Myocarditis in Cats with Feline Infectious Peritonitis Can Be Cured with GS-441524 and Symptomatic Cardiovascular Treatment.

Feline infectious peritonitis (FIP) caused by feline coronavirus (FCoV) is a fatal disease in cats characterized by variable manifestations. Myocarditis represents a less commonly described pathology within the clinical spectrum of FIP. No research has described the successful treatment of FIP-induced myocarditis. In this study, 40 cats were included and treated with 15 mg/kg of GS-441524 every 24 h orally. All cats were diagnosed with FIP by reverse transcription quantitative PCR in effusion in combination with typical clinical and laboratory changes. Echocardiography was performed in all cats, and myocarditis was suspected in 4/40 cats. Equivocal wall thickness was diagnosed in 2/4 cats, while systolic dysfunction with biatrial dilation was diagnosed in the other 2/4 cats. One cat also presented with ventricular ectopy. A severe increase in cardiac troponin I was seen in all four cats (median 1.82 ng/mL (1.20-5.84 ng/mL)). Cardiac dimensions and electrocardiographic abnormalities completely normalized in all four cats during treatment with GS-441524 and remained stable after treatment discontinuation during a one-year follow-up period. Myocarditis can be a clinical feature of FIP and present with different cardiologic manifestations. FIP-induced myocarditis can be cured with GS-441524 in combination with symptomatic cardiovascular treatment including pimobendan, clopidogrel, furosemide, or atenolol, depending on the clinical presentation.