Pulmonary hypertension (PH) is present in approximately 70–80% of dogs with left-sided congestive heart failure (L-CHF) and contributes to clinical signs and outcome. Anecdotal evidence suggests that PH in cats with L-CHF is much less frequent. However, data on the prevalence of PH in cats with L-CHF is not available. This study addresses the general hypothesis that PH secondary to L-CHF is uncommon in cats and that echocardiographic findings in cats with PH are different compared to dogs.

This retrospective observational study included 56 healthy cats and 131 cats with L-CHF imaged between 2004 and 2016 at the Veterinary Medical Center, Ohio State University. Key diagnostic variables included tricuspid regurgitation (TR) peak velocity, right atrial (RA) size, right ventricular (RV) size and function, RV wall thickness, pulmonary artery (PA) size, Doppler-derived systolic time intervals of PA flow (STIs), presence of septal flattening, and variables characterizing left atrial size and left ventricular size and function. PH was identified if TR peak velocity was >2.7 m/s (estimated systolic PA pressure >35 mm Hg). Parametric and non-parametric statistical test procedures were used to compare normal cats to cats with L-CHF, and cats with and without PH.

Tricuspid regurgitation was present in 57/131 (44%) of cats with L-CHF. Pulmonary hypertension was present in 22/131 of cats with L-CHF (17%). In 15/22 cases PH was associated with cardiomyopathy, in 5/22 cases with congenital heart disease, and in 2/22 cases to other causes. All cats with PH (22/22, 100%) had subjectively-assessed right-sided enlargement, with larger RA and RV diameters (p<0.0001), thicker RV wall thickness (p<0.05) and higher prevalence of septal flattening (6/22, 27%, p<0.0001) in comparison to cats without PH. Pulmonary artery size and Doppler-derived STIs were not statistically different between cats with and without PH. Maximum right atrial diameter (>21.5 mm; Sensitivity [Sn] 0.82, Specificity [Sp] 0.42) and RV ventricular diameter (>7.8 mm; Sn 0.91, Sp 0.64) had the most accurate cutoff to predict PH compared to other variables. Method reproducibility (measurement variability) was good, with most coefficients of variation <15%.

Compared to dogs, PH is not a common finding in cats with L-CHF. Right-sided enlargement is the main finding in cats with PH, and right-heart dimensions should be used to suspect PH if TR is absent or difficult to measure. Further studies are needed to identify reasons and mechanisms for the obvious differences between dogs and cats.

Disclosures

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