Benjamin Starnes (Seattle, USA) told the audience attending yesterday’s mini symposium on acute aortic transection that intravascular ultrasound (IVUS) was an important tool in the management of patients with blunt aortic injury undergoing thoracic endovascular aortic repair (TEVAR) because it helps to ensure accurate sizing of the endograft and prevent rupture. The session also reviewed the differences between image-based classifications of blunt aortic injury.
Starnes reported that, over the past decade, endovascular repair of patients with blunt traumatic aortic injury has become the “predominant approach to fixing these injuries”, but added that there were “unique challenges” to using the endovascular approach. He said: “One of challenges is the dynamic nature of the aorta. There are some interesting data from blood-letting studies in Yorkshire pigs that show significant decrease in aortic diameter accompanying induced haemorrhagic shock, with a dose-dependent effect.”
According to Starnes, aortic diameter is also known to increase after resuscitation and the area with the greatest change in size is the area that is most commonly injured in blunt trauma (ie. the isthmus and descending aorta). He added: “CT angiography is used for diagnosis of these injuries and axial slices from the initial scan are often used for planning and sizing of the repair. While using IVUS at the time of repair to better characterise the injury, we noticed a difference in the aortic diameter with systolic variation [compared with the diameter observed on the initial CT angiography]. This then begs the questions “Is initial CT angiography appropriate for sizing the endograft in these patients?” and “Is that endograft going to be undersized once that patient is fully resuscitated?”
Starnes and colleagues, therefore, conducted a retrospective chart review of patients with blunt aortic injury who underwent TEVAR at their level-one trauma centre to determine if there was a difference between the aortic diameter observed on diagnostic CT angiography and that observed on IVUS at the time of the repair. The inclusion criteria were initial admission or pre-admission CT angiography, IVUS at the time of repair, and a post-implant CT angiography. Of the 26 patients who were treated at the centre during the study period (July 2007–July 2011), three patients did not have post-implant CT angiography information, one patient was converted to surgery, and six patients did not receive IVUS—leaving 16 patients available for assessment.
There was a significant difference of 2.4mm between mean aortic diameter with initial CT angiography and mean aortic diameter with IVUS: 21.7mm vs. 24mm, respectively (p=0.004). Starnes noted: “When we look at post-implant CT angiography compared with initial CT angiography, there is again a highly significant difference of 3mm (p=0.0001). But, when we compared post-implant CT angiography with IVUS, there was no difference.” He added that when they reviewed theoretical graft diameters, there was a significant difference of 2.4mm (p=0.003) between the size of the graft that would be chosen based on the initial CT angiography and that based on IVUS at time of repair. There was also a significant difference in graft size between post-implant CT angiography and initial CT angiography (3mm; p=0.0002), but no difference in size between post-implant CT angiography and IVUS.
“I believe IVUS is a critical and important tool for the management of patients with blunt aortic injury,” Starnes concluded.
Ali Azizzadeh (Houston, USA) also presented data at the mini symposium, reviewing the long-term effects of intentional stent graft coverage of the left subclavian artery (in patients with blunt aortic injury undergoing TEVAR). He said that in a review of 82 patients undergoing TEVAR at his centre between September 2005 and July 2012, 50 received intentional stent graft coverage of their left subclavian artery. Azizzadeh reported: “Intentional coverage of the left subclavian artery during TEVAR for blunt aortic injury appears safe without compromising mental or physical health outcomes. Furthermore, left artery stent coverage does not increase the long-term risk of upper extremity symptoms or impairment of normal activities.”
Does intramural haematoma exist?
As well as presenting data for the role of IVUS in the management of patients with aortic, Starnes also reviewed the classification of the injury. He reported that he and his colleagues developed a new image-based classification system for these types of injury because they believed the current classification system, by the Society for Vascular Surgery (SVS), was “lacking”. Starnes explained: “The SVS system has four grades of injury—grade one, intimal tear; grade two, intramural haematoma; grade three, pseudoaneurysm; and grade four, rupture—but does not provide for any treatment recommendations because grades one to three are treated the same and we do not believe grade two exists. In a review of 140 aortic transections at our centre, we did not see a single case of intramural haematoma.”
Therefore, they developed a new classification system based on the presence or absence of an aortic external contour abnormality. Under this new system, intimal tear (intimal defect and/or thrombus of
However, Michael Dake (Stanford, USA) commented that there was a lack of consensus surrounding intramural haematoma as unlike Starnes and colleagues, Rabin and colleagues did recognise the existence of intramural haematoma and classified it as being a “grade one” injury (in contrast to the SVS classification). He added that Osgood and colleagues, in an another system, classed intramural haematoma as being “grade 1B” but he noted that they did not find any patients with that type of injury in their series. Dake reported, regardless of how it was classified, recent publications have suggested that: “Intramural haematoma without associated peri-aortic component, contour abnormality, or pseudoaneurysm may be conservatively managed with appropriate follow-up imaging.”