The impact of acute volume overload hemodynamics on the DFT with concurrent moderate left ventricular systolic dysfunction is unknown. Ten mongrel dogs (17.2 kg), using a crossover study design, each had baseline (study 1) hemodynamic, echocardiographic, and DFT measurements. These measurements were repeated after left ventricular dysfunction was induced using a norepinephrine (5 micrograms/kg per min) infusion (study 2). Hemodynamic and DFT parameters were obtained simulating acute heart failure by volume overload with an 0.9% normal saline infusion to an associated mean pulmonary capillary wedge pressure of > 19 mmHg (study 3). Numerous significant echocardiographic and hemodynamic parameters were noted when the animals from studies 1 and 2, 2 and 3, and 1 and 3 were compared. A significant difference in the DFT was observed only when study animals 1 and 3 were compared (P < 0.02). None of the dogs were hypoxemic at the time of the acute heart failure DFT. The mechanism of this finding remains unknown. This data would suggest that acute volume overload with associated left ventricular dysfunction does adversely affect the DFT in a canine model.