The determination of the heart size in 100 clinically thorax-disease-free pet rabbits (Oryctolagus cuniculus forma domestica) using the Vertebral Heart Score (VHS).

Abstract

Objective: To establish reference values for the Vertebral Heart Score (VHS) in pet rabbits that are clinically free of thorax disease.

Materials and methods: Radiographs of 100 pet rabbits without clinical or radiographic signs of thoracic disease were analyzed. The long and short axes of the heart were determined in lateral and ventrodorsal projections using Buchanan's method. These distances were then applied to the thoracic spine, starting from the cranial border of the fourth vertebra, to determine the size of the heart in vertebral lengths. Additionally, the angle between the sternum and the longitudinal axis of the heart was determined in the lateral view.

Results: A total of 54 male (14 intact and 40 neutered) and 46 female (29 intact and 17 neutered) rabbits, median age 4.75 years (range 6 months-11 years), were included in the study. The median long-axis dimension was 4.5 vertebrae (2.5-97.5% percentiles: 3.75-5.00 vertebrae) in the lateral projection, and 4.0 (3.25-5.00) vertebrae in the ventrodorsal projection. The short-axis dimension was 3.25 (3.00-4.00) vertebrae for the lateral and 3.25 (2.50-4.00) vertebrae for the ventrodorsal projection. The median vertebral heart score (VHS) was 7.75 (6.75-8.75) in the lateral projection and 7.25 (6.0-9.0) in the ventrodorsal projection. The median VHS was higher for male rabbits (8.0) than for female rabbits (7.5) in the lateral projection. Age and weight had no significant influence. The median angle between the sternum and the long axis in lateral projections was 50.4° (2.5 to 97.5% percentile: 42.81-61.60).

Conclusion and clinical relevance: This study presents reference ranges for the VHS in pet rabbits that can be used to objectively assess the heart size.