What is Coronary Artery Fistula?
Coronary artery fistulas are uncommon issues with the heart’s blood circulation system. These defects, which could be either present from birth or develop later, cause abnormal formation and pathways in the coronary arteries or heart blood vessels. These fistulas fall in two main categories.
The first, coronary-cameral fistulas, are unusual links between the heart’s blood vessels and any of its chambers. The second, coronary arteriovenous malformations, involve abnormal connections between the coronary arteries and the vessels for the body’s or lung’s circulation.
Most of the time, these coronary artery fistulas are discovered by chance during heart imaging. However, some of the people with this condition may experience signs and symptoms of heart failure, heart attack, high blood pressure in the lungs, and other heart and lung function issues.
Diagnosing this issue is usually reliable using a heart imaging test called coronary angiography, and another test called coronary computerized tomography angiography (CTA). Once diagnosed, the usual treatment involves a procedure to close the fistula using a catheter.
What Causes Coronary Artery Fistula?
The main reasons behind coronary artery fistulas are threefold. The most frequent cause is a natural birth abnormality due to irregular development in the womb. Another source often comes from physical injuries, like gunshot or stab wounds. Lastly, medical procedures involving the heart, like bypass surgery, heart scans, valve replacements, device installations, or tissue sample collections, can sometimes lead to coronary artery fistulas.
Risk Factors and Frequency for Coronary Artery Fistula
Studies on coronary artery fistulas, which are abnormal connections between the coronary arteries and other heart parts, have increased. In one such study, these fistulas were found to affect 0.9% of the population, a significant increase from the earlier estimated prevalence of 0.05% to 0.25%. This increase can be attributed to the greater use of coronary CT angiography, an imaging procedure that provides detailed pictures of the heart and blood vessels. The most commonly seen type of malformation involves a connection between a coronary artery and one of the pulmonary arteries.
Signs and Symptoms of Coronary Artery Fistula
A coronary artery fistula is a connection between the coronary artery and a different blood vessel. Each fistula can vary in its symptoms and severity based on its origin, end point, length, and size. Commonly, patients with this condition exhibit no symptoms. Fistulas are typically silent for about twenty years, but once they start significantly affecting blood flow, symptoms can appear. Here are some common scenarios:
- Congenital coronary artery fistulas – In infants around 3-4 months old, a significant coronary artery fistula may result in congestive heart failure. Infants may have a fast heart rate, rapid breathing, and generally seem restless and sweaty. A continuous murmur can often be heard when listening to the heart.
- Asymptomatic adult patients – Most patients with coronary artery fistulas don’t show symptoms for at least a decade or two. Sometimes, a physical exam can detect a continuous heart murmur. These fistulas are often found by accident during a coronary angiogram.
- Myocardial infarction/chronic myocardial ischemia – Coronary artery fistulas can harm the heart muscle by blocking blood flow, causing the areas supplied by these vessels to become ischemic (lack oxygen). Patients might feel typical or atypical chest pain, unrelenting, and doesn’t ease with rest.
- Congestive Heart Failure -Some coronary artery fistulas cause an imbalance of blood flow from the left to the right of the heart, leading to a buildup in the lungs. That may result in symptoms of right-sided heart failure like shortness of breath, difficulty breathing with exertion, difficulty breathing while lying down, or swollen legs.
- Atrial/Ventricular arrhythmias – Fistulas can sometimes cause abnormal heart rhythms by causing low output congestive heart failure. This condition leads to a backup of blood and subsequent enlargement of the atria and/or ventricles.
- Cardiac tamponade – Very rarely, if a coronary artery fistula ruptures, blood can fill the sac around the heart (hemopericardium). Patients may present with shortness of breath, low blood pressure, extensive neck vein distention, and an abnormal pulse.
Testing for Coronary Artery Fistula
To evaluate coronary artery fistulas, doctors begin by listening to the heart sounds in the lower chest area. In the beginning stages of diagnosis, they may use chest X-rays and EKGs (heart rhythm tests). While these tests alone are not enough to diagnose the condition, they can help spot any complications that have arisen. For example, changes in an EKG reading could suggest a heart attack or chronic poor blood supply to the heart. Chest X-rays can show whether there is excess fluid in the lungs.
Transthoracic echocardiograms (TTE), a type of ultrasound test that creates images of the heart, have been shown to identify significant coronary artery fistulas, but they don’t help determine where they start and end. TTEs are generally enough to diagnose the disease in children. Doppler echocardiography, which uses ultrasound waves to measure the speed and direction of blood flow, is useful for identifying enlarged or twisted arteries and mapping out blood flow. Abnormal blood flow into the heart’s chambers can also be seen through Doppler echocardiography.
Transesophageal echocardiograms (TEE) help see turbulent blood flow and detail where the fistulas start and end in adults. Cardiac magnetic resonance imaging, another imaging test, may also be used to better identify these abnormal tubes.
The most reliable way to diagnose coronary artery fistulas is through coronary catheterization and subsequent coronary angiography, where a dye is injected into the heart’s blood vessels to make them visible on an X-ray. Recent studies demonstrate the helpfulness of aortic root angiograms as the first test, to inform the best next steps. The next test involves conducting angiographies on each of the arteries, to find out where the fistulas start and end and estimate the blood flow. In some cases, doctors may turn to retrograde thoracic angiography. Recently, more doctors are shifting to coronary computerized tomography angiography (CTA). These CTAs are non-invasive, and they are even better at detecting coronary artery fistulas compared to the traditional invasive coronary catheterization with angiography.
Treatment Options for Coronary Artery Fistula
Treatment is usually only needed for patients who:
* Have significant unstable blood flow from left to right.
* Have heart failure with an overloaded left ventricle or a non-functioning left ventricle.
* Have a reduced blood supply to the heart muscle.
Previously, doctors used surgery as a way to treat coronary artery fistulas, which are abnormal connections between the coronary arteries and the chambers of the heart or another blood vessel. But lately, a less invasive method using catheters has become the preferred treatment. This technique aims to block off the problematic artery at the most downstream part of the fistula, closest to where it ends. The reason for this is to ensure that blood can still reach tissues supplied by that irregular artery, while at the same time, reducing the undesired blood flow through the fistula. Materials used for the blocking operation, known as embolization, include detachable balloons, or tiny steel or platinum coils.
After the embolization, the doctor will perform a type of X-ray called coronary angiography to make sure the procedure was successful. This scan can also reveal smaller fistulas or extra branches from the fistula that might need attention.
While surgery used to be the go-to method and aimed to close off the affected artery or heart chamber, it had a high chance of the fistula coming back. That’s why the less invasive catheter method is now favored.
After the procedure, patients are usually put on medication to prevent blood clots, such as antiplatelet drugs, and in some cases, anticoagulants as well. They usually need to take these medications for the first six months following the procedure.
What else can Coronary Artery Fistula be?
In cases where a patient shows signs and symptoms related to a condition known as coronary artery fistula, there are several other potential health problems a doctor needs to rule out, including:
- A persistent connection between two major blood vessels near the heart, called patent ductus arteriosus
- An abnormal passageway between an artery and a vein, known as arteriovenous malformation
- An acute phase of heart disease leading to damage in the heart muscle, often known as acute myocardial ischemia
- A condition where the heart doesn’t pump sufficient blood to the body, known as congestive heart failure
- Irregular heartbeat, referred to as arrhythmia
- A serious condition where fluid fills the space around the heart, compressing it, and making it difficult for the heart to pump effectively, called cardiac tamponade
These conditions could also show signs of a stable coronary artery fistula, but the doctor needs to make sure that other, more severe underlying causes are not present. These include a heart attack because of blood clots (also known as myocardial infarction secondary to thrombosis) and heart rhythm problems that start in the lower chambers of the heart, called primary ventricular arrhythmias.
What to expect with Coronary Artery Fistula
The prognosis, or likely course, of coronary artery fistulas largely differs based on several factors. Ultimately, the complications they cause can determine the outcome for patients. Some adults may not experience any symptoms throughout their life if the fistula is not causing any significant changes in blood flow. However, for other patients who develop complications like heart failure, irregular heartbeats, and cardiac tamponade (pressure buildup from fluid in the heart), immediate medical attention is needed.
For these patients, the first step involves treating the complication, followed by closure of the coronary artery fistula using a method called catheterization, all with the aim of reducing morbidity (risk of disease and illness). Even though it’s rare for the fistula to come back after closure, surgery is more likely to result in a recurrence compared to non-surgical closure by catheterization.
Possible Complications When Diagnosed with Coronary Artery Fistula
Coronary artery fistulas often don’t show any symptoms. However, when symptoms do happen, they’re usually due to complications that occur from the fistulas. Here is a list of possible complications:
- Steal syndrome – This is when blood does not flow to the end of the artery as it should because it’s being redirected through the fistula, leading to heart muscle damage due to lack of oxygen.
- Thrombosis/embolism – This can cause a heart attack.
- Volume overload – This can cause heart failure.
- Arrhythmias – Irregular heartbeats
- Rupture – This can cause bleeding into the pericardium (the sac around the heart) and can result in cardiac tamponade, a serious condition where the heart can’t pump properly.
- Endocarditis/endarteritis – Infection of the heart lining and/or the arteries.
Preventing Coronary Artery Fistula
Teaching patients about their condition is crucial. Most people diagnosed with coronary artery fistulas, abnormal connections between heart arteries, don’t show symptoms initially. They often find out about the fistulas unintentionally when undergoing heart tests for other reasons. After the diagnosis, it’s important to explain to patients that these fistulas could start causing symptoms within 20 years or less. Patients should be made aware to watch out for symptoms like chest pain, shortness of breath during exercise, unusual heartbeats, and other heart or lung-related issues. They should have regular check-ups with their family doctor and/or heart specialist. If they notice any of the mentioned symptoms, they should go to the nearest emergency department.
Patients who have had procedures to close these fistulas, either through a catheter or through surgery, should be encouraged to stick to their medication to prevent blood clots, and in some cases, blood thinners. They should also regularly visit their heart specialist for follow-ups.
