Objective:To investigate the value of 24-hour dynamic electrocardiogram combined with cardiac troponin I (cTnI) in evaluating the radiation-induced heart disease (RIHD) in chest tumor radiotherapy.Methods:From 2015 to 2018, 128 patients with chest tumor who received radiation therapy with/without chemotherapy in the Third People′s Hospital of Linyi were selected to undergo routine ECG examination, 24-hour dynamic ECG examination, cTnI and cardiac color Doppler ultrasound before radiotherapy, 30Gy radiotherapy, 50Gy radiotherapy, after radiotherapy and 3 months after radiotherapy, respectively. The detection rates of 24-hour dynamic electrocardiogram, routine electrocardiogram, cTnI, cardiac color Doppler ultrasound and 24-hour dynamic electrocardiogram combined with cTnI for RIHD were statistically compared. The correlation between glucose level, hypertension and coronary heart disease, combined with chemotherapy, radiation dose and the irradiated area of the heart and the incidence of RIHD was analyzed.Results:The detection rates for RIHD did not significantly differ between 24-hour dynamic electrocardiogram and routine electrocardiogram ( P>0.05), whereas the detection rates for arrhythmia, atrioventricular block, bundle branch block and ST-T changes of 24-hour dynamic electrocardiogram were significantly higher than those of routine electrocardiogram (all P<0.05). The detection rate of 24-hour dynamic electrocardiogram combined with cTnI was significantly higher compared with that of 24-hour dynamic electrocardiogram, routine electrocardiogram, cTnI or cardiac color Doppler ultrasound alone (all P<0.05). There was a significant difference in RIHD before and after radiotherapy ( P<0.05). The incidence rate of RIHD in the radiation therapy combined with chemotherapy group was significantly higher than those in the cisplatin chemotherapy and radiotherapy alone groups, especially in the epirubicin+cyclophosphamide group (45%, all P<0.05). The incidence rate of RIHD was similar between radiotherapy alone and radiotherapy combined with cisplatin chemotherapy (both P>0.05). After radiation therapy, the grade of RIHD was elevated in 40 cases (31.2%). Diabetes mellitus, hypertension, coronary heart disease, radiotherapy combined with chemotherapy, cardiac D mean and cardiac V 40Gy were the independent factors for the occurrence of grade 1-4 RIHD (all P<0.05). Conclusion:The 24-hour dynamic electrocardiogram combined with cTnI is of great value in the detection of RIHD induced by radiotherapy for chest tumors with high detection rate, simple operation and low cost, which is worthy of application in clinical practice.