Mitral Stenosis Severity by PISA

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J Am Coll Cardiol 1995 Aug;26(2):458-65
Comparison of proximal isovelocity surface area method with pressure half-time and planimetry in evaluation of mitral stenosis.
Rifkin RD, Harper K, Tighe D.
Department of Medicine, Baystate Medical Center, Tufts University School of Medicine, Springfield, Massachusetts 01199, USA.

OBJECTIVES. This study sought to 1) compare the accuracy of the proximal isovelocity surface area (PISA) and Doppler pressure half-time methods and planimetry for echocardiographic estimation of mitral valve area; 2) evaluate the effect of atrial fibrillation on the accuracy of the PISA method; and 3) assess factors used to correct PISA area estimates for leaflet angulation. BACKGROUND. Despite recognized limitations of traditional echocardiographic methods for estimating mitral valve area, there has been no systematic comparison with the PISA method in a single cohort. METHODS. Area estimates were obtained in patients with mitral stenosis by the Gorlin hydraulic formula, PISA and pressure half-time method in 48 patients and by planimetry in 36. Two different factors were used to correct PISA estimates for leaflet angle (theta): 1) plane-angle factor (theta/180 [theta in degrees]); and 2) solid-angle factor [1-cos(theta/2)]. RESULTS. After exclusion of patients with significant mitral regurgitation, the correlation between Gorlin and PISA areas (0.88) was significantly greater (p < 0.04) than that between Gorlin and pressure half-time (0.78) or Gorlin and planimetry (0.72). The correlation between Gorlin and PISA area estimates was lower in atrial fibrillation than sinus rhythm (0.69 vs. 0.93), but the standard error of the estimate was only slightly greater (0.24 vs. 0.19 cm2). The average ratio of the solid- to the plane-angle correction factors was approximately equal to previously reported values of the orifice contraction coefficient for tapering stenosis. CONCLUSIONS. 1) The accuracy of PISA area estimates in mitral stenosis is at least comparable to those of planimetry and pressure half-time. 2) Reasonable accuracy of the PISA method is possible in irregular rhythms. 3) A simple leaflet angle correction factor, theta/180 (theta in degrees), yields the physical orifice area because it overestimates the vena contracta area by a factor approximately equal to the contraction coefficient for a tapering stenosis.

Jpn Heart J 1997 Nov;38(6):811-9
Calculation of mitral valve area in mitral stenosis using the proximal isovelocity surface area method. Comparison with two-dimensional planimetry and Doppler pressure half time method.
Oku K, Utsunomiya T, Mori H, Yamachika S, Yano K.
Third Department of Internal Medicine, Nagasaki University, Japan.

Two-dimensional echocardiographic (2-D) planimetry and the Doppler pressure half-time (PHT) method have been used to estimate mitral valve area (MVA) in patients with mitral stenosis (MS). Recently, the proximal isovelocity surface area (PISA) method has been shown to be accurate for calculating MVA. The purpose of this study was to compare the PISA method with previous methods. Thirty patients with MS were studied; 17 had pure MS, 4 combined mild MR, 6 combined mild AR, and 3 combined MR and AR. Color Doppler flow mapping was performed at an aliasing (blue-red interface) velocity of 14 cm/sec using the zero-baseline shift. MVA was calculated as 2 x 3.14 x R2 x 14 x (theta/180) / PFV, where R is the distance from aliasing to orifice, 14 is the aliasing velocity, theta is the internal angle of the mitral valve, and PFV is the peak flow velocity at the mitral orifice. MVA was also calculated using the 2-D and PHT methods, and compared with the PISA method. MVA calculated using the PISA method correlated well with the 2-D (r=0.90, p < 0.01, SEE = 0.18 cm2) and PHT methods (r=0.82, p < 0.01, SEE = 0.24 cm2). Compared with the 2-D method, the standard error of the estimate of the PISA method was - 0.14+/-0.18 cm2 and the percent error was -10.4+/-18.9%. Compared with the PHT method, the standard error of the estimate of the PISA method was + 0.01+/-0.24 cm2 and the percent error was +3.4+/-34.6%. MVA calculated using the PISA method correlated well with the 2-D and PHT methods in patients with pure MS or with MS combined mild regurgitation. The PISA method may be useful for calculating MVA as an alternative method.

Am Heart J 1995 Jan;129(1):114-23 Related Articles, Links
Color flow Doppler determination of transmitral flow and orifice area in mitral stenosis: experimental evaluation of the proximal flow-convergence method.
Shiota T, Jones M, Valdes-Cruz LM, Shandas R, Yamada I, Sahn DJ.
Clinical Care Center for Congenital Heart Disease, Oregon Health Sciences University, Portland.

To evaluate the in vivo accuracy of color Doppler flow-convergence methods for determining transmitral flow volumes and effective orifice areas in mitral stenosis, we studied two models for flow-convergence surface geometry, a hemispheric (HS) model and an oblate hemispheroid (OH) model in a chronic animal model with quantifiable mitral flows. Color Doppler flow mapping of the proximal flow-convergence region has been reported to be useful for evaluation of intracardiac flows. Flow-convergence methods in patients with mitral stenosis that use HS assumption for the isovelocity surface have resulted in underestimation of actual flows. Chronic mitral stenosis was created surgically in six sheep with annuloplasty rings (group 1) and 11 sheep with bioprosthetic porcine valves (group 2). Hemodynamic and echocardiographic/Doppler studies (n = 18 in group 1; n = 21 in group 2) were performed 20 to 34 weeks later. Left ventricular inflow obstruction was of varied severity, with mean transmitral valve gradients in group 1 ranging from 1.3 to 18 mm Hg and in group 2 ranging from 6.3 to 25.6 mm Hg. Although transmitral flows derived by both geometric flow convergence models showed significant correlations with reference cardiac outputs, the correlations for the OH model were better than those for the HS model (group 1, r = 0.86 for the OH model vs r = 0.72 for the HS model; group 2; r = 0.84 for the OH model vs r = 0.62 for the HS model). The OH model was also superior to the HS model in determining effective orifice areas compared to reference orifice areas determined by postmortem planimetry of anatomic orifices (group 1 only, r = 0.64 for OH vs 0.58 for HS), by the Gorlin and Gorlin formula (group 1, r = 0.63 for OH vs 0.72 for HS; group 2, r = 0.82 for OH vs 0.76 for HS), and by the Doppler pressure half-time method (group 1, r = 0.76 for OH vs 0.69 for HS; group 2, r = 0.84 for OH vs 0.62 for HS). (ABSTRACT TRUNCATED AT 400 WORDS)

G Ital Cardiol 1992 Oct;22(10):1201-10
Validity of the proximal isovelocity surface area color Doppler method for calculating the valve area in patients with mitral stenosis; comparison with the two-dimensional echocardiographic method
Centamore G, Campione S, Leto G, Galassi AR, Coco R, Evola R, La Spina L, Milazzotto A, Palazzo G, Galassi A.
Divisione di Cardiologia, Ospedale Cannizzaro, Catania.

BACKGROUND. 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. METHODS AND RESULTS. 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). CONCLUSIONS. 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.

G Ital Cardiol 1991 Aug;21(8):815-23
Doppler estimation of the stenotic mitral valve area. Direct application of the continuity equation to the flow convergence region
Bargiggia GS, Scopelliti P, Bertucci C, Recusani F, Raisaro A, Bramucci E, Tronconi L, Montemartini C.
Divisione di Cardiologia, IRCCS Policlinico S. Matteo, Pavia.

The continuity equation, applied to the flow convergence region (FCR), furnishes a simple alternative to calculate stenotic valve area. The flow rate in the FCR can be calculated by multiplying the hemispheric isovelocity surface area by the velocity of the isovelocity surface. Since according to the continuity principle the flow rate through any isovelocity surface equals the flow rate through the stenotic orifice, the stenotic orifice area can be calculated as: 2 pi r2Vr/Vm, where 2 pi r2 is the hemispheric isovelocity area, Vr is the velocity at the radial distance r from the orifice and Vm is the peak jet velocity. This study was designed to analyze the validity of application of the continuity equation to the FCR for estimating mitral orifice area by Dopler ultrasound. We studied 35 consecutive patients with rheumatic mitral stenosis. Three patients were excluded; the final study population consisted of 32 patients (8 men and 24 women; mean age 56 years). Nine patients were in normal sinus rhythm and 23 in atrial fibrillation. Doppler examination was performed from the apical approach within 24 hours of cardiac catheterization. On color Doppler image Vr was defined as the first aliasing limit (lowered to 38 cm/s to increase FCR r); r represented the maximal early diastolic distance between the first alias and the stenotic orifice in a direction parallel to that of the transducer; Vm was the early diastolic peak jet velocity by continuous wave Doppler. (ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiography 2001 Feb;18(2):89-95
Can the proximal isovelocity surface area method calculate stenotic mitral valve area in patients with associated moderate to severe aortic regurgitation? Analysis using low aliasing velocity of 10% of the peak transmitral velocity.
Ikawa H, Enya E, Hirano Y, Uehara H, Ozasa Y, Yamada S, Ishikawa K.
The First Department of Internal Medicine, Kinki University School of Medicine, 377-2 Ohno-Higashi, Osakasayama, Osaka, Japan.

To assess the ability of the proximal isovelocity surface area (PISA) method to accurately measure the stenotic mitral valve area (MVA), and to assess whether aortic regurgitation (AR) affects the calculation, we compared the accuracy of the PISA method and the pressure half-time (PHT) method for determining MVA in patients with and without associated AR by using two-dimensional echocardiographic planimetry as a standard. The study population consisted of 45 patients with mitral stenosis. Seventeen of the 45 patients had associated moderate-to-severe AR. The PISA method was performed using low aliasing velocity (AV) of 10% of the peak transmitral velocity, which provided the most accurate estimation of MVA when compared with planimetry. The maximal radius r of the PISA was measured from the orifice to blue-red aliasing interface. Using the PISA method, MVA was calculated as (2pir(2)) x theta / 180 x AV/Vmax, where theta was the inflow angle formed by mitral leaflets, AV was the aliasing velocity (cm/sec), and Vmax was the peak transmitral velocity (cm/sec). MVA by the PISA method correlated well with planimetry both in patients with AR (r = 0.90, P < 0.001, SEE = 0.17 cm(2)) and without AR (r = 0.92, P < 0.001, SEE = 0.16 cm(2)). However, MVA by the PHT method did not correlate as well with planimetry (r = 0.57, P < 0.05, SEE = 0.37 cm(2)) in patients with associated AR, and the PHT method produced a significant overestimation (24%) of MVA obtained by planimetry in these patients. We conclude that the PISA method allows accurate estimation of MVA and is not influenced by AR.

G Ital Cardiol 1997 Feb;27(2):133-40
The "proximal isovelocity surface area" method in assessing mitral valve area in patients with mitral stenosis and associated aortic regurgitation.
Centamore G, Galassi AR, Evola R, Lupo L, Galassi A.
Divisione di Cardiologia Azienda Ospedaliera Cannizzaro, Catania.

BACKGROUND: This study compares the mitral valve area determined by Doppler color mapping of the proximal isovelocity surface area (PISA) and by Doppler pressure half-time with that obtained by two-dimensional planimetry in patients affected by mitral stenosis, with and without associated aortic regurgitation. Pressure half-time frequently overestimates the mitral valve area in patients with mitral stenosis and associated aortic regurgitation. PISA is an alternative method for determining mitral valve area in mitral stenosis and is not influenced by regurgitant lesions. METHODS: We studied 76 patients with mitral stenosis; aortic regurgitation > or = 2 was present in 24 patients. The PISA was recorded from the apex and the transmitral maximal flow rate, Q (ml/s), was calculated using the hemispheric equation Q = 2 pi R2 x AV x alpha/180, where R (cm) is the maximal radius of the PISA, AV (cm/s) is the aliasing velocity and alpha/180 is a correction factor accounting for the alpha inflow angle formed by the mitral leaflets. Mitral valve area, A (cm2), was calculated by continuity equation A = Q/V, where V (cm/s) is the peak transmitral flow velocity measured by continuous wave Doppler. RESULTS: The mitral valve area by two-dimensional planimetry (range 0.5-2.4 cm2; mean 1.33 +/- 0.41 cm2) was consistent with both PISA (r = 0.83; SEE 0.23 cm2) and pressure half-time (r = 0.79; SEE 0.25 cm2) methods. Similar agreement was found for the 36 patients with mitral regurgitation and for the 30 patients in atrial fibrillation. However, in patients with aortic regurgitation > or = 2, pressure half-time overestimated two-dimensional and PISA determined mitral valve areas by 0.24 +/- 0.25 cm2 (p < 0.01). CONCLUSIONS: In patients with mitral stenosis and significant aortic regurgitation, the PISA method is more accurate than pressure half-time in assessing mitral valve area. This method may be a reliable alternative when pressure half-time is affected by aortic regurgitation and two-dimensional planimetry images are unsuitable for anatomic evaluation.

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