Lusitropy is a term used to describe myocardial relaxation. The increase in calcium uptake by cardiomyocytes leads to increased myocardial contractility (positive inotropic effect), but the myocardial relaxation, or lusitropy, decreases.

[edit] Positive

Increased catecholamine levels promote positive lusitropy, enabling the heart to relax more rapidly.

[edit] 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 too easily, relaxation will become more difficult.

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