Rapid estimation of left ventricular contractility from end-systolic relations by echocardiographic automated border detection and femoral arterial pressure

Background: Automated echocardiographic measures of left ventricular (LV) cavity area are closely correlated with changes in volume and can be coupled with LV pressure to construct pressure-area loops in real time. The objective was to rapidly estimate LV contractility from the end-systolic relations of cavity area (as a surrogate for LV volume) and femoral arterial pressure (as a surrogate for LV pressure) in patients undergoing cardiac surgery. Methods: Studies were attempted on 18 consecutive patients with recordings of LV pressure, LV area, and femoral arterial pressure on a computer workstation interfaced with the ultrasound system. End-systolic pressure-area relations (in terms of pressure-area elastance [E'(es)]) from pressure-area loops during inferior vena caval occlusions were determined before and immediately after cardiopulmonary bypass using both LV and arterial pressure by semiautomated and automated iterative linear regression methods. Results: Data sets were available for 13 patients before and 8 patients after bypass (21 studies in 14 patients). E'(es) by arterial pressure was closely correlated with E'(es) by LV pressure: r = 0.96, standard error of the estimate = 2 mmHg/cm², y = 1.01 x -0.7 by the semiautomated method and r = 0.94, standard error of the estimate = 3 mmHg/cm², y = 1.02 x -0.5 by the automated method. Analysis of semiautomated and automated estimates of E'(es) from arterial pressure and E'(es) using LV pressure by the Bland-Altman method showed no systematic measurement bias and calculated limits of agreement of 8 and 9 mmHg/cm², respectively. Similar decreases in E'(es) by arterial and LV pressure occurred from before to after bypass in 7 patients with paired data sets: 32 ± 12 to 15 ± 6 mmHg/cm² and 32 ± 15 to 15 ± 7 mmHg/cm², respectively (P < 0.05 for both). Conclusions: On-line femoral arterial pressure and LV area data by echocardiographic automated border detection may be used to rapidly calculate E'(es) as a means to estimate LV contractility in selected patients.