Aortic aneurysm, peripheral arterial aneurysm
Introduction – definition
An aneurysm is a circumscribed vascular dilation where the maximum diameter exceeds 150% of the healthy blood vessel. Aneurysmatic vascular dilations usually occur in arteries. Arterial vascular dilations most commonly develop in the aorta. Aortic aneurysms constitute around 80% of all aneurysms.
Epidemiology
Abdominal aortic aneurysm (AAA) affects 1-5% of the population, and incidence increases with age. The group most at risk includes male smokers over the age of 65.
The aneurysm of peripheral blood vessels is overall rare, somewhat more commonly diagnosed in the popliteal artery and the arteries of the brain stem
Etiology – risk factors
The main risk factors of aneurysm are atherosclerosis and smoking, age, male gender, less often genetic predisposition, genetic disorders, infection, inflammation, and iatrogenic causes.
Abdominal aortic aneurysm (AAA)
Infrarenal abdominal aortic aneurysm is the most common form of arterial dilation. If the diameter of the aorta is > 3 cm, it is considered aneurysmal. The majority of abdominal aortic aneurysms remain asymptomatic and diagnosis is based on incidental findings (abdominal ultrasound). In the case of symptomatic abdominal aortic aneurysm, pain usually manifests spontaneously or at palpation. The most severe complication is rupture of the aneurysm, which has a 50% perioperative mortality.
In terms of morphology, abdominal aortic aneurysms may be fusiform (symmetric, spindle-shaped) and saccular (asymmetric) . In terms of location, aneurysms may be suprarenal, pararenal, juxtarenal, and infrarenal .
The devices used to diagnose abdominal aortic aneurysms are primarily ultrasound, CT angiography is crucial in measuring the length and diameter of the aneurysm, as well as for treatment planning and assessing the risk or any sign of rupture.
Fusiform infrarenal aortic aneurysm with a maximum diameter of over 5.5 cm is an indication for elective surgery. Surgery may be also be necessary if the aneurysm grows more than 1 cm/year, as well as in the case of symptomatic or saccular aneurysms.
Operative treatment of AAA may be open or endovascular surgery. Open surgery involves the partial resection of the aneurysm sac through an abdominal incision, along with aorto-aortic synthetic graft interposition (tubing) or aortobiiliac/aortobifemoral prosthesis implantation. In the course of endovascular treatment, a stent graft is implanted into the intended position via the femoral artery under X-ray guidance.
Iliac aneurysm
The aneurysm of the iliac artery is rare, and often occurs in combination with abdominal aortic aneurysm. It may develop most often in the common iliac artery and usually cause few symptoms. If the diameter of the aneurysm is over 3 cm, elective surgery should be considered. Surgery includes stent graft implantation or open surgery (aortofemoral, aortobifemoral bypass).
Thoracic aortic aneurysm (ThAA)
Thoracic aortic aneurysm usually develops due to atherosclerosis. Aneurysms are distinguished according to the involved segments of the aorta to aneurysm of the ascending aorta, the aortic arch, and the descending aorta. In the majority of cases, thoracic aortic aneurysm remains asymptomatic, and may be an incidental finding (thoracic X-ray). Significant rupture risk is present if the aneurysm has a diameter over 6 cm – which size is the threshold of surgical indication -, rupture has an extremely high mortality rate. Operative treatment of ThAA may be open, endovascular or hybrid surgery. Open surgery refers to synthetic graft interposition, endovascular surgery most often refers to the implantation of a stent graft, the combination of the two methods is hybrid surgery, which has an open surgery component (the repositioning of the supra-aortic blood vessels called debranching) followed by stent graft implantation.
Peripheral aneurysms
Popliteal aneurysm is the most common peripheral aneurysm. It frequently co-occurs with abdominal aortic or iliofemoral aneurysm (30%). Popliteal aneurysm has very few symptoms, the most at-risk group consists of men in the 6th to 7th decades of their lives. Its most common complications are embolization and thrombosis, rupture is uncommon. The primary method to examine popliteal aneurysms is duplex ultrasound, surgical planning is usually performed using CTA. The treatment of popliteal aneurysm is usually open surgery, which refers to interposition or bypassing with synthetic, autologous or homologous graft.
Femoral aneurysm is a rare type of vascular dilation and most often occur in the 7th decade of the patient’s life, and men are predominantly affected. The disease usually remains asymptomatic. It is relatively easy to diagnose during physical examination however, duplex US and CTA are necessary for treatment planning. Endovascular surgery (covered stent) and open surgery (synthetic graft or biological graft interposition) are equally possible to perform.
Subclavian and axillary aneurysms are are very rare types of aneurysm. These aneurysms usually manifest in the 6th decade of the patient’s life, most often as an asymptomatic supra- or infraclavicular pulsatile swelling. Symptoms are caused by the compression of tissues (brachial plexus, trachea, esophagus, superior vena cava); ischemic symptoms caused by thromboembolic occlusion; or rupture. CTA is the best suited method for diagnosis and surgery planning. Open surgery means the resection of the aneurysm and interposition with synthetic, autologous, or homologous graft. Endovascular intervention refers to covered stent implantation.
Summary
Aneurysms are rare vascular diseases, which can lead to life-threatening condition.
If the disease is asymptomatic, regular follow-up with medical imaging and vascular surgery consultation is indicated. Ideally, aneurysm surgery – open or endovascular – is performed at leading vascular centers.