In estimating RVSP, you combine the Doppler-derived pressure gradient with the right atrial pressure by adding them. The velocity of the tricuspid regurgitation jet gives the pressure difference between the right ventricle and right atrium through the simplified Bernoulli equation: ΔP = 4v^2. This gradient represents how much pressure the RV must generate above the RA during systole. To obtain the actual right ventricular systolic pressure, you add the estimated right atrial pressure to that gradient: RVSP ≈ 4(TRV)^2 + RAP. So the final estimate comes from summing the two terms, not subtracting, multiplying, or dividing. For example, if TRV is 3 m/s, the gradient is 36 mmHg; adding an RAP around 5–10 mmHg gives an RVSP in the ~41–46 mmHg range.

Vena contracta width is used because it measures the narrowest part of the regurgitant jet right after it exits the aortic valve, which reflects the size of the regurgitant orifice. The wider this narrowest region, the more blood is leaking back into the left ventricle, so it directly correlates with the severity of aortic regurgitation. In practice, a small width suggests mild AR, a mid-range width suggests moderate AR, and a wide width indicates severe AR. Example thresholds commonly used are roughly under 3 mm for mild, about 3–6 mm for moderate, and greater than around 6 mm for severe AR, though exact cutoffs can vary slightly by protocol. This makes vena contracta width a straightforward, reproducible metric on color Doppler. Other measurements exist, but they serve different purposes. Coronary flow velocity reserve assesses coronary microvascular function, not AR severity. LV end-diastolic volume shows remodeling from chronic AR but does not quantify how severe the leak is at the valve. Aortic root diameter indicates the size of the aortic root and potential etiologies of AR, not the current regurgitant strength.

PISA relies on flow convergence proximal to a regurgitant orifice. As blood accelerates toward the orifice, the velocity increases until it reaches a defined aliasing velocity, creating an isovelocity surface whose near-hemispherical shape is the basis for a simple flow calculation. By measuring the radius r of that first-encountered aliasing surface on color Doppler and using the known aliasing velocity Va, you estimate the flow rate through the orifice with Q = 2π r^2 Va. This flow rate is then related to the regurgitant jet by dividing by the peak velocity of the regurgitant jet Vmax measured with continuous-wave Doppler, giving the effective regurgitant orifice area: EROA = Q / Vmax = (2π r^2 Va) / Vmax. In practice, this means you place the sample window to capture the flow convergence, measure the radius at the first aliasing contour, and apply the formula to obtain EROA and, subsequently, regurgitant volume. Common pitfalls to avoid include assuming the flow convergence forms a perfect hemisphere, since actual flow can be distorted by jet direction, LV geometry, or multiple jets; eccentric or laminar jets and misalignment of the Doppler beam can bias the measured radius and Va, leading to under- or overestimation of EROA; and mistimed or incorrect placement of the measurement plane or use of an inappropriate aliasing velocity can distort Q. Being mindful of these factors helps ensure the PISA estimate reflects the true regurgitant flow.

The measurement used to calculate the LVOT area in the continuity equation is the LVOT diameter. The cross-sectional area of the LVOT is derived from this diameter with the formula area = π(D^2)/4, because stroke volume equals LVOT area times the LVOT velocity-time integral (VTI). The LVOT diameter is measured in the parasternal long-axis view, inner-edge to inner-edge, just below the aortic valve, in systole. The LVOT velocity gives the VTI for flow, not the area. The aortic root diameter and the RVOT diameter aren’t used in this LVOT area calculation. Since the area scales with the square of the diameter, tiny measurement errors in the LVOT diameter can lead to large errors in the calculated aortic valve area.