Mitral Valve Degeneration, Canine Heart Disease, Syncope, and Jet


Heart Circulation Pattern

I have talked about syncope in depth before. If you missed it, you can find the first of a series of articles here.

In short, syncope is a loss of consciousness caused by an interruption of blood flow to the brain.

There are a few possible causes for syncope, but it isn’t a particularly common occurrence in dogs.

This fact doesn’t surprise me all that much because, like his mother (ie: me), Jet never does things by the book.

So, why am I talking about syncope again?

Because Jet had a syncopic episode last night. His last one was two and a half weeks ago.

These episodes are becoming more frequent and this is not a good thing obviously.

So, it’s time to plan our next cardiac ultrasound…to the tune of $475 and change. Being that this obviously wasn’t planned for, we had to add the expense to our fundraising efforts and are keeping our fingers crossed that the kindness of strangers will see us through.

The video below is an example of a cardiac ultrasound on a dog that has a mitral valve insufficiency like Jet.

 

 

What Happens During a Dog’s Cardiac Ultrasound?

During our ultrasound process, a very sweet and bubbly lady comes to our vet clinic. Jet’s vet, his favorite vet tech, and I lift Jet up onto a special exam table.

The table is a slightly odd shape and has a large ‘U’ shape cut out so that the ultrasound technician can access Jet’s heart with her ultrasound wand while he is lying down.

If you’ve ever tried to lift a fearful large breed dog then you will understand that getting Jet on to that table is no easy feat!

Once we get him up there, I hold Jet’s head gently and talk to him while the ultrasound technician looks at his heart structure and watches it in action.

Now, different ultrasound technicians and veterinarians may prefer not to allow dog parents in the room with their pup during the ultrasound process, our vet is not one of them. Of course, during our first visit he respectfully asked the technician if it was alright with her if I stayed, but he and I both knew that it was not really an option to say no.

Any chance you have of getting Jet to lay still in a vulnerable position around strangers, in a strange room, with a strange machine, while being held down, is going to involve me being there to reassure him that they are not, in fact, going to torture him. By now we have the routine down pat, but even with me there, the first few scans we did were quite…eventful.

Anyway, after the technician gets one side of Jet’s heart scanned, we have to flip him onto the opposite side to get a good look at the entire heart structure. This part is never fun because Jet always thinks that we are finished.

When he finds out that we are just turning him over, he lets out a disgruntled grumble and makes his best attempt at an escape anyway.

What Does the Canine Cardiac Ultrasound Do?

The cardiac ultrasound captures a picture of a dog’s heart in action. It looks at the pattern of blood flow, the strength of blood flow, and the structure of the heart.

The technician can take specific measurements and identify changes that take place over time so that any cardiac concerns can be specified as well as measured to track their progression.

In Jet’s case of heart disease, the technician looks at the mitral valve of the heart.

What’s Mitral Valve Insufficiency in Dogs?

Jet has mitral valve insufficiency. This means that, over time, the mitral valve of his heart has become less effective at doing its job – it doesn’t close fully.

The picture below shows the mitral valve between the left atrium and left ventricle. Although this diagram is of a human heart, the circulation pattern is the same.

 

Heart Circulation Pattern

 

The mitral valve of the heart is a flap-like structure that is opened by the increase in pressure caused when the left atrium of the heart fills with blood. This blood then passes through the mitral valve into the left ventricle and the mitral valve closes to prevent blood from moving backwards into the atrium again. Think of it like a gate or a door.

When the mitral valve is diseased, malformed, or “worn” it does not close completely. Think of this as a door or gate that has been left ajar. This enables the blood in the ventricle to move backwards into the atrium where it just came from. This backflow of blood is referred to as “regurgitation”.

Failure to Treat Symptomatic Mitral Valve Insufficiency

Heart Enlargement
After a while, mitral regurgitation causes the atrium of the heart to become enlarged because it is being pushed to hold more blood and to work harder than it normally would.

Enlargement of the heart causes a variety of dangerous symptoms including difficulty breathing and trachea damage. This is something often seen when heart disease progresses into heart failure.

Decreased Blood Pressure
Regurgitation also causes a lower output of blood from the heart since less blood is making it out of the cardiac circulatory process. This decrease in blood volume is what causes a drop in blood pressure.

A drop in blood pressure then causes the body to be unable to provide adequate oxygen and nutrients to the tissues, cells, and organs. When this happens, the body recognizes a crisis taking place and releases hormones to address the crisis.

These hormones cause constriction of the blood vessels. This constriction of blood vessels causes the blood pressure to rise again because it takes more pressure to force blood through narrower blood vessels.

The body then pushes to stabilize it’s blood pressure so that blood vessels can return to their normal size. It does this by retaining water and sodium to increase blood volume.

When this process of fluid retention continues for a period of time, however, it becomes a problem as fluid leaks out of weakened capillaries. This leaked fluid pools in cavities within the body. Where this fluid pools will depend on the side of the heart that is affected. In mitral valve disease, the left side of the heart is affected, so fluid accumulation would occur in the lungs. This would require immediate veterinarian intervention since fluid accumulation in the lungs hinders breathing.

This is why keeping any type of heart disease in our dogs under control is so important.

Treatment Options

There is a variety of medications that can help to control the function of the heart in a dog with mitral valve insufficiency. The medication that your vet recommends will depend on your dog’s individual situation. These different medications can work to control blood pressure, remove excess fluid from the body, dilate veins in the body, regulate hormone release, strengthen the contractions of the heart, dilate the arteries in the body, or slow the heart rate.

We use Enalapril and Vetmedin.

Enalapril is an ACE inhibitor and it works as a hypertensive to reduce blood pressure. Enalapril controls the bodily response to decreased blood volume by expanding blood vessels. This means that the heart no longer has to work harder to force blood through narrowed blood vessels. This results in less fluid retention. Enalapril also suppresses the release of the “crisis” hormones that cause the body to react to decreased blood volume caused by mitral valve insufficiency.

Vetmedin  is a unique drug that works as an inodilator to open blood vessels wider to decrease the demand on the heart to pump harder and it also works to increase the strength of the heart itself.

So essentially, we are decreasing blood pressure, increasing the strength of the heart, and reducing resistance from the blood vessels through our current medication regime.

What’s Next For Us?

The recent increase in Jet’s syncope indicates that somewhere along the way his blood pressure is dropping.

This makes sense since our last cardiac ultrasound 8 months or so ago, showed decreased pumping strength or power of the heart.

It was after this ultrasound that we added Vetmedin to Jet’s Enalapril.

For months we were doing well on our current medication regime, but the increase in frequency of syncopic episodes indicates that something structural has changed in Jet’s heart or one of his medications isn’t doing its job anymore or is doing its job a little too well.

A cardiac ultrasound will be able to tell us what changes (if any) have taken place since our last ultrasound. If the heart has enlarged, mitral valve has weakened further, or pressure of the heart pumping has decreased we will address that by altering our current medications. If there is no change in Jet’s heart function or structure, we will need to address the current dosing of his medications to try to get these episodes under control.

For now, however, we focus on fundraising.

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