Coronary vasodilation shifts the diastolic pressure-dimension curve of the left ventricle.

The volume of blood in the left ventricular wall increases as coronary perfusion pressure or coronary blood flow increase, but it is unclear whether such an increase in volume can acutely alter the diastolic pressure-dimension relationship of the intact, working left ventricle. In 19 dogs, we measured left ventricular pressure with a catheter tip transducer and dimensions with an epicardial echo transducer and, during each experiment, compared the diastolic pressure-dimension relationship during two states of coronary blood flow: control and maximal vasodilation (induced by intravenous chromonar). Diastolic pressure-dimension relationships for diastolic pressures from 0 to 25 mmHg were obtained during transfusion with blood in 11 dogs with the pericardium open and in eight dogs with the pericardium closed. Left ventricular epicardial diameter did not change during maximal coronary blood flow compared with control, but endocardial diameter was less, wall thickness was greater, and the diastolic pressure-dimension relation was shifted to the left. The average magnitude of the increase in diastolic pressure at comparable diastolic dimensions was small when the pericardium was open (2.6 mmHg) and larger when the pericardium was closed (4.1 mmHg). The mechanism of this shift appears to be an alteration of the ratio of diastolic chamber volume to wall volume. Interaction of diastolic pressures between the right and left ventricles may contribute to the larger increase in diastolic pressure with the pericardium closed.