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Is the Conduction system Involved in Idiopathic Ventricular Arrhythmias Arising from The Region of Aorto-Mitral Continuity?
MedLine Citation:
PMID:  25431284     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Outflow tract ventricular tachycardias (OTVT) are the commonest type of idiopathic VT.(1) As the name suggests, these arrhythmias originate in the OT region of the right and left ventricles (RV and LV, respectively), the most common sites being the superior septal RVOT and the aortic cusp region.(2,3) Other less common sites of origin include the superior LV septum, LV summit, region of aorto-mitral, continuity (AMC) and superior mitral annulus (MA).(4) Delayed after depolarization (DAD) mediated triggered activity has been implicated as the mechanism underlying OTVT.(5) This has been validated through the pioneering studies by Lerman et al., who have shown intracellular calcium release underlying the triggered activity. The release of calcium is facilitated by cyclic adenosine monophosphate the formation of which is controlled through the interplay of stimulatory and inhibitory G-proteins.(6) Alteration of these proteins by pharmacologic interventions can enhance or diminish triggered activity. Thus, catecholaminergic agents enhance triggered activity, whereas adenosine and acetylcholine suppress it.(1,5,6) It remains unclear, however, why the OT region is the source of triggered activity. One possible explanation is that since developmentally the OT region originates from a separate cell line (the second heart field), these cells may have different electrophysiologic properties and so can support triggered activity.(7) Another possible explanation is that the inherent tissue anisotropy in this region (due to interposition of connective tissue from adjoining valve apparatus) may promote arrhythmogenesis, similar to observations made in the pulmonary veins (8) . Finally, remnants of the atrio-ventricular (AV) conduction system have also been demonstrated in some locations in the OT, and these have been implicated as a potential source of abnormal automaticity or triggered activity from this region.(9) Hai et al in this issue of the Journal, provide some interesting clinical observation in support of the latter hypothesis.(10) This article is protected by copyright. All rights reserved.
Authors:
Sanjay Dixit; Amit Mehrotra
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2014-11-28
Journal Detail:
Title:  Journal of cardiovascular electrophysiology     Volume:  -     ISSN:  1540-8167     ISO Abbreviation:  J. Cardiovasc. Electrophysiol.     Publication Date:  2014 Nov 
Date Detail:
Created Date:  2014-11-28     Completed Date:  -     Revised Date:  2014-11-29    
Medline Journal Info:
Nlm Unique ID:  9010756     Medline TA:  J Cardiovasc Electrophysiol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
This article is protected by copyright. All rights reserved.
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