Indices of ventricular contractile state: comparative sensitivity and specificity.

Twenty-four indices of ventricular contractile state were compared as to inotropic sensitivity using dobutamine infusion, as well as to preload and afterload independence using dextran and phenylephrine infusion. Experiments were done in 10 open-chest instrumented dogs and signal processing was done off-line by digital techniques. The indices studied, listed in order of decreasing sensitivity, are (1) power-averaged rate of generation of power density, (2) peak isovolumic rate of change of power, (3) ejection rate of change of power at peak tension, (4) peak second time derivative of ventricular pressure, (5) peak ejection rate of change of power, (6) peak isovolumic power, (7) energy-averaged power density, (8) mean aortic blood acceleration, (9) peak aortic blood acceleration, (10) peak first time derivative of ventricular pressure, (11) peak normalized fiber velocity, (12) peak fiber velocity, (13) peak aortic blood flow, (14) peak power, (15) extrapolated Vmax (total pressure), (16) mean normalized fiber velocity, (17) mean fiber velocity, (18) extrapolated Vmax (developed pressure), (19) mean aortic blood flow, (20) mean power, (21) stroke volume, (22) peak wall tension, (23) mean wall tension, (24) time-tension index. The most sensitive index which was statistically independent of preload and afterload manipulation was the ejection rate of change of power at peak tension.