Focused ultrasound of the caudal vena cava in dogs with cavitary effusions or congestive heart failure: A prospective, observational study

Abstract

Introduction: Ultrasonographic indices of the inferior vena cava are useful for predicting right heart filling pressures in people.

Objectives: To determine whether ultrasonographic indices of caudal vena cava (CVC) differ between dogs with right-sided CHF (R-CHF), left-sided CHF (L-CHF), and noncardiac causes of cavitary effusion (NC).

Materials and methods: 113 dogs diagnosed with R-CHF (n = 51), L-CHF (30), or NC effusion (32) were enrolled. Seventeen of the R-CHF dogs had pericardial effusion and tamponade. Focused ultrasound was performed prospectively to obtain 2-dimensional and M-mode subxiphoid measures of CVC maximal and minimal size (CVCmax and CVCmin), CVCmax indexed to aortic dimension (CVC:Ao), and CVC collapsibility index (CVC-CI). Variables were compared between study groups using Kruskal-Wallis and Dunn's-Bonferroni testing, and receiver operating characteristics curves were used to assess sensitivity and specificity.

Results: All sonographic CVC indices were significantly different between R-CHF and NC dogs (P < 0.001). Variables demonstrating the highest diagnostic accuracy for discriminating R-CHF versus NC were CVC-CI <33% in 2D (91% sensitive and 96% specific) and presence of hepatic venous distension (84% sensitive and 90% specific). L-CHF dogs had higher CVC:Ao and lower CVC-CI compared to NC dogs (P = 0.016 and P = 0.043 in 2D, respectively) but increased CVC-CI compared to the R-CHF group (P < 0.001).

Conclusions: Ultrasonographic indices of CVC size and collapsibility differed between dogs with R-CHF compared to NC causes of cavitary effusions. Dogs with L-CHF have CVC measurements intermediate between R-CHF and NC dogs.

Fig 1. Selected ultrasound indices by study group.

Box and whisker plots of data of select ultrasound indices obtained from 113 dogs with cavitary effusion or pulmonary edema diagnosed with either right-sided congestive heart failure (R-CHF, n = 51, including 17 dogs with pericardial effusion and tamponade), left-sided congestive heart failure (L-CHF, n = 30), or noncardiac causes of cavitary effusion (NC, n = 32). A, caudal vena cava collapsibility index (CVC-CI) in 2D; B, caudal vena cava collapsibility index in M-mode; C, maximum caudal vena cava to aorta ratio (CVC:Ao) in 2D; D, maximum caudal vena cava to aorta ratio (CVC:Ao) in M-mode; E, ratio of right ventricular to left ventricular dimension (RV:LV) in long axis. Boxes represent the interquartile range while the horizontal line in each box represents the group median; whiskers represent the 5th and 95th percentiles, and the outliers are plotted as dots.

Fig 2. Representative focused ultrasound images.

Representative images of caudal vena cava (CVC) sonographic indices taken from subxiphoid views in a patient with right-sided congestive heart failure (A, C, E, G) and a patient with noncardiac cause of cavitary effusion (B, D, F, H). A, B: Still 2-dimensional (2D) ultrasound images showing maximal sagittal diameter of the CVC (CVC_max) as it crosses the diaphragm. C, D: Still 2D ultrasound images showing minimal sagittal diameter of the CVC (CVC_min) as it crosses the diaphragm. E, F: M-mode image from a subxiphoid view showing CVC_max and CVC_min within a spontaneous respiratory cycle. G, H: Still 2D ultrasound images showing presence (G) and absence (H) of hepatic venous distension.