Autoregulation of Coronary Blood Flow: Effect of Interarterial Pressure Gradients

• Autoregulation is the term applied to the mechanism (s) which maintain blood flow through an organ relatively constant after changes in perfusion pressure. Results of pub-lished experiments on the coronary circulation seem contradictory, not only relative to the presence or absence of autoregulation, but also in regard to the degree to which this process regulates coronary blood flow. Shaw et al.1 found coronary blood flow completely independent of perfusion pressure over a wide physiological pressure range. Eckel et al.-previously described experiments which could be interpreted as autoregulation in the coro-nary circulation. In these experiments2 coro-nary flow was found to return slowly toward control level after an initial rise or fall produced by sudden increases and decreases in perfusion pressure in a single artery. On the other hand, Cross and co-workers "•4 emphasized the dependence of flow on coro-nary driving pressure (aortic pressure minus left ventricular pressure) rather than on vasomotor responses. Steady state coronary resistance values which could be interpret-ed as evidence of autoregulation were found in 44 % of innervated, beating hearts studied by Scott et al.5 Gregg " described a bi-phasic initial flow response in a single artery when pressure in all major arteries was in-creased simultaneously by compression of th