In this post we are going to continue talking about patent ductus arteriosus (PDA) and specifically the most common clinical findings in dogs. PDA is more frequent in females and, although there are some predisposed breeds, it can occur in other breeds and commonly occurs in mongrel dogs.

Some dog breeds with predisposition to PDA
  • Bichon Frise
  • Chihuahua
  • Cocker Spaniel
  • Collie
  • Springer Spaniel
  • German Shepherd
  • Keeshond
  • Maltese
  • English Shepherd Dog
  • Poodle
  • Shetland Sheepdog
  • Pomerania
  • Yorkshire terrier

Most dogs have a PDA I-D, are asymptomatic and present with a continuous, high grade murmur (usually with fremitus) present in the specific area of the PDA. It is important to auscultate puppies in an area slightly peripheral to conventional auscultation areas such as the left apex (mitral valve), left base (dorsal aorta and ventral pulmonary) and right apex (tricuspid valve). The murmur of the dog with PDA usually peaks in an area slightly dorsal to the cardiac base in the left hemithorax.

Another typical feature of puppies with PDA is the presence of a “jumpy” femoral pulse on palpation caused by a lower than normal diastolic pressure with a consequent increase in pulse pressure reflecting the pressure difference between systole and diastole.


A lateral radiograph shows the chest of a dog after implantation of an ACDO device (Amplatzer Canine Ductal Ductal Occluder; White Arrow). The site of the ACDO visually indicates the area where the point of maximum intensity on auscultation would often be found. This zone is located slightly dorsal to the auscultation zone of the cardiac base (red zone) and apex (blue zone).

A useful “trick” to differentiate the presence of systolic, diastolic or continuous murmurs is the simultaneous palpation, at the same time as auscultation, of the femoral pulse, which occurs in systole. In addition, the murmur often radiates widely and sonorously on both sides of the chest, and it may be difficult to pinpoint the point of maximum intensity by auscultation. In these cases, palpation can be very helpful: the point of maximum intensity will coincide with the anatomical location of the fremitus.


PDA L-R will cause volume overload and progressive enlargement of the pulmonary artery and veins, and the left atrium and ventricle.Eventually there may be progression to left congestive heart failure (pulmonary edema).

In the latter case, dogs will present, in addition to the characteristic murmur, with classic clinical signs of left heart failure such as tachypnea and tachycardia sometimes accompanied by crackles on auscultation, cough, or clinical signs of circulatory collapse. In addition, in most dogs with PDA, there is cardiac remodeling and increased sympathetic tone that may be substrates for the development of supraventricular or ventricular arrhythmias that could be detected during physical examination.


In patients with CAP R-L the clinical presentation is very different. These patients will not present with a murmur and the most common clinical sign will be the appearance of hind limb weakness during exercise, due to differential hypoxemia affecting the caudal/inferior part of the body..

Less commonly these patients may present with more diffuse signs of hypoxemia, such as exercise intolerance; or, clinical signs due to direct consequences of Eisenmenger’s syndrome (in which chronic hypoxemia causes appropriate secondary polycythemia), such as lethargy or seizures.

In the next post we tell you more about PDA: diagnosis, treatment and prognosis.

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