Evaluation of myocardial microcirculation changes in rats from different altitudes based on CT myocardial perfusion imaging

This study employed computed tomography myocardial perfusion imaging (CT-MPI) to investigate myocardial microcirculation changes in rats across different altitudes. Four-week-old male Sprague-Dawley rats were allocated into plain (450 m), moderate-altitude (MA, 2200 m), and high-altitude (HA-A, 3800 m; HA-B, 4200 m) groups. After 28 weeks, CT-MPI revealed significant altitude-dependent alterations in myocardial perfusion parameters: TTP and MTT increased while BF and BV decreased (P < 0.05). Accompanying these changes were modifications in blood parameters-including red blood cell indices, white blood cell counts, and biochemical markers-along with myocardial structural remodeling characterized by disordered cell arrangement, widened intercellular gaps, and increased collagen deposition. Molecular analyses demonstrated variations in mRNA and protein expression of hypoxia-related markers (CD34, EPO, VEGF, HIF-1α, HIF-2α) and collagen types I/III, with HIF-2α exhibiting particular sensitivity to altitude variation. These findings indicate that high-altitude exposure induces progressive myocardial microcirculation impairment coupled with hematological adaptations and tissue remodeling, potentially mediated through HIF-2α-regulated hypoxia response pathways.