Relationship of aortic excess pressure obtained using pressure-only reservoir pressure analysis to directly measured aortic flow in humans.

OBJECTIVES: A reservoir pressure model describing left ventricular-large artery interaction has been proposed as a useful heuristic model providing insight into the propagation of the central blood pressure as well as providing clinical prognostic information. A pressure-only approach to calculation of reservoir pressure waves has been proposed but this assumes that the resultant excess pressure is proportional to the volume flow rate out of the left ventricle; this has not been tested in humans. APPROACH: We use non-invasively acquired central pressure and flow data obtained in the 2nd Australian National Blood Pressure Study to test this assumption and to investigate the use of flow approximations based on excess pressure or an assumed triangular flow pattern in calculation of forward and backwards waves in the aortic root. MAIN
RESULTS: Results from 821 subjects showed close association between the shape of measured flow patterns and calculated excess pressure, with mean coefficient of determination R 2  =  0.931  ±  0.046(SD). For directly measured versus triangular flow approximation R 2 was 0.918  ±  0.057. Comparison of the peak amplitudes of forwards (Pf) and backwards (Pb) going pressure waves resulted in significant correlation between Pfmax and Pbmax using both measured flow and the triangular flow approximation (0.83 and 0.79 respectively) and using excess pressure as a flow approximation (Pfmax 0.86 and Pbmax 0.77). All associations for peak pressures and integrals were high with R-values between 0.70 and 0.95. SIGNIFICANCE: Pressure-only reservoir wave analysis appears to conform to the inherent assumptions underpinning the mathematical approach employed: this provides support for use of reservoir analysis as a non-invasive method to describe potentially important features and functions of ventriculo-vascular interaction without the requirement for flow measurement.