Early Doppler-echocardiography evaluation of 597 prosthetic aortic valves :

Assessment of normal and abnormal function of heart valve prostheses remains challenging. Doppler echocardiography has been shown to allow hemodynamic evaluation in various clinical settings and has become the most widely used tool to assess prosthetic valve function. Prosthetic valves, even when they function normally, are to some degree obstructive to the blood flow. The normal values of gradients, pressure half-time, and effective orifice area depend on valve type and valve size. Doppler assessment of prosthetic valve function, thus, requires specification of valve type and valve size, and knowledge of the normal values. This study provides an updated overview on the available data of normal values to facilitate adequate interpretation of Doppler data.

Doppler echocardiographic evaluation of aortic valve prostheses is based on the use of variables heretofore validated mostly for native valves. Accordingly, this study examined the validity and relative usefulness of the Doppler valve gradient and area measurements in 31 patients (mean age 69 +/- 10 years) 20 +/- 4 months after implantation of a given type of aortic bioprosthesis ranging in size from 19 to 29 mm. Valve area data obtained with both the standard and simplified continuity equations were compared with known in vitro prosthetic valve area measurements and an excellent correlation was obtained between the standard and simplified continuity equations (r = 0.98, SEE +/- 0.07 cm2, p less than 0.0005) and between in vivo and known in vitro prosthetic valve areas (r = 0.86, SEE +/- 0.16 cm2, p less than 0.0005). Peak gradient ranged from 10.8 to 75.0 mm Hg (mean 35 +/- 16) and mean gradient from 7.6 to 43.7 mm Hg (mean 20.5 +/- 9.5). The correlations between prosthetic valve gradient and in vivo area were r = -0.53, SEE +/- 14 mm Hg and r = -0.49, SEE +/- 8.63 mm Hg for peak and mean gradient, respectively. These relations were improved by indexing valve area by body surface area. The best correlations were obtained between indexed valve area and a quadratic function of the gradient (r = -0.72, SEE +/- 11.72 mm Hg and r = -0.70, SEE +/- 7.28 mm Hg for peak and mean gradient, respectively), reflecting a curvilinear relation.(ABSTRACT TRUNCATED AT 250 WORDS)

Pannus formation after aortic valve replacement is not common, but obstruction due to chronic pannus is one of the most serious complications of valve replacement. The causes of pannus formation are still unknown and effective preventive methods have not been fully elucidated. We reviewed our clinical experience of all patients who underwent reoperation for prosthetic aortic valve obstruction due to pannus formation between 1973 and 2004. We compared the initial 18-year period of surgery, when the Björk-Shiley tilting-disk valve was used, and the subsequent 13-year period of surgery, when the St. Jude Medical valve was used. Seven of a total of 390 patients (1.8%) required reoperation for prosthetic aortic valve obstruction due to pannus formation. All seven patients were women; four patients underwent resection of the pannus and three patients needed replacement of the valve. The frequency of pannus formation in the early group was 2.4% (6/253), whereas it was 0.73% (1/137) in the late group (P < 0.05). Pannus was localized at the minor orifice of the Björk-Shiley valve in the early group and turbulent transvalvular blood flow was considered to be one of the important factors triggering its growth. We also consider that small bileaflet valves have the possibility of promoting pannus formation and that the implantation of a larger prosthesis can contribute to reducing the occurrence of pannus.