Anomalous Left Coronary Artery from the Pulmonary Artery

An anomalous left coronary artery from the pulmonary artery is a rare defect of the blood vessels that provide blood to the heart muscle. It is congenital, meaning it is present at birth, and it is one of the most severe defects of the coronary arteries (the blood vessels that provide blood to the heart muscle).

Anomalous left coronary artery from the pulmonary artery (ALCAPA), also known as Bland-White-Garland Syndrome, is a rare congenital heart defect that affects 1 out of 300,000 births and accounts for 0.25%-0.5% of congenital heart disease. It is usually the only heart defect present but is associated with other cardiac anomalies in 5% of cases.

ALCAPA may present as cardiomyopathy (heart muscle disease) and is one of the most common causes of heart attacks in children.

To understand this condition, we first need to know how the heart works.

How does the heart normally function?

In a normal, healthy heart, blood circulates in a semi-figure-8 pattern. The blood follows this pattern:

  1. The right side of the heart pumps blood to the lungs via a large blood vessel called the pulmonary artery.
  2. The blood picks up oxygen from the lungs.
  3. The blood flows into the left side of the heart.
  4. The left side of the heart pumps the oxygen-rich blood throughout the body through an even larger artery (the aorta) that branches out to provide blood to the entire body.
  5. The first branch of this artery supplies oxygen-rich blood to the heart muscle via small arteries surrounding the outside of the heart. These small arteries are called coronary arteries.
  6. The blood continues throughout the entire body, delivering oxygen and nutrients to the cells and tissues.
  7. The blood, now depleted of oxygen, returns to the right side of the heart.
  8. The heart pumps the oxygen-depleted blood into the lungs.

This cycle repeats all day, every day.

What is the defect?

In an anomalous left coronary artery from the pulmonary artery, the artery supplying blood to the left side of the heart connects to the pulmonary artery instead of the aorta; it is attached to the main blood vessel heading into the lungs before reaching them.

What happens because of the defect?

As a result of the ALCAPA defect, the muscle on the left side of the heart does not have enough blood pressure or oxygen.

The lack of oxygen weakens the heart, and it cannot pump efficiently, which leads to cardiomyopathy (disease of the heart muscle).

Eventually, it can cause a heart attack or heart failure. 90% of infants with this heart defect will die within the first year of life.

10-15% of infants will develop smaller blood vessels in the heart connecting the two bigger blood vessels, called collateral circulation. If enough oxygen-rich blood is shunting from the right side of the heart to the left side, the infant can live into childhood or even adulthood.

A child may not have any symptoms or complications.

They may have varying degrees of heart muscle damage due to a lack of oxygen (ischemic cardiomyopathy).

They may develop problems with the valve between the two chambers on the left side of the heart not closing completely (mitral valve insufficiency).

If the infant survives into adulthood, the defect usually manifests as a heart arrhythmia (irregular heart rhythm).

ALCAPA Symptoms in infants

Symptoms usually begin to appear 1-2 months after birth.

They include:

  • Crying or sweating during feeding
  • Difficulty feeding
  • Rapid respiratory rate
  • Pain or distress, often resembling colic
  • Irritability
  • Excessive sweating
  • Wheezing and difficulty breathing
  • Heart murmur

Infants can also develop a condition known as the "coronary steal phenomenon."

The left side of the heart pumps blood throughout the entire body. The right side of the heart only pumps blood through the lungs; the blood pressure in the artery leading to the lung, the pulmonary artery, is much lower than in the aorta.

Because the pressure in the pulmonary artery is not high enough to pump blood into the left coronary artery effectively, the blood backs up into the pulmonary artery, leading to congestive heart failure (CHF) and significant mitral valve insufficiency, as mentioned above.

Sometimes an infant can grow to be an adult before the symptoms develop.

Symptoms in adults

Symptoms in adults include:

  • Dysrhythmias (irregular heart rhythms)
  • Enlarged heart
  • Fainting with exercise
  • Fatigue
  • Heart attack; or myocardial infarction (MI)
  • Heart palpitations
  • Left ventricular dysfunction (the left side of the heart does not function efficiently)
  • Mitral valve regurgitation: the valve between the left atria (top part of the heart) and the left ventricle (the bottom part of the heart) does not close properly, and some blood leaks backward.
  • Persistent angina (chest pain caused by decreased oxygen to the heart muscle)
  • Shortness of breath with exercise
  • Silent myocardial ischemia (heart muscle damage without symptoms)
  • Ventricular heart arrhythmia
  • Sudden cardiac death

How is this defect diagnosed?

ALCAPA is diagnosed with tests that look at the structure, electrical pathways, and blood flow through the heart's coronary arteries. Tests include a chest x-ray, ECG, CT, MRI, echocardiogram, or angiogram.

Diagnosis in adulthood is rare, and in the event of sudden cardiac death, diagnoses will be through an autopsy.

How is this defect treated?

A surgeon will relocate the left coronary artery from the pulmonary artery to the aorta or create a tunnel to the correct place in the aorta (Takeuchi repair). If the mitral valve needs repairing, your doctor may be able to do both during the same surgery. In severe cases, a heart transplant may be necessary.

Before the surgery, the patient may be placed on medication to help the heart perform better, and they may need to stay on them even after the surgery.

They will also need to see their cardiologist regularly to ensure the heart muscle is healing and the mitral valve function is improving. They will also need to be monitored for arrhythmias later in life.

What is the outlook for this defect?

Outlook for ALCAPA depends on how much collateral circulation forms.

Without treatment, approximately 90% of infants will die within the first year of life; if they survive into adulthood, this defect may cause sudden cardiac death.

Treatment and surgery can normalize the heart muscle and mitral valve function in some cases.

How well the muscle and valve can heal depends on how much damage occurred before the repair and how much scar tissue is present.

Key take-aways

An anomalous left coronary artery from the pulmonary artery is a rare heart defect that affects the coronary arteries.

In this congenital heart defect, the artery that supplies blood to the left side of the heart arises from the pulmonary artery instead of the aorta.

In other words, the left side of the heart is receiving blood with a low oxygen level and lower pressure, leading to backflow of blood and damage to the heart muscle due to lack of oxygen.

The treatment is surgery to reposition the artery onto the aorta.

References:

Oncel, Guray and Oncel1, Dilek (2013). Anomalous Origin of the Left Coronary Artery from the Pulmonary Artery: Diagnosis with CT Angiography. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3625882/

Weerakkody, Y., El-Feky (2020). M. Anomalous left coronary artery from the pulmonary artery. Reference article, Radiopaedia.org. https://doi.org/10.53347/rID-9750

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