Impact of coronary CT image quality on the accuracy of the FFRCT Planner

Abstract

Objective: To assess the accuracy of a virtual stenting tool based on coronary CT angiography (CCTA) and fractional flow reserve (FFR) derived from CCTA (FFR_CT Planner) across different levels of image quality.

Materials and methods: Prospective, multicenter, single-arm study of patients with chronic coronary syndromes and lesions with FFR ≤ 0.80. All patients underwent CCTA performed with recent-generation scanners. CCTA image quality was adjudicated using the four-point Likert scale at a per-vessel level by an independent committee blinded to the FFR_CT Planner. Patient- and technical-related factors that could affect the FFR_CT Planner accuracy were evaluated. The FFR_CT Planner was applied mirroring percutaneous coronary intervention (PCI) to determine the agreement with invasively measured post-PCI FFR.

Results: Overall, 120 patients (123 vessels) were included. Invasive post-PCI FFR was 0.88 ± 0.06 and Planner FFR_CT was 0.86 ± 0.06 (mean difference 0.02 FFR units, the lower limit of agreement (LLA) - 0.12, upper limit of agreement (ULA) 0.15). CCTA image quality was assessed as excellent (Likert score 4) in 48.3%, good (Likert score 3) in 45%, and sufficient (Likert score 2) in 6.7% of patients. The FFR_CT Planner was accurate across different levels of image quality with a mean difference between FFR_CT Planner and invasive post-PCI FFR of 0.02 ± 0.07 in Likert score 4, 0.02 ± 0.07 in Likert score 3 and 0.03 ± 0.08 in Likert score 2, p = 0.695. Nitrate dose ≥ 0.8mg was the only independent factor associated with the accuracy of the FFR_CT Planner (95%CI - 0.06 to - 0.001, p = 0.040).

Conclusion: The FFR_CT Planner was accurate in predicting post-PCI FFR independent of CCTA image quality.

Clinical relevance statement: Being accurate in predicting post-PCI FFR across a wide spectrum of CT image quality, the FFR_CT Planner could potentially enhance and guide the invasive treatment. Adequate vasodilation during CT acquisition is relevant to improve the accuracy of the FFR_CT Planner.

Key points: • The fractional flow reserve derived from coronary CT angiography (FFR_CT) Planner is a novel tool able to accurately predict fractional flow reserve after percutaneous coronary intervention. • The accuracy of the FFR_CT Planner was confirmed across a wide spectrum of CT image quality. Nitrates dose at CT acquisition was the only independent predictor of its accuracy. • The FFR_CT Planner could potentially enhance and guide the invasive treatment.

Keywords: Artifacts; Coronary CT angiography; FFRCT; Image quality; Percutaneous Coronary Intervention Planner.