The Diagnostic Accuracy of Radiographic Cardiac Indices in the Assessment of Cardiomegaly and Left Atrial Enlargement in Rats With Dilated Cardiomyopathy: An Experimental Study

The purpose of this study was to determine the diagnostic value of the vertebral heart score (VHS), radiographic left atrial dimension (RLAD), and vertebral left atrial size (VLAS) in the radiographic evaluation of doxorubicin-induced dilated cardiomyopathy (DCM) in rats. The animals were allocated into two experimental groups, a DCM group (n=100), which received weekly injections of doxorubicin (2 mg/kg per dose intraperitoneally [ip]) over nine weeks, and a control group (n=18) receiving an appropriate volume of 0.9% saline ip. Radiographic cardiac indices (VHS, RLAD, VLAS) were measured two weeks after the final injection, and cardiac morphological parameters (heart weight [HW], heart weight:body weight ratio [HBW], and heart weight:tibial length ratio [HTL]) were determined after sacrifice in all surviving rats (17 control and 54 DCM). Correlations were calculated between the indices and parameters, as well as their sensitivity and specificity in detecting cardiomegaly and left atrial enlargement (LAE) with the three classifiers (HW <= 0.96 g, HBW <= 235, and HTL <= 201). A powerful negative correlation was observed between the indices and parameters (rs >=-0.711, P<0.001). Area under the curve values were 0.989 for RL-VHS, 0.992 for DV-VHS, 0.971 for RLAD, and 0.948 for VLAS. The sensitivity and specificity of these indices in detecting cardiomegaly and LAE at the optimal cut-off values were 94.4% and 100%, respectively, at 8.8 vertebrae (v) for RL-VHS and DV-VHS, 96.3% and 94.1% at 1.4v for RLAD, and 94.4% and 88.2% at 2.1v for VLAS. Radiographic cardiac indices offer an accurate and repeatable method for predicting cardiomegaly and LAE in rats with DCM.