Estimating the Accuracy of Dobutamine Stress Echocardiography and Single-Photon Emission Computed Tomography among Patients Undergoing Noncardiac Surgery
When cardiac stress testing is ordered prior to noncardiac surgery, the optimal test modality is unknown. Therefore, we conducted this study to compare the diagnostic accuracy of dobutamine stress echocardiography (DSE) and single-photon emission computed tomography (SPECT) in a representative sample of patients undergoing noncardiac surgery without an existing diagnosis of coronary artery disease (CAD). The predicted accuracy of DSE was greater than that of SPECT in around 60.5% of cases above the current guideline-recommended risk threshold. In this population, DSE is likely to be more accurate than SPECT in the diagnosis of obstructive CAD. To the extent that making a diagnosis of obstructive CAD changes the decision to pursue noncardiac surgery, DSE likely represents a more efficient testing modality. However, in the range of pretest probabilities among this population, positive results from either test are more likely to represent false positives than true positives.
© 2018 Society of Hospital Medicine
Prediction of Obstructive CAD
To estimate the probability of obstructive CAD, we applied the risk prediction tool currently recommended by the European Society of Cardiology.11 The clinical version of this tool relies on age; sex; diagnoses of diabetes, hypertension, and dyslipidemia; active tobacco use; and chest pain characteristics to predict the probability of obstructive CAD on coronary angiography. We assumed that all patients in our cohort had nonspecific chest pain, the referent in the calculator.
Prediction of Perioperative Event Risk
To predict the probability of a perioperative cardiac event, we used the Myocardial Infarction or Cardiac Arrest (MICA) calculator, which was derived from an earlier cohort of NSQIP.12 All variables required for this prediction tool were included in the 2009 NSQIP cohort; our categorization of surgeries is included as an online appendix. MICA is one of three prediction tools included in the current American College of Cardiology/American Heart Association (ACC/AHA) guidelines.5
Prediction of Test Accuracy
We searched the MEDLINE database for estimates of the test characteristics of DSE and SPECT that adjusted for workup bias.13 (Also known as sequential-ordering bias, here we refer to the phenomenon whereby further workup is based on the results of diagnostic testing, resulting in underdiagnosis among patients with negative tests and falsely high estimates of sensitivity.14) Although other modalities of myocardial perfusion imaging exist, SPECT appears to be the most widely available, utilized, and studied modality of MPI.15 Our search strategy paired (“Sensitivity and Specificity” [MeSH Terms] AND “Coronary Disease/diagnostic imaging” [MAJR] AND “bias” [TIAB]) with (“Tomography, Emission-Computed, Single-Photon” [MAJR] OR “Echocardiography, Stress” [MAJR]). We reviewed the results for sensitivity and specificity estimates that corrected for workup bias. For each of SPECT and DSE, we drew the sensitivity and specificity from normal distributions based on literature estimates (see Table). We then calculated the expected accuracy of each modality for each patient in our dataset. All analyses were performed in Stata (version 14, College Station, Texas).
RESULTS
The median predicted probability of obstructive CAD was
Both accuracy and PPV were higher for DSE than for SPECT. The predicted accuracy of DSE was greater than that of SPECT in 73.5% of cases overall and in 60.5% of cases with a predicted operative cardiac risk greater than 1%. The mean PPV of DSE was 32.9% (median: 26.7%), while the equivalent PPVs for SPECT were 14.1% and 8.2%, respectively. Among cases with a predicted operative cardiac risk greater than 1%, the mean PPV of DSE was 57.5% (median: 60.2%), while the equivalent PPVs for SPECT were 29.8% and 26.7%, respectively.
DSE had a mean predicted accuracy of 93.0% (median: 96.2%), while SPECT had a mean accuracy of 92.6% (median: 95.6%). The predicted accuracies of DSE and SPECT are shown in the Figure, stratified by predicted perioperative risk across the 1% risk threshold currently used by ACC/AHA guidelines.
In our sensitivity analyses, dyslipidemia had little effect on the comparative accuracy. If no patients had dyslipidemia, DSE would have a higher accuracy than SPECT in 75.7% of cases. If all patients had dyslipidemia, DSE would have a higher predicted accuracy than SPECT in 72.8% of cases. For patients with an operative cardiac risk greater than 1%, the predicted accuracies were 65.0% and 59.4%, respectively.
