Plaque Morphology Could Modify Functional Measurements

The vulnerable features of plaque are independently associated to functional measurements done under hyperemia far better than baseline measurements such as iFR. These findings suggest that not only stenosis severity but also plaque features contribute to functional measurements. 

This is a sub-study of the PACIFIC (Prospective Comparison of Cardiac PET/CT, SPECT/CT Perfusion Imaging and CT Coronary Angiography with Invasive Coronary Angiography) which explores the impact of vulnerable plaque by CT on both hyperemic and non-hyperemic flow indices. Vulnerable plaque morphology by CT affects FFR measurements, which has been associated to imminent acute coronary syndrome. 

Instantaneous wave-free ratio (iFR) has recently emerged as an alternative to FFR and has been shown as good, even better, in most plaques, even though we know little about this equivalence in plaques with special risk characteristics. 

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The study prospectively assessed 257 vessels in 120 patients with suspected coronary artery disease. All patients received 256-slice coronary CT angiography to assess lesion severity and plaque characteristics. Positive remodeling, low attenuation plaque, spotty calcification and napkin ring sign were considered signs of vulnerable plaque by CT. All these plaques were assessed by FFR and iFR, including iFRa (during adenosine). 

On a per vessel basis, significant luminal stenosis corresponded to low FFR, iFR and iFRa measurements. Multivariable analysis showed both FFR and iFR were associated with ≥ 70% stenosis (p<0.001 y p=0.003, respectively).

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Vulnerable morphology was independently associated to abnormal FFR but not to iFR.

Conclusion

Vulnerable morphology of plaques by CT is associated to indices measured during hyperemia such as FFR but not to those done without adenosine such as iFR. These findings should be validated and suggest that not only stenosis severity but also plaque features contribute to functional measurements. 

Original Title: Adverse Plaque Characteristics Relate More Strongly With Hyperemic Fractional Flow Reserve and Instantaneous Wave-Free Ratio Than With Resting Instantaneous Wave-Free Ratio.

Reference: Roel S. Driessen et al. J Am Coll Cardiol Img 2020, article in press.

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