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|Year : 2014 | Volume
| Issue : 4 | Page : 397-399
Aortic coarctation associated with an absent segment of the proximal right subclavian artery
A Jasper, SN Keshava
Department of Radiology, Christian Medical College, Vellore, Tamil Nadu, India
|Date of Submission||09-Apr-2013|
|Date of Decision||08-Nov-2013|
|Date of Acceptance||18-Dec-2013|
|Date of Web Publication||5-Nov-2014|
Dr. A Jasper
Department of Radiology, Christian Medical College, Vellore, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Coarctation of the aorta is a congenital anomaly of the thoracic aorta with many known associations. We describe the case of a young man referred for management of subarachnoid hemorrhage, in whom subsequent work-up revealed the previously undescribed combination of severe postductal aortic coarctation and an absent segment of the proximal right subclavian artery.
Keywords: Adult, angiography, aorta, arteries, congenital, vascular
|How to cite this article:|
Jasper A, Keshava S N. Aortic coarctation associated with an absent segment of the proximal right subclavian artery. J Postgrad Med 2014;60:397-9
| :: Introduction|| |
Coarctation of the aorta usually occurs sporadically in the general population. It may occur in isolation or in association with various other lesions. The diagnosis of coarctation may be missed unless there is a high index of suspicion. About 90% of patients with severe undetected aortic coarctation die by the age of 58 years due to complications like congestive cardiac failure, aortic rupture, intracranial aneurysm rupture and infective endocarditis. 
| :: Case Report|| |
A 29-year-old man presented with a sudden onset of severe holo-cranial headache. A noncontrast brain computed tomography (CT) showed a subarachnoid hemorrhage localized to the anterior inter-hemispheric fissure. He was conscious, oriented and had no neurological deficits. There was no significant past medical history. A diagnostic cerebral angiogram was performed to evaluate the cause of subarachnoid hemorrhage. Right retrograde femoral access was secured by the Seldinger technique using a 5Fr sheath.  ("Fr" is an abbreviation of the French scale or French Gauge system used to measure the size of a catheter. The diameter of a catheter in millimeters can be determined by dividing the French size by 3.  ) A 0.035-inch hydrophilic guide wire was required to manipulate the 5Fr Headhunter catheter beyond the stenotic segment of the aorta at the level of the left main bronchus. Diagnostic cerebral angiogram revealed a bi-lobed aneurysm located at the junction of the anterior communicating artery and left A2 segment [Figure 1]. Selective left vertebral angiogram showed retrograde flow in the right vertebral artery, indicating the presence of a right subclavian steal phenomenon [Figure 2]. A subsequent arch aortogram revealed a diffusely narrowed aortic arch with severe postductal aortic coarctation. The left subclavian artery was markedly tortuous and hypertrophied, with multiple large collateral vessels producing inferior rib notching [Figure 3] and [Figure 4]. On the right side, only a short stump of the origin of the subclavian artery was visualized. However, delayed images revealed an absent intervening segment, with the rest of the right subclavian artery being supplied by retrograde flow through the right vertebral artery and multiple collaterals from the right external carotid artery [Figure 5] and [Figure 6]a and b.
|Figure 1: Selective left internal carotid angiogram showing berry aneurysms in the anterior communicating artery (small black arrows)|
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|Figure 2: Selective left vertebral artery (large black arrow) injection shows retrograde flow in the right vertebral artery (small black arrows)|
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|Figure 3: Arch aortogram shows a postductal aortic coarctation (thin black arrows) with only a stump of the origin of the right subclavian artery (thick black arrow)|
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|Figure 4: Narrowed aortic arch (thick black arrow) and markedly hypertrophied left subclavian artery and its branches (thin black arrows)|
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|Figure 5: Delayed phase of the arch aortogram showing the right subclavian artery (black arrow heads) being opacified through retrograde flow from the right vertebral artery and collaterals of the right external carotid artery|
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|Figure 6: (a) Selective injection of the right common carotid artery shows tortuous collaterals (small thin black arrows) arising from the right external carotid artery. (b)The collaterals from the right external carotid artery are seen to supply the right subclavian artery distal to the occluded segment (thick black arrow) in the delayed phase|
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patient underwent stenting for aortic coarctation prior to cranial surgery as his blood pressure was uncontrolled. The anterior communicating artery aneurysm was surgically clipped. No intervention was offered for the absent segment of the right subclavian artery as it was asymptomatic. He had an uneventful postoperative period and, at discharge from the hospital, had no neurological deficit.
| :: Discussion|| |
Coarctation of the aorta may be defined as a constricted aortic segment due to protrusion of thickened ridges into the aortic lumen.  The localized constriction may form a shelf-like structure with an eccentric opening or may be a membranous curtain-like structure with a central or eccentric opening. The constricted segment may be short or long, the former being more common. Aortic coarctation has been described as preductal (or infantile) type or postductal (or adult) type, depending on whether the coarctation segment is proximal or distal to the ductus arteriosus, respectively.  The classic coarctation segment is located in the thoracic aorta, distal to the origin of the left subclavian artery, at about the level of the ductus arteriosus. A postductal coarctation results when there is partial involution of the dorsal aorta just distal to the left sixth arch artery. 
Aortic coarctation may be associated with many other congenital cardiac anomalies like a patent ductus arteriosus, ventricular septal defect, aortic stenosis and bicuspid aortic valves. It is the most common cardiac defect associated with Turner syndrome. 
Saccular or berry aneuryms are the most common cause of nontraumatic subarachnoid hemorrhage. They are known to be associated with aortic coarctation in about 10% of cases and are related both to high pressure of the vascular tree above the coarctation and to congenital defects of the vascular tree. " With a five-fold increase in incidence of berry aneuryms in those with aortic coarctation compared with the general population, an increase in the incidence of subarachnoid hemorrhage in patients with aortic coarctation can also be expected.
Another well-described association of left-sided aortic arch coarctation is an aberrant right subclavian artery. " Embryologically, the right subclavian artery has three components; the most proximal segment is derived from the right fourth arch, the middle segment develops from the cranial portion of the right dorsal aorta and the most distal segment is derived from the right seventh intersegmental artery. During normal embryological development, the right dorsal aorta disappears between the origin of the seventh intersegmental artery and the junction with the left dorsal aorta.  In our case, although the origin of the right subclavian was visualized and was normal, a short segment of the proximal subclavian artery was not visualized and the rest was opacified through retrograde flow from the right vertebral artery and right external carotid artery collaterals. We presume that the proximal segment, which is embryologically derived from the right fourth arch, had failed to develop completely.
This case was interesting because our patient, while being evaluated for a subarachnoid hemorrhage, in addition to the cerebral berry aneurysms that caused the bleed, was also found to have a severe postductal aortic coarctation with an absent segment of the proximal right subclavian artery. This combination of findings has not been previously reported.
| :: References|| |
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]