Aortic dissection versus Aortic aneurysm

[flowerlady]

What is the difference between aortic dissection and aortic aneurysm, I ve always thought they are the same?

[Dr.NickRiviera]

aortic dissection is an intimal tear which creates another pathway within which the blood runs, like a false lumen between the layers of the aorta wall.

aortic aneurysm is a weakening of the wall and then an outpuching of the aorta wall.

[Dr. Mexito]

Originally Posted by khushi.chahal

aortic aneurysm is a weakening of the wall and then an outpuching of the aorta wall.

Also, is important to mention that in aortic aneurysm (AA), the 3 layers of the aorta are involved in the dilation, AA is more prone to be in the abdominal aorta and the mortality rate is not as high as in aortic dissection.

On the other hand, in aortic dissection (AD) the dilation involve just 2 layers of the aortic wall: the elastic layer and adventitia layer. The mortality is higher than that of aortic aneurism (A great number of patients with AD die because of being misdiagnosed with cardiac infarct), AD is more common in the ascending aorta, and AA can be a cause of AD.

Another big difference is that while patients with an AA in the abdominal aorta are treated with surgery, patients with an AD in abdominal aorta are treated just with medication and observation (most of the time) due to a high post OP mortality (bad outcome).

Last thing: since we are talking about dissection, I want to correct something that I heard in Goljan audio. Rx is not the way to Dx AD (It just gives a presumptive diagnosis), the gold standard is CT. MIR has almost 100% in both sensitivity and specificity but is to troublesome (not good in the emergency setting), TEE is also be used instead of CT, but has the problem of being too uncomfortable for the patient. The rest of the Dx tools are just to help, never to Dx because some times AD can present with a normal Rx and normal ECG, even low levels of D-dimer.

[doctorFH]

@ Dr. Mexito:

Every thing is right except that AD is not treated surgically. Acute aortic dissection can be treated surgically or medically. In surgical treatment, the area of the aorta with the intimal tear is usually resected and replaced with a Dacron graft. I remember an RTA patient who fell from motorbike, i saw during my Orthopedics rotation who got both lower limbs (b/L Tibia and 1 acetabulum) badly fractured, C7 vertebra fractured and at the same time got aortic dissection, our cardio-thoracic surgeon repaired her aortic dissection, the neurosurgeon did ACDF or pedicel screws i dont remember well and orthopedics ppl did bilateral illizarov and by the grace of God patient did well and recovered over time....

[Dr. Mexito]

Originally Posted by doctorFH

@ Dr. Mexito:

Every thing is right except that AD is not treated surgically.

A post traumatic AD has a totally different etiology than that of an AD due to cystic necrosis or an intimal tear secondary to collagen deterioration of the matrix. Plus, most of the post traumatic AD are in the descending aorta, just below the left subcalvian artery and most of the time, the tear can have a retrograde extension. In this case, surgery is the indication.

I will be more clear with my explanation:

In the Stanford type A aortic dissection (those involving the ascending aorta until the origin of the left subclavian artery) surgery is the treatment because this patients have a high risk of developing a cardiac tamponade due to retrograde dissection of the intimal tear. This is true if the AD has a complete false lumen, as it will occur in the case of a post traumatic AD (Like the one that you mentioned). Some of the few contraindications for surgery in patients with a Stanford non traumatic type A AD include: patient does not want surgery intervention, patient is in coma when arriving to the ER, or a really old patient (to mention some). Also, if the aortic dissection presents with an intramural hematoma of the false lumen or with a complete thrombosed false lumen (which are almost the same thing), there is no indication for surgical intervention. All this is true if the aortic dissection is a Stanford type A aortic dissection. Indications to operate a Stanford type A AD with a thrombosed false lumen are: sudden on sent of pain (means tear is extending), patient is hemodynamically unstable, the diameter of the aorta is increasing during CT follow up, or sudden lack of pulses in the extremities (To mention some).

Now, if the AD is in the abdominal aorta, this means that the dissection is an Stanford type B aortic dissection. Stanford type B AD are all of the dissections that involve the aorta distal form the left subclavian artery origin. In the case of a type B AD, surgery is not an indication unless the patient is hemodynamically unstable or for example: pulses are absent in the lower limbs, there is a suspicion of renal failure (to mention some). Here, in the case of a type B AD (Non post traumatic dissection), is does not matters if the false lumen is a complete false lumen or if it is thrombosed false lumen, the initial treatment is observational (According to IRAD, there is a high mortality if patients undergo surgery). However, if the patients is not doing well or if the dissection is expanding to fast, then you operate because the dissection can rupture.

OK, to finishing with this... One cannot say that all of the AD are to be treated surgically, or that all of the AD have to treated with a conservatory fashion. The therapeutic decision is based on the patient clinical presentation and in the classification of the AD (Stanford, DeBakey, proximal/distal). So, like I said before: most of the AD that happen in the abdominal aorta are not to be operated, while almost all of the abdominal aortic aneurysm are to be operated.

I hope that this can help to clarify some questions and doubts... I'll be more than happy to further discus this topic.

[doctorFH]

Originally Posted by Dr. Mexito

A post traumatic AD has .......... I'll be more than happy to further discus this topic.

Thanks for a great explanation!!!!