aka Cardiovascular Curveball 004
A 26 year-old man presented to the ED with chest pain, He tripped on some steps and the right-side of his chest collided with the handrail.
This is his chest radiograph:
Q1. What are the chest radiograph findings?
There is a right-sided aortic arch. The trachea is deviated to the left of the midline rather than the right. There is no evidence of traumatic injury or situs inversus.
About 1 in 100,000 people have a right-sided aorta. It occurs during embryological development when the left 4th branchial arch involutes and the right remains, rather than vice versa.
A right-sided aortic arch can simply be mirror image of a normal left-sided arch, in which case situs inversus may also be present. Alternatively, the right-sided arch may give rise to a left subclavian artery that passes leftwards behind the esophagus, or the arch may cross over into a normal left-sided descending thoracic aorta.
Q2. What is the significance of this radiographic finding?
Right sided aortic arches are asymptomatic if they occur in the absence of other cardiovascular abnormalities.
However, if a right-sided aortic arch is present, other abnormalities such as Tetralogy of Fallot (20% have a right-sided aortic arch) and truncus arteriosus may also be present. These abnormalities are more likely with right-sided aorta arches of the ‘mirror image’ type.
Q3. If a child has this finding and presents with respiratory distress or dysphagia what should be suspected?
Obstruction from a vascular ring encircling and constricting the trachea and /or esophagus.
For instance, a ring forms around the trachea and esophagus when a left-sided ligamentum arteriosum connects the left pulmonary artery and a retroesophageal left subclavian artery arsing from the right-sided aortic arch.
This can mimic croup or recurrent respiratory tract infections – the diagnosis requires a high index of suspicion.
Bronchoscopy and barium esophagraphy help define the extent of airway or esophageal compression. Echocardiography and/or cardiac catheterisation may also be used to define the nature of any cardiovascular anomalies associated with the vascular ring. CT or MRI may also be performed. The ring can be released by division of the ligamentum arteriosum.
Q4. What is the diverticulum of Kommerell?
The diverticulum of Kommerell is a dilated pouch at the aortic origin of the retroesophageal left subclavian artery.
It is formed from the remnant of the involuted left branchial arch. Its presence makes the vascular ring tighter, increasing compression of the trachea and esophagus. Thus, right-sided aortic arches that have vascular rings associated with a diverticulum of Kommerell are more likely to be symptomatic.
- Adam A, Dixon AK, Grainger RG, Allison DJ. Grainger & Allison’s Diagnostic Radiology, (5th ed) 2008. Churchill Livingstone.
- Keane JF, Lock JE, Fyler DC. Nadas’ Pediatric Cardiology, (2nd ed) 2006. Saunders.
- Yamamoto LG. Difficulty Breathing Throughout Infancy. Radiology Cases in Pediatric Emergency Medicine Volume 6, Case 19 [excellent pediatric emergency medicine radiology case online here]