Aortic aneurysm
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| Aortic aneurysm Classification and external resources | |
| ICD-10 | I71. |
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| ICD-9 | 441 |
| OMIM | 100070 |
| DiseasesDB | 792 823 805 |
| eMedicine | emerg/942 med/2783 emerg/27 radio/1 med/3443 |
| MeSH | D001014 |
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An aortic aneurysm is a general term for any swelling (dilatation or aneurysm) of the aorta, usually representing an underlying weakness in the wall of the aorta at that location. While the stretched vessel may occasionally cause discomfort, a greater concern is the risk of rupture which causes severe pain, massive internal hemorrhage and, without prompt treatment, results in a quick death. Aneurysms often are a source of blood clots (emboli) stemming from the most common etiology of atherosclerosis.
Pathology
The physical change in the aortic diameter can occur secondary to an intrinsic defect in the protein construction of the aortic wall, trauma, infection, or due to progressive destruction of aortic proteins by enzymes.
Signs, symptoms and diagnosis
Most intact aortic aneurysms do not produce symptoms. As they enlarge, symptoms such as abdominal pain and back pain may develop. Compression of nerve roots may cause leg pain or numbness. Untreated, aneurysms tend to become progressively larger, although the rate of enlargement is unpredictable for any individual. Rarely, clotted blood which lines most aortic aneurysms can break off and result in an embolus. They may be found on physical examination. Medical imaging is necessary to confirm the diagnosis.
Thoracic Aortic Aneurysm
- Thoracic aortic aneurysm represents aneurysmal dilatation of ascending, arch, or descending thoracic aorta.
- Aneurysm is defined as a localized or diffuse dilatation of more than 50% normal diameter of the aorta.
- Atherosclerosis or connective tissue disorders may be contributing underlying disorders that facilitate aortic dilatation.
- Frequently associated factors include:
- Advanced age
- Hypertension
- Smoking
- Atherosclerosis
- Aortic dissection
- Cystic medial necrosis (Marfan syndrome, Ehlers-Danlos syndrome)
- Syphilis
- Thoracic aneurysms are classified by the portion of aorta involved: the ascending thoracic aorta, the arch, or the descending thoracic aorta. This anatomic distinction is important because the etiology, natural history, and treatment of thoracic aneurysms vary for each of these segments.
- Aneurysms of the descending aorta are most common, followed by aneurysms of the ascending aorta, whereas arch aneurysms occur less often.
- Descending aortic thoracic aneurysms may extend distally to involve the abdominal aorta and create a thoracoabdominal aortic aneurysm.
- Thoracic aortic aneurysms are less common than abdominal aortic aneurysms.
- Complications:
- Aortic rupture
- Aortic dissection
Examples
Images shown below are courtesy of RadsWiki and copylefted
 Thoracic Aortic Aneurysm |
 Thoracic Aortic Aneurysm |
Abdominal Aortic Aneurysm
Aortic aneurysms, hereafter referred to as AAAs, are more common in the abdominal aorta. One reason for this is that elastin, the principal load bearing protein present in the wall of the aorta, is reduced in the abdominal aorta as compared to the thoracic aorta (nearer the heart). Another is that the abdominal aorta does not possess vasa vasorum, hindering repair. Most are true aneurysms that involve all three layers (tunica intima, tunica media and tunica adventitia), and are generally asymptomatic before rupture.
The prevalence of AAAs increases with age, with an average age of 65-70 at the time of diagnosis. AAAs have been attributed to atherosclerosis, though other factors are involved in their formation.
An AAA may remain asymptomatic indefinitely. There is a large risk of rupture once the size has reached 5 cm, though some AAAs may swell to over 15 cm in diameter before rupturing. Before rupture, an AAA may present as a large, pulsatile mass above the umbilicus. A bruit may be heard from the turbulent flow in a severe atherosclerotic aneurysm or if thombosis occurs. Unfortunately, however, rupture is usually the first hint of AAA. Once an aneurysm has ruptured, it presents with a classic pain-hypotension-mass triad. The pain is classically reported in the abdomen, back or flank. It is usually acute, severe and constant, and may radiate through the abdomen to the back.
The diagnosis of an abdominal aortic aneurysm can be confirmed at the bedside by the use of ultrasound. Rupture could be indicated by the presence of free fluid in potential abdominal spaces, such as Morrison's pouch, the splenorenal space, subdiaphragmatic spaces and peri-vesical spaces. A contrast-enhanced abdominal CT scan is needed for confirmation.
Only 10-25% of patients survive rupture due to large pre and post-operative mortality. Annual mortality from ruptured abdominal aneurysms in the United States alone is about 15 000. Another important complication of AAA is formation of a thrombus in the aneurysm.
Examples
Images shown below are courtesy of RadsWiki and copylefted
 CT: a large abdominal aortic aneurysm |
 CT: a large abdominal aortic aneurysm |
 CT: a large abdominal aortic aneurysm |
 CT: a large abdominal aortic aneurysm |
 CT: a large abdominal aortic aneurysm |
 CT: a large abdominal aortic aneurysm |
 CT: a large abdominal aortic aneurysm |
 Ruptured abdominal aortic aneurysm |
 Ruptured abdominal aortic aneurysm |
 Ruptured abdominal aortic aneurysm |
Screening
Medical Treatment
Medical therapy of aortic aneurysms involves strict blood pressure control. This does not treat the aortic aneurysm per se, but control of hypertension within tight blood pressure parameters may decrease the rate of expansion of the aneurysm.
Surgical Treatment
The definitive treatment for an aortic aneurysm is surgical repair of the aorta. This typically involves opening up of the dilated portion of the aorta and insertion of a synthetic (Dacron or Gore-tex) patch tube. Once the tube is sewn into the proximal and distal portions of the aorta, the aneurysmal sac is closed around the artificial tube. Instead of sewing, the tube ends, made rigid and expandable by nitinol wireframe, can be much more simply and quickly inserted into the vascular stumps and there permanently fixed by external ligature[4]
The determination of when surgery should be performed is complex and case-specific. The overriding consideration is when the risk of rupture exceeds the risk of surgery. The diameter of the aneurysm, its rate of growth, the presence or absence of Marfan Syndrome or similar connective tissue disorders, and other coexisting medical conditions are all important factors in the determination.
A rapidly expanding aneurysm should be operated on as soon as feasible, since it has a greater chance of rupture. Slowly expanding aortic aneurysms may be followed by routine diagnostic testing (i.e.: CT scan or ultrasound imaging). If the aortic aneurysm grows at a rate of more than 1 cm/year, surgical treatment should be electively performed.
The current treatment guidelines for abdominal aortic aneurysms suggest elective surgical repair when the diameter of the aneurysm is greater than 5 cm. However, recent data suggests medical management for abdominal aneurysms with a diameter of less than 5.5 cm.[1]
Endovascular treatment of AAA
In the recent years, the endoluminal treatment of Abdominal Aortic Aneurysms has emerged as a minimally invasive alternative to open surgery repair. The first endoluminal exclusion of an aneurysm took place in Argentina by Dr. Parodi and his colleagues in 1991. The endovascular treatment of aortic aneurysms involves the placement of an endo-vascular stent via a percutaneous technique (usually through the femoral arteries) into the diseased portion of the aorta. This technique has been reported to have a lower mortality rate compared to open surgical repair, and is now being widely used in individuals with co-morbid conditions that make them high risk patients for open surgery. Some centers also report very promising results for the specific method in patients that do not constitute a high surgical risk group.
There have also been many reports concerning the endovascular treatment of ruptured Abdominal Aortic Aneurysms, which are usually treated with an open surgery repair due to the patient's impaired overall condition. Mid-term results have been quite promising. However, according to the latest studies, the EVAR procedure doesn't carry any overall survival benefit. [1]
Endovascular treatment of other aortic aneurysms
The endoluminal exclusion of aortic aneurysms has seen a real revolution in the very recent years. It is now possible to treat thoracic aortic aneurysms, abdominal aortic aneurysms (please see above) and other aneurysms in most of the body's major arteries (such as the iliac and the femoral arteries) using endovascular stents and avoiding big incisions. Still, in most cases the technique is applied in patients at high risk for surgery as more trials are required in order to fully accept this method as the gold standard for the treatment of aneurysms.[1]
Complications of Endovascular Treatment
Endoleak
- Endoleak is a complication of endovascular aneurysm repair.
- The endoleaks may continue to perfuse and pressurize the aneurysm sac, thereby conferring an ongoing risk of aneursym enlargement and/or rupture.
- Endoleaks are classified by the source of blood flow, and organized into five categories.[1] [1]
- I: Attachment site leaks
- II: Collateral vessel leaks
- III: Graft failure (i.e. midgraft hole, junctional leak or disconnect)
- IV: Graft wall porosity
- V: Endotension (with or without endoleak)
Images shown below are courtesy of RadsWiki and copylefted
 Endoleak after Abdominal aortic aneurysm repair |
 Endoleak after Abdominal aortic aneurysm repair |
 Endoleak after Abdominal aortic aneurysm repair |
 Endoleak after Abdominal aortic aneurysm repair |
 Endoleak after Abdominal aortic aneurysm repair |
Prevention
Attention to patient's general blood pressure, smoking and cholesterol risks helps reduce the risk on an individual basis. There have been proposals to introduce ultrasound scans as a screening tool for those most at risk: men over the age of 65.[1] [1]. The tetracycline antibiotic Doxycycline is currently being investigated for use as a potential drug in the prevention of aortic aneurysm due to its metalloproteinase inhibitor and collagen stabilizing properties.
Research
Stanford University is conducting research to gather information on AAA risk factors, and to evaluate the effectiveness of an exercise program at preventing the growth of small AAAs in older individuals. [5]
See Also
Videos on Abdominal Aortic Aneurysm
References
External links
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
