Of particular concern during cardiac surgery is their reported association with severe hypo- tension after CPB (so-called vasoplegia syndrome) and postop- erative renal dysfunction.631,639 Although it has been postulated that these agents may protect against the development of postoperative AF, published studies have reached conflicting conclusions in this regard.634,636 The safety and efficacy of ACE inhibitors and ARBs after CABG in previously na ve low- to moderate-risk patients (ie, subjects without diabetes mellitus or renal insufficiency and with or Hillis et al 2011 ACCF/AHA CABG Guideline e681 without asymptomatic moderate LV systolic dysfunction) are uncertain; furthermore, ACE inhibitors and ARBs must be used with caution in these subjects. They should not be instituted in the immediate postoperative period if the systolic arterial pres- sure is 100 mm Hg or if the patient develops hypotension in the hospital after receiving them. 