience showed that (1) upgrade to CRT in patients with PICM resulted in a mean increase in LVEF from 28.7% to 44.3%; (2) among patients with severe PICM defined as an LVEF <35%, 91.9% improved to LVEF >35% and 35.1% improved to an LVEF >50%; (3) rates of ventricular arrythmia were low, with 3 sustained arrhythmias within the first 18 months of upgrade; and (4) those prescribed ACE inhibitors or ARBs observed the greatest improvement in LVEF. This evidence concerns the gene ACE and cardiac arrhythmia.