Conduction Blocks and Preexcitation syndromes07

Conduction Blocks and Preexcitation syndromes07 -...

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Unformatted text preview: Conduction System Abnormalities and Preexcitation Syndromes Conduction Abnormalities An obstruction in normal electrical An conduction system 3 types of conduction blocks types – Sinus node block – AV block (PR interval) » 1st degree » 2nd degree – Wenckebach, Mobitz I » 2nd degree – Mobitz II » 3rd degree – Bundle branch block (widened QRS complex) 1 1st Degree AV Block Prolonged delay in Prolonged conduction at the AV node or His bundle Look in lead II and V5 to Look verify – PR interval > 0.20 seconds – QRS for every P wave 2 PR interval ~ 0.26 sec 2nd Degree AV block – Mobitz I Each atrial impulse encounters a Each longer and longer delay in the AV node until one impulse fails to make it through PR interval progressively PR lengthens until one QRS complex is dropped QRS does not always follow a P QRS wave Also called Also Weinckebach 3 2nd Degree AV Block – Mobitz II Caused by a block below the Caused the AV node in which not all atrial impulses reach the ventricles PR interval is normal length PR (0.20 sec) P wave is not always followed wave by a QRS complex NO QRS follows P wave Progressively lengthened PR interval Varying PR interval AV Block, 2:1 4 3rd degree AV Block Also known as AV Also dissociation, there is no communication occurring between the atria and the ventricles. PR interval varies from cycle PR to cycle P wave is not always followed wave by a QRS complex. Atrial (P wave) rate will be Atrial twice that of the ventricles (QRS complex). Notice P waves may be hidden in QRS or T waves Atrial Rate ~ 70 bts/min Ventricular Rate ~ 35 bts/min 5 Bundle Branch Blocks Conduction block in either the right or Conduction left bundle branch Must look at the width of the QRS Must complex usually in the precordial leads Right bundle branch block (RBBB) – Right may be normal or abnormal occurrence Left bundle branch block (LBBB) – Left usually signifies underlying cardiac disease Right Bundle Branch Block QRS complex widened to greater than QRS 0.12 seconds RSR’ pattern in V1 and/or V2 with ST RSR segment depression and T wave inversion Reciprocal changes in V5 and V6 Reciprocal May also be “incomplete” meaning QRS May complex between 0.10 seconds and 0.12 sec in length 6 RBBB RSR’ QRS complexes in most leads are > 0.12 sec www.cardiology.org RBBB 7 Left Bundle Branch Block QRS complex widened to greater than QRS 0.12 seconds Broad or notched R wave with Broad prolonged upstroke in leads V5, V6, I, and avL with ST segment depression and T wave inversion Reciprocal changes in V1 and V2 Reciprocal LAD may also be present LAD LBBB QRS complexes in most leads are > 0.12 sec Notched QRS www.cardiology.org 8 LBBB Hemiblocks Conduction block of just one the the Conduction fascicles in the left ventricular conduction system Left Anterior Hemiblock – Left – Normal or borderline QRS duration – LAD Left posterior Hemiblock Left – Normal or borderline QRS duration – RAD 9 Left Anterior Hemiblock www.cardiology.org LAH 10 Preexcitation Syndromes This means that current is transmitted This faster than it should be from atria to ventricles Due to accessory pathways Due Wolff-Parkinson-White (WPW) Wolff syndrome Lown-Ganong-Levine (LGL) syndrome Lown WPW syndrome PR interval < 0.12 sec PR Wide QRS complexes Wide Presence of delta wave in some Presence leads 11 WPW Delta Wave www.cardiology.org LGL syndrome syndrome PR interval < 0.12 sec PR Normal QRS width Normal No delta wave No May be presence of PSVT or atrial May fibrillation with LGL 12 ...
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This note was uploaded on 01/16/2012 for the course KINE 430 taught by Professor Dr.jenniferblevins-mcnaughton during the Fall '11 term at Tarleton.

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