8.6 ELECTRICAL CAROTID BARORECEPTOR ACTIVATION LOWERS RENAL ARTERY IMPEDANCE AND STIFFNESS IN AN ACUTE CANINE MODEL

Abstract

Background: The exact mechanism by which electrical carotid baroreceptor activation (CBA) lowers blood pressure in patients with hypertension has yet to be fully elucidated. Given the central role of the kidneys in blood pressure regulation, the aim of this study was to assess the impact of CBA on renal artery impedance and hemodynamics. Materials and Methods: Renal artery pressure (P) and flow velocity (U) were measured using an intravascular pressure-velocity wire catheter (Volcano Corp.) in 6 anaesthetized dogs at baseline (BL) and during CBA intended to produce a moderate reduction in mean arterial pressure. Mean flow velocity (Umean), systolic (SBP), diastolic (DBP) and mean pressure (MAP) were derived. Local pulse wave velocity (PWV) was derived from the upstroke of the PU-loops, and wave intensity analysis and wave decomposition was applied to assess (the ratio of) the backward and forward pressure wave (Pb/Pf). Renal artery input impedance was derived. Results (Table) and discussion: CBA lowered blood pressure and reduced Pf, leading to higher Pb/Pf. CBA lowered the impedance modulus at all frequencies (DC component by 9%; harmonics on average by 28%). PWV concomitantly decreased significantly. SBP mmHg DBP mmHg MAP mmHg Umean cm/s PWV m/s Pf mmHg Pb mmHg Pb/Pf BL 107.5(11.0) 69.8(15.8) 85.6(14.3) 29.5(5.4) 8.2(2.9) 34.7(6.0) 12.6(2.8) 0.37(0.08) CBA 89.1(18.9)* 55.4(21.8)* 68.6(21.8)* 27.4(7.7) 5.4(1.7)* 29.3(3.6)* 12.7(2.5) 0.43(0.06)* mean(standard deviation); *P<0.05; paired T-test Conclusions: In an acute canine model, CBA has a profound effect of decreasing renal artery impedance and stiffness, suggesting that the therapy modulates renal artery tone and may have renoprotective effects by reducing the pulsatile energy in the microcirculation.