Comparison of left ventricular free wall and septal diastolic compliance in the dog

Septal to free wall dimensions are frequently employed for the analysis of diastolic compliance. However, the diastolic properties of these anatomically distinct regions of left ventricle are not well characterized. Regional compliance was studied in eight open-chest anesthetized dogs. Pairs of 2-mm-diameter piezoelectric crystals were implanted in the left ventricular free wall or septum 1.38 +/- 0.06 cm apart at a midwall location 58% +/- 1.9 of the left ventricular endocardial-epicardial or left ventricular endocardial-right ventricular endocardial distance. Left ventricular end-diastolic pressure was increased from an average of 8.1-21.0 mmHg, with a resulting average maximum end-diastolic strain of 11% (end-diastolic (ED) segment length/control ED length). Regional stiffness was assessed at all sites based on the relationship between left ventricular end-diastolic pressure and regional strain. Neither strain nor calculated stiffness coefficients differed significantly among the three sites. Septal transmural pressure (left ventricular end-diastolic pressure--right ventricular end-diastolic pressure) was nearly constant as left ventricular end-diastolic pressure increased during volume infusion and thus did not account for the observed septal strain.