Effect of Off-target Low Dose Radiation on Myocardial Contractile Function-An Animal Study

非治療標地低劑量之放射線照射對心肌收縮功能之影響－動物研究

張文馨(Wen-Hsin Chang) ； 謝忱希(Chen-Hsi Hsieh) ； 陳裕仁(Yu-Jen Chen) ； 王儷穎(Li-Ying Wang)

《物理治療》 42卷4期 (2017/12) Pp. 339-340

https://doi.org/10.6215/FJPT.2017.74.P05

摘要

Background and Purpose: Radiation therapy is one of the most common treatments for patients with thoracic cancer. During mediastinal radiation, heart is often included in the irradiation field and all components of the heart and pericardium are susceptible to radiation related oxidative stress damage. However, it remains unclear whether irradiation would affect myocardial contractile function. The purpose of this study was to investigate the effect of off-target low dose on myocardial contractile function using animal model. Methods: A total of 6 adult male Wistar rats (290–348 g) were used and randomized into radiation (RG, n = 10) and control group (CG, n = 10). After anesthetized, rats in RG and CG received 2 Gy/fraction and 0 Gy/ fraction/day irradiation for 5 days, respectively. Twenty-four hours following irradiation, myocardial contractile function was examined using in vivo pressure-volume (P-V) analysis. Load independent diastolic indexes and systolic indexes were evaluated. Results: Twenty-four hours after receiving 5-day course of irradiation, heart rate and end-systolic pressure (ESP) were significantly decreased, and end-systolic volume (ESV) was significantly increased in RG compared to that of control group (CG: 14.4 uL vs. RG: 53.2 uL, p = 0.001). Compare to CG, ejection fraction (systolic index) decreased significantly in RG after irradiation challenge radiation group (CG: 84.3% vs. RG: 51.1%, p ＜ 0.001). The relaxation time constant Tau (diastolic index), increased significantly after irradiation challenge (CG: 12.2 ms vs. RG: 16.2 ms, p = 0.07). Conclusion: The results showed that off-target low dose irradiation could induce both systolic and diastolic dysfunction of the myocardium. Clinical Relevance: Whether preconditioning of heart through exercise training could ameliorate cardiac dysfunction after irradiation warrants further investigation.