Right ventricular involvement in feline hypertrophic cardiomyopathy.

OBJECTIVES: To evaluate right ventricular (RV) wall thickness and chamber dimensions in cats with hypertrophic cardiomyopathy (HCM).

ANIMALS: One hundred fifty-one healthy control cats and 200 cats with HCM.

METHODS: Retrospective, observational, clinical cohort study. Two-dimensional echocardiograms from all cats were analyzed. Right atrial diameter, RV free wall thickness, and RV chamber diameter were quantified using multiple imaging views. Conventional (mean ± 2 standard deviations) and allometrically scaled (Y = a × Mb) reference values were determined in normal cats and compared to values found in cats with HCM. Linear and logistic regression, multivariate regression, and mixed model analysis were performed to identify associations between RV wall thickness and severity of left ventricular (LV) hypertrophy, clinical severity of HCM, and presence of pleural effusion.

RESULTS: Mean RV wall thickness was increased in HCM (p<0.001). Considering increased RV wall thickness in at least one segment, 94 (47%) and 112 (56%) cats with HCM had RV hypertrophy using upper reference limits based on mean + 2 standard deviations or allometric scaling, respectively. There was an association between severity of LV and RV hypertrophy (p<0.05). Left-sided congestive heart failure (n = 58) was associated with increased RV wall thickness in all segments compared to cats with preclinical HCM (p<0.001). Body weight had negligible effects on RV wall thickness (R2 0.08-0.17, p<0.001), whereas age and breed had no effect (p>0.05) in control cats.

CONCLUSIONS: Increased RV wall thickness is common in cats with HCM and relates to severity of LV hypertrophy and clinical status.