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Lusitropy Definition, Meaning, Positive Lusitropy, Negative Lusitropy

   

Lusitropic is also called diastolic properties. Relaxation occurs by the removal of calcium ions from the endoplasmic reticulum. Sarcoplasmic reticulum have ATPase pump and Na /Ca exchanger that is responsible for 90% removal of calcium ions. On cellular level, the procedure of relaxation is energy consuming which requires ATP , then releases calcium from sarcoplasmic reticulum for its uptake. Left ventricle of heart relaxation begins at the late ejection phase and it continues thoroughly during early rapid filling ends when ventricles are fully relaxed. Lusitropy properties can also be described by both active and passive relaxation. The increase in calcium level in the heart cells that will lead to increase in contraction and decrease relaxation (lusitropy)


For the proper ventricular systolic function inotropy, lusitropy, preload and afterload collectively play an important role in normal healthy heart rate. Change in any one of the factor may alter the function of heart.

Stimulation of beta adrenoreceptors also play a vital role for the lusitropy effect, it has a high sensitivity to beta adrenoreceptor excitation, lusitropy response becomes more efficiently due to increase in cyclic AMP. Lusitrophy results in increase in cardiac output and systolic blood pressure.
Lusitrophy can be detected by measuring the velocity of heart tissues by Tissue Doppler Timing (TDI), in this procedure E wave declared the time of relaxation period on echocardiographic examination. Another way of accessing diastolic feature of heart is speckle tracking echocardiography, where heart muscle (myocardium) are tracked to determine myocardial velocity and strain (which is the change in velocity at particular time period). In case left ventricular is not functioning properly or in disease state, relaxation is delayed.

Lusitropy Definition, Meaning, Positive Lusitropy, Negative Lusitropy

Positive Lusitropy


The activation of sympathetic nervous system increase the heart rate acceleration, increase in cardiac contractility and also increase relaxation called as positive lusitropy. These factors prepared the body for fight or flight response with the release of catecholamines ( nor epinephrine and epinephrine). Increase in cyclic AMP, leads to phosphorylation of receptor present in the sarcoplasm reticulum. This will enhance the greater degree of calcium removal and with the help of catecholamines will lead to relaxation. when next action potential arrives it will leads to positive inotropy effects.
Milrinone and dobutamine are mostly prescribed for the positive lusitropic effects

Negative Lusitropy


The activation of parasymphatheic nervous system decreases the heart rate, cardiac contractility, also rate of relaxation called as negative lusitropy. These factors prepared the body for rest and digest response with the release of acetylcholine. It leads to increase in vagal tone resulting in low heart rate. Relaxation is effected by two major factors, first one is increase in quantity of calcium in the cell and second one is ATPase and Na /Ca exchanger pump that take calcium out of cell will not working properly.

Atropine is used to treat negative lusitropy. it inhibits parasympathetic activity and leads to normal relaxation


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