Correlation between augmentation index and pulse wave velocity in rabbits

PURPOSE: Pulse wave velocity (PWV) is a direct measure of large arterial stiffness. Augmentation index (AIx) is a surrogate measure of arterial rigidity that could be affected by the ventricular ejection and peripheral haemodynamics in addition to the properties of large arteries. In clinical studies, it is still controversial whether PWV depends on AIx or not. We investigated a relationship between PWV and AIx in young normal rabbits when mean arterial pressure (MAP) level was altered using vasoactive drugs. MATERIALS AND METHODS: Pulse waves were simultaneously recorded in the ascending, proximal and distal abdominal aortas in response to intravenous infusion of angiotensin II or sodium nitroprusside in fifteen normal rabbits anaesthetized with pentobarbital sodium. Changes in intravascular diameters were measured using an intravascular ultrasound imaging system in the proximal thoracic and proximal abdominal aortas to determine pressure-strain elastic modulus (Ep). RESULTS: PWV from the ascending aorta to the bifurcation of the common iliac arteries and AIx at the ascending aorta were changed with MAP level in response to vasoactive drugs. Significant and positive correlation was observed between PWV and MAP. AIx was correlated significantly with systolic, diastolic and mean arterial pressures. PWV and AIx showed significant and positive correlation mainly with Ep in the proximal thoracic and proximal abdominal aortas, respectively. There was significant correlation between PWV and AIx (r = 0.66, P < 0.001). CONCLUSION: AIx was changed dependently on PWV when the MAP level was changed with vasoactive drugs, which was partly associated with the change in Ep.