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Frank-Starling mechanism
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The heart has a quiet way of adjusting to what reaches it, and it is called the Frank-Starling mechanism. The idea is simple: the force with which the heart muscle contracts depends on how stretched it was before it started.
During diastole, the moment when the heart fills, the blood coming in stretches the fibers of the myocardium, the heart muscle. The more volume that enters, the more stretched they end up, and within the normal range, the stronger the next contraction.
But stretch does not help indefinitely. There is an optimal length for the sarcomere, the unit that shortens inside the fiber; above or below it, tension drops. Think of a bow that shoots harder the more it is drawn, up to a point.
In systolic heart failure, when the heart pumps poorly, this mechanism cushions the fall in cardiac output.
In brief
The Frank-Starling mechanism links the starting length of the myocardial fiber to the force it generates when it contracts.
The larger the ventricular volume in diastole, the more its fibers stretch, and within the normal range the stronger the contraction.
There is an optimal sarcomere length: above or below it, tension drops.
A bow that shoots harder the more it is drawn, up to a point.
In systolic heart failure it cushions the fall in cardiac output.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Frank Starling Law, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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