CT-derived anatomic high-risk features in patients with anomalous aortic origin of a right coronary artery correlate with an impaired FFR assessed by computational fluid dynamics
Authors: Ferroni A , Stark A W , Bigler M R , Giannopoulus A A , Raeber L , Graeni C 
Published: June 2023

Abstract

Funding Acknowledgements
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): FNSNF - Schweizerischer Nationalfonds zur Förderung der wissenschaftlichen Forschung.

Introduction
Anomalous aortic origin of a right coronary artery (AAORCA) are a rare subtype of coronary artery anomalies, which occur with a prevalence of 0.23% in the general population. Especially, AAORCA with an interarterial course between the aorta and the pulmonary artery confer high risk of myocardial ischaemia. The interarterial course is however only a surrogate marker for other anatomic high-risk-features (HRF) such as intramural course (IMC), slit-like ostium (SLO), proximal narrowing (PN), acute take-off angle (ATOA) and proximal elliptic vessel shape (PEV). Computed tomography-derived fractional flow reserve (CT-FFR) is a novel tool, which allows noninvasive assessment of haemodynamics, so far assessed in patients with atherosclerotic stenosis. Our aim was to investigate the correlation of HRF in AAORCA with CT-FFR of the anomalous vessel.

Purpose
In patients with newly detected AAORCA, it is important to evaluate the underlying mechanisms of hemodynamic relevance and currently it is unknown how- and which anatomical high-risk features correlate with ischemia in noninvasively assessed CT-FFR.

Methods
All patients with AAORCA, who underwent CT imaging between 12/2008 and 9/2022, were retrospectively enrolled. HRF were evaluated from CT images as following: IMC (i.e. length ≥5mm), SLO (i.e. stenosis grade of the proximal lumen compared to the distal lumen ≥50%), PN (i.e. stenosis grade of the proximal lumen to the first round lumen ≥50%), ATOA (i.e. &lt;45°) and PEV (i.e. length/width ratio &gt;1.3). Patients were divided into group 1 (≥4HRF) and group 2 (&lt;4HRF). FFR was calculated using computational fluid dynamics (CT-FFR) using Siemens CT Research cFFR and the cut-off &lt; 0.8 was considered hemodynamically relevant and correlations were performed.

Results
In total 47 patients, 56.7±14.2years, thereof 34 (72%) male were included in the final analysis. Mean CT-FFR for the anomalous vessel in the whole cohort was 0.93±0.05. IML, ATOA and PEV were present in all patients, whereas SLO was in 22 (46%) and PN in 11 (23%) present. 25 (53%) patients showed ≥4 HRF. In group 1 (≥4HRF), mean CT-FFR within the anomalous vessel was significantly lower compared to group 2 (&lt;4HRF) with 0.91 versus 0.95 (p = 0.002). Three patients (6%) showed a CT-FFR&lt;0.8 and were all within group 1. CT-FFR correlated significantly with SLO (r=-0.348, p = 0.017), but not with other HRF.

Conclusion
Patients with AAORCA and ≥4HRF showed lower CT-FFR values of the anomalous vessel compared to those with less high-risk features (i.e. &lt;4HRF). A minority of patients showed abnormal CT-FFR, all within the group with ≥4HRF. From all HRF, only SLO correlated with CT-FFR. Future studies need to assess how the combination of anatomical high-risk features and CT-FFR can be used for decision-making towards revascularization in AAORCA patients.