Pulse wave velocity (PWV) is considered as “the gold standard” to assess arterial stiffness. However, PWV is very dependent of blood pressure (BP) and is affected by anaesthesia, largely used in animal experimentation. Thus, the goals of the present study were: 1) To validate the PWV measurement in awake unrestrained rats using a new telemetry implant from Data Science International equipped with two pressures probes. 2) To measure PWV at different BP levels by using the circadian change of BP during the day or after acute BP reduction.

One catheter was placed in aortic arch and the other in abdominal aorta at the level of iliac bifurcation in Wistar Kyoto rats (18weeks-old, n=5). Hemodynamic parameters were recorded for 24h during baseline period and during an acute decrease in BP induced by diltiazem (100mg/kg/po). PWV was calculated by using the foot-to-foot method.

This new implant allows to measure heart rate, BP, BP amplification and PWV (Table1). The changes in PWV due to circadian or pharmacological changes in BP are shown in Fig.1. Both conditions exhibit similar linear regressions, allowing the assessment of PWV at different BP levels and thus independently of the BP.

Figure 1

Relationship between PWV and MBP during circadian change of BP or acute administration of diltizem on 24h period. PWV : Pulse Wave Velocity, MBP : Mean Blood Pressure

In conclusion, we show for the first time that the evaluation of arterial stiffness dependent and independent of the BP in chronically instrumented awake unrestrained rats is now possible. It will be a good tool to assess the effects of drugs on arterial wall stiffness.