What are the electrocardiogram (ECG) findings if Mahaim fibers are present?

Updated: Jan 08, 2017
  • Author: Christopher R Ellis, MD, FACC, FHRS; Chief Editor: Mikhael F El-Chami, MD  more...
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Answer

If Mahaim fibers are present, the ECG findings are a normal or long PR interval and an abnormally wide QRS complex with a left-bundle appearance. Preexcitation may not be apparent during sinus rhythm but can be demonstrated with premature right atrial stimulation. Because retrograde conduction is absent, only an antidromic AV reentry tachycardia (ie, preexcited tachycardia) can develop.


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