AorticDissection.com-D-Dimer Test
 

Hi Brian,

Just thought that you should get the word out that there is a recent blood test that is great for aortic dissection.  Most of the work on this was in Europe.  Basically, it has been found that all acute aortic dissections thus far checked have an elevated d-dimer blood test and there have been no acute aortic dissections that have had negative d-dimer tests.

  This was discovered recently by Weber and others.  It was discovered because a d-dimer test was developed to detect blood clotting such as in pulmonary emboli and DVT (deep venous thrombosis) in the legs.  The current procedure to rule out a pulmonary embolism is a Chest CT (done for a positive d-dimer) with a number of dissections then discovered by accident. They then checked autopsy records of people sent home that died of a dissection and then checked hospital records, and sure enough, those that had a d-dimer test were positive.  Many of those people had a nuc med lung scan instead of a CT to exclude PE  (only the CT will discover the dissection by accident). 

Dean Easton MD, Radiologist
Las Vegas, NV

http://www.labtestsonline.org/understanding/analytes/d_dimer/test.html

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Hi,
Here are some articles on the d-dimer test now being a good test for aortic dissection.  Basically, if positive, DVT, PE, and aortic dissection need to be excluded with a CT of the chest and Doppler venous study of the legs. 
Dean Easton MD 
 
http://www.aemj.org/cgi/content/abstract/11/4/397

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Brian,
An elevated d-dimer can also be reflective of other medical conditions/illnesses. Thus, although it can suggest the possibility of an acute dissection, it is certainly not diagnostic of one and other tests (CT, TEE) would be necessary to confirm the diagnosis.

The most impt thing at this point in time for diagnosing a dissection is a high index of suspicion on the part of the ER doc.

Ed Chen

 

Hi,
--I agree.  A positive test can be positive for a number of other reasons, but if you have a positive d-dimer, a TEE or CT should be done to exclude dissection, along with a CT to exclude PE, and a Doppler venous ultrasound of the legs to exclude DVT.  
 
--The major impact of this test is to prevent people with subtle aortic dissection symptoms from being sent home from the ER as "OK".  Vague or no chest pain and a number of other subtle symptoms of aortic dissection can bring one to the ER, and without a family history or Marfans look or hypertension or other more classic clues, aortic dissection can be missed (historically up to 1/3 in the past).  The people with the classic severe "tearing" or "ripping pain" always get scanned.  It is the more vague presentations that tend to fall through the cracks.  Hence the need for an extremely high level of suspicion or paranoia by the ER doc that any seemingly innocent symptom might be a dissection (as a way catching some of that 1/3).   Routine d-dimer blood tests on all vague chest symptoms will help prevent that 1/3 from being sent home, without a lot of expensive testing on normal people due to that healthy high level of paranoia on the part of the ER doc.  Thus far all acute aortic dissections that have also had a d-dimer test done (in the literature) have had positive d-dimers.  No acute aortic dissections (in the literature) have thus far had negative d-dimers. 
 
--Chronic dissections seem to have lower and possible eventually normal d-dimer levels, and there was a Japanese article, saying that a d-dimer level may be useful in following Standford B (DeBakeyIII) dissections for possible signs of re-activation or progression despite medical therapy (another red flag for ordering a repeat CT to assess for interval change).  
 
--A negative test however does not mean that you won't get an acute aortic dissection tomorrow, it only means that you probably do not have one right now. 
 
Dean Easton MD, Radiologist

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D-dimer in acute aortic dissection.

Weber T, Hogler S, Auer J, Berent R, Lassnig E, Kvas E, Eber B.

Cardiology Department, General Hospital of the Barmherzigen Schwestern, Wels, Austria. webertom@aon.at

STUDY OBJECTIVE: Laboratory testing plays a minor role in the assessment of aortic dissection. Its main value is in the exclusion of other diseases. Following an incidental observation, we systematically investigated the relationship between elevated d-dimer levels and acute aortic dissection. DESIGN: We prospectively tested d-dimer levels in patients with suspected acute aortic dissection (10 patients). In addition, we investigated 14 patients who had received a confirmed diagnosis of thoracic aortic dissection during the previous 5 years, in whom d-dimer testing had been performed for differential diagnosis. Thirty-five patients with acute chest pain of other origin served as a control group. SETTING: Tertiary referral hospital. PATIENTS: Twelve patients had type A dissection (Stanford classification), and 12 patients had type B. MEASUREMENTS AND RESULTS: A d-dimer analysis was performed (Tina-quant assay; Roche Diagnostics; Mannheim, Germany) [normal limit of the assay, 0.5 micro g/mL]. The result of the d-dimer test was positive (ie, > 0.5 micro g/mL) in all patients (sensitivity of the test, 100%) with a mean value of 9.4 micro g/mL and a range of 0.63 to 54.7 micro g/mL. The degree of the elevation was correlated to the delay from the onset of symptoms to laboratory testing (mean, 12.6 h; range, 1 to 120 h) and showed a trend to the extent of the dissection, but not to the outcome (14 patients could be discharged; 10 patients died). CONCLUSIONS: Based on our observation, we suggest that testing for d-dimer should be part of the initial assessment of patients with chest pain, especially if aortic dissection is suspected. A negative test result makes the presence of the disease unlikely.

PMID: 12740250 [PubMed - indexed for MEDLINE]

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Hi Brian,
On researching aortic dissection, I did come across something that might be important.
There is a food that is associated with aortic dissection:  sweat peas
If rats are given a diet of 50% sweat peas, many will get aortic dissections. 
The cause has actually been well studied and is well known in poorer areas of the world where in times of drought, the peas are often the only thing left in the fields that are still green and edible. 
Grass peas (Lathyrus sativus even causes neurologic symptoms). 
Sweet peas (Lathyrus odoratus) contain a toxic nonprotein amino acid (beta amino-proprionitrile) that affects the cross-linking of the molecules of collagen, (making aortas and tendons weaker). 
So for what itís worth, it might be a good idea to stay away from sweat peas. 
Later,
Dean
 

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