Abstract
1071
Objectives: Regional wall motion analysis in conjunction with left ventricular ejection fraction (LVEF) is commonly used to assess diastolic function. Left ventricular (LV) deformation, a direct measure of diastolic function, was quantified by Hyperelastic Warping analysis of microPET images of a normotensive Wistar Kyoto (WKY) rat and a spontaneously hypertensive rat (SHR). The objective of this work was to document the differences in wall strain and fiber contraction/extension (stretch) over the life span of normotensive and hypertensive models.
Methods: Dynamic PET data were acquired using the microPET II at UC Davis. A WKY rat and a SHR rat were both imaged at 10-week intervals for a total of a year and half. At each acquisition, a dose of 1-2 mCi of F-18-FDG was injected and gated list mode data of 600-900 million counts were acquired over 60-80 mins. The end-systolic image data sets were manually segmented creating epi- and endocardial surfaces of the LV and were defined as the reference configurations. Finite element models of the LV's were created using the segmented surfaces. Hyperelastic Warping was performed on these images to obtain a fit to each model of the corresponding end-diastolic image data sets, thus providing an analysis of the diastolic relaxation and filling phases of the cardiac cycle. The Warping analyses provided the LV first principal Green-Lagrange strain and fiber stretch (extended length/reference length) distributions documented in the normotensive WKY and hypertensive SHR image data sets. The strain measurements were averaged and tabulated along with LVEF estimates.
Results: The results indicate that while the measured LVEF showed little difference between the WKY rat and the SHR rat, both the 1st principal strain and the fiber stretch showed differences in magnitude. The SHR rat showed little F-18-FDG uptake after 10 months therefore the data could not be used for analysis.
Conclusions: First Principal strain and fiber stretch provide a more sensitive measure of diastolic function than LVEF. Differences in strain distributions within the myocardial wall may provide valuable information on the early remodeling of the LV in response to the increased afterload present in hypertension. Continued uptake of F-18-FDG over the life of the SHR specimens indicates that these rats have a glucose based cellular metabolism as opposed to the fatty acid metabolism of the normotensive control.
Research Support (if any): NIH R01-EB00121, R01 HL71253 and U.S. Department of Energy Contract DE-AC02-05CH11231.
- Society of Nuclear Medicine, Inc.