| Planimetry by 2D echo (cm2) | |
|---|---|
| Tracing mitral orifice using 2D echo | |
| Concept: | Direct measurement of anatomic MVA. |
| Advantages: | Accuracy; Independence from other factors; Easy to obtain. |
| Disadvantages: | Experience required; Not always feasible (poor acoustic window, severe valve calcification) |
| Pressure half-time (cm2) | |
| 220 / T1/2 | |
| Concept: | Rate of decrease of transmitral flow is inversely proportional to MVA. |
| Advantages: | Easy to obtain. |
| Disadvantages: | Dependence on other factors (AR, LA compliance, LV diastolic function...) |
| Mean gradient (mmHg) | |
| ΔP ∑4v2 / Ν | |
| Concept: | Pressure gradient calculated from velocity using the Bernoulli equation. |
| Advantages: | Easy to obtain. |
| Disadvantages: | Dependent on heart rate and flow conditions. |
| Systolic pulmonary artery pressure (mmHg) | |
| sPAP = 4v2Tricuspid + RA Pressure | |
| Concept: | Addition of RA pressure and maximum gradient between RV and RA. |
| Advantages: | Obtained in most patients with MS. |
| Disadvantages: | Arbitrary estimation of RA pressure; No estimation of pulmonary vascular resistance. |
| Continuity equation (cm2) | |
| MVA = (CSALVOT × VTIAortic)/VTIMitral | |
| Concept: | Volume flows through mitral and aortic orifices are equal. |
| Advantages: | Independence from flow conditions. |
| Disadvantages: | Multiple measurements (sources of errors); Not valid if significant AR or MR. |
| PISA (cm2) | |
| MVA = π(r2)(VAliasing) / PeakVMitral × α/180° | |
| Concept: | MVA accessed by dividing mitral volume flow by the maximum velocity of diastolic mitral flow. |
| Advantages: | Independence from flow conditions. |
| Disadvantages: | Technically difficult. |
| Mean gradient & systolic pulmonary artery pressure at exercise (mmHg) | |
| ΔP ∑4v2 / Ν sPAP = 4v2Tricuspid + RA Pressure | |
| Concept: | Assessment of gradient and sPAP for increasing workload. |
| Advantages: | Incremental value in assessment of tolerance. |
| Disadvantages: | Experience required; Lack of validation for decision-making. |
AR, aortic regurgitation; CSA, cross-sectional area; DFT, diastolic filling time; LA, left atrium; LV, left ventricle; LVOT, left ventricular outflow tract; MR, mitral regurgitation; MS, mitral stenosis; MVA, mitral valve area; MVres, mitral valve resistance; ΔP, gradient; sPAP, systolic pulmonary artery pressure; r, the radius of the convergence hemisphere, RA, right atrium; RV, right ventricle; T1/2, pressure half-time; v, velocity; VTI. velocity time integral; N, number of instantaneous measurements.