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2,001 bytes added, 09:16, 25 August 2012
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[[MI Diagnosis in LBBB|Diagnosis of myocardial infarction in LBBB]] can be difficult.
==Other definitions==
The above definition of left bundle branch block is rather broad. In selecting patients for '''CRT-D therapy''' (cardiac resynchronization therapy) there has been debate whether a more specific definition should be used. In the RAFT trial the following AHA/ESC definition was used<cite>Tang</cite>:
'''Complete LBBB'''
#QRS duration greater than or equal to 120 ms in adults, greater than 100 ms in children 4 to 16 years of age, and greater than 90 ms in children less than 4 years of age.
#Broad notched or slurred R wave in leads I, aVL, V5, and V6 and an occasional RS pattern in V5 and V6 attributed to displaced transition of QRS complex.
#Absent q waves in leads I, V5, and V6, but in the lead aVL, a narrow q wave may be present in the absence of myocardial pathology.
#R peak time greater than 60 ms in leads V5 and V6 but normal in leads V1, V2, and V3, when small initial r waves can be discerned in the above leads.
#ST and T waves usually opposite in direction to QRS.
#Positive T wave in leads with upright QRS may be normal (positive concordance).
#Depressed ST segment and/or negative T wave in leads with negative QRS (negative concordance) are abnormal.
#The appearance of LBBB may change the mean QRS axis in the frontal plane to the right, to the left, or to a superior, in some cases in a rate-dependent manner.
'''Incomplete LBBB'''
#QRS duration between 110 and 119 ms in adults, between 90 and 100 ms in children 8 to 16 years of age, and between 80 and 90 ms in children less than 8 years of age.
#Presence of left ventricular hypertrophy pattern.
#R peak time greater than 60 ms in leads V4, V5, and V6.
#Absence of q wave in leads I, V5, and V6.
Also a narrow initial R wave in V1 has been linked with a reduced response to CRT.<cite>Mascioli</cite>
In general when the QRS is wide and the definitions of LBBB and RBBB are not met, the term NIVCD (non-specific intraventricular conduction delay) is used.
Also read [[RBBB|right bundle branch block]].
#Garcia isbn=0763722464
#wellens isbn=9781416002598
#Mascioli pmid=22651702
#Tang pmid=21073365

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