Descriptive assessment of cardiac changes in cats with feline infectious peritonitis

BACKGROUND: Myocarditis and myocardial injury associated with feline infectious peritonitis (FIP) recently are being recognized. HYPOTHESIS/OBJECTIVES: Prospectively document the frequency of cardiac changes in cats with FIP using echocardiography and cardiac troponin I (cTnI) concentrations. ANIMALS: Twenty cats with naturally occurring FIP without previous history of heart disease. METHODS: Cats diagnosed with FIP were tested for common concurrent infections associated with myocarditis by testing serum for feline immunodeficiency virus (FIV) antibodies, feline leukemia virus antigen (FeLV), Dirofilaria immitis antigen, Bartonella spp. immunoglobulin G (IgG), and Toxoplasma gondii IgG and immunoglobulin M (IgM) as well as by testing blood for nucleic acids of Bartonella spp. and coronavirus (SARS-COV-2). Each cat also was tested for serum cTn1 concentration and underwent an echocardiographic examination. After 12 weeks of treatment with antiviral drugs, serum cTnI concentrations were reassessed. RESULTS: All echocardiographic measurements were normalized to patient body weight. The left ventricular posterior wall from right parasternal long axis and short axis was thickened in 55% (11/20) and 25% (5/20) of cats, respectively. Pleural effusion was present in 40% (8/20) of cats and pericardial effusion in 25% (5/20) of cats, but a cardiac cause was not identified for these effusions. Median cTnI at initial evaluation was 0.37 ng/ml (interquartile range [IQR], 0.20-0.83; upper reference interval, 0.20 ng/ml). Repeat cTnI was performed after 12 weeks of antiviral treatment in 6 cats that initially had increased cTnI (median initial cTnI, 0.75 ng/mL) and, in all 6 cats, cTnI normalized to < 0.20 ng/mL. CONCLUSIONS AND CLINICAL IMPORTANCE: Cats with FIP can present with increases in cTnI and ventricular wall thickening, findings suggestive of myocarditis or myocardial injury.