Transient Myocardial Thickening in a 4-year-old Korean Domestic Shorthair Cat

A 4-year-old neutered female domestic shorthair cat weighing 5.1 kg was referred to Jeju National University Hospital with acute onset respiratory distress, weakness, and anorexia. The patient had a history of stressful antecedent events that involved bullying by a newly introduced cat. Thoracic radiography and echocardiography revealed a stage C hypertrophic cardiomyopathy phenotype based on the American College of Veterinary Internal Medicine classification system with pulmonary edema, pleural effusion, and pericardial effusion at the same time. The patient was treated with furosemide, pimobendan, and rivaroxaban. Pericardiocentesis was performed because pericardial effusion was identified. Reevaluation after 30 days revealed a normal respiratory rate on physical examination, normal cardiac shape on thoracic radiographs, and normal cardiac measurements on echocardiography. The patient was tentatively diagnosed with transient myocardial thickening (TMT) and all medications were discontinued. Six months after the initial hospitalization, the cat continued to do well without any clinical signs or left ventricular wall thickening. This case is the first report describing feline TMT in Korea. Moreover, it involves a rare case in which pulmonary edema, pleural effusion, and pericardial effusion, which induce cardiac tamponade, occurred simultaneously due to TMT-related congestive heart failure.