AORTIC ANEURYSM & DISSECTION

AORTIC ANEURYSM 

The aorta is the largest artery in the body

It is the main blood vessel that carries blood from the heart to the rest of the body. It is situated mainly next to the spine and extends from the heart into the chest, down to the abdomen and into the pelvis where it branches into the iliac arteries. From the iliac arteries, it then goes down to form the main blood supply to the lower limbs. During its course, it gives off vital branches that form the key arterial blood supply to vital organs such as the liver and stomach (Celiac artery), the intestines (the Superior Mesenteric Artery) and the kidneys (the Renal Arteries).

An Aortic Aneurysm (AA) develops when the wall of the aorta weakens and begins to bulge outwards like a balloon. 

Over time, the aneurysm can enlarge and if left untreated can spontaneously rupture, resulting in massive internal bleeding. An AA  can develop along the whole course of the aorta, either in the chest (a Thoracic Aortic Aneurysm or TAA), in the abdomen (an Abdominal Aortic Aneurysm or AAA) or in the region stretching from the thorax into abdomen (a Thoraco-Abdominal Aortic Aneurysm or TAAA).

WHO IS AT RISK?

  1. Chronic smokers
  2. Those older than 65 yrs, predominantly males
  3. Those suffering from long-term hypertension and/or heart disease
  4. Those with congenital soft tissue diseases such as Marfan’ syndrome, Ehlers-Danlos Syndrome, Loeys-Dietz Syndrome
  5. Strong family history of aortic aneurysms and dissections

Patients are strongly advised to undergo screening for AA if they belong to any of the above risk factor groups.

IS THIS A SERIOUS CONDITION?

In its early stages, when an AA  is small in size, it does not pose an immediate health risk. However, having an AA will require regular close monitoring and follow-up, for instance repeat ultrasounds or CT scans at 3-6 monthly intervals.

If the AA continues to grow, the walls of the aorta or iliac arteries can become thin and lose their ability to stretch. The weakened sections of wall may become unable to support the force and pressure of blood flow. Such an aneurysm could burst, causing serious internal bleeding and death.

SYMPTOMS

  1. Pain – a persistent and severe pain in the chest, abdomen and back or in the lower limbs 
  2. Persistent fever 
  3. A  pulsating or throbbing mass in their abdomen
  4. Gangrene patches in the toes 
  5. Recurrent vomiting after eating

DIAGNOSIS

  1. Diagnosis is based on clinical examination where an aneurysm can be felt as a throbbing mass in the abdomen
  2. An ultrasound scan or CT scan is recommended for confirmation of an aneurysm
  3. Markers for aneurysm rupture include the presence of a saccular aneurysm (an round outpouching of the aorta), the presence of infection (an infected or mycotic aneurysm), or rapid growth in diameter of the aneurysm (more than 0.5 cm within 6 months).

TREATMENT

There are two types of treatment for AA:

  • Open Surgical Repair

This is the traditional method of aneurysm repair and involves making long incisions or cuts on the chest wall (for TAA) or abdomen (for AAA) or both (for TAAA), cutting the surrounding tissue down to the aneurysm before applying clamps to stop blood flow so that the aneurysm can be excised and replaced with an artificial tube graft. 

Open repair is a sturdy method but has significant morbidity and mortality risks due to its invasive nature. As such, it is recommended only for younger patients with low surgical risk. Post surgery recovery for open surgical repair usually require ICU care in bed for up to 1 week post-surgery. And patients generally take about 1 month to 6 weeks to fully recover from the incisions made during open repair.

  • Minimally Invasive Repair

This method which uses covered stent grafts is also known as EndoVascular Aortic Repair (EVAR).  This involves the deployment of special covered stents inside the aneurysm such that it relines the aneurysm and excludes it from the arterial blood pressure circulation. The stents are inserted through the leg femoral arteries via small (1cm) incisions in the groin. X-ray guidance (fluoroscopy) is used to help position the stent grafts correctly inside the aneurysms. 

The EVAR procedure does not require big incisions and the aortic blood flow is not disrupted by clamps during the procedure. As such, EVAR can be done for older patients or patients with many co-morbid disease who have higher surgical risks. Also, due to its minimally invasive nature, EVAR can be done under local anaesthetic and mild sedation. EVAR is also recommended for difficult and complex aneurysms involving the key organ arteries (thoracoabdominal aneurysm or TAAA) or for thoracic aneurysms (TAA) where exposure of the aorta in open repair is associated with significant morbidity.

Patients who undergo EVAR usually do not require ICU stay and usually spend one night in a high-dependency ward. Because there are no major incisions, patients usually are up and about in 8 hours and are discharged well in 48 hours post-surgery. In selected cases, young and fit patients can even have EVAR done and discharged on the same day.

FOLLOW UP CARE

After the AA has been treated, all patients should have regular follow-up for life. This is because AA disease is degenerative in nature and can continue to develop in other parts of the aorta that were previously aneurysm-free. It is not uncommon for a patient with an abdominal aneurysm to subsequently develop a thoracic aneurysm and vice versa. This is especially so if the patient still has persistent risk factors such as smoking and hypertension. Follow-up post aneurysm repair requires repeat ultrasound scans and CT scans to be done at regular intervals (6 monthly at first and then annually). This is especially so for patients who have undergone the EVAR procedure and the scans are done to detect leaks around the covered stent graft.

AORTIC DISSECTION 

An aortic dissection happens when there is a tear in the wall of the aorta, resulting in blood flowing in between the muscle layers of the aorta.  As a result, the aorta is divided into 2 lumens – a true and a false lumen.  An aortic dissection can disrupt flow into the branches arteries and organs supplied by the aorta e.g intestines, kidneys , legs thus causing the affected organ to potentially die.  

WHO IS AT RISK?

  1.  Those suffering from uncontrolled hypertension
  2. Those with congenital soft tissue diseases such as Marfan’ syndrome, Ehlers-Danlos Syndrome, Loeys-Dietz Syndrome
  3. Those who may have sustained trauma to the aorta e.g a motor vehicle accident

SYMPTOMS

  1. Severe chest pain associated with elevated blood pressure
  2. Local abdominal pain and tenderness 

DIAGNOSIS

A contrast CT scan of the chest and abdomen is the best way to diagnose an aortic dissection. It will also show us where the initial tear in the aortic wall is, the extent of the dissection (which parts of the aorta is involved), the affected organs and blood supply as well as give the doctors an idea of the best way to treat the dissection.

TREATMENT

  1. In an acute situation, the main goal is to control the elevated blood pressure so that the dissection does not worsen.  
  2. Then either open surgery to repair the tear of the aortic wall or minimally invasive EVAR – the insertion of a stent graft through the groin arteries under fluoroscopic (X-ray guidance).