Frank–Starling law

The Frank–Starling law states that, within physiological limits, greater ventricular filling stretches cardiac muscle fibers and increases contraction force and stroke volume.

Preload: The stretch or load on ventricular muscle at the end of diastole, related to filling and end-diastolic volume. Ventricular filling sets the initial muscle stretch that drives the law.
Ventricular preload: The end-diastolic stretch or load experienced by ventricular muscle before it contracts. This cardiac-specific form of preload anchors the law’s input.
Left ventricular function curve: A plot relating left ventricular preload to a measure of ventricular pumping performance. It depicts the rising, then flattening, response to greater filling.
Otto Frank: A German physiologist whose experiments described relationships between cardiac muscle length, pressure, and contraction. His work established the ventricular mechanics later incorporated into the law’s name.
End-diastolic volume: The volume of blood in a ventricle at the end of diastole, just before contraction. It is a practical measure of the filling that increases fiber stretch.
Afterload: The load a ventricle must overcome to eject blood during systole. It can alter ejection independently of the filling-dependent increase in force.
Fluid responsiveness: The capacity of cardiac output or stroke volume to increase after a fluid challenge. It tests whether increased filling can still raise stroke volume in a particular patient.
Ernest Starling: A British physiologist who helped establish how the heart adjusts its output to venous return. His experiments extended the principle from isolated muscle to the working heart.
Sarcomere length–tension relationship: The relationship between a muscle sarcomere’s resting length and the force it can generate. Cardiac muscle produces greater active force over the physiological stretch range.
Myocardial contractility: The intrinsic capacity of cardiac muscle to generate force at a given initial fiber length. The law varies force with initial length, while contractility describes a separate influence.

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