MedWire News: Preoperative noninvasive cardiac stress testing is associated with improved 1-year survival and reduced hospital stay in patients undergoing elective non-cardiac surgery who are at high risk for cardiac complications, a large population-based study has found.
Stress testing was associated with only minor benefits in patients with patients with intermediate risk for cardiac complications, however, and with harm in those at low risk.
The findings reaffirm current American College of Cardiology and American Heart Association guidelines that recommend preoperative stress testing only in individuals with clinical risk factors for complications.
Despite these recommendations, some experts have discouraged any use of preoperative stress testing because it may delay surgery, instead advocating routine perioperative beta-blocker therapy, explain Duminda Wijeysundera (University of Toronto, Ontario, Canada) and co-authors of the current study.
However, the finding of no significant effect of preoperative stress testing on outcomes in the DECREASE II randomized trial had wide confidence intervals, they point out, while studies have also raised concerns over the safety of perioperative beta-blockade.
Given the lack of proved impact on outcomes, Wijeysundera and team used linked administrative databases to study Ontario residents aged 40 years or older who underwent elective surgery from 1994 through 2003.
Of a total of 271,082 patients included in the study cohort, 23,991 (8.9%) underwent stress testing, the authors report in the British Medical Journal.
Overall, patients who underwent stress testing had a significant 8% lower relative 1-year mortality rate (p=0.03) and 0.24-day shorter mean hospital stay (p<0.001) in comparison with a propensity-score matched cohort of 46,120 patients who did not.
Further analysis revealed that the effects of testing on mortality varied with patients’ baseline risk for cardiac complications, as indicated by Revised Cardiac Risk Index (RCRI) class which comprises the equally weighted risk factors ischemic heart disease, heart failure, cerebrovascular disease, diabetes, renal insufficiency, and high-risk surgery (intra-abdominal, intrathoracic, or suprainguinal vascular procedures).
Preoperative stress testing was associated with increased mortality in low-risk patients (RCRI 0 points), at a hazard ratio (HR) of 1.35, but with improved survival in intermediate-risk patients (RCRI 1–2 points) and high-risk patients (RCRI 3–6 points), at HRs of 0.92 and 0.80, respectively.
These values corresponded to a number needed to harm of 179 in low-risk patients and numbers needed to treat to prevent mortality at 1 year of 156 for intermediate-risk patients and 38 for high-risk patients.
Putting the latest findings in context, Davy Cheng (University of Western Ontario, London, Canada) said in a related editorial: “Overall, the evidence suggests that preoperative noninvasive stress testing should be reserved for high-risk patients, and that the survival benefits probably result from pharmacological intervention and monitoring rather than coronary intervention before non-cardiac surgery.
“Whether preoperative stress testing provides prognostic benefits in specific groups of patients at intermediate risk is unclear, but it should not be ordered in low-risk patients.”
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BMJ 2010; 340: b5526