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Published on: June 14, 2016
Structural and Functional Characterization of the Aorta in Hypertrophic Obstructive Cardiomyopathy
Ayman M Ibrahim1,2,3, Mohamed Roshdy1, Najma Latif4,5
1Aswan Heart Center, Magdi Yacoub Heart Foundation, Egypt (A.M.I., M.R., A. Elsawy, M.H., S.H., W.E., A. Elaithy, A. Elguindy, A. Afifi, Y.A., M.Y.).
Insights
Hypertrophic cardiomyopathy (HCM) causes aortic wall stiffness due to structural changes in smooth muscle cells and extracellular matrix. These alterations in hypertrophic cardiomyopathy patients indicate potential arterial dysfunction.
Area of Science:
- Cardiovascular Research
- Cardiomyopathy Studies
- Aortic Wall Mechanics
Background:
- Hypertrophic cardiomyopathy (HCM) affects not only the myocardium but also extracardiac tissues.
- Investigating aortic structural and functional changes in obstructive HCM is crucial.
Purpose of the Study:
- To elucidate the structural and functional alterations in the ascending aorta of obstructive hypertrophic cardiomyopathy patients.
- To correlate aortic changes with clinical and molecular parameters in HCM.
Main Methods:
- Histological, immunohistochemical, and electron microscopy analysis of aortic biopsies from 101 HCM patients and 9 controls.
- Quantitative assessment of protein expression and morphometry.
- Measurement of pulse wave velocity using cardiac magnetic resonance in 85 HCM patients and 117 controls.
Main Results:
- HCM aortas showed decreased medial lamellar units, increased interlamellar distance, and wall thickness.
- Alterations in extracellular matrix components (collagen, elastin) and smooth muscle cell markers were observed.
- Significantly higher pulse wave velocity in HCM patients correlated with disease severity.
Conclusions:
- Obstructive HCM is associated with increased aortic wall stiffness.
- Structural changes in the medial lamellar unit, smooth muscle cells, and extracellular matrix contribute to aortic dysfunction in HCM.
- These findings highlight potential arterial dysfunction in HCM patients.
Background:
Changes in the phenotype and genotype in hypertrophic cardiomyopathy (HCM) are thought to involve the myocardium as well as extracardiac tissues. Here, we describe the structural and functional changes in the ascending aorta of obstructive patients with HCM.
Methods:
Changes in the aortic wall were studied in a cohort of 101 consecutive patients with HCM undergoing myectomy and 9 normal controls. Biopsies were examined histologically, immunohistochemically, and by electron microscopy. Changes in protein expression were quantified using morphometry and Western blotting. Pulse wave velocity was measured using cardiac magnetic resonance in 85 patients with HCM and compared with 117 age-matched normal controls.
Results:
In HCM, the number of medial lamellar units was significantly decreased, associated with an increase in interlamellar distance and aortic wall thickness, as compared with controls. Electron microscopy showed an altered lamellar structure with disorientation of elastin fibers from the circumferential direction. There was a significant decrease in collagen content, α-smooth muscle actin, smooth muscle myosin, smooth muscle 22 and integrin β1, as well as a significant increase in calponin and caspase-3. Fibulins 1, 2, and 5 showed reduced expression in HCM-aortic biopsies. Functionally, pulse wave velocity was significantly higher in patients with HCM compared with healthy controls, with an association between higher pulse wave velocity and more severe molecular and clinical parameters.
Conclusions:
The increased wall stiffness observed in the aortas of obstructive patients with HCM is associated with structural alterations in the medial lamellar unit, including changes in smooth muscle cells and the extracellular matrix, indicating potential arterial dysfunction.
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