Characterization of segmental aortic stiffness and pulse pressure amplification in Wistar-Kyoto rats

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    Abstract

    Objective: Arterial pulse pressure amplification (PPA) between proximal and distal sites is a result of progressive increase in arterial stiffness (AS) along the vascular tree and wave propagation phenomena, both dependent on mean arterial pressure (MAP). The aim of this study was to characterize aortic pulse wave velocity (PWV), a surrogate measure of AS, and PPA between the proximal and distal aorta in normotensive rats over a wide range of MAP. Methods: Experiments were performed in anaesthetized (Urethane, 1.3 g/kg, ip) Wistar Kyoto rats (n = 6). Beat-to-beat PWV and pulse pressure (PP) were measured in the proximal (pPWV, pPP) and distal (dPWV, dPP) aortic segments using simultaneous recordings of pressure with high fidelity catheter-tip sensors over segment lengths of 4–5 cm. MAP was increased and decreased by 30 s infusions of phenylephrine (50 μg/min) and sodium nitroprusside (10 μg/min) respectively. PPA (rdPP/pPP), pPWV, dPWV and whole aorta PWV were expressed as functions of MAP in the range 50 – 140 mmHg. Elastic non-uniformity (ENU) was calculated as ENU = dPWV-pPWV. Results: PWV-MAP plots for all aortic segments showed a progressive increase in PWV with MAP. dPWV showed a higher sensitivity to MAP (0.042 m/s/mmHg) compared to pPWV (0.0092 m/s/mmHg). PPA-MAP curves showed a curvilinear pattern, with peak PPA (1.21 ± 0.04 [SEM])) occurring around normal resting MAP (rMAP,106 ± 1.4[SEM] mmHg). This was associated with a general monotonic increase in dPP with MAP but a curvilinear pattern in pPP, with a minimal pPP around rMAP. For MAP < rMAP, PPA showed strong correlation with ENU (r2 = 0.91) with no significant correlation for MAP > rMAP. Conclusions: For pressures below resting MAP, PPA in rats corresponds almost entirely to elastic non-uniformity of the aorta. For higher pressure, PPA decreases, possibly due to increased effects of peripheral wave reflection. This may have implications in elucidation of mechanisms involved in aortic pulse pressure changes with antihypertensive interventions.
    Original languageEnglish
    Article numberPP.10.385
    Pages (from-to)e165
    Number of pages1
    JournalJournal of Hypertension
    Volume28
    Issue numbere-Supplement A
    DOIs
    Publication statusPublished - 2010
    Event20th Annual Meeting of the European Society of Hypertension - Oslo, Norway
    Duration: 18 Jun 201021 Jun 2010

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