Accuracy of exercise testing in the assessment of the severity of myocardial ischemia as determined by means of technetium-99m tetrofosmin SPECT scintigraphy

Background. The separation of patients with suspected or known coronary art ery disease into low- and high-risk subgroups by means of noninvasive testi ng is highly relevant in the selection of patients who require further diag nostic or therapeutic investigation. We evaluated whether exercise electroc ardiographic variables during exercise testing might be a means of predicti ng the severity of myocardial ischemia as assessed,vith myocardial scintigr aphy. Methods and Results. We retrospectively reviewed 816 consecutive patients ( mean age, 57 +/- 10 Sears) who underwent exercise technetium-99m tetrofosmi n single photon emission computed tomography (SPECT) for the assessment of suspected or known coronary artery disease, Eight independent significant p redictors of the extent and severity of reversible perfusion defects (ische mic perfusion score), which when integrated in a diagnostic algorithm satis factorily discriminated patients with no reversible perfusion defects (sens itivity, 75%; specificity, 80%) and patients with severe impaired myocardia l perfusion (greater than or equal to 11 ischemic perfusion score; sensitiv ity, 77%; specificity, 82%), were identified by means of stepwise discrimin ant analysis. However, patients,vith mildly to moderately impaired myocardi al perfusion (greater than or equal to1 but <11 ischemic perfusion score) w ere poorly discriminated (sensitivity, 50%; specificity, 78%), The set of v ariables that were significant (P <.0001) for prediction included sex, myoc ardial infarction, exercise angina, the maximal amount of ST segment depres sion, rate-pressure product threshold criteria, slope of ST segment depress ion, ST/heart rate index, and peak exercise heart rate. Conclusions. The results of the use of clinical and electrocardiographic ex ercise variables satisfactorily agrees with the results from scintigraphy o nly for patients with no reversible perfusion defects and with severely imp aired myocardial perfusion. However, it fails as an approach with universal applicability.