My goal is to study changes in left ventricular 3D motion and deformation during hypertrophy by using tagged MRI. For my PH.D. research, I developed a method for 3D motion reconstruction from tagged MR images acquired at different view. Unlike 2D strain measurement, the components of 3D strain can be used to differentiate between changes in the magnitude and angle of contraction. An animal model of LV hypertrophy in rabbits has been developed in Dr. del Nido's laboratory, where the thoracic aorta of the rabbits is banded at 7 to 10 days of age. The stage of compensated hypertrophy, which we define as an increased mass-to-volume ratio with no dilatation, occurs at around 3 weeks while dilatation and heart failure occur at around 6 weeks of age. The presence of tumor necrosis factor (TNF) increases during the progression of hypertrophy and has been shown to affect cellular function. My proposal is to run parallel experiments using tagged MRI to study kinematic changes during the progression of hypertrophy in these rabbits. Our hypothesis is that changes in mechanics during compensated hypertrophy can be attributed to geometric factors, whereas TNF induced changes function at the cellular level is the major determinant of mechanics during heart failure. We will measure regional TNF levels and compare them with local myocardial strain measurements. The effect on regional strain after treatment with a soluble TNF receptor will also be studied.
