Abstract 520: Correlation Between Non-Perfusion Indices and Coronary Artery Calcification in Patients With Normal Positron Emission Tomographic Stress Myocardial Perfusion
Background: Prior studies have shown that patients with normal perfusion by myocardial perfusion imaging (MPI) frequently have substantial non-obstructive CAD. Non-perfusion indices in those with normal PET MPI scans may be sensitive to non-obstructive CAD.
Methods: We identified 760 consecutive patients referred for dipyridamole Rb-82 PET/CT MPI and same-setting CACS at our institution, who had no prior history of CAD and normal stress perfusion defined as a summed stress score <4. The TID ratio and change in LVEF were correlated with Agatston CACS categories. Univariable analysis was conducted, followed by multivariable analysis correcting for age, hypertension, and gender.
Results: There was significant univariate correlation between increased CACS and greater TID ratio (p =0.007), lesser increase in LVEF with stress (p =0.001), HTN (p<0.001), lower BMI (p =0.006), male gender (p =0.001) and increased age (p <0.001). The mean TID ratio was 1.08±0.08 in patients with CACS>800 and 0.99 ±0.11 in those with CACS <100. The mean increase in LVEF with stress was 2.54 ±3.92 in patients with CACS>800 and 5.05±4.69 in those with CACS<100. After multivariate adjustment, the relationship between CACS and TID ratio was no longer significant; however, the relationship between CACS and lesser increase in LVEF remained significant. As measured by the odds ratio, lower LV contractile reserve with stress was associated with CACS>400 (odds ratio=0.95, 95 percent confidence interval, 0.9 to 1). The multivariate analysis demonstrated that for every 1% increase in LVEF with stress, there was a 7% lower probability that patients would have CAC scores greater than 800.
Conclusion: A large non-obstructive coronary plaque burden evidenced by a high CACS is associated with impaired LV contractile reserve with vasodilator stress. The mechanism by which non-obstructive CAD leads to impaired LV contractile reserve is unclear. Patients with normal myocardial perfusion on PET MPI but little or no increase in LVEF with vasodilator stress may deserve further evaluation for non-obstructive CAD.