Effect of prosthetic valve malfunction on the Doppler-catheter gradient relation for bileaflet aortic valve prostheses.

Abstract

Considerable discrepancies between Doppler and catheter gradients caused by localized gradients and pressure recovery have been reported for normal bileaflet aortic valve prostheses. To examine whether this Doppler-catheter gradient relation is affected by prosthetic valve malfunction, a 19-mm CarboMedics aortic valve was simultaneously studied with continuous-wave Doppler and catheter technique in normal function and in various states of malfunction ranging from slightly restricted opening to total occlusion of one leaflet. For each functional status, peak and mean gradients were measured at eight different flow rates (cardiac output, 2.0-6.0 L/min). Excellent correlation between Doppler and catheter gradients was found regardless of the valve function (r = 0.99, SEE = 1.0-3.3 mm Hg). However, the relation between Doppler and catheter gradient was highly dependent on the function of the valve as shown by a variation of slopes from 1.08 to 2.08. For the normally functioning valve (angle between flow axis and leaflet 5 degrees), peak and mean Doppler gradients were approximately twice the catheter gradients (slope, 2.08 and 2.03 for peak and mean gradients, respectively). Slightly restricted opening of one leaflet (22 degrees) significantly altered the Doppler-catheter gradient relation, and slopes decreased to 1.69 (p < 0.01) and 1.52 (p < 0.001) for peak and mean gradients, respectively. The differences between Doppler and catheter gradients significantly decreased with further restriction of valve opening, and slopes ranged from 1.25 to 1.41 for angles between 34 degrees and 52 degrees. When one leaflet was totally occluded, the slope finally dropped to 1.08 for both peak and mean gradients, and Doppler gradients were only slightly greater than catheter gradients. Gradients increased with malfunction of the valve caused by reduction of the effective orifice area. However, the increase of Doppler gradients was considerably smaller than the increase of simultaneous catheter gradients. The discrepancies between Doppler and catheter gradients that have been reported for normally functioning bileaflet aortic valve prostheses may be reduced or even disappear in patients with malfunctioning valves. Furthermore, the increase of Doppler gradients caused by malfunction of the valve may underestimate the true hemodynamic changes.