An RCT demon- strated a significant reduction in the incidence of postopera- tive AF when a continuous intravenous infusion of meto- prolol was used rather than oral administration.616 The efficacy of beta-blocker use in CABG patients after hospital discharge is uncertain, as data from 2 RCTs and 1 large detailed observational analysis suggest that they exert no benefit over 2 years postoperatively.621 623 In contrast, some observa- tional analyses have reported that they are, in fact, efficacious in high-risk subgroups (eg, those with perioperative myocardial ischemia or elderly subjects with heart failure).624 A contempo- rary analysis of prescription data from 3,102 Canadian patients, 83% of whom were prescribed a beta blocker at the time of discharge, reported that those receiving beta blockers had a reduced mortality rate during a mean follow-up of 75 months.625 Of note, improved survival was noted in all patient subgroups receiving beta blockers, even including those without perioper- ative myocardial ischemia or heart failure. 4.6. ACE Inhibitors/ARBs: Recommendations Class I 1. ACE inhibitors and ARBs given before CABG should be reinstituted postoperatively once the pa- tient is stable, unless contraindicated.622,626,627 (Level of Evidence: B) 2. ACE inhibitors or ARBs should be initiated postop- eratively and continued indefinitely in CABG pa- tients who were not receiving them preoperatively, who are stable, and who have an LVEF less than or equal to 40%, hypertension, diabetes mellitus, or CKD, unless contraindicated.622,627,627a,627b (Level of Evidence: A) Class IIa 1. It is reasonable to initiate ACE inhibitors or ARBs postoperatively and to continue them indefinitely in all CABG patients who were not receiving them preoperatively and are considered to be at low risk (ie, those with a normal LVEF in whom cardiovas- cular risk factors are well controlled), unless contra- indicated.622,627 630 (Level of Evidence: B) Class IIb 1. 