Robert J. Gropler, M.D.

DEPARTMENT OF Radiology
Keywords: cardiac disease, cardiovascular imaging, metabolism, MRI, perfusion, PET

It is well established that cardiac function declines with age and the cardiac manifestations of a variety of diseases such as hypertension and diabetes mellitus become more pronounced with age. Furthermore, studies of experimental models of aging have shown there is a decline in myocardial vasodilatory capacity and a shift in myocardial intermediary metabolism from primarily fatty acid substrate use to that of glucose. Similar observations have been obtained in experimental models of pressure-overload myocardial hypertrophy. Conversely, in the diabetic heart there is a shift toward greater fatty acid use. The goal of this laboratory is to determine whether similar observations occur in humans and, more specifically, whether changes in myocardial perfusion and metabolic function that occur with age predispose the heart to more significant perturbations in myocardial perfusion and metabolism when hypertension and diabetes are present. To achieve this goal, measurements of myocardial perfusion and metabolism were performed with positron emission tomography (PET) and measurements of myocardial mechanical function were performed with magnetic resonance imaging (MRI) and echocardiography in appropriate patient subsets during a variety of interventions designed to alter plasma substrate levels, the hormonal environment and myocardial work. Using these approaches, we have demonstrated that the alterations in perfusion and metabolism that are observed in experimental models of aging occur in older healthy individuals and become more pronounced in patients with hypertension-induced myocardial hypertrophy and type 1 diabetes mellitus. Moreover, these abnormalities in myocardial perfusion and metabolism are paralleled by abnormalities in myocardial mechanical function. Studies are ongoing to help elucidate the mechanisms responsible for the blunting of myocardial vasodilatory capacity and shifts in metabolism, to identify potential interventions designed to “normalize” myocardial perfusional and metabolic patterns, and to determine whether the “normalization” of these patterns has salutary effects on myocardial mechanical function. Trainees will acquire an extensive understanding of the relationship between myocardial perfusion, intermediary metabolism, and mechanical function in humans, particularly with respect to the impact of aging, diabetes mellitus, and hypertension-induced myocardial hypertrophy. In addition, trainees will gain insight into instrument design, radiopharmaceutical and contrast agent production, kinetic modeling, and image analysis and alignment as they relate to PET, MRI, and echocardiography.