Ann Thorac Surg 2001;71:1008-1010
© 2001 The Society of Thoracic Surgeons
Case report
Origin of the left pulmonary artery from the aorta: embryologic considerations
Giorgio M. Aru, MDa,
William P. English, MDa,
Charles H. Gaymes, MDb,
Bobby J. Heath, MDa
a Division of Cardiothoracic Surgery, Jackson, Mississippi, USA
b Division of Pediatric Cardiology, University of Mississippi Medical Center, Jackson, Mississippi, USA
Accepted for publication April 6, 2000.
Address reprint requests to Dr Aru, Division of Cardiothoracic Surgery, University of Mississippi Medical Center, 2500 N State St, Jackson, MS 39216-4525
e-mail: garu{at}surgery.umsmed.edu
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Abstract
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We observed a case of anomalous origin of the left pulmonary artery from the aorta in which the media of the abnormal vessel and the main pulmonary artery were fused, but without communication. This is the fifth isolated case of repair without the use of cardiopulmonary bypass reported in the literature. This pathology should be included in the aortic arch anomalies as a partial or complete failure of development of the left sixth arch.
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Introduction
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Anomalous origin of the left pulmonary artery (LPA) from the ascending aorta (ALPA) is a rare anomaly, usually reported in small series together with anomalous origin of the right pulmonary artery from the ascending aorta (ARPA), which is also rare but five to eight times more frequently encountered. Either definition implies that the opposite pulmonary artery originates from the main pulmonary artery (MPA). Here we report a case in which the anomalous vessel and the MPA were sharing the wall but without communication. New considerations on the embryology are offered.
A 3-week-old baby boy presented with respiratory distress, fever, and a systolic cardiac murmur. Chest radiograph revealed increased pulmonary vascularity in both lung fields and cardiomegaly. Echocardiogram suggested the presence of ALPA, which was confirmed by cardiac catheterization. Systemic pressures were recorded in the right ventricle and the right pulmonary artery. Chromosomal evaluation revealed no abnormalities.
A median sternotomy was performed and the LPA was found to originate from the left side of the mid ascending aorta and to cross on top of the MPA (Fig 1A). The LPA was detached from the aorta and dissected from the MPA. The wall of the anomalous LPA was deeply shared inferiorly with the superior wall of the MPA. After dissection, a very thin portion of media on both the MPA and LPA was left. Ductus arteriosus remnant was not found. The LPA was then reimplanted onto the MPA at the area of dissection, using a running polydioxanone 6-0 suture technique (Ethicon, Sommerville, NJ) without cardiopulmonary bypass (Fig 1B). Postoperative pulmonary artery pressure measured 42 mm Hg with a systolic aortic pressure of 92 mm Hg. The child is doing well 13 months postoperatively and the echocardiogram shows a widely patent LPA.
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Fig 1. (A) Origin of the left pulmonary artery from the mid ascending aorta. (B) Anomalous left pulmonary artery anastomosed to the main pulmonary artery.
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Comment
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In the past, both ALPA and ARPA have been improperly referred to as hemitruncus. Different from the truncus arteriosus, here the two semilunar valves are separated and well developed. There have now been 42 reported cases of ALPA [1–5] in the literature through 1999.
Only 7 cases (17%) are isolated defects. ALPA with only right aortic arch is still considered an isolated defect since the right aortic arch does not require correction. Right aortic arch is present in 75% of all the patients with ALPA and in 100% of the reported cases of isolated ALPA, including our case. ALPA has a strong association with tetralogy of Fallot and anomalous origin of the right subclavian artery, respectively in 58% and 23% of the cases. These lesions have been only rarely reported in ARPA. Genetic screening is recommended to rule out DiGeorge syndrome [4]. The fusion of the media of the LPA and MPA, present in our case, has not been previously reported.
ALPA and ARPA should be considered separate embryological and surgical entities. Much of the disagreement about the embryology arises from the fact that the development of the aortic arches and pulmonary arteries is still partially hypothetical. Moreover, ALPA and ARPA can have a high or low takeoff from the ascending aorta [5], and the ALPA may present with either right or left aortic arch, making an embryological explanation even more difficult. It has been postulated that the normal left pulmonary artery and the ductus arteriosus develop from the left sixth arch [5, 6]. Early theories regarding the embryology of ALPA held that an abnormal aortic arch development with a persistent fifth and absent sixth aortic arch results in this anomaly [3]. This would not explain the sharing of the media of the LPA with the MPA, since the fifth arch is more cranial. However, the two cases presented by Dodo [4] may actually be the persistence of the left fifth arch. In their patients the ALPA originates at the same level of the innominate artery, as visible in the published aortogram. This is similar to the high takeoff of ARPA, which is accepted to be a persistence of the fifth right arch [6]. Cucci [1] hypothesized that a "dorsorotation of the left ridge extending throughout the conotruncus" is responsible for this anomaly. However, while this would explain the frequent association of tetralogy of Fallot to ALPA, it would not explain the rarity of ALPA in tetralogy of Fallot. Van Praagh [2] believes that failure of detachment of the origin of the left sixth arch from the aortic sac produces this defect. This theory seems acceptable to us, but it would not explain the association of ALPA with patent ductus arteriosus (PDA), which derives from the left sixth arch, in only 16% of the cases. Moreover, from review of the literature, we found that those PDA reported in ALPA are only on the right side and in patients with right aortic arch. Because the left sixth arch should participate in the formation of the ductus arteriosus in patients with left aortic arch (LAA) [5], Van Praagh’s [2] theory does not explain why there are no reported cases of PDA in ALPA and left aortic arch.
Therefore, based on our finding and the previously mentioned embryologic considerations, we believe that a failure of fusion of the LPA with the MPA (attempted in our case as fusion of the media) results in persistence of the aortic sac from which the PAs originate. The fifth and sixth arches on the left probably never developed either, as supposed by Van Mierop. It is possible that the sixth left arch, which develops as ductus arteriosus, is related to the fusion of the LPA to the MPA in both right aortic arch and LAA. The ductus arteriosus usually inserts in the first portion of the LPA, opposite to the point where the LPA departs from the MPA. In the absence of the left sixth arch, the LPA may not find connection to the MPA and consequently the aortic sac connection persists. Thus, we believe that proximal ALPA should be included in the aortic arch anomaly complex as partial or complete absence of the left sixth arch, as hypothesized by Van Mierop.
From a review of the literature through 1999, our case represents the fifth case of isolated ALPA successfully corrected without cardiopulmonary bypass. In our case, as well as in the others, the pulmonary artery pressure decreased immediately and continued to decrease as demonstrated by follow-up echocardiogram. Early repair is recommended to prevent pulmonary vascular disease of the hypertensive lung(s).
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References
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Cucci C.E., Doyle E.E., Lewis E.W., Jr Absence of a primary division of the pulmonary trunk: an ontogenetic theory. Circulation 1964;28:124.
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Penkoske P.A., Castaneda A.R., Fyler D.C., Van Praagh R. Origin of the pulmonary artery branch from ascending aorta. J Thorac Cardiovasc Surg 1983;85:537-545.[Abstract]
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Sikl H. Unusual anomalies of arterial trunk: main branch of pulmonary artery arising from aorta. Cas Lek Cesk 1952;91:1366-1369.[Medline]
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Dodo H., Alejos J.C., Perloff J.K., Laks H., Drinkwater D.C., Williams R.G. Anomalous origin of the left main pulmonary artery from the ascending aorta associated with DiGeorge syndrome. Am J Cardiol 1995;75:1294-1295.[Medline]
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Kutsche L.M., Van Mierop L.H.S. Anomalous origin of a pulmonary artery from the ascending aorta: associated anomalies and pathogenesis. Am J Cardiol 1988;61:850-856.[Medline]
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Mavroudis C, Backer C. Pediatric cardiac surgery, 2nd ed. Mosby, 1994;7, 512–5.
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Abstract
Introduction
