title: Funnel-tipped aortic cannula for reduction of atheroemboli.
abstract: BACKGROUND
  Atheroemboli caused by aortic manipulation poses a risk for stroke in patients undergoing cardiopulmonary bypass (CPB) surgery. One potential cause is the high velocity jet from aortic perfusion cannulae. This study describes the flow patterns of a novel funnel-tip cannula designed to reduce emboli by decreasing fluid velocity and resultant shear force on the aortic wall.
  
  
  METHODS
  A funnel-tip cannula was constructed and compared with standard straight-tip cannulae and the Dispersion (Research Medical Inc, Midvale, UT) and Sarns Soft Flow (Terumo Cardiovascular Systems Corp, Ann Arbor, MI) cannulae. Pressure drop measurements were collected at 1 to 6 L/minute flows. Velocity flow profiles were created using phase contrast magnetic resonance imaging. Absolute velocity was measured in a phantom aorta at 5 L/minute flow. Each cannula was further studied in a synthetic model of an atherosclerotic aorta to determine the mass of dislodged particulate matter generated at 2, 3, and 5 L/minute flows.
  
  
  RESULTS
  The funnel-tip cannula demonstrated significantly lower values (p < 0.05) in pressure drop (55 mm Hg), exit velocity (309 cm/second, 167 cm/second for center axis and wall, respectively), and particulate dislodgement (0.15 +/- 0.05 g) than other tested cannulae. The Soft Flow cannula generated the next lowest pressure drop but exhibited twice the exit velocity and particulate dislodgement of the funnel-tip cannula. The Dispersion cannula did not demonstrate a reduction in velocity or particulate dislodgement compared with the standard straight-tip cannulae.
  
  
  CONCLUSIONS
  The results of this study suggest that a low-angled funnel-tip cannula has favorable flow characteristics warranting further investigation. Design development may reduce the risk of atheroemboli generation during CPB surgery.
authors.affiliation: Department of Surgery, Division of Cardiac Surgery, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
authors.forename: Jennifer K
authors.initials: JK
authors.lastname: White
authors.forename: Anand
authors.initials: A
authors.lastname: Jagannath
authors.forename: Jim
authors.initials: J
authors.lastname: Titus
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Yoneyama
authors.forename: Joren
authors.initials: J
authors.lastname: Madsen
authors.forename: Arvind K
authors.initials: AK
authors.lastname: Agnihotri
mesh_terms: D001783:Blood Flow Velocity; D006328:Cardiac Catheterization / Q000295:instrumentation* / Q000379:methods; D006348:Cardiac Surgical Procedures; D002315:Cardiopulmonary Bypass / Q000009:adverse effects; D017700:Embolism, Cholesterol / Q000517:prevention & control*; D004867:Equipment Design; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008422:Materials Testing; D010477:Perfusion; D012212:Rheology