Multiscale characterization of left ventricle active behavior in the mouse
Sunder Neelakantan1, Mohit Kumar2, Emilio A Mendiola1
1Department of Biomedical Engineering, Texas A&M University, College Station, TX, USA.
Acta Biomaterialia
|March 24, 2023
Summary
This study developed a multiscale method to measure heart muscle contraction from fiber to organ. Findings reveal how active forces in the left ventricle free wall differ from single fibers, crucial for understanding heart failure.
Area of Science:
- Cardiovascular Physiology
- Biomechanical Engineering
- Cardiac Mechanics
Background:
- Cardiac systolic function relies on coordinated contraction across multiple length scales, from sarcomeres to the whole organ.
- Understanding the translation of active tension from the fiber level to organ-level function is critical for diagnosing and treating heart diseases like heart failure.
- While passive myocardial mechanics are well-studied, active contractile behavior across scales remains less understood, particularly at the tissue level.
Purpose of the Study:
- To develop and present a novel multiscale methodology for characterizing the active contractile behavior of the left ventricle free wall (LVFW) in mice.
- To establish a comprehensive understanding of cardiac contractility from the single-fiber level to the whole-organ level.
- To investigate the relationship between myocardial architecture and directional contractility.
Main Methods:
- Developed a multiscale experimental pipeline integrating active tests on papillary muscle fibers, LVFW myocardial tissues, and in vivo organ-level contractility measurements in mice.
- Quantified myocardial architecture using histology to analyze the directionality of tissue-level contractility.
- Performed isometric active tests to characterize activation-relaxation behavior and stress development in LVFW tissues.
Main Results:
- LVFW tissue activation-relaxation dynamics were qualitatively similar to papillary muscle fiber bundles but with significantly lower maximum stress and longer plateau times.
- LVFW tissues exhibited direction-dependent active stress generation, with larger stresses in the longitudinal compared to the circumferential direction.
- Active stress relaxation occurred faster in directions with higher peak stresses, contrasting with passive viscoelastic behavior.
Conclusions:
- The developed multiscale approach provides crucial insights into the active contractile behavior of the myocardium across different length scales.
- Results highlight significant differences in active stress generation and relaxation dynamics between single muscle fibers and the myocardial wall.
- This research lays the groundwork for understanding multiscale mechanisms underlying impaired cardiac function in conditions like heart failure.
