Hemiblock Case Studies

Home » MEDCLIN530 » EKG » 12-Lead EKG Confidence » IV. EKG Changes Related to Conduction Abnormalities » 10. Hemiblock » Hemiblock Case Studies
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Chris Anderson
Vice Chair, Pediatrics
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Kevin Hodges
Vice Chair, Emergency Medicine
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Table of Contents

Case 1: Left anterior hemiblock, step-by-step example

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  1. Lead I is positive, so the QRS direction is to the patient’s left side (somewhere between –90 and +90).
  2. Lead AVF is negative, so the QRS direction is upward (this narrows it down to between 0 and –90).
  3. Lead II is negative, so the QRS direction is more negative than –30 (this narrows it down to between –30 and –90).
  4. Lead AVR is negative, so the QRS direction is more positive than –60. Thus the QRS is between –30 and –60, or –45!
  5. We visualize the QRS direction in the frontal plane as pointing toward the patient’s left shoulder. This is the diagnostic characteristic of LAHB.

Case 2: Left posterior hemiblock, step-by-step example

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  1. Lead I is negative, so the QRS direction is to the patient’s right side (somewhere more negative than –90, or more positive than +90).
  2. Lead AVF is positive, so the QRS direction is downward (this narrows it down to between +90 and +180).
  3. Lead II is positive, so the QRS direction is less than +150 (this narrows it down to between +90 and +150).
  4. Lead AVR is close to isoelectric, so the QRS direction is perpendicular to it. Thus the QRS is either –60 or +120!
  5. We visualize the QRS direction in the frontal plane as pointing toward the patient’s right foot. This is the diagnostic characteristic of LPHB.

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