In a meta-analysis of 55 000 subjects with CAD, those with subclinical hypothyroidism did not have an increase in total deaths, but the CAD mortality rate was increased, particularly in those with thyroid-stimulating The risks of CABG in hypothyroid patients are poorly defined. A retrospective study of hypothyroid patients under- going CABG had a higher incidence of heart failure and gastrointestinal complications and a lower incidence of post- operative fever than did members of a matched euthyroid group.598 Patients with subclinical hypothyroidism may be at increased risk for developing AF after CABG,599 and 1 study even suggested that triiodothyronine supplementation in pa- tients undergoing CABG (including those who are euthyroid) decreased the incidence of postoperative AF.600 Conversely, controlled studies of triiodothyronine in subjects undergoing CABG have shown no benefit.601,602 Rarely, patients may develop severe hypothyroidism after CABG, which manifests as lethargy, prolonged required ventilation, and hypoten- sion.603 Thyroid replacement is indicated in these individuals. 4.5. Perioperative Beta Blockers: Recommendations Class I 1. Beta blockers should be administered for at least 24 hours before CABG to all patients without contra- indications to reduce the incidence or clinical se- quelae of postoperative AF.604 608,608a 608c (Level of Evidence: B) 2. Beta blockers should be reinstituted as soon as possible after CABG in all patients without contra- indications to reduce the incidence or clinical se- quelae of AF.604 608,608a 608c (Level of Evidence: B) 3. Beta blockers should be prescribed to all CABG patients without contraindications at the time of hospital discharge. (Level of Evidence: C) Class IIa 1. Preoperative use of beta blockers in patients without contraindications, particularly in those with an LVEF greater than 30%, can be effective in reduc- ing the risk of in-hospital mortality.609 611 (Level of Evidence: B) 2. 