Figure 7-7 Linear relationship between the time constant of isovolumic relaxation (τ) and left ventricular end-systolic pressure (P_es ) during inferior vena caval occlusion (left panels) in a typical dog before (red squares) and after (black squares) the development of pacing-induced cardiomyopathy in the conscious state and during isoflurane and halothane anesthesia. The histograms illustrate the slope (R) of the τ versus P_es relationship in the conscious state (top right panel) and during isoflurane (middle right panel) and halothane (bottom right panel) anesthesia before (red bars) and after (black bars) pacing. a, Significantly (P < .05) different from normal myocardium. (Adapted from Pagel PS, Hettrick DA, Kersten JR, et al: Isoflurane and halothane do not alter the enhanced afterload sensitivity of left ventricular relaxation in dogs with pacing-induced cardiomyopathy. Anesthesiology 87:952–962, 1997.)