Anrep effect

The Anrep effect is an autoregulation method in which myocardial contractility increases with afterload. It was experimentally determined that increasing afterload caused a proportional linear increase in ventricular inotropy.[1]

This effect is found in denervated heart preparations, such as the Starling Preparation, and as such, represents an intrinsic autoregulation mechanism.

The Anrep effect is named after Russian physiologist Gleb von Anrep,[2] who described it in 1912.

Functionally, the Anrep effect allows the heart to compensate for an increased end-systolic volume present and the decreased stroke volume that occurs when aortic blood pressure increases. Without the Anrep effect, an increase in aortic blood pressure would create a decrease in stroke volume that would compromise circulation to peripheral and visceral tissues.

Sustained myocardial stretch activates tension dependent Na⁺/H⁺ exchangers, bringing Na⁺ ions into the sarcolemma. This increase in Na⁺ in the sarcolemma reduces the Na⁺ gradient exploited by sodium-calcium exchanger (NCX) and stops them from working effectively. Ca²⁺ ions accumulate inside the sarcolemma as a result and are uptaken by sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) pumps. Calcium induced calcium release (CICR) from the sarcoplasmic reticulum is increased upon stimulation of the cardiac myocyte by an action potential. This leads to an increase in the force of contraction of the cardiac muscle to try and increase stroke volume and cardiac output to maintain tissue perfusion.

On the other hand, it has been proposed that the Anrep effect may be a spurious effect resulting from the recovery of the myocardium from a transient ischemia arising from the abrupt increase in blood pressure.[3]