Case Report (n=1)
QT hysteresis can result in transient QTc shortening after rhythm conversion, highlighting the need for careful interpretation of QT intervals during antiarrhythmic therapy.
Supports cautious QTc interpretation post-conversion; leaves open confirmation of functional benefit in larger trials.
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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Kamareddine et al. (2026) conducted a case report in atrial fibrillation (n=1). direct-current cardioversion was evaluated on QTc interval.
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