High thoracic sympathetic block improves coronary microcirculation disturbance in rats with chronic heart failure

Introduction: Coronary microcirculation disturbance plays an important role in chronic heart failure (CHF). High thoracic sympathetic block (HTSB) is effective to treat CHF, but its impact on coronary microcirculation is unclear. Methods: Forty male Wistar rats were subcutaneously injected with isoproterenol (340 mg/kg) for 2 days. Eight weeks later, 24 surviving rats were randomized to the CHF and HTSB groups and 10 rats were used as the control group. 50 μl of saline and ropivacaine (0.2%) were epidurally infused everyday in the CHF and HTSB group respectively. Four weeks later, echocardiography and pathological and ultrastructural examination, capillary histochemical staining and vascular endothelial growth factor (VEGF) immunohistochemical staining in left ventricular (LV) subendocardial myocardium were performed. Results: Compared with the control group, LV dilation and dysfunction, myocardial focal necrosis, capillary spasm appeared in the CHF group. HTSB ameliorated LV dilation and dysfunction, myocardial necrosis and capillary spasm. Rats in the CHF group had less myocardial capillary density and more VEGF expression than in the control group (1591 ± 99 vs. 1972 ± 118/mm2, 0.62 ± 0.13 vs. 0.33 ± 0.10 optic density, all p < 0.05). Myocardial capillary density (1782 ± 96/mm2) was more and VEGF expression (0.47 ± 0.12 optic density) was less in the HTSB group than in the CHF group (all p < 0.05). Conclusion: HTSB improves coronary microcirculation disturbance in CHF, which may contribute to reversing myocardial remodeling and dysfunction. HTSB stimulates myocardial capillary growth independent of VEGF.