Influence of polymeric microspheres on the myocardial oxygen partial pressure in the beating heart of pigs

Abstract

Injection of labeled microspheres is an established method in animal models to analyze the capillary organ blood flow at different time points. However, the microspheres can lead to stenoses of the capillary lumen, which might affect tissue oxygen supply. Our study aimed to investigate the influence of repeated injections of microspheres into the left coronary artery on the tissue oxygen partial pressure (pO2) in the downstream supplied myocardium of Göttingen minipigs. Tests (n = 6 pigs each) were performed with two differently sized microspheres (ø = 10 ± 0.1 μm (M10) or ø = 15 ± 0.15 μm (M15)) from polystyrene. The pO2 was measured in the midmyocardium of the left and right ventricle for 6 min continuously after each of five injections (1 × 106 microspheres each). There was a time laps of 12 min between each injection. In addition, the influence of the carrier solution was analyzed solely in the identical time frame. pO2 decreased significantly in the myocardial area supplied by the ramus interventricularis paraconalis after injection of M15 microspheres. In contrast, the application of the M10 microspheres did not change the myocardial pO2. This finding suggests to use microspheres with diameters not exceeding 10 μm for the coronary blood flow assessment.