What a CC/MCC is. A CC (Complication or Comorbidity) is a secondary diagnosis CMS considers to raise resource use; an MCC (Major CC) is the higher-acuity subset. Every code is pre-assigned NONE CC MCC on CMS's lists.

How it changes payment. Many DRGs come as a family of up to three tiers — with MCC, with CC, without. A CC/MCC pushes you up a tier only if that family has tiers (some, like Syncope 312, don't). The highest present wins.

The EP angle. On a non-EP admission, documenting plain atrial fibrillation doesn't raise the DRG (not a CC). But VT, atrial flutter, complete heart block are CCs, and VF, cardiac arrest, cardiogenic shock, acute HF, NSTEMI are MCCs. Note LAAO (DRG 273/274) has only an MCC tier — a CC does nothing there.