CONFIRMATION AND INITIAL DOCUMENTATION OF THORACIC AND ABDOMINAL AORTIC HELICAL FLOW - AN ULTRASOUND STUDY

Aortic helical flow may play an important role in plaque deposition, d issection formation, and organ perfusion. The authors have previously demonstrated, using in vitro flow models and transesophageal echocardi ography, that helical flow begins in the mammalian aortic arch and con tinues into the descending thoracic aorta. The purpose of this study w as to confirm thoracic aortic helical flow and document its extent int o the abdominal aorta using direct measurements. Twelve mongrel dogs u nderwent surgery with exposure of the abdominal aorta up to the diaphr agm. Six of the 12 underwent further thoracotomy with thoracic aorta e xposure. color Doppler ultrasound images were obtained using a 5 megaH z esophageal transducer, hand held, directly applied, and visually ali gned for transverse aortic imaging. Helical flow was considered presen t with the appearance of red/blue hemicircles during a systolic wave w hen the aorta was imaged transversely. All six dogs that had thoracoto my showed clockwise thoracic aortic helical flow (along the direction of blood flow) at the retro left ventricular region. In all dogs, cloc kwise helical flow was demonstrated to and immediately beyond the rena l arteries. In 11 of 12 dogs, clockwise helical flow was demonstrated 7 cm below the renal arteries. The study confirms the presence of heli cal flow in the thoracic aorta and documents its extent into the abdom inal aorta below the level of the renal arteries. The teleologic flow pattern of mammals may extend to other classes of vertebrates and must be accounted for in studies of endothelial shear and flow separation. In addition, tangential velocities imparted by helical flow may affec t organ perfusion.