Previous studies showed that increased QT dispersion has been observed during episodes of myocardial ischemia or infarction and identified the patients at risk of arrhythmia or sudden death. The aim of this study was to investigate the relation between QT dispersion and left ventricular (LV) function (systolic and diastolic), dimension and mass as well as to analyze the differences of this relationship according to the extent of angiographic coronary stenosis in patients with coronary artery disease.

The study population included 262 patients (male 129, female 133;average age 60 years). Echocardiography was done for the measurement of left ventricular function, dimension and mass on admission. Electrocardiography for QT and QTc (corrected QT) dispersion were recorded 25 mm/sec paper speeds before the coronary angiography. Patients were divided into two groups; Group A where angiographic coronary stenosis <50%, and Group B where angiographic coronary stenosis >or =50%.

The results were as follows: 1) QT dispersion was higher in those with depressed LV systolic function (EF<55%) than in those with normal LV systolic function among Group A (p<0.05). 2) QT dispersion was higher in those with abnormal IVRT (isovolumic relaxation time) than in those with normal IVRT among Group A (p<0.05). But, there was no correlation between QT dispersion and other diastolic parameters in Group A. 3) QT dispersion was positively correlated with increased LVDd (diastolic left ventricular dimension), LVDs (systolic left ventricular dimension), LAD (left atrial dimension) and IVS (interventricular septum) in those in Group A. But, there found no correlation between QT dispersion and LV dimension parameters in Group B. 4) QT dispersion also had a positive correlation with LV mass in all patients and in those in Group A (all patients p<0.01;Group A p<0.001). But, there found no correlation between QT dispersion and LV mass in Group B. 5) On multiple logistic regression analysis, sex, abnormal IVRT and significant stenosis (> or =50%) of the coronary artery were independent prognostic factors of prolonged QT dispersion (p<0.05). 6) QTc dispersion showed the same result as QT dispersion.

LV systolic function (EF), some diastolic function (IVRT), dimension (LVDd, LVDs, LAD IVS), and mass are associated with the increased QT dispersion in patients with coronary artery disease, especially minimal angiographic stenosed (<50%) patients. So, we consider echocardiography is an important tool to predict the QT dispersion in patients with coronary artery disease.