About a month or two ago, I was presented with a case that initially threw me for a loop. We were somewhat busy on a Sunday afternoon when a medium sized Shepherd mix was carried in by her owners. She was in obvious respiratory distress - her breathing was labored, her gums were cyanotic (blue-tinged) and pale, and she could not stand. Her condition was so poor, that our receptionist requested that the owners allow me to proceed with Class 1 triage (I start life-saving intervention on the pet before speaking with the owners). They consented to this immediately.
We placed oxygen by face mask initially, placed an IV catheter, and administered a mild sedative to help with the dog's obvious panic. Once she had calmed some, we started our testing. The first thing I wanted was a blood pressure. Given her bluish-white gums, I was worried about anemia, hypoxia, low blood pressure, and a host of other problems. Imagine my shock when her systolic blood pressure was over 300!! My technician was so convinced that our system had a leak or some other problem that she got a new cuff, new sphygmomanometer, and did it again. Still the same, >300.
Scratching my head, I started to mentally go over differentials for profound hypertension in our patients. Unlike people, dogs and cats very, very, very rarely (if ever) have primary hypertension. Humans have it all the time. In a dog or cat, there is an underlying cause - a tumor of some sort, heart disease, renal failure, or something else.
As I was thinking, my technician shaved the jugular to collect blood samples, and I was floored again. My patient had a pounding jugular pulse. To those not in the medical field - it is not normal in any way to see a pet's jugular pulse. You might feel it, you can certainly make the jugular stand up by applying pressure to it, but to see it actually beating like a drum in the neck is absolutely, 100% abnormal. It is a sign of right sided heart failure. Since the right side of the heart is responsible for taking blood that has been used by the body, pumping it through the heart, and into the lungs, it is a low pressure system. If that part of the heart starts to fail, blood starts to back up. It backs up into the vena cavas - one of which becomes the jugular vein. Hence, the jugular pulse. The right heart was failing, and blood was backing up into the jugular.
At that point, I suspected my diagnosis. Respiratory distress, jugular pulses, and severe hypertension in an obviously (from her appearance) outdoor, poorly cared for dog. I summoned the owners to the back at that point to discuss with them the dog's condition.
They were convinced she had been poisoned. Everyone always is. I pointedly asked them immediately if she was on heartworm preventative. Well, no, they said. That stuff doesn't work anyway, right doc?
I carefully explained that their pet appeared to be suffering from caval syndrome. Caval syndrome occurs when the burden of heartworms in the heart becomes so large that the worms start to cause occlusion of the vena cavas. In these cases, there are often >50 adult heartworms living in the heart. The heart begins to fail, and since the right side is such a low pressure system, it happens very, very rapidly.
The owners looked very skeptical. "Now, doc," they said, "we don't want you to fixate on just heartworms. We think she was poisoned."
I sighed, as we started the heartworm snap test running and moved the patient (carefully) into radiology for chest films. Her xrays were classic. Torturous, enlarged pulmonary vessels. Her caudal vena cava (taking blood to the heart form the abdomen) was 3 times the size of her aorta (extremely abnormal). I'd never seen anything like it. Shortly after moving her back to ICU, she urinated a massive amount of dark red urine. This was the final nail in the caval syndrome coffin (once the heartworm test showed up positive). The worm clot in the heart causes a secondary hemolytic anemia - the fragile red blood cells circulating through the bloodstream bump into and break up when encountering this clot. As a result, the patient develops what is called "port-wine hemoglobinuria." The hemoglobin released from the damaged red blood cells is cleared by the kidneys into the urine.
The owners were finally convinced. Due to their financial situation, and the grave prognosis associated with caval syndrome, they elected euthanasia. There IS a treatment for caval syndrome, however. It is radical, dangerous, and can be fatal in and of itself. The only way to stop the process is to physically remove the worms from the heart. This is done by actually making a hole in the patient's jugular, taking a long, long pair of special forceps, and inserting them into the dog's heart, then pulling out clots of heartworms. It is a procedure that few people do, as it is dangerous and has a guarded prognosis. Had the owners the finances and had they wanted me to try, I might have done it - as the dog was going to die anyway, but they did not.
She actually passed away before we were able to euthanize her. It was a very sad case but another excellent reminder of why heartworm prophylaxis is so absolutely crucial, especially in the SOUTH!
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