Quantitative but not Qualitative Computed Tomography Coronary Angiography High Risk Plaque Characteristics are Associated with Major Adverse Cardiovascular Events in Patients with Non-Significant Invasive Fractional Flow Reserve

Abstract

Background: Functionally non-significant coronary stenoses by fractional flow reserve assessment (FFR >0.8) are not routinely intervened upon. These patients may still remain at risk of major adverse cardiovascular events (MACE). Computed tomography coronary angiography (CTCA) allows non-invasive assessment of qualitative and quantitative high-risk plaque (HRP) morphology which are associated with future MACE. We seek to determine if HRP was associated with MACE in patients with functionally non-significant FFR. Methods: Consecutive patients with stable chest pain who underwent CTCA and FFR within a 3-month interval, between 2009–2017, at MonashHeart were examined. Qualitative HRP were low attenuation plaque (LAP, <30 Hounsfield units), positive remodelling and spotty calcification. Quantitative HRP was regarded as LAP volume normalised to vessel length analysed (distal plaque to ostium). MACE was defined as cardiovascular death, myocardial infarction (MI) or unstable angina. Results: 54 patients (age 63 ± 11, 70% males) were evaluated. There were 39 vessels in 39 patients (72%) with qualitative HRP. Seven patients (13%) experienced MACE over 5.4-year median follow-up with 5 demonstrating qualitative HRP. The mean interval between CTCA and MACE was 576 days. Qualitative HRP features were not associated with MACE, LAP (p = 0.2), positive remodelling (p = 0.99), spotty calcification (p = 0.69). Normalised LAP volume was predictive of MACE (Hazard Ratio 1.10, 95% confidence interval 1.01–1.10, p = 0.02). Traditional anatomic predictors of MACE, including total plaque burden (p = 0.91), minimal luminal area <4 mm (p = 0.99) and total plaque volume (p = 0.4) were not significant predictors. Conclusions: In patients with functionally non-significant FFR, there remains a risk of MACE and quantitative but not qualitative HRP characteristics appear to associate with prognosis.