Anrep effect

The Anrep effect is an autoregulation method in which myocardial contractility increases with afterload.[1] It was experimentally determined that increasing afterload caused a proportional linear increase in ventricular inotropy.[2] This effect is found in denervated heart preparations, such as the Starling Preparation, and represents an intrinsic autoregulation mechanism.

Physiology

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.[3] Ca2+ ions accumulate inside the sarcolemma as a result,[3] and are taken up by sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) pumps. Calcium induced calcium release (CICR) from the sarcoplasmic reticulum is thus increased upon the next activation of the cardiac myocyte. This leads to an increase in the force of contraction of the cardiac muscle, which partly counterbalances the effects of afterload by increasing 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.[4]

Function

The Anrep effect allows the heart to compensate for the increased end-systolic volume and the decreased stroke volume that occurs when aortic blood pressure (i.e. afterload) 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.

History

The Anrep effect is named after Russian physiologist Gleb von Anrep, who described it in 1912.[2][5] Anrep clamped the ascending aorta in dogs, and showed that the heart dilated.[2][3]

References
  1. Kass, D. A. (2017-01-01), Jefferies, John Lynn; Blaxall, Burns C.; Robbins, Jeffrey; Towbin, Jeffrey A. (eds.), "Chapter 1 - Ventricular Systolic Function", Cardioskeletal Myopathies in Children and Young Adults, Boston: Academic Press, pp. 3–19, doi:10.1016/b978-0-12-800040-3.00001-7, ISBN 978-0-12-800040-3, retrieved 2020-11-15
  2. Von Anrep, G. (1912). "On the part played by the suprarenals in the normal vascular reactions of the body". The Journal of Physiology. 45 (5): 307–317. doi:10.1113/jphysiol.1912.sp001553. PMC 1512890. PMID 16993158.
  3. Cingolani, Horacio E.; Pérez, Néstor G.; Cingolani, Oscar H.; Ennis, Irene L. (2012-11-16). "The Anrep effect: 100 years later". American Journal of Physiology. Heart and Circulatory Physiology. 304 (2): H175–H182. doi:10.1152/ajpheart.00508.2012. ISSN 0363-6135. PMID 23161880.
  4. Monroe, R. G. (1972). "The Anrep Effect Reconsidered". The Journal of Clinical Investigation. 51 (10): 2573–2583. doi:10.1172/JCI107074. PMC 332955. PMID 5056656.
  5. Gaddum, J. H. (1956). "Gleb Anrep. 1891-1955". Biographical Memoirs of Fellows of the Royal Society. 2: 19–42. doi:10.1098/rsbm.1956.0002. JSTOR 769473.
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