Solutions to "What's Your Diagnosis?"
Electrocardiogram Interpretation and Diagnosis: Right axis shift. Note the deep S waves in leads I and II indicative of right ventricular enlargement.
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Echocardiogram: Echocardiogram revealed mild to moderate right ventricular hypertrophy, mild tricuspid regurgitation, and a narrowing of the RVOT (right ventricular outflow tract) at the level of the pulmonic valve. The velocity of the blood flow across the pulmonic valve was measured at 5.6 m/s. Using the Bernoulli equation, p=4v², the transpulmonic pressure was calculated to be 145 mm Hg.
Diagnosis: Severe valvular pulmonic stenosis.
Pulmonic Stenosis: Congenital stenosis (narrowing) usually occurs at the level of the valve, but it can occasionally be supravalvular or subvalvular. Pressures under 50mm Hg are considered mild, usually results in no clinical signs, and no treatment is required. Pressures above 80mm Hg are considered severe. There may be concurrent signs of right-sided heart failure (pleural effusion, hepatomegaly due to congestion with resulting ascites), exercise intolerance, syncope, or sudden death.
Stenosis of the right ventricular outflow tract causes pressure overload of the right ventricle which results in hypertrophy. The high velocity jet into the pulmonary artery eventually results in its dilation. Hypertrophy of the right ventricle may result in tricuspid insufficiency and predisposes the dog to arrhythmias and ischemia.
Breeds prone to pulmonic stenosis include English Bulldogs, terriers (West Highland White, Fox, Scottish), Miniature Schnauzers, Chihuahuas, Beagles, Boxers, Cocker Spaniels, Mastiffs, and Samoyeds.
Balloon valvuloplasty is the treatment of choice. Aberrant right coronary vessels that might encircle the RVOT must be ruled out using angiography prior to any balloon attempt. English Bulldogs have a higher frequency of a right coronary vessel, but it can occur in any breed. Balloon valvulopasty can significantly increase the lifespan of severely affected dogs.