Two-dimensional speckle tracking echocardiography in evaluating radiation-induced heart damage

Radiation-induced heart damage (RIHD) in malignant tumor patients with thoracic radiotherapy has been well documented. However, there is no study on the cardiac toxicity of stereotactic body radiotherapy (SBRT) based on two-dimensional speckle tracking echocardiography (2D STE). In a prospective cohort trial, 48 patients with malignant tumor (including patients with lung cancer, pulmonary metastases and other tumor) were assigned to receive thoracic SBRT. Circulating biomarkers, electrocardiogram (ECG), echocardiography, and 2D STE were performed prior to and within 2 months after thoracic radiotherapy. The primary outcome of the trial was a decrease in global longitudinal strain (GLS)≥10%. The secondary outcomes were major adverse cardiovascular events (MACE). Analysis were conducted using paired sample t-test, Wilcoxon signed rank test and Chi square test. The morbidity of RIHD is 44% within 2 months after SBRT in malignant tumor patients. Compared with pre-RT, a significant decrease in GLS was observed post-RT (-17.98±3.54% vs -16.92±3.41%; P=0.008), without any significant change in left ventricular ejection fraction(LVEF)( 68.54±6.06 vs. 69.63±4.45; P=0.234), left ventricular mass(LVM) (P=0.342), ECG parameters, creatine kinase(P=0.074), cardiac troponin T(P=0.829) or N-terminal pro-B-type natriuretic peptide(P=0.453) at during the post-RT period. There was no evidence that RIHD was correlated with age(P=1.000), mean heart dose (P=0.602), BED (P=0.234), EQD2/2 (P=0.615), V5 (P=0.506), V10 (P=0.578), V20 (P=0.670) and V30 (P=0.741). Subgroup analysis showed, there is still a significant decline of GLS (-18.30±3.79% vs -17.11±3.58%; P=0.018) in patients without anthracycline treatment. And the decrease of GLS (-19.14±2.42% vs -16.85±2.46%; P=0.004) was more significantly post-RT in anthracycline treatment group. MACE were found in one patient over a period of 2 months after SBRT. By using strain analysis subclinical cardiac dysfunction was found to be evident early after SBRT, despite unchanged conventional indices such as LVEF, ECG parameters or circulating biomarkers. And the decrease of GLS is still existed after the effect of anthracycline was removed.