Abstract
The assessment of left ventricular shape changes during cardiac revolution may be a new step in clinical cardiology to ease early diagnosis and treatment. To quantify these changes, only point registration was adopted and neither Generalized Procrustes Analysis nor Principal Component Analysis were applied as we did previously to study a group of healthy subjects. Here, we extend to patients affected by hypertrophic cardiomyopathy the original approach and preliminarily include genotype positive/phenotype negative individuals to explore the potential that incumbent pathology might also be detected. Using 3D Speckle Tracking Echocardiography, we recorded left ventricular shape of 48 healthy subjects, 24 patients affected by hypertrophic cardiomyopathy and 3 genotype positive/phenotype negative individuals. We then applied Generalized Procrustes Analysis and Principal Component Analysis and inter-individual differences were cleaned by Parallel Transport performed on the tangent space, along the horizontal geodesic, between the per-subject consensuses and the grand mean. Endocardial and epicardial layers were evaluated separately, different from many ecocardiographic applications. Under a common Principal Component Analysis, we then evaluated left ventricle morphological changes (at both layers) explained by first Principal Component scores. Trajectories’ shape and orientation were investigated and contrasted. Logistic regression and Receiver Operating Characteristic curves were used to compare these morphometric indicators with traditional 3D Speckle Tracking Echocardiography global parameters. Geometric morphometrics indicators performed better than 3D Speckle Tracking Echocardiography global parameters in recognizing pathology both in systole and diastole. Genotype positive/phenotype negative individuals clustered with patients affected by hypertrophic cardiomyopathy during diastole, suggesting that incumbent pathology may indeed be foreseen by these methods. Left ventricle deformation in patients affected by hypertrophic cardiomyopathy compared to healthy subjects may be assessed by modern shape analysis better than by traditional 3D Speckle Tracking Echocardiography global parameters. Hypertrophic cardiomyopathy pathophysiology was unveiled in a new manner whereby also diastolic phase abnormalities are evident which is more difficult to investigate by traditional ecocardiographic techniques.
Highlights
Hypertrophic cardiomyopathy (HCM), due to its genetic aetiology with dominant autosomal transmission and complete or incomplete penetrance, became a central subject in cardiology it presents a highly variable phenotypic, clinical and prognostic heterogeneity [1]
Our approach allows answering important physiological questions: a) given the intimate relationship “form and function”, which of these undergoes first the most serious modifications in affected individuals? b) which of these is the most resistant to alterations caused by HCM? c) is epicardium or endocardium in HCM patients the layer most setting apart from healthy individuals? d) is the natural epi-endocardial synchronism altered in HCM patients? e) is there any means to assess quantitatively direct diastolic indicators in HCM? f) is there any means to index genotype from phenotype in HCM? Question e) and f) were faced recently using echocardiographic studies
For static shape analyses, we evaluated the pure shapes in the size and shape space, the shapes transported in the size and shape space, the shapes transported in the shapes space and, for any of these datasets, the shape differences at any homologous time from the shape at the R peak, i.e. in the same manner the 3DSTE parameters are computed
Summary
Hypertrophic cardiomyopathy (HCM), due to its genetic aetiology with dominant autosomal transmission and complete or incomplete penetrance, became a central subject in cardiology it presents a highly variable phenotypic, clinical and prognostic heterogeneity [1]. Several authors provided a huge amount of studies (whose complete review is not the scope of the present paper) illustrating functional LV impairments in HCM patients. None of these used modern shape deformation analysis to evaluate LV shape changes in HCM and g+p- individuals via speckle tracking. This approach could help diagnosis and prevention by looking for new preclinical indicators during diastole
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