Purpose: Although spinal irradiation used in the treatment of CNS malignancies includes a portion of the heart in the radiation field, cardiac effects have not been previously reported.
Patients and methods: We compared patients treated for malignancy in childhood with spinal irradiation (n = 26) with patients treated with mediastinal/flank irradiation (n = 47) that included the heart in the radiation field. All patients were more than 1 year from completion of radiation therapy. Patients underwent at least two of the following cardiac evaluations: (1) ECG; (2) 24-hour ambulatory ECG; (3) echocardiogram; and (4) exercise-testing using cycle ergometry.
Results: Twelve of 16 patients (75%) in the spinal irradiation group with an assessable exercise test achieved a maximal cardiac index (MCI) below the fifth percentile as compared with 13 of 40 patients (32%) who had received mediastinal/flank irradiation (P = .007). Furthermore, after adjusting for normal heart growth, radiation and anthracycline doses, and follow-up time, the group of patients who received spinal irradiation had significantly higher estimated posterior wall stress (P = .002), expressed as the natural logarithm of the ratio of end-diastolic left ventricular internal diameter (LVID) to left ventricular posterior wall thickness (LVPWT), than the group who had received mediastinal/flank irradiation. Finally, eight of 26 patients (31%) in the spinal group had pathologic Q-waves in the inferior leads versus three of 47 (6.4%) in the mediastinal/flank group (P = .001).
Conclusion: Patients who have received spinal irradiation for pediatric malignancies appear to be at risk for significant cardiac dysfunction. The asymmetric distribution of radiation to a growing heart, as given with spinal irradiation, may be the cause of these findings.