In summary, we have examined the response to arterial vasoconstriction in an in vitro coronary artery preparation. Without a preexisting stenosis, arterial vasoconstriction had minimal hemodynamic effects. Similarly, with a stenosis created by a circumferential snare, arterial vasoconstriction had minimal hemodynamic effects. In striking contrast, with a stenosis created by intraluminal obstruction, arterial vasoconstriction dramatically increased the hemodyamic severity of the stenosis. The use of an intraluminal obstruction provides a useful animal model for examining hemodynamics in coronary artery disease and had provided some insight into the effects of vasoconstriction on coronary artery hemodynamics. Obviously, this is an experimental study, and care must be taken in extrapolating these results to diseased human coronary arteries.