Systemic pressure does not directly affect pressure gradient and valve area estimates in aortic stenosis in vitro.

Abstract

Hypertension is a frequent finding in patients with aortic stenosis (AS). However, controversial data about the influence of systemic blood pressure on the quantification of AS have been published. Various models of AS (plates and biological valves) were studied in an in vitro circuit. Valve areas were calculated with the Doppler continuity equation and the Gorlin formula. Systolic systemic pressures were increased from 80 to 200 mmHg while flow rates were maintained constant. In addition, a computational fluid dynamics (CFD) model was constructed to test the effect of systemic pressures on pressure gradient and valve area estimates. When systemic pressure was raised, pressure gradients as well as valve areas did not change (mean difference 3.4 +/- 1.8 mmHg, range 0.4-6.8 mmHg; mean difference 0.01 +/- 0.03 cm(2), range -0.02 to 0.05 cm(2)). By multivariable analysis, neither valve area nor pressure gradient were independently affected by systemic pressure. In addition, CFD analysis revealed no effect of systemic pressure on pressure gradient and valve area. Our results suggest that blood pressure itself does not directly affect pressure gradients and valve area estimates in AS. Thus, when observed in vivo, these changes are most likely due to afterload-related variations of ejection fraction and, therefore, flow rate.