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| | __NOTOC__ |
| {{Infobox_Disease | | | {{Infobox_Disease | |
| Name = {{PAGENAME}} | | | Name = {{PAGENAME}} | |
| 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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| eMedicineSubj = ped |
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| eMedicineTopic = 2501 |
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| MeshID = |
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| }} | | }} |
| {{SI}} | | {{Left bundle branch block}} |
| {{WikiDoc Cardiology Network Infobox}}
| | '''For patient information click [[Heart block (patient information)|here]]''' |
| {{WikiDoc Cardiology News}}
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| {{CMG}}
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| __NOTOC__
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| '''Associate Editors-In-Chief:''' {{CZ}}; Atif Mohammad, MD
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| __NOEDITSECTION__
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| {{Editor Join}}
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| '''Synonyms and related keywords:''' LBBB
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| '''Left bundle branch block ([[LBBB]])''' is a cardiac conduction abnormality seen on the [[electrocardiogram]] ([[ECG]]). 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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| ==[[EKG]] diagnosis==
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| The criteria to diagnose a [[left bundle branch block]] on the [[electrocardiogram]]:
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| * The heart rhythm must be supraventricular in origin
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| * The [[QRS]] duration must be = or > 120 ms
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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 should be deflected opposite the terminal deflection of the [[QRS]] complex. This is known as appropriate [[T wave]] discordance with bundle branch block. A concordant [[T wave]] may suggest ischemia or [[myocardial infarction]].
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| ==Causes of [[LBBB]]==
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| Among the causes of [[LBBB]] are:
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| * [[Hypertension]]
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| * Acute [[myocardial infarction]]
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| * Extensive cases of [[coronary heart disease|coronary artery disease]]
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| * Primary disease of the cardiac electrical conduction system
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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 pseudoinfarct q waves that it causes, and furthermore 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 criterion were assessed on patients from the GUSTO-1 trial patients were scored from 0-5 for presence of LBBB in the context of 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>
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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 [[acute MI|Anterior MI]] ==
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| # Can cause poor R wave progression. Often see a decrease in the amplitude of R waves to the midprecordium 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 Reason: [[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 down the left bundle.
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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 QS waves inferiorly 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 and reflect actual changes in the myocardial action potentials.
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| # Secondary [[ST segment]] and [[T wave]] 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 ==
| | {{CMG}}; {{AE}} {{CZ}}; {{RT}}; {{AN}} |
| # 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]]? ==
| | {{SK}} LBBB |
| # 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]]? == | | == [[Left bundle branch block overview|Overview]] == |
| # 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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| ==Treatment == | | == [[Left bundle branch block historical perspective|Historical Perspective]] == |
| * Medical Care: Patients with LBBB require complete cardiac evaluation, and those with LBBB and near-syncope or syncope may require a pacemaker.
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| * Surgical Care: Some patients with LBBB, a markedly prolonged QRS, and congestive heart failure may benefit from a pacemaker, which provides rapid left ventricular contractions.
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| ==Classification== | | == [[Left bundle branch block classification|Classification]] == |
| Some sources distinguish between a "left anterior fascicular block" (LAFB)<ref>{{GPnotebook|x20050921122910832459}}</ref> and a "left posterior fascicular block" (LAPB).<ref>{{GPnotebook|x20050921123129832459}}</ref> This refers to the bifurcation of the left [[bundle branch]].
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| ==EKG Examples== | | == [[Left bundle branch block pathophysiology|Pathophysiology]] == |
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| <div align="center">
| | == [[Left bundle branch block causes|Causes]] == |
| <gallery heights="175" widths="175">
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| Image:12leadLBTB.png|Left Bundle Branch Block
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| Image:12leadLBTB002.jpg|Left Bundle Branch Block
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| </gallery>
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| </div>
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| | == [[Left bundle branch block differential diagnosis|Differentiating Left Bundle Branch Block from other Diseases]] == |
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| <div align="center">
| | == [[Left bundle branch block epidemiology and demographics|Epidemiology and Demographics]] == |
| <gallery heights="175" widths="175">
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| Image:c10.ht10.jpg|Left Bundle Branch Block <small> [http://www.ganseman.com/ecgbibnl.htm#_top000 Image courtesy of Dr Jose Ganseman]</small>
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| Image:c11.ht11.jpg|Left Bundle Branch Block <small> [http://www.ganseman.com/ecgbibnl.htm#_top000 Image courtesy of Dr Jose Ganseman]</small>
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| </gallery>
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| </div>
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| | == [[Left bundle branch block natural history, complications and prognosis|Natural History, Complications and Prognosis]] == |
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| <div align="center">
| | == Diagnosis == |
| <gallery heights="175" widths="175">
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| Image:c4.htm4.jpg|Left Bundle Branch Block <small> [http://www.ganseman.com/ecgbibnl.htm#_top000 Image courtesy of Dr Jose Ganseman]</small>
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| Image:c5.htm5.jpg|Left Bundle Branch Block <small> [http://www.ganseman.com/ecgbibnl.htm#_top000 Image courtesy of Dr Jose Ganseman]</small>
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| </gallery>
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| </div>
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| | [[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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| <div align="center">
| | == Treatment == |
| <gallery heights="175" widths="175">
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| Image:c6.htm6.jpg|Left Bundle Branch Block <small> [http://www.ganseman.com/ecgbibnl.htm#_top000 Image courtesy of Dr Jose Ganseman]</small>
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| Image:c7.htm7.jpg|Left Bundle Branch Block <small> [http://www.ganseman.com/ecgbibnl.htm#_top000 Image courtesy of Dr Jose Ganseman]</small>
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| </gallery>
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| </div>
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| | [[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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| <div align="center">
| | ==Case Studies== |
| <gallery heights="175" widths="175">
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| Image:c8.htm8.jpg|Left Bundle Branch Block <small> [http://www.ganseman.com/ecgbibnl.htm#_top000 Image courtesy of Dr Jose Ganseman]</small>
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| Image:c9.htm9.jpg|Left Bundle Branch Block + Left Anterior Fascicular Block <small> [http://www.ganseman.com/ecgbibnl.htm#_top000 Image courtesy of Dr Jose Ganseman]</small>
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| </gallery>
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| </div>
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| | [[Left bundle branch block case study one|Case #1]] |
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| <div align="center">
| | ==Related Chapters== |
| <gallery heights="175" widths="175">
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| Image:ECG RBTB LAtrD.jpg|Left Bundle Branch Block + Left Anterior Fascicular Block + Left atrial enlargement
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| Image:r10.ht35.jpg|Left Bundle Branch Block + Supraventricular tachycardia <small> [http://www.ganseman.com/ecgbibnl.htm#_top000 Image courtesy of Dr Jose Ganseman]</small>
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| </gallery>
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| </div>
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| <div align="center">
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| <gallery heights="175" widths="175">
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| Image:LBBB with Lateral Q waves.CMG.jpg|LBBB with Lateral Q waves <small>Image courtesy of [[C. Michael Gibson]] MS MD and Copylefted</small>
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| Image:LBBB.CMG.jpg|Left Bundle Branch Block <small>Image courtesy of [[C. Michael Gibson]] MS MD and Copylefted</small>
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| </gallery>
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| </div>
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| ==See also==
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| * [[Bundle branch block]] | | * [[Bundle branch block]] |
| * [[Right bundle branch block]] | | * [[Right bundle branch block]] |
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| == References ==
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| {{Reflist}}
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| ==External links==
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| * http://library.med.utah.edu/kw/ecg/mml/ecg_lbbb.html
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| ==Additional resources==
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| * [http://en.ecgpedia.org ECGpedia: Course for interpretation of ECG]
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| * [http://www.anaesthetist.com/icu/organs/heart/ecg/ The whole ECG - A basic ECG primer]
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| * [http://www.ecglibrary.com 12-lead ECG library]
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| * [http://www.ecgsim.org Simulation tool to demonstrate and study the relation between the electric activity of the heart and the ECG]
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| * [http://heartcenter.seattlechildrens.org/what_to_expect/electrocardiogram.asp ECG information from Children's Hospital Heart Center, Seattle]
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| * [http://www.regionalpci-stemi.org/id10.html ECG Challenge from the ACC D2B Initiative]
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| * [http://0-www.nhlbi.nih.gov.innopac.up.ac.za:80/health/dci/Diseases/ekg/ekg_what.html National Heart, Lung, and Blood Institute, Diseases and Conditions Index]
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| * [http://www.ecglibrary.com/ecghist.html A history of electrocardiography]
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| * [http://www.health.gov.mt/impaedcard/issue/issue1/ipc00103.htm EKG Interpretations in infants and children]
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| {{Electrocardiography}}
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| {{SIB}}
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| [[Category:Cardiology]] | | [[Category:Cardiology]] |
| [[Category:Electrophysiology]] | | [[Category:Electrophysiology]] |
| | [[Category:Arrhythmia]] |
| [[Category:Emergency medicine]] | | [[Category:Emergency 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]] |
