Effect of isoflurane and halothane on regional cardiac stiffness

To investigate the possibility of regional differences in cardiac stiffness which may relate to the known regional differences in systolic left ventricular function, seven mongrel dogs were acutely instrumented and regional cardiac stiffness was measured at both apical and basal region under two different concentrations of isoflurane (1.08% and 1.9%) as well as equipotent concentrations of halothane (0.9% and 1.58%). Cardiac stiffness was determined in terms of distensibility, chamber stiffness (derived from pressure-length relationships), and an elastic stiffness constant (derived from stress-strain relationships). Regional differences in cardiac stiffness were observed for all three indices and for each anaesthetic setting except for the elastic stiffness constant under 1.9% of isoflurane. The data indicate that regional differences in cardiac stiffness exist between the apex and the base of the heart. These regional differences do not depend on the anaesthetic agent or its concentration and may contribute to the differences in systolic function.