title: [Noninvasive determination of the orifice area of aortic valve prostheses using Doppler echocardiography].
abstract: In aortic valve stenosis, Doppler echocardiography enables reliable estimation of the orifice area with the use of the continuity equation. This study was carried out to determine the usefulness of the method in evaluation of prosthetic aortic valve area. Accordingly, 32 patients with normally-functioning mechanical Björk-Shiley prostheses underwent Doppler investigations two to three weeks after aortic valve replacement. Pre(v1)- and post(v2)-prosthetic velocities were recorded by pulsed and continuous-wave Doppler, respectively, and the prosthetic annulus used as cross-sectional area of flow (A1). For calculation of prosthetic orifice area (A2), the continuity equation at peak flow (v1,p) was employed where A2 = A1 X v1,p/v2 (at the point in time of v1,p). Mean pressure gradients across the prostheses were determined with the use of the modified Bernoulli equation. In addition, the ratio of acceleration to ejection time (AT/ET) was derived from the velocity profile of v2. Consistent with increasing prosthetic sizes (A 23 to A 29), there were increases in the calculated orifice areas A2 (A 23: 1.46 +/- 0.26, A 25: 1.71 +/- 0.24, A 27: 2.12 +/- 0.26, A 29: 2.53 +/- 0.35 cm2). Albeit with a substantial overlap between the various sizes, mean values for the respective sizes differed statistically significant and were comparably within the range established by in-vitro measurements. Pressure gradients across the prostheses were also different for the various sizes and were within the range reported from hemodynamic studies. In contrast, the AT/ET-ratio showed no significant difference between different prosthetic sizes.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D001021:Aortic Valve / Q000601:surgery*; D001783:Blood Flow Velocity; D002302:Cardiac Output; D004452:Echocardiography; D006350:Heart Valve Prosthesis; D006801:Humans; D011474:Prosthesis Design; D012212:Rheology
vernacular_title: Nichtinvasive Bestimmung der Offnungsfläche von Aortenklappenprothesen mit Hilfe der Doppler-Echokardiographie.