What is Major Aortopulmonary Collateral Arteries?
Major aortopulmonary collateral arteries, or MAPCAs, are birth defects affecting the heart. They form due to enduring connections from when a person was an embryo between the aorta (the main artery carrying blood from the heart to the rest of the body) or its branches, and the system of blood vessels in the lungs. MAPCAs are often seen in combination with other heart defects that block or partially block the flow of blood to the lungs.
These unusual connections from the main body (systemic) arteries to the lung (pulmonary) arteries enable the necessary blood flow to the lungs, supporting life in such circumstances. MAPCAs are very uncommon. Some research suggests that a specific scenario – where there’s closure of the lung artery (pulmonary atresia), a hole in the wall separating the heart’s lower chambers (ventricular septal defect), and MAPCAs present – happens in about 10 out of every 100,000 live births.
What Causes Major Aortopulmonary Collateral Arteries?
MAPCAs, which are extra blood vessels, start to form when a baby is still growing inside the womb. Normally, these vessels should disappear once the proper lung circulation develops. However, sometimes the lung arteries don’t grow like they should in certain heart defects present at birth. When this happens, these extra vessels keep growing and in some cases, they become the main source of blood for the lungs.
This condition is often seen with congenital heart diseases that cause low blood flow to the lungs, such as a certain type of heart condition called tetralogy of Fallot with pulmonary atresia. However, it can also sometimes occur on its own, although that’s rare. When it happens on its own, it’s referred to as an isolated aortopulmonary collateral artery and can lead to heart failure in newborns.
Different genetic conditions are thought to play a role in the development of MAPCAs. DiGeorge syndrome is a genetic disorder often linked with the development of MAPCAs, as are VATER syndrome (which affects the spine, anus, windpipe, food pipe, and kidneys) and Alagille syndrome. Children with MAPCAs because of Alagille syndrome usually have a poor outcome, mainly due to the effects on multiple organs.
Risk Factors and Frequency for Major Aortopulmonary Collateral Arteries
PA/VSD/MAPCAs is a complicated heart condition present at birth, showing up in around 10 out of every 100,000 live births. It affects both males and females equally. However, currently, we don’t have enough information to know if it affects some ethnic groups more than others. But it’s worth noting that about 40% of those with 22q11 deletion or DiGeorge syndrome also have MAPCAs.
Signs and Symptoms of Major Aortopulmonary Collateral Arteries
People with conditions involving duct-dependent pulmonary circulation and confluent pulmonary arteries can display a wide range of symptoms. Some may experience cyanosis (a blue or purple coloration of the skin due to low oxygen) after birth as their ductus (a blood vessel in the heart) closes up. This may require an emergency treatment known as prostaglandin resuscitation if the condition was not identified before birth.
On the other hand, those whose pulmonary circulation depends on Multiple Aorto Pulmonary Collateral Arteries (MAPCAs) and have a closed ductus arteriosus might not show any symptoms at birth because of the normal blood flow. However, as the baby grows and becomes more active, they may also develop cyanosis because their blood flow can’t keep up with their growing body’s demands.
Symptoms can be quite variable. Some newborns may exhibit signs of pulmonary overcirculation (too much blood flowing to the lungs) and congestive heart failure. Keep in mind that MAPCAs rarely occur in isolation. They usually come with various other heart and non-heart-related birth defects. Because of this, patients with MAPCAs can have a wide variety of issues related to their pulmonary blood flow, ranging from severe deficiency to excessive high.
Patients with duct-dependent pulmonary circulation and confluent pulmonary arteries often experience cyanotic spells due to reduced blood flow to their bodies or increased blood flow to their lungs. If undiagnosed, this condition might lead to complications such as polycythemia (an overproduction of red blood cells), clubbing (a deformity of the fingers and fingernails), and even recurrent infections or stroke in severe cases.
- Rapid breathing
- Rapid heart rate
- Irritability
- Excessive crying
- Intercostal and subcostal retractions (Inward movement of the muscles between the ribs or below the ribs during inhalation)
When listening to the chest with a stethoscope, a loud P2 heart sound or harsh continuous murmur might be heard, which may vary depending on the accompanying birth defect (like VSD or PDA).
Testing for Major Aortopulmonary Collateral Arteries
MAPCAs, or Major Aortopulmonary Collateral Arteries, are vessels that originate from the aorta and supply blood to the lungs. They are typically divided into three types based on where they originate from: Type I springs from the main branches of the aorta such as the subclavian (near the shoulder) and celiac (near the stomach). Type II originates from the bronchial artery, which supplies blood to the lungs and surrounding areas. Type III directly stems from the aorta itself. MAPCAs can also sprout from the coronary arteries, which supply blood to the heart.
All these can be detected and examined more closely through different types of tests. These tests help doctors understand how blood is flowing in the lungs, spot any abnormalities, plan surgeries, and monitor how patients are doing after a surgery. In this way, the tests assist in improving patient care and making treatments more effective.
Cardiac Catheterization, a procedure that involves inserting a long, thin tube into a blood vessel in your arm, neck, or groin and threading it to your heart, is extensively used to spot clot formations and narrowing in vessels. The structure and connections of all these MAPCAs are usually identified during the first procedure.
The doctor must carefully look for the unique “seagull” shape of the pulmonary arteries (the main passageways to your lungs) in these tests. The right and left pulmonary arteries resemble the wings of a seagull, and the main pulmonary artery looks like the bird’s body and head. The major task for the doctor in this situation is to identify a thin branch that’s as thin as 1 to 2 mm.
Depending on the case, other crucial facts must also be identified. The multiple blood vessel connections in each of the 18 to 20 bronchopulmonary segments (parts of the lungs) must be established. This can be very complex and requires careful analysis as it’s crucial for the surgery.
Cardiac catheterization also gives important information on how blood is flowing in the vessels. For instance, measuring the blood pressure in MAPCAs and estimating the pressure in the right ventricle (the lower right chamber of your heart) is important in determining the success of the overall treatment approach.
Echocardiography, a test that uses sound waves to create pictures of your heart’s chambers is also valuable. Although it helps in detailing the inside structure of your heart, it alone cannot detect MAPCAs. A procedure like cardiac catheterization is more accurate in such cases. However, echocardiography can help doctors spot unusual blood flow in pulmonary veins and atypical coronary anatomies.
Computed Tomography (CT), a test that uses x-rays to create detailed images of your body is beneficial in visualizing the complicated blood vessels of the lungs before any surgeries. Similarly, Magnetic Resonance Imaging (MRI), a test that uses strong magnets and radio waves to create pictures of your body, is increasingly seen as helpful for diagnosing complex MAPCAs. However, both CT and MRI cannot measure the pressure within the blood vessels and heart chambers.
Chest Radiographs or chest x-rays are commonly used to spot changes in your lungs and heart. In the early stages, they typically show an enlarged heart with much blood flow to the lungs. Over time, they can also reveal some lung segments receiving too much blood flow and others receiving too little.
Electrocardiography, a test which measures the electrical signals that coordinate your heartbeats, generally appears normal at birth but can show signs of the right side of the heart working too hard over time. Finally, Pulse Oximetry, a test that measures the oxygen level in your blood, is helpful in assessing the balance between blood flow in the lungs and the rest of the body. This is particularly significant in children with many MAPCAs that may cause heart failure.
Treatment Options for Major Aortopulmonary Collateral Arteries
The best surgical plan for individuals depends on many important factors. These include the size and layout of blood vessels in and around the heart and lungs, the patient’s overall health, weight, age, and any past surgeries. By thoroughly examining each patient’s unique circumstances, doctors can come up with a personalized surgical plan that will give the best chance of a successful outcome. This approach is particularly necessary when dealing with congenital heart defects that involve major aortopulmonary collateral arteries (MAPCAs).
Recent studies show that being a newborn and having a low body weight can negatively affect outcomes, while closing a hole in the heart (called a ventricular septal defect) during the same surgery or in a separate surgery can improve outcomes. Equally, patients with chromosome 22q11 deletion appeared to have their survival affected.
Typically, MAPCAs can be sorted into three main categories. The first two categories make up 75% of cases and include scenarios where the blood supply comes mainly from the ductus arteriosus. The remaining 25% of cases come with complications and depend on MAPCAs for their blood supply to the lungs. These cases are more challenging to manage since these arteries are essential for blood flow in the lungs, while others may not be necessary.
Surgery is a common treatment option. Two ways to estimate confluence (the degree to which the arteries merge) in MAPCAs are the McGoon ratio and the Nakata index. The Nakata index calculates the size of the arteries in the lungs relative to the size of the patient’s body. This index helps doctors decide whether major surgery (unifocalization) would lead to positive results. If the central pulmonary arteries are small, it might be beneficial to enlarge them by directly connecting them to the heart (right ventricle) with a conduit (a pipe-like structure). A study which tracked over 1000 patients from 1964 to 2001 found that conduits that don’t have valves tend to last longer.
Another surgical technique that can be used is called unifocalization, which aims to streamline the blood flow to the lungs. To help normalize the pressure and flow of blood in the heart and lungs, all lung areas must receive adequate blood flow.
In some cases, interventional catheterization might be necessary. This procedure involves inserting a long tube into a blood vessel to either close off duplicate blood vessels or widen narrow ones. These narrow vessels can exist within the pulmonary arteries or after unifocalization surgery.
While surgery is common for correcting heart defects with MAPCAs, medication plays a minor role, often providing short-term relief. If the MAPCAs are dependent on the ductus arteriosus, a drug, prostaglandin E1 infusion, may be used to keep it open. Although, it is not recommended to use long-term prophylactic β-blocker to manage severe cyanosis. Medication like Phenylephrine can temporarily manage severe cyanosis but should be used with caution especially prior to a surgery.
What else can Major Aortopulmonary Collateral Arteries be?
MAPCAs, or Major Aortopulmonary Collateral Arteries, are complex blood vessel structures often found in individuals born with certain heart defects. These formations usually occur when there isn’t enough blood flow to the lungs. When diagnosing MAPCAs, physicians take into account several other heart conditions that might have similar symptoms or could complicate the diagnosis.
The following conditions need to be considered:
- Pulmonary atresia with VSD: This is often linked with MAPCAs. This condition involves development of these collateral arteries as a way to supply blood flow to the lungs when the pulmonary valve is not open.
- Tetralogy of Fallot with absent pulmonary valve: Here, the underdevelopment or absence of the pulmonary valve can cause the pulmonary arteries to balloon and even though MAPCAs are not a primary symptom, the unusual pulmonary arterial anatomy could suggest a similar appearance.
- Truncus arteriosus: This condition entails a single trunk artery that arises from the heart supplying the pulmonary, systemic, and coronary circulations, different from MAPCAs where multiple separate collateral arteries develop from the aorta or its major branches.
- Complex single ventricle defects: Patients with single ventricle conditions may have various conduits or shunts placed that could be misinterpreted as MAPCAs on imaging studies. Comprehensive imaging and patient history are vital for distinguishing these surgically modified circulations from naturally formed collateral networks.
- Congenital or Acquired Pulmonary Artery Stenosis: Obstruction of the pulmonary arteries may lead to development of a collateral circulation similar to MAPCAs. The main difference lies in which arteries are primarily involved.
- Williams Syndrome: This disorder can produce heart abnormalities causing hemodynamic effects similar to those seen in MAPCAs.
Clinicians diagnosing MAPCAs should carry out detailed assessments with echocardiography, cardiac MRI, and sometimes cardiac catheterization. These investigations help to understand the extent of the collateral network, the functionality of the pulmonary circulation, and distinguish MAPCAs from other conditions. Accurate identification of the underlying condition is crucial for planning the right treatments, including unifocalization of collaterals, repair of associated defects, or, in certain cases, transplantation.
What to expect with Major Aortopulmonary Collateral Arteries
A recent study at Lucille Packard Children’s Hospital (LPCH) at Stanford University looked at a large number of cases where 780 individual patients underwent surgery. Initially, the number of new patients remained pretty steady for the first 15 years, but then it significantly increased. Interestingly, nearly 40% of patients already had surgery prior to coming to LPCH, and this pattern seems to be increasing in frequency lately.
Successful repair was accomplished in 704 patients, which is 90% of the total. Out of those, 67% managed to achieve this success during their initial surgery at LPCH.
Now let’s talk about some statistics related to heart pressure: the median pressure between the right ventricle (part of the heart) and the aorta (main artery) was 0.34, ranging between 0.28 and 0.40.
Also, the overall incidence of patient mortality (or death) within 10 years was about 15%. Interestingly, no significant differences were noted based on when the surgeries were performed.
Some factors, identified through advanced statistical models, were associated with a higher risk of death. Such factors include having Alagille syndrome (a genetic disorder affecting the liver and heart), needing respiratory support before surgery, and receiving a palliative surgery (aimed at relieving symptoms, but not curing disease) as the first surgery at the center.
Despite increasing surgical volumes and more patients having previous surgeries, the LPCH’s pulmonary artery reconstruction program, which treats conditions like narrowing or blockage of the pulmonary arteries, has continually improved patient outcomes.
Possible Complications When Diagnosed with Major Aortopulmonary Collateral Arteries
Major Aortopulmonary Collateral Arteries (MAPCAs) usually occur alongside other heart defects that an infant may be born with. If not treated, they can result in various serious health issues:
- Pulmonary overcirculation: This condition involves too much blood flowing to the lungs, which can cause fluid buildup in the lungs (pulmonary congestion) and high blood pressure in the lung’s arteries (pulmonary hypertension).
- Heart failure: If the blood pressure in the lungs’ vessels increases too much, the heart has to work extra hard to pump blood. This strain can eventually lead to heart failure.
- Ventilation-perfusion mismatch: Normal lung arteries evenly distribute blood. However, MAPCAs distribute blood unevenly; some lung parts can receive too much blood, and others might not get enough. Over time, this can cause lung damage and cyanosis, a condition that turns your lips, skin, or nails blue.
- Increased risk of infections: Unusual blood flow, coupled with the fluid buildup in the lungs, can raise the chances of respiratory infections.
- Hemoptysis: Sometimes, these abnormal arteries can rupture and bleed into the lungs.
Preventing Major Aortopulmonary Collateral Arteries
A diagnosis of congenital heart disease (CHD), or a birth defect of the heart, can understandably cause a lot of worry and stress for parents. Besides their child’s health and survival, parents often worry about how CHD will affect their child’s ability to learn and function in the future. Recent studies have indeed noted that children with CHD may face more challenges in education compared to other children.
A recent European study reported that only about 85.4% of children with CHD attend regular schools, which is less than the 97% attendance rate for other children in Switzerland. Similar findings have been recorded in Germany, with a smaller proportion of children with CHD in regular schools compared to the general population. Notably, they also found that children with heart defects who are in regular schools often need more educational support, such as repeating grades or a second year of kindergarten.
Despite these challenges, it’s important to note that children with CHD aren’t just defined by their health condition – they’re active and involved in their communities too. The study reported that these children, like their peers, enjoy leisure activities such as sports, social clubs like scouts, or playing musical instruments. The participation rate in sports is particularly encouraging, as it matches that of the general population of Swiss children.
