QT Interval: How to Measure It and What Is "Normal"

Ilan Goldenberg, M.D.; Arthur J. Moss, M.D.; Wojciech Zareba, M.D., Ph.D.

Disclosures

J Cardiovasc Electrophysiol. 2006;17(3):333-336. 

In This Article

Conclusions and Recommendations

The simple measurement of the QT interval is valuable for the diagnosis of abnormal QTc intervals. However, the routine measurement of the QT interval requires the use of uniform criteria for the determination of T-wave offset (especially when there is partial superimposition of the T and U wave), adjustment for heart rate, and T-wave morphology.

In a recent study,[4] correct classification of QT intervals (either "long" or "normal") using only manually measured QT and RR intervals was achieved by 96% of QT experts and 62% of arrhythmia experts, but by only <25% of cardiologists and noncardiologists. Clearly, experience and training play an important role in the accurate measurement of the QTc interval.

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