Keywords ALCAPA - cardiac MRI - PAH - perfusion abnormality
Introduction
Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) syndrome, also known as Bland–White–Garland syndrome, is a rare congenital abnormality accounting for 0.25 to 0.5% of all congenital heart diseases.[1 ]
[2 ] It has two types, infant and adult types, each with different clinical manifestations and prognosis. Computed tomography coronary angiogram (CTCAG) provides accurate, noninvasive imaging of this condition. However, they can present with atypical clinical features mimicking dilated cardiomyopathy. Here, we report an adult type of ALCAPA syndrome presenting as dilated cardiomyopathy with pulmonary hypertension on echocardiography. Cardiac magnetic resonance imaging (CMR) was able to establish ischemia as the cause of dilated cardiomyopathy and suspect ALCAPA due to ischemia from the perfusion abnormalities and late gadolinium enhancement.
Case Report
A 22-year-old gentleman presented with exertional dyspnea for 2 years. There was no history of chest pain, palpitation, limb edema, orthopnea, or paroxysmal nocturnal dyspnea. Two-dimensional (2D) echocardiography showed a dilated left ventricle with good systolic function (left ventricular ejection fraction of 54%) with no wall motion abnormalities. Moderate mitral regurgitation (MR) and severe pulmonary artery hypertension (PAH) were present. CMR (Siemens, 1.5-T, Avanto, Erlangen, Germany) done to rule out early dilated cardiomyopathy revealed dilated left atrium and left ventricle ([Fig. 1A ]) with MR. Subendocardial late gadolinium enhancement (LGE) was seen in the mid-anteroseptal, anterolateral, inferolateral, and apical segments, suggesting subendocardial infarcts in the left anterior descending (LAD) artery territory ([Fig. 1B–F ]). The perfusion scan showed enhancement of the lateral wall of the left ventricle before the contrast pool reached the left ventricular cavity ([Fig. 1B–D ]; [Video 1 ]). The LAD artery was visualized before the blood pool reached the left ventricular cavity ([Fig. 1B ]). This atypical pattern of perfusion anomaly raised suspicion for abnormal origin of coronary artery from pulmonary circulation.
Fig. 1 (A ) Cardiac magnetic resonance cine four-chamber view showing a dilated left atrium and left ventricle. (B–D ) Short axis perfusion images showing visualization of the left anterior descending artery (arrow in B ) before contrast in the left ventricular cavity. The left ventricular lateral wall shows early enhancement (arrow in C ). There are subendocardial perfusion defects in the mid-anteroseptal and anterolateral segments (D ). Late gadolinium enhancement (E ) four-chamber and (F ) long axis images show left ventricular subendocardial enhancement in lateral segments (arrow ).
Video 1 Static perfusion short axis images showing the perfusion in the anterolateral wall prior to the contrast appearing in the left ventricular cavity.
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CT angiogram (Philips, Brilliance, iCT 256) showed a dilated main pulmonary artery (MPA) of 32 mm with the left main coronary artery (LMCA) arising from the right lateral aspect of MPA, 4 cm above the pulmonary annulus ([Fig. 2B–D ]). The LAD artery and Left circumflex artery (LCX) were normal with no stenosis. Focal calcification was noted in the left ventricular lateral wall and apical regions secondary to subendocardial ischemia ([Fig. 2A ]). Invasive coronary angiogram demonstrated left coronary system filling from the right coronary artery (RCA) via intercoronary collateral vessel ([Fig. 2A, B ]) and retrogradely opacifying the MPA in diastole with antegrade flow in systole ([Video 2 ]).
Fig. 2 (A ) Noncontrast computed tomography (CT) showing subendocardial calcifications in left ventricular lateral wall and apex (arrow ). The left coronary shows anomalous from the main pulmonary artery from the (B ) right lateral aspect (arrow ) with (C, D ) ostio-proximal angulation (arrows ) in the CT angiogram. (E, F ) Coronary angiogram of the right coronary artery showing retrograde filling of left anterior descending artery from the intercoronary collateral vessel with bidirectional flow (arrow ) better appreciable in [Video 2 ].
Video 2 Right coronary angiogram shows retrograde filling of the left anterior descending (LAD) artery from the right coronal artery with bidirectional flow in the pulmonary artery from the LAD.
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The patient was treated surgically with LMCA ligation and coronary artery bypass with a single saphenous venous graft to the mid-LAD artery. The postoperative course and recovery in the hospital was uneventful.
Discussion
ALCAPA syndrome is a rare congenital coronary anomaly. The basic pathophysiology of ALCAPA syndrome is the “coronary steal” phenomenon, in which a left-to-right shunt leads to abnormal left ventricular perfusion. ALCAPA is of two types: infant type and adult type. Infants usually present around 8 weeks after birth with failure to thrive, profuse sweating, dyspnea, and pallor. If left untreated, up to 90% of patients with ALCAPA die within the first year of life.[3 ] The extent of acquired collateral circulation between the RCA and left coronary artery (LCA) is less in this group, leading to myocardial ischemia and infarction once the pulmonary artery pressure falls during the neonatal period.
In the adult type ALCAPA, patients may present with mitral insufficiency, ischemic cardiomyopathy, or malignant dysrhythmias, which lead to sudden death.[4 ] This group of patients have well-established collateral vessels between the RCA and the LCA but often these are not sufficient to supply the left ventricle, leading to chronic left ventricular subendocardial ischemia and malignant ventricular dysrhythmias, with a risk of sudden cardiac death occurring in 80 to 90% of cases.[3 ]
[5 ] Electrocardiogram-gated multidetector CT angiography and magnetic resonance imaging are valuable noninvasive modalities that can be used to diagnose ALCAPA. CT angiography with excellent spatial resolution is used to delineate the coronary anatomy and assess for collaterals and postoperative follow-up. CMR using the cine, perfusion, and LGE sequences helps assess the extent of left ventricular myocardial infarction, wall motion abnormalities, mitral valve impairment, and degree of left-to-right shunt.
Direct visualization of the LCA arising from the MPA is the diagnostic hallmark of the ALCAPA syndrome, seen in approximately 90% of cases.[6 ] The retrograde flow from the LCA to the MPA, when seen on magnetic resonance images, is a characteristic finding of the steal phenomenon and appears as a jet entering the MPA on Steady state free precession cine images.[7 ] However, in patients who develop PAH due to long-standing left-to-right shunt, the reversal of shunt may happen with early filling of the LAD artery in the right ventricular phase of magnetic resonance perfusion imaging, as seen in our case. The perfusion of the left ventricular lateral wall before the contrast reaches the left ventricular cavity is a clue to the development of PAH with retrograde flow into the myocardium from the pulmonary circulation. In addition, diffuse contiguous delayed subendocardial enhancement in multiple vascular territories seen on LGE indicative of subendocardial infarction is an important clue to suspect ALCAPA in patients with dilated cardiomyopathy. This finding in adult asymptomatic or incidentally detected ALCAPA patients is critical as it predicts the onset of malignant dysrhythmias leading to sudden cardiac death and requires surgery.[8 ] Subendocardial calcifications in the left ventricular and posterior mitral leaflet may develop as a sequela of chronic subendocardial infarctions.
Restoration of a dual-coronary-artery system is the ideal surgical treatment for the ALCAPA syndrome.[9 ] The surgical approaches include coronary button transfer, the Takeuchi procedure (transpulmonary baffling), and placement of the coronary artery bypass graft combined with ligation of the origin of the LCA. In adults, the latter method is preferred.[5 ] Endovascular treatment using percutaneous transcatheter closure of the ALCAPA is another described treatment option.[10 ]
In young adults with suspected dilated cardiomyopathy, CMR findings of early coronary and myocardial opacification with diffuse subendocardial LGE and subendocardial calcifications in the left ventricle could indicate ALCAPA with PAH.
