Local pulsatile intramyocardial pressure (IMP) as a vector force: simultaneous measurements of IMP and tissue oxygen availability.

A directional nonuniformity of the intramyocardial pressure (IMP) was observed in anesthetized open-chest dogs using a piezoelectric pressure sensor implanted in the left ventricular myocardium. The nonuniformity seemed to be attributable to the variation in myocardial fiber orientation. The IMP, which developed in a direction parallel to the base-apex line, was measured in the deep portion of the myocardium, simultaneously with local O2 availability. In some cases, IMP decreased quickly as soon as a decrement in O2 availability had proceeded only slightly as a result of ligation of the anterior descending artery (LAD). In other cases, the once decreased IMP recovered gradually even when O2 availability remained lowered by continuation of the ligation. These observations indicated that IMP had no direct dependency on O2 availability in the case of acute LAD.