Moving Beyond Binary Grading of Coronary Arterial Stenoses on Coronary Computed Tomographic Angiography

OBJECTIVES We evaluated the technical and clinical utility of visual 5-point coronary stenosis grading on coronary computed tomographic angiography (CCTA). BACKGROUND The binary approach used to assess coronary stenoses on CCTA does not adequately describe borderline obstructive lesions and limits full expression of clinically useful information. METHODS From 84 patients who underwent CCTA and invasive angiography, we identified 278 native coronary segments with >= 25% stenosis on CCTA after excluding all <25% stenotic, stented, and uninterpretable segments. Fifty <25% stenotic segments were randomly selected as controls. Segmental stenosis severity on CCTA was consensually graded using a 0 to 5 scale (grade 0 = none, grade 1 = 1% to 24%, grade 2 = 25% to 49%, grade 3 = 50% to 69%, grade 4 = 70% to 89%, grade 5 = 90% to 100%) by 2 readers, using visual inspection and computed tomography-based quantification (CTQCA). Invasive angiography-based stenosis quantification (IQCA) was performed for all segments, using the same 0 to 5 scale to score stenosis severity. RESULTS On CCTA, 185 (56%) segments had intermediate stenoses (grade 2 or grade 3). Stenosis severity by IQCA increased significantly with each step-up in CCTA grade (p < 0.001). CTQCA did not perform better than visual inspection. Visual CCTA stenosis grading differed from IQCA by >1 grade in only 4% of grade 2 to grade 5 segments (10 of 278; 2% of CCTA grade 2 segments, 4% of grade 3, 8% of grade 4, 2% of grade 5). Overall quantitative correlation was strong (r = 0.82) with high variability in agreement between CTQCA and IQCA for individual segments (95% of differences between 27.2% and 34.6%). CONCLUSIONS With current CCTA technology, experienced readers should consider adopting a visually based, multitiered grading approach to evaluate coronary stenoses. A <= 49% lesion on CCTA can be considered virtually exclusive of >= 70% stenosis by invasive angiography. (J Am Coll Cardiol Img 2008; 1:460-71) (C) 2008 by the American College of Cardiology Foundation