Pressure-volume (PV) loops can be used to derive the valuable cardiac functional parameters contractility and compliance. Conventional PV loop catheters provide unreliable volume measurements. In this study we develop and validate a method to obtain dynamic PV loops during an MRI-guided preload alteration via inferior vena cava occlusion, using simultaneous measurements of left ventricular pressure from a catheter and volume from real-time long-axis cardiac MRI. Pressure and volume signals were synchronized and used to derive contractility and compliance. Long-axis derived volumes were validated against conventional short-axis images. The method was tested in naïve, ischemic cardiomyopathy, and aortic banding swine models.