Patent Ductus Arteriosus In Dogs

Patent ductus arteriosus is one of the most common hereditary heart diseases in dogs. It is due to the malfunction of the fetal ductus arteriosus muscle to contract or persistence of ductal patency after the neonatal period, leaving an opening for blood flow.

“Patent” means “open”. When a fetus is in the womb, the lungs are not used because the fetus feeds oxygen from the mother dog’s placenta directly. Ductus arteriosus is a vascular structure that shunts blood from the main pulmonary artery (which transports deoxygenated blood to the lungs) to the descending thoracic aorta (which supplies blood to the aorta).

The fetal Ductus Arteriosus should close completely within the first week of birth to direct all the blood coming from the right side of the heart through the lungs and obtain the oxygen that is required to carry on normal functions of the body.

When this temporary blood vessel doesn't close, a flow of blood is reversed through the unclosed vessel (thoracic aorta to the pulmonary artery) allowing for ‘oxygen-rich blood’ from the aorta to mingle with ‘low-oxygen blood’ in the pulmonary artery. Surplus blood in the lungs results in the buildup of fluid. The left ventricle is filled with too much blood and this means the heart has to pump harder that elevating blood pressure in the pulmonary arteries. This will end in heart malfunction, typically within the 1-2 years of life--specifically, if the condition remains untreated and depending on its severity.

Sometimes, the PDA may be “silent” (not identified clinically but inadvertently diagnosed by echocardiography done for a different reason), small, large, or moderate. Irrespective of the size, complications may arise, sooner or later.

• Difficulty Breathing
• Abnormal Pulses
• Loud Heart Murmur
• Sleep more than usual.
• Stunted in growth.
• Fatigue / Cough
• Respiratory Distress

Surgical Ligation:

Lateral Thoracotomy (intercostal thoracotomy) - Thoracotomy is performed on the left side of the chest through the third or fourth intercostal space to explore the thoracic cavity and gain access to the surgical site. Even in the smallest dogs, the prognosis is excellent for a normal life and operative success should be greater than 90 percent.

Cardiac catheter-based (minimally-invasive surgery) occlusion - Catheter-based occlusion (a ductal occludeor closing the duct with coils) is a minimally-invasive alternative that uses the Titanium ligating clips or a custom-designed thoracoscopy clip applicator.

Transarterial PDA coil embolization: Catheterization of the femoral artery and placement of coils (made of surgical stainless steel with prothrombotic poly-Dacron fibers) into the femoral artery under general anesthesia. To delineate PDA morphology and facilitate coil selection, an angiogram is then performed.

Drug Therapy: When surgery is not an option or if heart failure has occurred, drug therapy with Indomethacin, enalapril or benazepril, digoxin, and furosemide is often prescribed.

Every breed of dog is different and indeed every individual dog is different in its own right.

This means that the best home remedies (such as diets) for your dog undergoing treatment for heart disease - depending on your dog.

Occasionally long-term follow-up appointments may be required if your animal is taking any cardiac medication or if there is any possibility of long-standing effects (permanent damage) to the heart.

Prevention of PDA is a hereditary concern. Dogs with PDA including First degree relatives (littermates and parents) should not be bred so as to avoid passing the condition on to the next generation.

Screening of highly affected breeds prior to breeding is strongly recommended.

Maltese, Pomeranian, Shetland Sheepdog, English Springer Spaniel, American Cocker Spaniel, Keeshond, Bichon Frise, German Shepherd, Collie, Irish Setter, Kerry Blue Terrier, Labrador Retriever, Newfoundland, Miniature Poodle, Toy Poodle, Chihuahua, Yorkshire Terrier

1. Causes:

• Mostly Congenital
• Malnutrition
• Toxicological
• Infections
• Environmental
• Pharmaceuticals

2. Types:

Based on its angiographic features, the Patent ductus is classified as:

• Type A: Conical with constriction near the pulmonary artery end and prominent aortic ampulla.
• Type B: Wide and very short (window-like) ductus.
• Type C: Tube-shaped ductus (no constrictions).
• Type D: Convoluted Ductus
• Type E: Elongated ductus and the constriction is distant from the trachea’s anterior edge.

3. Morbidity:

It is important to fix PDA because it can lead to congestive heart failure and hypertrophy or dilatation in the structure and function of the right ventricle (RV) (called cor pulmonale) later in life. PDA also increases the risk of endocarditis, a life-threatening infection of the endocardial surface of the heart that covers the valves, main arteries, and heart chambers.

Prostaglandin E2 is thought to promote the patency of the ductus. When the ductus doesn’t close after birth, it is associated with pulmonary hemorrhage, pulmonary edema, intraventricular hemorrhage, congestive heart failure, necrotizing enterocolitis, bronchopulmonary dysplasia (BPD), and renal failure.

The ratio of pulmonary vascular resistance (PVR) to systemic vascular resistance (SVR) is one of the main factors that determine the magnitude of the right to left shunt.

If the SVR is high and PVR is low = the blood flow through the shunt to the lungs will be elevated.  Blood flow is increased to the left atrium and left ventricle leading to left atrial and left ventricular hypertrophy.

4. Mortality:

The untreated PDA shows clinical signs usually within a year. Dogs with PDA have a more than 50% mortality rate by one year of age if left untreated.

After congestive heart failure has developed due to PDA, Life expectancy is variable and it is typically around 6-14 months. Very few dogs have PDA small enough that congestive heart failure eventually does not occur.

5. Diagnosis:

• Routine Hematology, Urinalysis
• Serum Chemistry Profile
• Electrocardiogram
• Cardiac Ultrasound
• Echocardiography

6. Prognosis:

When detected early and given appropriate treatment with successful closure of the PDA, most dogs live a normal life. Unless there are complications from already developed heart failure or other heart defects, there is rarely any need for medications in the future.

Time to visit the vet clinic for an examination, if you notice any of the following:

• Difficulty Breathing
• Abnormal Pulses
• Loud Heart Murmur

• In diets elevated in protein (>100 grams per 1000 calories) at least 30% meat-based protein (on a dry matter basis) is recommended.
• PDA dogs' ability to excrete sodium in their urine is markedly reduced. Sodium or salt should be limited to help reduce fluid accumulation.
• Foods that tend to be high in salt should be cut off. snack foods (crackers, chips, pretzels, etc.), bread, pizza, cheese, other dairy products, etc.
• Omega-3 fatty acids (fish oils) and amino acid foods/supplements.
• Vitamin E and Co-enzyme Q10.
• Carnitine, B Vitamins, and Magnesium.
• Maintain ideal body weight and Fresh food can be a very healthy option.

It’s never pleasant to hear your dog has heart defects. The prognosis for PDA dogs is much better than with other heart defects. Many PDA dogs can live normal lives if they are without any other complications. Dogs with mild symptoms can be managed with medications.