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.