P140 Arterial Wave Dynamics in the Horse: Insights Obtained from A 1D Arterial Network Model Simulation

Background Relatively little is known about equine arterial hemodynamics because it is technically and ethically challenging to investigate a large number of arteries. Pulsed-wave Doppler images of arterial flow velocities typically display patterns of a higher oscillatory nature than in humans, but the background of these oscillations is not well understood. The aim of this study is to gain insight into equine arterial hemodynamics and physiology through 1D arterial network simulations. Methods Anatomical data of lengths, diameters and branching angles collected post-mortem from five horses, were used as the input for a previously validated (in humans) 1D arterial network model [1]. Cardiac and arterial parameters were tuned to equine physiology at rest (heart rate 40 bpm, cardiac output 36 l/min, mean arterial pressure 92 mmHg). Pressure and flow waveforms were simulated for the ascending aorta, right common carotid and median (in the front limbs) arteries. Simulated flow velocities were compared with ultrasound data from one horse and wave intensity analysis (WIA) was used to study wave dynamics. Results Figure 1 shows that simulated flow velocities are quantitatively close to ultrasound data. Ultrasound images show a high level of oscillations, also present in the simulations. The most prominent feature revealed by WIA is the existence of a mid-systolic forward expansion wave and prominent wave activity throughout diastole. Conclusions Initial model simulations indicate a great activity of wave reflection and a quantitative match of intra-arterial waveforms with ultrasound data. Simulations are also able to capture the oscillatory patterns observed in ultrasound data. Figure 1 A: Pressure signals and forward (P+) and backward (P-) components. B: Wave Intensity analysis. C: ln-vivo measurements from one horse compared with model simulations (FCW: forward compression wave. FEW: forward expansion wave, BCW: backward compression wave, dl: wave intensity, dP: change in pressure, t : normalized time).