Ann Thorac Surg 2006;81:1346-1347
© 2006 The Society of Thoracic Surgeons
Original article: Cardiovascular
Invited commentary
Katherine E. Maturen, MD,
David M. Williams, MD
Vascular and Interventional Radiology, Department of Radiology, University of Michigan, 1500 E Medical Center Dr, Ann Arbor, MI 48109-0030
(Email: kmulder{at}med.umich.edu; davidwms{at}med.umich.edu).
The authors [1] report a single center experience of 856 aortograms performed to evaluate suspected descending thoracic aortic injury from 1997 to 2004. In 206 patients, a computed tomographic (CT) examination preceded the aortogram, using a single-slice CT scanner until 2003 and a modern multidetector (16-slice) CT scanner thereafter. Any such study faces challenges (ie, maintaining a unified protocol despite rapid technical advances in imaging, encompassing a variety of clinical styles and levels of experience, accommodating the evolving paradigm and diagnostic demands of endovascular treatment of traumatic rupture, and accumulating enough patients in a reasonably discrete period when the prevalence of the index injury is less than 4%). The authors cannot hope to make everyone happy.
In the end, the authors limit their conclusions to two: (1) that chest computed tomography is an acceptable screening tool with high sensitivity, and (2) that 3-dimensional reconstruction tools are helpful but not conclusive for detecting injury. The authors acknowledge issues that qualify even the following modest claims: clearing the descending thoracic aorta in isolation has limited utility as injuries may be multiple, whereas artifacts and reader inexperience may limit 3-dimensional reformatting and other advanced CT techniques. Regarding the latter, our department and others have reported a less than 1% incidence of significant deviation between resident and staff readings of emergency CT scans. Furthermore, the importance of immediate definitive CT interpretation may be overemphasized, as many aortic ruptures are now treated in delayed fashion.
Does this study apply a fixed diagnostic algorithm to answer a specific clinical question in a well-defined population? Figure 3 documents a decline in aortography from a high of 180 in 1997 to a low of 40 in 2003. Computed tomographic scans have been steady at 30 to 40 per year. Thirty-one aortic injuries were found, 11 of them in the current era of the multidetector CT and 3-dimensional reconstruction. These 11 (30%) injuries were found in the latest 14 months (July 1, 2003 to August 31, 2004) using approximately 50 aortograms in contrast to 20 injuries (70%) in the preceding 78 months using 800 aortograms. Using multidetector computed tomography, we see a monthly incidence of aortic rupture three times that of the earlier era, and an aortography yield 10 times greater. It is hard to argue that the target population has been steady, or that the diagnostic algorithm is fixed. Ironically, just when gated 64-slice computed tomographies are about to stabilize the algorithm, the endograft era is changing the clinical question. We must still identify an injury, of course, but we must now also define the intimal tear and measure critical dimensions of the aorta.
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- Bruckner BA, DiBardino D, Cumbie T, et al. Critical evaluation of chest computed tomography scans for blunt descending thoracic aortic injury Ann Thorac Surg 2006;81:1339-1347.[Abstract/Free Full Text]
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