The systolic pressure in the portion of an internal mammary artery which is within a myocardial tunnel may be much higher than aortic systolic pressure. The high pressure occurs in the distal portion of the tunnel and exists during the isovolumetric and ejection phases of myocardial systole. It occurs consistently in an implant which has passed initially into the inner half of the myocardium and inconsistently in more shallow implants. It is a result of systolic occlusion of the implant as it passes through different myocardial layers.
The presence of an implant-to-coronary pressure gradient during systole is probably another factor encouraging the formation of implant-to-coronary anastomoses and the subsequent flow through them.
- © 1969 American Heart Association, Inc.