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| Image = Left bundle branch block ECG characteristics.png| | | Image = Left bundle branch block ECG characteristics.png| |
| Caption = ECG characteristics of a typical [[LBBB]] showing wide [[QRS]] complexes with abnormal morphology in leads V1 and V6 | | | Caption = ECG characteristics of a typical [[LBBB]] showing wide [[QRS]] complexes with abnormal morphology in leads V1 and V6 | |
| DiseasesDB = 7352 |
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| ICD10 = {{ICD10|I|44|7|i|30}} |
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| ICD9 = |
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| ICDO = |
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| OMIM = |
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| MedlinePlus = |
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| }} | | }} |
| {{SI}} | | {{Left bundle branch block}} |
| {{CMG}}; '''Associate Editor(s)-In-Chief:''' {{CZ}}
| | '''For patient information click [[Heart block (patient information)|here]]''' |
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| '''''Synonyms and related keywords:''''' LBBB
| | {{CMG}}; {{AE}} {{CZ}}; {{RT}}; {{AN}} |
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| ==Overview==
| | {{SK}} LBBB |
| '''Left bundle branch block (LBBB)''' is a cardiac conduction abnormality seen on the [[electrocardiogram]] ([[ECG]]) whereby there is an impairment of transmission of the cardiac electrical impulse along the fibers of the left main bundle branch, or both the left anterior fascicle and left posterior fascicle. This conduction disturbance is characterized by wide (greater than or equal to 0.12 seconds) [[QRS complexes]]. In this condition, activation of the [[left ventricle]] is delayed, which results in the left ventricle contracting later than the [[right ventricle]].
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| ==Classification== | | == [[Left bundle branch block overview|Overview]] == |
| ===New Left Bundle Branch Block===
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| New LBBB is defined as the presence of a new left bundle branch block and:<ref>Shvilkin A, Bojovic B, Vajdic B, Gussak I, Ho KK, Zimetbaum P, Josephson ME. Vectorcardiographic and electrocardiographic criteria to distinguish new and old left bundle branch block. Heart Rhythm 2010;7:1085–1092.</ref> <blockquote>
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| # A prior ECG with normal [[QRS]] duration (<110 ms)12 within 24 hours before the LBBB tracing without [[T-wave]] abnormalities.
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| # Acute-onset illness with LBBB on the admission tracing resolving within 24 hours without [[T-wave]] abnormalities on the subsequent narrow [[QRS]] tracings (to exclude LBBB lasting more than 24 hours) in patients with no history of LBBB.
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| </blockquote>
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| ===Old Left Bundle Branch Block=== | | == [[Left bundle branch block historical perspective|Historical Perspective]] == |
| An old LBBB is defined as an<ref>Shvilkin A, Bojovic B, Vajdic B, Gussak I, Ho KK, Zimetbaum P, Josephson ME. Vectorcardiographic and electrocardiographic criteria to distinguish new and old left bundle branch block. Heart Rhythm 2010;7:1085–1092.</ref> LBBB that has existed for more than 24 hours (by prior tracings or reports in the electronic medical record).
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| ===Left Bundle Branch Block of Unknown Duration=== | | == [[Left bundle branch block classification|Classification]] == |
| The LBBB duration is unknown on tracings obtained within the first 24 hours of admission in which there is not any prior EKG information.<ref>Shvilkin A, Bojovic B, Vajdic B, Gussak I, Ho KK, Zimetbaum P, Josephson ME. Vectorcardiographic and electrocardiographic criteria to distinguish new and old left bundle branch block. Heart Rhythm 2010;7:1085–1092.</ref>
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| ==Causes of LBBB== | | == [[Left bundle branch block pathophysiology|Pathophysiology]] == |
| * [[Aortic insufficiency]]
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| * [[Aortic stenosis]]
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| * [[Aortic valve replacement]]
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| * [[Cardiomyopathy]]
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| :*[[Ischemic cardiomyopathy]]
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| :*[[Alcoholic cardiomyopathy]]
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| :*[[Hypertrophic cardiomyopathy]]
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| :*[[Restrictive cardiomyopathy]]
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| :*[[Hypertensive cardiomyopathy]]
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| :*[[Postpartum cardiomyopathy]]
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| * [[Chagas disease]]
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| * [[coronary heart disease|Coronary Artery Disease]]
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| * [[Dilated cardiomyopathy]]
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| * [[Endocarditis]]
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| * [[Hemochromatosis]]
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| * [[Hypertension]]
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| * [[Hypertrophic obstructive cardiomyopathy]] ([[HOCM]])
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| * [[Ischemic heart disease]]
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| * [[Left ventricular hypertrophy]]
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| * [[Left ventricular outflow tract]] surgery
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| * [[Lyme disease]] <ref>http://onlinelibrary.wiley.com/doi/10.1111/j.1540-8159.1990.tb04009.x/abstract</ref>
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| * [[Myocardial infarction]]
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| * [[Myocardial ischemia]]
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| * [[Myocarditis]]
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| * Primary disease of the cardiac electrical conduction system
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| * Progressive conduction system disease
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| * [[Rheumatic fever]] with [[aortic valve]] involvement
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| * [[Sarcoidosis]]
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| * [[Scleroderma]]
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| * [[Septal myomectomy]]
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| ==Differentiating LBBB from other Disorders== | | == [[Left bundle branch block causes|Causes]] == |
| LBBB must be differentiated from:
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| *[[Left anterior fascicular block]] ([[LAFB]]) where there is block of only the anterior fascicle
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| *[[Left posterior fascicular block]] ([[LPFB]]) where there is block of only the posterior fascicle
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| *[[Left ventricular hypertrophy]] which also causes tall [[QRS complexes]]
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| ==Diagnosis== | | == [[Left bundle branch block differential diagnosis|Differentiating Left Bundle Branch Block from other Diseases]] == |
| ===Electrocardiographic Criteria===
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| The criteria to diagnose a [[left bundle branch block]] on an [[electrocardiogram]] includes the following:
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| * The heart rhythm must be supraventricular in origin. A [[wide QRS complex]] that is not preceded by [[P waves]] would not qualify.
| | == [[Left bundle branch block epidemiology and demographics|Epidemiology and Demographics]] == |
| * The [[QRS]] duration must be greater than or equal to 120 milliseconds.
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| * There should be a QS or rS complex in lead V1.
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| * There should be a monophasic [[R wave]] in leads I and V6.
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| The [[T wave]] deflection should be opposite of the terminal deflection of the [[QRS]] complex. This lack of concordance in direction is known as appropriate [[T wave]] discordance, and it is expected in patients with a left bundle branch block. A concordant [[T wave]] may suggest the presence of either [[ischemia]] or [[myocardial infarction]].
| | == [[Left bundle branch block natural history, complications and prognosis|Natural History, Complications and Prognosis]] == |
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| | == Diagnosis == |
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| The EKG below shows a case of left bundle branch block depicting an RsR' pattern (M pattern) in lead V6, and a [[wide QRS complex]] in both leads V1 and V6.
| | [[Left bundle branch block history and symptoms|History and Symptoms]] | [[Left bundle branch block physical examination|Physical Examination]] | [[Left bundle branch block laboratory findings|Laboratory Findings]] | [[Left bundle branch block electrocardiogram|Electrocardiogram]] | [[Left bundle branch block EKG examples|EKG Examples]] | [[Left bundle branch block chest x ray|Chest X Ray]] | [[Left bundle branch block echocardiography|Echocardiography]] | [[Left bundle branch block other imaging findings|Other Imaging Findings]] | [[Left bundle branch block other diagnostic studies|Other Diagnostic Studies]] |
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| [[File:LBBBmain.png|center|350px]]
| | == Treatment == |
| Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:LBBB.png
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| === EKG Examples ===
| | [[Left bundle branch block management strategy|Management Strategy]] | [[Left bundle branch block surgery|Surgery]] | [[Left bundle branch block primary prevention|Primary Prevention]] | [[Left bundle branch block secondary prevention|Secondary Prevention]] | [[Left bundle branch block cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Left bundle branch block future or investigational therapies|Future or Investigational Therapies]] |
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| The EKG below shows an RsR' pattern (M pattern) in leads [[Electrocardiogram#Precordial|V4]], [[Electrocardiogram#Precordial|V5]], and [[Electrocardiogram#Precordial|V6]] suggesting a left bundle branch block. Also seen are [[wide QRS complexes]] throughout the [[precordium]], and [[ST segment depression]] in leads [[Electrocardiogram#Limb|II]], [[Electrocardiogram#Precordial|V5]], and [[Electrocardiogram#Precordial|V6]].
| | ==Case Studies== |
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| [[File:Left bundle branch block.jpg|center|500px]] | | [[Left bundle branch block case study one|Case #1]] |
| Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:E23.jpg
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| The EKG below shows a [[QRS axis and voltage#Left Axis Deviation (-30 to -90)|left axis deviation]] with an RsR' pattern (M pattern) in all limb leads (leads [[Electrocardiogram#Limb|I]], [[Electrocardiogram#Limb|II]], [[Electrocardiogram#Limb|III]], [[Electrocardiogram#Augmented limb|aVR]], [[Electrocardiogram#Augmented limb|aVL]], and [[Electrocardiogram#Augmented limb|aVF]]) and in lead [[Electrocardiogram#Precordial|V6]], depicting a left bundle branch block. [[Tachycardia]] is also present with a rate of more than 100 beats per minute.
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| [[File:LBBB01.png|center|500px]]
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| Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:12leadLBTB.png
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| The EKG below shows a [[QRS axis and voltage#Left Axis Deviation (-30 to -90)|left axis deviation]] with an RsR' pattern (M pattern) throughout the [[precordium]], depicting a left bundle branch block. The EKG also shows [[wide QRS complexes]] and a [[prolonged PR interval]].
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| [[File:LBBB02.jpg|center|500px]]
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| Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:12leadLBTB002.jpg
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| The EKG below shows an RsR' pattern (M pattern)in leads [[Electrocardiogram#Precordial|V5]], [[Electrocardiogram#Precordial|V6]], and [[Electrocardiogram#Augmented limb|aVL]] depicting a left bundle branch block. There is also notching of the [[QRS complex]] in lead [[Electrocardiogram#Limb|I]] and [[ST segment elevation]] seen in leads [[Electrocardiogram#Precordial|V1]], [[Electrocardiogram#Precordial|V2]], [[Electrocardiogram#Precordial|V3]], [[Electrocardiogram#Precordial|V4]], and [[Electrocardiogram#Augmented limb|aVR]].
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| [[File:LBBB04.jpg|center|500px]]
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| The EKG below shows an RsR' pattern (M pattern) in leads [[Electrocardiogram#Limb|II]], [[Electrocardiogram#Augmented limb|aVL]], and [[Electrocardiogram#Augmented limb|aVF]] depicting a left bundle branch block. There is also [[ST segment elevation]] in leads [[Electrocardiogram#Precordial|V1]], [[Electrocardiogram#Precordial|V2]], and [[Electrocardiogram#Augmented limb|aVR]]. There is [[wide QRS complexes|widening of the QRS complexes]] throughout the [[Electrocardiogram#Precordial|precordial leads]].
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| [[File:LBBB06.jpg|center|500px]]
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| The EKG below shows an RsR' pattern (M pattern) in leads [[Electrocardiogram#Limbs|I]], [[Electrocardiogram#Limb|II]], [[Electrocardiogram#Augmented limb|aVL]], and [[Electrocardiogram#Precordial|V4]] depicting a left bundle branch block. The EKG also shows [[QRS axis and voltage#Left Axis Deviation (-30 to -90)|left axis deviation]] with [[left ventricular hypertrophy]], and [[ST segment elevation|ST segment elevations]] in [[Electrocardiogram#Precordial|V1]], [[Electrocardiogram#Precordial|V2]], and [[Electrocardiogram#Precordial|V3]] as well as an [[ST segment depression]] in [[Electrocardiogram#Precordial|V6]]. There is [[wide QRS complexes|widening of the QRS complexes]] throughout the [[Electrocardiogram#Precordial|precordial leads]].
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| [[File:LBBB07.jpg|center|500px]]
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| The EKG below shows an RsR' pattern (M pattern) in leads [[Electrocardiogram#Precordial|V1]], [[Electrocardiogram#Precordial|V4]], [[Electrocardiogram#Precordial|V5]], and [[Electrocardiogram#Augmented limb|aVL]] depicting a left bundle branch block. The EKG also shows [[ST depression]] with [[T wave inversion]] in lead [[Electrocardiogram#Precordial|V6]] indicating a left ventricular strain pattern. [[Wide QRS complexes]] are seen throughout the EKG. The EKG also shows evidence of [[left ventricular hypertrophy]].
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| [[File:LBBB08.jpg|center|500px]]
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| The EKG below shows an RsR' pattern (M pattern) in leads [[Electrocardiogram#Limb|III]], [[Electrocardiogram#Augmented limb|aVL]], [[Electrocardiogram#Augmented limb|aVF]], and notching of the [[QRS complex]] in [[Electrocardiogram#Precordial|V5]] depicting a left bundle branch block. [[Wide QRS complexes]] are seen throughout the EKG.
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| [[File:LBBB09.jpg|center|500px]]
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| The EKG below shows an [[irregular rhythm]] with an RsR' pattern (M pattern) in leads [[Electrocardiogram#Limb|II]], [[Electrocardiogram#Precordial|V5]], and [[Electrocardiogram#Precordial|V6]]. [[Q waves]] are seen in leads [[Electrocardiogram#Limb|I]], [[Electrocardiogram#Augmented limb|aVL]], [[Electrocardiogram#Precordial|V5]], and [[Electrocardiogram#Precordial|V6]]. There is evidence of [[left ventricular hypertrophy]] and [[QRS axis and voltage#Left Axis Deviation (-30 to -90)|left axis deviation]].
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| [[File:LBBB with Lateral Q waves.CMG.jpg|center|500px]]
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| The EKG below shows a left bundle branch block.
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| [[File:LBBB.CMG.jpg|center|500px]]
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| The EKG below shows an RsR' pattern (M pattern) in leads [[Electrocardiogram#Precordial|V4]] and [[Electrocardiogram#Precordial|V5]] depicting a left bundle branch block. The EKG also shows [[sinus rhythm]], [[prolonged PR interval]] (greater than 200ms), and [[wide QRS complexes]] (> 120ms). The loss of the septal [[Q waves]] and the tall broad [[R waves]] in leads [[Electrocardiogram#Limb|I]], [[Electrocardiogram#Augmented limb|aVL]], and [[Electrocardiogram#Precordial|V6]] are diagnostic of a left bundle branch block.
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| [[File:LBBB12.jpg|center|500px]]
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| Copyleft image obtained courtesy of ECGpedia, http://en.ecgpedia.org/wiki/File:E203.jpg
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| == Reading Ischemia In The Presence Of LBBB ==
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| [[LBBB]] can simulate an [[MI]] due to the associated secondary ST changes and pseudoinfarction [[q wave]]s that it is associated with. It can mask the [[EKG]] changes of an [[MI]].
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| ===Sgarbossa Criteria===
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| An EKG scoring system was developed, and the independent criteria were assessed on patients from the GUSTO-1 trial. These patients were scored from 0-5 for the presence of LBBB in the context of an [[acute myocardial infarction]].<ref>{{cite journal |author=Sgarbossa EB, Pinski SL, Barbagelata A, Underwood DA, Gates KB, Topol EJ, Califf RM, Wagner GS |title=Electrocardiographic diagnosis of evolving acute myocardial infarction in the presence of left bundle-branch block. GUSTO-1 (Global Utilization of Streptokinase and Tissue Plasminogen Activator for Occluded Coronary Arteries) Investigators |journal=[[N. Engl. J. Med.]] |volume=334 |issue=8 |pages=481–7 |year=1996 |month=February |pmid=8559200 |doi= |url=http://content.nejm.org/cgi/pmidlookup?view=short&pmid=8559200&promo=ONFLNS19}}</ref>
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| <table width="30%" height="100px" border="1">
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| <tr>
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| <td>Criteria </td>
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| <td>Score</td>
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| </tr>
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| <tr>
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| <td> 1.[[ST-segment elevation]] ≥ 1 mm and concordant with [[QRS complex]] </td>
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| <td> 5 </td>
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| </tr>
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| <tr>
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| <td> 2.[[ST-segment depression]] ≥ 1 mm in lead V1,V2 or V3 </td>
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| <td> 3 </td>
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| </tr>
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| <tr>
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| <td> 3.[[ST-segment elevation]] ≥ 5 mm and discordant with [[QRS complex]] </td>
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| <td> 2 </td>
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| </tr>
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| </table>
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| == Pseudoinfarct Patterns: Simulation of an Anterior MI ==
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| # LBBB can cause a [[poor R wave progression]]. In the presence of LBBB, there is often a decrease in the amplitude of [[R wave|R waves]] to the mid [[precordium]] in the absence of a septal infarct.
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| # QS complexes are often seen in the right precordial leads in uncomplicated [[LBBB]], and they may even extend as far out as V5 or V6.
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| # Non infarctional [[Q waves]] may be seen in aVL.
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| # The electrical basis for the appearance of [[q waves]] is that [[LBBB]] causes a loss of the normal septal [[R waves]] in the right precordial leads. The septum is no longer being depolarized from left to right as it normally does because of the delay in conduction down the left bundle. Therefore, there is a loss of the early [[R wave]].
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| # There can occasionally be Rs complexes in V1. These unanticipated initial positive forces are due to early RV depolarization and may actually mask the [[q waves]] (i.e. loss of initial septal forces) that accompany an [[acute MI|anteroseptal MI]].
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| == Simulation of an Inferior [[MI]] ==
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| # Noninfarctional QS complexes can be seen in leads II, III, and aVF in [[LBBB]].
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| # There are a number of autopsy cases were there are QS waves inferiorly without evidence of an [[MI]].
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| # There are several reported cases of intermittent [[LBBB]] in which the inferior QS waves were present only in the aberrantly conducted beats.
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| # Conversely, [[LBBB]] may mask the development of Q waves in an [[MI]].
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| == Secondary [[ST segment]] and [[T Wave]] Changes ==
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| # Primary [[ST segment]] and [[T wave]] changes are repolarization changes that are seen with ischemia or electrolyte imbalance. They reflect actual changes in the myocardial action potentials.
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| # Secondary [[ST segment]] and [[T wave]] changes occur when the sequence of ventricular activation is altered without any disturbance in the electrical properties of the myocardial cells such as is seen in [[LBBB]].
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| # As a result of secondary [[ST segment]] and [[T wave]] wave changes, the [[QRS]] and the [[T wave]] vectors are oriented in opposite directions which is known as discordance of the [[QRS]] and [[T wave]] vectors.
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| # Thus, the [[QRS]] is often predominantly negative in the right precordial leads while the [[T wave]] is oriented positively. In those leads where there is a tall positive R wave there is a negative [[T wave]].
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| # These secondary [[ST segment]] and [[T wave]] changes often mimic infarction, and furthermore they may mask the [[ST segment]] and [[T wave]] changes of an MI.
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| # Sometimes primary [[ST segment]] and [[T wave]] changes will be superimposed on the [[LBBB]] pattern and the following suggests the diagnosis of ischemia or infarction:
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| #* [[ST segment]] elevation in leads with a predominant R wave. In uncomplicated [[LBBB]], the [[ST segment]] is isoelectric or depressed.
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| #* T wave inversions in the right to midprecordial leads or in other leads with a predominantly negative [[QRS]]. In other words there is an absence of discordance, and there is the presence of concordance.
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| #* Morphology: In leads with a predominant R wave, the [[ST segment]] begins to slope downwards and blends into the [[T wave]]. The ascending limb of the [[T wave]] ascends back to the baseline at a more acute angle.
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| #* The ischemic [[T waves]] have a more symmetric appearance and a slightly upwardly bowed [[ST segment]].
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| #* [[ST segment]] and [[T wave]] elevations simulating acute infarction: The [[ST segment]] can be markedly elevated (up to 10 mm or more at the J point ) in leads with a QS or rS segment in uncomplicated [[LBBB]]. In addition, there can be a loss of R wave progression.
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| #* T wave inversions in intermittent [[LBBB]]: May develop deep [[T wave]] inversions in the right to midprecordial leads of normally conducted beats in the absence of CAD. These [[T wave]] inversions are deepest in leads V1 to V4 with a symmetric or coved appearance.
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| == Etiology of Q Waves ==
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| # As described earlier, in [[LBBB]] there is a loss of depolarization from left to right, which produced an initial r wave in the right precordial leads.
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| # Now there is depolarization from right to left. Consequently the initial r wave is lost, and the non infarctional QS complexes may appear in the precordial leads.
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| # The reversal of septal activation results in RS complexes in the left precordial leads.
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| == Can You Read a Left Ventricular Free Wall Infarction In the Presence of a [[LBBB]]? ==
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| # No. This pattern of infarction results in abnormal q waves in the midprecordial to lateral precordial leads.
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| # In [[LBBB]] the initial septal depolarization forces are directed from right to left. These leftward septal forces will produce an initial R wave in the midprecordial to the lateral precordial leads, masking the loss of potential q waves produced by the infarction.
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| # Therefore left ventricular free wall infarction by itself will not produce diagnostic q waves in the presence of a [[LBBB]].
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| # Poor R wave progression is seen in uncomplicated [[LBBB]].
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| == Can You Read a Septal Infarction in the Presence of [[LBBB]]? ==
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| # Yes. Again the septal forces are directed to the left in [[LBBB]].
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| # If enough of the septum is infarcted to eliminate these initial leftward septal forces, abnormal QR, [[QRS]], or qrs types of complexes may appear in the midprecordial to lateral precordial leads.
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| # These initial q waves may reflect posterior and superior forces from the spared basal portion of the septum.
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| # Small q waves of 0.03 sec or less may be seen in leads I, V5 to V6 in uncomplicated [[LBBB]].
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| # The presence of q waves laterally is an example of false localization. <ref>Myocardial Infarction, Electrocardiographic Differential Dx, Ary L. Goldberger, 3rd ed., Mosby Co., St. Louis, 1984, p.85 93.
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| </ref>
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| ===Physical Examination===
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| ====Heart====
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| Paradoxical split of the [[second heart sound]]
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| ==Treatment ==
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| Treatment is directed at the underlying cause of left bundle branch block, such as [[ST elevation myocardial infarction]]. Patients with [[syncope]] and LBBB may have a rhythm disturbance that requires a pacemaker. Given the dysynchrony that occurs with left ventricular contractility, [[cardiac resynchronization therapy]] in [[heart failure]] patients may be of benefit.
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| ==Related Chapters== | | ==Related Chapters== |
| * [[Bundle branch block]] | | * [[Bundle branch block]] |
| * [[Right bundle branch block]] | | * [[Right bundle branch block]] |
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| == References ==
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| {{Reflist|2}}
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| [[Category:Cardiology]] | | [[Category:Cardiology]] |
| [[Category:Electrophysiology]] | | [[Category:Electrophysiology]] |
| | [[Category:Arrhythmia]] |
| [[Category:Emergency medicine]] | | [[Category:Emergency medicine]] |
| [[Category:Intensive care medicine]] | | [[Category:Intensive care medicine]] |
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| [[de:Linksschenkelblock]]
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| [[pt:Bloqueio do ramo esquerdo do feixe de His]] | | [[pt:Bloqueio do ramo esquerdo do feixe de His]] |
| [[fr:Bloc de branche]] | | [[fr:Bloc de branche]] |
