Discrepancies between Doppler and catheter gradients in aortic prosthetic valves in vitro. A manifestation of localized gradients and pressure recovery.

Abstract

To evaluate possible causes of discrepancy between Doppler and catheter gradients across prosthetic valves, five sizes (19-27 mm) of St. Jude and Hancock valves were studied in an aortic pulsatile flow model. Catheter gradients at multiple sites distal to the valve were compared with simultaneously obtained Doppler gradients. In the St. Jude valve, significant differences between Doppler and catheter gradients measured 30 mm downstream from the valve were found: Doppler gradients exceeded peak catheter gradients of 10 mm Hg or more by 81 +/- 35% (15 +/- 3.6 mm Hg), and mean catheter gradients by 71 +/- 11% (10.3 +/- 2.5 mm Hg). When the catheter was pulled back through the tunnel-like central orifice of the valve, high localized gradients at the valve plane and significant early pressure recovery were found. When the catheter was pulled back through the large side orifices, gradients at the same level were only 46 +/- 6% of the central orifice gradients (mean difference, 7.6 +/- 4.5 mm Hg). Doppler peak and mean gradients showed excellent agreement with the highest central orifice catheter gradients (mean difference, 1.0 +/- 3.1 and 0.9 +/- 1.5 mm Hg, respectively). A significantly better agreement between Doppler and catheter gradients at 30 mm was found for the Hancock valve, although Doppler peak and mean gradients were still slightly greater than catheter gradients. Doppler gradients exceeded catheter gradients by 18 +/- 10% (3.4 +/- 1.9 mm Hg) and 13 +/- 11% (2.1 +/- 0.9 mm Hg), respectively. When the catheter was pulled back through the valve, the highest gradients were found approximately 20 mm distal to the valve ring.(ABSTRACT TRUNCATED AT 250 WORDS)