Diary of a Third-Year Vet Student: An Amazing Big Thing

I recently got a chance to observe a very cool cardiac surgery. The pup came into the teaching hospital with a severe congenital defect in her heart. She had a grade 5 out of 6 murmur, which even inexperienced vet students could hear! Grade 5 murmurs also have something called a palpable thrill, which means you could feel the murmur by putting your hand on her chest. It felt like an electric buzzer was tucked in there.

This particular defect needs to be corrected. If it is not treated, animals die young of congestive heart failure. This pup had the severe murmur, extremely deranged blood flow patterns that we could see on echocardiography, and a greatly enlarged left heart that we could see on radiographs (x-rays). She didn’t have any obvious clinical signs of heart failure but it was only a matter of when, not if.

The defect was a persistent duct between her pulmonary artery and her aorta that should have closed a few days after birth. There are two common ways to correct this defect. The first method is to open up the chest and tie a suture around the persistent duct. Amazingly, this is the cheaper option!

The other method is to place a device called an Amplatz Occluder. This neat little device is specifically designed to resolve this particular defect in dogs, and placement of this device was the option that the owners of this pup chose. To place the occluder, a large catheter is first inserted into the dog’s femoral artery (in its thigh) and pushed all the way up to the aorta and then through the defect. The device is threaded into the catheter and pushed into the pulmonary artery. When it is deployed, it opens up like a mushroom-shaped umbrella. It is pushed up against one end of the duct by the pressure of the flowing blood. The device is made of a special metal mesh that encourages clots to form in and on it, and with time, fibrotic tissue forms around the device. All of this combines to close off that duct. The occluder becomes a permanent part of the dog’s body.

This surgery was a perfect combination of technology, medicine, and physics. Placing the catheters into the persistent duct requires a lot of real-time imaging and a steady hand on the part of the cardiac surgeon. Choosing the right size of occluder requires a lot of tests and imaging even before surgery begins. Here’s the cool physics part: the surgeon deployed the mushroom umbrella and in two heartbeats, the pup’s diastolic blood pressure increased from 30 (way too low) to 80 (in the normal range). In other words, the pattern and pressure of the blood flow through her heart became more normal in just two heartbeats. When she woke up from surgery, her murmur was completely gone. I listened to her new, normal heart rhythm myself. 

This is what makes vet med such a visceral experience. Students were involved in the entire procedure from the beginning. We could ask as many questions as we wanted. We helped obtain the physical exam and imaging data used to diagnose the problem. We watched the surgical procedure from just a couple of meters away. We were responsible for the aftercare of this pup (minimal, she woke up from anesthesia ravenous and ready to go home). And this was just another day in the cardiology unit at our vet school.