Experimental and numerical investigation of orbital atherectomy: absence of cavitation

Abstract

A definitive, quantitative investigation has been performed to determine whether orbital atherectomy gives rise to cavitation. The investigation encompassed a synergistic interaction between in vitro experimentation and numerical simulation. The experimentation was performed in two independent fluid environments: 1) a transparent tube having a diameter similar to that of the superficial femoral artery and 2) a large, fluid-filled, open-topped container. All of the experimental and simulation work was based on the geometric model of the Diamondback 360 atherectomy device (Cardiovascular Systems, Inc., St. Paul, MN). Rotational speeds ranged from 80,000 to 214,000 rpm. The presence or absence of cavitation in the experiments was assessed by means of high-speed photography. The photographic images clearly display the fact that there was no cavitation. Flow visualization revealed the presence of fluid flows driven by pressure gradients created by the geometry of the rotating crown. The numerical simulations encompassed the fluid environments and the operating conditions of the experiments. The key result of the numerical simulation is that the minimum fluid pressure due to the rotational motion was approximately 50 times greater than the saturation vapor pressure of the fluid. Since the onset of cavitation requires that the fluid pressure falls below the saturation vapor pressure, the computational outcome strongly supports the experimental findings.