Hemodynamics, Doppler, and Quantitative Assessment
Core equations
The simplified Bernoulli equation, ΔP = 4v², converts peak velocity to peak gradient; mean gradients are traced, not calculated. Stroke volume is cross-sectional area times velocity-time integral, and cardiac output is stroke volume times heart rate. The continuity equation gives aortic valve area as (LVOT area × LVOT VTI) ÷ aortic VTI. Proximal isovelocity surface area gives regurgitant orifice area as 2πr² × Nyquist velocity ÷ peak regurgitant velocity, with regurgitant volume as EROA × VTI.
Right heart and pulmonary pressures
Right ventricular systolic pressure equals 4 × (TR peak velocity)² plus estimated right atrial pressure from IVC size and collapsibility. Pulmonary acceleration time and the shape of the RV outflow tract envelope refine the estimate. RV function is judged by TAPSE, fractional area change, and tricuspid annular systolic velocity.
Diastolic function
Use E/A ratio, deceleration time, septal and lateral annular e′ velocities, E/e′, TR velocity, and left atrial volume index. Normal E/e′ is ≤14, septal e′ ≥7 cm/s, lateral e′ ≥10 cm/s, TR velocity ≤2.8 m/s, and LAVI ≤34 mL/m². Average values over three cycles, five in atrial fibrillation.
Traps
Continuous wave is needed for high velocities and gives the peak, not the location; pulsed wave localizes but aliases. An insonation angle above 20 degrees underestimates velocity - correct or reposition. Overgained spectral Doppler broadens the envelope and falsely raises gradients. Do not mistake the flutter of aortic regurgitation for the ejection envelope.
Rule of thumb
RVSP ≈ 4V² + 5 mmHg when the IVC is small and collapsing, +10 when intermediate, +15–20 when dilated and plethoric.