Aims: Hypertrophic cardiomyopathy (HCM) is a disease with marked regional differences in wall thickness. However, the relation between myocardial function and wall thickness has not been well studied. Ultrasonic strain rate (SR) imaging makes it possible to study the regional myocardial deformation. We investigated whether regional systolic deformation is reduced in paediatric patients with HCM and evaluated its relation with wall thickness, electrocardiographic pattern, and exercise capacity.
Methods and results: We studied 41 children with asymmetric HCM (mean age 12.3 years) and 29 controls. Electrocardiograms, exercise testing (when feasible), and echocardiograms with tissue Doppler imaging were performed. Peak systolic SR, strain, post-systolic shortening, and time to maximal strain were calculated in the longitudinal direction from the basal septum, mid-septum, and basal lateral myocardial segments and in the radial direction from the basal antero-septal and infero-lateral myocardial segments. Children with HCM had a significant reduction in deformation in all myocardial segments when compared with controls. In the HCM group, peak systolic SR and strain were significantly lower in the basal septum when compared with the mid-septal and basal lateral myocardial segments. In the basal septum, post-systolic shortening was significantly higher and time to maximal strain significantly longer than in mid-septal and lateral myocardial segments. A strong inverse curvilinear relation between peak systolic strain and wall thickness was found (r = -0.86, P < 0.001), with no further decrease in the regional myocardial function demonstrated once maximal wall thickness exceeded a Z-score of 3.5. Peak systolic strain in the basal part of the septum correlated inversely with exercise capacity (r = 0.68, P < 0.01).
Conclusion: Systolic deformation is significantly and inhomogeneously reduced in children with HCM. This reduction in myocardial function is related to maximal wall thickness and decreased exercise capacity.