Aim To investigate the relationships between QT dispersion (QTd) and plasma endothelin (ET) levels, insulin-sensitivity, and ventricular arrhythmias in coronary heart disease (CHD). Methods Oral glucose tolerance test was conducted in 27 patients with acute myocardial infarction (AMI), 20 patients with angina pectoris and 20 healthy control subjects (in the fourth week after the onset in AMI patients). Blood samples were analysed for glucose, insulin, C-peptides and ET. Linear and/or stepwise regression analysis were used to assess the correlation between QTd and nine insulin-sensitivity parameters and ET levels. Results In patients, QTd was independently, significantly, positively correlated with ET levels. Nevertheless, fasting glucose was an independent, inversely correlated variable in AMI-recovery-period patients. The first-day ET level and QTd were higher in AMI patients with severe ventricular arrhythmias than without (160.5±23.0 ng/L Vs 119.7±15.2 ng/L,P<0.01 for ET;86±19 ms Vs 69±13 ms,P<0.05 for QTd), and both of them were higher than that in control subjects (44.98±14.74 ng/L,P<0.01). QTd was positively correlated with ET(r=0.94 and 0.84,respectively,P<0.01). Conclusions In CHD, especially in AMI, the increase of plasma ET levels is an important independent factor that causes QTd increasing and might further result in severe ventricular arrhythmias. In the recovery period of AMI, low fasting blood glucose is another independent factor of QTd increase.