Fig. 6. Typical left atrial (LA) pressure–area diagrams under resting conditions (top ) and during administration of dobutamine (bottom ) in a patient with atrial fibrillation. The arrows indicate the temporal movement of the diagram. Note that no active work is performed during atrial fibrillation. The clockwise movement of each diagram indicates that forces external to the LA determine the observed changes in pressure and volume over time. Dobutamine produced a decrease in LA minimum and maximum volumes consistent with enhanced left ventricular (LV) contractility and reduced LA afterload. Reprinted with permission. 18