Severe Subaortic Stenosis in a Six-Year-Old Pug

Abstract

Aims: Subaortic stenosis (SAS) is the most frequently diagnosed form of aortic stenosis in dogs, typically identified in large breeds during early life. However, its manifestation in atypical breeds or adult animals is less commonly described. This case report highlights the diagnostic approach, clinical course and medical management of SAS in a Pug, emphasizing its relevance in older small-breed dogs. Presentation of Case: A six-year-old intact male Pug was presented with exertional intolerance and syncopal episodes. Clinical examination revealed a grade V/VI systolic murmur at the left heart base. Hemato-biochemical parameters, including liver and renal function tests were within normal ranges. Thoracic radiography demonstrated cardiomegaly, while electrocardiography showed sinus rhythm with ST slurring. Echocardiography identified a broad fibromuscular ridge in the left ventricular outflow tract (LVOT), concentric left ventricular hypertrophy and a peak aortic velocity of 5.41 m/s, corresponding to a transvalvular gradient of 117.12 mmHg, consistent with severe SAS. Diastolic dysfunction was evidenced by a reversed E/A ratio on pulsed-wave Doppler. The dog was managed with atenolol (6.25 mg PO q12h) alongside exercise restriction. At five-month follow-up, the owner reported improved tolerance to activity with no recurrence of syncope. Discussion and Conclusion: This case underscores the clinical importance of considering SAS in adult dogs of any breed presenting with exertional collapse. Echocardiography remains indispensable for definitive diagnosis and grading severity. While the prognosis of severe SAS is guarded, medical therapy with beta-blockers may provide symptomatic relief and short-term improvement.