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

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 (Ea_ao_SYS, Ea_fem_SYS, Ea_rad_SYS), mean arterial pressure (Ea_ao_MAP, Ea_fem_MAP, Ea_rad_MAP), and dicrotic notch pressure (Ea_ao_DIC, Ea_fem_DIC, Ea_rad_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 Ea_ao_SYS, Ea_fem_SYS and Ea_rad_SYS, respectively. For estimates using dicrotic notch, the relationship was r² = 0.94, 0.95 and 0.94 for Ea_ao_DIC, Ea_fem_DIC and Ea_rad_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 Ea_ao_MAP, Ea_fem_MAP and Ea_rad_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.