Vertebral Heart Score in Rhesus Macaques (Macaca mulatta): Generating Normal Reference Intervals and Assessing its Validity for Identifying Cardiac Disease.

Vertebral heart scoring (VHS) is a semiquantitative method to assess the presence and severity of cardiomegaly by using thoracic radiographs. VHS in rhesus macaques (Macaca mulatta) has not been validated or used routinely in the clinical or research setting. We hypothesized that rhesus macaques with cardiac disease diagnosed by using echocardiography would have higher VHS than animals without cardiac disease. A total of 150 rhesus macaques were enrolled in this study. All animals underwent echocardiography and thoracic radiography (right lateral [RL], dorsoventral [DV], and ventrodorsal [VD] views).According to echocardiography, 121 rhesus macaques had no cardiac disease and were used to establish reference intervals for VHS. The remaining 29 macaques had hypertrophic cardiomyopathy (n = 20) or other cardiac disease (n = 9). Results showed that VHS of RL and VD views were significantly higher in macaques with any of the identified cardiac diseases and in the cardiac disease group that excluded hypertrophic cardiomyopathy. VHS of animals with HCM was not significantly different than that of control animals. In the RL view, VHS was moderately accurate for predicting the presence of cardiac disease, with an AUC of 0.71 and an optimal cut-off value of 10.25 (sensitivity: 62%, specificity: 77%). In the VD view, VHS was a mildly accurate test for cardiac disease, with an AUC of 0.654 and an optimal cut-off value of 10.65 (sensitivity, 66%;specificity, 63%). Study results indicated that VHS could be a useful screening tool for clinically identifying rhesus macaques with cardiac disease. However, VHS is unlikely to replace echocardiographic examination for determining the presence, type,and severity of cardiac disease in this species.