Comparison of CT-FFR to invasively measured FFR adenosine and FFR dobutamine in patients with an anomalous aortic origin of a right coronary artery
Authors: Stark A W , Ferroni A , Bigler M R , Giannopoulos 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) is a rare congenital anomaly. Malignant AAORCA with an interarterial course between the great arteries inherit an anticipated higher risk for myocardial ischemia. Anatomical high-risk features are beside the interarterial course the slit-like ostium (SLO), elliptic vessel shape (EVS), proximal narrowing (PN), acute take-off angle (ATOA) and an intramural course (IM) inside the aortic wall. The complex anatomy lead to both a fixed and further dynamic component of anomalous vessel compression. The suggested gold-standard for the assessment of combination (i.e. fixed and dynamic component) is invasively measured fractional flow reserve (FFR) during dobutamine and volume challenge, whereas FFR under adenosine may only cover the fixed components. A possible non-invasive alternative for FFR assessment is novel CT-FFR method, which can calculate FFR from coronary computed tomography angiogram (CCTA) images using computational fluid dynamics (CFD).

Purpose
CT-FFR may be used as a non-invasive alternative to invasive FFR measurements. Our aim was to compare CT-FFR to invasively measured FFRadenosine and FFRdobutamine in patients with AAORCA.

Methods
Consecutive patients enrolled in the NARCO trial (i.e. Noninvasive anatomical assessment for ruling out hemodynamically relevant coronary artery anomalies – A comparison of coronary-CT to invasive coronary angiography), with AAORCA undergoing CCTA and invasively measured ischemia assessment were included. All patients underwent CCTA for quantification of anatomical high-risk features and analysis of CT-FFR, invasive coronary angiography using FFR with adenosine (140μg/kg/min) and secondly with dobutamine and volume challenge (40 μg/kg/min + saline: 1.5–3 l+ atropine: 1 mg). Comparison between different methods was performed.

Results
In total, 29 consecutive patients with an AAORCA with an interarterial course (56 ± 13 years old), 22 (76%) male patients who underwent both CCTA and invasive coronary angiography were included. SLO was present in 18 (62%), PN in 5 (17%), EVS in 29 (100%) and an ATOA in 29 (100%) patients. An IM was present in 28 (97%) with a mean length of 11 ± 4 mm. While there was no difference between CT-FFR and FFRadenosine (p = 0.656), the mean invasive measured FFRdobutamine (0.85 ± 0.11), was significantly lower than FFRadenosine (0.88 ± 0.10, p = 0.002) and trend towards lower values than CT-FFR (0.89 ± 0.06, p = 0.063).

Conclusion
In patients with AAORCA, CT-FFR shows no difference with FFRadenosine, but they both overestimate FFR compared to FFRdobutamine gold-standard. Hence, there is a need for CCTA derived CFD FFR models, including dynamic components and mimicking FFR under dobutamine stress.