Left ventricular anatomy in obstructive hypertrophic cardiomyopathy: beyond basal septal hypertrophy

Figures

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  Figure 1. HCMR statistical shape analysis pipeline. From a set of segmented endocardial and epicardial contours, automatic personalized 3D meshes are generated for each patient. (A)Statistical shape model is then built using a principal component analysis (PCA), which results in a set of anatomical modes or PCA modes (linear directions of anatomical change from the average shape) that capture the most common shape changes in the cohort. A Fisher linear discriminant analysis (LDA) is finally used to explore the characteristic phenotypes associated with left ventricular outflow tract obstruction in HCM under different conditions.

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  Figure 2. Flow chart of study design resulting in the six different groups studied. HCMR, Hypertrophic Cardiomyopathy Registry; LV, left ventricular; LVOT, left ventricular outflow tract; SSM, statistical shape model.

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  Figure 3. HCMR statistical shape analysis. Most relevant PCA modes of variation showing significant differences between groups. Box-plots represent the distribution of Z-scores along each axis for each group: 1. Non-obstructive cases at rest (blue/first row – R−); 2. Obstructive cases at rest (green/second row – R+); 3. Non-obstructive cases at rest and stress (red/third row – R−S−); 4. Obstructive cases at stress but not at rest (dark blue/fourth row – R−S+). The average of the population is represented by a dark blue/middle cross (Z-score 0). Orange/left cross and shapes show −3 SD from the average shape; purple/right cross and shapes, +3 SD. Mode 1 shows changes in LV size and length, as well as basal septal hypertrophy. Mode 2 captured LV length and sphericity variations. Mode 8 captured a global concentric remodelling, with marked septal hypertrophy. Mode 10 shows the presence of apical dilatation. Mode 11 shows curvature changes around the septum. Mode 12 captured changes in the septal wall thickening location. LVOT location is clarified with a red arch (note Bull's eye plot (right) is viewed from the apex, model views are from lateral (left) and base (middle)). Red dot: septal wall…

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  Figure 4. HCMR signature of LVOTO. Set of linear discriminant axes that characterize the role of LV shape in obstructive HCM (oHCM). Boxplots represent the Z-score distributions along each axis for each group. Orange/left cross and 3D shapes show −3SD from the average shape (blue/middle cross); purple/right cross and shape, +3SD. (A) LDArest: Linear discriminant axis between non-obstructive HCM cases at rest (blue/first row – R−) and obstructive HCM (oHCM) cases at rest (green/second row – R+). (B) LDA∆stress: Linear discriminant axis between non-obstructive HCM cases at rest and stress (red/first row – R−S−) and obstructive HCM cases at stress but not at rest (dark blue/second row – R−S+). Genotype negative (yellow/third row – G−) and genotype positive (black/fourth row – G+) scores are projected along the LDArest and LDA∆stress. (C) LDAgen: Linear discriminant axis between genotype negative (yellow/first row – G−) and genotype positive (black/second row – G+) cases. Black arch: LVOT location (note Bull's eye plot (bottom) is viewed from the apex, model views are from lateral (top-left) and base (top-right)). Red dot: Septal wall location. A, Anterior; I, Inferior; L, Lateral; S, Septal.

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  Figure 5. LV shape and LVOTO. Impact of LV shape on vortex formation during early systole, which changes the angle of attack of blood flow with respect to the mitral valve leaflets, increasing the systolic anterior motion of the mitral valve and consequently, LVOTO. Orange/left shape represents −3SD from the average shape along the LDArest axis (extreme non-obstructive HCM phenotype at rest). Purple/right shape, +3SD (obstructive HCM phenotype at rest). Phenotypes resulting from the LDA∆stress are overlayed with lines. An estimation of the left atrium, mitral valve, aorta, and aortic valve is shown with dotted lines.