Hypertrophic cardiomyopathy: Functional aspects by tagged magnetic resonance imaging

Studies addressing the issue of regional function in hypertrophic cardiomyopathy patients (HCM) are reviewed. The relationship between regional wall thickness and function in these patients was studied by three dimensional (3D) tagged magnetic resonance imaging (MRI) utilizing the volume-element approach. Regional function was indexed by myocardial thickening and circumferential shortening and related to the local thickness and wall stress index. An inverse relationship was found between wall thickening and thickness as well as between circumferential shortening and wall thickness. Lower stresses were obtained for thicker myocardial segments. Function of the normal-thickness regions was enhanced in the HCM patients relative to the normal subjects. Thicker segments in patients with HCM are thus characterized by reduced systolic function, which occurs at segments with relatively low stress levels. This pattern is consistent with the hypothesis that the thick myocardial segments have reduced contractile activity, probably due to recently identified mutations in the gene responsible for production of β heavy chain myosin as well as other contractile proteins.