Ectopic Origin of One Pulmonary Artery from the Ascending Aorta

Abstract

When the normal pulmonary artery is absent, the blood supply to the lung may be derived from a number of anomalous sources. Manhoff and Howe (20) classify these as follows: Group I. Truncus Arteriosus : Both pulmonary arteries originate from a persistent truncus because of failure of development of the aorticopulmonary septum. Group II. Ductus Arteriosus: The ductus originates from the aortic arch or one of its primary vessels (either the innominate or subclavian artery) and communicates with the pulmonary plexus (1, 2, 4, 17, 21, 26, 30). Group III. Bronchial Arteries: Hypertrophied bronchial arteries may provide the only vascular supply to the lung in the absence of a pulmonary artery. Group IV. Abnormal Systemic Arteries: The arterial supply to the lung is derived from blood vessels not normally associated with this process embryologically, such as the subclavian, common carotid, celiac, superior mesenteric, and lower thoracic or abdominal aorta. To the original four groups suggested by Manhoff, we add a fifth in which one pulmonary artery arises ectopically from the ascending aorta. The purpose of this paper is to present three cases of ectopic origin of one pulmonary artery from the ascending aorta and to discuss this entity. Early recognition of the anomaly is important because surgical correction may provide the only chance for survival. Presentation of Cases Case I: C. N., an infant male, was hospitalized for cardiac evaluation because of previous episodes of tachypnea, coughing associated with feedings, and a cardiac murmur discovered following delivery. Physical examination revealed an infant in respiratory distress who was minimally cyanotic when crying. Blood pressure was 108/60. A Grade IV/VI systolic murmur was loudest along the left sternal border and radiated to the back. A Grade II/VI decrescendo diastolic, murmur was heard at the apex. The electrocardiogram indicated left ventricular and right atrial hypertrophy. The following pressure data were obtained at cardiac catheterization: RA-6 mm Hg (mean); RV-64/4; MPA-64/27 (mean-44); LBA-105/19 (mean-54). A left-to-right shunt was not demonstrated, nor could the catheter be advanced past the main pulmonary artery. The chest film revealed a huge globular heart with a narrow base. Peripherally, the right lung was over-circulated and the vascularity of the left lung was at the upper limits of normal. Centrally, the pulmonary vessels and aorta were not well defined. The thorax was symmetrical with no mediastinal shift (Fig. 1). Biplane cineangiocardiography was performed with injection of contrast material into the right ventricle. The main and left pulmonary arteries were opacified but not the right (Fig. 2). Biplane retrograde brachial cineaortography demonstrated the right pulmonary artery originating posteriorly from the ascending aorta approximately 1.5 cm above the aortic valve and ramifying normally within the lung.