Aortofemoral transfer function: a method to determine the instantaneous aortic valve gradient in aortic valve...

Area of Science:

• Cardiovascular Physiology
• Medical Imaging and Diagnostics

Background:

• Accurate aortic valve gradient measurement in aortic stenosis often requires simultaneous ascending aorta and left ventricular pressure recordings.
• Femoral artery pressure is typically an inadequate substitute for ascending aorta pressure.
• Aortic pressure can be derived from femoral pressure using a determined aortofemoral transfer function.

Purpose of the Study:

• To evaluate the utility of synthesized ascending aorta pressure, derived from femoral artery pressure via an aortofemoral transfer function, for assessing aortic valve stenosis.

Main Methods:

• Simultaneous recording of femoral and ascending aorta pressures.
• Determination of the aortofemoral transfer function using Fourier components.
• Calculation of synthesized ascending aorta pressure from femoral pressure using the transfer function.

Main Results:

• Synthesized ascending aorta pressure waveforms closely matched directly recorded ones.
• Mean aortic valve gradients calculated from synthesized pressure showed strong correlation with direct measurements (r=0.98).
• Valve areas (r=0.93) and resistances (r=0.98) also correlated well between the two methods.

Conclusions:

• Accurate aortic valve gradients can be rapidly calculated using femoral artery pressure as a surrogate for ascending aorta pressure with current technology.
• This technique minimizes the necessity and associated risks of using multiple catheters for gradient determination.