FINITE STRAINS IN ANTERIOR AND POSTERIOR WALL OF CANINE LEFT-VENTRICLE

Piezoelectric crystals were implanted in the anterior and posterior midwall of the left ventricle in six anesthetized dogs to compare regional two-dimensional finite deformations. Increasing left ventricular end-diastolic pressure (LVEDP) from 3 to 18 mmHg caused a similar expansion in the end-diastolic configuration (similar end-diastolic principal strains), but maximal lengthening was more circumferential in the anterior wall (-18 +/- 13-degrees) and more longitudinal in the posterior wall (-54 +/- 19-degrees). End-diastolic in-plane shears were negative in both regions, consistent with a left-handed diastolic torsion. As LVEDP increased, maximal shortening strains increased similarly (similar end-systolic principal strains), but there was a preferential increase in end-systolic circumferential strain in the anterior wall and preferential increase in longitudinal strain in the posterior wall. End-systolic in-plane shears were small and positive in both regions. The circumferential strain accurately reflected maximal end-diastolic and end-systolic principal strains in the anterior wall at mid and high LVEDP but underestimated the maximal end-diastolic principal strain by 50% and the maximal end-systolic principal strain by 30% in the posterior wall at all LVEDPs. We conclude that the magnitude of end-diastolic and end-systolic strains is similar for anterior and posterior walls over a wide range of LVEDP. However, there are regional differences in the directions of maximal deformation that should be considered when evaluating regional ventricular function.