Title:The Measurement of the QT Interval
Volume: 10
Issue: 3
Author(s): Pieter G. Postema and Arthur A.M. Wilde
Affiliation:
Keywords:
QT interval, long QT syndrome, arrhythmias, sudden death.
Abstract: The evaluation of every electrocardiogram should also include an effort to interpret the QT interval to assess
the risk of malignant arrhythmias and sudden death associated with an aberrant QT interval. The QT interval is measured
from the beginning of the QRS complex to the end of the T-wave, and should be corrected for heart rate to enable comparison
with reference values. However, the correct determination of the QT interval, and its value, appears to be a daunting
task. Although computerized analysis and interpretation of the QT interval are widely available, these might well
over- or underestimate the QT interval and may thus either result in unnecessary treatment or preclude appropriate measures
to be taken. This is particularly evident with difficult T-wave morphologies and technically suboptimal ECGs. Similarly,
also accurate manual assessment of the QT interval appears to be difficult for many physicians worldwide. In this
review we delineate the history of the measurement of the QT interval, its underlying pathophysiological mechanisms and
the current standards of the measurement of the QT interval, we provide a glimpse into the future and we discuss several
issues troubling accurate measurement of the QT interval. These issues include the lead choice, U-waves, determination of
the end of the T-wave, different heart rate correction formulas, arrhythmias and the definition of normal and aberrant QT
intervals. Furthermore, we provide recommendations that may serve as guidance to address these complexities and which
support accurate assessment of the QT interval and its interpretation.
