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Original Articles: Adult Cardiac

Funnel-Tipped Aortic Cannula for Reduction of Atheroemboli

^a Department of Surgery, Division of Cardiac Surgery, Massachusetts General Hospital, Boston, Massachusetts
^b Cardiology Laboratory for Integrative Physiology and Imaging, Massachusetts General Hospital, Boston, Massachusetts

Accepted for publication April 28, 2009.

^_* Address correspondence to Dr Agnihotri, Massachusetts General Hospital, Department of Surgery, Division of Cardiac Surgery, Cox Building, Room 642, 55 Fruit St, Boston, MA 02114 (Email: aagnihotri{at}partners.org).

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.