Abstract
Acute aortic dissection can be fatal if overlooked, and the absence of D-dimer elevation can be used to exclude acute aortic dissection. However, we report a case of acute aortic dissection without D-dimer elevation. A man in his 70s presented to the emergency department with lumbar back pain. D-dimer was <1.0 µg/mL; however, acute aortic dissection was strongly suspected because of the sudden onset of lumbar back pain with a shifting location. Because of a difference in systolic blood pressure in both upper extremities, we performed a thorough examination using contrast-enhanced CT, leading to a diagnosis of acute aortic dissection. The patient was immediately referred to cardiovascular surgery and treated conservatively with antihypertensive management. The aortic dissection detection risk score (ADD-RS) classified the patient as high risk. This suggests the importance of using the D-dimer with the ADD-RS rather than solely relying on the D-dimer results to diagnose acute aortic dissection.
Keywords: Primary Care, Pericardial disease, Clinical diagnostic tests
Background
Acute aortic dissection is a disease that cannot be overlooked in the emergency department, as it can be fatal if discounted or treated too late. However, since various diseases present with symptoms of chest and back pain, it is impractical to perform contrast-enhanced CT in all cases. Additionally, it is widely known that a cut-off D-dimer value of 0.5 µg/mL has a 96% sensitivity for aortic dissection1 and is useful in ruling out the condition. It has also been reported that D-dimer combined with the aortic dissection detection risk score (ADD-RS), which evaluates the risk of acute aortic dissection by scoring patient background, nature of pain and physical findings, is useful as a diagnosis of exclusion.2 3 Although the D-dimer was not elevated in this case, the patient was at high risk with an ADD-RS score of 2, and indeed contrast-enhanced CT showed findings of acute aortic dissection. This suggested the importance of combining ADD-RS with the medical history, physical examination, and medical and family history rather than using D-dimer alone.
Case presentation
A man in his 70s presented to the emergency department with sudden onset of lumbar back pain. He had become aware of the onset of back pain while exiting his car, and after monitoring, he became aware of severe pain that moved from his back to between his shoulder blades while eating. He had a history of hypertension, which had been treated by a local physician and was well controlled. He also had a history of smoking 30 cigarettes per day between the ages of 20 and 73 years; however, there was no known history of alcohol consumption.
Investigations
Blood pressure measurements of the extremities showed right and left upper extremity blood pressures of 190/107 mm Hg and 167/80 mm Hg, respectively. According to the ADD-RS, the patient was at risk of sudden-onset, severe or tearing pain. In this case, the patient was also evaluated as high risk because of a difference in blood pressure in the upper extremities between the right and left sides of the body. Contrast-enhanced CT showed mild external diameter dilation from the aortic arch to the descending aorta and soft shadows without contrast extending beyond the calcification of the aortic wall, leading to a diagnosis of pseudoluminal aortic dissection (figure 1).
Figure 1.
Enhanced CT of the chest showing the increasing soft shadow of calcification of the descending aorta.
Differential diagnosis
Treatment
The patient was immediately referred to the Department of Cardiovascular Surgery, where he was urgently admitted with a diagnosis of Stanford type B acute aortic dissection and treated conservatively with antihypertensive therapy.
Outcome and follow-up
He was discharged home without any enlargement of the dissected lumen or symptoms of organ ischaemia.
Discussion
Delayed diagnosis of acute aortic dissection can be fatal, particularly for Stanford type A. It has been reported that the fatality rate increases by 1%–2% per hour of onset.4 The D-dimer is usually elevated in the pathophysiology of acute aortic dissection because it occurs during the lysis of the fibrin clot that forms during the haemostatic process of bleeding. Furthermore, the diagnostic accuracy of D-dimer in acute aortic dissection has been reported to have 96% sensitivity, 70% specificity and 0.06 negative likelihood ratio,1 making it an excellent biomarker to exclude the condition. However, in reality, D-dimer may not always be elevated in patients with high platelet counts or tiny dissection cavities.5 In this case, it was assumed that the D-dimer was not elevated because of the tiny dissection lumen. The contrast-enhanced CT scan was performed because of the presence of ADD-RS pain and physical findings. This case suggests that it is risky to exclude aortic dissection based on D-dimer. In fact, it has been reported that combining ADD-RS and D-dimer improves the accuracy of diagnosis in cases of suspected acute aortic dissection.6 The diagnostic accuracy of D-dimer when stratified by ADD-RS and D-dimer <500 ng/mL has 100% sensitivity when ADD-RS=0, and negative likelihood ratio of 0; sensitivity of 98.7% and negative likelihood ratio of 0.04 for ADD-RS ≤1; and sensitivity of 97.5% and negative likelihood ratio of 0.07 for ADD-RS ≥2. The accuracy of exclusion by D-dimer is one step lower in the high-risk group with an ADD-RS score of ≥2. Therefore, contrast-enhanced CT may be necessary for patients who are assigned to the high-risk group on the ADD-RS, as in this case, regardless of the D-dimer result. However, if the ADD-RS predicts low or intermediate risk, the D-dimer results could be used to determine whether contrast-enhanced CT should be performed. Furthermore, there are cases of acute aortic dissection with negative D-dimer similar to this case, suggesting that interpreting laboratory studies according to the patient’s risk based on clinical evaluation is crucial.
Learning points.
In high-risk groups for aortic dissection detection risk score (ADD-RS), there is a risk of missing the diagnosis when acute aortic dissection is excluded using D-dimer alone.
Clinical evaluation and contrast-enhanced CT are the pillars in diagnosing acute aortic dissection, and laboratory studies should be used as an adjunct because of the presence of negative D-dimer aortic dissection.
The D-dimer interpretation should be changed for each patient’s risk based on the clinical assessment in the ADD-RS.
Footnotes
Contributors: KS contributed to the design of the study, acquisition of data, interpretation of data and drafting the manuscript. SS contributed to interpretation of data, drafting the manuscript and revising the manuscript critically for important intellectual content. Both authors approved the final version of the manuscript.
Funding: The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests: None declared.
Provenance and peer review: Not commissioned; externally peer reviewed.
Ethics statements
Patient consent for publication
Obtained.
References
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