P5.1 FROM AORTIC FLOW VELOCITY TO CENTRAL PRESSURE: A NON-INVASIVE PROOF OF CONCEPT

• Main Authors: Samuel Vennin*, Jordi Alastruey, Phil Chowienczyk
• Format: Article
• Language: English
• Published: Atlantis Press 2015-11-01
• Series: Artery Research
• Online Access: https://www.atlantis-press.com/article/125930631/view

Estimation of aortic and left ventricular (LV) pressure usually requires measurements that are difficult to acquire during the imaging required to obtain concurrent LV dimensions essential for determination of LV mechanical properties. We describe a novel method for deriving aortic pressure from the aortic flow velocity. The target pressure waveform is divided into an early systolic upstroke and a diastolic decay, interposed by a late systolic portion described by a second-order polynomial. Pulse wave velocity (PWV), mean arterial pressure, diastolic pressure and diastolic decay are required inputs for the algorithm. The algorithm was tested using a) pressure data derived theoretically from pre-specified flow waveforms and properties of the arterial tree using a single-tube 1-D model of the arterial tree and b) experimental data acquired from a pressure/Doppler flow velocity transducer placed in the ascending aorta (n=18, mean+/−SD, age: 63+/−11 years, aortic BP: 136+/−23 / 73+/−13 mmHg) at the time of cardiac catheterisation. For experimental data, PWV was calculated from measured pressures/flows and mean, diastolic pressures and diastolic decay were taken from measured pressure. Pressure reconstructed from measured flow agreed well with theoretical pressure: mean+/−SD root mean square (RMS) error 0.7+/−0.1 mmHg. Similarly, for experimental data, pressure reconstructed from measured flow agreed well with measured pressure (mean RMS error 2.4+/−1.0 mmHg). First systolic shoulder and systolic peak pressures were also accurately rendered (mean+/−SD difference 1.4+/−2.0 mmHg for peak systolic pressure). This is the first non-invasive derivation of aortic pressure based on fluid dynamics (flow and wave speed) in the aorta itself.