What is Aortic Arch Aneurysm?
An isolated aortic arch aneurysm is a fairly rare condition, and since it tends to grow slowly, it often goes unnoticed. Aortic arch aneurysms typically exist alongside aneurysms in the neighbouring ascending or descending aorta. The exact frequency and natural course of these aneurysms are somewhat unknown, but they pose a significant challenge in surgical treatment, and complications can include brain injury and dangerous events related to the cardiovascular system.
An aneurysm is a health condition where a section of a blood vessel swells due to disease. All three layers of the vessel wall are involved, and the swell has to show at least a 50% increase in size compared to the expected size of the artery. An aortic arch aneurysm occurs in the upper chest and affects the blood vessels off of the aorta.
The aortic arch is a major artery in the body that develops from the left branch of the fourth building block of the throat in early development. The aortic arch connects the upward part of the aorta – the main artery carrying blood from the heart to the rest of the body – to the descending aorta. The aortic arch is located to the left of the windpipe and descends down, ending next to the bottom of the fourth thoracic vertebrae, where it continues as the descending aorta.
There are three main offshoots from the arch-like curve of the aortic arch:
1. The brachiocephalic trunk – It divides into the right subclavian and right common carotid arteries, sending blood to the right arm and the right side of the head and neck.
2. The left common carotid artery – This supplies blood to the left side of the head and neck.
3. The left subclavian artery – This is the furthest branch off the arch and sends blood to the left arm.
What Causes Aortic Arch Aneurysm?
Aortic aneurysms can be caused by a number of things, but the most common cause is the build-up of plaque within the arteries, also known as atherosclerosis. This happens throughout the body, but it’s particularly important when it happens in the aortic arch or the descending aorta.
In the case of the ascending thoracic aorta, these aneurysms are often brought on by a condition called cystic medial degeneration. There are a number of attributing factors to this, including various genetic disorders like Marfan syndrome, Loeys-Dietz syndrome, Ehlers-Danlos syndrome, Turner syndrome, familial aneurysm syndrome, and Behcet disease. On top of these, injuries that cause a rapid reduction in speed can also cause the segment just after the aortic arch to dilate.
In addition, certain infections or inflammatory conditions affecting the aorta can also result in an aortic aneurysm. These include syphilis, giant cell arteritis, and Takayasu arteritis.
Although the main risk factors for atherosclerosis include habits like smoking, high blood pressure, and high cholesterol, anything that increases stress on the wall of the aorta can also increase the risk of an aortic aneurysm. This includes certain conditions like pheochromocytoma, the use of drugs like cocaine, lifting heavy weights, and aortic coarctation.
Risk Factors and Frequency for Aortic Arch Aneurysm
Aortic aneurysms often don’t show symptoms, so it’s hard to know exactly how common they are. Many cases are found by accident. However, experts estimate around 10 cases of thoracic aortic aneurysms (TAAs) occur per 100,000 person-years. Aneurysms in the aortic arch (the top part of the aorta) make up about 10% of all TAAs.
- Males are two to four times more likely to have an aortic aneurysm than females.
- Most patients with aortic aneurysms are in their sixties or seventies.
- With better screening and imaging techniques, doctors are finding more aortic aneurysms.
- But it’s unclear whether more people are actually getting this disease, or whether we’re just getting better at finding it.
Signs and Symptoms of Aortic Arch Aneurysm
Aortic arch aneurysms, which are expansions of the aorta (the main blood vessel in the body), often go unnoticed as they don’t always produce symptoms. Many people with an aortic arch aneurysm won’t know they have it unless their doctor finds it during tests for another condition. Some people might feel a vague discomfort in the chest, neck, or jaw if the aneurysm is in the arch of the aorta.
Large aneurysms can press against nearby body parts, which can cause a variety of symptoms:
- Hoarseness due to the stretching of the left recurrent laryngeal nerve
- Noisy breathing, or stridor, from pressure on the trachea or bronchial tubes
- Cough, difficulty breathing, and repeated lung inflammation due to lung compression
- Difficulty swallowing as a result of pressure on the esophagus
- Swelling and redness from compression of the superior vena cava, a large vein that carries deoxygenated blood from the upper body to the heart
The most dangerous complications of aortic arch aneurysms are aortic dissection or aortic rupture, which cause intense chest pain and low blood pressure, respectively. Other less common complications include blood clots that can travel to other parts of the body, and bleeding into the gastrointestinal tract due to a fistula, which is an abnormal connection between the aorta and the esophagus.
Testing for Aortic Arch Aneurysm
Thoracic aortic aneurysms are often suspected on routine chest x-ray films, taken for reasons unrelated to aneurysm suspicion. These aneurysms can cause changes in the chest, including a widened or abnormal shape in the chest’s middle section, or a shifted windpipe. However, chest x-rays aren’t always able to clearly identify aortic aneurysms. They also can’t always differentiate an aneurysm from other conditions like a mass in the chest’s middle section, tortuous aorta, or aortic dissection, which can have similar features on the x-ray. Therefore, more specific aortic imaging is required.
Computed tomography angiography (CTA) or magnetic resonance angiography (MRA) are the preferred imaging techniques for accurately detecting and measuring thoracic aortic aneurysms. They allow doctors to thoroughly evaluate the aorta’s size, shape, involvement of branch arteries, and rule out other potential conditions. However, CTA and MRA can be less suitable for patients with decreased kidney function, as CTA requires an injection of contrast dye and MRA usually requires the use of a substance called gadolinium.
Echocardiography, a type of ultrasound, can also be used to view the aorta and its major branches. Different viewing angles are beneficial, depending on what section of the aorta and which arteries are suspected to be involved. Sometimes, further investigations like coronary angiography and carotid duplex scanning are carried out to assess the heart’s health and blood flow to the brain, especially if surgery involving the aortic arch process is considered. These investigations can help determine whether additional heart procedures are needed concurrently.
If a thoracic aortic aneurysm is detected, imaging of the abdominal aorta is recommended as well; this is to check if an abdominal aortic aneurysm is also present.
Treatment Options for Aortic Arch Aneurysm
The first step in treating an aortic arch aneurysm is to prescribe medication that can help keep risk factors for atherosclerosis, like high blood pressure and high cholesterol, under control. This helps to slow down the growth of the aneurysm and reduces the chance of further complications such as rupture or dissection.
Medical guidelines recommend that people with these aneurysms, whether they are small or in patients not suitable for surgery, must strictly manage high blood pressure, maintain an optimal lipid or cholesterol profile, and quit smoking. Educating patients to recognize signs and symptoms of related issues is also key, as is regular screening for growth of the aneurysm and counseling for individuals who might have a related genetic disorder.
Guidelines also suggest that regular imaging using CT or MRI is necessary to monitor the size of the aneurysm. For smaller aneurysms, up to 4.0 cm, imaging should be done annually. But for larger ones, 4.0 cm or greater in diameter, these check-up images should be taken every 6 months.
Surgical intervention for aortic arch aneurysms can be complicated and carries a higher risk of death. The decision to operate is a balance between the risk the procedure itself and the danger of the aortic aneurysm rupturing.
There are set criteria for which patients should be considered for surgery. These include patients who have a large aortic arch aneurysm, more than 5.5 cm in diameter, or those who will also have surgery for an adjacent aneurysm. Surgical treatment is recommended for all patients who show symptoms of an aneurysm, those with a fast-growing aneurysm, and those with an aneurysm size of more than 5.5 cm.
Surgical techniques have improved substantially over the years, as have anesthetic practices and ways of maintaining blood flow to crucial parts of the body during surgery. Alongside these advancements are emerging treatments to repair the aneurysm with less invasive surgery and new technologies, making it possible to operate on more patients, including those at high risk with multiple health issues. The choice of surgical procedure is dependent on various factors including the patient’s overall risk, the presence of other diseases, and the specifics of the aneurysm.
One such procedure is the ‘elephant trunk’ procedure which involves repairing the ascending aorta and aortic arch and placing a ‘trunk’ in the first stage. The second stage involves surgery on the descending aorta using a technique called thoracic endovascular stent grafting (TEVAR).
A less invasive procedure, known as hybrid surgery, combines conventional open heart surgery with endovascular procedures. This is a safer option for patients with multiple health issues who might not tolerate open heart surgery.
New emerging procedures use advanced technology to repair the aortic arch through small incisions using devices called endografts. These operations have been successful but more extensive studies are needed to fully understand their long term effects and durability.
What else can Aortic Arch Aneurysm be?
Other conditions that affect the aortic arch and cause it to expand, like pseudo-aneurysms, intramural hemorrhages, and aortic dissections, might bring about symptoms similar to those of an aortic arch aneurysm. Pseudoaneurysms often occur after an injury due to a sudden slowdown or a twisting trauma, like during accidents or falls. The chest pain associated with an aortic dissection is usually very intense, often described as being sharp or like tearing.
Other aortic problems and conditions, such as mediastinal masses, a bending aorta, and aging-related dilation (senile ectasia), can mimic the results seen on a plain X-ray of a thoracic aneurysm. These results could include a broadened shadow of the space between the lungs (mediastinal silhouette) and changes in the outline of the aorta. Because of this, additional confirmatory tests like angiograms may be required to distinguish these disorders correctly.
What to expect with Aortic Arch Aneurysm
The outlook for aortic arch aneurysm – a bulging area in the body’s main artery – largely hinges on its size. The size of the aneurysm and how fast it’s growing are the key factors that determine the likelihood of it bursting. If treated before it ruptures, the prognosis is typically good. However, if it does rupture, the risk of death can be as high as 80% according to some studies.
Possible Complications When Diagnosed with Aortic Arch Aneurysm
Aneurysms in the aortic arch can have severe adverse effects, including life-threatening heart and brain complications. The consequences can be quite severe, including the aorta rupturing typically into the left chest or pericardium. This rupture can cause severe chest pain, low blood pressure, or even shock. Other complications can be the layering in the aorta tearing or chunks of plaque breaking off and causing strokes. There are also some unusual complications such as the formation of abnormal connections between the aorta and esophagus, or the aorta and bronchial tubes.
Surgery to repair the aorta can also bring about additional complications. These include the possibility of clots breaking off during the repair, which could lead to a stroke or a reduction in blood flow to the spine. Other concerns include leaks from the graft used in the repair, and the formation of hematomas (pools of clotted blood).
Potential Complications:
- Aorta rupturing
- Severe chest pain
- Low blood pressure or shock
- Aorta tearing
- Strokes due to chunks of aortic plaque breaking off
- Abnormal connections between the aorta and the esophagus or bronchial tubes
- Clots causing stroke or reduced spine blood flow during surgery
- Leaks from the repair graft
- Formation of hematomas
Preventing Aortic Arch Aneurysm
It’s essential to educate patients about the various risk factors that could lead to the development of an aortic arch aneurysm. They should know the importance of their prescribed treatment and lifestyle changes they can make to limit its growth. Additionally, if an individual already has an aortic arch aneurysm, they need to be made aware of the potential signs and symptoms associated with complications. Understanding the necessity of regular imaging scans and recognising when surgical intervention might be needed will also inform their healthcare journey. Remember, staying informed is key to successful management.
