Reliability of effective arterial elastance using peripheral arterial pressure as surrogate for left ventricular end-systolic pressure.

ABSTRACT

To compare the effective arterial elastance (Ea) obtained from the arterial pressure with Ea calculated from left-ventricular (LV) pressure-volume analysis. Experimental study. LV pressure-volume data was obtained with a conductance catheter and arterial pressures were measured via a fluid-filled catheter placed in the proximal aorta, femoral and radial arteries. Ea was calculated as LV end-systolic pressure (ESP)/stroke volume (SV). Experimental protocol consisted sequentially changing afterload (phenylephrine/nitroprusside), preload (bleeding/fluid), and contractility (esmolol/dobutamine). 90% of systolic pressure (Eaao_SYS, Eafem_SYS, Earad_SYS), mean arterial pressure (Eaao_MAP, Eafem_MAP, Earad_MAP), and dicrotic notch pressure (Eaao_DIC, Eafem_DIC, Earad_DIC) were used as surrogates for LV ESP. SV was calculated from the LV pressure-volume data. When Ea was compared with estimations based on 90% SAP, the relationship was r2 = 0.95, 0.94 and 0.92; and the bias and limits of agreement (LOA) - 0.01 ± 0.12, - 0.09 ± 0.12, - 0.05 ± 0.15 mmHg ml-1, for Eaao_SYS, Eafem_SYS and Earad_SYS, respectively. For estimates using dicrotic notch, the relationship was r2 = 0.94, 0.95 and 0.94 for Eaao_DIC, Eafem_DIC and Earad_DIC, respectively; with a bias and LOA 0.05 ± 0.11, 0.06 ± 0.12, 0.10 ± 0.12 mmHg ml-1, respectively. When Ea was compared with estimates using MAP, the relationship was r2 = 0.95, 0.96 and 0.95 for Eaao_MAP, Eafem_MAP and Earad_MAP, respectively; with a bias and LOA 0.05 ± 0.11, 0.06 ± 0.11, 0.06 ± 0.11 mmHg ml-1, respectively. LV ESP can be estimated from the arterial pressure. Provided that the SV measurement is reliable, the ratio MAP/SV provides a robust Ea surrogate over a wide range of hemodynamic conditions and is interchangeably in any peripheral artery, so it should be recommended as an arterial estimate of Ea in further research.