Ann Thorac Surg 2008;85:1782-1784. doi:10.1016/j.athoracsur.2007.11.005
© 2008 The Society of Thoracic Surgeons
Case Reports
Ascending Aortic Dissection: Look Again Before You Leap
Michael S. Firstenberg, MD*,
Juan A. Crestanello, MD,
Chittoor B. Sai-Sudhakar, MBBS,
John H. Sirak, MD,
Benjamin Sun, MD
Department of Cardiothoracic Surgery, The Ohio State University, Columbus, Ohio
Accepted for publication November 2, 2007.
* Address correspondence to Dr Firstenberg, Department of Cardiothoracic Surgery, North Doan Hall, 8th Floor, The Ohio State University, Columbus, OH 43210 (Email: michael.firstenberg{at}osumc.edu).
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Abstract
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Advances in imaging technology can provide a potentially more accurate, precise, and timely diagnosis. However, false-positive results, particularly when acute aortic pathology is being considered, can lead to unnecessary interventions. We present a case of a computed tomography scan that was false-positive for aortic dissection and highlight the importance of confirmatory studies.
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Introduction
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Acute dissections of the ascending aorta represent true surgical emergencies, with a mortality rate at 48 hours of 50% [1]. As such, a prompt and accurate diagnosis is critical in identifying patients who require emergency surgical intervention. Just as critical: identifying those who do not have a dissection can guide further diagnostic management or avoid unnecessary sternotomy, cardiopulmonary bypass, and a negative aortic exploration.
Improvements in imaging technology have resulted in highly sensitive and specific diagnostic tools; however, more widespread use may increase the number of false-positive results on tests. Therefore, before any invasive intervention, understanding the limits of imaging technology and confirmatory testing is critical. We present a case of an aortic dissection, initially diagnosed with computed tomography (CT) scanning, which on further confirmatory testing proved to be an artifact and prevented unnecessary surgery.
The patient is a 41-year-old, non-English-speaking woman. She had no known medical problems because she was a recent immigrant and had no previous access to health care. The patient resented to another hospital, with the assistance of a family member translating, complaining of chest and back pain. Her blood pressure was 150/100 mm Hg in both arms and heart rate was 110 beats/min. Results of an electrocardiogram (ECG) and tests of cardiac enzymes were normal, and she had strong peripheral pulses.
A contrast spiral CT scan of the chest revealed an acute dissection of the ascending aorta (Fig 1). She was transferred to our institution for surgical management. Upon arrival, she was hemodynamically stable. A transesophageal echocardiography (TEE) showed no aortic pathology (Fig 2). Because of the high concern from the initial CT scan, a repeat ECG-gated CT scan was performed, and this too showed no aortic pathology (Fig 3). Then, to definitively rule out a potentially lethal problem, magnetic resonance imaging was performed, and this result was also normal (Fig 4).
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Fig 1. The initial multidetector computed tomography scan of the chest with contrast suggested an ascending aortic dissection with a false lumen extending into the arch, without descending involvement.
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Fig 2. Transesophageal echocardiography, with extensive scanning though the aorta, failed to reveal any pathology despite the previous computed tomography scan findings.
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Fig 3. A repeat multidetector, contrast-enhanced, electrocardiograph-gated, computed tomography of the chest demonstrated an aorta of normal sized and caliber. The previously visualized flap was not seen.
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Fig 4. Magnetic resonance imaging (MRI) shows no evidence of intraaortic pathology from the proximal ascending aorta (shown) to the aortic bifurcation.
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The patient, now pain free, was subsequently started on antihypertensive medications, and medical follow-up was arranged. She is doing well, without problems.
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Comment
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Our case illustrates one of the many pitfalls of advanced imaging technology, particularly in the absence of a reliable history as a result of communication and cultural barriers. With an increasing reliance on noninvasive imaging, the rates of false-positive results, although rare in incidence, may be more common in frequency. The potential complications of errors in diagnosis can be severe, however. Because of these concerns, it is our policy to perform a different confirmatory study before an operative intervention. Even in unstable patients brought directly to the operating room, a TEE is performed before the incision. Although this may seem intuitive, a review of the International Registry of Acute Aortic Dissection (IRAD) database suggests many patients are operated on after a single test, with the number of studies performed at United States sites (1.71 ± 0.76) significantly lower than at non-United States centers (1.94 ± 0.83, p < 0.0005) [2].
Traditional CT scanning has a reported sensitivities ranging from 83% to 94% and specificities of 87% to 100% for all aortic dissections; however, with ascending dissections, the sensitivity can be less than 80% [3]. Helical or spiral CT is reported to be more accurate, with Hayter and colleagues [4] reporting no false-positive results and 99% to 100% sensitivities, specificities, positive/negative predictive vales, and accuracies, but our cases suggests otherwise. Magnetic resonance imaging has reported sensitivities and specificities of 95% to 100%. Transesophageal echocardiography, a quick bedside or intraoperative test, despite operator dependence, is also very sensitive (about 98%) and specific (63% to 96%); but clearly, none of these tests are 100% accurate [3].
Although CT scans are known to be extremely valuable, understanding the potential causes for false-positive results is vital. Abnormal venous structures, such as a low-lying left innominate or left pulmonary vein can mimic an aortic flap. A large contrast bolus at the time of the procedure or motion can result in imaging artifacts. Another potential for a false-positive result is a thickened pericardium closely adherent to the ascending aorta [5]. The incidence of false-positive scans that result in negative explorations is unknown and probably underreported. The cause of our initial false-positive scan probably reflects a combination of motion and contrast artifacts from pulmonary artery reflections.
Recognition of the limitations of current technology can present a diagnostic dilemma. Often patients are initially seen at smaller centers that may be less versed in understanding the evaluation of complex and maybe infrequently observed problems, which may lead to overcalling a diagnosis in fear of missing a fatal problem. Hence, these patients are transferred with a potentially erroneous diagnosis.
It is important to recognize that no single test is 100% perfect. Confirmatory studies, especially when clinical judgment questions initial test results, are critical in avoiding the potential for a negative aortic exploration.
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References
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- Anagnostopoulos CE, Prabhakar MJ, Kittle CF. Aortic dissections and dissecting aneurysms Am J Cardiol 1972;30:263.[Medline]
- Moore AG, Eagle KA, Bruckman D, et al. Choice of computed tomography, transesophageal echocardiography, magnetic resonance imaging, and aortography in acute aortic dissection: International Registry of Acute Aortic Dissection (IRAD) Am J Cardiol 2002;89:1235-1237.[Medline]
- Khan IA, Nair CK. Clinical, diagnostic, and management perspectives of aortic dissection Chest 2002;122:311-318.[Medline]
- Hayter RG, Rhea JT, Small A, Tafazoli FS, Novelline RA. Suspected aortic dissection and other aortic disorders: multi-detector row CT in 373 cases in the emergency setting Radiology 2006;238:841-852.[Abstract/Free Full Text]
- Shanmugam G, Mckeown J, Bayfield M, Hendel N, Hughes C. False positive computer tomography findings in aortic dissection Heart Lung Circ 2004;13:184-187.[Medline]
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Abstract
Introduction
