Assessment of right ventricular (RV) function is inherently more difficult than left ventricular (LV) function because of the unusual geometry. We have developed a bedside system that integrates a multiwire gamma camera (MWGC) with pulmonary artery catheterization (PAC). This system permits simultaneous acquisition of first pass radionuclide angiography (RNA) images and pressure data from the catheter as well as acquisition of thermodilution data. The system provides highly accurate quantitative measurement of RV and LV ejection fractions, which are indicators of systolic function. This combined RNA-PAC technique permits simple and accurate calculation of both right and left ventricular volume of the ventricular cavity by dividing stroke volume by ejection fraction. Because these data are based on measurements that are non-geometric, this technique for volume measurement is extremely accurate and far surpasses any of the currently available modalities. The system is capable of generating curves relating RV volumes and pressures, which are critical in evaluation of heart failure (HF) patients. Clinical studies were successfully performed on 25 patients, and the results were of high quality and were reproducible. In summary, the system for the first time provides a novel method of generation of RV pressure-volume loops, using a hybrid method of right heart catheterization and RNA.