When arterial blood flow in perfused hearts is lowered below critical levels, oxygen delivery to cardiac tissue is impaired and heterogeneous anoxic zones develop. These zones can be visualized as areas of impaired metabolism by imaging epicardial NADH fluorescence. This study involves a comparison of metabolic and flow heterogeneities in perfused rat hearts. Low-flow ischemia was induced in perfused rat hearts by stepwise decreases in perfusion pressure. NADH images of the perfused hearts were acquired during flow titrations using a computer-controlled videofluorometer. Fluorescent microspheres of different colors were injected at normal and reduced perfusion pressures and NADH images of heterogeneous (patchy) surface perfusion recorded. Fluorescent microsphere locations were obtained using an automated microsphere imaging system. This instrument permits evaluation of regional flow in variable tissue volumes. Correlations are made between perfusion pressure, micro regional flow volumes and metabolic ischemic areas.
Research supported by grant HL50898-02 from the National Institutes of Health and a Partners in Science award from Research Corporation and the M.J. Murdock Charitable Trust.