Heart Conditions in PWDs other then JDCM

The PWDCA Heart committee is currently keeping track of the following defects and as more cases are reported we will be able to get researchers interested in studying these problems in our breed.

Patent Ductus Arteriosus (PDA)

PDA is the most common congenital heart defect in dogs. This defect occurs when normal fetal communication between the nonfunctional lungs and the aorta fails to close after birth. This results in a patent (open) duct with blood being shunted into the pulmonary artery and overperfusing the lungs. At the same time, the rest of the body is not getting adequate circulation. It is inherited as a polygenic trait with a high rate of heritability in some breeds. The degree of patency (openness) can vary from a large patent ductus to a very small opening.

Pulmonic Stenosis (PS)

PS was definitively identified in our breed in 2002, thanks to some very astute breeders obtaining autopsies on stillborn puppies. Unfortunately, more than 50% of some litters were lost due to the condition. Pulmonic stenosis is a defect of the heart valve that leads from the right ventricle to the lungs. The narrowing that occurs prevents adequate blood flow from the heart into the lungs, so that sufficient oxygen is not picked up and carried to the rest of the body. Mild, moderate and severe forms exist. We do not know the numbers of dogs with this defect in our breed but severe stenosis, which has been identified in our puppies, is incompatible with life. If a dog has mild or moderate stenosis, it will have a heart murmur and should be picked up on physical exam. All heart murmurs do not indicate pulmonic stenosis but dogs with heart murmurs should have an echocardiogram (ultrasound of the heart) done to identify their particular problem. Pedigree study on PS is critical and now underway as the mode of inheritance is complicated and not certain.

Ventricular Septal Defect (VSD)

A ventricular septal defect is a hole (or defect) in the muscular wall of the heart (the septum) that separates the right and left ventricles. Before birth, abnormalities can arise at several steps in the developmental process, resulting in abnormal blood flow in the heart with varying effects depending on the size and location of the defect. Often the first indication of a problem is when a veterinarian hears a heart murmur on a puppy's physical examination. Some low-grade murmurs are "innocent" and disappear by 6 months of age, but if the murmur is significant, your veterinarian will suggest a diagnostic workup to determine the cause. Signs associated with this disorder may develop within months or years, depending on the significance of the defect, and include shortness of breath, exercise intolerance, and even sudden death due to an abnormal heart rhythm. Among puppies with large VSDs, it is probable that many die early, before 8 weeks of age or before they are examined by a veterinarian. Treatments include medications to reduce pulmonary congestion, a special diet, exercise restriction, and precautionary antibiotic therapy before procedures such as dentistry. There are two current surgical options available - pulmonary artery banding to reduce the overload on the lungs and actual repair of the defect, but this requires open heart surgery and carries a very high risk.

Tetralogy of Fallot

Tetralogy of Fallot is a relatively uncommon but serious combination of defects that are the result of abnormal development in the embryo during the formation of the heart and great blood vessels. As the name implies, Tetralogy of Fallot consists of 4 defects. These are pulmonic stenosis, ventricular septal defect, overriding aorta and right ventricular hypertrophy secondary to the pulmonic stenosis. It is possible that pulmonic stenosis or a ventricular septal defect, both of which occur independently, may be less severe manifestations of this same genetic defect. Normally, the blood that is pumped to the body from the left side of the heart is fully saturated with oxygen. The result of the defects that make up the Tetralogy of Fallot is that poorly oxygenated blood is delivered to the body. As with other heart defects, the degree to which your dog is affected depends on the severity of the defect. If your dog has Tetralogy of Fallot with a very mild degree of pulmonic stenosis and a small ventricular septal defect, then he or she may only have a heart murmur and no associated clinical problems. More often though, puppies with this combination of defects experience weakness, failure to thrive and grow, a reduced tolerance for exercise, and general cyanosis (blue-grey instead of pink mucous membranes). Unfortunately, these dogs rarely live beyond 1 or 2 years without treatment. Complex open heart surgery is required to correct the condition but it has a high mortality rate.

Sub Aortic Stenosis (SAS)

SAS is an inherited disease, however, the exact mode of inheritance is complex and still has not been proven. It is characterized by an obstruction (stenosis) or "lesion" near the aortic valve involving the narrowing of the out-flow tract from the left ventricle leading to the aorta. (This is similar to a hose with a "crick" in it.) When there is a "crick" or obstruction in the tract, the heart must pump harder to get blood through the smaller opening. As the SAS-affected dog matures, his/her heart develops more muscle to push harder, which leads to an irregular heart beat, a lack of blood to the heart, congestive heart failure, or sudden death. The subaortic lesion progresses with maturity, and heart murmurs can be detected as early as six to eight weeks of age, or develop as late as three to four years of age in the milder cases. The obstruction can be valvular, supravalvular, or subvalvular (below the valve itself), the subvalvular variety being the most prevalent, hence "Sub Aortic Stenosis" or SAS. Diagnosis of SAS in its mildest, or sub-clinical, form, is extremely difficult. A dog affected with the mildest form of SAS will lead a full life of normal duration and quality, and will most likely be completely asymptomatic. Even those with moderate SAS can lead normal lives. However, dogs that are severely affected are at risk of sudden death.

Heart Murmurs are the sounds caused by alterations in blood flow through the heart or its large blood vessels. There are varying classifications: Benign - seen in young puppies and considered "innocent" as they disappear over time; Functional - associated with extra-cardiac factors such a; fever, pregnancy, chronic anemias, and hyperthyroidism; Pathological: result of a congential or acquired structural defect in the heart or large blood vessels leading from the heart. The intensity of a heart murmur is graded on a scale of 1 to 5 - a Grade 1 being barely audible and a Grade 5, the most severe, capable of being heard with a stethoscope held away from the chest. All dogs with heart murmurs, no matter what age, should have a diagnostic cardiac work-up, including an echocardiogram.

Congenital Lethal Edema

Sometimes referred to as "Anasarca", this is a condition which results in puppies that are swollen four to five times their normal birth size and weight. This massive collection of subcutaneous fluid often makes these puppies to large to be delivered naturally. Some are born alive, they seldom live more then several hours. They have been nicknamed "walrus" or "water" puppies. The cause and mode of inheritance is currently not known.

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