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Corrected QT in ventricular paced rhythms: what is the validation for commonly practiced assumptions?
Saneka Chakravarty1, Jeffrey Kluger, Lovely Chhabra
1Department of Cardiovascular Medicine, Hartford Hospital, Hartford, Conn., USA.
Cardiology
|March 21, 2015
Summary
Subtracting 50 ms from corrected QT (QTc) during ventricular pacing (VP) is accurate at average heart rates. However, this 50-ms adjustment may underestimate QTc at faster heart rates.
Area of Science:
- Cardiology
- Electrophysiology
- Medical Device Technology
Background:
- Ventricular pacing (VP) can affect QT interval accuracy due to QRS widening.
- Current clinical practice subtracts 50 ms from corrected QT (QTc) in ventricular paced rhythms.
- The accuracy of this 50-ms adjustment requires further investigation.
Purpose of the Study:
- To evaluate the accuracy of the 50-ms subtraction method for corrected QT (QTc) intervals during ventricular pacing (VP).
- To compare QTc measurements between native rhythms and ventricular paced rhythms.
Main Methods:
- Prospective observational study involving 23 pacemaker patients.
- Recorded four ECGs per patient: two at native rate, two at 100 bpm ventricular pacing.
- Compared averaged QTc in ventricular paced rhythm versus non-ventricular-paced QTc.
Main Results:
- At a mean heart rate of 66 bpm, the mean QTc difference was 48.27 ms (p < 0.001).
- At faster paced rates, the mean QTc difference increased to 81.3 ms (p = 0.002).
Conclusions:
- The 50-ms subtraction for QTc during VP is accurate within ±16 ms at an average heart rate of 66 bpm.
- At faster heart rates, the 50-ms adjustment may underestimate the QTc discrepancy.
- Clinical practice may need adjustment for faster heart rates during ventricular pacing.
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