Afterload Sensitivity of Nonlinear End-Systolic Pressure–Volume Relation vs Preload Recruitable Stroke Work in Conscious Dogs

The observationsin vivoof a non-linear, afterloadsensitive end-systolic pressure–volume relation (ESPVR) and a linear, load-insensitive preload recruitable stroke work (PRSW) relation may be reconciled by considering the PRSW as a product of both the ventricular ESPVR and the arterial elastance (Ea). We obtained pressure–volume data from eight conscious dogs. The ESPVR was nonlinear, and its trajectory was afterload-dependent. The PRSW was linear and load-independent. Arterial elastance changed with both acute reductions in preload and steady-state changes in afterload. The PRSW relation thus describes both myocardial function and ventricular–arterial interaction and is a useful index of cardiovascular performance in patients.