A 50-year-old woman presents to the office complaining of chest pain upon moderate/severe exertion when attending her aerobics classes. She is an ex-smoker who quit 5 years ago with no other risk factors. In her family history, her father was diagnosed with three-vessel coronary artery disease and had coronary artery bypass grafting at the age of 70. Upon presentation, her temperature is 95 degrees F, heart rate is 75 bpm, blood pressure is 138/84 mmHg, and oxygen saturation is 99%. Her electrocardiogram shows a sinus rhythm at 75 bpm with a left QRS axis and a QTc of 390 ms. She is not routinely taking medications except for occasional use of a homeopathic anxiolytic preparation. In view of her symptoms, she is referred for a coronary computed tomography angiography (CTA) coupled with CT-derived fractional flow reserve measurements (FFRCT). The FFRCT results identify an ischemic lesion at the mid-left anterior descending artery with an FFR value of 0.74.
Which of the following plaque characteristics, as assessed by CTA, is most likely to be present at this ischemic lesion?
The correct answer is: A. Low attenuation plaque
Because plaque characteristics frequently coexist, the answer is somewhat elusive and may explain inconsistencies among studies. Nonetheless, the presence of low attenuation plaques has been repeatedly shown to be a feature of ischemic lesions, as measured by FFR.
Low-density plaques contain necrotic lipid cores and are linked to endothelial dysfunction. In a sub-study of the PACIFIC (Prospective Comparison of Cardiac PET/CT, SPECT/CT Perfusion Imaging and CT Coronary Angiography With Invasive Coronary Angiography) trial, despite the fact that all plaque features correlated to FFR, the only independent predictors of FFR were the presence of non-calcified plaque, low-attenuation plaque, positive remodeling, and spotty calcifications.1
The presence of a heavy calcific burden, identified either as a presence of a calcified plaque or dense calcium volume, is not independently associated with the presence of ischemia. This finding is consistent across studies and points toward a plaque-stabilizing role for calcium.1-3 Negative remodeling and the napkin ring sign were similarly not associated with the ischemic potential of coronary lesions.
Driessen RS, Stuijfzand WJ, Raijmakers PG, et al. Effect of Plaque Burden and Morphology on Myocardial Blood Flow and Fractional Flow Reserve. J Am Coll Cardiol 2018;71:499-509.
Park HB, Heo R, ó Hartaigh B, et al. Atherosclerotic plaque characteristics by CT angiography identify coronary lesions that cause ischemia: a direct comparison to fractional flow reserve. JACC Cardiovasc Imaging 2015;8:1-10.
Baskaran L, Ó Hartaigh B, Schulman-Marcus J, Gransar H, Lin F, Min JK. Dense calcium and lesion-specific ischemia: A comparison of CCTA with fractional flow reserve. Atherosclerosis 2017;260:163-8.