Effect of aortic regurgitation on the assessment of mitral valve orifice area by Doppler pressure half-time in mitral stenosis

Introduction: Hydrodynamic theory predicts fluid approaches a point orifice with accelerating velocity in hemispheric shells, forming the basis for the proximal isovelocity surface area (PISA) method to quantify valve regurgitation. Previous CFD and in vitro work has shown that with a finite, non-point orifice, there is a small, systematic underestimation of flow that is approximately the ratio of contour velocity (va) to maximal orifice velocity (vo), e.g., roughly an 8% error if a 40 cm/s contour is used with a 5 m/s jet. The PISA method is further questioned in the setting of noncircular orifices, with concerns of further underestimation. We sought to quantify this impact with CFD. Hypothesis: Application of standard PISA analysis to an elliptical orifice leads to further flow underestimation, but the magnitude is negligible. Methods: Mathematical modeling of flow through a finite elliptical orifice was computed using the open-source incompressible flow solver Nalu. Forty-five permutations of valve flow were characterized by varying valve orifice area (0.1, 0.3 and 0.5 cm^2), ellipse axis ratios (1:1, 2:1, 3:1, 5:1, and 10:1), and max velocity (400, 500 and 600 cm/s). Computed hemispherical flow contours scaled to true orifice flow (Qc/Qo) and scaled computed area to true orifice area (Ac/Ao) were plotted against distance from the orifice scaled to a circular orifice with equivalent orifice area. Results: Qc/Qo and Ac/Ao for each ellipse axis ratio when plotted against normalized orifice distance produced the same curves for each permutation of valve orifice area and max velocity. Plotting Qc/Qo (or Ac/Ao) against va/vo reveals marginal underestimation of flow with physiologic elliptical axis ratios of 2:1 and 3:1 against a circular orifice with axis ratios of 1:1 (Figure 1). Conclusions: The added error in using PISA to approximate flow through an elliptical mitral valve orifice area is minimal compared to traditional assumptions of a circular mitral valve orifice.

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Effect of altering left ventricular volume on mitral valve orifice area during exercise

Journal of the American College of Cardiology ◽

10.1016/0735-1097(91)91242-7 ◽

1991 ◽

Vol 17 (2) ◽

pp. A69

Author(s):

Ann Walling ◽

Angelique Foster ◽

Kent L. Richards ◽

Michael H. Crawford ◽

Scott R. Cannon ◽

...

Keyword(s):

Mitral Valve ◽

Left Ventricular Volume ◽

Ventricular Volume ◽

Left Ventricular ◽

Orifice Area ◽

Valve Orifice ◽

Valve Orifice Area

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Direct Assessment of Normal Mechanical Mitral Valve Orifice Area by Real-Time 3D Echocardiography

JACC Cardiovascular Imaging ◽

10.1016/j.jcmg.2011.06.024 ◽

2012 ◽

Vol 5 (5) ◽

pp. 478-483 ◽

Cited By ~ 6

Author(s):

Selim R. Krim ◽

Rey P. Vivo ◽

Ankit Patel ◽

Jiaqiong Xu ◽

Stephen R. Igo ◽

...

Keyword(s):

Mitral Valve ◽

Real Time ◽

3D Echocardiography ◽

Orifice Area ◽

Direct Assessment ◽

Valve Orifice ◽

Valve Orifice Area

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Reliability and reproducibility of two dimensional echocardiographic measurement of the stenotic mitral valve orifice area

The American Journal of Cardiology ◽

10.1016/0002-9149(79)90014-6 ◽

1979 ◽

Vol 43 (3) ◽

pp. 560-568 ◽

Cited By ~ 188

Author(s):

Randolph P. Martin ◽

Harry Rakowski ◽

Jay H. Kleiman ◽

William Beaver ◽

Elizabeth London ◽

...

Keyword(s):

Mitral Valve ◽

Two Dimensional ◽

Orifice Area ◽

Valve Orifice ◽

Echocardiographic Measurement ◽

Valve Orifice Area

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Impact of 3D echocardiography on grading of mitral stenosis and prediction of clinical events

Echo Research and Practice ◽

10.1530/erp-18-0031 ◽

2018 ◽

pp. 105-111 ◽

Cited By ~ 2

Author(s):

C Bleakley ◽

M Eskandari ◽

O Aldalati ◽

K Moschonas ◽

M Huang ◽

...

Keyword(s):

Mitral Valve ◽

Clinical Outcomes ◽

Mitral Stenosis ◽

Primary Outcome Measure ◽

Orifice Area ◽

Clinical Events ◽

2D Echocardiography ◽

Balloon Valvotomy ◽

2D And 3D ◽

Valve Orifice Area

Background The mitral valve orifice area (MVOA) is difficult to assess accurately by 2D echocardiography because of geometric assumptions; therefore, 3D planimetry may offer advantages. We studied the differences in MVOA measurements between the most frequently used methods, to determine if 3D planimetry would result in the re-grading of severity in any cases, and whether it was a more accurate predictor of clinical outcomes. Methods This was a head-to-head comparison of the three most commonly used techniques to grade mitral stenosis (MS) by orifice area and to assess their impact on clinical outcomes. 2D measurements (pressure half-time (PHT), planimetry) and 3D planimetry were performed retrospectively on patients with at least mild MS. The clinical primary endpoint was defined as a composite of MV balloon valvotomy, mitral valve repair or replacement (MVR) and/or acute heart failure (HF) admissions. Results Forty-one consecutive patients were included; the majority were female (35; 85.4%), average age 55 (17) years. Mean and peak MV gradients were 9.4 (4) mmHg and 19 (6) mmHg, respectively. 2D and 3D measures of MVOA differed significantly; mean 2D planimetry MVOA was 1.28 (0.40) cm2, mean 3D planimetry MVOA 1.15 (0.29) cm2 (P = 0.003). Mean PHT MVOA was 1.43 (0.44) cm2 (P = 0.046 and P < 0.001 in comparison to 2D and 3D planimetry methods, respectively). 3D planimetry reclassified 7 (17%) patients from mild-to-moderate MS, and 1 (2.4%) from moderate to severe. Overall, differences between the two methods were significant (X2, P < 0.001). Only cases graded as severe by 3D predicted the primary outcome measure compared with mild or moderate cases (odds ratio 5.7). Conclusion 3D planimetry in MS returns significantly smaller measurements, which in some cases results in the reclassification of severity. Routine use of 3D may significantly influence the management of MS, with a degree of prediction of clinical outcomes.

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