EXCESSIVE PULSATILE POWER IN CAROTID ARTERIES IS ASSOCIATED REDUCED COGNITIVE FUNCTION: PULSATILE AND STEADY STATE ARTERIAL HEMODYNAMICS IN TWO COMMUNITY-BASED COHORTS

Abstract

Objective: Increased pressure and/or flow pulsatility in the carotid arteries have been adversely associated with cerebral structure and function. We postulated that increased power(product of pressure and flow) pulsatility is even harmful to the microcirculation of high-flow organs. We aimed to investigate the associations of carotid pressure, flow, and power pulsatility with cognitive function and pulsatile and steady state hemodynamics in proximal aorta and carotid arteries. Design and method: A total 1855 adult aged > = 30 years old were recruited for measurements of echocardiography and carotid sonography. We obtained hemodynamic parameters including pressure, flows, and power at proximal aorta and both carotid arteries. Proximal aortic pressure was determined by the tonometry waveform measured at common carotid arteries, calibrated by mean and diastolic pressure of brachial pressure. Pulsatility indexes(PIs) of pressure, flow and power in the proximal aorta and carotid arteries were calculated as the pulsatile value divided by mean value. We modelled the aorta-carotid interface with a large parent vessel(proximal aorta) branching into small (carotid) and large(distal aorta) daughter vessels and calculated the reflection coefficient and transmitting coefficient from aortic and carotid characteristic impedances. Cognitive function was evaluated by the Montreal Cognitive Assessment (MoCA) score. Results: The pulsatile component was 10.3%(105/996mW) and 4.2%(11/268mW) of total aortic and carotid power, respectively. PIs of aortic pressure(r = -0.048,p = 0.0417), aortic flow(r = 0.060,p = 0.0101), aortic power(r = -0.080,p = 0.006), carotid flow(r = -0.085,p = 0.003), and carotid power(r = -0.097,p < 0.0001) were all significantly associated with cognitive function, independent of age, sex, and education. Carotid power PI was significantly better than other PIs in the association with cognitive function. In the multivariable model, MoCA score was positively and negatively associated with carotid mean power (beta = 0.005,p < .0001) and carotid pulsatile power(beta = -0.048,p < .0001), respectively. With increasing aortic characteristic impedance and transmitting coefficient, and decreasing reflection coefficient, there was a significantly increased transmitting aortic power into carotid arteries(all p value < 0.0001). Conclusions: Among all ascending aorta and carotid hemodynamics, carotid power PI was the hemodynamic parameter with the best correlation with cognitive function. Increased proximal aortic stiffness, and increased transmission and decreased reflection of the aortic power at the aorta-carotid interface were closely associated with increased carotid pulsatile power.