The impact of AAOCA anatomical characteristics in coronary blood supply
Authors: Lo Rito M , Anglese S , Rosato A , Arzuffi L , Deamici M , Negri J , Corrado C , Conti M , Frigiola A , Giamberti A , Bedogni F , Agnifili M L 
Published: October 2024

Abstract

Background
Impact of AAOCA in coronary blood flow and myocardial perfusion is an unknown field although it is well-accepted that the anomaly is one of the leading causes of sudden death during effort. The risk factors for AAOCA are the anatomical characteristics of the abnormal vessel, such as the presence of intramural (IM) segment, the ostium shape, and the take-off angle.

Purpose
We aim to evaluate the impact of AAOCA anatomical risk profile in the blood flow using the thermodilution technique, an accurate and reproducible method used to investigate coronary physiology.

Methods
This is a single-centre prospective study that included AAOCA subjects who underwent invasive thermodilution functional coronary assessment. We divided patients into two groups according to the anatomical risk profile: a) ischemic risk (IR): concomitant presence of IM segment, take-off angle&lt;45°, and slit-like/oval shape ostium, or a IM length&gt;10 mm; b) no-ischemic risk (no-IR): absence of IM segment, take-off angle&gt;45°, round ostium. We obtained coronary functional measures using the thermodilution method. We measured the absolute flow, and coronary resistance at rest and maximal hyperemia. Data were reported as median and IQR and we used Wilcoxon signed-rank test for paired data in the rest vs. hyperaemia comparison.

Results
We included 28 AAOCA pts (22 male, 6 female, median age: 48.6 (IQR: 18.9) ) that were 20 anomalies of the right coronary and 8 of the left. Symptomatic subjects (n=16) presented with angina (n=12), syncope (n=1), presyncope (n=1), fatigue (n=1), and dyspnea associated with arrhythmia (n=1). The IR group (26 pts; R-AAOCA=24, L-AAOCA=2) has an IM segment with a median length of 10 mm (IQR: 5.5), a median take-off angle of 28° and the ostium was slit-like (n=16), oval (n=10), and round (n=1). The no-IR group consisted of 9 (R-AAOCA=3, L-AAOCA=6), median take-off angle of 69° and the ostium was oval (n=1), and round (n=8). The absolute flow and coronary resistance at rest of the IR group did not have significant differences compared to no-IR. Hyperemia determines an increment of coronary flow in both groups although the IR had a 2.9 fold increase and the no-IR as 3.5 fold increase compared to rest. In particular, the absolute flow of the IR group was significantly lower compared to the no-IR group (185 vs. 330 mL/min, p=0.012) and there was a greater coronary resistance (419 vs. 268 mmHg/(mL/min), p=0.027), as shown in Fig. 1.

Conclusions
Anatomical risk factors of AAOCA, such as IM take-off angle and ostium morphology, have a negative impact on the coronary blood supply that is reduced when compared to AAOCA without such anatomical features. Such impact can be revealed also at rest using the thermodilution method that induces maximal coronary vasodilatation that is the natural coronary response to physical effort. Further studies are needed to validate benefit of functional assessment in AAOCA risk stratification.