An accessory pathway is an additional electrical connection between two parts of the heart.[1] These pathways can lead to abnormal heart rhythms or arrhythmias associated with symptoms of palpitations. Some pathways may activate a region of ventricular muscle earlier than would normally occur, referred to as pre-excitation, and this may be seen on an electrocardiogram. The combination of an accessory pathway that causes pre-excitation with arrhythmias is known as Wolff-Parkinson-White syndrome.[2]
Accessory pathways are often diagnosed using an electrocardiogram, but characterisation and location of the pathway may require an electrophysiological study. Accessory pathways may not require any treatment, but those causing symptoms may be treated with medication including calcium channel antagonists, beta blockers or flecainide.[3] Alternatively, the electrical conduction through an accessory pathways can be abolished using catheter ablation, potentially offering a permanent cure.[3]
The most common sites for accessory pathways are connections between muscle tissue in the atria and the ventricles (atrio-ventricular pathways), bypassing the atrioventricular node. Rarer sites include connections between atrial muscle and the conducting tissue within the ventricles (atrio-fascicular pathways), between the atrioventricular node and the muscle tissue of the ventricle (nodo-ventricular pathways), and between the conducting tissue of the ventricle and the ventricular muscle (fasciculo-ventricular pathways). These rarer accessory pathways are sometimes collectively referred to as Mahaim pathways or Mahaim fibres.[4]
ECGs during sinus rhythm and AVRT from a 9-year-old girl with Ebstein's anomaly and a Mahaim accessory pathway.
Mahaim pathways are typically seen on the right side of the heart, with their ventricular connection lying within or close to the right bundle branch.[4] The fibres often conduct slowly and in one direction only - from the atria to the ventricles (antegrade conduction); not from the ventricles to the atria (retrograde conduction). Unlike most atrio-ventricular accessory pathways which conduct electrical impulses at a relatively fixed speed, conduction through a Mahaim pathway varies according to how rapidly it is stimulated. More frequent stimulation leads to slower conduction, known as decremental conduction.[4] If conduction to the ventricles occurs solely through the pathway (maximal pre-excitation), as occurs during arrhythmias like antidromic atrioventricular re-entrant tachycardia, the ECG appearance is of QRS complexes with a left bundle branch block morphology which can be mistaken for ventricular tachycardia. However, due to their slow decremental conduction, during sinus rhythm the 12-lead ECG will often show little pre-excitation.[4]
Referencesedit
^Josephson, Mark E. (2015-08-10). Josephson's clinical cardiac electrophysiology : techniques and interpretations. Preceded by: Josephson, Mark E. (Fifth ed.). Baltimore, MD. ISBN9781496326614. OCLC 938434294.{{cite book}}: CS1 maint: location missing publisher (link)
accessory, pathway, accessory, pathway, additional, electrical, connection, between, parts, heart, these, pathways, lead, abnormal, heart, rhythms, arrhythmias, associated, with, symptoms, palpitations, some, pathways, activate, region, ventricular, muscle, ea. An accessory pathway is an additional electrical connection between two parts of the heart 1 These pathways can lead to abnormal heart rhythms or arrhythmias associated with symptoms of palpitations Some pathways may activate a region of ventricular muscle earlier than would normally occur referred to as pre excitation and this may be seen on an electrocardiogram The combination of an accessory pathway that causes pre excitation with arrhythmias is known as Wolff Parkinson White syndrome 2 Accessory pathways are often diagnosed using an electrocardiogram but characterisation and location of the pathway may require an electrophysiological study Accessory pathways may not require any treatment but those causing symptoms may be treated with medication including calcium channel antagonists beta blockers or flecainide 3 Alternatively the electrical conduction through an accessory pathways can be abolished using catheter ablation potentially offering a permanent cure 3 Contents 1 Mahaim pathways 2 ReferencesMahaim pathways editThe most common sites for accessory pathways are connections between muscle tissue in the atria and the ventricles atrio ventricular pathways bypassing the atrioventricular node Rarer sites include connections between atrial muscle and the conducting tissue within the ventricles atrio fascicular pathways between the atrioventricular node and the muscle tissue of the ventricle nodo ventricular pathways and between the conducting tissue of the ventricle and the ventricular muscle fasciculo ventricular pathways These rarer accessory pathways are sometimes collectively referred to as Mahaim pathways or Mahaim fibres 4 nbsp ECGs during sinus rhythm and AVRT from a 9 year old girl with Ebstein s anomaly and a Mahaim accessory pathway Mahaim pathways are typically seen on the right side of the heart with their ventricular connection lying within or close to the right bundle branch 4 The fibres often conduct slowly and in one direction only from the atria to the ventricles antegrade conduction not from the ventricles to the atria retrograde conduction Unlike most atrio ventricular accessory pathways which conduct electrical impulses at a relatively fixed speed conduction through a Mahaim pathway varies according to how rapidly it is stimulated More frequent stimulation leads to slower conduction known as decremental conduction 4 If conduction to the ventricles occurs solely through the pathway maximal pre excitation as occurs during arrhythmias like antidromic atrioventricular re entrant tachycardia the ECG appearance is of QRS complexes with a left bundle branch block morphology which can be mistaken for ventricular tachycardia However due to their slow decremental conduction during sinus rhythm the 12 lead ECG will often show little pre excitation 4 References edit Josephson Mark E 2015 08 10 Josephson s clinical cardiac electrophysiology techniques and interpretations Preceded by Josephson Mark E Fifth ed Baltimore MD ISBN 9781496326614 OCLC 938434294 a href Template Cite book html title Template Cite book cite book a CS1 maint location missing publisher link Bhatia Atul Sra Jasbir Akhtar Masood March 2016 Preexcitation Syndromes Current Problems in Cardiology 41 3 99 137 doi 10 1016 j cpcardiol 2015 11 002 ISSN 1535 6280 PMID 26897561 a b Katritsis Demosthenes G Boriani Giuseppe Cosio Francisco G Hindricks Gerhard Jais Pierre Josephson Mark E Keegan Roberto Kim Young Hoon Knight Bradley P Kuck Karl Heinz Lane Deirdre A 2017 03 01 European Heart Rhythm Association EHRA consensus document on the management of supraventricular arrhythmias endorsed by Heart Rhythm Society HRS Asia Pacific Heart Rhythm Society APHRS and Sociedad Latinoamericana de Estimulacion Cardiaca y Electrofisiologia SOLAECE Europace 19 3 465 511 doi 10 1093 europace euw301 ISSN 1532 2092 PMID 27856540 a b c d Katritsis Demosthenes G Wellens Hein J Josephson Mark E April 2017 Mahaim Accessory Pathways Arrhythmia amp Electrophysiology Review 6 1 29 32 doi 10 15420 aer 2016 35 1 ISSN 2050 3369 PMC 5430943 PMID 28507744 Retrieved from https en wikipedia org w index php title Accessory pathway amp oldid 1054210528, wikipedia, wiki, book, books, library,
