Cor Triatriatum in Dogs

The first sign you may notice in your dog is a huge belly caused by the fluid retention from the lack of heart function. This usually shows up in young dogs before the age of six months old and is sometimes ignored because it resembles other common issues of puppies such as eating too much. However, this symptom should never be ignored because it can be a sign of many illnesses including bloat, heartworm, or intestinal parasites.

Soon after, you will notice your dog is tired a lot, not eating as much, and may have diarrhea. If not treated, other complications may include pulmonary hypertension, pulmonic stenosis, ventricular defect, and eventually heart failure. It is important to take your dog to see a veterinary professional right away if you believe he has cor triatriatum.

Cor triatriatum is a congenital heart malformation that is caused by a membrane separating the left (sinister) or right (dexter) atrium into two chambers. While cor triatriatum sinister is rare, the abnormality in the right atrium is more common. Cor triatriatum dexter is the result of the right pulmonary vein not regressing as it should, causing the heart to have three atria instead of two. This creates a backup of pressure resulting in a slowed heart rate, fainting, fluid buildup in the abdomen, and eventually heart failure leading to death.

Often, this disorder is accompanied by other problems such as valve anomalies, mitral regurgitation, pulmonic stenosis, and heart failure. It is most common in Chow Chows and other large breed dogs such as Boxers, Rottweilers, Greyhounds, Golden Retrievers, Shorthaired Pointers, German Shepherds, German Shorthaired Pointers, English Bulldogs, and Cocker Spaniels.

Symptoms caused by cor triatriatum vary greatly due to the complications that can accompany the disorder. The most commonly reported signs of this condition include:

• Decreased appetite
• Slow heart rate
• Heavy breathing
• Pale gums
• Cough
• Enlarged liver
• Exercise intolerance
• Fainting
• Heavy breathing
• Distended veins in the abdomen
• Diarrhea
• Slowed growth
• Swollen abdomen
• Right-sided congestive heart failure

Types

• Cor triatriatum sinister is a rare defect of the heart that involves the left atrium
• Cor triatriatum dexter is a more common birth defect of the heart involving the right atrium

This birth defect can occur in any breed of dog, but is most common in large breed male dogs under a year old. Some of the most often reported breeds include:

• Rottweilers
• Greyhounds
• Golden Retrievers
• German Short-haired Pointers
• German Shepherds
• English Bulldogs
• Cocker Spaniels
• Chow Chows
• Boxers

A physical examination with palpation and auscultation should reveal abnormally distended abdominal veins with little or no pulse, enlarged abdomen due to fluid backup, and probably an enlarged liver as well. On auscultation of the heart, a murmur and slowed heart rate should be evident. The veterinarian will also need your dog’s medical history and immunizations. Also, be sure to let the veterinarian know if you have given your dog any kind of medication or vitamin supplements. If there is a large amount of abdominal fluid present, the veterinarian will most likely do an abdominal paracentesis to remove the fluid, saving some for laboratory analysis. This is done by inserting a fine needle into the abdomen to get a small amount of fluid. This fluid is tested in the laboratory and will probably show a high concentration of protein if your dog has cor triatriatum. In addition, routine blood tests, urinalysis, and fecal examination will be performed, but all of these will likely be normal.

Radiographs (x-rays) will likely show vena cava distention and a displaced diaphragm. An electrocardiogram (ECG) is usually normal or only slightly abnormal so the need for more tests is evident at this point. The veterinarian will perform an echocardiogram (ECHO), which should show the presence of the extra atrium caused by the membrane. Cardiac catheterization should reveal the increased pressure that is caused by the cor triatriatum which is considered to be a definitive diagnosis.

There are medications that the veterinarian will probably try before suggesting surgery. However, in most cases, surgery is usually needed eventually.

Medications

The most common drug for cor triatriatum is furosemide, which is for heart failure and has a diuretic that helps relieve fluid and congestion. Because this drug can have some unwelcome side effects, benazepril is usually given as well to balance the ACE activity. This drug therapy has shown promise in dogs with heart failure and increases energy and survival time. Other drugs that may be considered are pimobendan and atenolol.

Surgery

Operational techniques that can help include balloon catheterization and removal of the membrane causing the cor triatriatum. Both of these procedures have been very successful and have minimal complications.

Your dog will likely be in the hospital for at least 24 hours after surgery for observation and to provide any supplemental treatment if needed. Once you get him home, cage rest and plenty of attention are essential and you should call your veterinarian if you have any questions or concerns.