Anomalous Origin of the Left Coronary Artery from theRight Pulmonary Artery Presenting Following Relief ofLeft Heart Obstruction: A Distinct and PredictableClinico-Pathological Syndromechd_357 327..330

Gareth Morgan, Mphil,* Christopher Caldarone, MD,* Robert Anderson, MD,† andRajiv Chaturvedi, PhD*

*Hospital for Sick Children—Labatt Family Heart Centre, Toronto Canada; ‡University College London—Institute of ChildHealth, London, UK

A B S T R A C T

Introduction. Pre-operative recognition of significant abnormalities of the coronary arteries is important in a varietyof congenital cardiac conditions. Failure to diagnose anomalous origin of the coronary artery from the pulmonaryartery during repair of other anomalies is important because reduction in pulmonary artery pressure will reducemyocardial perfusion pressure.Patients. We report two cases of the rare association of anomalous origin of the left coronary artery from the rightpulmonary artery, aortic coarctation, and mitral stenosis.Conclusions. Definitive imaging of coronary artery anatomy by echocardiography or other modalities should form aroutine part of diagnostic assessment in all congenital heart disease patients but particularly those with left heartobstruction.

Key Words. Coronary Artery; ALCAPA; Ischemia; Left Heart Obstruction

Introduction

The association of anomalous origin of theleft coronary artery from the pulmonary

trunk with aortic coarctation is uncommon butwell recognized.1,2 Clinical presentation of thecoronary problem in this group of patients variesmainly with the degree of pulmonary venous andarterial hypertension, which influences the abilityof the pulmonary circulation to perfuse the myo-cardium. The mechanism by which the pulmo-nary arterial pressures are maintained may be acombination of ductal patency and transpulmo-nary transmission of a high left ventricular enddiastolic pressure (LVEDP) secondary to leftheart obstruction.3,4 Treatment should aim atre-establishing dual coronary arterial supply fromthe aorta. It is important to recognize this asso-ciation ahead of neonatal repair of the coarcta-tion, because repair of coarctation may result indiminished pulmonary artery pressures (e.g.after ligation and division of the ductus arterio-sus), which will reduce coronary perfusionpressure.5,6

We report two patients in whom the anomalousleft coronary artery arose from the right pulmo-nary artery in association with aortic coarctationand congenital stenosis of the mitral valve.

Case Reports

Our first patient was an infant of 5 months,weighing 5.5 kg, who presented with increasingheart failure 2 months after repair of aortic coarc-tation. Pre-operative echocardiography failed todemonstrate any coronary abnormality; however,in retrospect, the coronary imaging was sub-optimal. She was known to have a mildlystenosed, parachute, mitral valve, diagnosed at thetime of her initial presentation. There was nosuggestion of ischemia on the pre-operative elec-trocardiogram.

As part of the evaluation for symptoms andsigns of heart failure, she underwent echocardio-graphy, which revealed significantly decreasedleft ventricular function with echogenicity of thepapillary muscles, suggesting ischemia. Cardiac

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© 2010 Copyright the AuthorsJournal Compilation © 2010 Wiley Periodicals, Inc. Congenit Heart Dis. 2010;5:327–330

catheterization revealed the anomalous origin ofthe left coronary artery from the right pulmonaryartery. There was no residual coarctation, and thepulmonary artery pressures were normal. Thefollowing week, she underwent uncomplicateddirect transfer of the coronary artery to itsappropriate aortic sinus. The left ventricularfunction had recovered 7 months after thereimplantation.

The second patient was another infant, aged 8months, who weighed 7.8 kg. This patient hadundergone elective repair of aortic coarctationand relief of mitral stenosis secondary to a para-chute mitral valve. On weaning from bypass,acute changes in the ST segments were notedelectrocardiographically, along with hemody-namic instability. Intra-operative transesophagealechocardiography showed an abnormal pattern offlow in the coronary arteries, with significant dias-tolic retrograde flow in the left coronary artery.Coronary and pulmonary angiography demon-strated the anomalous origin of the left coronaryartery from the inferior wall of the right pulmo-

nary artery (Figure 1). There was evidence of ret-rograde filling of the left coronary arterial system,with prominent collateral vessels from the rightcoronary artery coursing through the ventricularseptum. Pre-operative echocardiography had sug-gested a normal origin of the coronary arteries,and pulsed wave Doppler interrogation has alsoproduced normal patterns. With hindsight, thisimaging was not definitive and should, given thecombination of diagnoses, have led to a morethorough investigation of the coronary anatomy(Figure 2). The patient underwent a direct transferof the left coronary artery from the pulmonaryartery to the appropriate aortic sinus, with anuneventful recovery.

Discussion

The embryological process by which the coronaryarteries become connected to the aorta remainsincompletely understood. The current predomi-nant thinking is that the coronary arteries begin asa primitive plexus of unperfused vessels around the

Figure 1. Angiography showing antegrade filling of the left coronary artery from the right pulmonary artery in our secondpatient, shown in anteroposterior (A) and lateral (B) projections.

Figure 2. The pre-operative echocardiogram in our second patient, showing apparently normal origin (B) and flow (A) in theleft coronary artery. This was later disproved clinically and on angiography.

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aortic root before an invagination of the structuresthat will become the left and right coronary arter-ies, rather than developing as an outpouching ofthe aortic sinus, as had previously been thought tobe the case.7 The cellular and molecular details ofthis connection remain unresolved.8–10 Interest-ingly, knock-out studies in mice have suggestedthat perlecan, a proteoglycan with numerousextracellular matrix signaling functions, may be animportant factor in directing the coronary arteriesto connect with the aorta. In these mice models,the coronary arteries connected either aberrantlyto the aorta or to the pulmonary trunk.11,12

Another candidate gene is the gap junction geneConnexin43. Knock-out mice models involvingthis gene have produced various positional anoma-lies of the coronary arteries, including anomalousorigin.9

The combination of left-sided obstructionwith anomalous coronary arterial origin fromthe pulmonary circulation produces a predictablesyndrome, albeit with hindsight in the previouscases. The typical high neonatal pulmonary vas-cular bed resistance and pressures, which oftenprotects the neonate and delays the onset ofischemia by driving pulmonary arterial bloodinto the coronary arterial system, are maintainedin this subgroup. Clinical presentation, therefore,may be delayed by the concomitant obstructionin the systemic circulation. The perfusion pres-sure in the anomalously connected coronaryartery is maintained by pulmonary venous hy-pertension secondary to a raised left ventricularend diastolic pressure combined with a degree ofmitral stenosis. Hence, the electrocardiogrammay remain normal, and there may be minimalretrograde flow in the anomalous coronary arteryprior to relief of the left-sided obstruction.Despite the fact that the degree of mitral stenosiswas not severe in either case we must postulatethat this, in combination with a raised LVEDP,provided the mechanism for the clinical course inthese cases.

Convincing two-dimensional, color flowmapping, and Doppler interrogation of the proxi-mal right coronary artery, the left main stem,left anterior descending, and circumflex should bereviewed by an experienced echocardiographerprior to repair. Failure to definitively demonstratean abnormality is not a substitute for definitivedemonstration of normality, and review of both ofour cases illustrates this point well.

Even in the presence of perceived normalimaging, an appropriate index of suspicion should

be maintained in the knowledge that echocar-diographic assessment of functional coronaryanatomy is an imperfect science.13 Failure toclearly delineate the coronary anatomy shouldindicate the need for more definitive cross-sectional imaging or angiography.

Corresponding Author: Gareth Morgan, Mphil,Bristol Congenital Heart Centre, Upper MaudlinStreet, Bristol BS2 8BJ, UK. Tel: (+44) 117 93428332;Fax: (+44) 117 93428857; E-mail: hotmorgan@doctors.net.uk

Conflict of interest: None.

Accepted in final form: August 31, 2009.

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