Comparative Value of Single-beat Load-independent Contractility Indices in Dilated Cardiomyopathy and Mitral Regurgitation

Objective: We sought to compare single-beat estimates of contractility indices. Methods: Echocardiography was performed for 6 control patients, 8 patients with dilated cardiomyopathy, and 9 patients with mitral regurgitation (MR). Left ventricular volume waveform, outflow tract velocities, and mitral annulus velocities were recorded with carotid tonometry. Numeric simulations were used to generate the same data while varying contractility, compliance, and MR. Estimates of elastance (normalized systolic and bilinearly approximated), preload-recruitable stroke work, and preload-adjusted maximal power were calculated. Results: Normalized systolic and bilinearly approximated elastance were decreased in patients with dilated cardiomyopathy (P < .005 for both) and MR (P = .0002 and .02, respectively). Preload-recruitable stroke work and preload-adjusted maximal power were decreased in patients with dilated cardiomyopathy only (P < .005 for both). Simulations confirmed that these differences are a result of dissimilar behavior of estimates if MR or compliance change. Conclusions: Single-beat indices are decreased in dilated cardiomyopathy, but in MR show dissimilar behavior.