The heart-to-single vertebra ratio measured at the sixth thoracic vertebra (HSVRT6) is a recently described radiographic index developed to simplify the assessment of cardiac silhouette size in cats. This prospective method-comparison study evaluated the diagnostic performance of HSVRT6 in feline hypertrophic cardiomyopathy (HCM), compared it with vertebral heart score (VHS), and assessed the ability of both measurements to differentiate ACVIM stages. A total of 124 cats were included: 48 control cats and 76 cats with HCM classified as ACVIM B1 (n=23), B2 (n=23), or C (n=30). Right lateral thoracic radiographs and echocardiographic examinations were obtained, and HSVRT6 and VHS were calculated. HSVRT6 values were lower in control cats than in all HCM groups and showed a progressive numerical increase across ACVIM stages (control: 7.35±0.70; B1: 8.07±0.70; B2: 8.51±0.96; C: 8.72±0.87). HSVRT6 was strongly correlated with VHS (r=0.835, P<0.001). For differentiating cats with HCM from control cats, HSVRT6 yielded an AUC of 0.803, with 88.9% sensitivity and 58.8% specificity, whereas VHS yielded an AUC of 0.752, with 75.6% sensitivity and 67.6% specificity. HSVRT6 showed particularly high sensitivity for distinguishing control cats from ACVIM B1 cats, while neither HSVRT6 nor VHS reliably discriminated against adjacent ACVIM stages. Overall, HSVRT6 appears to be a useful radiographic screening aid for cats suspected of having HCM, particularly when deciding whether echocardiography is warranted. However, its limited specificity and poor discrimination between adjacent stages indicate that echocardiography remains necessary for definitive diagnosis and staging.

To Cite This Article: Ozcan U, Kurt YT, Guder BE, Kot ZN and Dalgin D, 2026. Diagnostic value of heart to single vertebra ratio-T6 in feline hypertrophic cardiomyopathy: comparison with vertebral heart score. Pak Vet J, 46(8): 2147-2157. http://dx.doi.org/10.29261/pakvetj/2026.180