901–46 QT Dispersion Predicts Mortality in Treated Patients with Life-threatening Ventricular Tachyarrhythmias

Abstract

QT dispersion (QTD = QT max – QT min), measured from the 12-lead ECG, reflects regional variations in ventricular repolarization and has been associated with an increased risk of arrhythmic events in some patient (pt) groups, but has not been applied as a predictor in patients at risk for recurrent, sustained ventricular tachyarrhythmias (VT/VF). Thus, we sought to determine the predictive value of QTD in consecutive pts presenting with life threatening ventricular arrhythmias and treated with antiarrhythmic drugs predicted to be effective by electrophysiologic testing (n = 11) or Holter monitoring (n = 18). The study group comprised 29 pts of age 66 ± 13 years with ejection fraction 37 ± 13%; 24 were males, 23 had coronary artery disease; 22 had failed previous antiarrhythmic therapy; treatment was with class I drugs in 16 and class III (sotalol) in 13. Follow-up lasted up to 5.7 years (x ± SD, 2.1 ± 1.7). Arrhythmia recurred in 15 pts; there were 4 arrhythmic and 7 total deaths. Parameters on 12 lead ECG tested for long-term predictive value included QRS, QT. QTc, JT, JTc, QTD, QTcD, JTD, and JTcD. Measurements were made within 1 mo of initiating “effective” antiarrhythmic therapy by an experienced observer using electronic calipers and blinded to clinical course. Only measures of dispersion of recovery were predictors of arrhythmic and total mortality: QTD (p ≤ 0.005, 0.0001), QTcD (p ≤ 0.01, 0.0001), JTD (p ≤ 0.005, 0.0000), and JTcD (p ≥ 0.005, 0.0000). In patients dying vs surviving, QTD was 147 ≤ 42 vs 74 ≤ 34 ms and JTcD, 141 ≤ 33 vs 76 ± 30 ms, respectively. Predictive value was independent of antiarrhythmic therapy (ie, sotalol vS other) in a multivariate model. Thus, excessive dispersion of repolarization is a powerful predictor of arrhythmic and total deaths, despite “effective” drug therapy, in patients with life-threatening ventricular arrhythmias. QTD should be further tested in larger groups of high-risk pts, including the selection of pts for further therapies (eg, defibrillators).