The Role of D-Dimer in Assessing for Aortic Dissection
January 2025
Author: Dr. Sasha Leibholz, MD PGY2
Peer Reviewer: Dr. Maria Mosley-Colón, MD PGY4
Faculty Editor: Dr. Sagar Nakrani, MD, Assistant Professor of Emergency Medicine at Weill Cornell Medical Center
The authors of this article have no financial or industry relationships to disclose.
Introduction
Aortic dissection is scary. The name itself is pretty dramatic, but the actual mechanics are even more terrifying. Aortic dissection is a condition marked by a tear in the intimal layer of the aortic wall, allowing blood to flow into the media layer and create a false lumen as it “dissects” the layers apart. As this occurs, mortality increases by 1-2% per hour if left untreated.
The gold standard imaging modality for diagnosis of aortic dissection is CT angiography (CTA), which is highly specific (94-100%) for the condition. Of course, in any Emergency Department, there will be many patients visiting on a given day whose chief complaints could be hypothetically attributed to a dreaded aortic dissection. Should we scan every single one of them? What about those patients for whom dissection is on the differential, but who we do not think are really dissecting? The patients we would assign less than a 2% pretest probability of acute aortic dissection – do even they require a CTA in every case? I suppose it depends on where you practice, but I would (and will) argue no. This diagnostic conundrum is a circumstance in which d-dimer, a blood test commonly used to assess for venous thromboembolism and point-of-care-ultrasound (POCUS) have shown promise as a potential screening tool for aortic dissection.
D-dimer in Aortic Dissection
Let’s first discuss why d-dimer would be elevated in aortic dissection. The d-dimer assay measures a fibrin degradation product that increases in the blood as clots are formed and then begin to break down. As we discussed, an aortic dissection begins with an intimal tear, allowing blood to flow into the media layer, creating a false lumen. Blood in this false lumen causes local activation of the coagulation cascade, causing formation of a thrombus. As fibrin cross-links within the thrombus, excess fibrin is also broken down in the process of fibrinolysis. As this occurs, fibrin degradation products such as the aforementioned d-dimer are released into the circulation. Thus, the release of d-dimer serves as a marker for active thrombus formation and breakdown, indicating the ongoing vascular injury and dynamic coagulation occurring in association with aortic dissection.
It’s worth noting off the bat that this test lacks any specificity for aortic dissection, meaning that a positive d-dimer value does not indicate a dissection. Elevated d-dimer levels can result from various conditions including pulmonary embolism, myocardial infarction, or even pregnancy, thus leading to a high rate of false positives (Shimony et al., 2011). Consequently, a positive d-dimer result cannot confirm an aortic dissection and requires further imaging for definitive diagnosis.
Even so, a negative value can give a pretty strong clue that no dissection is occuring. There is evidence that a negative d-dimer may effectively “rule out” aortic dissection in low-to-moderate risk patients. Let’s discuss three studies that support this idea.
Literature Review
Suzuki et al. (2009) performed a multicenter study demonstrating that a d-dimer level of less than 500 ng/mL had a high negative predictive value (NPV) for ruling out acute aortic dissection. In patients with suspected dissection, therefore, a low d-dimer reliably excluded the diagnosis. The patient population of this study included Emergency Department patients with suspected acute aortic dissection. In the study, d-dimer levels were measured at the time of presentation and patients were then evaluated using imaging studies (CT, MRI, or TEE) to confirm or rule out acute aortic dissection (AAD). The study found that a d-dimer cutoff of 500 ng/mL yielded a sensitivity of 100% for detecting AAD.
Mokhles et al. (2012) further expanded on this work in a cohort study evaluating d-dimer alongside clinical features in diagnosing aortic dissection. This study involved the measurement of d-dimer levels among various patient groups, including those with imaging-confirmed cases of AAD. The authors found that a low d-dimer level ( < 500 ng/mL) had a high negative predictive value for ruling out AAD, corroborating previous evidence. Overall, this study demonstrated that d-dimer has a sensitivity of 97% for ruling out AAD.
The same year, Sodeck et al. (2012) ran a prospective study analyzing patients who presented with suspected aortic dissection. For these patients, d-dimer levels were measured correlated with the results of imaging studies that either confirmed or ruled out dissection. The authors found that elevated d-dimer levels were, in fact, significantly associated with the presence of aortic dissection, with a sensitivity approximately 95-100%.
No test is without its weaknesses, and it’s worth noting that d-dimer levels vary depending on the timing of blood sample collection relative to symptom onset. Studies indicate that d-dimer levels peak shortly after dissection onset and may decrease quickly, within hours. A delay in testing could therefore result in false negatives and compromise the test's reliability as a rule-out tool. Hazui et al. (2005) demonstrated this phenomenon in their study analyzing whether d-dimer levels could reliably indicate the presence of AAD and how the timing of this test affected its diagnostic accuracy. The study included 62 patients with confirmed aortic dissection and 24 patients with other conditions that could mimic dissection. D-dimer levels were measured and compared across different time intervals after symptom onset, with testing within the first 24 hours from symptom onset demonstrating the highest sensitivity for diagnosing AAD. Sensitivity decreased slightly as time elapsed from symptom onset, suggesting that early testing maximizes diagnostic accuracy.
The Role of ADD-RS and POCUS
The ADD-RS assigns points based on high-risk conditions, pain features, and exam findings.
The ADD-RS assigns 1 point for:
High-risk conditions (e.g., Marfan syndrome, family history, thoracic aortic aneurysm).
High-risk pain features (e.g., abrupt onset, severe intensity, tearing quality).
High-risk exam findings (e.g., pulse deficit, systolic BP differential >20 mmHg, new murmur with pain).
A score of 0–1 combined with a normal d-dimer has a sensitivity of ~98% for ruling out dissection.
POCUS can complement this tools. The SPEED protocol—a focused ultrasound evaluation—assesses for pericardial effusion, aortic outflow tract dilation (>35 mm), and intimal flaps in the abdominal aorta. Studies suggest a sensitivity of 92% and specificity of 91%, making POCUS a valuable adjunct in low-risk scenarios.
Challenges in Diagnosing IMH and PAU
D-dimer’s utility diminishes in intramural hematoma (IMH) and penetrating atherosclerotic ulcer (PAU), conditions that can mimic dissection but have distinct pathophysiology. IMH lacks the intimal tear of a classic dissection, and its course is often more benign, though not without risks. Complications of IMH include progression to dissection (~30% of Type A cases), rupture, and aneurysm formation. PAU involves plaque erosion into the aortic media, typically in the descending thoracic aorta, with potential complications like hematoma, aneurysm, and rare progression to dissection. Because these entities lack the dynamic dissection seen in AAD, d-dimer is not consistently elevated, and scoring tools like the Aortic Dissection Detection Risk Score (ADD-RS) perform poorly, detecting only 50–70% of cases. This limitation underscores the need for imaging in patients with atypical presentations or low-risk ADD-RS scores when IMH or PAU is suspected.
A Practical Approach
In patients with suspected aortic dissection, clinical suspicion drives decision-making. For high-risk cases, CTA remains the gold standard. For low-risk patients (ADD-RS 0–1), combining d-dimer testing and POCUS can refine diagnostic accuracy. A negative d-dimer and normal POCUS effectively rule out dissection, while positive results warrant further imaging. If IMH or PAU is suspected, there are limitations of these tools and you should maintain a low threshold for imaging.
Clinical Approach
If clinical suspicion is high: Obtain STAT CTA.
If low suspicion (ADD-RS 0–1):
Perform d-dimer testing and/or SPEED protocol POCUS.
A negative d-dimer and normal POCUS can help exclude dissection.
Positive results necessitate further imaging, usually CTA.
References
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Hazui H, Fukumoto H, Negoro N, Hoshiga M, Muraoka H, Nishimoto M, Morita H, Hanafusa T. Simple and useful tests for discriminating between acute aortic dissection of the ascending aorta and acute myocardial infarction in the emergency setting. Circ J. 2005 Jun;69(6):677-82. doi: 10.1253/circj.69.677. PMID: 15914945.
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