Atrioventricular node

Atrioventricular node

Isolated heart conduction system showing atrioventricular node

Conduction system of the Heart (AV node labeled 2 on image)
Details
Artery Atrioventricular nodal branch
Identifiers
Latin Nodus atrioventricularis
TA A12.1.06.004
FMA 9478

Anatomical terminology

The atrioventricular (AV) node is a part of the electrical conduction system of the heart that coordinates the top of the heart. It electrically connects atrial and ventricular chambers.[1] The AV node is an area of specialized tissue between the atria and the ventricles of the heart, specifically in the posteroinferior region of the interatrial septum near the opening of the coronary sinus, which conducts the normal electrical impulse from the atria to the ventricles. The AV node is quite compact (~1 x 3 x 5 mm).[2] It is located at the center of Koch's triangle—a triangle enclosed by the septal leaflet of the tricuspid valve, the coronary sinus, and the membraneous part of the interatrial septum.[3]

Structure

The AV node receives two inputs from the atria: posteriorly, via the crista terminalis, and anteriorly, via the interatrial septum.[4]

Blood supply

The blood supply of the AV node is via the AV nodal artery. The origin of this artery is most commonly (about 90% of hearts) a branch of the right coronary artery, with the remainder originating from the left circumflex artery.[5][6][7] This is associated with the dominance of the coronary artery circulation. In right-dominant individuals the blood supply is from the right coronary artery while in left dominant individuals it originates from the left circumflex artery.

Development

BMP (Bone morphogenetic protein) cell signaling plays a key role in diverse aspects of cardiac differentiation and morphogenesis. (BMPs) are multifunctional signaling molecules critical for the development of AV node. BMP influences AV node development through Alk3 receptor (Activin receptor-like kinase 3). Abnormalities seen in BMP and Alk3 are associated with some cardiovascular diseases like Ebstein’s anomaly and AV conduction disease.[8]

Function

Contraction of cardiomyocytes (heart muscle cells) requires depolarization and repolarization of their cell membranes. Movement of ions across cell membranes causes these events. The cardiac conduction system (and AV node part of it) coordinates myocyte mechanical activity. A wave of excitation spreads out from the sinoatrial node through the atria along specialized conduction channels. This activates the AV node.[1] The atrioventricular node delays impulses by approximately 0.12s. This delay in the cardiac pulse is extremely important: It ensures that the atria have ejected their blood into the ventricles first before the ventricles contract.[9]

This also protects the ventricles from excessively fast rate response to atrial arrhythmias (see below).[10]

AV conduction during normal cardiac rhythm occurs through two different pathways:

An important property that is unique to the AV node is decremental conduction,[12] in which the more frequently the node is stimulated the slower it conducts. This is the property of the AV node that prevents rapid conduction to the ventricle in cases of rapid atrial rhythms, such as atrial fibrillation or atrial flutter.

The AV node's normal intrinsic firing rate without stimulation (such as that from the SA node) is 40-60 times/minute.[13] This property is important because loss of the conduction system before the AV node should still result in pacing of the ventricles by the — slower — pacemaking ability of the AV node.

Clinical relevance

See also

This article uses anatomical terminology; for an overview, see Anatomical terminology.

References

  1. 1 2 Gray, Huon H.; Keith D. Dawkins; Iain A. Simpson; John M. Morgan (2002). Lecture Notes on Cardiology. Boston: Blackwell Science. p. 135. ISBN 978-0-86542-864-5.
  2. ↑ Full Size Picture triangle of-Koch.jpg. Retrieved on 2008-12-22
  3. ↑ Harrison's Principles of Internal Medicine, 17e” Section 3: Disorders of Rhythm Archived July 7, 2011, at the Wayback Machine.
  4. ↑ Fuster V, Rydén LE, Asinger RW, et al. (October 2001). "ACC/AHA/ESC guidelines for the management of patients with atrial fibrillation" (PDF). Journal of the American College of Cardiology. 38 (4): 1231–66. doi:10.1016/S0735-1097(01)01587-X. PMID 11583910.
  5. ↑ Van der Hauwaert LG, Stroobandt R, Verhaeghe L (October 1972). "Arterial blood supply of the atrioventricular node and main bundle". British Heart Journal. 34 (10): 1045–51. doi:10.1136/hrt.34.10.1045. PMC 458545Freely accessible. PMID 5086972.
  6. ↑ Pejković, B.; Krajnc, I.; Anderhuber, F.; Kosutić, D. (2008). "Anatomical aspects of the arterial blood supply to the sinoatrial and atrioventricular nodes of the human heart". The Journal of international medical research. 36 (4): 691–698. doi:10.1177/147323000803600410. PMID 18652764.
  7. ↑ Saremi, F.; Abolhoda, A.; Ashikyan, O.; Milliken, J. C.; Narula, J.; Gurudevan, S. V.; Kaushal, K.; Raney, A. (2007). "Arterial Supply to Sinuatrial and Atrioventricular Nodes: Imaging with Multidetector CT". Radiology. 246 (1): 99–107; discussion 108–9. doi:10.1148/radiol.2461070030. PMID 18024438.
  8. ↑ Stroud DM, Gaussin V, Burch JB, et al. (November 2007). "Abnormal Conduction and Morphology in the Atrioventricular Node of Mice With Atrioventricular Canal–Targeted Deletion of Alk3/Bmpr1a Receptor". Circulation. 116 (22): 2535–43. doi:10.1161/CIRCULATIONAHA.107.696583. PMC 2947829Freely accessible. PMID 17998461.
  9. ↑ Campbell, N., & Reece, J. (2002). Biology. 6th ed. San Francisco: Benjamin Cummings
  10. ↑ Gray, Huon H.; Keith D. Dawkins; Iain A. Simpson; John M. Morgan (2002). Lecture Notes on Cardiology. Boston: Blackwell Science. p. 136. ISBN 978-0-86542-864-5.
  11. 1 2 Gray, Huon H.; Keith D. Dawkins; Iain A. Simpson; John M. Morgan (2002). Lecture Notes on Cardiology. Boston: Blackwell Science. p. 157. ISBN 978-0-86542-864-5.
  12. ↑ Patterson E, Scherlag BJ (October 2002). "Decremental conduction in the posterior and anterior AV nodal inputs". Journal of Interventional Cardiac Electrophysiology. 7 (2): 137–48. doi:10.1023/A:1020833604423. PMID 12397223.
  13. ↑ Guyton, Arthur C.; John E. Hall (2006). Textbook of Medical Physiology (11 ed.). Philadelphia: Elsevier Saunders. p. 120. ISBN 0-7216-0240-1.
  14. ↑ Benson DW (October 2004). "Genetics of atrioventricular conduction disease in humans". The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology. 280 (2): 934–9. doi:10.1002/ar.a.20099. PMID 15372490.
  15. ↑ Sharma G, Linden MD, Schultz DS, Inamdar KV (January 2009). "Cystic tumor of the atrioventricular node: an unexpected finding in an explanted heart". Cardiovascular Pathology. 19 (3): e75–8. doi:10.1016/j.carpath.2008.10.011. PMID 19144541.

External links

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