Radiographic measurement of vertebral heart size in pregnant cats and cats with uterine diseases

An abstract of the research paper presented to the Faculty of Veterinary Medicine, Universiti Malaysia Kelantan, in partial requirement of the course DVT 55204 – Research Project.
The Vertebral Heart Size (VHS) is a critical, standardized radiographic tool for detecting cardiomegaly in small animals. The established VHS range (6.7–8.1 V) for healthy cats may not adequately represent the physiological cardiac adaptations during pregnancy or pathological conditions of the uterus. This study aimed to determine the mean VHS in pregnant cats and cats with uterine diseases. By comparing these values to the published normal reference range, we can enhance diagnostic accuracy for these specific patients. A retrospective cross-sectional study was conducted using medical records and lateral thoracic radiographs from a total of 75 female cats (n=52 pregnant, n=23 with uterine diseases) from the year of 2020 to 2024. VHS was measured according to the standard of the Lister and Buchanan method (2000). Statistical analysis revealed a highly significant increase in VHS in both groups compared to the normal mean of 7.5 V (p < 0.001 for both). Pregnant cats exhibited a mean VHS of 8.4 ± 0.5 V, with a range of 8.2 V to 8.5 V. Cats with uterine diseases (including pyometra, fetal death, and endometrial hyperplasia) showed an estimated median VHS of 8.0 V (95% CI: 7.8–8.2 V). The difference in VHS between the pregnant cats and cats with uterine diseases was not statistically significant (p = 0.085). The findings suggest that pregnancy-induced hemodynamic changes, such as increased cardiac output and cardiac hypertrophy, lead to an increase in VHS. Similarly, the elevation in VHS in cats with uterine diseases is likely caused by the systemic inflammatory responses (e.g., SIRS/sepsis in pyometra animals). This study shows that the conventional feline VHS reference range should be used with care for pregnant queens and cats with uterine pathology. A VHS of up to 8.5 V should be considered within the normal physiological range for pregnant cats, supporting more accurate radiographic interpretation in clinical practice.