Surgery for repair of aortic aneurysm

What is the aorta? 

The aorta is the main pipe or tube that originates from the outflow portion of the left side of the heart. Through this tube the heart pumps blood into the entire body. As the aorta goes out further from the heart it has branches to various parts of the body to supply blood to all organs. Part of the aorta within the chest is known as “Thoracic aorta” and part in the abdomen is known as “abdominal aorta” and hence the term thoracic aortic aneurysm or abdominal aortic aneurysm. The diameter of this tube varies between 3.0 to 4.0 cm and it varies according to height, gender and race of the patient. There is an outlet valve at the beginning of this tube which is known as the “aortic valve”. This valve, when functioning normally, is a one way valve, meaning that blood can only go out of the heart and cannot re-enter into the heart chamber.

Figure 1

When the diameter of the aorta is increased by 50% of what is expected for an individual it is known as an aneurysm of the aorta. In simple terms an aneurysm is bulging of a straight tube as seen in the diagram (Figure 1). It can affect various parts of the aorta (Picture/Figure 2). The complications of this condition depends on the location of the aneurysm and similarly the treatment varies according to the location of the aneurysm.

Type of aortic aneurysm

The aorta is a long tube and has been divided into several parts to enable description and type of treatment required.

Types of aortic aneurysm according to location

  • Aortic root aneurysm – this part, as the name implies is the very origin of the aorta from the heart. Aortic root includes origin of aorta, aortic valve, which is an outlet valve, and origin of coronary arteries that supplies blood to heart muscle.
  • Ascending aortic aneurysm – As the aorta comes out of the heart it ascends in the upright body towards the head. This part of the aorta is known as the ascending aorta and an aneurysm of this part is known as ascending aortic aneurysm.
  • Aortic arch aneurysm – After the aorta has ascended towards the head it takes a gentle curve just below the neck of the human body to descend in the body. This curve looks like an arch, hence the name aortic arch. An aneurysm of this part is known as aortic arch aneurysm.
  • Descending thoracic aortic aneurysm – after the formation of the arch , the aorta descends towards the lower part of the body. An aneurysm of this part is known as descending thoracic aortic aneurysm.

What are the complications of aortic aneurysm?

The most feared complication is rupture of the aorta, which is a fatal complication. The other most feared complication is known as “ Dissection of Aorta” which leads to death in 50% of patients in 48 hrs if untreated. Dissection means a tear in the wall of the aorta resulting in a weakened wall that can lead to rupture and death.

Other complications can arise due to compression of the surrounding structures eg. Nerves, cardiac chambers, rib cage or sternum

What are the symptoms of aortic aneurysm?

Most aortic aneurysms are diagnosed incidentally while investigating other conditions. Most aneurysms that don’t cause any symptoms are discovered as a surprise to patients. The most important symptom is severe central chest pain radiating to the back which indicates that the aneurysm is expanding or impending rupture. In such circumstances patients are advised to attend ED straight away.

What causes an aneurysm to develop?

  1. Hypertension
  2. Genetic conditions/connective tissue disorders
  3. Infection/inflammation
  4. Life style – heavy weight lifting
  5. Pregnancy

How to diagnose an aneurysm?
Most aneurysms are diagnosed incidentally when patients are investigated for chest pain or other chest conditions.

The best and most reliable test is a CT scan of the chest with contrast (A scan with dye injected into the aorta). Most CT scans are done for other conditions and may have been done without contrast. Aortic surgeons may arrange for you to have a special CT scan to assess your condition further. Another common test is Echocardiogram (Ultrasound of heart). This simple test is great in diagnosis of an aneurysm but not reliable for assessing accurate diameter. Aortic surgeons will arrange a CT scan if the aneurysm has been diagnosed on echocardiogram. The other limitation of echocardiogram is that it can only reliably assess the beginning of the aorta while a CT scan allows the aortic surgeon to assess the entire aorta from beginning to end.

What type of treatment is required?

Not every aortic aneurysm requires surgery. There are criteria and guidelines to guide Aortic surgeons. Unfortunately these guidelines have limitations and are not based on robust scientific evidence but nonetheless form a great foundation for guiding treatment.

Most guidelines and statements would agree that aneurysms will require surgical resection and repair when the diameter exceeds 5.5cm. However, surgeons experienced in aortic surgery may offer surgical treatment at lower dimensions after discussing with individual patients. This is due to marked variation in normal aortic diameter based on height, race and sex. For example : someone who is 160cm tall, with a diameter of 5cm will be as dangerous as 5.5cm for someone who is 180cm tall. Therefore, surgery may be considered at smaller diameter in short stature patients depending on the expertise of the aortic surgeon. The other factors that play an important role in surgery being considered at diameter less than 5.5cm are – genetic conditions/connective tissue disorders, family history of death due to aneurysm, uncontrolled hypertension, social circumstances etc

When your surgeon decides that you don’t need surgery, he will refer you back to your GP or cardiologist. They shall arrange for you to have a regular CT scan/ MRI or echocardiogram to monitor any progression in the aneurysm size. Meanwhile you will be commenced on blood pressure tablets or cholesterol lowering medications.

Surgery for Aneurysm:

The majority of these surgeries will require an incision on your breastbone (sternotomy). This will be done by a heart surgeon or aortic surgeon under general anaesthetic. The heart will be connected to the heart lung machine. Depending on the location of the aneurysm, this operation can be simple or quite complex. Simple repair requires replacing just the ascending aorta (Figure 2) without replacing the valve or anything else. While complex repair may require repair or replacement of the aortic valve, reimplanting blood supply of the entire heart, or reimplanting blood vessels that take blood to the brain.

Figure 2

While connected to the heart lung machine, body temperature is lowered to protect the brain and other organ function. For complex repair, body temperature may be lowered to 20-25 degrees celsius and blood circulation may be completely stopped for up to 30 mins  to carry out the repair. The surgeon will use an artificial tube made from special cloth (polymer resin from polyester fibre) to replace the aneurysm. This artificial tube can remain in your body for life and the body will grow a capsule around it over time. Once the surgical part is completed the patient’s body is rewarmed to normal temperature and separated from the heart lung machine. The chest is closed and the patient is transferred to the ICU. Patients are electively placed on a breathing machine to monitor vital body signs and ensure a period of stability after major surgery prior to waking up.

Majority of these surgeries will require incision on your breastbone(sternotomy). This will be done by heart surgeon or aortic surgeon under general anaesthetic. Heart will be connected to heart lung machine. Depending on the location of aneurysm, this operation can be simple or quite complex. Simple repair requires replacing just the ascending aorta( picture) without replacing valve or anything else. While complex repair may require repair or replacement of aortic valve, or re implanting blood supply of entire heart, or reimplanting blood vessels that take blood to brain( picture).

 

While connected to heart lung machine, body temperature lowered to protect brain and other organ function. For complex repair, body temperature may be lowered to 20-25 degree C and blood circulation may be completely stopped for upto 30 mins  to carry out complex repair. Surgeon will use artificial tube made from special cloth(polymer resin from polyester fibre) to replace aneurysm. This artificial tube can remain in your body for lifetime and body will grow a capsule around it over time. Once the surgical part is completed patient’s body is rewarmed to normal temperature and separated from heart lung machine. Chest is closed and patient is shifted to ICU. Patients are electively placed on breathing machine to monitor vital body signs and ensure period of stability after major surgery prior to waking up.

Types of surgery for aortic aneurysm

  • Aortic root replacement : This surgery involves replacement of aortic valve , ascending aorta and reimplantation of coronary arteries. Aortic valve will be replaced with the tissue/biological or mechanical valve as discussed with you prior to surgery
  • Valve sparing aortic root replacement : This is a very specialised surgery and done by only handful of surgeons in Australia and around the world. In this surgery, aortic root is replaced but surgeon will reuse your own valve which may need some repair. The advantage of your retaining your own valve is that your own valve is the best tissue ever made for you
  • Ascending aorta replacement : This complex procedure is relatively simple compared to aortic root replacement as your valve and coronary arteries does not require anything done. Surgeon will simply replace ascending part of your aorta without touching aortic root.
  • Aortic Arch replacement : This is one of the most complex heart surgeries and requires surgeon to be very experienced in carrying out this surgery. Not all heart surgeons are proficient in doing this surgery. The complexity results from the requirement of managing branches of aortic arch that directly supplies blood to brain. Any complications in managing branches of arch vessels can result in life threatening stroke and hence the complexity. When surgeon replaces this part of the aortic arch he needs to reconnect brain vessels to arch. Typically patients body is cooled to 25 degree C or less to protect brain during this surgery. The surgery has associated complications of brain injury and bleeding
  • Descending thoracic aorta replacement : This surgeries are one of the most complex undertaking and fortunately don’t need to be done frequently due to advanced technology. This part of the aorta can now be treated with stents that can be inserted from groin without requiring heart surgery.

Death is a complication which is associated with any surgery, but it is very rare for that to occur during surgery. This surgery is a prophylactic surgery for most hence the expected risk of surgery should be less than expected risk of death from untreated aneurysm. Your surgeon will discuss this in detail with you.

Major complications that can occur are : infection, stroke, bleeding, heart attack and kidney failure. Depending on your health condition the chances of these complication can be very small to moderate.

Post operative bleeding may require blood transfusion or requirement of revisit to operation theatre to stop any new bleeding that may have started again after finishing primary operation.

Stroke is uncommon however, can be significant when dealing with complex repair that requires reimplantation of brain vessels.

Late complications are building up of fluid around your heart which may require drainage with a needle. Some patients can develop fever as a reaction to surgery and surgical material.

Please read heart surgery guide for other general complications.

When you wake up in ICU, you notice that you are connected to multiple monitoring lines, urinary catheter, intravenous catheters etc. This is part of normal procedure. It can be overwhelming for most patients but most of these lines are removed by day 3 or 4. The usual stay in ICU is about 2 days. For complex repairs it may be few days more. You will spend another 5-7 days in ward. Most patients after simple repair are expected to go home after a stay on 7 days on hospital. At this point in time majority of patients are expected to be independently mobile and capable of doing two flights of stairs( if you were able to do them before !) This is done with help of physiotherapist and rehab specialist.

You should ensure that you are accompanied by someone at home for first two weeks and you are advised to not drive for six weeks from the time of surgery. We would expect you to have achieved 80-90% of physical recovery by the end of six weeks.

Simple answer – Yes. That is the purpose of the operation. But in some patients it may not be achievable.

However, if you develop any complications then it may affect some functions of your life. You should be aware that you can develop aneurysm further in your aorta depending on your condition. This may require monitoring or modification of life style

You will be seen by Dr Joshi in his clinic after 6 weeks for review. He will advise you regarding long term follow up which can be either with himself or with your treating cardiologist.