Valvular structure

Heart Valves

Aortic Valve Area (AVA)

The aortic valve area (AVA) must be reduced to roughly one-fourth its normal size before any significant changes occur in hemodyanmics. AVA can be measured by cardiac catheterization, Doppler echo-cardiography or imaging to assess aortic stenosis severity. The diagnostic techniques provide the Gorlin area, the effective orifice area (EOA) and the geometric orifice area (GOA), respectively. IGOA represents the geometric area of the valve orifice, whereas EOA is the minimal cross-sectional area of the downstream jet. It should be noted that the relationship between EOA and GOA is EOA = C<sub>c</sub> × GOA, where C<sub>c</sub> is the contraction coefficient and is highly dependent upon the valve inflow shape(Garcia and Kadem 2006).

<figure> <img src="/latex/images/heart_valve/AVA.png" id="fig:AVA" alt="Different methods used to estimate aortic valve area (Garcia and Kadem 2006)." /><figcaption aria-hidden="true">Different methods used to estimate aortic valve area <span>(Garcia and Kadem 2006)</span>.</figcaption> </figure>

For echo-cardiography, AVA can be estimated using the continuity equation that through the ratio of stroke volume and estimate of velocity-time integral (VTI)(Yap et al. 2007; O’Brien et al. 2009). For CMR, AVA can be be calculated in similar manner. However, the approaches to calculate the stroke volume and VTI vary for in different ways.

  • Definition: The area of aortic valve.

  • Calculation: Let VTI<sub>LVOT</sub> be the velocity-time integral for left ventricular outflow tract (LVOT), VTI<sub>AoV</sub> be that sampled just above the stenotic aortic valve. VTI<sub>peak</sub> is the VTI at the aortic flow velocity peak.

    1. Continuity equation using echo: AVA<sub>echo</sub> = echo SV/VTI<sub>AoV</sub> = (VTI<sub>LVOT</sub>×A<sub>LVOT</sub>)/VTI<sub>AoV</sub> (Yap et al. 2007; O’Brien et al. 2009)

    2. Using volumetric stroke volume in CMR: AVA<sub>vol</sub> = CMR SV/VTI<sub>peak</sub> where CMR SV is determined using cine (O’Brien et al. 2009; De Rubeis et al. 2019).

    3. Using phase contrast estimate of flow in CMR: AVA<sub>PC</sub> = PC SV/VTI<sub>peak</sub> where PC SV can be obtained through summation of the net forward flow through the cardiac cycle (O’Brien et al. 2009; De Rubeis et al. 2019).

  • Acquisition Type: LAX, SAX, PC

  • Reference Range:

    StudyCohort SizeGenderReference Value (cm<sup>2</sup>)Note
    (Kany et al. 2023)22807male2.5-3.9
    24416female2.0-3.1
    (Cotella et al. 2023)977male1.98-4.84
    926female1.57-3.68
    (Defrance et al. 2012)212.38-3.0710 males, 11 females

  • Clinical Associations: Severe aortic stenosis (AS) is defined as AVA typically smaller than 1cm<sup>2</sup> according to AHA guidelines(Nishimura et al. 2014).

  • ICC: 0.71

Mitral and Tricuspid Annular Diameter

  • Definition: The diameter of mitral annular and tricuspid annular.

  • Acquisition Type: LAX

  • Reference Range:

    • Mitral, end-diastolic:

      StudyCohort SizeGenderReference Value (cm)Note
      (Ricci et al. 2020)328male2.4-4.1measured in 4CH
      328male2.2-3.6measured in 3CH
      328male2.9-4.2measured in 2CH
      393female2.4-3.6measured in 4CH
      393female1.9-3.3measured in 3CH
      393female2.6-3.8measured in 2CH

    • Mitral, end-systolic:

      StudyCohort SizeGenderReference Value (cm)Note
      (Ricci et al. 2020)328male2.4-4.3measured in 4CH
      328male2.6-4.1measured in 3CH
      328male2.9-4.4measured in 2CH
      393female2.4-3.8measured in 4CH
      393female2.3-3.8measured in 3CH
      393female2.6-3.9measured in 2CH

    • Tricuspid, end-diastolic:

      StudyCohort SizeGenderReference Value (cm)Note
      (Ricci et al. 2020)328male2.3-4.1measured in 4CH
      393female2.1-3.5measured in 4CH

    • Tricuspid, end-systolic:

      StudyCohort SizeGenderReference Value (cm)Note
      (Ricci et al. 2020)328male2.3-4.2measured in 4CH
      393female2.0-3.6measured in 4CH

  • Clinical Associations: Lone atrial fibrillation (AF) is associated with annular dilation in both mitral and tricuspid valves (Zhou et al. 2002).

Tenting Area*

Due to papillary muscle displacement, increased tethering forces on mitral chordae and annular dilatation, mitral valve leaflets lose their coaptation and take shape of a tent during systole. Typically, the triangular area between mitral annulus and tented leaflets is described as MV tenting area (von Stumm et al. 2021). The parameter is not unique to the mitral valve and can likewise be applied to the tricuspid valve, where leaflet tethering and annular dilatation similarly contribute to functional regurgitation.

<figure> <img src="/latex/images/heart_valve/annular_dimension.png" id="fig:annular_dimension" alt="Mitral annular and tricuspid annular dimensions and tethering indices" /><figcaption aria-hidden="true">Mitral annular and tricuspid annular dimensions and tethering indices</figcaption> </figure>

  • Definition: The triangular area enclosed between the annular plane and the tented leaflets of the mitral or tricuspid valve during systole.

  • Acquisition Type: LAX

  • Reference Range:

    • Mitral:

      StudyCohort SizeGenderReference Value (cm<sup>2</sup>)Note
      (Ricci et al. 2020)328male0.6-2.1measured in 3CH
      393female0.6-1.8measured in 3CH

    • Tricuspid:

      StudyCohort SizeGenderReference Value (cm<sup>2</sup>)Note
      (Ricci et al. 2020)328male0.2-1.1measured in 4CH
      393female0.2-0.8measured in 4CH

  • Clinical Associations: Patients having tenting area of mitral valve larger than 3.4cm<sup>2</sup> are more likely to experience severe functional mitral regurgitation, more hospitalization and higher death rates (Karaca et al. 2011). Similarly, tenting area of tricuspid valve is higher in patients with tricuspid regurgitation (TR) (Sukmawan et al. 2007).

Tenting Height*

In addition to area, the tenting height provides a complementary geometric descriptor for both MV and TV. It is defined as the perpendicular distance from the annular plane to the point of leaflet coaptation, thereby quantifying the vertical component of tethering. Like tenting area, tenting height has been widely applied in the evaluation of functional mitral and tricuspid regurgitation, and both parameters carry prognostic value in predicting surgical and trans-catheter outcomes.

  • Definition: The perpendicular distance from the annular plane to the point of leaflet coaptation in the mitral or tricuspid valve.

  • Acquisition Type: LAX

  • Reference Range:

    • Mitral:

      StudyCohort SizeGenderReference Value (cm)Note
      (Ricci et al. 2020)328male0.4-1.0measured in 3CH
      393female0.3-0.9measured in 3CH

    • Tricuspid:

      StudyCohort SizeGenderReference Value (cm)Note
      (Ricci et al. 2020)328male0.1-0.6measured in 4CH
      393female0.1-0.5measured in 4CH

  • Clinical Associations: Tenting height of mitral valve is longer in patients with ischemic mitral regurgitation than control subjects (Watanabe et al. 2005). The maximum and mean tenting lengths are longer in patients with tricuspid regurgitation as well (Sukmawan et al. 2007).

Anterior Mitral Leaflet Length*

<figure> <img src="/latex/images/heart_valve/AML.png" id="fig:AML" alt="The atrioventricular valvular entrance of the ventricles (Standring et al. 2005)." /><figcaption aria-hidden="true">The atrioventricular valvular entrance of the ventricles <span>(Standring et al. 2005)</span>.</figcaption> </figure>

  • Definition: The length of the anterior mitral leaflet (AML) from the most distal part of the leaflet up to its insertion during mid- or end-diastole.

  • Acquisition Type: LAX (3CH)

  • Reference Range:

    StudyCohort SizeGenderReference Value (cm)Note
    (Ricci et al. 2020)328male1.8-2.5measured in 3CH
    393female0.9-1.3measured in 3CH

  • Clinical Associations: Tertiles of AML length shows proportional increase with the amount mitral valve prolapse (MVP)-associated MR (Delling et al. 2010). The AML length can also help identify individuals at higher risk for left ventricular outflow tract obstruction (LVOTO) (Sahota et al. 2022), especially at mid-systole but not end-diastole.

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