Estimation of aortic pulse pressure using Fourier velocity encoded M-mode MR

To use a simplified hemodynamic model and Fourier-encoded velocity data to measure pulse pressure (PP) in the descending aorta.

A one-dimensional, cylindrically localized pulse sequence with Fourier velocity encoding (FVE) was used to obtain time-dependent velocity distributions along the descending aorta. Numerical evaluation of a simplified hemodynamic model, based on a cross-sectionally averaged form of the mass conservation equation, allowed estimation of the average pressure waveform and PP along 6-cm-long segments located within the descending aorta. Magnetic resonance (MR)-derived pressures were compared against applanation tonometry (AT) performed in healthy subjects (n = 18) and intravascular pressure measurements (IVPM) obtained in patients (n = 4) undergoing diagnostic cardiac angiography and then found to be either normal or with clinically insignificant coronary artery disease.

The root mean square (RMS) error between MR- and AP-derived pressure waveforms was 11.7 ± 5.8%. With respect to IVPM, the RMS error ranged from 4.2% to 14.7%. In terms of pulse pressures, there was good agreement with both AT (bias = 0.99 mmHg; 95% limits of agreement (LOA) = [-5.0 to 7.0 mmHg]; range = 12.0 mmHg) and IVPM (bias = -1.82 mmHg; 95% LOA = [-7.2 to 3.5 mmHg]; range = 10.7 mmHg).

FVE M-mode and numerical evaluation of a simplified flow model can be used to estimate central pulse pressures noninvasively and accurately with respect to well-established gold standards.