Patent Ductus Arteriosus in a Pomeranian
History. A 7-week-old female Pomeranian puppy is presented to you because it is not growing as fast as its Iittermates. The breeder says it is lethargic and prefers to sleep, whereas the other puppies play.
Clinical Examination. Clinical examination reveals a small puppy with a rapid heart rate. The mucous membranes of its gums are pink, and its temperature is normal. While holding the puppy around the thorax, you notice a vibration in the region of the heart. When you listen with a stethoscope, you hear a loud murmur that is almost continuous through systole and diastole, and you recall that this is called a machinery murmur. It is difficult to listen to the breath sounds because the murmur is audible all over the thorax.
A radiograph reveals a slightly enlarged heart, but the lungs appear normal, although minimally compressed by the heart. An echocardiogram is performed, which better characterizes the suspected patent ductus arteriosus (PDA). The velocity of blood flow through the ductus and its mean diameter indicate that the dog is a candidate for surgical correction of the PDA.
Comment. The clinical and radiographic findings in a puppy of this age are characteristic of PDA. In some animals the ductus fails to close after birth, and blood continues to flow through it, usually from the aorta to the pulmonary artery. This presents the animal with two problems. First, the left ventricle must increase its output to supply the systemic tissues because so much blood is passing through the ductus. Second, the pulmonary circulation has a volume overload that increases the pressure against which the right ventricle must work. Depending on the magnitude of the PDA, these extra loads result in dilation of the ventricles and sometimes in hypertrophy of the myocardium, which is seen on radiographs as an enlarged heart. The puppy is not growing and is listless because the tissues are not receiving a normal blood flow. Although surgical correction of the PDA allows the puppy to live a normal life, it would be unwise to breed this animal in the future because the condition is inherited.
Treatment. The patent ductus is closed by surgical ligation, and the puppy is expected to have a normal life.
Recently, use of a Iransarterial coil occlusion procedure has been successful in the treatment of animals with PDA. The treatment choice is somewhat dictated by the size of the shunt as well as the presence or absence of heart failure.