Correlation between dispersion of repolarization (QT dispersion) and ventricular ectopic beat frequency in patients with acute myocardial infarction: a marker for risk of arrhythmogenesis?
BACKGROUND
QT dispersion (QTd) has evoked a lot of interest in recent years as regards the basic concept of dispersion of repolarization, which it is supposed to reflect on a surface ECG, as being a marker or substrate for arrhythmogenesis. QTd has been shown to be high in patients with ventricular fibrillation and tachycardia. But there is still some debate about its possible role as a marker or substrate for arrhythmogenesis. We studied whether it has any correlation with simple benign ventricular ectopic beats (VEB) after acute myocardial infarction.


METHODS
We studied four different dispersion parameters (QTd, QTcd, JTcd, AQTd) on 2 different days after AMI and also obtained a 24-h ambulatory ECG on the 2nd day after admission in 64 out of a total of 90 patients. Patients were divided into five groups based on VEB frequency/h on a 24-h ambulatory ECG.


RESULTS
We found a gradual increase in dispersion parameters across the five groups with increasing frequency of VEB. A significant difference was noticed between group 1 (VEB 0.0-0.9/h) and group V (>30/h) on the day of admission: QTd 88.8+/-28.5 versus 123.3+/-23.4, P<0.02; QTcd 100.5+/-27.6 versus 160.3+/-30.7, P<0.01; JTcd 95.5+/-31.0 versus 160.4+/-30.9, P<0.01; AQTd 29.6+/-8.2 versus 48.6+/-13.7, P<0.01. We also noticed a significant positive correlation between VEB frequency and dispersion parameters on both days.


CONCLUSIONS
We hypothesize that with increasing dispersion of repolarization the chances or the frequency of ventricular arrhythmias increase. Our findings also point to a definite role of QTd as an arrhythmogenic marker or substrate.
Jain
Hitender
H
Mercy Hospital of Philadelphia, Philadelphia, PA 19143, USA. hjainmd@yahoo.com
Avasthi
R
R
D000704:Analysis of Variance; D015716:Electrocardiography, Ambulatory; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000150:complications / Q000503:physiopathology*; D011446:Prospective Studies; D012307:Risk Factors; D014693:Ventricular Fibrillation / Q000209:etiology / Q000503:physiopathology*; D018879:Ventricular Premature Complexes / Q000503:physiopathology*