Angiography in a 30-year-old man revealed the unique combination of aortic coarctation and an unusual arch anomaly. Proximal to the coarctation, a single arch vessel trifurcated into the brachiocephalic, left common carotid and left subclavian arteries. This anomalous arch vessel is a normal equine variant.
Coarctation of the aorta is associated with other congenital anomalies including bicuspid aortic valve, supravalvular and subvalvular aortic stenosis, patent ductus arteriosus, venticular and atrial septal defects. More unusual associated anomalies include mitral valve atresia, mitral valve prolapse, anomalous origin of the left circumflex artery from the right pulmonary artery, cor triatriatum, sinus of Valsalva aneurysm, complete transposition of the great vessels and double outlet left ventricle.[1,2]
Anomalies of the arch vessels associated with coarctation are very unusual but include right aortic arch, aberrant right and left subclavian arteries and brachiocephalic arterial stenosis.[2,5] In contrast, isolated aortic arch abnormalities are relatively frequent with the left carotid and brachiocephalic arteries arising from a common trunk and the origin of the left vertebral artery directly from the arch being the two most frequent. A rare anomaly in humans, seen frequently in horses, is a single arch vessel.
We report a patient with a single arch vessel originating proximal to a true coarctation of the aorta. This vessel trifurcated into the brachiocephalic, left common carotid and left subclavian arteries. Possible embryologic origins are considered.
A 30-year-old man was admitted to the hospital with upper extremity hypertension. There was a five-year history of headache with evaluation including a negative head CT and MRI. There was no history of lower extremity claudication or fatigue. Physical examination revealed no clubbing or cyanosis; the blood pressure was 170/110 mm Hg in both arms with diminished and delayed lower extremity pulses. The carotid arteries were 2+, symmetric and without bruits. Cardiac examination disclosed an [S.sub.4] and a grade 2/6 posterior intrascapular systolic murmur. A chest x-ray film revealed borderline left ventricular enlargement, a low aortic arch at the level of the left pulmonary artery with poststenotic dilatation of the descending aorta. There was no rib notching. The electrocardiogram revealed left ventricular hypertrophy.
Right heart catheterization demonstrated normal hemodynamics (RA, 6; PCWP, 12) and cardiac output (5.1 L/min), without evidence for a left-to-right shunt by oximetry. There was a 45-mm Hg peak-to-peak gradient across the aortic coarctation (ascending aorta, 135/80 mm Hg; distal to the coarctation, 90/70 mm Hg), but no pressure gradient across either the aortic or mitral valves. Coronary angiography demonstrated normal origin of the coronary arteries and a normal right dominant system. An arch aortogram (Fig 1) demonstrated a normal ascending aorta and a tricuspid aortic valve. There was an aortic coarctation distal to the origin of a large single arch vessel which trifurcated into the brachiocephalic, left common carotid and left subclavian arteries in normal sequence. An extensive network of collateral vessels to the descending aorta was visualized as well as prominent right and left internal mammary arteries. Magnetic resonance imaging confirmed the arch anomaly and demonstrated that the transverse aortic arch was anterior to the esophagus in its usual position. The coarctation arose 3 cm distal to the origin of the single arch vessel at the level of the ligamentum arteriosum.
The patient subsequently underwent successful surgical correction of the coarctation with placement of a 16-mm Goretex graft between the left subclavian artery and the descending aorta. Postoperative physical examination revealed no gradient between upper and lower extremity blood pressure readings (120/80 mm Hg).
This is the first report, to our knowledge, of a true aortic coarctation associated with an equine-type single arch vessel giving rise to the brachiocephalic, left common carotid and left subclavian arteries. Clarke and Dodrill described brachiocephalic and left common carotid arteries arising from a single orifice with a diminutive left subclavian artery partially fused to the left common carotid artery. This anomaly was associated with indentation of the aorta during systole resembling an eccentric coarctation. In contrast, the current report demonstrates a true coarctation distal to and separate from a single arch vessel. These findings were confirmed at surgery.
The right and left carotid artery systems develop from the third branchial arches and appeared normal in this patient except for their takeoff from the single arch vessel. The normal anterior position of the transverse aortic arch relative to the esophagus argues against a remnant right aortic arch. However, the left subclavian artery, which forms from the cephalad migration of the left seventh intersegmental artery, is abnormally fused with the left common carotid artery. Normally, the aortic arch distal to the left common carotid artery develops from the left fourth branchial arch. Abnormal development and distal hypoplasia of the left fourth branchial arch may have resulted in fusion of the left subclavian and left common carotid artery and distal coarctation.
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 Reid DA, Foster ED, Stubberfield J, Alley RD. Anomalous right subclavian artery arising proximal to a postductal thoracic aortic coarctation. Ann Thorac Surg 1981; 32:85-87
 Okita Y, Shigehito M, Kusuhara K, Ueda Y, Takafumi T, Tamura T. Brachiocephalic arterial stenosis associated with atypical aortic coarctation. Am J Cardiol 1987; 60:1202-03
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