Objectives: To investigate the prevalence and progression of murmurs and the development of the left ventricular outflow tract (LVOT) and flow velocities in the great arteries in boxer puppies through adolescence until three years of age.
Methods: Nineteen boxer puppies with or without a low-intensity murmur, but without evidence of congenital heart disease, were studied prospectively. Examinations were carried out at 7 weeks, 3, 4, 6, 9, 12 and 36 months of age by cardiac auscultation and Doppler echocardiography.
Results: Presence and intensity of heart murmurs varied in the same dog and between dogs, but flow velocities did not change. Estimated effective orifice diameter (EOD) and indexed EOD was significantly narrower than measured subvalvular and valvular diameters.
Clinical Significance: The variability in presence and intensity of low-intensity ejection murmurs is high during growth in boxers.