**7.2 Intramural hypoplasia**

An IVUS hypoplasia of the intramural segment is demonstrated with a ratio <1.0 between the intramural minimal circumference and the distal reference circumference. The length of the intramural segment, generally ranged from 5 to 15 mm, may vary depending of the site of the ectopic orifice. The narrowing diameters and surfaces must be compared with the distal reference parameters. The baseline area of stenosis is the ratio between the distal area (mm2) minus the intramural area (mm2), and the distal area (mm2). The degree of area obstruction varies between 30 and 70%.

Proximal Anomalous Connections of Coronary Arteries in Adults 207

echocardiography (TEE) may improve the imaging quality (figure 19) but not necessarily the diagnostic ability. Several studies have reported the echocardiographic prevalence of ANOCOR particularly in paediatric populations or young adults. An anomalous connection with the opposite sinus was found in 4 cases (0.2%) in a series of 2388 children or adolescents referred for innocent murmurs or functional assessments (Davis et al., 2001), and in 3 cases (0.09%) in 3504 (mean age, 30 years) asymptomatic athletes (Zeppilli et al., 1998). In the latter study a clear visualization of both ostia was obtained in 90% of cases. Therefore, the echographic prevalence is lower than those reported with selective coronary angiography and tomographic imaging techniques. The limited discriminating power of TTE to distinguish some ANOCOR may explain this discrepancy. TTE lacks reliability to identify a small RCA or CX coronary artery with an ectopic origin. Besides, an ectopic vessel with preaortic course crosses very closely the appropriate sinus, and thus may pretend a normal origin. Nevertheless, in young adults or in patients with a satisfactory acoustic window, several echographic characteristics must be known (Cohen et al., 2010). An abnormal diastolic colour flow between the aorta and the pulmonary trunk is often the first identification of an ANOCOR with a preaortic course. However, only the first millimetres of the ectopic vessel are visualized, and, often, the TTE is inconclusive in ruling out some ectopic paths. Thus, a suspected retroinfundibular or preaortic course with TTE should be always confirmed with other imaging modalities. In addition, TTE is not able to describe the shape of an ectopic orifice and to measure a possible ostial narrowing. TEE may identify some high take-off above the sinotubular junction with the long-axis view. Echographic diagnosis of anomalous origin of the LCA from the pulmonary trunk is mainly based on indirect features with a dilation of the RCA and a multiple collateral flow through the interventricular septum. In practice, the management of an ANOCOR should never be

discussed with only echocardiographic imaging in adult patient.

retroaortic course.

Fig. 19. Short-axis transoesphageal echocardiographic view showing an ectopic circumflex coronary artery (arrows) coursing between the aorta (AO) and the left atrium (LA) with a

**AO**

**LA**

### **7.3 Lateral compression**

The intramural segment of the ectopic has an abnormal shape (figure 18), resulting from a shared media with the aorta and a probably incomplete growth of the ectopic vessel in the aortic wall. The cross section is more or less oblong. The lateral compression is defined as a smaller area than that possessed by a circle of the same circumference. This parameter is quantified with the asymmetric ratio of the smallest to the largest diameter <1.0.

Fig. 18. Intravascular ultrasound images showing the intramural segment (A) and the extramural segment (B) of an ectopic right coronary artery connected with the left sinus.

Despite first promising results, the IVUS imaging tool has several limits. Non selective canulation of the vessel may disrupt the procedure. The possibility of artefacts has been pointed out, as well as the decreasing in the precision of measurements, due to the tangential orientation of the vessel (Angelini & Flamm, 2007). Moreover, ST-T changes and angina may occur during IVUS manoeuvres.
