Load Independent Contractility
Load Independent Contractility - Related Videos
08:08
Measurement of Cytosolic Ca2+ in Isolated Contractile Lymphatics
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Cited by 24 •
2011
We introduce an approach to evaluate the cytosolic Ca2+ concentration in isolated lymphatics to study Ca2+-dependent and Ca2+-sensitizing mechanisms of lymphatic smooth muscle contraction.
02:15
The Contractile Ring
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2023
Contractile rings are composed of microfilaments and are responsible for separating the daughter cells during cytokinesis. Contractile ring assembly proceeds along with other cell cycle events; however, very few mechanistic details are known about the timing and coordination of the contractile rings with the cell cycle. A small GTPase, RhoA, controls the function and assembly of the contractile ring. RhoA belongs to the Ras superfamily of proteins. The activation of formins by RhoA promotes...
02:15
The Contractile Ring
0 Views •
2021
Contractile rings are composed of microfilaments and are responsible for separating the daughter cells during cytokinesis. Contractile ring assembly proceeds along with other cell cycle events; however, very few mechanistic details are known about the timing and coordination of the contractile rings with the cell cycle. A small GTPase, RhoA, controls the function and assembly of the contractile ring. RhoA belongs to the Ras superfamily of proteins. The activation of formins by RhoA promotes...
01:21
Introduction to Test of Independence
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2025
In statistics, the term independence means that one can directly obtain the probability of any event involving both variables by multiplying their individual probabilities. Tests of independence are chi-square tests involving the use of a contingency table of observed (data) values. The test statistic for a test of independence is similar to that of a goodness-of-fit test: where: O = observed values E = expected values (which should be at least 5) A test of independence determines whether...
01:16
Hypothesis Test for Test of Independence
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2023
The test of independence is a chi-square-based test used to determine whether two variables or factors are independent or dependent. This hypothesis test is used to examine the independence of the variables. One can construct two qualitative survey questions or experiments based on the variables in a contingency table. The goal is to see if the two variables are unrelated (independent) or related (dependent). The null and alternative hypotheses for this test are: H0: The two variables (factors)...
FAQs
Pressure-volume analysis separates myocardial performance from the effects of how much blood enters the ventricle and the pressure it must overcome. Investigators alter ventricular loading conditions, then examine how pressure and volume change across those conditions. This produces relationships that emphasize intrinsic force generation rather than treating a single beat’s ejection as a complete measure of contractile function.
End-systolic elastance, or Ees, is calculated as the slope of the end-systolic pressure-volume relationship. Its value summarizes how end-systolic pressure changes in relation to end-systolic volume while loading conditions are varied. In this framework, the slope serves as an index of myocardial performance because the calculation is designed to reduce the confounding effects of preload and afterload.
Stroke volume and ejection fraction describe how much blood leaves the ventricle relative to its filling, but both can change when preload or afterload changes. A favorable ejection value therefore does not necessarily isolate the muscle’s force-generating capacity. Load-independent assessment adds pressure-volume relationships to provide a more direct estimate of ventricular contractility than either measure alone.
A basic assessment begins by recording ventricular pressure and volume while altering loading conditions. The resulting beats are compared to identify the end-systolic pressure-volume relationship, and its slope is calculated as end-systolic elastance. The essential outcome is not a single pressure or volume value, but the relationship formed across different loading states.
Because the approach examines performance across changing loading conditions, it can help distinguish an intervention’s effect on myocardial contractility from effects caused by altered filling or arterial pressure. This distinction is useful when interpreting drug responses or other interventions. The resulting pressure-volume relationships provide a more focused measure of ventricular performance than changes in ejection fraction alone.
This framework is particularly relevant to studies of ventricular function, heart failure, and cardiac disease. It allows investigators to characterize myocardial performance while minimizing the influence of changing preload and afterload, which can otherwise complicate interpretation. It is also useful for evaluating how drugs or other interventions affect the heart’s intrinsic contractile behavior.