The Rings of Saturn in the Aortic Arch? An Unusual Consequence of Cardiopulmonary Bypass in an Acute Type-A Aortic Dissection

A DISORIENTED 58-YEAR-OLD, 96-kg, 177-cm man was transported by helicopter to the authors' institution for treatment of an acute type-A aortic dissection. A computed tomography (CT) scan with angiographic contrast showed aneurysmal dilatation of the ascending thoracic aorta and an acute type-A aortic dissection originating proximal to the sinotubular junction that extended to the left iliac artery. The right iliac artery was poorly visualized. Right femoral and dorsalis pedis pulses were absent, but blood flow to the right leg was verified with Doppler ultrasound. The dissection extended into the innominate, left carotid, and left subclavian arteries. The patient was urgently transported to the operating room. A transesophageal echocardiographic (TEE) examination was performed after anesthetic induction that confirmed the CT findings and also revealed the presence of a large pericardial effusion without tamponade physiology and moderate aortic insufficiency. A median sternotomy was performed, the pericardium was opened, and the effusion was drained. The surgeon was reluctant to cannulate the left femoral artery for cardiopulmonary bypass because of the presence of the dissection. Potential compromise of right lower-extremity perfusion also suggested that a vascular bypass from the left to the right femoral artery may have been required for limb salvage. Furthermore, extension of the dissection into the innominate and right subclavian arteries precluded cannulation of these sites. As a result, the surgeon chose to directly cannulate the true lumen of the dissection in the distal ascending aorta using a Seldinger technique. Intravenous heparin was administered, a needle was inserted into the aorta, and a wire was advanced into the true lumen using TEE guidance. A 21F Bio-Medicus femoral arterial cannula (Medtronic, Minneapolis, MN) was then placed in the true lumen, and its position was confirmed with TEE (Fig 1, Fig 2). After venous cannulation, cardiopulmonary bypass was begun at a flow rate of 4.7 L/min, and cooling for subsequent deep hypothermic circulatory arrest was initiated. Color Doppler blood-flow interrogation of the cannula and transverse aortic arch revealed the presence of an unusual ring-like structure within the true lumen surrounding flow from the cannula itself (Fig 3 and Video 1). What is the cause of this finding?