Non-invasive cardiac stress testing before elective major non-cardiac surgery: population based cohort study

OBJECTIVE To determine the association of non-invasive cardiac stress testing before elective intermediate to high risk non-cardiac surgery with survival and hospital stay. DESIGN Population based retrospective cohort study. SETTING Acute care hospitals in Ontario, Canada, between 1 April 1994 and 31 March 2004. PARTICIPANTS Patients aged 40 years or older who underwent specific elective intermediate to high risk non-cardiac surgical procedures. INTERVENTIONS Non-invasive cardiac stress testing performed within six months before surgery. MAIN OUTCOME MEASURES Postoperative one year survival and length of stay in hospital. RESULTS Of the 271 082 patients in the entire cohort, 23 991 (8.9%) underwent stress testing. After propensity score methods were used to reduce important differences between patients who did or did not undergo preoperative stress testing and assemble a matched cohort (n=46 120), testing was associated with improved one year survival (hazard ratio (HR) 0.92, 95% CI 0.86 to 0.99; P=0.03) and reduced mean hospital stay (difference -0.24 days, 95% CI -0.07 to -0.43; P<0.001). In an analysis of subgroups defined by Revised Cardiac Risk Index (RCRI) class, testing was associated with harm in low risk patients (RCRI 0 points: HR 1.35, 95% CI 1.05 to 1.74), but with benefit in patients who were at intermediate risk (RCRI 1-2 points: 0.92, 95% CI 0.85 to 0.99) or high risk (RCRI 3-6 points: 0.80, 95% CI 0.67 to 0.97). CONCLUSIONS Preoperative non-invasive cardiac stress testing is associated with improved one year survival and length of hospital stay in patients undergoing elective intermediate to high risk non-cardiac surgery. These benefits principally apply to patients with risk factors for perioperative cardiac complications.