Time-Dependent Changes in QT Dynamics after Initiation and Termination of Paroxysmal Atrial Fibrillation

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Abstract

Background:

Little is known about time-dependent changes in QT dynamics after initiation of atrial fibrillation (AF) and after restoration of sinus rhythm (SR) in patients with paroxysmal AF.

Methods:

Beat-to-beat QT and RR intervals in CM5 lead were measured automatically in 13 patients with both AF and SR on the single 24-hour Holter electrocardiology recording. QT-RR relation was analyzed at six periods of time: 1 hour before AF onset (Pre0–1h), 0–1 hour and 4–5 hours after AF onset (AF0–1h and AF4–5h), and 0–1 hour, 2–3 hours, and 4–5 hours after the restoration of SR (SR0–1h, SR2–3h, and SR4–5h).

Results:

QT-RR slope was gradually decreased after AF onset and gradually returned to the baseline level after restoration of SR. The slope became greater at SR4–5h than at AF4–5h and AF0–1h. In patients receiving antiarrhythmic drugs (AADs; n = 5), QT-RR slope was greater at SR4–5h than in those not receiving AADs (n = 8).

Conclusion:

In patients with paroxysmal AF, bradycardia-dependent QT prolongation was attenuated during AF, and was corrected and gradually augmented along with continuation of SR, especially in patients receiving AADs. This could increase the risk of developing torsade de pointes.

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