Key result
When QT interval cannot be measured in Lead II, lead aVR is the best alternative, showing the least absolute difference in QT interval of 8.7 ms compared to Lead II.
Why the study?
Which alternative ECG lead provides QT interval measurements closest to Lead II in healthy volunteers?
Observational (n=1,906)
Which alternative ECG lead provides QT interval measurements closest to Lead II in healthy volunteers?
Answers are grounded in this paper and cite their sources.
When the QT interval cannot be measured in Lead II, leads aVR, aVF, V5, V6, and V4 are the best alternatives, whereas lead aVL should be avoided.
INTRODUCTION: Conventionally, QT interval is measured in lead II. There are no data to select an alternative lead for QT measurement when it cannot be measured in Lead II for any reason. METHODS AND RESULTS: We retrospectively analyzed ECGs from 1906 healthy volunteers from 41 phase I studies. QT interval was measured on the median beat in all 12 leads. The mean difference in QT interval between lead aVR and in Lead II was the least, followed by aVF, V5, V6 and V4; lead aVL had maximum difference. The T wave was flat (<0.1 mV) in Lead II in 6.9% of ECGs; it was also flat in 20% of these ECGs (1.4% of all ECGs) in Leads aVR, aVF and V5. CONCLUSIONS: When QT interval cannot be measured in Lead II, the best alternative leads are aVR, aVF, V5, V6 and V4 in that sequence. It differs maximally from that in Lead II in Lead aVL.
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Salvi et al. (2012) conducted an observational in Healthy volunteers (n=1,906). Lead aVR vs. Lead II was evaluated on Absolute difference in QT interval compared to Lead II (ms) (95% CI 8.1-9.4, p=<0.001). When QT interval cannot be measured in Lead II, lead aVR is the best alternative, showing the least absolute difference in QT interval of 8.7 ms compared to Lead II.
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