Coronary Artery Aneurysm

Coronary artery aneurysm (CAA) is a rare but life-threatening condition that can cause serious complications such as blood clotting and vessel rupture. It has a significant impact on the heart and may result in death if left untreated.¹

Therefore, it is important to identify the signs and symptoms and seek medical care for proper diagnosis and management to minimise the risk of death. In this article, we will shed light on the topic of coronary artery aneurysms and provide valuable and relevant information on all aspects of this health issue.

What is coronary artery aneurysm?

A coronary artery aneurysm is the abnormal widening or outpouching of a coronary artery (the blood vessel which carries oxygenated blood to the heart), either in one part of the artery or widespread and affecting the whole segment.

In order to define the widening in the coronary artery as an aneurysm, the bulged part of the vessel needs to exceed the diameter of adjacent normal segments by at least 50%.²  

Coronary artery aneurysms are divided into two depending on their shape. In saccular aneurysms, the transverse diameter exceeds the longitudinal diameter. On the contrary, the longitudinal diameter exceeds the transverse diameter in fusiform aneurysms.³

Aneurysmal coronary artery disease (ACAD) is another term used to encompass both coronary artery aneurysms and coronary artery ectasia (CAE). Coronary artery ectasia is defined as a widening or bulging of the coronary artery affecting at least 50% of the artery’s length, resulting in a more widespread enlargement.⁴

Pathophysiology

The complete pathophysiology of coronary artery aneurysms is not fully understood. However, the destruction of the structures in the vessel wall plays a major role in the development of coronary artery aneurysms. Inflammation processes in the vascular wall involve the activation of certain enzymes called matrix metalloproteinases (MMPs). These enzymes are responsible for the destruction of the structural proteins in the vessel wall, resulting in the wall getting thinner and weaker.² Increased strain on the weakened vessel wall causes subsequent widening and aneurysm.

Studies have shown a strong association between atherosclerosis (fatty deposits within the walls of arteries) and coronary artery aneurysms. That means there is a possibility of a common underlying mechanism.⁵ 

There is also a high prevalence of aneurysms in other arteries seen in patients with a coronary artery aneurysm, suggesting the involvement of another mechanism other than atherosclerosis. 

Different studies and populations show an incidence of coronary artery aneurysms ranging from 0.3% to 5%. Studies also indicate that the sections of the arteries that are closer to the heart are more likely to be affected than the more distant parts, and the most affected artery is the right coronary artery.³

Causes, symptoms and diagnosis

It is important to understand and recognise the causes and symptoms of this condition in order to seek prompt medical treatment and reduce the risk of further complications.

What causes coronary artery aneurysms

There are many causes of coronary artery aneurysms, and the causes vary depending on the geographic location and the age. In the Western world, the most common cause is atherosclerosis, followed by congenital and infectious causes. However, in the Far East, Kawasaki disease is the most common cause. In terms of age, atherosclerotic aneurysms are the leading cause in adults, whereas Kawasaki is the most common cause in children.⁴

The following are the various causes of coronary artery aneurysms:⁵

• Atherosclerosis
• Inflammatory disorders
• Infectious disorders
• Congenital disorders
• Connective tissue disorders
• Drugs or certain medications
• Trauma
• Iatrogenic disorders

Atherosclerosis

Around half of coronary aneurysms are atherosclerotic in origin, making it the most common cause.²

Atherosclerosis is the build-up of plaque consisting of fat, cholesterol and other substances in the walls of the arteries. It causes the arteries to become narrowed and hardened, making the blood flow difficult. There is also a possibility of the plaque bursting and causing a blood clot.

The inflammatory cells present in the plaque produce some substances, which, in turn, secrete degrading enzymes. These enzymes damage the vessel wall, causing it to become thinner and weaker. 

Coronary aneurysms that are atherosclerotic in origin are usually multiple in number and involve more than one coronary artery. There is also an increased possibility of clot formation in atherosclerotic aneurysms.⁴

Inflammatory disorders

As discussed above, inflammation contributes to aneurysm formation. Thus, many inflammatory disorders can also cause aneurysm formation in the coronary arteries. Although the most well-known association is with Kawasaki disease, other disorders that might cause coronary aneurysm include Takayasu’s arteritis, polyarteritis nodosa, lupus, rheumatoid arthritis, giant cell arteritis, and Behcet’s.⁵

Kawasaki disease is the most common cause of aneurysmal coronary artery disease in children.⁴

Infectious disorders

Mycotic aneurysm is a type of aneurysm that is caused by an infection in the blood vessel wall. Pathogens, especially bacteria such as staphylococcus or streptococcus, are the most common causes. 

Pathogens can cause the formation of aneurysms as they grow and invade the vessel wall, as well as causing damage via immune complex deposition.⁶

Congenital disorders

A congenital condition is a defect that is present at the time of birth.

Congenital aneurysmal coronary artery disease is found to be related to coronary artery fistula in most reported cases, and they are often diagnosed in young individuals. A coronary fistula is an abnormal connection between a coronary artery and a heart chamber or a large vessel. While most coronary fistulas are congenital, they can also develop as a result of certain medical procedures such as heart surgery or biopsy.⁴

Connective tissue disorders

Certain connective tissue disorders such as Marfan syndrome, Ehlers-Danlos, fibromuscular dysplasia and polycystic kidney disease can cause coronary aneurysm as a complication.⁵

Drugs and certain medications

There is an increased prevalence of aneurysmal coronary artery disease in individuals who abuse cocaine. Cocaine abuse can result in vessel wall damage and atherosclerosis, paving the way to aneurysm.

Cocaine abuse may also cause heart attacks, rhythm disturbances, high blood pressure and problems with the blood vessels in the brain.⁴

Trauma and iatrogenic disorders

A coronary aneurysm can be induced through direct trauma after an incident and also after a medical treatment or diagnostic procedure that happens unintentionally, which is called iatrogenic. 

Interventions carried out on coronary arteries are rare causes of aneurysms. Such procedures include balloon or laser angioplasty, stent placement, and surgeries to remove atherosclerotic plaques. 

Trauma to the arterial wall, inflammatory or allergic reactions to stents, and delayed healing may be the underlying mechanisms for aneurysm formation after coronary interventions.⁴

What are the symptoms of coronary artery aneurysms

Most coronary artery aneurysms are present without symptoms and are only detected incidentally during an imaging procedure. Even though they are mostly silent, symptoms develop based on the underlying cause and extent of the aneurysm, as well as the result of complications. 

Coronary aneurysms due to atherosclerosis can present with symptoms similar to coronary artery disease or myocardial infarction (the medical term for heart attack).⁴ Such symptoms include chest pain or discomfort, shortness of breath, weakness, light-headedness, nausea, cold sweats, and pain in the arms or shoulders.

Congenital giant coronary artery aneurysms associated with fistulas might cause congestive heart failure and symptoms like tiredness and shortness of breath.⁷

Rupture of the heart muscle with consequent blood accumulation between the layers of the heart and cardiac tamponade is a possible complication, which might cause symptoms such as chest pain, fainting, and difficulty breathing. Other possible complications include clot formation in the coronary arteries, heart attack, and a tear in the layers of a vessel called dissection.⁴

How are coronary artery aneurysms diagnosed?

Different types of imaging techniques are used as diagnostic tools due to the variation in the presentation of coronary artery aneurysms. 

Although the gold standard method for diagnosis is coronary angiography, coronary artery aneurysms may also be diagnosed with non-invasive imaging such as echocardiography, CT, and MRI.

Coronary angiography is a type of imaging method in which a special dye (contrast material) and X-rays are used to demonstrate blood flow. It provides important information about the size, shape, location, and extension of aneurysms, as well as the severity of atherosclerosis. However, it provides limited information regarding the vessel wall. In order to have a better demonstration of the vessel wall, intravascular ultrasonography (IVUS) can be used alongside invasive angiography. IVUS can also be used to treat aneurysms.

Before the angiography, it is important to evaluate the benefits and risks of the procedure, especially in younger patients with Kawasaki disease. In children with Kawasaki disease, follow-up imaging methods without exposure to radiation, such as echocardiography and MR angiography, are often recommended.⁸  

Additional tests, including blood tests, may also be performed to identify the underlying cause of the coronary aneurysm. 

Treatment and prevention

How are coronary artery aneurysms treated?

There is a lack of clinical evidence and insufficient data in regard to the treatment of coronary artery aneurysms in both symptomatic and asymptomatic patients. Therefore, treatment strategies should be based on individual cases, considering the patient’s characteristics, clinical presentation, and the structure of the coronary artery aneurysm.³

Blood “thinners” are usually prescribed to patients with aneurysms who are at high risk of clot formation. 

Immunosuppressive therapy is used to improve the outcome of coronary aneurysms in patients with an inflammatory background.⁴

Percutaneous stent placement aims to set a stent inside a vessel lumen using thin, long tubes called catheters through a puncture site in the skin. Stents covered with polytetrafluoroethylene (PTFE) are effective in limiting the expansion of coronary aneurysms by decreasing blood flow within the widened segment, thus preventing a subsequent rupture, which is a potentially life-threatening complication of aneurysms. Coil embolisation to block a vessel is another percutaneous treatment option for coronary aneurysms.

For coronary aneurysms at least three times larger than the original diameter, patients with obstructive coronary artery disease, or those with a heart attack risk despite blood “thinners”, surgery may be required as part of the management. Surgery might involve ligation (tying off) or resection (removing) the aneurysm.⁴

How can we prevent coronary artery aneurysms?

Preventive methods for coronary artery aneurysms depend on the underlying cause. Although it may not be possible to prevent all cases, certain measures can help reduce the risk.

Prevention of atherosclerosis is an important step to prevent coronary aneurysms, as the most common cause of coronary aneurysms is atherosclerosis. 

High-dose intravenous therapy with immunoglobulins together with aspirin is an effective treatment choice to decrease coronary artery involvement in Kawasaki disease.⁴

Risk factors

Risk factors of coronary aneurysms can be modifiable or non-modifiable. 

Genetic susceptibility is a non-modifiable risk factor that suggestively plays a role in the development of coronary artery aneurysms, especially congenital ones.³ It is also suggested that genetic factors have a role in increasing the risk of coronary aneurysms in patients with Kawasaki disease; however, more evidence is needed.⁸

Coronary aneurysm predilection for people assigned male at birth (AMAB) over people assigned female at birth (AFAB) is reported in some studies.³

Coronary aneurysms are, in most cases, suggested to be a manifestation of atherosclerosis with a similar pathophysiology.⁵ Common modifiable risk factors that contribute to the formation of atherosclerosis include high blood pressure, diabetes, metabolic syndrome, and an unhealthy diet. On the other hand, risk factors such as family history, inflammatory diseases, and old age are non-modifiable risk factors for atherosclerosis.

Mycotic aneurysms are associated with certain risk factors, including low immune states, trauma to the arteries due to certain invasive procedures such as stent placement, and infections like endocarditis (infection in the inner lining of the heart), out of which endocarditis is the most common.⁶  

When to seek medical treatment

It is very important to seek appropriate medical management and expert advice to prevent possible complications of coronary aneurysms. The most important complications are clot formation, rupture, calcification (hardening of vessels), and distal embolisation (blockages in smaller blood vessels).⁹

If you experience any of the possible symptoms of coronary aneurysm, such as chest pain and light-headedness, or if you think you are at risk of developing it, seeking a professional assessment immediately might be life-saving. 

It is also very important for both symptomatic and asymptomatic cases to attend regular follow-ups and follow the advice given by healthcare professionals.

Summary

Coronary artery aneurysm is the widening of a coronary artery beyond its normal limits, and it is an uncommon but potentially serious condition that might result in fatal complications such as clot formation and vessel rupture. 

There are many causes of coronary artery aneurysms. However, the most common ones are atherosclerosis and Kawasaki disease in adults and children, respectively.

Despite the fact that most coronary artery aneurysms present without a symptom, symptoms can be present in some cases depending on the underlying cause.

Coronary angiography is used as the gold standard for diagnosis, and treatment is based on individual cases; however, it's always advisable to consult with a healthcare professional for an accurate diagnosis and appropriate treatment options for coronary aneurysms.