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.