# Assessment of Pulmonary Vein Diameters in Cavalier King Charles Spaniels with Myxomatous Mitral Valve Disease

## TL;DR

This study shows that measuring the diameter of a specific pulmonary vein can help assess the severity of heart disease in Cavalier King Charles Spaniels.

## Contribution

The study identifies pulmonary vein 2 (PV2) diameter as a reproducible and disease-stage-sensitive echocardiographic parameter in dogs with myxomatous mitral valve disease.

## Key findings

- PV2 diameter increases with disease progression and is less influenced by body weight compared to other pulmonary veins.
- A PV2 cut-off of 12.8 mm distinguishes stage C from stage B2 with 93% specificity but only 57% sensitivity.
- PV2 diameter correlates with multiple echocardiographic indices of cardiac remodeling and pressure overload.

## Abstract

This study examined whether the size of the pulmonary veins could help assess heart disease severity in Cavalier King Charles Spaniels (CKCSs) with myxomatous mitral valve disease (MMVD). Healthy dogs were compared to those at different stages of the disease using ultrasound measurements. The pulmonary vein 2 (PV2) diameter was found to be the least affected by body weight and increased as the disease progressed. The PV2 diameter showed positive correlations with several echocardiographic indices of cardiac remodeling. A PV2 cut-off value of 12.8 mm yielded a sensitivity of 57% and a specificity of 93% for distinguishing stage C from stage B2. PV2 measurements could be used as an additional, not standalone, tool for staging and treatment decisions and may offer additional insights into cardiac disease progression.

The present study aimed to compare pulmonary vein (PV) diameters between Cavalier King Charles Spaniels (CKCSs) with myxomatous mitral valve disease (MMVD) and healthy CKCSs, assess correlations between PV diameters and echocardiographic parameters, and identify the optimal PV diameter cut-off value that distinguishes stage C from stage B2. CKCSs were recruited both retrospectively and prospectively and classified according to the ACVIM guidelines (stages A, B1, B2, and C). From a left apical view, the diameters of three PVs (PV1, PV2, and PV3) were measured with high reproducibility. In healthy dogs, the PV2 diameter showed no correlation with body weight. The PV2 diameter was significantly higher in stage B2 compared to B1 and in stage C compared to B2, while no difference was found between stages A and B1. The median (IQR) PV2 diameters were 4.9 mm (3.9–5.2) in stage A, 5.1 mm (4.0–6.0) in stage B1, 9.3 mm (7.3–11.1) in stage B2, and 13.7 mm (9.9–15.1) in stage C. Positive correlations were observed between the PV2 diameter and the left ventricular internal diameter normalized for body weight, the left atrium-to-aorta ratio, mitral E wave peak velocity, tricuspid regurgitation pressure gradient, and regurgitant fraction. A PV2 diameter cut-off value of 12.8 mm discriminated stage C from stage B2 with 57% sensitivity and 93% specificity. The PV2 diameter is a reproducible echocardiographic measure that increases with MMVD severity and could assist in the early detection of congestive heart failure. However, the modest sensitivity observed reflects the overlap of PV2 measurements between stages B2 and C. Therefore, PV2 should be interpreted with caution and considered a supportive, rather than exclusive, tool in disease staging and therapeutic decision-making.