Aortic Dissection

Chapter 30 Aortic Dissection








4 What is the epidemiology of dissection, including mortality?


Aortic dissection is a relatively rare but a highly lethal disease. The estimated incidence is 5 to 30 cases per million people per year. Population-based studies suggest that the incidence of acute dissection ranges from 2 to 3.5 cases per 100,000 person-years, which correlates with 6000 to 10,000 cases annually in the United States. It may be that two to three times as many patients die of dissections as of ruptured aortic aneurysms; approximately 75% of patients with ruptured aortic aneurysm will reach an emergency department alive, whereas for aortic dissection 40% die immediately. Furthermore, only 50% to 70% will be alive 5 years after surgery depending on age and underlying cause.


For untreated acute dissection of the ascending aorta the mortality rate is 1% to 2% per hour after onset. For type A dissections treated medically it is approximately 20% within the first 24 hours and 50% by 1 month after presentation. Even with surgical intervention, the mortality rate for type A dissection may be as high as 10% after 24 hours and nearly 20% 1 month after repair.


Although type B dissection is less dangerous than type A, it is still associated with an extremely high mortality. The 30-day mortality rate for an uncomplicated type B dissection approaches 10%. However, patients with type B dissection who have complications such as limb ischemia, renal failure, or visceral ischemia have a 2-day mortality upwards of 20% and may prompt the need for surgical intervention.



5 What are the risk factors and associated conditions for dissection?


The prevalence of aortic dissection appears to be increasing, independent of the aging population, as noted by Olsson and colleagues, who found that the incidence of dissection among Swedish men has increased to 16 per 100,000 yearly. Risk factors include the following:



image Hypertension: Present in 70% to 90% of patients with acute dissection.


image Advanced age: Mean of 63 years in the International Registry of Acute Aortic Dissection (IRAD).


image Male sex: Represented by 65% of patients in the IRAD.


image Family history: Recently recognized is a genetic, nonsyndromic familial form of thoracic aortic dissection. Studies of patients referred for repair of thoracic aortic dissections and aneurysms who did not have a known genetic mutation have indicated that between 11% and 19% of these patients have a first-degree relative with thoracic aortic disease.


image Trauma (deceleration/torsional injury)


image Congenital and inflammatory disorders: present as Marfan syndrome in almost 5% of total patients in the IRAD and half of those patients under age 40 years. Other associated congenital disorders include Ehlers-Danlos syndrome, Loeys-Dietz syndrome, bicuspid aortic valve, aortic coarctation, Turner syndrome, Takayasu and giant-cell aortitis, relapsing polychondritis (Behçet disease, spondyloarthropathies), or confirmed genetic mutations known to predispose to dissections (TGFBR1, TGFBR2, FBN1, ACTA2, or MYH11).


image Pregnancy: Associated with 50% of dissections in women under age 40 and most frequently occurring in the third trimester. This might be attributable to elevations in cardiac output during pregnancy that cause increased wall stress.


image Circadian and seasonal variations: Producing a higher frequency of dissection in the morning hours and in the winter months.


image Iatrogenic: Occurring as a consequence of invasive procedures or surgery, especially when the aorta has been entered or its main branches have been cannulated, such as for cardiopulmonary bypass.




7 Describe the common clinical findings associated with aortic dissection


A systems-based approach can be used to describe the wide range of clinical findings that can be associated with aortic dissection.


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Jul 7, 2016 | Posted by in CRITICAL CARE | Comments Off on Aortic Dissection

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