ALCAPA syndrome

ALCAPA syndrome (Anomalous Left Coronary Artery from the Pulmonary Artery), also known as Bland-White-Garland syndrome, is a very rare congenital heart defect (approx. 0.5 % of all congenital heart defects) in which the left coronary artery originates from the pulmonary artery instead of the aorta.

This has two consequences: In the first few weeks of life, the pressure in the pulmonary artery drops in all babies. The pressure in the pulmonary artery is then much lower than in the aorta, from which the coronary vessels normally originate. In children with ALCAPA syndrome, this often means that at the age of a few weeks to months, there is no longer enough blood in the left coronary artery to supply the heart muscle. This undersupply then manifests itself as heart failure.

In addition, only deoxygenated blood flows in the pulmonary artery, which is transported from the body towards the lungs. As a result, the coronary artery that is failing also only receives deoxygenated blood and not oxygen-rich blood as usual. This further increases the undersupply of the heart muscle. An undersupply of oxygen to the heart muscle (ischaemia) can lead to a considerable reduction in function and, if this oxygen deficiency persists for a long time, to irreversible destruction of the heart muscle (infarction).

The left coronary artery supplies the left ventricle, which pumps oxygen-rich blood into the body via the main artery. Heart failure in this area is therefore particularly critical. Patients' symptoms vary depending on the connections (collaterals) to the right coronary artery, which arises from the aorta. For example, significant symptoms can occur as early as a few weeks of life, when pulmonary vascular resistance drops. In other patients with a good collateral supply, however, ALCAPA syndrome can go unnoticed for a long time.

In ALCAPA syndrome, the left coronary artery is malformed early in the development of the child in the womb. The reasons for this maldevelopment are not fully understood. However, it is assumed that many different factors and environmental influences play a role. ALCAPA syndrome usually occurs as an isolated heart defect, which means that there are rarely accompanying malformations in the heart. However, due to the limited function of the left ventricle, there is often also variable leakage of the mitral valve.

As described, ALCAPA syndrome leads to an undersupply of blood to the left ventricle, which usually becomes noticeable in the first weeks to months of life. The left ventricle can then no longer pump enough blood from the lungs into the body. The children show symptoms of cardiac insufficiency with rapid breathing, sweating, rapid fatigue and reluctance to drink. Reduced pumping function with a large left ventricle often also prevents the mitral valve, which separates the left atrium from the left ventricle, from closing. A leak in the mitral valve can exacerbate the symptoms.

In exceptional cases, the heart defect may only become noticeable later, sometimes even in adulthood, if the collateral supply is very good (vascular connections from the normally originating right coronary artery to the incorrectly originating left coronary artery). In these patients, there is a particular risk of cardiac arrhythmia, which can lead to sudden cardiac death. The heart defect should therefore be corrected at any age, even if there are few symptoms.

Depending on how well developed the collateral supply is, your child will develop symptoms sooner or later. If there are hardly any collaterals, symptoms of heart failure may occur shortly after birth or during the first few months of life (when the pulmonary vascular resistance falls). These include rapid fatigue, sweating or breathlessness. If the pumping function is severely restricted, this can quickly lead to a life-threatening situation if the heart is barely able to pump blood into the body to supply the organs (‘low cardiac output’).

However, if the collateral vessels are very well developed, the symptoms may not manifest themselves until later, in rare cases even in adulthood. However, even with a good collateral supply, these patients do not have a normal, sufficient blood supply to the heart muscle, which means that there is a risk of cardiac arrhythmia and sudden cardiac death if left untreated.

An insufficient supply to the left coronary artery can also lead to a significant leak in the left-sided AV valve (mitral valve). This leakage can cause blood to back up into the lungs, which can lead to pulmonary hypertension and heart failure. This manifests itself in breathlessness, considerable exercise limitation and increased respiratory infections. Significant thinning of the heart wall (aneurysm) due to the loss of heart muscle is also possible. Dangerous cardiac arrhythmias can also occur due to the lack of oxygen supply to the conduction system.

An operation should therefore be performed as soon as the diagnosis is made.

ALCAPA syndrome is usually treated with a so-called "coronary transfer ’. This involves transferring the incorrectly originating left coronary artery from the pulmonary artery to the aorta. The procedure is performed after opening the sternum using a heart-lung machine and in cardiac arrest. The left coronary artery is cut out of the pulmonary artery at its origin with a small margin for suturing. The vessel is then carefully detached from the tissue to make it more mobile. It is important that there is no traction on the vessel, as otherwise parts of the heart may again be deprived of oxygen. The coronary artery is then sutured back into place at a suitable point in the aorta. The resulting ‘hole’ in the pulmonary artery is closed with a small patch made from the patient's own pericardium. There is usually already a mild to moderate leak in the mitral valve at the time of the operation. A slight leak usually improves after the operation due to the improved oxygen supply. However, if the leak is severe, it may be necessary to repair the mitral valve during the same operation.

If the pumping function of the left ventricle is already significantly impaired before the operation due to chronic oxygen deprivation (LVEF < 35%), the left ventricle may initially suffer from persistent functional impairment even if the operation is successful. In some cases, the heart initially requires support through the use of a mechanical circulatory support system. However, in most cases this can be removed after the heart has recovered sufficiently and pumping function has been restored.

As ALCAPA syndrome is a very rare congenital heart defect and the repositioning of the coronary artery must be technically flawless for successful treatment, patients should be treated in centres with a high level of expertise. At the DHZC, we have a great deal of experience in treating children and adults with ALCAPA syndrome. As we also transfer the coronary arteries in other heart defects from the neonatal period and also in difficult conditions (coronary anomalies), we carry out these ‘coronary transfers’ regularly and with very good results. This routine for such a rare and complex heart defect is noticeable in the very good post-operative course of our patients.

If a timely correction with repositioning of the left coronary artery to the aorta was possible without significant functional impairment of the left ventricle, normal exercise is generally possible after hospitalisation and an appropriate recovery period. In most cases, minor to moderate mitral valve leakage existing at the time of the operation is tolerated, as this usually recovers over time. However, this takes some time, which means that performance may initially be impaired after the operation due to this valve leakage. The sternum, which we have to cut longitudinally during this operation, usually takes around 4-6 weeks to heal completely and become stable again. After this, there is basically nothing to prevent normal exercise.