Can cardiac catheterization accurately assess the severity of aortic stenosis? An in vitro pulsatile flow study.

An accurate hemodynamic assessment of aortic stenosis has important clinical implications. In clinical practice, cardiac catheterization is often used to assess the severity of aortic stenosis. However, in conducting catheterization, the precise position of the catheter tip is often not known or controlled. From the standpoint of hydrodynamics, the position of the catheter tip may affect pressure measurement due to the complicated flow fields distal to the valve. This fact is particularly true when the diagnosed valve is stenotic. The study was aimed to investigate how the position of the catheter tip in catheterizing aortic stenosis affects pressure measurement. The experiments were conducted in an in vitro pulse duplicator system. Laser flow visualization was used to examine the flow fields in the vicinity of varying degrees of aortic stenosis, and a pressure transducer with a side-hole catheter was used to measure pressures. Minimal variation in transvalvular pressure drop measured along the radial direction was observed for varying degrees of valvular aortic stenosis. This implies that, in catheterization, the placement of the catheter tip along the radial direction does not seem to affect pressure measurement. However, along the axial direction, pressure recovery was observed for all the cases studied. Therefore, within the region of pressure recovery, the position of the catheter tip may affect the pressure drop measurement. This may cause inaccuracy in assessing the severity of aortic stenosis. However, this concern may be overcome by pulling the catheter slightly further downstream, so that the position of the catheter tip is outside of the pressure recovery region.