Heart 1997;78:371-375 ( October )
Dispersion of ventricular repolarisation: a marker of ventricular arrhythmias in patients with previous myocardial infarction
Division of Cardiology, Cliniques Universitaires Saint
Luc and Faculty of Medicine, University of Louvain, Brussels, Belgium
Correspondence to: Dr C Brohet, Clinique Saint
Luc
Service de Cardiologie, Avenue Hippocrate 10/2881, B 1200 Brussels, Belgium.
Accepted for publication 10 June 1996
Objective
To examine whether, in
coronary patients after myocardial infarction, the dispersion of
ventricular repolarisation measured through QT and JT intervals from a
surface electrocardiogram could allow separation of those with
ventricular tachyarrhythmias (VT) complicating their myocardial infarct
from those without.
Design
A retrospective comparative study.
Setting
University hospital.
Patients
39 patients with myocardial infarction
complicated by VT, 300 patients after myocardial infarction without
arrhythmic events, and 1000 normal subjects. The myocardial infarction
groups were divided into anterior, inferior, and mixed locations.
Interventions
A computer algorithm examined an
averaged cycle from a 10 second record of 15 simultaneous leads (12 lead ECG + Frank XYZ leads). After interactive editing, four intervals
were computed: QTapex, JTapex, QTend, and JTend. For each interval, the
dispersion was defined as the difference between the maximum and
minimum values across the 15 leads.
Results
The mean values of all four
dispersion indices were higher in patients with myocardial infarction
than in normal subjects (p < 0.01). In the infarct groups, patients
with VT had significantly greater mean and centile dispersion values
than those without VT. For instance, the 97.5th centile value of QTend
was 65 ms in normal individuals, 90 ms in infarct patients without
arrhythmia, and 128 ms in those with VT; 70% of the infarct patients
who developed serious ventricular arrhythmias had values exceeding the
97.5th centile of the normal group, while only 18% of the infarct
patients without arrhythmia had dispersion values above this normal
upper limit. Among the infarct patients, nearly half of those (18 of 39) with tachyarrhythmias had dispersion values that exceeded the
97.5th centile of those without arrhythmia.
Conclusions
Dispersion of
ventricular repolarisation may be a good non-invasive tool for
discriminating coronary patients susceptible to VT from those who are
at low risk.
© 1997 by Heart
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