d-dimer and aortic dissection

RAGING HYPOTHETICAL:

--your patient arrives complaining of severe chest pain radiating to the back
--you fear aortic dissection
--you've heard about this d-dimer thing...but is it ready for prime-time?




HIGH IN PE/DISSECTION, NOT SO MUCH IN MI: (PMID: 21478122)
--purpose of this research was to define the D-dimer value for discrimination between AAD, PE and AMI.
--consecutive series of 35 AAD, 22 PE and 206 AMI patients


--D-dimer values of patients with AAD (32.9 ± 66.7 g/ml, p<0.001) and PE (28.5 ± 23.6 g/ ml, p<0.001) were significantly higher than those of AMI patients (2.1 ± 3.7 g/ml).
--A cutoff value of 5.0 g/ ml was effective in distinguishing AAD and PE from AMI, with a sensitivity of 68% and a specificity of 90% (ok, but not great)




GOOD SENSITIVITY IS PROMISING... (PMID: 21296332)
--Review and meta-analysis to examine use of d-dimer as screening tool for aortic dissection.
--A value of 500 ng/ml was defined as the threshold for a positive plasma DD finding because it is widely used for ruling out pulmonary emboli.
--Identified 7 studies involving 298 subjects with aortic dissection and 436 without.


--When data were pooled across studies:

• sensitivity high (0.97, 95% confidence interval [CI] 0.94 to 0.99)
• negative predictive value high (0.96, 95% CI 0.93 to 0.98)
• specificity low (0.56, 95% CI 0.51 to 0.60)
• positive predictive value low (0.60, 95% CI 0.55 to 0.66) 

--In conclusion, our meta-analysis suggests that plasma DD <500 ng/ml is a useful screening tool to identify patients who do not have AAD.




NOT QUITE READY?  (PMID: 21546117)
--There is inadequate evidence to support the use of D-dimer to exclude acute aortic dissection.


--registry data reported by Suzuki et al provide the most valid estimates for D-dimer sensitivity and specificity; however, the relatively small sample size (N=220) resulted in imprecise estimates, with a lower limit of the 95% confidence interval (CI) of 0.90 for sensitivity and 0.38 for specificity.


--A conservative estimate based on these results indicates that the negative likelihood ratio for D-dimer is approximately 0.2 and the positive likelihood ratio is 1.5. If these approximations are validated in a larger prospective study, a positive D-dimer result would have no value in clinical decisionmaking, but a negative D-dimer result may decrease the probability of aortic dissection to a moderate degree.


--However, to rule out aortic dissection with a negative D-dimer result, the pretest probability would have to be very low. 


--Unfortunately, unlike pulmonary embolism or acute myocardial infarction, there are no validated clinical prediction rules to aid clinicians with establishing a pretest probability of aortic dissection.

BOTTOM LINE:

--studies used d-dimer cutoff of 500ng/ml

--high (but not perfect) sensitivity (90+%), low specificity

--potentially useful with patients with low pretest probability for aortic dissection

--since no validated prediction rules (like Wells/PERC for PE) for dissection, not quite ready for primetime

Submitted by J. Gullo.




Reference(s): PMID: 21478122; PMID: 21296332; PMID: 21546117; picture

where do patient’s with Marfan Syndrome dissect?

AORTIC DISSECTION & MARFAN SYNDROME:
--The major cardiovascular manifestation in Marfan Syndrome is a progressive dilatation of the ascending aorta, leading to aortic aneurysm formation and eventually to fatal aortic rupture or dissection. Aortic dissection in early adult life is the leading cause of death.

--The ascending and descending aorta are both abnormal in Marfan Syndrome.

· The descending aorta is affected in two out of three patients during aortic dissection, and is the site of most complications which occur during follow-up.

· Aortic dissection limited to the descending aorta can occur in patients without dilatation of the ascending aorta.

--Dissection of the descending aorta was associated with dissection of ascending aorta in 43% and was isolated in 20% of cases.

BOTTOM LINE:

--dissections in Marfan involve descending aorta ~2/3 of the time, but these frequently involve the ascending aorta also

--if you have a patient with Marfan, and are worried about a dissection...worry about both (ascending/descending)

Submitted by J. Gullo.

Reference(s): PMID: 20232788, medscape article, picture