Aortic Aneurysms

The aorta is the body’s largest artery (a blood vessel that carries oxygen-rich blood). Roughly the diameter of a garden hose, this artery extends from the heart down through the chest and abdominal region, where it divides into a blood vessel that supplies each leg. An aneurysm is a balloon-like bulge in the aortic artery that occurs when the wall of the vessel becomes weakened. Blood pressure forces it to bulge outward, forming something similar to a blister.

An aneurysm is defined as a permanent focal dilatation of an artery having at least 50% increase in diameter compared with expected aortic diameter for the size of the patient.

Because thoracic aortic aneurysms usually develop slowly and do not cause many symptoms, they can be hard for doctors to detect and diagnose. Unless the aneurysm has expanded significantly or ruptured, a physical exam by your doctor likely will be normal.

Undergoing imaging tests for other symptoms or conditions is often how thoracic aortic aneurysms are detected. These tests can include a chest x-ray, echocardiogram (ultrasound of the heart and part of the aorta), a computed tomography (CT) scan, or a magnetic resonance imaging (MRI). A CT scan or MRI show the size of the aorta and the exact location of the aneurysm.

Thoracic aortic aneurysms are usually diagnosed when patients reach their 6th and 7th decades of life. Aneurysms in patients younger than 40 usually involve the ascending aorta due to weakening of the aortic wall.

Many factors can contribute to the development of an aortic aneurysm. Some of the most common conditions associated with aneurysm formation are:

  • High blood pressure (hypertension)
  • Smoking, causing injury of the wall of the aorta
  • Hardening of the arteries (atherosclerosis): fat, cholesterol, and other substances (plaque) clog the arteries
  • Changes in your aorta due to advanced age, the size of all aortas is increasing with age
  • Inflammation of your aorta
  • Injury from falls or motor vehicle accidents
  • Untreated infection such as syphilis or salmonella
  • Congenital or genetic causes of weakness of the artery wall (present from birth), such as Marfan or Ehlers-Danlos syndrome

Approximately 10% of patients may have other family members who have aortic aneurysms. The principal causes of death due to thoracic aneurysmal disease are dissection and rupture.

The diameter of the thoracic aorta is a reliable indicator of the severity of aneurysmal degeneration. It is the most important criterion that we have identified to estimate the risk of the catastrophic complications, aortic rupture and dissection, and therefore to guide preemptive surgical correction, so as to protect patients from these devastating events. Current guidelines recommend prophylactic surgical intervention at an aortic diameter of 5.5 cm for asymptomatic patients, and between 4.0 and 5.0 cm for Marfan syndrome and other genetically-mediated thoracic aortic aneurysms.

Relative aortic aneurysm size in relation to body height may be more important than absolute aortic size in predicting complications. Patients are stratified into four risk categories and we generally recommend aortic surgical repair for patients in the moderate-risk category with an AHI of 2.44 to 3.17 cm/m

Rapid expansion in aortic diameter is also a surgical indication. Aneurysm growth averages 0.07 cm/year in the ascending aorta and 0.19 cm/year in the descending aorta. A growth rate of 1 cm/year or faster is an indication for surgical repair.

Positive family history of aortic dissection significantly increases the risk of developing a new dissection in unaffected family members. Patient within a decade of the age of dissection of their relative (or even earlier) should receive frequent monitoring of the size of their aorta and be should be strongly considered for a surgical intervention even at moderate aortic size.

There is evidence to show that specific gene mutations confer a specific increased risk for adverse outcomes, even at small or normal aortic sizes. It has been recognized that aortic dissection in Marfan syndrome patients can occur at smaller sizes, therefore we recommend early intervention at 5 cm for the ascending aorta and 6 cm for the descending aorta.

The decision to operate on an aortic aneurysm depends entirely on the safety with which the operation can be performed—with the risk of aneurysmal rupture and dissection being weighed against the inherent risk of the surgical procedure itself, which over the years, has become considerably safer – especially when performed by sub-specialist aortic surgeons, at appropriate centers of excellence and with the help and support of sub-specialist, multidisciplinary aortic team.

Note: patients with symptoms should undergo repair of their aneurysm regardless of size. Acutely symptomatic patients require emergency operation.

Thoracic aortic aneurysm and bicuspid (bileaflet) aortic valve (BAV)

Bicuspid (bileaflet) Aortic Valve disease (the disease where the aortic valve has two instead of three cusps (or otherwise known as leaflets) is also a heritable disorder, is known to have an increased risk of ascending aortic aneurysm as well. Bicuspid aortic valve (BAV) disease is the most common congenital cardiac disorder, being present in 1-2% of the general population. Approximately 9% to 15% of first-order family members also have BAV disease, with men and women equally affected within family members. The heritability of BAV disease is more than 80%, and approximately 9% to 15% of first degree relatives have the disorder. Therefore, it is recommended that first-degree relatives of patients with BAV are screened with echocardiography

In BAV disease, valvular complications (aortic valve stenosis or regurgitation) progress at their own independent rates, different from the rate of progression of the bicuspid aneurysm. Patients with pure/predominant BAV aortic regurgitation (10% to 15% cases of BAV) tent to be younger and males.

BAV aortopathy and aortic aneurysm is a common finding in patients with BAV disease and as high as 40%. Aneurysmal dilatatation in BAV aortopathy may occur in the aortic root, the tubular ascending aorta (most common, 60-70%), the proximal aortic arch, or any contiguous combination of these three. Although only 5% or less of patients with BAV will have aortic dissection over a lifetime, so BAV is an important cause of aortic dissection. Patients with BAV and aortic valve disease (stenosis or regurgitation) are at increased risk of rupture and dissection of the aorta. Evidence increasingly demonstrate that BAV with aortic regurgitationcan be more malignant phenotype than BAV with aortic stenosis BAV, with a higher risk (10x) of aortic dissection.

BAV pathologyBAV aortopathy consists of premature changes to the consistency of the aortic wall (cystic medial degeneration) in approximately one half of the patients who had surgery for BAVs. Valve mediated blood flow dynamics and regional wall stress differences are associated with changes in regional aortic wall histology and proteolytic events which are known to contribute towards the premature changes to the consistency of the aortic wall. Both genetic predisposition and rheological abnormalities may coexist, resulting in diverse clinical presentations, with distinct natural histories.

Prophylactic aortic repair is recommended to prevent catastrophic aortic complications, particularly aortic dissection and rupture. Although aortic diameter is currently the major criterion for timing of elective surgical repair of ascending aortic aneurysms, it is an imperfect predictor of aortic dissection or rupture (50 mm aorta could represent moderate dilatation in a large man but may be severe dilatation in a small woman) and correction for body size parameters should be taken to account. The ratio of aortic cross-sectional area divided r2 π (cm2)/ by height [ratio height (m)] has also been proposed as a method to correct for body size with a cutoff of 13cm2/m  for the tubular ascending aorta and 10cm2/m for the root exhibited superior predictive accuracy for the occurrence of dissection than absolute aortic diameter cutoffs.

Indications for Elective Surgical Repair of DilateAscending Aorta/Aortic Root/Aortic Arch Associated With Bicuspid aortic valve (BAV)
  • Repair of the ascending aorta/root is recommended when:
    • The diameter is >5.5 cm in patients with no risk factor
    • The diameter is ≥50 mm and no risk factors, when the patients are at low surgical risk and operated on by an experienced aortic team in a center with established surgical results.
    • The diameter is <5.0 cm associated with any of the following:
      • Root phenotype or predominant aortic valve regurgitation,
      • Uncontrolled hypertension,
      • Family history of aortic dissection/sudden death,
      • Aortic coarctation,
      • Aortic diameter growth >3 mm/y
      • Small adult body size (especially if they have Turner’s syndrome), indicated by either of the following:
        • aortic cross-sectional area to height ratio of > 10 cm2/m
        • Indexted aortic diameter of >2,75 cm/m2
      • Women planning pregnancy because of an increased risk of aortic complications in such patients
      • Patients with BAV aortic regurgitation and root phenotype of aortic dilation at an aortic diameter of 5.0 cm. Such patients may particularly benefit from a valve-sparing aortic root replacement (David) operation, if done in an experienced center with known outcomes.
  • Concomitant repair of the ascending aorta/ root should be performed when the aortic diameter is ≥45 mm in patients undergoing cardiac surgery.
  • Repair of the aortic arch is recommended:
    • When the aortic arch diameter is ≥55 mm.
    • Concomitantly for patients undergoing cardiac surgery for other reasons and have an aortic arch diameter of ≥50 mm
    • Concomitantly for patients undergoing cardiac surgery for other reasons and have aortic arch diameter of ≥45 mm, provided the patients are at low surgical risk and operated on by an experienced aortic team with established surgical results.
    • For patients undergoing elective aortic arch repair by an experienced aortic team with established surgical results.

Note: patients with symptoms should undergo repair of their aneurysm regardless of size. Acutely symptomatic patients require emergency operation.

Surgery for thoracic aortic aneurysms

An aneurysm can often be repaired before it bursts. Surgery involves replacing the weakened section of blood vessel an artificial tube (called a graft). Surgery to repair an aortic aneurysm depends on the size and location of the aneurysm and your overall health. Aortic aneurysms in the upper chest (the ascending aorta) are usually operated on straight away as they can become critical. Aneurysms in the lower chest and the area below your stomach (the descending thoracic and abdominal parts of the aorta) may not be as life threatening. Aneurysms in these locations are monitored for varying periods, depending on their size. If they grow over 4-5 centimetres (almost 2 inches) in diameter (depending on your height and health) or continue to grow fast and/or begin to cause you symptoms, you will be advised to proceed with surgery to stop the aneurysm from bursting.

Aortic aneurysms can involve the aortic arch with various degrees of complexity. Usually, patients with aortic arch aneurysms that do not involve the rest of the cardiovascular system are the exception rather than the rule. Open aortic arch replacement involving all 3 supra-aortic branches that supply with blood the head (brain) and both upper limps The “Elephant Trunk” technique is a technique that is often used to repair aortic arch aneurysms and provide the most optimal solution when secondary surgical to the descending thoracic aorta is anticipated via either an open procedure or intra-vascular stenting. When an intra-vascular procedure is anticipated, the hybrid “Frozen Elephant Trunk – FET” technique with a stent extension is most commonly used. Due to the advanced complexity of the procedure, which usually require deep hypothermia (very low temperature and cooling of the patient) and complex techniques in protecting the brain and other organs of the patient during the operation, these operations are usually performed by sub-specialist aortic surgeons

The simple ascending aorta aneurysm repair requires for your to stay at the hospital for 5-7 seven days and is done under general anaesthesia; this means you will be asleep during the procedure. Your hospital stay and the time spent in the intensive care however, may be prolonged depending on the extend and complexity of the surgery required.

Once the anaesthetic has taken effect, your surgeon will make an incision (traditionally about 25cm long, a mini sternotomy access is not appropriate here) down the middle of your breastbone and open the ribcage to reach the heart. The heart is stopped (using medication) and blood is re-routed to a heart-lung machine. This takes over the pumping action of the heart and lungs, adding oxygen to the blood and maintaining the circulation.

Your surgeon will remove the damaged part of the aorta and sew in an appropriately sized plastic tube. If the aneurysm extends up to your head and neck vessels, your temperature will be lowered to 15-27 oC and the blood circulation to your brain will be stopped very briefly. After finishing the aortic replacement, blood is then redirected back to your body and your heart is restarted. The breastbone is re-joined using wires and your chest is closed using dissolvable sutures, stitches or staples. The operation usually takes about 4-8 hours.

Dissection of the thoracic aorta

Aortic dissection is a tear in the wall of the aorta that causes blood to flow between the layers of the wall of the aorta and forces these layers apart. Aortic dissection is a medical emergency and can quickly lead to death, even with optimal treatment. If the dissection tears the aorta completely open (through all three layers), massive and rapid blood loss occurs. Aortic dissections resulting in rupture have an 80% mortality rate and 50% of patients die before they even reach the hospital.

Aortic dissection is associated with high blood pressure and many connective tissue disorders. It can also be the result of chest trauma. 72 to 80% of individuals diagnosed with an aortic dissection have a previous history of high blood pressure. Note that vasculitis (inflammation of an artery) is rarely associated with aortic dissection.

The highest occurrence of aortic dissection is in individuals who are 50 to 70 years old. The incidence is twice as high in males as in females (male-to-female ratio is 2:1). Half of dissections in females before age 40 occur during pregnancy (typically in the 3rd trimester or early postpartum period).

A bicuspid aortic valve (a type of congenital heart disease involving the aortic valve) is found in 7-14% of individuals who have an aortic dissection. These individuals are prone to dissection in the ascending aorta. The risk of dissection in individuals with bicuspid aortic valve is not associated with the amount of valve disease (stenosis).

Marfan syndrome is found in 5-9% of individuals who suffer from aortic dissection. Marfan syndrome is a genetic disorder of connective tissue. It is associated with aneurysms of the aorta as well as proximal aortic dissections and is likely to occur in younger individuals. Turner syndrome is also a genetic disorder which increases the risk of aortic dissection due to aortic root dilatation.

Aortic dissection due to chest trauma can be divided into two groups based on cause: blunt chest trauma (commonly seen in car accidents) or complications resulting from medical treatment. Complications include trauma during cardiac catheterization or due to an intra-aortic balloon pump. Aortic dissection may also occur as a late onset result of cardiac surgery. 18% of individuals who present with an acute aortic dissection have a history of open heart surgery.images-1

The acute Type A dissection represents a cardiac emergency. This type of disease requires an immediate replacement of the dissected part of the thoracic aorta (with inclusion of the “torn” part of aorta where the “hole” is). Usually, the ascending part of the thoracic aorta is replaced by a plastic tube, while the aortic valve (which is frequently leaking as a result) is usually repaired at the same time. The extend of the repair is dependent on a variety of factors and all above options in repairing aortic aneurysms may need to be explored at the time of the operation.

On certain occasions, where the tear involves the aortic root (the area where the heart joints the aorta) and/or the aortic arch (the area of the aorta where from the head and neck arteries come from) more extensive surgery is required and the need for extensive replacement of larger parts of the thoracic aorta is explored.

It is not uncommon that part of the remaining native thoracic aorta, despite been dissected, remains untouched and is treated at a later stage.

Endovascular repair of the thoracic aortic aneurysms (aortic stenting)

Endovascular means that surgery is performed inside your aorta using long, thin tubes called catheters without having to open the chest. A smallincision is made at the top of the leg (groin) and a catheter is passed into your femoral artery and up to the site of the aortic aneurysm. It is then used to guide and deliver a stent-graft to the effected area. The stent-graft is deployed in the diseased segment of the aorta and “relines” the aorta like a sleeve.

The endovascular stent-graft is a fabric tube supported by metal wire stents (also called a scaffold) that reinforces the weakened aneurysmal area. By sealing the area tightly above and below the aortic aneurysm, the graft allows blood to pass through it without pushing on the aneurysm.

Endovascular repair of thoracic aneurysms is generally less painful and has a lower risk of complications than traditional surgery because the incisions are smaller. Endovascular aortic aneurysm procedures also allow you to leave the hospital sooner and recover more quickly.

You may be eligible for endovascular stent grafting if your thoracic aneurysm has not ruptured and the aneurysm is greater than 5 cm in size. However, not all patients are a candidate for this procedure any potential surgery should be discussed with your cardiac surgeon.

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