Coronary calcium scoring in selected patients after normal or equivocal myocardial perfusion imaging studies, clinical usefulness

Abstract

Background: Coronary calcium scoring (CCS) by CT after myocardial perfusion imaging (MPI) in selected patients might improve sensitivity for the detection of significant coronary artery disease (CAD), or in patients with symptoms, improve diagnostic confidence for the absence of significant CAD. Methods: We reviewed all 132 patients who were referred for CCS shortly after MPI at our medical center (4-slice MDCT; scan parameters 120 kV, 100 mA, 4 × 2.5 mm slice collimation, 0.375 scan pitch, 3 mm slice thickness, 125–250 ms temporal resolution) (MPI by thallium, sestamibi, or dual isotope SPECT in 124 patients, rubidium PET in 8). Results: No patient had an ischemic MPI, but 15 had chest pain with exercise testing, 15 had an ischemic ECG response, and 8 had an equivocal scintigraphic response. These patients (n=30) thus had a stress response which was considered not to be completely normal. The remaining patients (n=102) had completely non-ischemic stress MPI tests and were referred for CCS in order to improve the diagnostic confidence that CAD was not present. Nine patients (7%) had CCS scores greater than 400 volume units indicating significant CAD and another 11 (8%) patients had CCS 100–400 units indicating CAD which was possibly significant. In addition, 15 patients had mildly abnormal CCS (score 11–100) suggesting early CAD The remainder (n=81) had CCS less than 10 confirming no significant CAD. No patients with CCS >100 were diabetics. Of the 30 patients with not-completely-normal stress studies, 2 were reclassified as having significant CAD based on a CCS > 400, and another 2 had CCS 100–400. Thus, in this series of patients who were referred for CCS after MPI, 29/132 (22%) were reclassified from not having CAD to having CAD based on a CCS > 100. Patients who were reclassified were not easily identifiable based on clinical or stress test parameters. Coronary calcium testing appears to be a promising approach to identifying patients who have significant CAD despite a non-ischemic MPI, and for confirming the absence of CAD in selected patients in whom diagnostic concern persists.