Arterial Thromboembolism Secondary to Subaortic Stenosis in a Persian Kitten

Background: Aortic stenosis refers to several types of anatomic and functional obstructions of the left ventricular outflow tract. In small animals, this anomaly is most commonly documented as either a congenital lesion or an obstruction that develops soon after birth. It is a hereditary disease, caused by a dominant autosomal gene and modifying genes that interfere with phenotype expression. Even though aortic thromboembolism may be a potential complication in cats with cardiac diseases, aortic stenosis is deemed rare in that species. In this paper, we report an unusual case of a Persian kitten with aortic stenosis that eventually developed arterial thromboembolism.Case: A 7-month-old Persian kitten (3.1 kg) was admitted to a Veterinary Teaching Hospital with a history of hindlimbs paralysis over the past 48 h, as well as excessive vocalization. Also, the cat presented with inappetence, adipsia, urine incontinence, and hematuria. On physical examination, we observed hypothermia and cold paws. The footpads were cyanotic and there were no palpable femoral pulses. Cardiac auscultation disclosed a regular fast pace (200 bpm) and a grade 2/6 murmur heard best over the left cardiac base, but irradiating to the contralateral hemithorax. Prothrombin time and activated partial thromboplastin time were within the normal reference range, but the complete blood count showed microcytosis, lymphopenia, and hyperproteinemia. Also, elevated alanine aminotransferase and BUN were identified. On the echocardiogram, we observed a subvalvular aortic stenosis, which resulted in concentric remodeling of the left ventricle and a mild left atrial dilation. The stenotic lesion was classified as mild. Also, the thoracic radiography unveiledcardiomegaly. The recommended therapy included atenolol (6.25 mg/cat PO, q24h), clopidogrel (18.7 mg/cat PO, q24h), enoxaparin (1 mg/kg SC, q24 h), methadone (0.2 mg/kg IM, q8h) and amoxicillin + potassium clavulanate (20 mg/kg SC, q12h). Additional recommendations included physical therapy on the hindlimbs as well as monitoring heart rate and blood pressure every two hours in the first day, and every six hours thereafter during hospitalization. Seven days later, the cat was depressed, extremely lethargic, and did not respond to therapy at all. Also, necrosis was documented on the hindlimb paws. Therefore, in face of the unfavorable prognosis, the owners opted for euthanasia.Discussion: Cats with cardiomyopathy have an increased risk for developing arterial thromboembolism. The dilated left atrium causes blood stasis and, because of the augmented sensitivity of platelets to serotonin, they aggregate and increase the likelihood of thrombi formation. While some thrombi remain within the heart, usually in the left atrial appendage, others may dislodge and follow blood flow to the aortic trifurcation down in the abdomen. That obstruction impairs blood flow to its tributaries such as the iliac and femoral arteries, which are involved with the hind limbs perfusion. Cats with severe stenotic lesions usually carry a bad prognosis, contrasting with our patient in which only a mild stenosis was documented.However, having developed aortic thromboembolism absolutely changed the prognosis for this cat. Although aortic stenosis is an uncommon condition in cats, its occurrence should be considered as differential diagnosis whenever young patients are admitted with a cardiac murmur. If the diagnosis is confirmed, the patient will need periodical re-evaluations due to the possibility of complications such as arterial thromboembolism. This condition carries a bad prognosis. In this case, it was responsible for the decline in clinical condition which eventually was crucial for the owner opting to euthanize the cat.Keywords: congenital heart disease, echocardiography, valve dysplasia, ischemia