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Regional dysfunction correlates with myofiber disarray in transgenic mice with ventricular expression of ras
W J Karlon1, A D McCulloch, J W Covell
1Department of Bioengineering, University of California San Diego, La Jolla, California 92093, USA.
Insights
Focal myofiber disarray in hypertrophic cardiomyopathy is linked to impaired heart function. This study shows myofiber disarray reduces septal torsion and surface shortening in mouse models.
Area of Science:
- Cardiology
- Biomedical Engineering
- Pathology
Background:
- Familial hypertrophic cardiomyopathy is characterized by focal myofiber disarray.
- Regional ventricular dysfunction is observed in hypertrophic cardiomyopathy patients.
- A direct correlation between regional dysfunction and myofiber disarray remains unestablished.
Purpose of the Study:
- To investigate the relationship between myofiber disarray and septal surface strain.
- To determine if myofiber disarray impacts regional cardiac function.
Main Methods:
- Utilized a transgenic mouse model with ventricular expression of the human oncogene ras, inducing regional myofiber disarray.
- Employed an isolated ejecting mouse heart preparation to record septal surface deformation.
- Generated nonhomogeneous septal surface strain maps and correlated them with histological myofiber disarray.
Main Results:
- Myofiber disarray near the right ventricle (RV) septal surface was associated with significantly smaller maximum principal shortening.
- Disarray near the RV surface or at the midwall correlated with significantly smaller surface shear strain.
- Surface shear strain serves as a local indicator of cardiac torsion.
Conclusions:
- Myofiber disarray is associated with reduced septal torsion.
- Focal myofiber disarray leads to diminished regional surface shortening.
- These findings provide direct evidence linking myofiber disarray to regional cardiac dysfunction.
Abstract:
A hallmark of certain cardiac diseases such as familial hypertrophic cardiomyopathy is focal myofiber disarray. Regional ventricular dysfunction occurs in human subjects with hypertrophic cardiomyopathy; however, no direct evidence exists to correlate regional dysfunction with myofiber disarray. We used a transgenic mouse, which exhibits regional myofiber disarray via ventricular expression of the human oncogene ras, to investigate the relationship between myofiber disarray and septal surface strain. An isolated ejecting mouse heart preparation was used to record deformation of markers on the septal surface and to determine nonhomogeneous septal surface strain maps. Myofiber disarray made in histological tissue sections was correlated with gradients in surface systolic shortening. Significantly smaller maximum principal shortening was associated with disarray located near the right ventricle (RV) septal surface. There was also significantly smaller surface shear strain associated with disarray located either near the RV surface or at the midwall. Because surface shear is a local indicator of torsion, we conclude that myofiber disarray is associated with reduced septal torsion and reduced surface shortening.
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