Abstract 16807: New Approach to Pressure-Volume Loop Analysis Using Custom Made High Fidelity MRI Compatible Pressure Sensor Tipped Catheters and Real Time MRI

Abstract

Background: Pressure-Volume (PV) loop analysis remains the only load-independent method to assess cardiac function. However, current methods limit the clinical use of PV loops particularly in congenital defects. We developed a novel technique for PV loop analysis using custom made high fidelity MRI compatible pressure sensor tipped catheters (hfMRIc) with real time MRI (rtMRI). Hypothesis: Accurate PV loop cardiac function can be obtained using single plane rtMRI imaging and hfMRIc pressure sensor tipped catheters. Methods: PV loop analysis was performed in the LV of 4 swine. Instantaneous ventricular volume estimation was obtained with the Simpson method using V = ∑Vi(Li) where Vi(Li) are length volume relations derived from a short axis cine stack and a LA cine plane and Li are lengths obtained using custom made segmentation software and a single rtMRI LA plane (Figure 1(a)). Volume error calculations were performed at two different preload conditions. Pressure measurements were obtained with custom made hfMRIc fiber optic pressure sensor tipped catheters. Pressure measurements were compared to values obtained with a high fidelity Millar catheter positioned in the Aorta. Results: At a sampling rate of 20 Khz, the pressure difference between the hfMRIc catheters and the Millar catheter was 1% with a standard deviation (SD) of 0.9%. There was no effect of MRI scanning on pressure recording. The difference between the volume measured with a short axis cine stack and the volume estimated with our methodology using a single LA cine plane was 6.7% with a SD of 4.7%. EDPVR and ESPVR and instantaneous PV loops were obtained by inflating a balloon in the IVC while obtaining rtMRI planes at a temporal resolution of 42 msec (Figure 1(b)). Conclusions: Using this new technique, we can accurately assess the instantaneous cardiac function using PV loops. Unlike current technology this new modality is not dependent on ventricular shape or valve function.