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We have designed a new type of aortic cannula for extracorporeal circulation which we hypothesize has superior haemodynamic characteristics compared with existing types. The aim of the study was to perform a quantitative evaluation of the haemodynamic performance of commercially available aortic cannulas against our new design. Six existing cannulas and two selfdesigned, modified DLP cannulas were investigated. Pressure drop, peak velocity and wall thickness were obtained from in vitro experiments. Pressure drop and turbulent stresses were obtained by in vivo experiments. At 5 L/min the pressure drops of the new design were 18–25 mmHg in vitro and 20 mmHg in vivo compared with 25–92 mmHg in vitro and 28–90 mmHg in vivo for the six commercially available cannulas. Turbulent stresses of the new design varied between 25 and 50 N/m2in vivo compared with 125–500 N/m2. Both in vivo and in vitro results showed a clear haemodynamic superiority of the new cannula-tip design compared with all existing types.