The coronary pressure-flow determinants left ventricular compliance in dogs

Displacement of the left ventricular diastolic pressure-dimension relationship (change in compliance) has been observed with alterations in coronary perfusion pressure. The relative contribution of coronary (myocardial) blood flow, as compared with the perfusion pressure at which flow occurs, was studied in 10 dogs during diastolic relaxation potassium arrest during cardiopulmonary bypass. The normalized left ventricular pressure-dimension relationships, obtained during passive, gradual filling of the left ventricle (0-20 mm Hg) were shifted progressively to the left as coronary perfusion pressure was increased. Myocardial blood flow was 0.06 ml/mg per min +/- 0.02 ml/mg per min (mean +/- SEM) at a coronary perfusion pressure of 40 mm Hg and increased to 0.38 ml/mg per min +/- 0.11 ml/mg per min as the coronary perfusion pressure was raised to 120 mm Hg. Addition of adenosine significantly increased myocardial blood flow by 109% at a coronary perfusion pressure of 80 and by 147% at a coronary perfusion pressure of 120 mm Hg, but caused no additional significant shifts in the pressure-dimension relationships, compared to the same coronary perfusion pressures without adenosine. Coronary perfusion pressure, and not coronary blood flow, is a more direct determinant of cardiac diastolic properties.