Transaortic Gradient is Pressure-Dependent in a Pulsatile Model of the Circulation
Renato Razzolini MD, Gino Gerosa MD, Loira Leoni MD, Dino Casarotto MD,
Raffaello Chioin MD, Sergio Dalla-Volta MD

Although the transvalvular gradient is described as flow-dependent, pressure-dependence of the gradient, irrespective of flow, has never been demonstrated. The Sheffield pulse duplicator fitted with an X-Cell 21 porcine valve mounted in the aortic position was used. Transaortic gradient was measured at a rate of 80 beats/min, with flow at 2, 5 or 8 l/min; systemic pressure was set up to 200 mmHg by adjusting peripheral resistances manually. Valve area was computed with the Gorlin formula. For each flow, the transvalvular gradient increased linearly with pressure, and computed area decreased. The slope of pressure-gradient relation was independent of flow. Thus, the transaortic gradient depends on flow, but is pressure-dependent. This should be considered when evaluating aortic stenosis, especially in hypertensive and hypotensive states.