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

Abstract

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.

Keywords: Cavalier King Charles Spaniels; canine; congestive heart failure; myxomatous mitral valve disease; pulmonary vein.

Figure 1

Schematic representation (A) and echocardiographic images of a control dog (B) and a stage C (C) dog from the left parasternal apical view focused on the ostia of the pulmonary veins. PV diameter measurement was performed on 2D echocardiography using the inner edge-to-inner edge method (indicated by the yellow dotted line in panel (A) and yellow double arrows in panels (B,C) at the end of systole, as indicated by the red arrow on the schematic electrocardiogram at the bottom of the image. Three PVs (PV1, PV2, and PV3) were identified, and their diameters were recorded. PV1, pulmonary vein 1; PV2, pulmonary vein 2; PV3, pulmonary vein 3; LA, left atrium; and LV, left ventricle. The V in panels (B,C) corresponds to the probe’s orientation marker.

Figure 2

Boxplots showing pulmonary vein 2 diameters in 92 Cavalier King Charles Spaniels including groups of different stages of myxomatous mitral valve disease according to ACVIM classification (stages B1, B2, and C) and a control group (stage A). The central line within each box represents the median; the length of the box represents the interquartile range (25th–75th percentiles), and the whiskers indicate the 10th and 90th percentiles. Outliers are represented by empty circles.

Figure 3

Significant correlations between pulmonary vein 2 diameter and (A) left ventricular internal diameter in diastole normalized for body weight, (B) ratio of the left atrial dimension to the aortic annulus dimension, and (C) peak velocity of early diastolic transmitral flow in 92 Cavalier King Charles Spaniels with different stages of myxomatous mitral valve disease according to ACVIM classification, including control dogs. PV2, pulmonary vein 2; LVIDDN, Left ventricular internal diameter in diastole normalized for body weight; LA:Ao, ratio of the left atrial dimension to the aortic annulus dimension; E, peak velocity of early diastolic transmitral flow.

Figure 4

Receiver operating characteristic (ROC) curve (solid line) illustrating the performance (sensitivity and specificity) of pulmonary vein 2 optimal cut-off value (corresponding to the point on the ROC curve) for distinguishing stage B2 from B1 ((A): threshold = 6.5 mm) and stage C from B2 ((B): threshold = 12.8 mm) according to ACVIM classification. The dotted lines indicate on each ROC curve the diagnostic performance of the chosen cut-off value.