Cardiology

Non-Surgical Closure of Patient Ductus Arteriosus (PDA) in Dogs

Patent ductus arteriosus in dogs is a congenital heart disease in which the ductus did not close at birth, therefore allowing shunting of blood from the aorta into the pulmonary artery. If the shunting is significant, pulmonary hyperperfusion and volume overload of the left heart occur, resulting in left heart failure at a very young age. The murmur of a PDA is a characteristic loud continuous murmur at the left heart base, with bounding pulses.

If the PDA is closed early enough, heart failure can be prevented and the left heart dilation reversed. Classically, closure of PDA has been done surgically via a thoracotomy, blunt dissection of the PDA, and ligation with non-resorbable sutures. Although effective, some complications can occur with this approach. They include rupture of the PDA resulting in a fatal hemorrhage, and abrupt bradycardia (slowing down of the heart rate) resulting sometimes in fatal cardiac arrest.

Alternatives to surgery have been devised more recently. They are techniques leading to embolize (creating a local blood clot) or obturate the PDA with coils, vascular plugs or vessel occluders. These devices are placed into the PDA using guiding catheters introduced via the femoral artery. They require fluoroscopy to accurately position the catheters.

We are performing non surgical closure of PDA in dogs using the Amplatz PDA occluder device. This procedure can only be performed in dogs weighing more than 4 kgs (due to the size of the femoral artery). It currently requires 1-1:30 hours of anesthesia, but recovery is a lot quicker than the one needed after a thoracotomy. The technique consists in introducing a delivery sheath into the PDA, and deploying through that sheath the Amplatz occlude. This device is a double umbrella separated by a narrower waist. The waist is positioned such as to straddle the PDA opening into the pulmonary artery. The umbrellas on each side (one on the pulmonary side, one of the PDA side prevent this device to move. Once the placement deemed satisfactory, the introducing catheter is removed and the femoral artery sutured. The dogs are usually sent home the following day. Sutures of the incision site over the femoral artery are removed 10 days later.

For dogs less than 4 kgs, surgery still remains the only approach, although smaller PDA occluders are currently in the process of being designed.

Careful echocardiographic evaluation is still required prior to the intervention, in order to measure the PDA and evaluate the size of the Amplatz occluder that will have to be implanted. An angiogram has to be performed at the beginning of the procedure to confirm the PDA size.