Time dependent variability of QT dispersion after acute myocardial infarction and its relation to ventricular fibrillation: a prospective study.
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.


METHODS
Prospective cohort study.


METHODS
Coronary care units of three teaching hospitals in Newcastle-upon-Tyne over an eight month period.


METHODS
All had acute myocardial infarction according to World Health Organization criteria.


METHODS
For 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.


METHODS
Occurrence of ventricular fibrillation within the first 24 hours after myocardial infarction.


RESULTS
Data 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) ms(0.5) (95% CI 70 to 102) v 77 (29) ms(0.5) (95% CI 72 to 82), respectively. Significant QTcd changes occurred early after myocardial infarction.


CONCLUSIONS
Admission 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.
Aitchison
J D
JD
Academic Department of Cardiology, Freeman Hospital, Newcastle-upon-Tyne NE7 7DN, UK. j.d.aitchison@ncl.ac.uk
Campbell
R W
RW
Higham
P D
PD
D000368:Aged; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications / Q000503:physiopathology*; D011446:Prospective Studies; D012307:Risk Factors; D013997:Time Factors; D014693:Ventricular Fibrillation / Q000175:diagnosis* / Q000209:etiology