Laboratory Studies
Cardiac isoenzymes
Laboratory blood tests are not definitive in the diagnosis of anomalous left coronary artery arising from the pulmonary artery (ALCAPA).
Although elevation of creatine kinase (CK), MB, or troponin occurs following infarction of cardiac muscle, these tests should not be exclusively used for diagnostic purposes.
Electrocardiography
Twelve-lead electrocardiography
Typically, an anterolateral infarct pattern with abnormal deep (>3 mm) and wide (>30 msec) q waves is observed in leads I, aVL, V5, and V6, absent q waves in leads II, III, and aVF, and poor R wave progression across the precordial leads, with sudden shift to qR. Electrocardiography (ECG) detects abnormalities of repolarization in the form of ST-segment depression or inversion, both inferior and lateral (see the image below). The QRS axis is typically normal, although, in some cases, a left superior axis is seen.
Preoperative electrocardiogram in a 2-month-old infant with anomalous origin of the left coronary artery from the pulmonary artery demonstrating pathologic Q waves in leads I and aVL and diffuse ST-T wave changes consistent with an anterolateral infarction.
Following successful surgical revascularization, the ECG may revert to normal findings with the disappearance of the pathologic q waves and ST-T wave changes (see the image below).
Electrocardiogram in 2-month-old infant with anomalous origin of the left coronary artery from the pulmonary artery 17 months following successful surgical revascularization, demonstrating complete resolution of the anterolateral infarction pattern and ST-T wave changes.
Imaging Studies
Chest radiography
Chest radiography usually demonstrates cardiomegaly, with or without pulmonary venous congestion, although this is not diagnostic for anomalous left coronary artery arising from the pulmonary artery (ALCAPA).
Cardiovascular magnetic resonance imaging
Cardiovascular magnetic resonance imaging (CMRI) is a good, noninvasive, radiation-free investigation in the postsurgical evaluation of ALCAPA. In referred patients, basal, anterolateral subendocardial myocardial fibrosis is a characteristic finding. Furthermore, stress adenosine CMRI perfusion, can identify reversible ischemia in this group, and is indicative of left coronary artery occlusion. [12]
Two-dimensional echocardiography with Doppler color flow mapping
This test often is diagnostic and, in some situations, replaces the need for cardiac catheterization and angiography.
Echocardiography without Doppler may identify abnormal origin of the left coronary artery from the main pulmonary artery (see the image below). In unusual circumstances, the anomalous coronary may arise from a branch pulmonary artery, making echocardiographic diagnosis difficult, even with Doppler.
Two-dimensional echocardiographic image (parasternal short axis view) in a patient with anomalous origin of the left coronary artery arising from the pulmonary artery (ALCAPA). The left coronary artery (white arrow) appears to course towards the main pulmonary artery (MPA) just above the pulmonary valve and not to the aortic root (Ao). RV = Right ventricle.
The use of color flow velocity mapping can be diagnostic, demonstrating retrograde flow from the anomalous left coronary into the pulmonary trunk. The retrograde flow into the pulmonary trunk is typically directed in an unusual orientation within the main pulmonary artery (see the image below), distinguishing it from the diagnosis of a patent ductus arteriosus.
Two-dimensional echocardiographic image with color flow mapping (parasternal short axis view) in the same patient with anomalous origin of the left coronary artery arising from the pulmonary artery (ALCAPA). The addition of color flow mapping to the 2-dimensional image demonstrates abnormal flow reversal within the left coronary artery (white arrows) towards the main pulmonary artery (MPA) just above the pulmonary valve. RV = Right ventricle. Ao = Aortic root.
Doppler mapping of an abnormal color flow jet will usually identify abnormal retrograde flow within the main pulmonary artery in both late systole and diastole (see the image below). The mapping image partially depends on pulmonary artery pressure.
Doppler interrogation of the abnormal color flow jet is depicted, demonstrating abnormal flow within the main pulmonary artery towards the transducer in diastole, which represents runoff from the anomalous left coronary artery (large white arrowhead). Small white arrow: Normal antegrade main pulmonary artery flow in systole. MPA = Main pulmonary artery.
The presence of retrograde flow is dependent on the development of collaterals between the left and right coronary artery systems. If collateralization has not occurred, as may be the case with a very early age presentation, this finding may be absent.
Abnormal dilation of the proximal right coronary artery, when present, reflects development of extensive collateralization between the right and left coronary artery systems in those patients who present later in infancy or in childhood.
An additional finding, which is not sensitive but highly specific, is abnormal "brightness" (echogenicity) of left ventricular papillary muscles and sharply delimited sectors of the left ventricular endocardial surface.
Variable degrees of mitral valve regurgitation, left ventricular dysfunction, and wall motion abnormalities may be identified. [13]
Although the echo-Doppler studies are excellent tools in diagnosing ALCAPA, sometimes they may mislead the echocardiographer with seemingly normal origin of left coronary artery. When clinical suspicion of ALCAPA is high, an alternative imaging technique such as cardiac catheterization with angiography or MRI should be performed—even with seemingly “normal” origin of left coronary artery.
Contrast echocardiography of the main pulmonary artery demonstrating negative contrast secondary to flow from the ALCAPA may also be used to diagnose this condition. [14]
Procedures
Cardiac catheterization and angiography
Angiographic evaluation of the coronary artery system should be performed despite a negative echocardiogram if either the clinical history or electrocardiography (ECG) is strongly suggestive. [15]
Hemodynamic measurements are usually consistent with low cardiac output and elevated left atrial pressures secondary to reduced left ventricular compliance or significant mitral valve insufficiency.
Oximetry may show a small left-to-right shunt into the pulmonary arteries.
Aortography or selective right coronary arteriography usually demonstrates an enlarged right coronary artery system with collateralization to the left coronary artery and eventual reflux of contrast into the pulmonary arterial system (see the image below).
Aortogram in a patient with suspected anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA). Frontal (left panel) and lateral (right panel) images demonstrating an enlarged right coronary artery (small white arrow), which fills a small left coronary system (solid arrow head) via collaterals with eventual faint opacification of the main pulmonary artery (not demonstrated in this frame).
If collateralization has not occurred, identification of the anomalous left coronary artery may not be evident by aortography or selective right coronary arteriography.
Stop flow angiography
With a large bolus of contrast under high pressure, an alternative approach is to perform a balloon occlusion angiogram within the distal main pulmonary artery, which retrogradely should fill the anomalous left coronary artery (see the image below).
Main pulmonary artery angiogram demonstrating the technique of stop flow angiography. There is retrograde opacification of the entire left coronary artery system, which originates from the distal main pulmonary artery (MPA), including the anterior descending (solid white arrowhead) and circumflex (small white arrow) branches. Left panel: Frontal image. Right panel: Lateral image.
Although rare, false-negative results with this technique may be caused by incomplete occlusion of the main pulmonary artery or by balloon malposition. A balloon positioned in the proximal main pulmonary artery may occlude the orifice of the anomalous left coronary. Alternatively, if the anomalous left coronary artery arises from the left pulmonary artery, positioning the balloon in the distal main pulmonary artery may prevent contrast from entering the coronary artery. [16]
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Preoperative electrocardiogram in a 2-month-old infant with anomalous origin of the left coronary artery from the pulmonary artery demonstrating pathologic Q waves in leads I and aVL and diffuse ST-T wave changes consistent with an anterolateral infarction.
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Electrocardiogram in 2-month-old infant with anomalous origin of the left coronary artery from the pulmonary artery 17 months following successful surgical revascularization, demonstrating complete resolution of the anterolateral infarction pattern and ST-T wave changes.
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Two-dimensional echocardiographic image (parasternal short axis view) in a patient with anomalous origin of the left coronary artery arising from the pulmonary artery (ALCAPA). The left coronary artery (white arrow) appears to course towards the main pulmonary artery (MPA) just above the pulmonary valve and not to the aortic root (Ao). RV = Right ventricle.
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Two-dimensional echocardiographic image with color flow mapping (parasternal short axis view) in the same patient with anomalous origin of the left coronary artery arising from the pulmonary artery (ALCAPA). The addition of color flow mapping to the 2-dimensional image demonstrates abnormal flow reversal within the left coronary artery (white arrows) towards the main pulmonary artery (MPA) just above the pulmonary valve. RV = Right ventricle. Ao = Aortic root.
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Doppler interrogation of the abnormal color flow jet is depicted, demonstrating abnormal flow within the main pulmonary artery towards the transducer in diastole, which represents runoff from the anomalous left coronary artery (large white arrowhead). Small white arrow: Normal antegrade main pulmonary artery flow in systole. MPA = Main pulmonary artery.
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Aortogram in a patient with suspected anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA). Frontal (left panel) and lateral (right panel) images demonstrating an enlarged right coronary artery (small white arrow), which fills a small left coronary system (solid arrow head) via collaterals with eventual faint opacification of the main pulmonary artery (not demonstrated in this frame).
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Main pulmonary artery angiogram demonstrating the technique of stop flow angiography. There is retrograde opacification of the entire left coronary artery system, which originates from the distal main pulmonary artery (MPA), including the anterior descending (solid white arrowhead) and circumflex (small white arrow) branches. Left panel: Frontal image. Right panel: Lateral image.
