PERIOPERATIVE β-BLOCKADE

Randomized clinical trials have demonstrated that β-blocker therapy reduces cardiac morbidity and mortality associated with silent myocardial ischemia,^[155] congestive heart failure,^[156] and acute MI.^{[157] [158]} Although the specific mechanism underlying this improvement in outcome is unknown, the prevention of catecholamine-induced arrhythmia, coronary plaque disruption, and other effects of sympathetic stimulation likely play a significant role. An expanding list of randomized clinical trials now suggest the perioperative use of β-blocker therapy can reduce cardiac morbidity and mortality after noncardiac surgery.^{[58] [60] [61] [62] [63] [159]}

The AHA/ACC guidelines^[32] have made the use of β-blockers in vascular patients with a positive stress test a level I recommendation. Implementation of these guidelines and administration of β-blockers are associated with improved cardiac outcomes after major vascular surgery.^[160] A report from the Agency for Healthcare Research and Quality identified that the perioperative use of β-blockers can reduce perioperative cardiac morbidity and mortality and advocates their expanded use beyond vascular patients.^[161] Extensive reviews of this topic have been published.^{[162] [163]}

Of the three trials that used perioperative ischemia monitoring, all found significantly less ischemia in patients treated with a β-blocker. ^{[58] [61] [159]} Both studies reporting cardiac morbidity and mortality found significantly improved cardiac outcomes for patients treated with a β-blocker.^{[60] [62] [63]} Mangano and colleagues^[60] found in 200 patients with or at risk for CAD that the 2-year mortality after noncardiac surgery was 10% in patients treated with atenolol versus 21% for the control group. Poldermans and coworkers ^[62] randomized 112 patients with positive DSE results who were undergoing vascular surgery to perioperative bisoprolol or standard care. The combined 30-day incidence of cardiac death and nonfatal MI was 3.4% in the bisoprolol group and 34% in the standard care group ( Fig. 52-8 ). At 2 years, the combined incidence of cardiac death and nonfatal MI (in 101 patients who survived surgery) was 12% in the bisoprolol group and 32% in the standard care group^[63] ( Fig. 52-9 ).

Perioperative β-blocker therapy may decrease the number of patients referred for preoperative cardiac testing. To help address this issue, Boersma and associates^[91] studied the relationship between clinical predictors, DSE results, β-blocker therapy, and adverse cardiac outcomes in a large cohort of patients scheduled for vascular surgery. Figure 52-10 summarizes their results. Patients on β-blocker therapy with a risk score of less than 3 points had a very low (0.7%) cardiac event rate. This potentially large (>80%) group of patients could proceed directly to surgery without preoperative testing. DES testing was useful to stratify patients with a risk score of 3 or more points. Patients without stress-induced ischemia and those with limited (1 to 4 segments) new wall motion abnormalities were adequately protected by β-blockers. However, β-blockers failed to reduce cardiac morbidity among patients who were in the highest risk strata (i.e., five or more abnormal segments). These patients would be referred for invasive testing and possible coronary revascularization.

In summary, the perioperative administration of β-blocker therapy reduces perioperative and long-term cardiac morbidity.^[162] This outcome benefit probably results from blunting of the neurohormonal and hemodynamic effects of sympathetic stimulation. Available evidence suggests that clinicians caring for vascular surgery patients should embrace this therapy and widely incorporate it into their practice. Although perioperative β-blocker therapy may decrease the number of patients referred for preoperative cardiac testing, such testing will not likely be eliminated.