The radiographic images that follow have only been altered to remove the names and other identifying features.
Received a call the other night from a rDVM (referring vet) regarding a dog with caval syndrome that he wanted to send this way. The confusing part of the story is that the description I was receiving of the case and the classification of caval syndrome did not really fit.
Caval syndrome is when heartworm disease becomes so severe that there are adult worms present in the right atrium of the heart. For those unfamiliar, calling it heartworm disease is a bit of a misnomer anyway since the adult worms are typically found in the pulmonary artery, not in the actual heart. When caval syndrome occurs, the affected dog is in right heart failure with all the bells and whistles including peritoneal effusion, pulmonary hypertension, congestion of the liver, etc. etc. etc. Often these patients are also in DIC (disseminated intravascular coagulation aka dog in cooler if you have the morbid sense of humor that most in our profession do) and are at high risk for thromboembolic events such as pulmonary thromboembolism (PTE) which is most often fatal. In other words, you have a really sick patient who is not a good candidate for anesthesia. What is the treatment? Anesthetize the animal and surgically remove the adult worms from the heart.
In addition to the above listed problems, dogs with heartworms often get a secondary pneumonitis or severe inflammatory response in the lungs. There is no such thing as waiting to make these patients more stable and a better candidate for the surgery.
Back to the patient at hand. She was described as an approximately 8 year old, spayed female, Basset Hound who had a bicavitary ultrasound showing adult worms in the right atrium, only mild changes to the heart, no evidence of failure including no peritoneal effusion or changes in the liver. I was also told that the dog was bright, alert, and responsive and that the worms had been visualized approximately 48 hours previously. What part of this description makes no sense to you???
Recommended that the dog be sent immediately. As a side note, they were supposed to arrive around 11pm but got lost and rolled in around 1am. The dog was BAR with nothing to indicate to me that it was a caval syndrome dog. We obtained some baseline data including CBC, Chemistry panel, PT/PTT, and d-dimers. Nothing particularly exciting on the bloodwork other than mildly elevated liver enzymes. We then obtained thoracic radiographs. Four views to follow:
Ventro-dorsal thorax
Dorso-ventral thorax
Right lateral thorax
Left lateral thorax
So the obvious is the large heart with a "reverse D" appearance that is oh so typical of heartworm disease. The interesting part to me is the suggestive appearance of pulmonary edema consistent with left heart failure that is not really pulmonary edema. What you see, particularly in the DV and right lateral views, is an extremely huge, tortuous pulmonary artery (I would put in an arrow or outline it but couldn't figure out how - hmmmmm.....). Pretty impressive isn't it?
Blood pressure was normal, ECG was normal. Called in the cardiologist who did an echocardiogram and determined that there were no worms in the right atrium. We then looked at the echo video sent by the rDVM and there were indeed worms present two days prior. She apparently "resolved" her own caval syndrome so to speak. Clearly, she did not develop severe symptoms therefore the worms must not have been present for long. I find it extremely amazing the things that our patients can deal with and still be okay.
In talking to the dog's owners, I found them to be extremely concerned and caring people. The dog had been diagnosed with heartworms a minimum of 3 years previously because she was positive at the time when they adopted her. So why didn't they do anything?!? Misinformation. Either through their misunderstanding or incorrect information given by someone (could have been rDVM or other vet or some random person since I have learned people often listen better to what "Aunt Polly" found off the internet than they do to trained veterinarians) they were under the impression that heartworm disease is incurable.
We opted to treat for presumptive pneumonitis and use a medication to decrease the risk of thromboembolic events then begin a two stage adulticidal therapy with required hospitalization during each stage of the therapy. The prognosis is still guarded since the same risk factors enumerated earlier still apply but it's probably better than having to go to surgery (although surgery would have been way more cool!) With some luck, this very sweet dog will get treated, do well, and still have some really good years ahead.
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