The response of diastolic myocardial tissue pressure and regional coronary blood flow to increased preload from blood, colloid, crystalloid.

An increase in the left ventricular end-diastolic pressure (LVEDP), resulting from the intravenous administration of blood, a colloid solution, or a crystalloid solution, was accompanied by an increase in both the inner:outer left ventricular wall flow ratio and the diastolic myocardial tissue pressure gradient. With a normal left ventricular end-diastolic pressure, the normal inner:outer flow ratio was just above unity and the minimum diastolic myocardial tissue pressure in the subepicardium was twice as high as in the subendocardium. When the left ventricular end-diastolic pressure was raised, the subepicardial tissue pressure rose earlier and to a higher degree than the subendocardial; thus a gradient which encourages subendocardial flow was increased. This paper correlates the changes in diastolic myocardial tissue pressure and in inner:outer flow ratios which occurred when eight dogs were transfused with blood, seven with colloid, and seven with lactated Ringer's solution. Regional diastolic myocardial tissue pressure was measured by the flow-cessation technique and regional flow by radioactive microspheres. The gradient in diastolic myocardial tissue pressure, which is a major contributory factor to adequate subendocardial perfusion under normal conditions, is of even greater importance when LVEDP is raised.