Does A Very Low Calcium Score Guarantee A Favorable Outcome in Symptomatic Patients (with Positive Stress Perfusion Scan

338 Objectives 1.To examine the incidence of functionally significant CAD in symptomatic patients with a very low CAC score by combined CAC score measurements and myocardial perfusion imaging (MPI). 2. To examine whether a low CAC score portends a good outcome even in the presence of a positive MPI. Multiple studies have shown that a very low coronary artery calcium (CAC) score of Methods 1756 patients with no previously known CAD underwent combined MPI and CAC score studies between January and December 2014. MPI was performed using a same-day rest/stress study (using a dose of 296 MBq (8 mCi) Tc99m-MIBI for rest and 925 MBq (25 mCi) for stress). Our study group consisted of 517/1756 patients with CAC score≤10, which was compared to a control group (n=367) having cardiovascular with CS of 11-99. The patients with positive MPI were followed up for a period of 12 month and events were recorded including myocardial infarction (MI), hospitalization for unstable angina, and coronary revascularization. We also recorded the presence of significant CAD (>50% stenosis) in patients who underwent invasive or noninvasive coronary angiography. Results Six percent (32/517) of patients had a positive MPI in the study group compared to 11% (41/367) in the control group (p<0.01). There was no significant difference between the two groups in age (range 32-81, median 56 years vs. 34-76, median 61 years), in the male-to-female ratio and in the number of cardiovascular risk factors per patient. During the follow up period, in the study group: 10/ 32 patients (31%) had coronary angiography, of whom 9 had significant CAD, including 6 patients who underwent coronary revascularization. In the control group: 22/ 41 patients (54%) underwent coronary angiography, of whom 15 had significant CAD including 10 who required coronary revascularization. One additional patient had a non-ST elevation MI and was treated conservatively because of significant thrombocytopenia and bleeding. Overall, 19% (6/32) patients with very low CAC score had events, compared to 27% (11/41) of patients with average CAC score (p=ns). Conclusions In symptomatic patients, with a very low CAC score, a small but significant percentage have a positive MPI. This group has a relatively high event rate, similar to patients with higher CAC scores, indicating that this group needs careful follow up, often with additional testing. In symptomatic patients, CAC alone cannot rule out functionally significant CAD and one should consider performing MPI in conjunction with CAC score measurements prior to further management decisions