Abstract 15127: Dobutamine Stress Testing as an Early Diagnostic Tool to Detect Radiation-Induced Heart Disease

• Published in: Circulation (New York, N.Y.) N.Y.), 2016-11, Vol.134 (Suppl_1 Suppl 1), p.A15127-A15127
• Main Authors: Lieblong, Benjamin J, Bhatti, Sabha, Sridharan, Vijayalakshmi, Mulkey, Robin L, Fletcher, Terry W, Boerma, Marjan, Rusch, Nancy J
• Format: Article
• Language: English
• ISSN: 0009-7322; 1524-4539

IntroductionRadiation-induced heart disease (RIHD) is a potentially severe side effect of radiotherapy for intrathoracic and chest wall tumors. There is no recommended approach for early detection of the cardiac abnormalities caused by ionizing radiation to identify patients at risk for cardiac events. Dobutamine stress testing (DST) is widely used as a diagnostic to detect ischemic heart disease, but its value to detect early abnormalities in the irradiated heart is unknown.HypothesisDST may serve as an early diagnostic of RIHD prior to manifestation of delayed, overt disease.MethodsMale Sprague-Dawley rats received X-irradiation localized to the heart via 5 fractions of 0 (Sham), 6, or 9 Gy. DST was performed at pre-irradiation baseline, and at 10, 20, 30, 60, 90 and 180 days post-irradiation by infusing dobutamine intravenously in increasing doses (10 - 50 μg/kg/min) concurrent with ECG recording. Rats were subjected to echocardiography at 90 days post-irradiation and before sacrifice at 180 days to evaluate cardiac function. Blood was drawn to determine cardiac troponin-I (cTn-I) and electrolytes at DST sessions.ResultsRIHD-induced fibrosis and echocardiographic abnormalities presented at 90 days, and were accentuated at 180 days post-irradiation. In contrast, DST resulted in T-wave elevation as early as 10 days in rats receiving 5 fractions of 9 Gy, and as early as 20 days at the 5 fractions of 6 Gy dose. The early DST-induced T-wave elevation in irradiated rats persisted during the 180-day study, whereas other ECG events (P, R and S waves) were unchanged. Sham rats did not exhibit ECG abnormalities during DST. At 60 days post-irradiation, T-wave amplitude and cardiac cTn-I were elevated in irradiated rats. Neither DST nor radiation altered blood potassium or calcium concentrations.ConclusionsOur results indicate that DST unmasks ECG abnormalities in irradiated hearts at early time points preceding RIHD-induced functional and structural abnormalities. Hyperkalemia and hypercalcemia can be excluded as causes of T-wave elevation. Thus, DST should be evaluated further as a potential early diagnostic tool in a standard of care to identify individuals at risk for RIHD.