2370 - Arrythmias in Patients Receiving Thoracic Radiation
Presenter(s)
H. E. Grace1, S. K. Montalvo1, A. Bennett2, J. S. Buatti1, N. Kalakuntla3, K. D. Westover1, Y. Zhang4, N. Munshi2, J. Dianels2, V. Zaha2, M. S. Link2, and P. G. Alluri1; 1Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, 2Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, 3UT Southwestern Medical Center, Dallas, TX, 4Department of Radiation Oncology, UT Southwestern Medical Center, Dallas, TX
Purpose/Objective(s): Patients receiving thoracic radiation (RT) are at increased risk for cardiac morbidity and mortality from radiation-induced cardiotoxicity. This study aims to establish the incidence of cardiac arrhythmias before and after thoracic radiation, and to define dosimetric characteristics of the cardiac substructures related to the conduction system and arrhythmia outcomes in patients treated with thoracic RT.
Materials/Methods: We retrospectively analyzed single institution data from patients treated with thoracic RT between 2006-2020 who had electrocardiograms (ECGs) recorded both before and after RT. Formal ECG reads from electronic medical records were categorized into the following abnormalities: abnormal rates, supraventricular arrhythmias (SVA), ventricular arrhythmias, atrioventricular (AV) conduction abnormalities, aberrant conduction, chamber sizes/axis/voltage abnormalities, and ischemic/infarction changes. Cardiac substructures, including sinoatrial (SA) node, AV node, left pulmonary vein (PV) and right PV were manually contoured for patients with available treatment planning data. Pairwise odds ratios were calculated using the McNemar test before and after RT, and groups were assessed using the chi squared test. Kaplan-Meier estimates were used to evaluate the incidence of atrial fibrillation (AF).
Results: A total of 3328 ECGs corresponding with 360 individual patients were identified. The predominant primary malignancy was of lung origin (91.1%) and the remainder esophageal (8.9%). The median age at treatment was 69 (range: 34-93) and 55% were male. Patients underwent IMRT (50.83%), 3D RT (24.58%), SBRT (23.95%), or HDR brachytherapy (0.62%). Among the various arrhythmias, the prevalence of SVA increased significantly from 14.2% pre-RT to 22.8% post-RT (OR 2.35, 1.417-4.008, p < 0.001). Among SVAs, prevalence of AF significantly increased from 11.94% pre-RT to 18.33% post-RT (OR 2.045, 1.203-3.577, p < 0.007). Prevalence of supraventricular tachycardia significantly increased from 0.83% pre-RT to 3.05% post-RT (OR 5, 1.066-46.933, p<0.039). Among 54 patients with normal baseline ECG who developed new SVAs, 48% (26/54) had evaluable dosimetry. In these patients, the median maximum dose to the SA node was 13.15 Gy (IQR 20.74), AV node was 10.74 Gy (IQR 27.72), left PV was 40.37 (IQR 43.29) Gy, and right PV was 32.61 Gy (IQR 44.85). The median mean dose to the SA node was 8.68 Gy (IQR 13.17), AV node was 6.30 Gy (IQR 21.00), left PV was 22.27 Gy (IQR 39.83), and right PV was 15.76 Gy (IQR 29.82).
Conclusion: ECG abnormalities were common in this single institutional cohort of patients receiving standard-of-care thoracic RT. SVAs increased significantly after RT. Given the high incidence of arrhythmias, ECG evaluations at baseline and after thoracic RT may be warranted. These data suggest that further studies are needed to identify cardiac substructure dose metrics and develop mitigation strategies for arrhythmias.