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Previous Volume 355:1283-1284 September 21, 2006 Number 12 Next

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To the Editor: The medical mystery in the July 27 issue¹ involved a chest film (Figure 1A) showing cardiomegaly and a left-sided pacemaker, the leads from which took an unusual course through the mediastinum, to the left of the midline. A persistent left-sided superior vena cava was suspected. A right-sided paratracheal soft-tissue density was also present (Figure 1A, arrowheads). Contrast-enhanced computed tomography (CT) showed that this density was caused by a right-sided aortic arch and not by an aortic-arch aneurysm (Figure 1B, arrow). An aberrant left subclavian artery arising from a dilated diverticulum of Kommerell (Figure 1C, curved arrow) passed posterior to the esophagus. CT without contrast medium confirmed the presence of a persistent left-sided superior vena cava (L in Figure 1C) within the right-sided superior vena cava (R in Figure 1C) owing to the absence of a left brachiocephalic vein. A persistent left-sided superior vena cava occurs in 0.3% of the normal population and is often not recognized unless a central venous line or pacemaker is inserted. A right-sided arch with an aberrant left subclavian artery is the most common type of right-arch anomaly, with an incidence of approximately 1 in 2500.

View larger version (56K): [in this window] [in a new window]   Figure 1. Chest Film, Showing a Soft-Tissue Density (Panel A, Arrowheads), and Computed Tomography of the Chest, Showing a Right-Sided Aortic Arch (Panel B, Arrow) and an Aberrant Left Subclavian Artery (Panel C, Arrow).

 

J.R.A. Turkington, F.R.C.R.
E. McAteer, F.R.C.R.
Craigavon Area Hospital
Portadown BT63 5QQ, Northern Ireland, United Kingdom

Editor's note: We received 900 responses to this medical mystery — from 66 countries. Of these responses, 62% were from physicians in practice, 22% from physicians in training, 8% from medical students, and 8% from other readers. Many of the responses continue to reflect a team effort — such as after a discussion of the case during a teaching conference.

Forty-seven percent of responses correctly identified the left-sided superior vena cava with the pacemaker correctly inserted into the right heart, including 10 respondents (1%) who also noted the right-sided aortic arch. Twenty-one percent of respondents suggested that the answer was aortic disease (e.g., aneurysm, unfolding of the arch, aortic dissection, and arterial placement of the pacemaker), 6% suggested mediastinal disease, and the remaining 26% suggested a variety of conditions, including situs inversus with an inverted display of the image, pericardial effusion, azygous lobe, collapse of the left lower lobe, congestive heart failure, mitral valvular disease, and cannulation of the thoracic duct.

References

1. Turkington JRA, McAteer E. A medical mystery: abnormal chest X-ray film. N Engl J Med 2006;355:393-393. [Free Full Text]

PDF PDA Full Text Add to Personal Archive Add to Citation Manager Notify a Friend E-mail When Cited E-mail When Letters Appear Related Article by Turkington, J.R.A. PubMed Citation