Canine Infectious Diseases: Self-Assessment Color Review, Q&A 12

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Student tip: This case is an interesting history, allowing many differentials to be covered.

A 6-year-old neutered male, 20.6 kg mixed breed dog (see image) was referred for a cardiac work-up, because the referring veterinarian had heard a new continuous heart murmur. The dog was known to have had a systolic murmur for several years. Along with dental prophylaxis, a grade I mast cell tumour had been surgically removed from the right thoracic limb 1 year previously. There was no history of exercise intolerance or other clinical signs. The dog lived in Ingolstadt, Germany, and was current on vaccinations and treated regularly with parasiticides. He had never travelled outside Germany. Physical examination revealed that the dog was active, alert, and responsive. The rectal temperature was 38.9°C (102.0°F), mucosal membranes were moist and pink, capillary refill time was <2 seconds, all lymph nodes were of normal size, and abdominal palpation was unremarkable. Lung sounds were physiologic, and the respiratory rate was 36 breaths/min. A left basal continuous heart murmur with an intensity of V/VI was audible. The regular heart rate was 128 bpm. Pulse quality was normal, without pulse deficit or evidence of jugular vein distension/pulsation. The remainder of the physical examination was unremarkable.

Question	Answer		Article
What is your interpretation of the physical examination, and what are the differential diagnoses for the described heart murmurs?	The main problem identified on physical examination was the new continuous heart murmur with point of maximal intensity over the left heart base. The previously documented left basal systolic murmur could result from pulmonic stenosis (PS) (infundibular, sub, supra, or valvular), aortic or subaortic stenosis (AS/SAS), tetralogy of Fallot, obstructive outflow disorders, or an atrial septal defect (ASD) leading to a relative pulmonic stenosis. Given the loud murmur intensity and the fact that it had been present for several years, an ASD was considered unlikely. The continuous left basal heart murmur could be due to a congenital persistent ductus arteriosus (PDA) or a coexisting systolic and diastolic murmur (e.g. AS/PS along with severe aortic or pulmonic insufficiency, respectively). As the continuous murmur was newly reported, an acquired cause was more likely than PDA.		Link to Article
What further diagnostic procedure should be recommended?	Echocardiography should be performed to identify the cause of the heart murmur.		Link to Article

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