Perspective Chapter: Evolution of Techniques to Assess Vascular Impedance in Patients with Aortic Stenosis

Abstract

Aortic stenosis (AS) once was conceptualized as a mechanical problem with a fixed left ventricular (LV) afterload because of an obstructive valve. With time, there has been growing recognition that AS functions more like a series circuit, with important contributions from the ventricle through to the vasculature. Emerging evidence suggests that higher blood pressure and increased arterial stiffness, synonymous with vascular aging, increases global LV afterload in patients with AS. This in turn, has adverse consequences on quality-of-life measures and survival. Although traditional methods have emphasized measurement of the transvalvular pressure gradient, focusing on valvular hemodynamics alone may be inadequate. By definition, total vascular load of the human circulation includes both steady and pulsatile components. Steady load is best represented by the systemic vascular resistance whereas pulsatile load occurs because of wave reflections and vascular stiffness, and is often referred to as the valvulo-arterial impedance. In the following Review, we evaluate existing and upcoming methods to assess vascular load in patients with AS in order to better understand the effects of vascular aging on this insidious disease process.