How do pressure gradient vs. flow relationships characterize the physiology of a severely stenotic aortic valve before and after transcatheter valve implantation?
The concept of 'valvular fractional flow reserve' during dobutamine stress may better characterize aortic valve fluid dynamics and explain exertional symptoms in patients with moderate resting aortic stenosis.
Pressure loss vs. flow curves offer a fundamental fluid dynamic synthesis for describing aortic valve pathophysiology. Severe AS does not consistently behave like an orifice (as suggested by Gorlin) or a resistor, whereas TAVI devices behave like a pure resistor. During peak dobutamine, the ratio of aortic to left ventricular pressures during systolic ejection provides a 'fractional flow reserve' of the aortic valve that closely approximates the complex, changing fluid dynamics. Because resting assessment cannot reliably predict stress haemodynamics, 'valvular fractional flow' warrants study to explain exertional symptoms in patients with only moderate AS at rest.
Johnson et al. (Fri,) studied this question.