Objectives: Large artery stiffening, a risk factor in cardiovascular diseases, can be evaluated in human and rats by pulse wave velocity and echotracking, but controversies remain regarding the roles of blood pressure (BP) and vascular wall properties. We studied these points with the echotracking device ArtLab in the hypertensive rat (SHR) treated with L-NAME (SHRLN) to reduce nitric oxide levels.

Methods: In anaesthetized normotensive rats (WKY), SHR and SHRLN 20 weeks old, aortic BP is recorded via a catheter and diameter via the ArtLab ultrasound probe, in a motion mode to detect pulsatile displacement of aortic walls (distension). Data are analysed via a Matlab software.

Results: Compliance and distensibility are decreased in SHRLN (<SHR<WKY) and stiffness index increased. From distension-pressure loop curves, ascending, descending slopes and isobaric ascending slope at 200 mmHg are reduced in SHRLN<SHR<WKY. If we plot pulsatile time-waveform curves of pulse pressure (PP) and distension in % (Figure), maximal values and waves kinetics are altered. We therefore calculate a distensibility index as area under the curves of distension/PP. Diltiazem i.v. in SHRLN decreases systolic BP and PP to values similar to those in WKY; compliance, distensibility and stiffness reach only the values of SHR. Isobaric compliance at 160 mmHg is < than in WKY and distension remains lower than in SHR.

Conclusions: This study shows that 1) the ArtLab device analyses accurately compliance and stiffness indexes in animal models and 2) adding an analysis of aortic distension pulse waveform allows additional evaluation of BP-independent vascular wall stiffening.