QT dispersion is not related to infarct size or inducibility in patients with coronary artery disease and life threatening ventricular arrhythmias

Objective-To relate QT parameters to infarct size and inducibility during e lectrophysiological studies. Design-Analysis of a prospective register. Setting-University hospital. Patients-64 patients with coronary artery disease and documented life threa tening ventricular arrhythmias. Interventions-Measurements of QT-max, QTc-max, and QT dispersion (QT-d) on a simultaneous 12 lead ECG (50 mm/s). Estimation of myocardial infarct size with radionuclide left ventricular ejection fraction (LVEF), echocardiogra phy (left ventricular end diastolic diameter, LVEDD), and a defect score ba sed on a quantitative stress redistribution 201-thallium perfusion study. E lectrophysiological study to assess inducibility. Results-Mean (SD) QT parameters were: QT-max 440 (50) ms, QTc-max 475 (46) ms, and QT-d 47 (20) ms. Mean (SD) estimates of infarct size were: LVEF 34 (13)%, LVEDD 61 (9) mm, and defect score 18 (11). There was no significant correlation between any index of infarct size and QT parameters. QT paramet ers were not significantly different between patients with inducible (n = 5 7) and noninducible arrhythmias (n = 7) (QT-max: 416 (30) v 443 (51) ms, p = 0.18; QTc-max 485 (34) v 473 (47) ms, p = 0.34; QT-d 47 (12) v 47 (21) ms , p = 0.73). Non-inducible patients had a significant lower defect score: 8 (9) v 19 (11), p = 0.02, but comparable LVEF: 38 (12)% v 34 (12)%, p = 0.5 8, and LVEDD: 54 (10) v 61 (8) mm, p = 0.13. Conclusions-QT parameters are not influenced by infarct size and do not pre dict inducibility during electrophysiological study in patients with corona ry artery disease and malignant ventricular arrhythmias. In contrast, the a mount of scar tissue determined by perfusion imaging is strongly correlated with inducibility.