- Lusitropy
Lusitropy is a term used to describe
myocardial relaxation. The increase incalcium uptake bycardiomyocyte s leads to increased myocardial contractility (positiveinotropic effect), but the myocardial relaxation, or lusitropy, decreases.Positive
Increased catecholamine levels promote positive lusitropy, enabling the heart to relax more rapidly.
Negative
Relaxation of the heart is negatively impacted by the following factors:
1) Calcium overload - too much intracellular calcium
2) Rate of efflux of calcium through pumps - if calcium is not removed from the cell quickly enough
3) Impaired sarcoendoplasmic reticulum calcium ATPase (SERCA )- this channel in the myocyte pumps calcium from the cytoplasm of the cell into the endoplasmic reticulum.
4) TN-C binding affinity - TN-C (troponin C ) is a protein that affects the myosin-actin fibers of the heart. When calcium binds, it triggers contraction of the heart. If calcium binds to easily, relaxation will become more difficult.
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