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Effect of Plaque Morphology on Myocardial Perfusion
Study Questions:
What is the association between coronary plaque burden and morphology, as assessed by coronary computed tomography angiography (CCTA) and quantitative myocardial perfusion obtained by [15O]H2O positron emission tomography (PET) and fractional flow reserve (FFR)?
Methods:
The authors performed a post hoc substudy analysis of the PACIFIC (Prospective Comparison of Cardiac PET/CT, SPECT/CT Perfusion Imaging and CT Coronary Angiography With Invasive Coronary Angiography) trial. Patients with suspected coronary artery disease (CAD), normal left ventricular function, and an intermediate pretest probability of CAD were included (n = 208). Notable exclusion criteria were a history of documented CAD, prior myocardial infarction, atrial fibrillation, and renal failure. All patients underwent CCTA (noninvasive characterization of plaque morphology and burden), [15O]H2O PET (noninvasive characterization of hyperemic myocardial blood flow [MBF]), and FFR (invasive characterization of MBF) of all coronary arteries.
Results:
The final analysis comprised 204 patients and 610 evaluable coronary arteries, with 596 coronary arteries interrogated by FFR, and vascular territories related to PET data in 203 patients. Among these, 303 vessels (49.6%) were found to have coronary stenosis ≥50% by CCTA, where FFR was ≤0.80 in 158 coronary arteries (25.9%). Using univariable analysis, CCTA plaque parameters of plaque length, plaque volume, calcified and noncalcified plaque volume, lumen area, wall area, and maximal plaque burden were all associated with reduced hyperemic MBF by[15O]H2O PET. Using multivariable analysis, only noncalcified plaque volume and positive remodeling remained significantly associated with impaired hyperemic MBF, in addition to stenosis severity. Univariable analysis of plaque characteristics and FFR showed that the same CCTA plaque characteristics were significantly associated with FFR. Multivariable analysis revealed a significant inverse relationship with FFR for noncalcified plaque volume, low attenuation plaque, positive remodeling, spotty calcification, and luminal stenosis severity. Compared to luminal stenosis alone, the addition of noncalcified plaque volume and positive remodeling improved the positive predictive value of CCTA for FFR ≤0.80 (AUC increased from 0.86 to 0.90).
Conclusions:
Independent of luminal stenosis, CCTA features of positive remodeling and noncalcified plaque volume are associated with abnormal hyperemic MBF and FFR.
Perspective:
CCTA displays good agreement with invasive coronary angiography; however, stenosis severity alone, derived from invasive or noninvasive coronary angiography, often is not predictive of ischemia. This suggests that coronary flow hemodynamics are affected by other variables in addition to luminal stenosis. In the present study, the CCTA features of positive remodeling and noncalcified plaque volume were associated with a lower MBF (as assessed by [15O]H2O PET) and a lower FFR. In addition, these parameters offered a modest incremental improvement in diagnostic accuracy for obstructive CAD. The mechanisms underlying these associations remain unknown. Additional studies are needed to further evaluate the relationship between plaque morphology and myocardial perfusion, and if there exists a prognostic impact.
Keywords: Acute Coronary Syndrome, Angiography, Constriction, Pathologic, Coronary Angiography, Coronary Artery Disease, Coronary Stenosis, Diagnostic Imaging, Fractional Flow Reserve, Myocardial, Hemodynamics, Ischemia, Perfusion Imaging, Plaque, Atherosclerotic, Positron-Emission Tomography, Primary Prevention, Tomography, Emission-Computed, Single-Photon, Tomography, X-Ray Computed, Ventricular Function, Left
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