Comparison between three-dimensional strain in the anterior and posterior walls during left ventricular ejection

We examined the pattern of deformation in the anterior and posterior free walls of the normal left ventricle for a wide range of chamber volumes before and after ejection (pre- and afterloads) under well-defined boundary conditions. Local three-dimensional Lagrangian strains in four isolated, blood-perfused dog hearts were measured by biplane cineradiography of radiopaque beads implanted between midwall and the outside surface (epicardium) at both sites. Anterior and posterior subepicardial strains throughout various cardiac cycles were computed with respect to the state at which the left ventricle was filled to its maximum volume. During ejection, the approximately linear relations between all six strain components for either site and left ventricular volume (V) were nearly independent of preload and afterload, similar to previous observations in the lateral wall. On average, mean meridional (E₂₂) and radial strains during ejection (E₃₃) were significantly greater in the anterior wall (-0.045±0.006 and 0.183±0.022) than in the posterior wall (-0.024±0.007 and 0.093±0.013). In all four hearts, the mean transverse shear strain during ejection E₂₃ was significantly different on the anterior (-0.023±0.011) and posterior walls (-0.034±0.009). Also, changes in three of the six strain components with ejected volume (ΔE₃₃/ΔV, ΔE₁₂/ΔV, ΔE₁₃/ΔV) varied significantly between the anterior (-0.0108±0.0011, -0.0067±0.0003, 0.0014±0.0006 ml^-1) and posterior subepicardium (-0.0059±0.0006, -0.0018±0.0001, -0.0001±0.0007 ml^-1). Left ventricular geometric differences i.e., the rather flat posterior free wall, may be responsible for these variations.