Aortic stenosis is a congenital abnormality of the aortic valve or the left ventricle outflow tract. In the United States, subaortic stenosis (SA) is the most common form of aortic stenosis in dogs, counting for more than 95% of such cases. However, this abnormality is considered rare in cats. Due to its uncommon condition, aortic stenosis is sometimes left aside as a differential diagnosis in kittens with murmurs or exercise intolerance. Therefore, this report is intended to describe a case of severe SA in a Persian kitten, with no clinical signs at the moment of presentation.

A 5-month-old male Persian kitten was presented to the Small Animal Clinics for routine vaccination. The owner reported a normal healthy cat, and the kitten, in fact, had no clinical signs, despite a systolic ejection 3/6 murmur, which was loudest at the left basilar region, was heard at the course of regular physical examination. The cat was submitted to EKG and echocardiogram evaluation.

Electrocardiogram revealed sinus tachycardia. Echocardiographic evaluation showed a mild left ventricular concentric hypertrophy, and a severely increased aortic peak velocity was also measured (6.03 m/s, PG 145.5 mmHg). On the other hand, it was not possible to observe a narrowed subaortic region. However, no concave shape nor delayed systolic peak was observed on Doppler tracing from the left ventricular outflow tract and aorta, which indicated that this increased gradient was not due to a dynamic obstruction, but to a fixed stenosis in nature. A mild aortic regurgitation was also determined.

Since the kitten was asymptomatic and had no exercise intolerance or EKG abnormalities, we decided against putting him on beta blockers. At this time, the cat has undergone a 3-month follow-up, without increasing aortic peak velocity and left ventricular hypertrophy. According to his owner, he developed neither clinical signs nor exercise intolerance.

Although rare, subaortic stenosis can affect cats. This report has the importance of awaking clinicians of such condition and emphasizes the necessity of performing a detailed physical examination prior to routine vaccinations or exams.