Year : 2013 | Volume
: 16 | Issue : 3 | Page : 226--227
In response to, aortic dissection: To be or not to be?
Bhupesh Kumar, Aveek Jayant
Department of Anaesthesia and Intensive Care, Post Graduate Institute of Medical Education and Research, Chandigarh, India
Department of Anaesthesia and Intensive Care, Post Graduate Institute of Medical Education and Research, Chandigarh - 160 012
|How to cite this article:|
Kumar B, Jayant A. In response to, aortic dissection: To be or not to be?.Ann Card Anaesth 2013;16:226-227
|How to cite this URL:|
Kumar B, Jayant A. In response to, aortic dissection: To be or not to be?. Ann Card Anaesth [serial online] 2013 [cited 2020 Aug 12 ];16:226-227
Available from: http://www.annals.in/text.asp?2013/16/3/226/114246
We read with interest the case reported by Baloria et al., and the editorial on the article. , The clinical spectrum of acute aortic syndromes is expanding; it is only natural that the conundrum surrounding their imaging evolves in parallel.  We describe a parallel confounder in echocardiography. During transesophageal echocardiography, side lobe artifact in ascending aorta often mimics a dissection flap.  It arises from a bright echo at sinutubular junction resulting in an unnaturally curvilinear echo extending along the direction of scan plane lines within the lumen of aorta. It can be differentiated by true dissection flap by:
Rigid and fixed location of artifact with respect to aortic wall as opposed to random mobility of a true dissection flap.Progressively diminishing intensity of artifact in contrast to homogenous echo intensity of true dissection flap along its course.An artifact often disregards the normal anatomic boundary and is seen crossing the aortic wall.Color flow imaging shows no margination of color in case of artifact in contrast to margination of color flow by true dissection flap.
Similarly, a flap seen on conventional computerized tomography angiography could be a motion artifact in around one third of cases. In majority, it occurs at the anterior-left and posterior-right margin of aortic circumference corresponding with the direction of systolic aortic motion. It virtually never occurs in the true right or left posterior position.  Sometimes it appears as a low attenuation line extending beyond the wall of ascending aorta into the adjacent mediastinum.  Once suspected it can be ruled out by electrocardiogram gated computed tomography as described in the editorial. 
In the case described by Baloria et al., the false positive diagnosis can be attributed to a motion artifact as supported by the location of the apparent flap-right posterior as has been reported previously.  However, the patient also presented with an acute onset chest pain with dyspnea. A large pericardial effusion that the patient was subsequently noted to have could have caused chest pain with dyspnea. Acute chest pain can also be caused by non-dissection acute aortic syndromes; they should ordinarily be considered in the differential diagnosis. Figure 1 of the indexed article shows a crescent shaped separate lumen (potential true lumen of a dissection) and a larger, similarly enhancing possible false lumen. The crescent structure could equally represent an intramural hematoma (IMH).  However, this cannot be an IMH because IMH does not enhance and there is no dissection flap; it is actually better delineated on a plain non-contrast scan because of its relative higher attenuation.  IMH has other distinguishing features such as constant relationship relative to the aorta while a dissection classically spirals around the aorta in a longitudinal fashion, as it progresses.  That this patient did not have an IMH is confirmed further by the epiaortic scan [Figure 5 of the indexed article], which shows an aortic wall of homogeneous echo density and a normal wall thickness.  IMH as a pathologic entity deserves to be highlighted as the presence of a pericardial effusion with potential aortic pathology is an ominous marker of severity.
Thus, as the diagnostic umbrella of acute aortic conditions extends beyond the spectrum of dissection, anesthesia providers need to constantly be aware of the pitfalls of each diagnostic modality to confirm or exclude these conditions. Systematic ruling out of these conditions using a diagnostic modality or the other must, as the editorial points out, be based on the unpleasant consequences a false negative diagnosis portends and the urgency of reaching an appropriate decision. 
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