Dimension change measures of regional ventricular function, such as absolute or percent wall thickening (ΔT or %ΔT) or segmental shortening (ΔL or %ΔL), are highly load dependent. In 16 anesthetized mongrel dogs we assessed use of the end-systolic pressure-thickness and end-systolic pressure-length relationships (ESPTR,ESPLR) as more load-independent measures of regional function. We found that the ESPTR and ESPLR could be measured without detectable baroreceptor-mediated reflex changes in cardiac contractile state. Systemic administration of dobutamine shifted the ESPTR to the right and the ESPLR to the left of control, mainly due to a change in the slope (Ees) of the relationships. Both ΔT, %ΔT and ΔL, %ΔL failed to detect the positive inotropic effect of dobutamine because of an associated reduction in preload. With systemic administration of propranolol, ESPTR, ESPLR, ΔT, %ΔT, and ΔL, %ΔL detected the negative inotropic effect. Thus systemic propranolol shifted the ESPTR to the left and the ESPLR to the right of control, mainly due to a change in Ees. Regional administration of dobutamine shifted the ESPTR and the ESPLR in the direction of positive contractility in the region receiving the drug, whereas simple dimension change measures of regional function failed to detect the inotropic effect because preload fell and the timing of regional end-systole was altered. With regional propranolol both the ESPTR,ESPLR and simple dimension change measures detected the negative inotropic effect. Thus the ESPTR,ESPLR is a reliable measure of regional ventricular function and may be better than simple dimension change measures of regional function, particularly when loading conditions or the timing or regional systole is altered by an intervention.
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)