Financial support: Unrestricted grants for analyses of Holter data were provided to Drs. Couderc and Zareba of University of Rochester by Pfizer and to Dr. Badilini of AMPS-LLC by DMR, a legacy company of Daiichi Sankyo Pharma Development.
Analyses of Dynamic Beat-to-Beat QT–TQ Interval (ECG Restitution) Changes in Humans under Normal Sinus Rhythm and Prior to an Event of Torsades de Pointes during QT Prolongation Caused by Sotalol
Article first published online: 24 OCT 2007
Annals of Noninvasive Electrocardiology
Volume 12, Issue 4, pages 338–348, October 2007
How to Cite
Fossa, A. A., Wisialowski, T., Crimin, K., Wolfgang, E., Couderc, J.-P., Hinterseer, M., Kaab, S., Zareba, W., Badilini, F. and Sarapa, N. (2007), Analyses of Dynamic Beat-to-Beat QT–TQ Interval (ECG Restitution) Changes in Humans under Normal Sinus Rhythm and Prior to an Event of Torsades de Pointes during QT Prolongation Caused by Sotalol. Annals of Noninvasive Electrocardiology, 12: 338–348. doi: 10.1111/j.1542-474X.2007.00183.x
- Issue published online: 24 OCT 2007
- Article first published online: 24 OCT 2007
- QT prolongation;
- restitution, torsades de pointes;
Background: Restitution through intracardiac pacing has been used to assess arrhythmia vulnerability. We examined whether analyses of sequential beat-to-beat QT and TQ interval measures can be used to quantify ECG restitution changes under normal sinus rhythm.
Methods: The QT, R-R and TQ intervals were examined 22.5 hour Holter monitoring before and after oral sotalol in normal male and female volunteers. Additionally, comparisons were made to those observed in the time-matched dataset prior to torsades de pointes in a heart diseased patient that received a single dose of sotalol.
Results: Sotalol increased QT, R-R and TQ intervals 71, 101, and 125 ms after 160 mg (n = 38) and 194, 235, and 135 ms after 320 mg (n = 19) during maximum plasma concentrations, respectively. The percentage of beats with a QT/TQ ratio >1 was reduced 25% over the entire 22.5 hours after sotalol and the lower TQ interval boundary (5th quantile) was increased 22–30%. In contrast, 99% of the beats prior to torsades de pointes had a QT/TQ ratio > 1 and the median TQ interval was below the lower 98% confidence bounds of normals before and after sotalol.
Conclusions: ECG restitution changes are quantifiable under varying states (nocturnally, beta-adrenergic blockade, QT prolongation) in healthy subjects.