The coronary hemodynamics of left main and branch coronary stenoses. The effects of reduction in stenosis diameter, stenosis length, and number of stenoses.

Although considerable investigation has been devoted to the concept of "critical" coronary stenosis, there is general lack of agreement on which coronary stenoses consistently decrease coronary blood flow (CBF). In 32 open-chest dogs we studied CBF and the aorta-distal coronary pressure gradient at rest and with reactive hyperemia (RH) as stenoses were created in the left coronary artery (LCA) or its major branches--anterior descending (LAD) or circumflex (LCx) arteries. The effects of stenosis location, reduction in stenosis diameter, stenosis length, and the number of stenoses were studied. Resting CBF and resting distal coronary pressure were decreased by short snare stenoses, which reduced the diameter of the LCA or either major branch more than 80%. Lengthening 50 to 60% LAD or LCx stenoses decreased CBF and increased the pressure gradient. There were small increases in pressure gradients but no change in CBF with multiple stenoses in either the LAD or LCx branch. During peak RH, CBF was decreased by a 60% LCA or branch snare stenosis. Peak RH CBF responses decreased further as length of an LAD or LCx stenosis increased. Multiple stenoses affected peak RH CBF responses significantly more than a single stenosis of the same total length. These data indicate that several anatomic variables of coronary stenosis affect the physiological responses of the coronary circulation. The variables are (1) reduction in lumen diameter, (2) length of stenosis, and (3) number of stenoses in one vessel.