Mary Allen
The PDA represents a vascular anomaly in which a vascular connection between the aorta and the pulmonary artery remains after birth. This vascular connection always exists in the embryo, but it should close shortly after birth. This connection allows more blood to enter the pulmonary circulation and thus the left heart. The result is an increasing enlargement of the left main and antechamber. In the final stage, blood can back up in the lungs and heart failure with pulmonary edema (“water in the lungs”) occurs.
Which Animals Get Sick?
PDA is one of the three most common congenital (inherited) heart diseases in dogs, while cats are rarely affected. Predisposed dog breeds include the Spitz, Shelties, Maltese, German Shepherds, and Mini and Miniature Poodles.
What Symptoms Does The Owner Notice?
Even with large epidurals, the majority of patients are asymptomatic for a long period of time, i.e. they show no symptoms. The only clinical sign of the disease is that the dogs have a very loud heart murmur. This is often so loud that the noise causes punctual vibrations in the chest (chest wall tingling). This vibration is noticed by many owners, for example when they pick up their pet. PDAs that have been in use for a long time often lead to left heart failure with the classic respiratory symptoms and later also to poor performance.
The fact that many patients do not show any symptoms for a long time makes the clinical examination of puppies very important. The longer the defect remains undetected, the greater the negative effects on the heart muscle.
Put simply, it can be said that the defect is treated at best as long as the owner does not notice any symptoms because the prognosis is best in this case. If the epidural is discovered too late, the prognosis is significantly worse despite therapy.
Clinical symptoms in left heart failure:
- rapid breathing to the point of shortness of breath
- Cough
- performance intolerance
How Does A PDA Come About? What Are The Effects On The Heart Muscle?
To understand this, you have to delve a little further into physiology. As already described, PDA is one of the congenital diseases. Due to a genetic defect, a vessel – the ductus arteriosus Botalli – does not close. In the embryo, this vessel directs blood past the lungs directly into the aorta. In the case of the unborn child, it makes sense to bypass the lungs because they are not ventilated. Because the lungs are not ventilated, the pressure in the pulmonary vessels is extremely high, even higher than in the systemic circulation. Thus, following the pressure gradient, blood flows from the right heart into the pulmonary artery and from there via the ductus arteriosus Botalli into the aorta and thus into the systemic circulation. The ductus arteriosus bottle is therefore created in all our domestic animals and also in humans during embryonic development in order to bypass the pulmonary circulation.
During birth, the newborn begins to breathe, and the lungs expand. This immediately increases the oxygen tension in the blood. This in turn leads to a contraction, i.e. a contraction of the ductus arteriosus Botalli via a number of different control systems with ultimately complete closure of the vessel within a few minutes after birth.
However, in the patient in whom the epidural remains, the musculature of the ductus arteriosus Botalli is so weak that this contraction only functions incompletely. The ductus remains open, and the PDA develops.
In most cases, the pulmonary pressure has fallen sharply due to the unfolding of the lungs, so the systemic blood pressure is now well above that of the pulmonary vessels. This is why in most patients with epidurals, blood flows from the aorta into the pulmonary circulation and from there back to the left side of the heart.
The result is often a significant enlargement of the left side of the heart, which often leads to left heart failure.
How Is The Disease Diagnosed?
The pet owner often notices an abnormal heartbeat in the form of chest wall tingling. Chest wall trembling describes a loud heart murmur that causes a clear, more or less punctiform vibration of the chest and thus makes the murmur palpable. That chest wall buzz feels a little like putting your hands on a blender. The PDA produces a typical heart murmur, the so-called machine murmur, which can be heard by the vet with a stethoscope. In most cases, a suspected diagnosis can already be made on the basis of the clinical examination. However, cardiac ultrasound is essential to confirm the diagnosis. Here, on the one hand, the blood flow in the PDA and, in most cases, the abnormal vessel itself can be displayed. In addition, the heart ultrasound provides important information about the size and function of the heart muscle, which is of prognostic relevance.
How Can A PDA Be Treated?
In most cases, locking the PDA is unavoidable. Two proven methods are available for this purpose, surgical ligature and catheter-based interventional closure with coils or Amplatzer duct occluders (ACDO). The surgical variant is now considered outdated insofar as it requires a surgical opening of the chest and thus represents a not inconsiderable burden for the patient. Today it is only used in very small patients whose small size means that it is not possible to insert a catheter into the vascular system. Another reason why a catheter occlusion is not possible in some cases is an unfavorable shape of the PDA.
The newer, minimally invasive procedure of catheter-based closure is now the therapy of choice. A catheter is inserted into the vascular system via the femoral artery. A “closure plug” is then placed in the PDA via this catheter. (see PDA lock)
Does A PDA Also Lock Itself?
No. This is one of the reasons why a puppy with a heart murmur should never be given further diagnostics (especially a cardiac ultrasound) until the patient is fully grown. If there is severe congenital heart disease, valuable time can be wasted here.
Is A Drug Closure Possible?
In human medicine, it is possible for premature babies to close the PDA with the help of Cox inhibitors such as ibuprofen. Due to other underlying pathophysiological mechanisms, this does not work in veterinary medicine. Sometimes medication to improve heart function and drainage medication must be given prior to the procedure.
What’s The Prognosis?
The prognosis depends on how early the defect was detected. In most cases, the patients have a completely normal life expectancy with an unrestricted quality of life after successful closure. Early therapy is therefore crucial for the further course. However, it usually does not depend on a few days. In some cases, a puppy is so small that an interventional occlusion has to be delayed a few weeks to allow a catheter to be inserted into the vasculature. As a rule, however, you should not wait longer than a few months.
Can Dogs With Epidurals Be Bred?
The disease can be passed on to offspring. A further use for breeding should therefore be viewed critically.
Do I Have To Take Care Of My Dog?
For the vast majority of heart diseases, the basic rule is that affected animals are allowed to exercise within the framework that they offer themselves. Sick dogs are allowed to exercise normally, but if they want to take a break from training, this must be accepted.
However, very intense training or training in high heat should be avoided in animals with severe findings. After successful closure, a normal load capacity is given in almost all cases. If in doubt, your cardiologist should be able to provide you with information.