Computational modeling of oxygen consumption in the heart based on PET measurements

by Yan, Fu.

Many cardiovascular diseases are partly due to heart muscle malfunctions. The main dynamic function in the heart is metabolism via mitochondrial respiration. And the most direct measure of oxidative tissue metabolism is the conversion rate of oxygen to water. Finding the oxygen consumption rate in the heart vessel will help us prevent the heart diseases. In the experiment, [15O]-labeled RBCs (Red Blood Cells) and indocyanine green dye were injected into the isolated blood-perfused rabbit heart. The dye curves defined the inflow for the dye have the same shape as the inflow curves for the [15O] oxygen. The inflow and outflow dilution curves for [15O] were obtained with use of PET (Positron Emission Tomography) technology. After appropriate correction for baseline and radioactive decay, the data were transferred to a UNIX workstation for model analysis. A linear, three-region (capillary space, interstitial fluid space, and parenchymal cell space), and axially distributed model is introduced to simulate the oxygen consumption process and determine the oxygen conversion rate. Parameters of concentration are oxygen and water corresponding to capillary space, interstitial fluid space, and parenchymal cell space. The diffusion coefficients are largely independent of molecular motion. The blood flow happens only in capillary part. Other parameters are determined by experimental data. Using the input data, consumption rate i is determined through a process minimizing the difference between the experimental and numerical output. Effects of key parameters on oxygen concentration and consumption rate are investigated. ii