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Pediatric Left Bundle Branch Block Workup

  • Author: Bahram Kakavand, MD, FACC; Chief Editor: Stuart Berger, MD  more...
 
Updated: Jan 12, 2015
 

Laboratory Studies

In left bundle branch block (LBBB), blood work is rarely necessary; however, assessing cardiac enzymes (troponins, creatine kinase [CK]) and the erythrocyte sedimentation rate (ESR) may be useful if myocarditis is suspected. When cardiomyopathy is considered, specific blood work to evaluate underlying causes may be helpful.

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Imaging Studies

Cardiac evaluation requires thorough physical examination, repeat ECG, and echocardiography.

Chest radiography may be helpful, depending on the clinical circumstances

A 24-hour ambulatory ECG recording can reveal other arrhythmias (eg, second-degree or third-degree heart block, atrial or ventricular extrasystoles, atrial or ventricular tachycardia). One study reported alternating right and left bundle branch block in a patient with atrial tachycardia.[1] {{Ref6

Other investigational studies may be performed to evaluate for suspected associated abnormalities that may be the cause of left bundle branch block.

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Other Tests

The following diagnostic ECG criteria have been established:

  • QRS duration of 120 milliseconds (ms) or more in adults, more than 100 ms in children aged 4-16 years, and more than 90 ms in children younger 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: In the lead aVL, a narrow q wave may be present in the absence of myocardial pathology.
  • R peak time of more than 60 ms in leads V5 and V6 but normal peak time 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
  • Possible normal positive T wave in leads with upright QRS (positive concordance)
  • Depressed ST segment and/or negative T wave in leads with negative QRS (negative concordance): This is abnormal and is discussed in part VI of this statement.
  • Changed mean QRS axis in the frontal plane to the right, to the left, or to a superior possible with left bundle branch block (in some cases in a rate-dependent manner)

ECG criteria necessary to confirm the diagnosis of left anterior hemiblock (LAH) in children include the following:

  • The duration of the QRS complex is normal for the patient's age or prolonged by less than 0.02 s.
  • The frontal-plane QRS axis is less than -30°.
  • A Q wave is present in lead I and a deep Q wave is present in lead aVL.
  • Major QRS forces in lead aVF are negative.
  • Slurred S waves are present in the left precordial leads.
  • A late R wave (delay, >0.045 s) is observed in lead aVR.
  • The terminal R wave in lead aVL is slurred.

Presence of LAH pattern in children usually reflects certain types of congenital heart defects, particularly endocardial cushion defects. Note the following:

  • In this group, the left anterior division of the left bundle is either congenitally absent or severely hypoplastic.
  • A superior frontal-plane QRS axis may occur in other congenital heart defects (double-outlet right ventricle, tricuspid atresia, single ventricle) with a normal anterior fascicle.
  • The literal diagnosis of LAH can be reserved for patients with previously normal ECG findings who develop left axis deviation after congenital heart surgery or other injury to the left anterior fascicle.

In left posterior hemiblock, ECG criteria necessary to confirm the diagnosis of left posterior hemiblock in children include the following:

  • The duration of the QRS axis is normal or only slightly prolonged for the patient's age.
  • A Q wave is present in leads II, III, and aVF.
  • The frontal plane QRS axis is +120° to +180°.
  • An S wave is present at the end of the QRS complex in leads I and aVF.

A study by Rivard et al indicated that in patients who develop new-onset left bundle branch block after transcatheter aortic valve replacement (TAVR), the postoperative occurrence of an HV interval of 65 milliseconds or more is predictive of an AV block. The study, which involved 75 pacemaker-free patients who underwent TAVR, included 30 who subsequently developed left bundle branch block, eight of whom also developed AV block. The length of the HV interval was found to have a sensitivity and specificity of 83.3% and 81.6%, respectively, in predicting AV block in the patients with new-onset left bundle branch block.[7]

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Contributor Information and Disclosures
Author

Bahram Kakavand, MD, FACC Assistant Professor of Pediatrics, Pediatric Cardiology and Electrophysiology, University of Kentucky College of Medicine

Disclosure: Nothing to disclose.

Specialty Editor Board

Mary L Windle, PharmD Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Alvin J Chin, MD Emeritus Professor of Pediatrics, University of Pennsylvania School of Medicine

Alvin J Chin, MD is a member of the following medical societies: American Association for the Advancement of Science, Society for Developmental Biology, American Heart Association

Disclosure: Nothing to disclose.

Chief Editor

Stuart Berger, MD Medical Director of The Heart Center, Children's Hospital of Wisconsin; Associate Professor, Department of Pediatrics, Section of Pediatric Cardiology, Medical College of Wisconsin

Stuart Berger, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology, American College of Chest Physicians, American Heart Association, Society for Cardiovascular Angiography and Interventions

Disclosure: Nothing to disclose.

Additional Contributors

Christopher Johnsrude, MD, MS Chief, Division of Pediatric Cardiology, University of Louisville School of Medicine; Director, Congenital Heart Center, Kosair Children's Hospital

Christopher Johnsrude, MD, MS is a member of the following medical societies: American Academy of Pediatrics, American College of Cardiology

Disclosure: Nothing to disclose.

Acknowledgements

The authors and editors of Medscape Drugs & Diseases gratefully acknowledge the contributions of previous author Christopher Mart, MD, to the development and writing of this article.

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ECGs show a normal sinus rhythm and a sinus rhythm with a left bundle branch block.
Anatomy of the penetrating portion of the atrioventricular (AV) bundle.
ECG depicts electrophysiologic events in normal cardiac conduction. AV = atrioventricular.
Pathophysiology of left bundle branch block. AV = atrioventricular; LV = left ventricular; RV = right ventricular.
ECG depicts electrophysiologic events of left bundle branch block.
 
 
 
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