Signal-averaged ECG in patients after anthracycline therapy for childhood cancer.

Late cardiac complications after anthracycline therapy is an increasingly common problem among survivors of childhood cancer. Routine clinical examination may be normal, but subclinical cardiac abnormalities, which may progress with time, are documented in high percentage of these patients. Microstructural myocardial alterations may result in production of micropotential level signals (late potentials, LP) and altered frequency components of signal-averaged ECGs (SAECG). SAECG abnormalities are valuable in risk stratification of patients with various heart diseases culminating in fatal arrhythmias or heart failure. Forty-five pediatric oncologic patients (mean age 14.4 +/- 4.1 years) were included in the study. SAECG was performed 3 months-12 years (median 5.5 years) following completion of anthracycline therapy. The total cumulative doses of anthracyclines were 90-555 (median 230) mg/m2. The control group consisted of 30 healthy age-matched volunteers. LP were present in six (13.3%) patients after anthracycline therapy at 40 Hz high-pass filter setting. Using frequency-domain analysis within the QRS complex, area ratio 1 (area of 20 to 50 Hz/area of 0 to 20 Hz) and area ratio 2 (area of 40 to 100 Hz/area of 0 to 40 Hz) were calculated. Twenty (44.4%) and fourteen (31.1%) had abnormal values in area ratios 1 and 2, respectively, within the QRS complex. Area ratios 1 and 2 of patients after anthracycline therapy were significantly higher than those in control group (p = 0.0187 and p = 0.0043). Our preliminary results suggest that chemotherapy with anthracyclines, even in low dosage, is associated with increased incidence of SAECG abnormalities. The potential of this simple, noninvasive method to detect subclinical anthracycline-induced myocardial alterations and facilitate prognostic stratification of cancer survivors is promising, however, the clinical value of SAECG remains to be established in a larger and a longer study.