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Morphological and mechanical examination of the atrial 'intima'
David Schwartzman1, Karen Schoedel, Donna Beer Stolz
1Heart and Vascular Institute, University of Pittsburgh, UPMC Presbyterian, B535, Pittsburgh, PA 15213 2582, USA.
Insights
The left atrial intima thickens with age and significantly contributes to atrial wall stiffness, while the right atrial intima does not change. This study investigated atrial intima morphology and mechanics in individuals across different age groups.
Area of Science:
- Cardiovascular Research
- Anatomical Pathology
- Biomechanical Engineering
Background:
- The atrial intima, defined as the tissue between the endocardium and myocardium, is crucial for atrial function.
- Understanding its developmental and mechanical properties is essential for diagnosing cardiac conditions.
Purpose of the Study:
- To investigate the morphological and mechanical characteristics of the atrial intima in individuals without cardiovascular disease.
- To determine how atrial intima thickness and stiffness change with age.
Main Methods:
- Post-mortem atrial tissue samples were collected from infants, children, and adults.
- Light and electron microscopy were used to measure atrial intimal thickness and collagen bundle organization.
- Planar biaxial testing assessed passive atrial wall stiffness.
Main Results:
- Left atrial intima thickness significantly increased with age, particularly in adults.
- Left atrial collagen bundles became less organized and thicker in adults compared to younger groups.
- The atrial intima was identified as the primary contributor to passive atrial wall stiffness.
Conclusions:
- The left atrial intima undergoes age-related changes in thickness and ultrastructure.
- The left atrial intima is the main determinant of atrial wall stiffness.
- These findings highlight the intima's role in atrial mechanics and potential implications for cardiovascular health.
Aims:
To examine morphology and mechanical properties of the atrial 'intima', which we defined as the tissue interposed between atrial endocardium and myocardium, in patients without known cardiovascular disease.
Methods And Results:
Post-mortem right and left atrial tissue was obtained from male infants (<1 year, n = 4), children (10-19 years, n = 4), and adults (58-69 years, n = 7). Using light microscopy and an ocular micrometer, atrial intimal (AIT) thickness was measured. Intimal collagen bundle thickness was measured using electron microscopy. Passive atrial wall stiffness was measured using a planar biaxial testing device. Among infants, left AIT (0.2 ± 0.2 mm) and right (0.2 ± 0.1 mm) AIT were not significantly different (P = 0.84). Among children, left AIT (0.6 ± 0.2 mm) was significantly greater than right (0.2 ± 0.1 mm) AIT (P = 0.03), and left AIT was marginally greater than in infants (P = 0.07). Among adults, with the exception of the appendage region, left AIT (1.0 ± 0.2 mm) was markedly greater than right AIT (0.3 ± 0.1 mm; P < 0.05), and left AIT was significantly greater than that in other age groups (P < 0.05). There were no differences in right AIT among age groups. Left intimal collagen bundle thickness was greater in adults (0.0512 ± 0.0056 µm) than infants (0.0432 ± 0.0071 µm) or children (0.0435 ± 0.0013 µm), and bundles were less organized. Wall stiffness was attributable primarily to the intima (1245 ± 132, vs. 260 ± 45 N/m(2) for the remaining atrial wall).
Conclusion:
The left atrial intima, but not the right, thickens with age, becomes more disorganized ultrastructurally, and is responsible for the majority of atrial wall stiffness.
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