And Right-Side Heart Failure In Your Dog
It’s Signs And Treatment
Ron Hines DVM PhD
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What is Pulmonary Hypertension ?
Pulmonary hypertension is a term used to describe unusually high blood pressure in the blood vessels leading to, and passing through the lungs of your pet. Ordinary or common hypertension describes another situation in which your pet’s blood pressure is abnormally high in the vessels leading from its heart to the rest of its body. When pet’s develop pulmonary hypertension, their hearts have to work harder than they should.
Your local vet might have told you that your pet has right-side heart failure or the vet might have used a Latin term, cor pulmonale. Cor pulmonale occurs when there are blockages to blood flow through the lungs that increase pressure in the right side of your dog’s heart (pulmonary hypertension). These terms can be confusing. But they are just looking at different aspect of the same basic problem - be it in you or in your pet.
What Are The Symptoms Of Pulmonary Hypertension
In Dogs ?
To understand what symptoms your pet might experience, you need to think about how blood circulates in its body. Oxygen-depleted blood, returning from its body, enters the right side of the heart. From there it is pumped to the lungs through the pulmonary artery to be re-oxygenated. The pet’s lungs act like a car radiator in dispersing the blood and exposing it to as much inspired air oxygen as possible. The re-oxygenated blood then passes back into the left side of the heart to be distributed again to the pet’s body – no different than in your body.
Now any blockage to the flow of the oxygen-depleted blood into the pet’s lungs will cause the blood pressure in that portion of the system to be abnormally high. (up to 4-5 times the normal value of 30 mm of mercury). Blockages of that kind also reduce the amount of re-oxygenated blood coming back from the lungs to the left side of your pet’s heart. With insufficient re-oxygenated blood, your pet will be less energetic, less able to exercise and more likely to faint or show shortness of breath when it’s body’s oxygen needs are greater than what is available to it.
What Are The Causes Of Pulmonary Hypertension ?
The majority of dogs with pulmonary hypertension develop this condition because of disease of their heart valves. But any condition that affects their lung tissue (parenchyma) can restrict the flow of blood through the lungs causing pulmonary hypertension.
The second most common of these other causes are heartworms. Heartworms cause changes that restrict blood flow in this area. But other diseases, including hormone imbalances (Cushing’s disease), cancer, chronic liver or kidney disease, and auto-immune disease.
What Are The Signs Of Pulmonary Hypertension In My Pet ?
That depends on how serious the elevated pressure has become. Many dogs with generalized heart failure have mild pulmonary hypertension and in those dogs, no specific signs are present.
In those dogs, signs are the signs of heart problems in general. They begin with a soft chronic cough , easy tiring and lack of energy and progress to overly fast breathing , gasping (dyspnea) and wheezing – all made worse by exercise.
How Will My Veterinarian Diagnose Pulmonary Hypertension In My Pet ?
Your veterinarian will notice these same signs
that you did. They are all due to a
When your veterinarian listens to your pet’s
heart, the vet will often tell you a heart murmur is present. Most dogs
with serious heart conditions have one. The vet might also hear through
a stethescope the pet’s lungs wheezing, crackling and rubbing
(pleural friction) as they over-inflate to process more air.
But to be one hundred percent certain of the diagnosis, its severity and its best treatment, your vet often recommends that a veterinary cardiologist examine the pet. Veterinary cardiologists own a marvelous machine I covet called a spectral doppler echocardiograph.This ultrasound machine allows one to see the heart, lungs and blood vessels in real-time action, visualize blood flow and estimate arterial blood pressure (through valvular regurgitation jet estimates)(ref) . When blood pressure on the right side of the heart and its attachments to the lungs are too high, your primary vet’s suspicions are confirmed. The most extensive study of the use of this machine in the diagnosis and treatment plan for dogs was done at the Veterinary College in Blacksburg Virginia in 2004. You may wish to read it.
This examination is painless and almost never requires anesthetics or other drugs. Based on the estimated increase in blood pressure to the lungs, the cardiologist will classify your pet’s pulmonary hypertension as mild, moderate or severe.
They might also run or suggest a blood gas study as well to determine the severity of the problem.
Judging The Severity Of Your Pet’s Problem
Pulmonary hypertension is a progressive problem. That is, with time, it will get worse. However, with good veterinary care, many dogs live happily for a long time with the problem.
Mild Pulmonary Hypertension
Most dogs with pulmonary hypertension are in this group – at least initially. These pets have little or no outward signs of their condition. However, your veterinarian might notice that the pet’s femoral pulse is a bit weak, perhaps its liver is a bit enlarged and it probably has a heart murmur. If an ECG is run, there may be signs that the pet’s heart rhythm is abnormal.
Most of these dogs are, or should, be under general therapy for heart failure and the drugs that they are receiving are adequate to help with their pulmonary hypertension as well.
Blood pressure is measured as to how high it will raise a tube filled with liquid mercury. Dogs with mild pulmonary hypertension raise this column of mercury 30 – 55 millimeters.
Moderate Pulmonary Hypertension
Dogs with moderate pulmonary hypertension often have fainting spells when they exert themselves in minor ways. Many have fluid accumulation in the their abdomens (ascites) and some have a puffiness to their legs and thighs due to fluid accumulation there as well (edema). This form of puffiness pits, much as a peach would pit if you pressed on it firmly, and it remains indented even after you release pressure.
If the base of the neck of these pets is closely observed, one can often see the pet’s heart pulse throbbing (jugular pulse). Their EKG readings are almost always abnormal. Fluid accumulated in the lungs and airways make these pets more susceptible to respiratory tract infections. So they may need antibiotics from time to time as well as cough suppressants and bronchodilators medications on a regular basis. Dogs with moderate pulmonary hypertension raise the mercury column 56 – 79 mm.
Severe Pulmonary Hypertension
These pets are in a medical emergency. They may have distress breathing even when they are at rest and they certainly do with any degree of normal exertion. They commonly faint when exerted even mildly. During these periods, their tongue will become bluish (cyanotic). They are often depressed, dehydrated and apathetic. These dogs need immediate oxygen. Their response to medications tends to be poor and they rarely live for extended periods. Dogs with severe pulmonary hypertension raise the mercury column above 79 mm.
What Medications Are Available To Treat Pulmonary Hypertension In My Pet ?
Many dogs with mild to moderate pulmonary hypertension do well on drugs used to treat generalized heart failure in pets and humans. These include ACE inhibitors (like enalapril) positive ionotropes (like Vetmedin) and diuretics (like Lasix). Bronchodilators (like theophylline), calcium channel blockers, antibiotics, and restricted salt diets. If blood clots are thought to be part of the problem, blood thinners like heparin are included.
Other therapies included cough suppressants, bronchodilators, and miscellaneous medications directed at underlying known problems such as cancer, pancreatitis, or collapsed trachea in toy breeds.
But when dogs have fainting spells, or right-side signs that are not controlled with the standard medications, there are other medications that may help. These medications, when successful, lower blood pressure to and in the lungs.
Sildenafil (ref) is the drug that has been used most by veterinarians to specifically treat pulmonary hypertension. It seems to be helpful in about half the diagnosed cases. Sildenafil will not return your pet’s pulmonary pressure to normal, but pets often appear more energetic and in less distress when they take it.
Ambrisentan , bosentan and macitentan are three of many drugs commonly used to treat pulmonary hypertension in humans. Perhaps they might help a pet that is no longer responding to the medications veterinarians commonly use. These medications belong to a class of drugs called endothelin receptor antagonists (ERAs). They block, endothelin, a natural compound that maintains the tone of blood vessel walls. (ref) Once relaxed by ERAs, the blood vessels allow the passage of more blood and lower pulmonary blood pressure in the process. Unfortunately, they all have the potential to harm the liver. (ref)
Humans also suffer from pulmonary hypertension. One of the newest and most promising treatments for pulmonary hypertension in humans is Treprostinil (Orenitram tablets®, Tyvaso® inhaled spray). (ref) This, and other compounds in its class, allow blood to pass more easily through blood vessels. It had a similar affect in dogs which were used as drug models before trepostinil was approved for use in humans. (ref) That last reference also mentions that at the higher doses, the drug had the potential to cause vomiting, diarrhea and fecal abnormalities. If your or your veterinarian elect to use them or the ERAs in your pet, please let me know their effect.
Pets with severe pulmonary hypertension experience rapid temporary relief when they receive 40% oxygen. However, if I had a beloved furry companion that reached a point were oxygen treatment was routinely required, out of love, I would send that pet to Heaven.
Can Pulmonary Hypertension Be Cured? What Is The Long-term Outlook For My Pet ?
There is no known cure for pulmonary hypertension. The goal of treatment is to control symptoms and make your pet’s remaining life as comfortable as possible.
Because this is a progressive disease, doses of medication will need to be gradually increased as symptoms reoccur and additional drugs will be added. This can be done with periodic monitoring with the echocardiograph – but you can accomplish the same thing based on your observation of your dog’s energy level and general comfort at home. (please do not change or add medications on your own) Some dogs do not tolerate one or more medications well, and in those dogs, specific medications need to be discontinued and the drug cocktail recipe changed through trial and error. Only you can provide your veterinarian with the information and a general well-being diary needed to do this effectively.
diary need to record your pets breathing rate, breathing effort, episodes
of collapse, exercise intolerance, appetite, weight change and anything
else you observe that might indicate a change for the better or worse
in its condition.