Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Two The Thorax 139
A
Fig. 2-110 A 2-year-old male Neapolitan Mastiff with failure to gain weight and labored breathing
after exercise. Auscultation revealed a continuous (machinery) murmur. Radiographs revealed generalized
cardiomegaly and prominent pulmonary arteries. A, A right parasternal short-axis view
reveals marked dilation of the right ventricular outflow tract (rvo), as well as the main (pa) and right
(rpa) pulmonary arteries. B, The right parasternal long-axis aortic outflow view reveals dilation of
the left atrium (la) and left ventricle (lv). Also identified are the right ventricle (rv) and aorta (ao).
Diagnosis: Patent ductus arteriosus.
B
Fig. 2-111 A 6-month-old male, 30-
lb mixed breed dog had a continuous
murmur. The M-mode echocardiogram
revealed marked dilation of the
left ventricle (LVDd = 50 mm).
Diagnosis: Left ventricular dilation
due to volume overflow from a
patent ductus arteriosus.
The echocardiogram in dogs with PDA will reveal left atrial and left ventricular dilation,
and eccentric hypertrophy may be present (Figs. 2-110 and 2-111). The EPSS, the
point of maximal mitral valve opening to left ventricular septal echo, may be greater than
normal. Fractional shortening will be either normal or diminished subsequent to the ventricular
dilation. In some cases, the aneurysmal dilation of the aorta will be identified.
Dilation of the pulmonary artery is seen more frequently. In some cases with long-standing
disease, there may be right ventricular dilation. Direct visualization of the ductus is
uncommon but may be accomplished in some cases by using a parasternal short-axis view
at the heart base. 288 Doppler studies may reveal a continuous flow disturbance and a highvelocity
retrograde flow toward the pulmonic valve in the proximal pulmonary artery (Fig.
2-112). 289 Mitral and aortic regurgitation is identified often as well.