Truncus Bicaroticus and an Aberrant Right Subclavian Artery Contributing to Internal Jugular Venous Line Misplacement into the Carotid Artery

A 75-year-old woman with pneumonia, ventilator-dependent respiratory failure, and hypotension underwent placement of a central venous catheter into what was thought to be the left internal jugular vein. Placement of this catheter was performed using a modified Seldinger technique. During the catheter placement, the patient was hypotensive and hypoxic, and blood return through both a large-bore needle and a triple-lumen catheter appeared dark and nonpulsatile. At that time, the blood pressure was 72/40 mm Hg, heart rate was 105 bpm, and oxygen saturation was 89% on 50% oxygen facemask. Chest radiography performed immediately after catheter placement was interpreted by the operative surgeon and an attending radiologist as showing the catheter tip to be within the superior vena cava. The central line was used for medication and fluid administration without the aid of a pressure bag but was not connected to a transducer. No total parenteral nutrition or vasopressors were infused. Three days after placement, the patient developed right-sided weakness and was found to have multiple left-sided cerebral infarcts seen on magnetic resonance imaging. A carotid duplex ultrasound showed the triple-lumen catheter to be in the left common carotid artery. The catheter was removed, and a subsequent computed tomographic angiogram demonstrated aberrant anatomy of the aortic arch (Figure 1). The carotid arteries arose from one common trunk, the truncus bicaroticus, and the subclavian arteries arose separately from the distal arch. The right subclavian artery arose aberrantly as the last arch branch and passed posterior to the esophagus. Both vertebral arteries arose from the subclavian artieries. The presence of truncus bicaroticus and subsequent catheter placement into the left carotid artery was not suspected on chest radiography as the catheter appeared to project over the superior vena cava, as would a left internal jugular vein catheter. We are of the opinion that this anatomic variation, in the setting of hypotension, contributed to arterial central line misplacement going undetected, which subsequently resulted in an embolic stroke.

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Figure 1.

Computed tomographic angiogram demonstrating a common carotid trunk, truncus bicaroticus, and aberrant right subclavian artery arising as the most distal aortic arch branch.

Discussion

A common origin of the carotid arteries is extremely rare. Embryologically, two complementary processes mark the development of the aortic arch branches. Obliteration of arterial segments and growth of mesenchymal interarterial septae are the two processes, both of which would be faulty in the development of a complex aortic arch abnormality. ¹ In our review of the English literature, we found two cadaveric studies that identified truncus bicaroticus associated with a common trunk for both subclavian arteries. ^1,2 We also found two clinical case reports of incidental angiographic findings of truncus bicaroticus with separate subclavian artery origins. ^3,4 Both of these patients were found to have this anatomic variation during angiograms performed for the evaluation of carotid stenosis. In these cases, however, the left subclavian artery origin was distal to the right subclavian artery origin. In our case, the right subclavian artery arose as the most distal branch of the arch and passed posterior to the esophagus from left to right. To our knowledge, the findings of truncus bicaroticus and an aberrant right subclavian artery have not been previously reported. In this case, an anatomic variation contributed to a misinterpreted chest radiograph of a left carotid artery central line misplacement that initially went undetected. The patient recovered from her respiratory failure but developed a permanent neurologic deficit.

Arterial misplacement of central venous catheters is a relatively rare event, and multiple factors contribute to this phenomenon. ⁵ Clearly, prevention of inadvertent arterial cannulation is ideal. A study evaluating 493 ultrasound-guided internal jugular vein cannulations revealed an arterial puncture rate of 1.4%. The subgroup analysis among operators revealed that the physicians' level of experience with central line placement did not affect the arterial puncture rate, but the level of experience with ultrasonography did. ⁶ It appears that with proper training in ultrasonography, this technique may reduce the arterial puncture rate and increase the overall success of attempted jugular venous catheter placements. Also, in the hypotensive patient, arterial blood gas sampling of the new line would be a useful adjunct and would help identify arterially placed catheters early. Finally, it should be noted that a femoral approach in the severely hypotensive patient would essentially eliminate the risk of stroke and should be considered.

In this case, a rare and previously unreported combination of anatomic variations of the aortic arch may have contributed to a delay in diagnosis of the misplacement. These variations, truncus bicaroticus and associated aberrant right subclavian artery, are indeed rare, but knowledge of these entities is relevant to the practice of general surgery, as is evident in this case.