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When QTc Shrinks After Rhythm Conversion
Mohammed Hussein Kamareddine1, Alyssa Zakala1, Farid Farkouh1
1Lankenau Medical Center, Main Line Health, Wynnewood, Pennsylvania, USA.
Case Summary:
An 83-year-old man with a history of atrial fibrillation on amiodarone therapy was admitted for direct-current cardioversion because of recurrent atrial fibrillation with a ventricular rate of approximately 105 beats per minute. Cardioversion successfully restored sinus rhythm. Postcardioversion 12-lead electrocardiography revealed an unexpectedly short QTc of 344 ms despite chronic treatment with a QT-prolonging agent. This finding was attributed to QT hysteresis, reflecting delayed adaptation of ventricular repolarization to the abrupt reduction in heart rate after rhythm conversion.
Take-Home Message:
QT hysteresis can result in transient QTc shortening and has important implications for interpretation of QT intervals during antiarrhythmic therapy.
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