Doppler evaluation of peripheral vascular adaptations to transverse aortic banding in mice

Transverse aortic banding in mice is commonly used to produce pressure overload, but the resulting cardiac hypertrophy is variable and the actual load produced is unknown. The purposes of the study were to characterize peripheral blood flow in banded mice using noninvasive Doppler methods, investigate whether changes in flow could predict the amount of cardiac hypertrophy induced and validate the simplified Bernoulli equation for estimating the pressure drop across the stenosis in very small vessels. Wild-type mice underwent aortic banding (n=15) or sham operation (n=6). Doppler velocity was measured in the right and left carotid arteries (RCA and LCA) 1 day later, and the heart weight/body weight ratio was measured at 7 days. The RCA/LCA peak velocity ratio at 1 day was significantly correlated with the heart weight/body weight ratio at 7 days after banding (r=0.62, p<0.005). In another 12 banded mice, serial Doppler velocity signals were obtained from the aortic banding site, the abdominal aorta (ABD) and the RCA and LCA before, 1 day after and 7 days after banding. Peak RCA velocity increased significantly after banding and both peak LCA velocity and peak ABD velocity decreased significantly. Mean velocities of RCA, LCA and ABD were unchanged before and after banding, suggesting that mice utilize peripheral arterial adaptations to maintain normal cerebral and peripheral perfusion. There was a significant positive correlation (r=0.83, p<0.001) between the RCA/LCA peak velocity ratio and peak jet velocity across the aortic banding site. Our data indicate that changes in carotid velocity after aortic banding can be used to estimate the pressure drop across the aortic band and to predict loading and resulting cardiac hypertrophy in mice. Additionally, we validated that the simplified Bernoulli equation (DeltaP=4V2) can be used to estimate the pressure drop across the aortic band in mice noninvasively.