Unique Treatment for a Unique Case

Aggressive symptoms, an unusual presentation, and an elusive diagnosis called for a multidisciplinary approach across four services at Henry and Lois Foster Hospital for Small Animals (FHSA) at Cummings School of Veterinary Medicine at Tufts University to save a cat with a potentially fatal disease.

The upcoming June edition of the Journal of Veterinary Cardiology will feature the first documented case report treating feline infectious peritonitis (FIP) by both surgical and medical interventions with a positive outcome. The case report titled “Successful treatment of feline infectious peritonitis with pericardiectomy and GS-441524” is authored by clinicians from FHSA’s Cardiology, Diagnostic Imaging, Emergency Medicine, and Critical Care (ECC), and Pathology services.

The five-year-old domestic shorthair cat arrived at the emergency room at FHSA in respiratory distress. An ultrasound showed both pleural effusion (fluid in the pleural space surrounding his lungs) and pericardial effusion (fluid in the sac surrounding his heart). To immediately help him breathe, FHSA’s ECC clinicians performed a thoracentesis to extract the fluid around his lungs and hospitalized him in the intensive care unit (ICU) with oxygen support. An echocardiogram confirmed a large volume of pericardial effusion, with the pericardium itself appearing thick and irregular, concerning for pericarditis (inflammation of the pericardial sac).

Landing on a prognosis was challenging. When encountered in a cat, pericardial effusion is usually secondary to significant underlying heart disease, causing secondary congestive heart failure. However, his echocardiogram did not show evidence of significant underlying heart disease. Bloodwork, a thoracic computed tomography (CT) scan, and samples of the fluid near his lungs and heart did not initially point to a definitive cause. The clinicians suspected FIP, a disease caused by a feline coronavirus mutation. FIP is common in cats, but can be difficult to diagnose. Bloodwork findings can suggest FIP, and pericardial, pleural, or abdominal effusions can also be indicators. However, further confirmatory tests, such as PCR testing on the effusions, are needed to confirm a diagnosis. Previously, FIP was usually fatal to cats, until the recent introduction of an anti-viral medication called GS-441524 that has shown significantly improved survival rates.

Cardiology resident at FHSA and first author of the case report, Dr. Bradley Whelchel (he/him) describes how the clinicians decided on a recommended treatment, “We were worried the cat would either develop recurrent pericardial effusion or constrictive pericardial disease even after removing the pericardial effusion because the pericardium was so thick it would impair the ability of the heart to pump and function normally. The best way to treat and prevent that from happening is to remove the pericardium with a pericardiectomy.”

Pericardiectomy, surgery to take out the sac around the heart, is rarely performed in cats. Regarding the use of pericardiectomy as a treatment option for FIP, there is just one other case of a cat with FIP and secondary recurrent pericardial effusion that underwent a pericardiectomy. This patient recovered from the surgery, but FIP symptoms worsened, and the cat was eventually euthanized, though that cat was not treated with the FIP medication GS-441524.

FHSA’s Soft Tissue Surgery team removed a large section of the cat’s pericardium. The surgery went smoothly, and the cat recovered well and was eventually discharged from the hospital. Additional testing later confirmed the diagnosis of FIP, so the cat was started on a 12-week course of GS-441524.

The cat fully recovered and has had no recurrence of effusions, now almost two years after the surgery.

“It's not as common to have FIP affect the heart, although there are now more case reports coming out showing how FIP can cause secondary cardiac changes. However, we still have much more to learn about FIP,” says Whelchel.

Cummings School clinicians who treated the cat and co-authored the case report with Whelchel include Dr. Fabio Brum Rosa, assistant clinical professor in the Department of Comparative Pathobiology; Dr. Mauricio Solano, head of the Diagnostic Imaging service and associate professor in the Department of Large Animal Clinical Sciences; Dr. Alexia Berg, assistant clinical professor in the Department of Small Animal Clinical Sciences, on the ECC team; Dr. Stephanie Kline, ECC resident at the time; and Dr. Emily Karlin, associate clinical professor in the Department of Small Animal Clinical Sciences, on the Cardiology service.

"This case was a multidisciplinary success story,” says Karlin. “Not so many years ago, FIP was an almost uniformly fatal disease, so it's really amazing to see very sick cats who are able to be cured now."

The case report serves as the first evidence that, if a cat presents with pericardial effusion, inflammation and thickening of the pericardium, and signs of FIP, a viable treatment option is pericardiectomy and a course of GS-441524. Whelchel stresses that not every case like this may require a pericardiectomy; for this patient, surgery was the optimal treatment and diagnostic option, followed by the FIP anti-viral medication.

“FIP should be considered in a cat that has any sort of effusion, including pericardial effusion,” says Whelchel. “Multiple things could have caused the cat's pericardial effusion. It's important not to get blinders on and to make sure to cast a wide net.”

On getting the word out to the larger veterinary community about this positive outcome to an unusual and complicated case, Whelchel says, “We're very happy that it's out in the literature as the first case report where a cat has been doing really well with this unique approach to FIP treatment with both the GS drug and the pericardiectomy.”