Myocardial deformation abnormalities in pediatric hypertrophic cardiomyopathy: are all etiologies identical?

Hypertrophic cardiomyopathy (HCM) is a disease with a heterogeneous clinical and morphological presentation. It can be secondary to mutations in genes encoding for sarcomeric and non-sarcomeric proteins. The pattern of ventricular hypertrophy can vary from isolated basal septal to concentric hypertrophy. We investigated if there are differences in regional myocardial function in different forms of HCM.

We performed echocardiograms on children with (i) isolated asymmetric septal HCM, (ii) isolated concentric HCM, (iii) Friedreich's ataxia associated with concentric HCM, and (iv) healthy controls. Wall thickness, left ventricular dimensions, ejection fraction, and mitral inflow were measured. Peak early diastolic myocardial velocities, peak systolic myocardial velocities, peak systolic strain rate (SR), peak systolic strain (epsilon), post-systolic shortening and time to maximal epsilon were measured in the basal and mid-septum and basal lateral wall to evaluate longitudinal myocardial function. Similar data were acquired and analysed in the anterior septum and infero-lateral wall to evaluate the radial myocardial function. All three groups with HCM had had increased wall thickness, reduced left ventricular dimensions, and evidence of impaired diastolic filling compared to controls. All forms of HCM had reduced early diastolic and systolic myocardial velocities and peak systolic SR and peak systolic epsilon compared with controls in all myocardial segments investigated. Children with asymmetric septal HCM had reduced systolic deformation, increased post-systolic shortening, and prolonged time to maximal epsilon in the basal septum compared with the other two groups with HCM. There were no differences in any echocardiographic variable between patients with isolated concentric HCM and Friedreich's ataxia and resulting HCM.

Myocardial deformation is abnormal in all forms of paediatric HCM. Myocardial deformation is more reduced and associated with post-systolic shortening in the more hypertrophied basal septum in patients with asymmetric septal HCM. In contrast, this reduction is uniformly distributed in all myocardial segments in patients with concentric HCM irrespective of whether HCM results from isolated or secondary HCM. Our findings suggest the pattern of hypertrophy influences myocardial deformation more than the underlying cause of HCM.