Left bundle branch block - wikipedia Left bundle branch block Left bundle branch block ECG characteristics of a typical LBBB showing wide QRS complexes with abnormal morphology in leads V1 and V6. Classification and external resources Specialty Cardiology, Emergency Medicine ICD - 10 I44. 4 - I44. 7 DiseasesDB 7352 eMedicine ped / 2501 ( edit on Wikidata ) Left bundle branch block ( LBBB ) is a cardiac conduction abnormality seen on the electrocardiogram ( ECG ). In this condition, activation of the left ventricle of the heart is delayed, which causes the left ventricle to contract later than the right ventricle. Contents 1 Causes 2 Diagnosis 2.1 Diagnostic consequences 3 Treatment 4 See also 5 References 6 External links Causes Among the causes of LBBB are : Aortic stenosis Dilated cardiomyopathy Acute myocardial infarction Extensive coronary artery disease Primary disease of the cardiac electrical conduction system Long standing hypertension leading to aortic root dilatation and subsequent aortic regurgitation Lyme disease Side effect of some cardiac surgeries ( e.g., aortic root reconstruction ) Diagnosis Electrocardiogram showing left bundle branch block and irregular rhythm due to supraventricular extrasystoles. A left bundle branch block The criteria to diagnose a left bundle branch block on the electrocardiogram : The heart rhythm must be supraventricular in origin The QRS duration must be ≥ 120 ms There should be a QS or rS complex in lead V1 There should be a notched ( 'M ' - shaped ) R wave in lead V6. 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. There are also partial blocks of the left bundle branch : `` left anterior fascicular block '' ( LAFB ) and a `` left posterior fascicular block '' ( LPFB ). This refers to the bifurcation of the left bundle branch. Diagnostic consequences The presence of LBBB results in that electrocardiography ( ECG ) can not be used to diagnose left ventricular hypertrophy or Q wave infarction, because LBBB in itself results in widened QRS complex, and changes in the ST - T segment consistent with ischemia or injury. Treatment Patients with LBBB require complete cardiac evaluation, and those with LBBB and syncope or near - syncope may require a pacemaker. Some patients with LBBB, a markedly prolonged QRS ( usually > 150 ms ), and systolic heart failure may benefit from a biventricular pacemaker, which allows for better synchrony of heart contractions. See also Bundle branch block Right bundle branch block Sgarbossa 's criteria References Jump up ^ `` Conduction Blocks 2006 KCUMB ''. Retrieved 2009 - 01 - 20. Jump up ^ `` Lesson VI - EKG Conduction Abnormalities ''. Retrieved 2009 - 01 - 07. Jump up ^ `` more detailed information about left anterior fascicular block ''. GPnotebook. Jump up ^ `` more detailed information about left posterior fascicular block ''. GPnotebook. Jump up ^ Emily Groepper ; Nasar Nallamothu ; Wilfred Lam ; Frank Aguirre ; Kristi Bergman ; Patricia Good ; Patricia Wright ( May 13, 2014 ). `` Electrocardiography > Left Bundle Branch Block ( LBBB ) ''. SIU School of Medicine. Retrieved 2015 - 07 - 02. Jump up ^ Stevenson WG, Hernaddez AF, Carson PE, et al. Indications for cardiac resynchronization therapy : 2011 update from the Heart Failure Society of America guideline committee. J Card Fail 2012 ; 18 : 94 - 106. External links http://library.med.utah.edu/kw/ecg/mml/ecg_lbbb.html Cardiovascular disease ( heart ) ( I00 -- I52, 390 -- 429 ) Ischaemic Coronary disease Coronary artery disease ( CAD ) Coronary artery aneurysm Spontaneous coronary artery dissection ( SCAD ) Coronary thrombosis Coronary vasospasm Myocardial bridge Active ischemia Angina pectoris Prinzmetal 's angina Stable angina Acute coronary syndrome Myocardial infarction Unstable angina Sequelae hours Hibernating myocardium Myocardial stunning days Myocardial rupture weeks Aneurysm of heart / Ventricular aneurysm Dressler syndrome Layers Pericardium Pericarditis Acute Chronic / Constrictive Pericardial effusion Cardiac tamponade Hemopericardium Myocardium Myocarditis Chagas disease Cardiomyopathy Dilated Alcoholic Hypertrophic Restrictive Loeffler endocarditis Cardiac amyloidosis Endocardial fibroelastosis Arrhythmogenic right ventricular dysplasia Endocardium / valves Endocarditis infective endocarditis Subacute bacterial endocarditis non-infective endocarditis Libman -- Sacks endocarditis Nonbacterial thrombotic endocarditis Valves mitral regurgitation prolapse stenosis aortic stenosis insufficiency tricuspid stenosis insufficiency pulmonary stenosis insufficiency Conduction / arrhythmia Bradycardia Sinus bradycardia Sick sinus syndrome Heart block : Sinoatrial AV 1 ° 2 ° 3 ° Intraventricular Bundle branch block Right Left Left anterior fascicle Left posterior fascicle Bifascicular Trifascicular Adams -- Stokes syndrome Tachycardia ( paroxysmal and sinus ) Supraventricular Atrial Multifocal Junctional AV nodal reentrant Junctional ectopic Ventricular Accelerated idioventricular rhythm Catecholaminergic polymorphic Torsades de pointes Premature contraction Atrial Junctional Ventricular Pre-excitation syndrome Lown -- Ganong -- Levine Wolff -- Parkinson -- White Flutter / fibrillation Atrial flutter Ventricular flutter Atrial fibrillation Familial Ventricular fibrillation Pacemaker Ectopic pacemaker / Ectopic beat Multifocal atrial tachycardia Pacemaker syndrome Parasystole Wandering pacemaker Long QT syndrome Andersen -- Tawil Jervell and Lange - Nielsen Romano -- Ward Cardiac arrest Sudden cardiac death Asystole Pulseless electrical activity Sinoatrial arrest Other / ungrouped hexaxial reference system Right axis deviation Left axis deviation QT Short QT syndrome T wave alternans ST Osborn wave ST elevation ST depression Strain pattern Cardiomegaly Ventricular hypertrophy Left Right / Cor pulmonale Atrial enlargement Left Right Other Cardiac fibrosis Heart failure Diastolic heart failure Cardiac asthma Rheumatic fever Retrieved from `` https://en.wikipedia.org/w/index.php?title=Left_bundle_branch_block&oldid=781361187 '' Categories : Cardiogenetic disorders Hidden categories : Infobox medical condition Talk Contents About Wikipedia Azərbaycanca Deutsch Español Français Bahasa Indonesia Italiano עברית 日本 語 Norsk Polski Português 5 more Edit links This page was last edited on 20 May 2017, at 19 : 28. 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Question: what is a left bundle branch block in the heart
Answer: a cardiac conduction abnormality