The aim of this study was to establish whether analysis of the left ventricular pressure waveform provides indicative information about cardiac load and contractility and to develop an algorithm for computer-based assessment of changes in these variables. In eight healthy standard breed anaesthetized open-chest pigs, a high frequency response guide-wire mounted pressure sensor was introduced into the left ventricle. Preload reduction was induced by vena cava occlusion, afterload increase by an i.v. injection of phenylephrine and increased contractility by an i.v. injection of adrenalin. Left ventricular pressure waveform analysis was performed by plotting the slope of the pressure curve during the systolic ejection period versus maximal systolic pressure. The analysis revealed characteristic changes in left ventricular pressure and pressure waveform and identified easily discernible reaction patterns in the slope versus maximal pressure plot, specific for each provocation. Analysis of the left ventricular waveform provides indicative information about loading conditions and contractility. The proposed algorithm can easily be implemented in pressure monitoring systems allowing real-time assessment and discrimination of acute changes in preload, afterload and myocardial performance.