Abstract 14413: Stress-Corrected Circumferential Myocardial Shortening is Reduced in All Layers in Patients with Hypertrophic Cardiomyopathy

Abstract

Background: Hypertrophic cardiomyopathy (HCM) is associated with reduced longitudinal myocardial strain despite preserved left ventricular (LV) ejection fraction (EF). In contrast, circumferential strain (CS) has been reported to be increased or decreased according to the studies. Layer-specific myocardial strains can now be measured at innermost, midwall, and outermost LV layers by using 2-dimensional speckle tracking imaging. We thus aimed to determine whether layer-specific CS is reduced in patients with HCM.

Methods: Echocardiography was performed in 51 HCM patients and 30 healthy, age-matched control subjects. The parasternal LV short-axis view was recorded at the mid-ventricular level by using an Artida system (Toshiba Medical Systems) and layer-specific segmental CS was measured based on the speckle tracking. Layer-specific segmental end-systolic circumferential wall stress (WS) was calculated according to Mirsky’s formula, specially using segmental wall thickness. Stress strain product (SSP), WS×(-CS), was calculated in each layer as an index of stress-corrected myocardial shortening. LV EF was measured using biplane method of disks.

Results: Interventricular septal thickness (18 ± 6 vs 9 ± 1 mm, p<0.001), LV posterior wall thickness (10 ± 1 vs 8 ± 1 mm, p<0.001), and LV mass index (163 ± 47 vs 79 ± 13 g/m², p<0.001) were significantly greater in HCM than control. LV EF was significantly greater in HCM (71 ± 7 vs 65 ± 6%, p<0.001). Segmental WS was lower in HCM than in control in all 3 layers (inner: 790 ± 136 vs 1040 ± 127 dynes/mm², p<0.001; mid: 243 ± 112 vs 536 ± 130, p<0.001; outer: 155 ± 83 vs 389 ± 110, p<0.001). Segmental CS was reduced in HCM in midwall (-12 ± 6 vs -14 ± 5%, p<0.001) and outer layer (-8 ± 5 vs -10 ± 4%, p<0.01), but not in inner layer (-25 ± 8 vs -25 ± 7%, p=NS). SSP was lower in HCM in all 3 layers (inner: 198 ± 66 vs 259 ± 74 dynes/mm², p<0.001; mid: 31 ± 23 vs 77 ± 34, p<0.001; outer: 14 ± 12 vs 38 ± 22, p<0.001).

Conclusions: Stress-corrected circumferential myocardial shortening was reduced in all 3 layers in HCM, indicating that intrinsic myocardial contraction is impaired across all LV layers in this disease.