# Breed-Specific Variations in Vertebral Right Heart Index (VRHi): Implications for Detection of True and False Right Heart Enlargement (RHE) in Dogs

## TL;DR

This study shows that some dog breeds naturally have higher heart measurements on X-rays, which can lead to misdiagnosis of heart enlargement if breed-specific factors are not considered.

## Contribution

The study introduces breed-specific cutoff values for VRHi to improve the accuracy of diagnosing right heart enlargement in dogs.

## Key findings

- Brachycephalic breeds like Schnauzers and Pomeranians have higher VRHi values without true heart enlargement.
- Right lateral radiographs are more reliable than ventrodorsal views for VRHi measurements.
- Breed-specific diagnostic cutoffs for VRHi were established to reduce misdiagnosis in veterinary cardiology.

## Abstract

This study explored breed-specific differences in vertebral right heart index (VRHi) values and their accuracy in diagnosing right heart enlargement (RHE) in dogs. Certain breeds, particularly brachycephalic dogs, often exhibited higher VRHi values despite having a normal heart size. Right lateral thoracic radiographs were more reliable for VRHi measurements than ventrodorsal views. These results emphasize the importance of accounting for breed-specific factors when interpreting chest X-rays to assess heart size in veterinary practice.

This study investigated breed-specific variations in vertebral right heart index (VRHi) values and their diagnostic accuracy in detecting right heart enlargement (RHE) in dogs. A total of 359 dogs from various breeds, including brachycephalic and non-brachycephalic groups, were evaluated using radiographic and echocardiographic methods. The VRHi was measured from lateral (RL) and ventrodorsal (VD) thoracic radiographs. Certain breeds, such as brachycephalic dogs, Schnauzers, Dachshunds, Pomeranians, Yorkshire Terriers, and Miniature Pinschers, demonstrated significantly higher VRHi values than non-brachycephalic breeds, even without true RHE. The RL VRHi showed stronger clinical relevance than the VD VRHi, correlating better with the echocardiographic findings. Breed-specific diagnostic cutoff values were established: RL VRHi ≥ 3.45 vertebral units (v) (sensitivity: 75%, specificity: 75%) and VD VRHi ≥ 2.75 v (sensitivity: 72%, specificity: 72%) for brachycephalic breeds and RL VRHi ≥ 3.25 v (sensitivity: 78%, specificity: 80%), VD VRHi ≥ 2.4 v (sensitivity: 61%, specificity: 61%) for non-brachycephalic breeds not belonging to the aforementioned categories. Body weight and chest conformation showed no significant association with VRHi values. These findings highlight the necessity of considering breed-specific factors in radiographic cardiac evaluations, as some breeds may present radiographic signs of RHE despite a normal cardiac anatomy and function.