Cardiovascular medicine
Time dependent variability of QT dispersion after acute
myocardial infarction and its relation to ventricular fibrillation: a
prospective study
J D Aitchison, R W F Campbell, P D Higham
Academic Department
of Cardiology, Freeman Hospital, Newcastle-upon-Tyne NE7 7DN, UK
Correspondence to: Mr Aitchison j.d.aitchison{at}ncl.ac.uk
Accepted 16 August
2000
OBJECTIVE
To show whether increased
QT dispersion on admission predicts ventricular fibrillation after
acute myocardial infarction, and to determine the nature of time
related changes in QT dispersion.
DESIGNProspective cohort study.
SETTINGCoronary care units of three
teaching hospitals in Newcastle-upon-Tyne over an eight month period.
PATIENTSAll had acute myocardial
infarction according to World Health Organization criteria.
INTERVENTIONSFor all patients, QT
dispersion (QTd) and Bazett rate corrected QTc dispersion (QTcd) were
measured from a high quality 12 lead ECG recorded on admission at a
paper speed of 50 mm/s. In a subset, serial ECGs were recorded
regularly to show time related changes in QTcd following acute
myocardial infarction.
MAIN OUTCOME MEASURESOccurrence of
ventricular fibrillation within the first 24 hours after myocardial infarction.
RESULTSData collected from 201 patients, 12 of whom (6%) developed ventricular fibrillation within 24 hours. Neither QTd nor QTcd differed between those developing
ventricular fibrillation and those who did not: QTd mean (SD), 74 (24) ms (95% confidence interval (CI) 59 to 89)
v 66 (24) ms (95% CI 62 to 70),
respectively; QTcd, 86 (26) ms0.5 (95% CI 70 to 102)
v 77 (29) ms0.5 (95% CI 72 to
82), respectively. Significant QTcd changes occurred early after
myocardial infarction.
CONCLUSIONSAdmission QTd and QTcd do
not predict ventricular fibrillation after acute myocardial infarction.
There are significant changes in QTcd with time, which may account for
this measured lack of correlation.
Keywords: acute myocardial infarction; arrhythmia; ventricular fibrillation; QT dispersion
© 2000 by Heart
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