Heart Failure, Congestive (Right-sided) in Dogs

Congestive heart failure (CHF) is a non-specific symptom that can occur with many different types of heart disease. CHF can be either left-sided or right-sided depending on which part of the heart is involved; occasionally, CHF may be biventricular, affecting both sides of the heart at once. Many signs of CHF, such as fainting, shortness of breath, and inability to exercise are common to both left and right-sided origins, however small differences in your dog’s symptoms may suggest which side of the heart is more involved and help the veterinarian make an accurate diagnosis of the problem causing CHF. Oxygen depleted blood from the veins enters the right atrium. It passes through the tricuspid valve into the right ventricle before being pumped into the lungs as the heart contracts. If the right side of the heart is weak, or the tricuspid valve is not functioning properly, the heart is unable to pump as much blood to the lungs for oxygenation. Pressure can build up in the veins that transport blood to the right atrium, sometimes causing a strong pulse and marked protrusion in the jugular vein in the neck. Meanwhile, blood will pool in the lungs since the reduced force of the heart’s contraction will not push it on to the left side of the heart as quickly. Fluid from the stationary blood frequently leaches out of the lungs and accumulates in the abdomen (called ascites). This is the most distinctive symptom of right-sided congestive heart failure. Dogs often have a distended pear-shaped belly, and may be reluctant to lie down or put pressure on their abdomen. Left-sided CHF on the other hand will be more likely to cause fluid accumulation within the lungs (pulmonary edema) with symptoms of coughing. Both types of CHF ultimate lead to oxygen depletion in the tissues and eventual heart failure, so CHF is a very serious condition.

Congestive heart failure is a symptom that often occurs in dogs with severe heart disease. If the problem begins in the right side of the heart, this is called right-sided congestive heart failure. Fluid accumulation in the abdomen is the most distinctive symptom.

These are some of the symptoms you might notice in a dog with right-sided CHF.

• Distended abdomen (ascites)
• Discomfort while lying down
• Swollen limbs from fluid accumulation
• Increased breathing rate
• Exercise intolerance
• Lethargy
• Weight loss
• Weakness
• Fainting
• Noticeable protrusion of the jugular vein in the neck
• Strong pulse in the jugular vein

Types

These are the different types of CHF that might affect your dog’s diagnosis.

• Right-sided CHF (problem originates on the right side)
• Left-sided (problem originates on the left side)
• Biventricular (problem affects both sides)

• Atrioventricular valve degeneration (tricuspid valve)
• Dilated cardiomyopathy – more common in large dogs
• Heartworm
• Congenital heart defects (tricuspid dysplasia, ventricular septal defect, atrial septal defect)
• Tumor in the heart
• Infective endocarditis affecting the tricuspid valve (rare)

The veterinarian will physically examine your dog. A heart murmur may be audible through a stethoscope and the veterinarian may even be able to tell which valve is affected based on the placement of the murmur. This, along with other symptoms like fluid accumulation in the abdomen or legs can suggest the problem is located on the right side of the heart. Right-sided CHF is a symptom rather than a disease, so the veterinarian will need to diagnose the underlying condition that is causing your dog’s heart to fail. The most common problem is some degree of backflow, or regurgitation in the tricuspid valve that connects the right atrium and ventricle. This could be caused by an inherited condition, age related degeneration, a cancerous tumor, or a heart infection (although this is more likely to cause left-sided CHF). 

More definitive diagnosis is made with x-rays of the chest, as well as electrocardiography, and echocardiography (an ultrasound of the heart). Chamber enlargement may be visible on an x-ray, while an electrocardiogram will record abnormal heart rhythms. The echocardiogram is the most useful tool for diagnosis since this shows the heart in more detail. The veterinarian will also order blood tests and urinalysis to check for infection that could be causing or contributing to your dog’s symptoms. Dogs with severe CHF will usually have signs of liver and kidney dysfunction as well, which may be apparent on these tests. Most dogs with right-sided CHF are also given a heartworm test, which measures for abnormal proteins produced by the worms. The larvae and adult worms live in the arteries that connect the heart and the lungs and often spread into the right ventricle and atrium, so heart failure from heartworm infection usually starts in the right side of the heart.

Dogs with moderate to severe problems may need to be hospitalized until the condition is stabilized. Taps will be inserted to remove fluid from the abdomen and around the heart (called abdominocentesis and pericardiocentesis). Strong diuretics, such as furosemide, may be injected to further encourage fluid elimination, and dogs may need additional oxygen.

Once the immediate attack is stabilized, long-term medications will be prescribed to help to control symptoms. Diuretics and ace inhibitors are the most common medications used to reduce fluid build-up and improve blood flow. Pimobendan can increase the force of the heart’s contractions, and digoxin may be prescribed if your dog’s heart rate is very fast. Beta-blockers and calcium blockers could also be suggested depending on your dog’s condition. Most treatment plans will combine a number of different medications.

Other treatment will focus on eliminating the problem that is causing CHF. If your dog has heartworm, it can be treated with medication once your dog’s symptoms are stabilized. Some conditions, like atrial septal defect, can be treated with surgery. Others cannot. Valve replacement is only done very rarely in dogs, so problems that affect the valves are often only untreatable symptomatically.

Recovery will depend on treating the problem which led to right-sided CHF. Mild heartworm infection, or a heart defect that is treatable surgically can have a reasonably good prognosis, but if severe CHF has developed there may be permanent damage to the heart muscles. With medical management, dogs have an average survival rate of 6-12 months. A low salt diet is recommended and dogs should only be allowed mild exercise. Frequent checkups will be necessary so the veterinarian can monitor your dog’s condition and assess the effectiveness of treatment. Keeping a close watch on your dog’s breathing rate can help you identify the onset of another attack before it becomes serious.