Atrioventricular block (AV block) is a type of heart block in which the conduction between the atria and ventricles of the heart is impaired. Under normal conditions, the sinoatrial node (SA node) in the atria sets the pace for the heart, and these impulses travel down to the ventricles. In an AV block, this message does not reach the ventricles or is impaired along the way. The ventricles of the heart have their own pacing mechanisms, which can maintain a lowered heart rate in the absence of SA stimulation.
The causes of pathological AV block are varied and include ischaemia, infarction, fibrosis or drugs, and the blocks may be complete or may only impair the signaling between the SA and AV nodes. Certain AV blocks can also be found as normal variants, such as in athletes or children, and are benign. Strong vagal stimulation may also produce AV block. The cholinergic receptor types affected are the muscarinic receptors.
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http://cdn.intechopen.com/pdfs/13776.pdf pacing therapy in infants and children with congenital and acquired complete atrioventricular block: optimal pacing strategies, management, and follow-up. By floris e.a. Udink ten cate and narayanswami sreeram.
http://www.hindawi.com/journals/cric/2014/372936/ nagham saeed jafar, warkaa al shamkhani, sunil roy thottuvelil narayanan, and anil kumar rajappan, “rapidly progressive atrioventricular block in a patient with sarcoidosis,” case reports in cardiology, vol. 2014, article id 372936, 3 pages, 2014. Doi:10.1155/2014/372936
Karande s c, sheth s s, dalvi b v, lahiri k, shah m d. Congenital intermittent atrio-ventricular dissociation in tetralogy of fallot (a case report). J postgrad med [serial online] 1991 [cited 2016 aug 1];37:58-61. Available from: http://www.jpgmonline.com/text.asp?1991/37/1/58/798