We weren't even sure we were going to talk about this part of heartworm disease and treatment, but since it happens, we had better cover it.
First the good news from a study:
The authors therefore conclude that dogs with caval syndrome that undergo a transvenous heartworm extraction successfully and survive to discharge, possess a good long-term prognosis.So that's a good result. They call it a minimally invasive surgery. Wonder what the definitions are for that - having someone put "basket forceps through the right jugular vein and into the right heart" seems a little more than minimally invasive, but then again, to us having someone take our temperature is pushing it boundary wise!
And since we used the quote from that page, we might as well include some gruesome photos so that you will want to keep reading about caval syndrome and the surgical treatment for it.
Warning - graphic! Seventy-one worms were removed from this patient's right heart. That's right, 71 worms. I am sure that causes a little hitch in your giddyup.
Are you ready? As someone said, if this stuff doesn't make you think about testing and using heartworm medicines, nothing will.
Here it is...
So, now that we have all of our attention, and probably all of our stomachs in our throats (and it will go back there if you watch the video at the end of this post), what is caval syndrome? From the AHS with our attempts to interpret in ( ).
(First how it starts) When juvenile heartworms (makes them sound like delinquents, which they totally are) first reach the lungs, the blood pressure forces them into the small pulmonary arteries. As they grow and increase in size, they occupy larger and larger arteries until they become fully mature.
The eventual location of the mature adult worms appears to depend mainly on the size of the dog and the worm burden. A medium-sized dog (e.g., Beagle) with a low worm burden (i.e., 10) usually has worms mainly in the lobar arteries and main pulmonary artery (these are locations we are not familiar with exactly but here is a link to a picture). Oh look! Someone did it with the heartworms included!
As the worm burden increases, worms are also located in the right ventricle. Dogs with more than 40 worms are more likely to have caval syndrome, where most of the worms migrate into the right ventricle, right atrium and the caudal vena cava, thus interfering with valvular function and/or blood flow.Now this is interesting and we wish we could understand it better, but talk to your vet, those of you with HW+ dogs awaiting treatment because this is potentially important information regarding activity and your dog and caval syndrome. Unfortunately, it's written in cardiologist (link there) and that does not translate in babelfish.
The exact reason or reasons that a large number of heartworms invade the right heart are not completely understood. It has been noted that caval syndrome is most common in dogs with many heartworms. In one study of experimental dogs, one group of dogs with a large worm burden developed caval syndrome while another group with a similar worm burden did not. In this study, the group of dogs that developed caval syndrome had an average mean pulmonary artery pressure of 60 mmHg while the dogs that did not develop caval syndrome had an average mean pulmonary artery pressure of 30 mmHg. Consequently, it appears that a large worm burden and moderate to severe pulmonary hypertension may be precipitating variables. It should be noted, however, that another study has documented caval syndrome in dogs with an average of only 40 worms and as little as 12 worms in one dog (range from 12 to 125 worms). Also, many dogs in this study had a mean pulmonary artery pressure less than 30 mmHg.How is diagnosed? From the AHS again - oh and if you follow the link, more pictures of caval surgery:
The diagnosis is based on a sudden onset of severe lethargy (click here for what exactly that means - very interesting article) and weakness accompanied by hemoglobinemia and hemoglobinuria (uh, huh...ask your vet). (Merck also says respiratory distress - and good link here for that info) Caval syndrome can be confirmed conclusively by echocardiographic visualization of heartworms within the tricuspid orifice and posterior vena cava (and of course that is also for a vet).
The clinical course usually ends fatally within two days, if surgical extraction of the worms is not pursued promptly.And we know if it is pursued promptly, there are some good outcomes. As always, talk to your vet about this.
So those are the three types of heartworm treatment. This treatment is a little extreme, but necessary as caval syndrome is almost immediately fatal (as opposed to the slower death of heartworm infection that has moved there) if not treated once signs are seen.
To cap this off, we are going to post an incredible video shared by one of Mila's friends on a German Shepherd forum.
Remember to get your pet tested and get started on heartworm meds if you are not doing so.
Next, a Mila update.