Until recently, canine patent ductus arteriosus (PDA) was routinely treated via thoracic surgery – opening the chest cavity – to ligate, or tie off, a blood vessel that should have closed soon after birth. Two other less invasive procedures are now available to dog owners to correct this congenital defect. Early intervention is important to prevent permanent heart damage.
Understanding Canine Patent Ductus Arteriosus
Patent ductus arteriosus is a congenital disease in dogs which affects many small breeds, including Chihuahuas, Pomeranians, Maltese and miniature poodles, as well as some larger breeds, most notably German Shepherds, Keeshounds, Irish Setters and Collies.
The ductus arteriosus is a fetal blood vessel which allows blood to bypass the unborn puppy’s lungs, which are not inflated until after birth. The mother dog provides oxygenated blood until this time; then the blood vessel normally closes within a week of the puppy being born. If the vessel remains patent, or open, the heart must work harder. PDA takes two forms, left to right, which is the more typical form, and right to left. In left to right PDAs the blood is moved from the aorta to the pulmonary artery resulting in a murmur, a bounding arterial pulse and if left untreated, left ventricular failure and pulmonary edema, or fluid in the lungs. The aorta and pulmonary artery may also be enlarged.
In right to left PDA or reverse patent ductus arteriosus, the right ventricle is enlarged and the pulmonary artery is enlarged. This form of PDA does not cause such rapid degeneration and, left untreated, dogs may survive for three to five years.
Treatment Options for Patent Ductus Arteriosus in Dogs
Thoracotomy, or the opening of the chest wall, was for many years the only option when treating canine PDA. Once into the chest cavity, the veterinarian ligates, or ties off, the ductus arteriosus, stopping blood from passing through it and restoring normal blood flow through the heart and lungs.
The procedure is reasonably safe in the hands of an experienced veterinary surgeon, with a 95% success rate in uncomplicated cases. When complications such as significant hemorrhage do occur survival rates drop to 60% or less, with small breeds being at highest risk of death.
Less invasive methods have been developed which include placing a coil or mesh device into the ductus ateriosus via a vein or artery. This procedure is most commonly used in human babies with PDA due to a lower risk of complications. In the last few years evidence has accumulated that these newer procedures are equally effective, giving veterinary surgeons and dog owners the chance to decide which is the best option for the individual animal.
Devices For Non-surgical Repair of PDAs
To prevent the flow of blood through a patent ductus arteriosus in dogs, coils made of thrombogenic, or clot producing, fibers; Amplatzer vascular plugs and Amplatzer canine duct occluders may be used. Several studies have provided further insight into the uses of each. In one German study, which targeted the use of single coils in dogs weighing 3kg or less, all 21 dogs in the study were successfully treated using a single coil implanted in the blood vessel via the femoral vein.
A Colorado State University retrospective study looked at the use of single coils, multiple coils or Amplatzer canine duct occluders or vascular plugs in 56 dogs was reviewed. In this case 96.4% of the cases were successfully treated using the femoral vein to access the PDA. Amplatzer canine duct occluder efficacy was tested at Texas A&M University with 40 of 41 dogs being successfully treated via the femoral artery and one dog requiring surgical intervention to close the patent ductus arteriosus.
The size of the ductus and overall health of the dogs had an impact on the success of the treatment. Very large PDAs (> or = 4mm) may require surgery and dogs with significant heart disease are at a higher risk of not surviving the procedure. With the information provided in these studies, it is possible for veterinarians to review options for PDA treatment based on the status of the individual animal.
Henrich, E. et al. 2011. Transvenous coil embolization of patent ductus arteriosus in small (< 3.0kg) dogs. J Vet Intern Med. 25(1):65-70. Epub 2010 Nov 23. Accessed online 7-08-2011.
Gordon, SG et al. 2010. Transarterial ductal occlusion using the Amplatz Canine Duct Occluder in 40 dogs. J.Vet. Cardiol. 12(2):85-92. Epub. 2010 Jul 7. Accessed online 7-08-2011.
Blossom, JE., Bright, JM., Griffiths, LG. 2010. Transvenous occlusion of patent ductus arteriosus in 56 consecutive dogs. J. Vet. Cardiol. 12(2)75-84. Epub 2010 Jul.1. Accessed online 7-08-2011.
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