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A Novel Methodology for Rat Aortic Pulse Wave Velocity Assessment by Doppler Ultrasound: Validation against Invasive Measurements.

There is still lack of a simple, accurate and noninvasive method for rat aortic pulse wave velocity (PWV) measurement, especially the transit distance cannot be accurately measured. Thus we aimed to derive an equation for aortic transit distance as a function of the nose-to-rump length (L), and to test the hypothesis that aortic PWV measured by new equation combined with Doppler ultrasound (the "equation method") may have stronger correlation with invasive measurements than traditional "body surface method". Two hundred male Sprague-Dawley (SD) rats (age ranged 5-24 weeks) were included in Protocol 1 and the aortic transit distances were measured post mortem. In Protocol 2, heart-femoral PWV and carotid-femoral PWV were measured by "equation method" (hfPWVE, cfPWVE), and also by traditional "body surface method" (hfPWVS, cfPWVS) in another 30 young and 28 old rats. Then these measurements were validated against invasively measured hfPWVI, cfPWVI from the same animal. Protocol 1 showed that the heart-femoral transit distance could be calculated by 0.6086×L-1.6523, the carotid-femoral transit distance by 0.4614×L+1.8335. In Protocol 2, in young rats, the Pearson r between hfPWVE, cfPWVE, hfPWVS, cfPWVS and their corresponding invasive measurement were 0.8962, 0.8509, 0.8387, 0.7828, respectively (all P<0.0001). In old group, the results were 0.8718, 0.7999, 0.8330, 0.7112, respectively (all P<0.0001). The hfPWVE and cfPWVE showed better agreement with hfPWVI and cfPWVI, and lower intra- and inter-observer variability compared with hfPWVS and cfPWVS in both groups. These findings demonstrate that this novel methodology provides a simple and reliable method for rat noninvasive aortic PWV measurement.