Background: QT dispersion is prolonged in numerous cardiac diseases, representing a general repolarization abnormality.
Aim: To evaluate the influence of viable myocardium on QT dispersion in patients with severely depressed left ventricular (LV) function due to coronary artery disease.
Methods and results: 103 patients with ischemic cardiomyopathy (LV ejection fraction [EF]: 25+/-6%) were studied. Patients underwent 12-lead electrocardiography to assess QT dispersion, and two-dimensional echocardiography to identify segmental dysfunction. Dobutamine stress echocardiography (DSE) was then performed to detect residual viability. Resting echo demonstrated 1260 dysfunctional segments; of these, 476 (38%) were viable. Substantial viability (> or =4 viable segments on DSE) was found in 62 (60%) patients. QT dispersion was lower in these patients, than in patients without viability (55+/-17 ms vs. 65+/-22 ms, P=0.012). Viable segments negatively correlated to QT dispersion (r=-0.333, P=0.001). In contrast, there was no correlation between LVEF and QT dispersion (r=-0.001, P=NS).
Conclusions: There is a negative correlation between QT dispersion and the number of viable segments assessed by DSE. Patients with severely depressed LV function and a low QT dispersion probably have a substantial amount of viable tissue. Conversely, when QT dispersion is high, the likelihood of substantial viability is reduced.