title: Measuring ascending aortic stiffness in vivo in mice using ultrasound.
abstract: We present a protocol for measuring in vivo aortic stiffness in mice using high-resolution ultrasound imaging. Aortic diameter is measured by ultrasound and aortic blood pressure is measured invasively with a solid-state pressure catheter. Blood pressure is raised then lowered incrementally by intravenous infusion of vasoactive drugs phenylephrine and sodium nitroprusside. Aortic diameter is measured for each pressure step to characterize the pressure-diameter relationship of the ascending aorta. Stiffness indices derived from the pressure-diameter relationship can be calculated from the data collected. Calculation of arterial compliance is described in this protocol. This technique can be used to investigate mechanisms underlying increased aortic stiffness associated with cardiovascular disease and aging. The technique produces a physiologically relevant measure of stiffness compared to ex vivo approaches because physiological influences on aortic stiffness are incorporated in the measurement. The primary limitation of this technique is the measurement error introduced from the movement of the aorta during the cardiac cycle. This motion can be compensated by adjusting the location of the probe with the aortic movement as well as making multiple measurements of the aortic pressure-diameter relationship and expanding the experimental group size.
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University.
authors.forename: Maggie M
authors.initials: MM
authors.lastname: Kuo
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University.
authors.forename: Viachaslau
authors.initials: V
authors.lastname: Barodka
authors.affiliation: Department of Medicine (Cardiology), Johns Hopkins University.
authors.forename: Theodore P
authors.initials: TP
authors.lastname: Abraham
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University.
authors.forename: Jochen
authors.initials: J
authors.lastname: Steppan
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University.
authors.forename: Artin A
authors.initials: AA
authors.lastname: Shoukas
authors.affiliation: The Australian School of Advanced Medicine, Macquarie University.
authors.forename: Mark
authors.initials: M
authors.lastname: Butlin
authors.affiliation: The Australian School of Advanced Medicine, Macquarie University.
authors.forename: Alberto
authors.initials: A
authors.lastname: Avolio
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University; Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University.
authors.forename: Dan E
authors.initials: DE
authors.lastname: Berkowitz
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University; Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University; lsantha1@jhmi.edu.
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Santhanam
mesh_terms: D000818:Animals; D001011:Aorta / Q000000981:diagnostic imaging* / Q000473:pathology*; D051379:Mice; D018608:Ultrasonography, Doppler / Q000379:methods; D059289:Vascular Stiffness / Q000502:physiology*