**4. Technique of epiaortic (epivascular) ultrasound examination**

The sequence and technique have been previously published (Royse and Royse 2006) Fig. 4 or with Guidelines (Glas, Swaminathan et al. 2008). One important point to appreciate is that the orientation of the aorta to orthogonal planes is highly variable. For accurate crosssectional dimensions, the ultrasound probe needs to be oriented at 90 degrees to the aorta irrespective of the relationship to the orthogonal plane, Fig. 5. This is not difficult to achieve, and it is obvious as you simply rotate the probe to produce a circle on the screen; yet it is a common failing in the early learning experience.

The technique of aortic clamping itself varies, with the repeated application of the aortic clamp rather than the "single clamp" technique; and use of the partial occlusion clamp for the construction of proximal aortic coronary anastomoses, further manipulates the aorta and will lead to greater propensity for dislodgement of any existing aortic atheroma. In particular, the typical Kaye-Lambert partial occlusion ("side biting") clamp will usually occupy the majority of the ascending aorta in a vertical plane and about half of the cross sectional diameter of the aorta in the horizontal plane, see Fig. 3. This clamp will therefore manipulate a considerable part of the ascending aorta even with only one application; and

repeated applications would be common.

Fig. 3. Partial occlusion clamp manipulates most of the ascending aorta

common failing in the early learning experience.

**4. Technique of epiaortic (epivascular) ultrasound examination** 

The sequence and technique have been previously published (Royse and Royse 2006) Fig. 4 or with Guidelines (Glas, Swaminathan et al. 2008). One important point to appreciate is that the orientation of the aorta to orthogonal planes is highly variable. For accurate crosssectional dimensions, the ultrasound probe needs to be oriented at 90 degrees to the aorta irrespective of the relationship to the orthogonal plane, Fig. 5. This is not difficult to achieve, and it is obvious as you simply rotate the probe to produce a circle on the screen; yet it is a

Fig. 4. Standardised epiaortic echocardiography examination. (Royse and Royse 2006) Intraoperative ultrasound examination of the aorta and proximal coronary arteries 10 standard views, 2 supplementary views. LAX, longitudinal axis, SAX, short axis, RCA, right coronary artery, SoV, Sinus of Valsalva, AV, aortic valve, RCC, right coronary cusp of aortic valve, LCC, left coronary cusp, NCC, non coronary cusp, ST Jn, sinotubular junction of aorta, ALMV, anterior leaflet of mitral valve, RV, right ventricle, RVOT, right ventricular outflow tract, MPA, main pulmonary artery, PV, pulmonary valve, LA, left atrium, LAD, left anterior descending artery, Cx, circumflex coronary artery, SVC, superior vena cava, RA, right atrium, RPA, right pulmonary artery, Z1, zone 1 or proximal ascending aorta, Z2, zone 2 or mid ascending, Z3, zone 3 or distal ascending, Z4, zone 4 or proximal aortic arch, Z5, zone 5 or distal aortic arch, RMB, right main bronchus, LMB, left main bronchus, RBCA, right brachiocephalic artery, LCC, left common carotid artery, LSA, left subclavian artery. Reproduced from Royse A and Royse C. A standardised intraoperative ultrasound examination of the aorta and proximal coronary arteries. Interact CardioVasc Thorac Surg 2006;5:701-704. © 2006 European Association of Cardio-Thoracic Surgery with permission from the European Association of Cardio-Thoracic Surgery.

Epiaortic Ultrasound Assessment of the Thoracic Aorta in Cardiac Surgery 43

A variety of ways exist to allow a sterile acoustic interface for the probe. The simplest is to partially fill a sterile plastic cover with saline - either a custom made bag or a bag adapted from another use such as an endoscopic camera cover. Alternatively, sterile gel may be placed within the bag as the internal acoustic couple. Some fill the pericardium with warm saline to enhance the external acoustic couple; most do not. One important point that is often overlooked is the issue of "near field crowding". What this refers to is the need to maintain some distance between the ultrasound probe and the structure being imaged in order for the ultrasound to travel some distance, and then be reflected from the structure back to the probe. This is important for visualising the superficial (anterior) aortic wall. This wall cannot be adequately imaged when the probe is resting directly on the surface; and in order to adequately image this part of the aorta, the probe needs to be moved away from the aorta by 0.5-1.0 cm. Of course the acoustic coupling between the probe and the structure in question needs to be maintained, but generally this is not a problem when saline has been

There is no rationale or valid reason for any particular order or protocol to be followed whilst performing a study. However, it makes logical sense to follow a routine in order to efficiently complete a comprehensive study. See Fig. 4 for a proposed sequence. Specialpurpose ultrasound examinations may be performed without the need for a comprehensive examination. One example may be to interrogate flow in the right coronary artery following an aortic valve replacement where there is some doubt as to whether the prosthesis was

The operator performing the ultrasound examination is (or should be) the surgeon. The anaesthetist should be recording sample images or video loops as the examination is being performed so that appropriate archiving of the findings occurs. The fascinating thing about the subject of atheroma detection and this ultrasound examination is that very little new knowledge or new techniques have occurred in the past 10-15 years. The evidence is very strong that the performance of this study accurately establishes the presence and location of aortic atheroma and provides the surgeon with a greater range treatment options. Remarkably, this is not a routine part of every cardiac surgical procedure! Indeed only the minority of surgeons actually perform epiaortic ultrasound examinations and even fewer

This ultrasound examination pertains almost exclusively to cardiac surgery. It could quite easily be applied to any other forms of surgery involving examination of large arteries or veins. At the current time intraoperative transoesophageal echocardiography is routine in many parts of the Western world, and becoming more common in the developing world. Therefore generally there is a good level of basic ultrasound experience and knowledge amongst surgical staff from the general observation of ultrasound being performed. However, at present few will be actively performing ultrasound examinations such as transthoracic echocardiography, ultrasound guided procedures or venous duplex studies all of which are becoming standard practice in advanced cardiac surgical centres. With this familiarity, the performance of epiaortic ultrasound examination is extremely simple to implement and to teach since there is significant underlying theoretical and practical experience. For those who have not performed ultrasound examinations before themselves;

used within the plastic bag in which the probe is suspended.

obstructing the flow to this coronary artery.

still, perform this on a routine basis.

**5. Training** 

Fig. 5. Ultrasound images of aorta. A angles of ultrasound probe. B Zone 1, C Zone 2, D Zone 3, E Aortic arch, F Cerebral vessels. Other abbreviations as for Fig. 4.Ultrasound probe selection is important. A phased, linear array probe with a frequency in the rage 8-12 Mhz is preferred. Some attention to the physical size is also important as a large probe may not easily fit in the sternotomy wound, and a round probe is difficult to hold or to maintain orientation. If the frequency is too high, then the depth of penetration may be sufficiently limited so as to preclude adequate imaging of the posterior aortic wall.

A variety of ways exist to allow a sterile acoustic interface for the probe. The simplest is to partially fill a sterile plastic cover with saline - either a custom made bag or a bag adapted from another use such as an endoscopic camera cover. Alternatively, sterile gel may be placed within the bag as the internal acoustic couple. Some fill the pericardium with warm saline to enhance the external acoustic couple; most do not. One important point that is often overlooked is the issue of "near field crowding". What this refers to is the need to maintain some distance between the ultrasound probe and the structure being imaged in order for the ultrasound to travel some distance, and then be reflected from the structure back to the probe. This is important for visualising the superficial (anterior) aortic wall. This wall cannot be adequately imaged when the probe is resting directly on the surface; and in order to adequately image this part of the aorta, the probe needs to be moved away from the aorta by 0.5-1.0 cm. Of course the acoustic coupling between the probe and the structure in question needs to be maintained, but generally this is not a problem when saline has been used within the plastic bag in which the probe is suspended.

There is no rationale or valid reason for any particular order or protocol to be followed whilst performing a study. However, it makes logical sense to follow a routine in order to efficiently complete a comprehensive study. See Fig. 4 for a proposed sequence. Specialpurpose ultrasound examinations may be performed without the need for a comprehensive examination. One example may be to interrogate flow in the right coronary artery following an aortic valve replacement where there is some doubt as to whether the prosthesis was obstructing the flow to this coronary artery.

The operator performing the ultrasound examination is (or should be) the surgeon. The anaesthetist should be recording sample images or video loops as the examination is being performed so that appropriate archiving of the findings occurs. The fascinating thing about the subject of atheroma detection and this ultrasound examination is that very little new knowledge or new techniques have occurred in the past 10-15 years. The evidence is very strong that the performance of this study accurately establishes the presence and location of aortic atheroma and provides the surgeon with a greater range treatment options. Remarkably, this is not a routine part of every cardiac surgical procedure! Indeed only the minority of surgeons actually perform epiaortic ultrasound examinations and even fewer still, perform this on a routine basis.
