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We describe a computer algorithm that allows continuous, real-timeevaluation of ventricular elastance (Ees), arterial elastance (Ea), and theircoupling ratio in a clinical setting. In the conventional pressure-volumeanalysis of left ventricular (LV) contractility, invasive methods of volumedetermination and a significant, rapid preload reduction are required togenerate Ees. With the help of automated border detection by transesophagealechocardiography, and a technique of estimating peak LVisovolumic pressure, Ea and Ees were determined from a single cardiac beatwithout the need for preload reduction. A comparison of results obtained bya conventional approach and the new algorithm technique, showed goodcorrelation for Ea (r = 0.86, p < 0.001) and Ees(r = 0.74, p = 0.001). Bias analysis showed a bias (d) of1.47 mmHg/cm2 for Ea with a standard deviation (SD) of 7.03mmHg/cm 2, and upper (d+2SD) and lower (d−2SD)limits of agreement of 15.25 mmHg/cm2 and −12.31mmHg/cm2, respectively. Bias analysis showed a bias of−1.42 mmHg/cm2 for Ees with a SD of 4.88mmHg/cm2, and limits of agreement of 8.15mmHg/cm2 and −10.98 mmHg/cm2. Thealgorithm’s stability to artifacts was also analyzed by comparingmagnitudes of residuals of Ea and Ees from source signals with and withoutnoise. With Ea differing by an average of 1.036 mmHg/cm2 andEes differing by an average of 0.836 mmHg/cm2, the algorithmwas found to be stable to artifacts in the source signals. |
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