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Corrected QT interval prolongation in anthracycline-treated survivors of childhood cancer
C L Schwartz1, W L Hobbie, S Truesdell
1Department of Pediatrics, University of Rochester Medical Center, NY 14642.
Purpose:
Comprehensive cardiac evaluations are currently recommended for all anthracycline-treated patients to detect subclinical cardiac failure. A screening test is needed that would easily and inexpensively identify patients who are at risk for late cardiac decompensation.
Methods:
We routinely reviewed the ECG and echocardiogram (ECHO) results of 52 of 56 anthracycline-treated long-term survivors of childhood cancer who had received > or = 100 mg/m2 of ANTH (ANTH = 1 mg/m2 of doxorubicin), and who were not in clinical heart failure. Exercise testing was performed in eight patients with a corrected QT interval (QTc) of > or = 0.43.
Results:
Zero of 15 patients (without chest radiation) who received less than 300 mg/m2 of ANTH versus six of 22 who received > or = 300 mg/m2 of ANTH had a QTc > or = 0.43 (P = .03). Three of 15 patients (with chest radiation) who received less than 300 mg/m2 of ANTH versus 12 of 22 who received > or = 300 mg/m2 of ANTH had a QTc > or = 0.43 (P = .03). For all patients (including those with chest radiotherapy), zero of 19 who received less than 300 mg/m2 of ANTH versus eight of 33 who received > or = 300 mg/m2 of ANTH had a QTc of > or = 0.45 (P = .025). Three of 19 who received less than 300 mg/m2 of ANTH versus 19 of 33 who received > or = 300 mg/m2 of ANTH had a QTc of > or = 0.43 (P = .003). One patient had decreased fractional shortening (FS) and QTc prolongation. Cardiac decompensation (with a FS of 24%) occurred with propranolol in a patient with previously normal FS but prolonged QTc. With exercise, the QTc became further prolonged in all four patients with a QTc of 0.44 to 0.46 and in two of four patients with a QTc of 0.43.
Conclusion:
Prolongation of the QTc, a measure of myocardial repolarization, may reflect injury to myocardial cells. QTc prolongation may be predictive of an increased risk of late cardiac decompensation. If the utility of the QTc measure is confirmed, screening for evidence of myocardial damage can be easily and inexpensively performed by oncologists and primary caretakers.