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QT interval dispersion in chronic heart failure and left ventricular hypertrophy: relation to autonomic nervous
P P Davey1, J Bateman, I P Mulligan
1Department of Cardiovascular Medicine, John Radcliffe Hospital, Oxford.
Insights
QT dispersion is elevated in left ventricular hypertrophy and heart failure, but does not predict ventricular arrhythmias. Abnormal QT dispersion and distribution in these conditions do not reflect arrhythmic risk.
Area of Science:
- Cardiology
- Electrophysiology
- Cardiac Pathophysiology
Background:
- Left ventricular hypertrophy (LVH) and chronic heart failure (CHF) are associated with altered cardiac electrical activity.
- QT dispersion, a measure of repolarization heterogeneity, is a potential marker for arrhythmic risk.
Purpose of the Study:
- To investigate QT dispersion in patients with LVH and CHF.
- To determine the relationship between QT dispersion and ventricular arrhythmias in these patient groups.
Main Methods:
- QT dispersion was measured using 12-lead electrocardiograms in patients with LVH (n=14), CHF (n=18), and controls (n=17).
- Analysis included QT distribution and correlation with 24-hour Holter monitoring, autonomic function, and mechanical abnormalities.
Main Results:
- QT dispersion was significantly increased in LVH and tended to increase in CHF.
- QT distribution was abnormal in both LVH and CHF groups.
- No significant correlation was found between QT dispersion and ventricular arrhythmias, autonomic, or mechanical abnormalities.
Conclusions:
- Despite abnormal QT dispersion and distribution in LVH and CHF, these findings do not support QT dispersion as a predictor of arrhythmic risk in these conditions.
- The relationship between QT dispersion and QRS duration warrants further investigation.
Objective:
To study QT dispersion in left ventricular hypertrophy and chronic heart failure and to determine the relation to ventricular arrhythmias.
Setting:
Investigational laboratory of a tertiary referral centre.
Study Design:
Patients with left ventricular hypertrophy and normal systolic function (n = 14) and patients with chronic heart failure (n = 18) were matched with controls (n = 17). The QT dispersion was examined in relation to abnormalities in resting mechanical and autonomic function and to the findings of 24 hour Holter monitoring.
Main Outcome Measures:
QT dispersion is the difference between the maximum and the minimum QT values from the 12 lead electrocardiogram. Mean(SD) QT dispersion from the 10 lead electrocardiogram was also examined once the 12 lead minimum and maximum values had been removed. The QT distribution is the curve describing the distance from the mean for all QT intervals (ms).
Results:
All measures of QT dispersion were increased significantly in left ventricular hypertrophy and tended to increase in those with heart failure. The QT distribution was abnormal in both heart failure and left ventricular hypertrophy. There was no relation between the degree of change in QT dispersion and the incidence of ventricular arrhythmia on 24 hour Holter monitoring. Also there was no relation between QT dispersion and autonomic or mechanical abnormalities. The QT dispersion was related to QRS duration.
Conclusion:
Though QT dispersion and distribution are abnormal in left ventricular hypertrophy these findings do not support the hypothesis that QT dispersion reflects arrhythmic risk in either hypertrophy or heart failure.