Biphasic relationship between arterial pressure and aortic pulse wave velocity in normotensive rats

Background. Arterial stiffness is an independent predictor of cardiovascular risk. Pulse wave velocity (PWV) is a surrogate of arterial stiffness and is dependent on mean arterial pressure (MAP). The presented study aimed to characterise arterial function over a wide range of MAP by means of quantification of the PWV – MAP relationship. Methods. Experiments were performed on 6 anaesthetised (Urethane, 1.3 g/kg, ip) Wistar Kyoto rats by recording beat-to-beat PWV and MAP using a high fidelity 2.5F catheter with dual pressure sensors 5 cm apart, introduced via the femoral artery and positioned in the descending aorta. Pressure was increased and decreased by intravenous infusion of phenylepherine and sodium nitroprusside respectively. PWV - MAP phase plots were obtained for pressures between 40 and 160 mmHg. Results. Analysis of PWV-MAP phase plots shows a consistent biphasic pattern with two significantly different slopes in a low pressure (40 – 100 mmHg, 0.80.2 m/s/ mmHg) and high pressure range (100 – 160 mmHg, 150.9 m/s/ mmHg, p0.05). The intersection of these two linear regression lines occurs at critical pressure level (Pc) (11213.8 mmHg). Pc was significantly higher than the resting (anaesthetised) MAP (83.515.3 mmHg, p0.05). Conclusion. Both Pc and slopes of the PWV-MAP phase plots represent intrinsic characteristics of aortic distensibility. This may be used to quantify arterial function in the rat aorta with normal and altered arterial wall properties.