Circulation research
-
Circulation research · Aug 1986
Myocardial oxygen tension determines the degree and pressure range of coronary autoregulation.
Experiments were designed to separate effects of myocardial oxygen tension and oxygen consumption on coronary autoregulation. The approach was to measure coronary hemodynamic and metabolic responses to decreases in perfusion pressure during interventions that altered the balance between myocardial oxygen supply and demand. Studies were conducted in anesthetized heart-blocked dogs with the left coronary artery perfused from a pressure-controlled blood reservoir. ⋯ The observed variations in the autoregulation index were largely explained by differences in the prevailing venous oxygen tension. Furthermore, the upper pressure limit for autoregulation was dependent on venous oxygen tension with a threshold oxygen tension for autoregulation of 32 mm Hg. These results indicate that coronary autoregulation is closely coupled to the prevailing venous oxygen tension but not oxygen consumption and is facilitated at low venous oxygen tension.