Background: Anthracycline cytostatics, widely used in oncologic practice, may induce discrete myocardial damage occasionally culminating in life-threatening cardiologic complications. The most serious clinical manifestations of anthracycline cardiotoxicity are dilated cardiomyopathy, heart failure and fatal arrhythmias. OBJECTIVES, STARTING POINT AND MAIN PURPOSE: High-resolution electrocardiography (HRECG) is one of the latest cardiologic methods, which can be promising for early identification of patients at risk of anthracycline cardiotoxicity. The aim of this study is the evaluation of the incidence of HRECG abnormalities in a group of paediatric patients treated with anthracyclines and the usefulness of HRECG for stratification of patients at risk of the clinical cardiotoxicity.
Patients and methods: A set of 60 oncologic paediatric patients treated with anthracyclines was divided into two groups. The first group was formed by 15 patients undergoing evaluation during their anthracycline therapy (median after the last administration of antracyclines was 3.2 days). Their average age at the time of examination was 14.7 +/- 4.1 years. The total cumulative dose of antracyclines was 40-300 mg/m2 (median 150 mg/m2). The second group was formed by 45 patients who were evaluated after completing anthracycline therapy. The interval of time from the last administration of antracycline in this subgroup of patients was 3 months-12 years (median 5.5 years). Their average age at the time of HRECG examination was 14 +/- 4.1 years. The total cumulative dose of anthracyclines was 90-440 mg/m2 (median 230 mg/m2). Six patients of this group (13.3%) were treated also with mediastinal radiotherapy (18-40 Gy). 43 patients (95.5%) of second group were in complete remission, two other patients yielded a progression of their malignancy. 10 patients (22%) were examined by HRECG 2-5 times in app. two-month intervals. The control group was formed by 30 randomly selected healthy children and adolescents with normal ECG. Average age was 15.1 +/- 5.8 years. Using HRECG the time- and frequency-domain characteristics of the ECG signal were analyzed. The time-domain analysis was performed at 40-250 Hz filter. The frequency-domain analysis was performed by fast Fourier transformation (FFT), a 120 ms segment starting 20 ms before the end of the QRS complex was analyzed. The altered frequency content was expressed as the ratio of frequency areas (area ratio, AR) 20-50 Hz/0-20Hz. The average level of noise was 0.56 microV in the first group, 0.62 microV in the second group of patients and 0.68 microV in the control group.
Results: Abnormalities in the time-domain analysis (ventricular late potentials, VLP) were present in 2 (13.3%) of 15 patients during the anthracycline therapy in the first group and in 4 (8.8%) of 45 patients after completing therapy in the second group. No abnormalities in the time-domain analysis were detected in the control group. Using frequency-domain analysis, abnormalities in AR20-50 Hz/0-20 Hz were found in 8 (53.3%) of 15 patients of the first group, and in 11 (24.4%) of 45 patients of the second group. Significant differences were observed in the frequency parameters of the ECG signal in patients of the first group in comparison to the control group (p = 0.0018) and also when comparing the patients of the second group and the control group (p = 0.045).
Conclusion: The HRECG results in time- and frequency-domain analyses indicate to high incidence of HRECG abnormalities in patients examined both during and after the antracycline therapy in comparison to the control group. The prognostic use of the HRECG abnormalities must be established in a larger and longer study. (Fig. 4, Tab. 2, Ref. 43.)