Relationship Between Quantitative Adverse Plaque Features From Coronary Computed Tomography Angiography and Downstream Impaired Myocardial Flow Reserve by ¹³ N-Ammonia Positron Emission Tomography

Abstract

Background We investigated the relationship of quantitative plaque features from coronary CT Angiography (CTA) and coronary vascular dysfunction by impaired myocardial flow reserve (MFR) by 13N-Ammonia Positron Emission Tomography (PET). Methods and Results Fifty-one patients (32 men, 62.4±9.5 years) underwent combined rest-stress 13N-ammonia PET and CTA scans by hybrid PET/CT. Regional MFR was measured from PET. From CTA, 153 arteries were evaluated by semi-automated software, computing arterial non-calcified plaque (NCP), low-density NCP (NCP<30 HU), calcified and total plaque volumes, and corresponding plaque burden (plaque volumex100%/vessel volume), stenosis, remodeling index, contrast density difference (maximum difference in luminal attenuation per unit area in the lesion), and plaque length. Quantitative stenosis, plaque burden and myocardial mass were combined by boosted ensemble machine-learning algorithm into a composite risk score to predict impaired MFR (MFR≤2.0) by PET, in each artery. Nineteen patients (37%) had impaired regional MFR in at least one territory, (41/153 vessels). Patients with impaired regional MFR had higher arterial NCP (32.4 vs.17.2 %), low-density NCP (7 vs 4 %) and total plaque burden (37 vs 19.3 %, p<0.02). In multivariable analysis with 10-fold cross-validation, NCP burden was the most significant predictor of impaired MFR (Odds Ratio 1.35, p=0.021). For prediction of impaired MFR with 10-fold cross-validation, receiver-operating-characteristics-area-under-the-curve for the composite score was 0.83 (95%CI:0.79–0.91), greater than for quantitative stenosis (0.66, 95%CI:0.57–0.76, p = 0.005). Conclusions Compared to stenosis, arterial NCP burden and a composite score combining quantitative stenosis and plaque burden from CTA significantly improves identification of downstream regional vascular dysfunction.

Clinical Quantification of Myocardial Blood Flow Using PET: Joint Position Paper of the SNMMI Cardiovascular Council and the ASNC

“…[172][173][174][175][176] The addition of CT angiography information can improve the specificity of PET, especially in the setting of abnormal MBF values. 35 Special Considerations for Reporting MBF and MFR MBF and MFR studies should be conducted and interpreted by experienced labs.…”

The tools are ready, are we?

“…The information of coronary calcium burden and coronary vascular anatomy can be additionally given by CT and combined to SPECT or PET MPI data, making more comprehensive understanding of myocardial perfusion in regards to coronary plaque characters possible. 6,10,11 Clinicians are getting additional information on coronary plaques from additional invasive technologies including intravascular ultrasound, optic coherence tomography as well as near infrared imaging. It is a challenge to nuclear cardiologists how to provide comprehensive characterization of coronary plaques before the patient undergoes invasive coronary studies.…”

Updates on Stress Imaging Testing and Myocardial Viability With Advanced Imaging Modalities

“…For example, in one recent study, a cohort of patients underwent cCTA and 13-NH3 PET perfusion imaging, demonstrating that the burden of non-calcified plaque better predicted abnormal MBF than the degree of stenosis. Likewise, those with abnormal MBF were shown to have significantly more non-calcified arterial plaque, low-density non-calcified plaque, and total plaque [29]. Assante et al redemonstrated the finding that CAC correlates inversely with stress MBF and CFR and serves as an independent risk factor for reduction in CFR [30].…”