412 ATTENUATION CORRECTION AND SUM STRESS SCORE IN MYOCARDIAL PERFUSION IMAGING AMONG WOMEN AT RISK FOR CORONARY HEART DISEASE.

Background Myocardial perfusion imaging (MPI) is a powerful tool to detect myocardial ischemia. Nevertheless, it has not been well validated in women and obese patients due to image attenuation. We evaluated the role of attenuation correction software used in conjunction with MPI among obese women at risk for coronary heart disease (CHD). Methods MPI study data from 45 women who subsequently underwent coronary angiography were collected and analyzed. Three independent nuclear radiologists/cardiologist were asked to interpret these studies and calculate the sum stress score (SSS) and sum rest score (SRS) using nonattenuation corrected (NAC), attenuation corrected (AC), and a combine score (NAC + AC) methodologies. They were blinded to the results of the angiogram. Results The body mass index of these patients was 30.6 ± 6.6 kg/m2; the mean age was 63.3 ± 11.2. There was no difference between NAC SSS and AC SSS (6.5 ± 0.5 vs 6.7 ± 0.6; p = NS). When a combined score was calculated, there was a significant decrease in SSS between NAC SSS and combined SSS (6.5 ± 0.5 vs 4.1 ± 0.4, respectively; p < .005). Similarly, there was also a difference between AC SSS and combined SSS (6.7 ± 0.6 vs 4.1 ± 0.4, respectively; p < .003). AC software did not significantly impact the SRS, either used alone or in a combined score with the NAC image. Angiography revealed 16 patients with CHD (35.5%, defined as any coronary artery with > 70% stenosis). Among these patients the NAC SSS was higher than the AC and combined SSS (6.7 ± 0.8 vs 4.9 ± 0.9 and 4.3 ± 0.7, respectively; p < .05). Conclusions A combined score appears to significantly lower the SSS among obese women undergoing MPI. This may lead to an increased specificity of MPI in ruling out myocardial ischemia. However, among patients with true disease, the lower combined score may also decrease the sensitivity of MPI in this setting.