Measuring Ascending Aortic Stiffness <em>In Vivo</em> 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.

A preclinical ultrasound method for the assessment of vascular disease progression in murine models

“…Previous research on humans and animals indicated that arterial elasticity is linked to the structural arrangements of the artery 38 relating to cardiovascular disease and aging. 38,39 Preclinical studies showed that arterial elasticity decreases during fatty streak formation, before pathophysiological changes. 38 Leone et al concluded that carotid artery distension is an independent predictive marker of coronary heart disease in the elderly and found that carotid artery distension was associated with carotid plaque burden.…”

Killing Me Unsoftly

“…As such, the aforementioned in vivo metrics of arterial stiffness, such as PWV (either determined though Doppler measurements, 43, 44 applanation tonometry, 45 or MRI 46 ) or local arterial compliance and distensibility 25, 47, 48 have been established for use in murine studies. Those methods are indispensable for longitudinal in vivo studies measuring arterial stiffness but only allow indirect assessment of biomechanical properties.…”

Assessment of Phasic Changes of Vascular Size by Automated Edge Tracking-State of the Art and Clinical Perspectives

“…However, the PWV is usually measured from the carotid-femoral artery PWV, a global index, which does not reflect local stiffness variations. In theory, aortic stiffness could be estimated directly, by measuring with US the aorta pulsatility under a known pressure variation (systo-diastolic) (55), in different aortic segments (56). Whether segmental aortic stiffness measured by US might discriminate different patients' conditions and risk, it is worth exploring.…”