APPLICATION OF PROXIMAL ISOVELOCITY SURFACE-AREA METHOD TO DETERMINE PROSTHETIC MITRAL-VALVE AREA

Background. In this study, we Investigated the accuracy of orifice are a determination of the prosthetic valve (Biocor) by using proximal iso velocity surface area method (PISA). Thirty-two patients (26 women, 6 men; mean age 44 +/- 8.1 years) were studied, Eleven patients were in normal sinus rhythm and the rest were in atrial fibrillation. Associat ed valvular lesions were mild aortic regurgitation in 12 patients and moderate tricuspid regurgitation in 19 patients. Sizes of prosthetic v alves were 27 to 31, and implantation duration was 4 to 8 years. Metho ds and Results. We analyzed the flow convergence zone proximal to the valve orifice with the concept of a hemispheric model Mitral valve are a (MVA) calculation was formulated by MVA = 2pr(2) Y Va/Vm Y (vm/vm - Va), where Vm Is the maximal mitral velocity and Vm/Vm - Va is a corre ction factor to account for flattening of isotachs near the prosthetic orifice. MVA calculations by PISA were compared with pressure half-ti me (PHT), continuity equation (CONT), and color flow area (CFA) method s. Mitral valve areas were 2.17 +/- 0.17 cm(2), 2.22 +/- 0.21 cm(2), 2 .19 +/- 0.22 cm(2), and 2.16 +/- 0.17 cm(2) in PISA, CFA, PHT, and CON T methods, respectively. Values in the comparison of MVA measurements by different methods were PISA vs PHT, r = .86; PISA vs CFA, r = .77; and MSA vs CONT, r = .89. Conclusions. The PISA method gives reliable estimates of large orifices such as prosthetic valves. Although the be st correlation was seen with the CONT method, results of this study al so confirmed that the PISA method can be applied with reasonable accur acy.