Vulnerable plaque features on coronary CT angiography as markers of inducible regional myocardial hypoperfusion from severe coronary artery stenoses

Objective: We explored whether the presence of 3 known features of plaque vulnerability on coronary CT angiography (CCTA) - low attenuation plaque content (LAP), positive remodeling (PR), and spotty calcification (SC) - identifies plaques associated with greater inducible myocardial hypoperfusion measured by myocardial perfusion imaging (MPI). Methods: We analyzed 49 patients free of cardiac disease who underwent CCTA and MPI within a 6-month period and were found on CCTA to have focal 70-99% stenosis from predominantly non-calcified plaque in the proximal or mid segment of 1 major coronary artery. Presence of LAP (<= 30 Hounsfield Units), PR (outer wall diameter exceeds proximal reference by >= 5%), and SC (<= 3 mm long and occupies <= 90 degrees of cross-sectional artery circumference) was determined. On MPI, reversible hypoperfusion in the myocardial territory corresponding to the diseased artery was quantified both as percentage of total myocardium (RevTPD(ART)) by an automatic algorithm and as summed difference score (SDSART) by two experienced readers. RevTPD(ART) >= 3% and SDSART >= 3 defined significant inducible hypoperfusion in the territory of the diseased artery. Results: Plaques in patients with RevTPD(ART) >= 3% more frequently exhibited LAP (70% vs. 14%, p < 0.001) and PR (70% vs. 24%, p = 0.001) but not SC (55% vs. 34%, p = 0.154). RevTPD(ART) increased from 1.3 +/- 1.2% in arteries with LAP-/PR- plaques to 3.2 +/- 4.3% with LAP+/PR- or LAP-/PR+ plaques to 8.3 +/- 2.4% with LAP+/PR+ plaques (p < 0.001); SDSART showed a similar increase: 0.3 +/- 0.7 to 2.3 +/- 2.8 to 6.0 +/- 3.8 (p < 0.001). Using the same LAP/PR categorization, there was a marked increase in the frequency of significant hypoperfusion as determined by both RevTPD(ART) >= 3% (1/19 to 10/21 to 9/9, p < 0.001) and SDSART >= 3 (1/19 to 8/21 to 8/9, p < 0.001). LAP and PR, but not SC, were strong predictors of RevTPD(ART) and SDSART in regression models adjusting for potential confounders. Conclusions: Presence of low attenuation plaque and positive remodeling in severely stenotic plaques on CCTA is strongly predictive of myocardial hypoperfusion and may be useful in assessing the hemodynamic significance of such lesions. (C) 2011 Published by Elsevier Ireland Ltd.