SHA24/038006

Assessment of Mitral Valve Area by 3D Echocardiography in Rheumatic Mitral Stenosis; Validation of offline 3D Planimetry Measurements

A. Mohamed1, A. Omran1, MA. Hussein2 (1) National Guard Hospital, King Abdul-Aziz Cardiac Center (KACC), Riyadh, Saudi Arabia (2) King Abdullah International Medical Research Center, Riyadh, Saudi Arabia

Introduction • Rheumatic mitral valve disease is the most frequent etiology of MS. • Rheumatic mitral valve disease causes thickening and shortening of the leaflets and chordae, fusion of the commissures with "doming" of the leaflets in diastole.

These damages restrict the valve opening and create mitral stenosis.

• MS is an obstacle to LV diastolic filling, leading to elevation of left atrium pressure and left atrium dilatation. The upstream effect on the right heart is elevation of right ventricle after-load and pulmonary hypertension.

How to assess mitral stenosis? • Indices of Stenosis Severity • Pressure gradient (Level 1). The estimation of the diastolic pressure gradient is derived from the trans-mitral velocity flow curve using the simplified Bernoulli equation P= 4v2. • Good correlation with invasive measurement using trans-septal catheterization.

Mitral gradient by CW Doppler in mitral stenosis

SAX view at MV level and papillary ms level

Disadvantages of Doppler gradient

• Mitral gradient by Doppler, is not the best marker of the severity of MS since it is dependent on the MVA as well as other factors that influence trans-mitral flow rate • Heart rate.

• Cardiac output.

• Associated MR

Mean mitral valve gradient in atrial fibrillation.

How to assess mitral stenosis?

• Pressure half-time (Level 1 Recommendation).

• T1/2 is defined as the time interval in milliseconds between the maximum mitral gradient in early diastole and the time point where the gradient is half the maximum initial value.

• The decline of the velocity of diastolic trans-mitral blood flow is inversely proportional to valve area (cm2), and MVA is derived using the empirical formula:

MVA=220 ⁄ T1⁄2

• T1/2 is obtained by tracing the deceleration slope of the Ewave on Doppler spectral display of trans-mitral flow and valve area is automatically calculated by the integrated software of currently used echo machines.

Estimation of mitral valve area using the pressure half-time method

Determination of Doppler pressure halftime (T1/2) with a bimodal, non-linear decreasing slope of the E-wave. The deceleration slope should not be traced from the early part (left), but using the extrapolation of the linear mid-portion of the mitral velocity profile (right).

Gonzalez M et al. Am J Cardiol 1987;60:327-32.

How to assess mitral stenosis? • LV diastolic filling rate, which is reflected by the deceleration slope of the E-wave, depends on: 1. MVA 2. Mitral pressure gradient in early diastole.

3. Left atrial compliance.

4. LV diastolic function (relaxation and compliance). • The empirically determined constant of 220 is in fact proportional to the product of net compliance, i.e. the combined compliance of left atrium and LV, and the square root of maximum trans-mitral gradient in a model that does not take into account active relaxation of LV. • The increase in mean gradient is frequently compensated by a decreased compliance, and this may explain the rather good correlation between T1/2 and other measurements of MVA in most series.

How to assess mitral stenosis?

• Limitations of PHT: • • • •

• 1.

2.

• •

After balloon mitral valvuloplasty.

Low left atrial compliance.

T1/2 is also shortened in patients who have associated severe AR. Impaired LV diastolic function difficult to assess because of complex and competing interactions between active relaxation and compliance as regards their impact on diastolic trans-mitral flow.

Early diastolic deceleration time: Is prolonged when LV relaxation is impaired.

Shortened in case of decreased LV compliance.

T1/2is not reliable to assess MVA in the elderly.

In patients with rheumatic MS with associated AS and hypertension and, thus, impaired diastolic function, the use of T1/2 may be unreliable and should be avoided.

How to assess mitral stenosis?

• MVA Planimetry (Level 1).

• Planimetry using 2D echocardiography of the mitral orifice has the advantage of being a direct measurement of MVA and, is not affected by 1. Flow conditions.

2. Cardiac chamber compliance.

3. or associated valvular lesions.

• Planimetry has been shown to have the best correlation with anatomical valve area as assessed on explanted valves1.

• For these reasons, planimetry is considered as the reference measurement of MVA2.

1. Faletra F et al.Measurement of mitral valve area in mitral stenosis: four echocardiographic methods compared with direct measurement of anatomic orifices. J Am Coll Cardiol 1996;28:1190-7.

2. Vahanian A et al. The Task Force on the Management of Valvular Heart Disease of the European Society of Cardiology. Eur Heart J 2007;28:230-68.

How to assess mitral stenosis?

• MVA Planimetry ( requirements) • Careful scanning from the apex to the base of the LV is required to ensure that the CSA is measured at the leaflet tips.

• The measurement plane should be perpendicular to the mitral orifice, which has an elliptical shape.

• Gain setting should be just sufficient to visualize the whole contour of the mitral orifice. Excessive gain setting may cause underestimation of valve area, in particular when leaflet tips are dense or calcified.

2D planimetric measurement of MVA

How to assess mitral stenosis?

• Limitations: • The performance of planimetry requires technical expertise.

• The measurement plane must be optimally positioned on the mitral orifice.

• In the particular case of degenerative MS, planimetry is difficult and mostly not reliable because of the orifice geometry and calcification present.

How to assess mitral stenosis? • Recent reports suggested that real-time 3D echo and 3D-guided biplane imaging is useful in optimizing the positioning of the measurement plane and, therefore, improving reproducibility. • It also improves the accuracy of planimetry measurement when performed by less experienced echocardiographers.

X plane view of rheumatic mitral valve.

Mitral valve area measuring using biplane 2D imaging. The 3D transducer allows simultaneous display of more than one 2D view. The advantage of this is the ability to confirm that the parasternal short axis view of the mitral orifice is in fact at the tip of the mitral leaflets.

Rheumatic mitral stenosis MPR mode.

Rheumatic mitral stenosis MPR mode.

Background • Measurements of MVA by(2D) planimetry and Doppler (PHT) remain the mainstay methods used in routine clinical practice.

3 dimensional transesophageal echocardiography, provides more improved accuracy and reproducibility over 2D methods in the assessment of mitral valve morphology.

Planimetry of the MVA by 3D echocardiography has only been done through multi-planar reconstruction of the mitral valve orifice.

However using offline 2D image calibration and measurement tools allows us to measure MVA by 3D planimetry.

Aim of the study To validate the feasibility and accuracy of performing offline planimetric measurement of mitral valve area (MVA) using 3D TEE. To compare 3D TEE with methods used routinely in clinical practice specifically (2D) planimetry and pressure half time (PHT)

Methods • A total of 45 patients with moderate to severe rheumatic mitral stenosis were referred for transthoracic and transesophageal (TEE) echocardiography 2D and 3D. • Offline planimetric measurement of MVA obtained from real time 3D TEE zoom views of the mitral valve from both left atrial (MVA 3DPLA) and left ventricular side (MVA 3DPLV) were compared to MVA by 2D planimetry and PHT.

Methods • MVA measurements (2Dplanimetry, doppler PHT and 3D planimetry) were reported by 2 independent experienced cardiologist.

• MV area measured by 3D TEE was compared to pressure half time and 2D planimetry using Altman and Bland methods and Shukla’s correlation.

• Interobserver variablity was compared across all three methods using pair-wise comparison F statistics.

Patients characteristics • 45 patients with moderate to severe rheumatic Mitral Stenosis.

• Females: 33 Males: 12 • 13 were assessed during or prior MBV • 22 were evaluated during or prior to valve surgery • 10 were being evaluated during other procedures e.g. cardioversion

Patients characteristics • • • • • • •

Mean age was 46 years (16 yrs -71yrs) Mean HR: 84 ( 52 B/min – 117 b/min) Mean systolic BP: 116 mm hg Mean diastolic BP: 71 mm hg Average weight: 75 KG (38 -130 KG) Average height: 159 cm (144-180 cm) Average BMI: 29.6 KG/m2 (18.8 – 58.56)

Patients characteristics • • • • • • • • • •

Mean MVA 3d planimetry LV side : 1.01 cm2 Mean MVA 3d planimetry LA side : 1.03 cm2 Mean MVA 2d planimetry: 1.23 cm2 Mean MVA PHT: 1.2 cm2 Mean transmitral gradient 14 mmhg (4-30 mmhg) Average Boston score: 8.36 Average MR grade: 1.27 Mean PASP: 53 mm hg Mean LA volume index: 58 ml/m2 Mean LVEF: 59%

Rheumatic mitral valve 3d planimetry LV side

MVA = 0.96

MVA by planimetry LA view

MVA = 0.93

MVA by planimetry LV view

Results • The Altman and bland analysis showed consistency among all three measurements methods. • 3DTEE showed the least variability across different observers compared to 2D planimetry and PHT, Mean difference 0.08, -0.15, and -.17 respectively.

Comparison of 3D TEE, 2D Planimetry and PHT

Difference

(3D TEE MVA - 2D Planimetry MVA)

Bland and Altman Scatter Plot for 2d and 3d LV Planimatery

Avergae

Average 3D TEE MVA and 2D Planimetry MVA

Altman Plot for 3D TEE and 2D Planimetry MVA

There is General agreement between the two methods.

The average gap in measurement is -.35 (SE= Âą 0.04) There is a tendency for bigger gap in measurement between the two methods when MVA area is large (r= 0.49, p< 0.0011)

Bland and Altman Scatter Plot for 3D and Pressure Half time

Difference

(3D TEE MVA â&#x20AC;&#x201C; Pressure Half Time MVA)

Comparison of 3D TEE, 2D Planimetry and PHT

Avergae

Average 3D TEE MVA and Pressure Half Time MVA Altman Plot for 3D TEE and Pressure half time MVA

There is General agreement between the two methods The average gap in measurement is -0.30 (SE= Âą 0.05) The gap between the two measurements appears to be uniform over the entire range of measurement (r= -0.12 , p= 0.4398

Inter-observer variability for 3D TEE, 2D Planimetry

Difference

(observer 1 – observer 2 MVA)

Bland and Altman Scatter Plot for inter-rater consistency for 3d Planimatery

Avergae

Average observer 1 and observer 2 MVA

3D TEE inter-observer variability

The inter-observer variability in measuring MVA by 3D TEE planimetry is much lower than 2D planimetry and PHT. The average gap in measurement for 3D TEE among the two observers is twice less ( 0.077±0.13) than that for 2D measurements (0.015±0.24).

Inter-observer variability for 3D TEE, 2D Planimetry

Difference

(observer 1 – observer 2 MVA)

Bland and Altman Scatter Plot for inter-rater consistency for 2d Planimatery

Avergae

Average observer 1 and observer 2 MVA

2D planimetry inter-observer variability

The inter-observer variability in measuring MVA by 3D TEE planimetry is much lower than 2D planimetry and PHT. The average gap in measurement for 3D TEE among the two observers is twice less ( 0.077±0.13) than that for 2D TEE (0.15±0.24).

Conclusions â&#x20AC;˘ In the assessment of mitral valve stenosis, the measurement of MVA by 3D TEE planimetry were accurate and reproducible in comparison to 2D planimetry and PHT. â&#x20AC;˘ Among all three measurements of MVA, 3D TEE planimetry showed the least interobserver variability across different observers. â&#x20AC;˘ Our study also shows that 3D TEE allows optimal alignment of the imaging planes of the mitral valve thus ensuring that the planimetry measurement performed at the appropriate level. Hence, 3D TEE should be the first choice for clinicians to assess mitral valve area among patients diagnoses with moderate to severe mitral stenosis

Limitations • In case of degenerative MS, 3D planimetry is difficult and mostly not reliable.

• Frame rate of the 3D echo is still not optimal.

• Using 3d TEE would not be feasible for followup of all patients with MS. • 3D TEE uses the machine lateral resolution as compared to axial resolution in trans thoracic echo, this tend to underestimate the measured areas.