What is Coronary Artery Fistula, Know its Causes, Symptoms, Complications and Diagnosis

Coronary artery fistula is a link between several coronary arteries with the great vessel which is technically termed as the cardiac chamber. Fistula stands for the abnormal link between the organ which is usually present by birth or during an accidental surgery. This is a very rare incidence and occurs silently.¹

A coronary artery fistula can affect how well the blood flows to the heart and lead to dilation of the coronary arteries. In some cases, infants who are born with this condition may also have other heart defects. Before we understand what coronary artery fistula is in detail, let us first understand the anatomy of the heart and the coronary arteries and its function.

A coronary artery fistula is often congenital. It is present by birth, as a result of the failure of functional coronary arteries. The feeding artery of the fistula may drain from a main coronary artery or one of its branches and is usually a sinuous and enlarged artery terminating in one of the heart chambers or any of its vessels.

When the fistula drains into the right side of the heart, the load volume is increased to the right side of the heart. When it drains into the left side of the heart, the overload occurs but without an increase in pulmonary blood flow. Hence, the case of a coronary artery fistula draining into the right side of the heart can be more lethal and occasionally, results in cardiac arrest.

The majority of the fistulas have a congenital origin, but may rarely be found out after cardiac surgery, such as valve replacement, artery bypass, cardiac biopsies and other forms of transplantation.

The causes of a coronary artery fistula are:

• An infection that weakens the wall of the coronary artery and heart can lead to the fistula. For example, endocarditis degrades the valves and wall of the heart which can lead to the abnormal attachment of the heart chamber to the coronary artery which carries the oxygenated blood towards the heart.
• Certain types of heart surgery like regular biopsies and heart transplantation can cause coronary artery fistula.
• An injury to the heart caused by any surgery or accident is also one of the reasons that can result in the fistula.²

Most of the patients are asymptomatic in the first few decades especially, when the link is small. After a certain age, complications and symptoms may begin. The fistula may increase in size over time, although this change is variable for different patients.

Some of the noticeable symptoms of coronary artery fistula are:

• Chest pain or discomfort
• Heart murmur which is heard in the mid-chest or even in the lower chest
• Easy fatigue
• Shortness of breath
• Fast or irregular heartbeat
• Slow growth.

Some of the complications of coronary artery fistula are:

• Abnormal heart rhythm
• Heart Attack
• Heart Failure
• Poor oxygen to the heart due to the fistula
• Opening of fistula.

In most cases, the diagnosis of coronary artery fistula is not done until later in life or are found as incidental findings in some. Initial diagnostic angiography is required to access the significance of fistula. The understanding of the presence of coronary artery fistula to provide detailed anatomy including the size, origin, and the course of fistula.

Selective coronary angiography of both coronary arteries, in some case all three coronary arteries, is required to confirm the diagnosis. However, these procedures should take place only when the surgery is planned.

Other tests may include two dimensional and color doppler echocardiography which helps in determining the size of fistula and color flow points the area of drainage, but it is difficult to determine the exact anatomy of fistula through this technique. Magnetic resonance imaging (MRI) can also be helpful to confirm the fistula, as the size of the fistula vessel can be seen. A CAT scan of the heart is also suggested.

In humans and some other animals and birds, the heart is divided into four-chamber- left and right atria and left and right ventricles. Commonly the left ventricle and atria are referred together as left heart whereas right ventricle and atria as a right heart. The blood flow is controlled by valves, which retards the backflow of blood.

The backside of the heart is situated near vertebrae columns and the front part is beneath the rib cage. One disputable fact states that the size of a person’s heart is equivalent to the size of its fist, although the size of the heart is a little bigger. Well trained athletes and high-altitude residents have a much larger heart due to the effect of exercise and daily chores on their heart muscle. The much larger heart allows them to do more work than an average person.

The heart functions as a pump in the circulatory system to provide a continuous flow of blood throughout the body. This circulation consists of systematic circulation to and from the body and the pulmonary circulation to and from the lungs. The normal heartbeat of a person is about 72 BPM. Exercise strengthens the heart muscle and temporarily increases the heart rate but decreases the resting rate which is good for heart’s health.

Coronary arteries are the arteries of the coronary circulation, which is the circulation of blood in the blood vessels that supply the heart muscle. Coronary arteries supply oxygenated blood to the heart muscle. Coronary arteries supply blood to the myocardium and other components of the heart. The blockage of these arteries with cholesterol deposition can increase the risk of a heart attack.

Coronary artery fistula is curable. Children who undergo the surgery for coronary artery fistula mostly do well, although a small percentage may need to undergo the surgery again. Most people with this condition have a normal lifespan and do well in life. Timely diagnosis and appropriate treatment of coronary artery fistula are necessary.

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