Centamore G, Campione S, Leto G, Galassi A R, Coco R, Evola R, La Spina L, Milazzotto A, Palazzo G, Galassi A
Divisione di Cardiologia, Ospedale Cannizzaro, Catania.
G Ital Cardiol. 1992 Oct;22(10):1201-10.
The proximal isovelocity surface area (PISA) method, assessed by color Doppler echocardiography, has gained acceptance as a means of calculating flow rate through regurgitant orifice. The method can also be used to derive mitral valve area (MVA), by continuity equation, in patients with mitral stenosis (MS). The aim of this study was to compare the PISA method with the two-dimensional echocardiographic planimetry (2D) method and pressure half-time method (PHT) in MVA calculations in a group of 37 patients with MS.
All of these patients had satisfactory MVA by 2D method. There were 22 female and 15 male; age 56 +/- 11 years (range 32-71); 19 were in sinus rhythm (SR) and 18 in atrial fibrillation (AF); 17 patients had pure MS, while the remaining 20 had associated mitral regurgitation (MR); in 23 patients the orifice morphology was circular or elliptic, and was defined as regular; while in 14 patients the morphology was irregular for the presence of two or more nodular calcifications on the commissures or leaflet's edges. MVA by PISA method was calculated assuming a uniform radial flow convergence region along a hemispherical surface, according to the formula: MVA = 2 pi r2 Vn(1-cos theta)/Vmax; where r was the PISA radius measured in 2D from the first alias to the mitral leaflet's edge; Vn was the flow velocity at radial distance from the mitral orifice; Vmax was the peak transmitral velocity by CW Doppler; 1-cos theta was a factor that accounted for the inflow angle formed by the mitral leaflets. The Nyquist limit was lowered to 29 cm/sec. Alpha angle formed by the mitral leaflets ranged between 86 degrees and 134 degrees; average 110 degrees +/- 10 degrees. 2D MVA was 1.33 +/- 0.37 cm2; range 0.69-2.2 cm2; PHT MVA was 1.29 +/- 0.34 cm2; range 0.70-2.1 cm2; PISA MVA was 1.18 +/- 0.36 cm2; range 0.47-1.95 cm2. The PISA method underestimates MVA by 0.15 +/- 0.21 cm2, in comparison with the 2D method; and by 0.11 +/- 0.18 cm2 in comparison with PHT method (p ns). The correlation between 2D and PISA MVA was: r = 0.84; p < 0.001; y = 0.83x + 0.06; 95% confidence intervals +/- 0.40 cm2; and between PHT and PISA MVA was: r = 0.79; y = 0.84x + 0.09; p < 0.001; 95% confidence intervals +/- 0.46 cm2. The correlation coefficient was similarly good in patients with SR or AF, and did not significantly change in patients with pure MS or MS+MR; neither did it vary with respect to the orifice morphology (p < 0.001 for all the variables considered), except for the correlation PHT-PISA in the group of patients with irregular orifice morphology (r = 0.70; p = 0.005). The interobserver and intraobserver variability were, respectively: 2.2% and 4.4% for 2D MVA; 3.4% and 3.8% for PHT MVA; 5.2% and 3.5% for the PISA radius; 6.1% and 4.4% for the alpha angle; 10.2% and 7.2% for PISA MVA (F ratio of variances ns).
In conclusion, the PISA method allows accurate assessment of MVA in patients with MS, regardless of cardiac rhythm or additional MR. Moreover, our study suggests that orifice morphology does not affect the accuracy of this method.
通过彩色多普勒超声心动图评估的近端等速表面积（PISA）法已被认可为计算通过反流口血流量的一种方法。该方法也可用于通过连续方程推导二尖瓣狭窄（MS）患者的二尖瓣面积（MVA）。本研究的目的是在一组37例MS患者中比较PISA法与二维超声心动图平面测量法（2D）和压力减半时间法（PHT）在MVA计算中的差异。
所有这些患者通过2D法测得的MVA结果均令人满意。其中女性22例，男性15例；年龄56±11岁（范围32 - 71岁）；19例为窦性心律（SR），18例为心房颤动（AF）；17例患者为单纯MS，其余20例合并二尖瓣反流（MR）；23例患者的瓣口形态为圆形或椭圆形，定义为规则形态；14例患者因瓣叶交界处或边缘存在两个或更多结节状钙化而形态不规则。根据公式MVA = 2πr²Vn(1 - cosθ)/Vmax，采用PISA法计算MVA，假设沿半球形表面存在均匀的径向血流汇聚区域；其中r为在二维图像上从第一个伪像到二尖瓣叶边缘测量的PISA半径；Vn为距二尖瓣口径向距离处的血流速度；Vmax为连续波多普勒测得的二尖瓣峰值流速；1 - cosθ为一个考虑二尖瓣叶形成的流入角度的因子。将奈奎斯特极限降低至29 cm/秒。二尖瓣叶形成的α角在86°至134°之间；平均110°±10°。2D法测得的MVA为1.33±0.37 cm²；范围0.69 - 2.2 cm²；PHT法测得的MVA为1.29±0.34 cm²；范围0.70 - 2.1 cm²；PISA法测得的MVA为1.18±0.36 cm²；范围0.47 - 1.95 cm²。与2D法相比，PISA法低估MVA 0.15±0.21 cm²；与PHT法相比低估0.11±0.18 cm²（p无统计学意义）。2D法与PISA法测得的MVA之间的相关性为：r = 0.84；p < 0.001；y = 0.83x + 0.06；95%置信区间±0.40 cm²；PHT法与PISA法测得的MVA之间的相关性为：r = 0.79；y = 0.84x + 0.09；p < 0.001；95%置信区间±0.46 cm²。在SR或AF患者中，相关系数同样良好，在单纯MS或MS + MR患者中无显著变化；在瓣口形态方面也无差异（所有考虑变量的p均< 0.001），除了瓣口形态不规则的患者组中PHT与PISA的相关性（r = 0.70；p = 0.005）。观察者间和观察者内的变异性分别为：2D法测得的MVA为2.2%和4.4%；PHT法测得的MVA为3.4%和3.8%；PISA半径为5.2%和3.5%；α角为6.1%和4.4%；PISA法测得的MVA为10.2%和7.2%（方差F比值无统计学意义）。
总之，PISA法能够准确评估MS患者的MVA，无论其心律或是否合并MR。此外，我们的研究表明瓣口形态不影响该方法的准确性。
