A 3 month old Samoyed presents to you for vaccination. On physical examination a left basilar systolic heart murmur is detected. Thoracic radiographs appear normal. The EKG also is normal. Once again Echocardiography is ideal to confirm the diagnosis of this congenital cardiac disorder. As for aortic stenosis, Doppler Echocardiography is the specific mode of echocardiography which offers the most information to establish the diagnosis of pulmonic stenosis and address the severity of the disorder.
Routine Two-dimensional Echocardiography nevertheless provides much insight into the disorder. As the severity of the pulmonic stenosis increases, one will observe an increase in the thickness of the interventricular septum and right ventricular free wall. The moderator band of the right ventricle also increases in size. The region of the pulmonic valve is noted to be narrowed and the motion of the pulmonic valve is seen to be restricted (reduced amplitude of excursion). The main pulmonary artery is usually noted to be enlarged. On the M-mode examination the measured thickness of the interventricular septum is increased as well as that of the right ventricular free wall. The motion of the interventricular septum is noted to be abnormal demonstrating a flat motion in systole.
The Doppler Echocardiographic examination reveals an accelerated velocity of blood flow across the pulmonic valve in systole. The normal maximal antegrade velocity of blood flow across the pulmonic valve should be no more than 1.2 meters per second. Thus peak velocities of blood flow detected in excess of 1.2 m/s (especially velocities in excess of 2.0 m/s) across the pulmonic orifice in systole suggest pulmonic stenosis. As the severity of the stenosis increases the measured maximal velocity of blood flow detected increases. Velocities in excess of 5 m/s indicate a severe degree of stenosis.
The Doppler study in this dog revealed a velocity of blood flow across the pulmonic valve of 2.5 m/s and pulmonic valve insufficiency.