This is a small, wide organ in the unborn fetus that links the pulmonary artery to the aorta and enables majority of the blood to move straight from the right sided ventricle into the aorta. Prior to birth, oxygenated blood inside the major pulmonary artery flows inside the descending aorta via the ductus arteriosus, evading the yet non-functioning lungs. When an animal is born and begins breathing, the lungs inflate and cause the ductus to seal and allow the blood to go into the lungs.
Failure of the ductus to close makes the blood to flow from the sectors of the left of the heart to that of the right; such abnormalities are known as left-to-right shunts. This creates over-circulation of the lungs and growth in size of the heart chambers, which results in arrhythmias. As time progresses, symptoms of left-side congestive heart failure become evident.
Dogs that have a tiny ductus may get to become adults without showing signs of heart failure, but are quite prone to swelling and diseases affecting the lining of the heart, which is known as infective endocarditis. In certain cases, a big patent ductus arteriosus may create high blood pressure within the arteries of the lungs, increasing the workload on the heart. This can lead to a situation where the force exerted via the ductus slows and changes direction, i.e. converts to a right-to-left shunt).
Dogs suffering from a patent ductus arteriosus with left-to-right shunting tend to have a very clear, incessant, machinery-like murmur that is detectable using a stethoscope. There are cases, in newborn puppies, where the ductus stays open for a number of days after birth. However, majority of young puppies rarely display any signs. More mature dogs with large shunts tend to have symptoms of left-sided congestive heart failure, with arrhythmias being regularly heard. X-rays may help in detecting large abnormalities, and an echocardiography is also a valuable technique when it comes to excluding coexisting congenital defects, as well as detecting the presence of patent ductus arteriosus.
The best and most effective treatment option for dogs with left-to-right shunting patent ductus arteriosus is to perform surgery that ties off the ductus. However, drugs must be given in order to treat congestive heart failure, prior to performing surgery. Another technique that is available is called interventional closure, which involves inserting a catheter in the patent ductus arteriosus, which is what is responsible for blood clot formation or physical obstruction of the ductus.
Animals that suffer from a patent ductus arteriosus with right-to-left shunting usually have a history of exhaustion, exercise intolerance, and fainting. On careful examination, one might discover a minor bluish tinge to the skin and membranes. The vet might detect other irregularities such as a split heart sound, a soft murmur, or an abnormal rise in red blood cells; these can all be diagnosed by an electrocardiograph and echocardiograph.
Patent ductus arteriosus with right-to-left shunting usually doesn’t respond well to surgically tying off the ductus, as this will cause an increase in blood pressure in the arteries of the lungs, and ultimate death. Treatment involves cyclic blood-letting in order to manage the increase in red blood cells, although the long-term outlook is typically poor.