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

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 predictor in patients at risk for recurrent, sustained ventricular tachyarrhythmias ( ). 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). Methods: 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). Arrhythmi 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. Results: 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 multivariate model. Thus, excessive dispersion of repolarization is 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).