Right-sided congestive heart failure (R-CHF) secondary to right-sided heart or pericardial diseases is characterized by increased right atrial, systemic venous and capillary pressures. Direct right atrial pressure measurements are considered the gold standard for identifying R-CHF, but are invasive. In human medicine, sonographically identifying a distended, non-compliant caudal vena cava (CVC) is a non-invasive means of detecting R-CHF and/or estimating intravascular volume. Sonographic CVC dimensions in healthy dogs have been reported. However, the effect of R-CHF on CVC dimensions is not well described. The objective of this study was to determine if CVC measurements, obtained via three different sonographic views, from dogs with R-CHF are outside reference intervals (RI).

Dogs presenting with right-sided heart disease and ascites were prospectively evaluated. Via longitudinal subxiphoid views (SV), maximal and minimal CVC diameter (SV-CVCMax, expiration, SV-CVCMin, inspiration) and collapsibility index (CI) were measured. Transverse 11–13th right hepatic intercostal views (HV) were used to measure maximal and minimal CVC (HV-CVCMax, HV-CVCMin) and aortic diameter. A single CVC and aortic diameter (PV-CVC, PV-Ao) were measured via longitudinal right paralumbar views (PV). CVC dimensions were adjusted for the three views using allometric scaling as well as indexed to aortic diameter for HV and PV. Data were compared to a RI previously established by the authors using 126 healthy dogs of various breeds. Data were expressed as median and range.

Six dogs weighing 19,2 kg (7,2 – 33,9), were included. Diagnosis included pulmonary hypertension (n=3), congenital heart disease (n=2) and pericardial effusion (n=1). Six out of 6 and 5/6 dogs had SV-CVCMax and SV-CVCMin above RI, respectively. All dogs had CI (19% (7–24) within RI. HV-CVCMax and HV-CVCMin were above RI in 5/6 and 4/6 dogs, respectively. Two out of 6 HV-CVCMax/Ao and HV-CVCMin/Ao ratios were above RI. The PV-CVC/Ao ratio was 1,28 (1,13–1,47), and above RI in 4 dogs. The PV-CVC diameter, using allometric scaling, was above RI in one dog.

This pilot study suggests that an enlarged CVC is observed in dogs with evidence of R-CHF. CVC distension may be easiest to identify at the SV. This could be due to the proximity CVC in relation to the right atrium and/or the influence of the respiratory cycle on the CVC diameter between healthy dogs and dogs with R-CHF when measured at the SV. In contrast to human medicine, there was no difference in CI between dogs with R-CHF and healthy dogs. A larger study is needed to confirm these findings.

Disclosures

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