An Exploratory Assessment of Focused Septal Growth in Hypertrophic Cardiomyopathy

Growth and Remodelling (G&R) processes are typical responses to changes in the heart’s loading conditions. The most frequent types of growth in the left ventricle (LV) are thought to involve growth parallel to (eccentric) or perpendicular to (concentric) the fiber direction. However, hypertrophic cardiomyopathy (HCM), a genetic mutation of the sarcomeric proteins, exhibits heterogeneous patterns of growth and fiber disarray despite the absence of clear changes in loading conditions. Previous studies have predicted cardiac growth due to increased overload in the heart [7, 12, 23] as well as modelled inverse G&R post-treatment [1, 14]. Since observed growth patterns in HCM are more complex than standard models of hypertrophy in the heart, fewer studies focus on the geometric changes in this pathological case. By adapting established kinematic growth tensors for the standard types of hypertrophy in an isotropic and orthotropic material model, the paper aims to identify different factors which contribute to the heterogeneous growth patterns observed in HCM. Consequently, it was possible to distinguish that fiber disarray alone does not appear to induce the typical phenotypes of HCM. Instead, it appears that an underlying trigger for growth in HCM might be a consequence of factors stimulating isotropic growth (e.g., inflammation). Additionally, morphological changes in the septal region resulted in higher amounts of incompatibility, evidenced by increased residual stresses in the grown region.