Simultaneous measurements of pulmonary capillary wedge and left atrial pressures as well as other hemodynamic effects of lidocaine with verapamil infusion were investigated in six dogs given fentanyl-nitrous oxide anesthesia. They were an initial bolus of lidocaine 3 mcg/kg/min. After 30 minutes of lidocaine infusion, Verapamil 0.2 mg/kg was given initially, followed by infusions of 3, 6, 9 and 12 mcg/kg/min respectively. Each infusion of verapamil lasted 30 minutes. Hemodynamic measurements were taken every 30 minutes following each infusion. We found that the pulmonary capillary wedge pressures were significantly higher than the left atrial pressures in each of the cases in which verapamil 6.9 and 12 mcg/kg/min(p<0.05) were respectively injected. The discrepancy between pulmonary capillary wedge and left atrial pressures may be due to an increase in pulmonary vascular resistance index. This may be related to an increase in mean pulmonary arterial pressures and a decrease in left ventricular stroke work index. We concluded from this data that the left atrial pressure reflects more accurately left ventricular filling. Therefore, The left atrial pressure should be used instead of pulmonary capillary wedge pressure to monitor the hemodynamics of depressed ventricular performance.