Overview
Gorlin uses flow, heart rate, flow duration and the mean simultaneous pressure gradient. Aortic Hakki uses peak LV minus peak aortic pressure; mitral Hakki uses the mean diastolic gradient. The formulas are not interchangeable with Doppler peak gradients.
Ten nominal beats are averaged. Areas are calculated from synthetic traces, not measured anatomic areas. Low flow, regurgitation and irregular rhythm affect interpretation; Hakki is less reliable outside 60–100 bpm. Mechanical support and shunts require valve-specific flow, so a net-CO area is withheld.
Sources: Dean and Kern, Measuring Valve Gradients and Areas (2022), in Works cited.