Presence of Prolonged Dispersion of Qt Intervals in Late Survivors of Childhood Anthracycline Therapy

To determine the incidence of abnormal dispersion of QT intervals on an ECG the authors measured these intervals in long-term survivors after anthracycline treatment for childhood malignancies and compared the incidence to the traditional markers, prolonged QT and QTc intervals. Prolonged QT dispersion (QTd) and corrected QT dispersion (QTcd) have been associated with serious arrhythmias and sudden death in many forms of heart disease. The above intervals and shortening fraction (SF) on echocardiogram were determined in 64 late survivors who were 4-22 years post anthracycline therapy. They were divided into 2 groups: group I, 39 patients with normal function with SF >or= 29%, and group II, 15 patients with SF < 29%. An additional 10 patients had died and had SF < 29% at the time of death. They were divided into 2 groups: group III, 5 patients who died with heart failure after a mean of 12 years from of therapy, and group IV, 5 patients who had a sudden cardiac death after a mean of 9 years from end of therapy. In group I patients, the incidence of prolonged QT and QTc intervals was < 6%, whereas that of QTd and QTcd was > 38%. In group II patients, the presence of prolonged QT and QTc intervals was < 16%, whereas that of QTd and QTcd was > 40%. The QTc (p =.01), QTd (p =.02), and QTcd (p =.01) were significantly higher and SF (<.01) significantly lower in group IV compared to those alive (group I and II patients) with no significant difference in age, number of years of follow-up, precordial radiation dose, or anthracycline dose between the two. The combination of QTcd > 110 ms and diminished SF < 29% was found to be associated with sudden death. In summary, the long-term survivors of anthracycline therapy had a high incidence (>38%) of abnormally prolonged QT dispersion intervals, QTd and QTcd, even in those with normal QT and QTc on an ECG and normal shortening fraction on an echocardiogram.