An aortic aneurysm should be diagnosed before it ruptures; nearly all aneurysms can be treated surgically. An aneurysm found incidentally or through screening should be monitored until it reaches a size where the benefit of a surgical repair outweighs the operational risk.
The risk of rupture is small in aneurysms < 5 cm in diameter.
It is easy for a primary care physician to learn the diagnosis of an abdominal aortic aneurysm with ultrasonography.
The possibility of aortic dissection must be considered in a patient with severe pain suggestive of acute myocardial infarction but without clear ECG changes.
A patient with a ruptured aneurysm or aortic dissection needs immediate hospitalization.
Aortic aneurysms
Thoracic aortic aneurysm (TAA)
Incidence
The incidence of TAA is 5.9/100 000/year; the prevalence is growing due to the increased use of imaging studies.
Men are affected 2-4 times more frequently than women.
Risk factors
Smoking
Hypertension
Atherosclerosis
Genetic connective tissue diseases, such as Marfan syndrome, Loeys-Dietz syndrome (LDS) and Ehlers-Danlos syndrome (EDS)
Mycotic aneurysms (for example syphilitic) are very rare these days.
Bicuspid or unicuspid aortic valve (bicuspid aortopathy)
Signs and symptoms
Usually asymptomatic before rupture
Some patients have vague chest discomfort or pain.
Hoarseness of voice in some cases, which signifies aneurysm-induced strain to the recurrent laryngeal nerve.
Physical examination usually reveals no significant findings.
The patient's vascular status must be carefully assessed for the possible presence of an abdominal aortic aneurysm, peripheral arterial disease or distal embolization.
Auscultation may reveal a diastolic murmur of aortic regurgitation if a TAA of the ascending aorta is causing secondary aortic insufficiency.
Imaging studies
An incidental finding in a chest x-ray: mediastinal widening in an AP projection. A distended silhouette of the descending aorta is occasionally visible in a lateral projection.
CT or MRI scanning is used to confirm diagnosis.
In aneurysms of the ascending aorta, echocardiography may be used to assess the morphology and functional status of the aortic valve and root.
Indications for elective surgery
Ascending aorta
A degenerative aneurysm ≥ 5.5 cm in diameter
In bicuspid aortopathy 5.0-5.5 cm, depending on the morphology as well as on patient's age and risk factors
In Marfan syndrome, when the aneurysm is ≥ 5.0 cm in diameter
Surgery is considered in aneurysms smaller than this if the family history is heavy.
In other connective tissue disorders (e.g. LDS, EDS) the criterion is 4.0-5.0 cm; there are no clear guidelines.
A growth rate of ≥0.5 cm/year when the diameter approaches other criteria.
With other concomitant heart surgery when the diameter of the ascending aorta is ≥4.5 cm
Aortic arch and descending aorta
Degenerative aneurysm ≥5.5-6.0 cm in diameter
After dissection and in genetic connective tissue disease when the aneurysm is ≥ 5.5 cm in diameter
Surgery
Ascending aorta
Surgery through a sternotomy
Involves the use of the standard open heart surgery procedure where the heart is temporarily stopped.
The dilated part of the ascending aorta and/or the aortic root is replaced with a Dacron vascular prosthesis.
In an aortic root repair, the native valve can be spared in selected cases and reimplanted into the dacron graft. Otherwise, the valve is replaced with a mechanical or biological valve prosthesis.
Aortic arch
Open heart surgery as a rule requiring temporary cessation of circulation.
Deep hypothermic circulatory arrest (DHCA) is used to provide brain protection; the body temperature is lowered usually to below 20°C with the aid of a heart-lung machine.
Various additional temporary cerebral perfusion techniques may be used during the circulatory arrest, particularly if the repair is anticipated to last longer than 30 minutes.
Endovascular repair of pathological changes in the first section of the descending aorta is possible in association with open aortic arch repair by using the so-called hybrid prostheses (“Frozen Elephant Trunk”, FET).
Today, so-called hybrid aortic arch surgery is becoming more common. It entails the reconnection of blood vessels branching off from the aortic arch to the ascending aorta using a separate branch prosthesis. This takes place during open heart surgery and is followed by endovascular stent graft therapy of the aortic arch pathology.
Descending aorta and thoracoabdominal aorta
The aorta is accessed via a left thoracotomy. The incision may be extended if necessary to the left retroperitoneal space.
The risk of ischaemic damage to the spinal cord and visceral organs poses a particular problem.
The risk of paraplegia is 5-15% with modern surgical techniques; the more extensive the reconstruction the higher the risk.
Stent graft therapy, i.e.endovascular placement of a stent graft is nowadays the primary treatment. Stent graft therapy is for the time being not recommended for persons with Marfan syndrome or other connective tissue disorders.
If the procedure is technically feasible, a stent graft is particularly suitable for patients in poor health and elderly patients whose surgical risk during open heart surgery is considered to be excessively high.
Abdominar aorta is regarded as aneurysmatic when its diameter is > 3.0 cm.
An aorta with a diameter between 2.5 and 3.0 cm is regarded as enlarged. Of these, 30% will grow within 5 years and fulfill the criteria of an aneurysm.
According to meta-analyses, the prevalence of abdominal aortic aneurysm (AAA) with a diameter of > 3 cm in men aged 65 years is 4.9%.
In women aged 65-80 years, the prevalence of AAAs with a diameter of > 3 cm is only 0.6-1.5%.
According to newer studies, the prevalence of AAA has clearly decreased: e.g. in Sweden, screening showed the prevalence of AAA (diameter > 3 cm) to be 1.7% in men.
The cause of an AAA is almost always atherosclerosis.
Prevalence is higher in persons who have occlusive arterial disease in the lower extermity or hypertonia, who smoke, or who have a sibling with an AAA.
Signs and symptoms
An unruptured aneurysm is usually asymptomatic.
Pain is generally a sign of rupture or quick expansion of the aneurysm. Sudden abdominal pain that radiates to the back is a typical sign of a rupture. Pain sometimes radiates to the flank, groin, testicles or upper thighs. Fainting may also be an early symptom.
A pulsating mass may be palpated on the upper or mid-abdomen. An AAA is often an incidental finding.
Abdominal x-rays may show the outline of a calcified AAA (plain x-rays or urography).
AAAs are easily detected with ultrasonography. However, ultrasonography cannot be used for diagnostic purposes if the aneurysm has ruptured. If the patient's condition allows, CT scanning is used to confirm rupture.
Effective management of hypertension and other atherosclerotic risk factors
An AAA less than 4.5 cm in diameter may be monitored in primary care.
After an AAA (diameter > 3 cm) has been diagnosed, the first follow-up ultrasonography should be carried out after 3-6 months.
During follow-up, ultrasonography is indicated
after 5 years for aneurysms of 2.5-2.9 cm in diameter
every 3 years for aneurysms of 3.0-3.5 cm in diameter
every 2 years for aneurysms of 3.6-4 cm in diameter
every 3-12 months for aneurysms of 4.1-4.4 cm in diameter.
If no growth is observed, less frequent follow-up visits are possible or they may sometimes, albeit rarely, even be totally stopped.
A patient with an aneurysm of more than 4.5 cm in diameter, or whose aneurysm has grown more than 10 mm in a year should be referred to a vascular surgery unit. Surgery is indicated when the diameter of an AAA exceeds 5.2 cm in women and 5.5 cm in men. Aneurysms that cause pain or embolisation are operated on regardless of their size. Moreover, 4.5-5.4 cm aneurysms with an annual growth rate of over 1 cm must also be managed surgically.
The annual risk of rupture is only 1.1% in aneurysms with a diameter of 4.0-4.9 cm, 3.3% when the diameter is 5.0-5.9 cm, 9.4% when the diameter is 6.0-6.9 cm, and 24.5% when the diameter is 7.0-7.9 cm.
The surgical options include conventional open surgery where the distended portion is replaced with a vascular prosthesis and, nowadays increasingly, the repair of the distension with an endovascular stent graft.
In studies, screening for an AAA has been observed to significantly reduce AAA mortality in men, but there is no evidence to demonstrate significant reduction in women.
At present, there is suggestive evidence that men aged 65 years should be screened once. As for the rest of the population, screening should target risk groups including patients with atherosclerotic disease of the lower limbs or carotid arteries, hypertension, smokers and those with a family history of an aneurysm.
Aortic dissection
Dissection is defined as a tear in the innermost layer (tunica intima) of a blood vessel, which results in blood entering the middle layer (tunica media) and creating a false lumen of varying length in between the layers. The false lumen may thrombose (intramural haematoma, IMH) or it may form a permanent lumen with a continuous flow within (classic dissection).
As the dissection extends it may damage the aortic valve or prevent circulation to the aortic branch vessels. In such a case, the patient may suffer major ischaemic target organ complications involving the heart, brain, spinal cord, visceral organs or lower limbs.
The incidence is 2-3/100 000/year.
The Stanford classification system is the most used clinical classification system.
Type A originates in the (intrapericardial) ascending aorta and may propagate to the aortic arch and beyond it to involve the descending aorta.
Early mortality is high, usually attributable to cardiac tamponade, interrupted flow to the coronary arteries or sudden severe aortic valve incompetence.
Type B originates from the descending aorta but may retrograde into the aortic arch.
The early mortality rate is about 10-20%, and death is generally due to malperfusion of visceral organs or lower limbs, but aortic rupture is rarer.
Symptoms
Sudden onset of chest and back pain; the location of the pain may change as the dissection advances.
Malperfusion of the aortic branch vessels may cause highly variable symptoms depending on the target organ affected.
Clinical findings
In general, the patient looks critically ill.
In Type A dissection, the clinical picture may resemble that of cardiogenic shock
Blood pressure is either low (Type A) or high (Type B)
Pulse deficits are typical
A murmur indicative of aortic regurgitation
Chest x-ray
widened mediastinum
pleural effusion
ECG may show signs of ischaemia (not to be treated with thrombolysis!)
Diagnosis
If the patient is haemodynamically stable, the first choice imaging study is a contrast-enhanced CT scan of the aorta.
If the patient is in unstable condition, transoesophageal echocardiography carried out in the operating theatre is recommended.
Surgical intervention is always necessary; the ascending aorta is reconstructed with a vascular graft.
If the primary dissection extends to beyond the aortic arch or the arch is aneurysmal, the arch must be repaired.
Aortic root repair is warranted if it is dilated or the aortic valve is incompetent.
Coronary artery bypass surgery if coronary circulation is impaired
Type B
Uncomplicated cases are treated conservatively. The principal treatment approach consists of aggressive blood pressure control at the early stages, usually with an infusion of nitroprusside and/or a beta blocker and takes place at a monitoring ward. Follow-up CT imaging is performed after a few days and after 1-2 weeks.
Surgery, which primarily means placement of a stent graft to cover the primary tear, is considered if
malperfusion or rupture (immediately)
the aorta is severely dilated and there is a risk of rupture (urgently)
hypertension or pain cannot be controlled with medication (urgently).
Monitoring
Some patients with type A dissection that has been treated surgically or type B dissection that has been treated conservatively will develop aortic dilatation requiring interventional treatment within 5 years. Consequently, monitoring is important.
After hospitalisation, a follow-up CT or MRI scan of the aorta 3, 6 and 12 months after the dissection and then annually for at least 5 years.
References
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