Aortic aneurysm and dissection.

Code

Quality of Evidence

Definition

High

Further research is very unlikely to change our confidence in the estimate of effect.

Several high-quality studies with consistent results
In special cases: one large, high-quality multi-centre trial

Moderate

Further research is likely to have an important impact on confidence in the estimate of effect and may change the estimate.

One high-quality study
Several studies with some limitations

Low

Further research is very likely to have an important impact on confidence in the estimate of effect and is likely to change the estimate.

One or more studies with severe limitations

Very Low

Any estimate of effect is very uncertain.

Expert opinion
No direct research evidence
One or more studies with very severe limitations

The levels of evidence [A-D] supporting the recommendations are defined at the end of the "Major Recommendations" field.

Basic Rules

Diagnose aortic aneurysm before rupture: nearly all aneurysms can be treated surgically. Monitor a small aneurysm, found incidentally or through screening, until it reaches a size where the benefit of surgical repair outweighs the risks associated with such surgery.
It is easy for a general practitioner to learn the diagnosis of abdominal aortic aneurysm with ultrasonography.
Remember the possibility of aortic dissection in a patient with severe pain suggestive of acute myocardial infarction (AMI) but without clear electrocardiogram (ECG) findings.
Patients with aortic dissection must be referred to a hospital immediately.

Aortic Aneurysms

Abdominal Aortic Aneurysm

Atherosclerosis is the most important causative factor.
85% of the patients are men. An aneurysm is found in 10% of men aged 75 years or more.
A palpable, pulsating mass in the upper or middle abdominal region is a typical finding. Most aneurysms are found accidentally.
The patient may complain of pain which may resemble pain originating from the ureter or spinal cord. The pain often radiates to the back. Pain indicates an expanding aneurysm that needs surgery.
Sometimes a calcified aneurysm can be recognised on plain abdominal x-rays or urography films.
The diagnosis is confirmed by ultrasonography (which can be performed by a general practitioner familiar with the examination).
Treatment
- Hypertension and other cardiovascular risk factors should be treated effectively.
- An aneurysm with a diameter of over 3 cm is monitored with ultrasonography every 12 months. When the diameter of the aneurysm has reached 5 cm in a man or 4.5 cm in a woman the ultrasonographic checks are carried out every 6 months (Powell & Greenhalgh, 2003).
- Surgery is indicated when the diameter of the aneurysm exceeds 5.5 cm (The UK Small Aneurysm Trial Participants, 1998; Ballard, Fowkes, & Powell, 1999; Lederle et al., 2007) [B].
  - About 1% of aneurysms with diameter of 4 cm rupture annually compared with 10% of aneurysms with a diameter of 6 cm or more. The mortality from a ruptured aneurysm is 90%.
  - The operation may be performed by conventional open surgery with implantation of a vascular prosthetic graft, or by endovascular stenting.
- Aneurysms extending into the chest cavity should be operated on.
Screening for abdominal aortic aneurysms is worthwhile, at least if certain criteria related to age and risk are applied (Kent et al., 2004): these include age over 65 years, male sex, smoking and family history of the disease. Elderly brothers of patients with known aneurysms should be screened with ultrasonography (Salo et al., 1999) [C].
Recommendations for even more active screening have been published because screening has been proven to decrease mortality (Cosford & Leng, 2007; Fleming et al., 2005; Earnshaw et al., 2004; Kent et al., 2004; Ashton et al., 2002; Takagi et al., 2007) [A]. A prerequisite for the decrease is low operative mortality (Greenhalgh & Powell, 2007).

Aneurysm of the Thoracic Aorta

Usually asymptomatic. Pain suggests expansion.
Aortic regurgitation (with symptoms related to it) (See the Finnish Medical Society Duodecim guideline "The Most Common Acquired Adult Valvular Heart Diseases and Associated Murmurs.")
Tracheal or bronchial compression or phrenic nerve paralysis.
Sometimes the neck veins are dilated due to the compression caused by the aneurysm.
May be visible as an incidental finding on a chest x-ray.
Treatment is either surgical or conservative.

Aortic Dissection

The typical locations are the ascending (type I and II) and descending thoracic aorta (type III). Type I is confined to the ascending aorta. Dissections of the other types may extend into the abdominal aorta.
As the tunica interna ruptures, the blood rushes into the layers of the tunica media. The aorta is often (but not always) dilated and may be visible on a chest x-ray.
Marfan's syndrome is often associated with dissection or annuloaortic ectasia and aortic regurgitation.
The incidence of aortic dissection is about 10/million inhabitants/year.

Symptoms

Suspect aortic dissection in a patient with sudden excruciating pain without ECG findings suggestive of AMI.
The patient is usually a hypertensive male.
The location of the pain may change as the dissection advances.
The pain radiates in the same way as pain associated with AMI, including the jaw and sometimes the palate. Pain is often also felt in the back.
The associated symptoms include those resulting from the occlusion of aortic branches, i.e., ischaemic symptoms of the brain, heart, kidneys, and intestines.
Acute aortic regurgitation may occur (a new murmur).

Findings

Even though pulse asymmetry is presented only in a minority of patients it is worth checking for. A murmur from aortic regurgitation or bruits may be heard.
Blood pressure is high, particularly in distal dissection.
ECG will not be indicative of AMI but may show left ventricular hypertrophy, an old infarction, or ischaemia (AMI is sometimes possible when the dissection occludes a coronary artery).
A chest x-ray may show a dilated aortic arch, but often the x-ray is nearly normal.
Transoesophageal echocardiography is a good primary investigation. Computed tomography, magnetic resonance imaging (MRI), or angiography is often needed for final diagnosis.

Treatment

The systolic blood pressure should be lowered quickly to around 100-120 mmHg. First aid treatment includes nifedipine 10 mg chewed, nitrate (or nitroprusside) infusion, a beta-blocker, and effective analgesia.
Dissection of the ascending aorta should be operated on immediately. Prognosis without surgery is very poor.
The immediate treatment of a dissection of the descending aorta is conservative (i.e., reduction of blood pressure and heart rate).
Thrombolysis is contraindicated.

Related Resources

Refer to the original guideline document for related evidence, including Cochrane reviews and other evidence summaries.

Definitions:

Classification of the Quality of Evidence

Code	Quality of Evidence	Definition
A	High	Further research is very unlikely to change our confidence in the estimate of effect. Several high-quality studies with consistent results In special cases: one large, high-quality multi-centre trial
B	Moderate	Further research is likely to have an important impact on confidence in the estimate of effect and may change the estimate. One high-quality study Several studies with some limitations
C	Low	Further research is very likely to have an important impact on confidence in the estimate of effect and is likely to change the estimate. One or more studies with severe limitations
D	Very Low	Any estimate of effect is very uncertain. Expert opinion No direct research evidence One or more studies with very severe limitations

GRADE (Grading of Recommendations Assessment, Development and Evaluation) Working Group 2007 (modified by the EBM Guidelines Editorial Team).

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