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Lookup NU author(s): Emeritus Professor Alan MurrayORCiD
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Cardiac repolarization abnormalities can be assessed from measurements of the QT duration taken from paper electrocardiogram recordings. Errors associated with determining the end of the T wave are known, but those associated with the start of the Q wave have so far been neglected. This paper quantifies the variation in manual identification of the start of the Q wave, and assesses its contribution to errors in the manual measurement of QT. A randomized study of errors in the timing of Q wave initiation from electrocardiograms plotted on paper was conducted, Four electrocardiogram leads were recorded in eight subjects relaxing in a semirecumbent position, Manual measurements were made of the time of Q wave initiation in 512 electrocardiograms, presented with different superimposed noise, recording speed and recording gain. The greatest mean difference between four cardiologists amounted to 6.7 ms. A recording gain of 5 mm mV(-1), in comparison with 10 mm mV(-1), resulted in a difference in Q wave timing of 3.2 ms (P < 0.05). A further increase in gain, or the addition of noise up to 20 mu V made no significant difference to Q wave measurements. Provided EGGS Of at least 10 mm mV(-1) are used, the effect of variation in Q determination on QT measurement is likely to be small.
Author(s): MURRAY A, MCLAUGHLIN NB
Publication type: Article
Publication status: Published
Journal: PHYSIOLOGICAL MEASUREMENT
Print publication date: 01/02/1995